Why doesn't the plane accelerate/move forward when it's at rest, if the propeller is spinning?

When you start the engine in the c172, the blades on the prop are
  spinning - but the plane doesn't move at all.

When the propellor is idling its obviously moving air, this you can see, feel, and hear, however its simply not spinning fast enough to provide enough thrust to overcome the force of the plane sitting on the ground. Basically this is comprised of friction air resistance as well as some limited brake pressure that is usually applied. With fresh bearings, on level ground an idling prop may very well pull a plane forward. For the record it is a matter of certification that the brakes on an aircraft can hold it in place at full throttle. It also takes a bit more force to get a plane rolling than it does to keep it rolling. You need to break static friction to get rolling but then only provide enough power to overcome kinetic friction.

Generally speaking static friction is higher than kinetic friction,

(source)

  When taxiing out, it feels like the forward motion is being provided
  by the wheels - like in a car.

The first time you are in small plane you associate it with a car. You
equate that feeling with a car and thus you think intuitively that the tires are pushing you. In a car you could not be able to tell the difference between a front wheel drive and real wheel drive setup the idea is the same here.

  When taking off, you can audibly hear the change with the throttle
  increases.

I don't think there is a question here.

  In cruise, the plane almost looks the same from the inside
  as when it's on the ground (i.e. prop spinning). Which is where the
  weird psychological block is for me - the plane feels stationary even
  though the horizon/backdrop is moving towards you, and i get that fear
  kick in that it could drop because there's not enough momentum.

The plane feels stationary because you are in unaccelerated straight and level flight. In other words the forces are balanced about the aircraft. You feel nothing because there is nothing to feel ("feeling" is really another word for acceleration). This is different than a car, our road system lends its self to speeding up/slowing down often and unless you are on a very straight highway at night when its empty its less likely you are in unaccelerated movement in a car. The twits and turns of the road and the constant passing and slowing down of cars leads to a "feeling" of movement.


Can an Iranian citizen attain ATP in the United States?

The U.S. does not prohibit Iranian citizens entering the United States and remaining here on extended business. It also allows noncitizens to attend flight school, conditional on a review of the candidate by the Transportation Security Administration. So, the U.S. would not categorically prohibit an Iran citizen learning to fly and obtaining a commercial or airline pilot's license.

However, while not impossible, it will be much harder than I just made it sound if you are living in Iran right now, because communications between Iranians and the U.S. State Department have been made difficult by the politics of the past 35 years.

There is, to put it delicately, no functional United States Embassy on Iranian soil. The U.S. maintains a virtual Iranian Embassy online at http://iran.usembassy.gov/ (also in Farsi at http://persian.iran.usembassy.gov/); however it was blocked by Iranian information authorities less than 12 hours after it initially opened and remains blacklisted to this day. Users with a VPN tunnel outside Iran's firewall can access it, but the site is mostly educational; you cannot apply for a visa using the site alone. You'd have to be able to submit your paperwork to a functioning U.S. Embassy or directly to the State Department offices in Washington D.C., which will be a delicate process as the Revolutionary Guard will be monitoring both sides of such correspondence.

Assuming you can establish reliable contact with the U.S. State Department either directly or through an Embassy, you would need an extended visa. There are three basic reasons to stay longer than 90 days, with visa classes for each; work, school, and temporary asylum. If you are coming to the U.S. specifically to learn to fly, an M-1 visa should be what you apply for; it permits entry to the U.S. for "vocational or other non-academic training", including FAA Part 61 and Part 141 flight schools. The Iranian authorities also look most favorably on student visas compared to other types.

In addition to the visa, you would, like any other foreign applicant for flight training, be required to pass a TSA security clearance. This is ultimately discretionary; you cannot force the TSA to grant your clearance (ask any U.S. national; you can't force the TSA to do anything).

While neither the State Department, TSA nor the FAA would categorically prevent you learning to fly based on country of origin, the TSA does list Iran as a country of origin that prohibits the visa holder from "Automatic Revalidation". Essentially, if while attending flight school, you ever left the U.S. (to visit family back home, or even driving north to Canada or south to Mexico for sightseeing) you would be required to go through the full security clearance process again including the TSA check. So, you would have to stay in the United States political borders at all times while in flight school, or you could risk being denied reentry or resumption of your flight training.

While taking flight training and amassing your 1000 hours flight time required for an Airline Transport Pilot license (that 1000 hours number is good only if you're attending a four-year flight school; for most civilians working their way up it's 1,500), there are a number of illegal acts you can unintentionally commit while flying. For citizens, the legal penalty for unintentionally breaking an FAA regulation ranges from nothing to a talking to by air traffic control up to formal hearings with possible suspension or revocation of your pilot certificate. For a non-citizen in the United States for the express purpose of learning to fly, any offense bad enough to get your pilot's license suspended would likely also get you deported (if not for the criminal act, then because you can no longer do what you're here to do). But, you'd usually have to mess up pretty bad several times to get that far.

Once you have your ATPL, your M-1 would no longer be valid as you'd no longer be a student, and so you'd have to leave the U.S. unless you made prior arrangements with the State Department and/or an airline to remain in the country under another status (such as H-1b to work for an airline). If you take your license and leave the country, the FAA ATPL would only allow you to fly "N-numbered" aircraft registered by the FAA. Most other countries have their own registration, and would require you to "convert" your pilot's license to the local regulatory agency's version before you could fly a locally-registered plane. For an ATPL holder this is typically easier than for lower levels, and for the EASA (the largest ICAO-compliant regulatory body besides the FAA) it boils down to a skills test (knowledge and practical), a new medical cert, and being re-rated by the EASA for multi-engine operations (the FAA AMEL class rating does not transfer).


How does this vortex form inside a jet engine?

Whenever there is under-pressure in air, the air flows along the gradient of this under-pressure, i.e. into the direction of the source of the under-pressure. (In first order.)

If there's a wall (or the ground) in the way, air will flow along the surface of this obstacle and will change its direction at some point, as shown in this sketch:

Now, imagine the whole air around the engine is rotating slowly for some reason around the symmetry axis in the sketch.

From physics, you may know the conservation of momentum, or in this case, of angular momentum. It says that the product of distance to rotation axis times RPM of this rotation is constant for a certain particle. If a particle reduces its distance to the axis, its RPM increases.
This is like the spinning ice skater, who rotates faster when he pulls his arms to his body (to the axis).

This law also applies to packets of air, which are sucked to the axis, though internal friction brakes the air to some extent.

The fast rotating air near the axis encounters a centrifugal force, i.e. the air is pulled away from the axis, forming a region of strong under-pressure. In this region, the air expands and so, cools down. This can cause condensation of water, if the humidity of the air is high enough. And that's what you can see on your pictures.

There's still one question unanswered: I wrote, this happens if the surrounding air is rotating slowly. This usually happens, because the wind is deflected from the aircraft itself, which means it changes its direction, which is some kind of rotation.

And of course, a strong, non-uniform air flow from the rear, as generated by the reverse thrusters, can cause more / stronger rotating air, which results into stronger vertices. So, it's no wonder when they appear (or better: become more visible) in this case.

Here is a nice picture of a simulation, which also shows that the fuselage can be the wall where the vortex is created.

Source: http://gallery.ensight.com

It seems the wind comes from the camera position, or a bit more right of it. It gets deflected by the fuselage and flows along it, which explains the straight lines coming from the rear and the curved ones coming from the front left of the aircraft. If you imagine the air flow along / under the fuselage, you may also understand why the two vertices are rotating in different orientations.

As the strong under-pressure inside the vortex, it may also suck in dust or even larger objects, which can damage the engine. For aircraft landing on unpaved airfields, unpaved strip kits may be available, which can contain a vortex dissipator:

Source: http://www.b737.org.uk

This is a nozzle blowing bleed air into the region where vortices could apper, reducing the under-pressure and so the risk of ingesting objects from the ground.

Notes:

You can see something similar in the sink of your bathtub. As soon as there is a little rotation, it is amplified above the sink, the centrifugal force pushes the water aside, and forms this fast rotating vortex.

A tornado is a giant version of an inlet vortex. The air is moving along ground over far distances, until it moves upwards at some point, and a slight rotation leads to this fast rotating hose sticking to the ground and sucking in everything due to the strong under-pressure inside.

And a bit off-topic:

Sometimes, you can see vortices at the wing tips or at the edges of engaged flaps of aircraft flying through humid air. The reason is similar: The air is put into rotation due to the higher pressure below and the lower above the wings. (But that's not exactly the same as inlet vortices.) And sometimes, you also see fog forming above the wing just because of the under-pressure.
On this picture, you see both, and may imagine the rotation for the second vortex from the right.

Source: http://avioners.net


What is the effect of flying height on helicopter fuel consumption?

The lift equation shows that as air density decreases, as it does with altitude, in order to maintain lift, the speed of the blades must increase or, the coefficient of lift (CL) must increase.  Since the characteristics of the blades do not change, in order to increase the CL, the angle of attack must be increased.

Increasing either of these increases drag so, in order to prevent the blades from slowing down, the engine must produce more power to counteract the drag.

Most helicopters use constant speed rotors so in practice, the angle of attack (the pitch of the blades) is the only variable.  In order to maintain speed of the blades, the pilot, or a throttle governor, must increase power from the engine.

Therefore, a helicopter uses more fuel as it's altitude increases.


What are the rules for driving at a public, uncontrolled airport in the USA?

The FAA has issued an FAA Guide to
Ground Vehicle
Operations -
A Comprehensive Guide
to Safe Driving on the
Airport Surface which covers what they call "non-towered airports"

  NON-TOWERED AIRPORTS
  When the control tower is closed or if there is no tower, the airport
  is referred to as non-towered. At a non-towered airport, you do not
  need controller permission before entering a runway or taxiway.
  Below are some best practices for operating on a non-towered
  airport:

  When you approach the runways and taxiways, STOP, LOOK
  both ways, and LISTEN for aircraft that are landing or taking
  off. Vehicle windows should be open to do this properly.
  Alert others when you are using a taxiway or runway by
  always making an announcement on the radio before you
  enter. Be specific with your location and intentions.
  Always yield the right-of-way to taxiing aircraft and give them
  plenty of room. If an aircraft is headed toward you on the
  same taxiway, move out of the aircraft’s way.
  Always carry a radio tuned to the airport’s Common Traffic
  Advisory Frequency (CTAF) or UNICOM.
  If an aircraft is about to land on a runway that you need to
  cross, stop well clear of the runway. Continue to yield to the
  aircraft until it has landed and taxied off of the runway.
  Be aware that some
  aircraft at non-towered
  airports are not equipped
  with radios.
  Before you cross a runway, ensure that no potentially
  conflicting aircraft are taxiing, landing or taking off. Be
  aware of aircraft at non-towered airports that frequently make
  touch-and-go landings (immediately after landing, full power
  is applied and the aircraft takes off again).
  If your vehicle has a rotating beacon, be sure to turn it on
  anytime you are on the airport surface. Turn on headlights as
  well, being careful not to blind any pilots in the area.


Can a laser Doppler anemometer be used to measure airspeed?

In place of pitot-static system

No, because it measures different physical quantity.

Laser Doppler anemometer measures velocity of the stream¹. But pitot-static system does not. Pitot-static system measures dynamic pressure and expresses it as airspeed at which that dynamic pressure would occur at sea level on an ISO standard day².

Since lift and control effectiveness depend on dynamic pressure, that is exactly the quantity the pilot needs to see. Laser Doppler anemometer does not provide it, therefore it cannot replace pitot-static system.

In addition to pitot-static system

Anything can be used in addition to what we have. But the question is whether there is a reason to.

For flying the aircraft, true airspeed is not needed and for determining the wind speed by comparing true airspeed and ground speed the airspeed can be estimated well enough from indicated airspeed, pressure and temperature.

However a laser anemometer has the advantage of being able to measure the wind speed ahead of the aircraft. This could be used for load alleviation (the system needs to know about the gusts a bit in advance so it can move the control surfaces in advance) and it could perhaps be used for detecting wind shear, though I am not sure how feasible such anemometer measuring wind speed hundreds of metres ahead is.

¹ A.k.a. true airspeed.

² That quantity is called equivalent airspeed. That is intended quantity, but the measurement is subject to various errors. The raw output of the pitot tube is called indicated airspeed and the value corrected for positional errors (due to the air-stream impacting the pitot tube at an angle) is called calibrated airspeed.


How much lift is lost by wing dihedral, and can it be fixed?

The amount of lift lost to dihedral is because of a trigonometrical condition, and cannot be fixed by ribs.

Lift is always perpendicular to the local surface, and each wing half develops lift at the dihedral angle. Only the vertical bit is useful for suspending the aeroplane weight.

In order to quantify:

Cos 5° = 0.9962, so less than 0.4% of lift is not useful.
Cos 10° = 0.9848, meaning a 1.5 % loss.

Wing sweep has the same roll/sideslip stabilising effect as dihedral does (this answer), so less or no dihedral is required if the wing is swept. But there are many other considerations related to lift and drag with a swept wing.


Low hour Pilot wants to move up to Piper Malibu Mirage but having trouble finding insurance

You won't be able to get around the time-in-type requirement for insurance. That's pretty much a set-in-stone requirement, especially for a high performance aircraft like the Mirage. I suggest that while you build the hours you fly with someone who meets the requirements for insurance.


Would a refueling stop be cheaper than finding lodging for all the passengers?

I don't know what aircraft you flew on over 3 years ago. The current options from Etihad are Boeing 777 and Airbus A380. The route doesn't seem to be nonstop anymore, aboard any airline.

Along the shortest distance -- great circle route -- there aren't many options for an A380 to land and find support equipment mid-route (shown below). Refueling can occur with the passengers on board, there is a procedure to be followed, which includes alerting the fire service at the airport to be ready.

If we take only the cost of fuel into account, and a 777-200 as a baseline, actually stopping every ~6 hours is more economical. (This doesn't take into account landing fees, accrued cycles*, passenger convenience, etc.) Not just for your flight, but any long-haul flight; the fuel burned to carry the fuel for long distances becomes considerable after a certain range.

Another consideration is which freedoms of the air, say Etihad/UAE, has with say Russia. The second freedom specifically is:

  The right to refuel or carry out maintenance in a foreign country without embarking or disembarking passengers or cargo.

While they are called freedoms, not all country-pairs mutually allow all the freedoms. The specifics are usually not public and are contained in the air service agreement between any 2 nations.

In all, it might have saved fuel even if we included a detour off the great circle. It certainly would have increased the maintenance cost. And it would have been an operational nightmare to arrange compared to a hotel and meal.

* Pressurizing and depressurizing twice, applying the takeoff thrust twice, applying the brakes twice, etc., all increase the maintenance cost.

Re: comment about London or Sweden already being destinations:

Already having flights to Sweden, UK, or Italy, doesn't mean the 2nd freedom is guaranteed. Note that "not many options" $\neq$ none. The middle half of the flight is either over tundra or the Arctic Ocean. An airport like London Heathrow won't welcome an on the spot request for a slot; busy airports in Europe are running near max capacity, so unless it's an emergency, on the spot slots really aren't realizable. Three daily slots to land at London Heathrow (as a destination) already cost Etihad £46.2 million back in 2013.

(gcmap.com)


What is the difference between a turbofan and a turboprop engine?

Both engines use a turbine for power. This is where the "turbo" part of the name comes from. In a turbine engine, air is compressed and then fuel is ignited in this compressed air. The energy produced by the ignition turns the turbine. The turbine is then able to drive both the compressor at the front of the engine and also some useful load. In airplanes, it produces thrust.

The first jet engine was a turbojet. This is a simple turbine engine that produces all of its thrust from the exhaust from the turbine section. However, because all of the air is passing through the whole turbine, all of it must burn fuel. This means it is inefficient, and the solution is the turbofan.

In a turbofan, the turbine primarily drives a fan at the front of the engine. Most engines drive the fan directly from the turbine. There are usually at least two separate shafts to allow the fan to spin slower than the inner core of the engine. The fan is surrounded by a cowl which guides the air to and from the fan. Part of the air enters the turbine section of the engine, and the rest is bypassed around the engine. In high-bypass engines, most of the air only goes through the fan and bypasses the rest of the engine and providing most of the thrust.

In a turboprop, the turbine primarily drives a propeller at the front of the engine. There is no cowl around the prop. Some air enters the turbine, the rest does not. The propeller is geared to allow it to spin slower than the turbine. Although this diagram shows only a single shaft, many turboprops have two, with a high pressure shaft driving the compressor and a low pressure shaft driving the propeller. Some engines such as the popular PT6 also reverse the flow direction multiple times.

Turboprops are more efficient at lower speeds since the prop can move much more air with a smaller turbine than the fan on a turbofan engine. The cowl around the turbofan's large fan allows it to perform better than an open propeller at high speeds, but limits the practical size of the fan.

At supersonic speeds, turbojets have more of a performance benefit. They develop all of their thrust from the high velocity turbine exhaust, while turbofans supplement that with the lower velocity air from the fan. Since the air from the fan is also not compressed nearly as much as the core turbine flow, it is also harder to prevent the flow from going supersonic and causing losses.

The Concorde used turbojets because it was designed to cruise for long periods at supersonic speeds. Modern fighter jet engines are turbofans, which provide a compromise between efficiency and speed.

There are other benefits and drawbacks between turbojets, turbofans, and turboprops, but I think they are beyond the scope of this question.

Work has been done on creating a "propfan" engine, in an attempt to get the efficiency of a turboprop and the speed of a turbofan. They have yet to come up with a viable design.

Elsewhere in aviation, turbine engines are used in

helicopters, as a turboshaft engine driving the rotors instead of a propeller, and with a freewheeling clutch to enable autorotations
APUs in jet aircraft and large turboprop aircraft

Turbines also find use outside of aviation in power plants (to generate electricity), and even vehicles (like the Abrams tank).

Turbocharged piston engines use a turbine much differently from the examples above. Instead of being the primary power source, the turbine only assists the piston engine. A turbocharger uses a turbine to compress air sent to the engine intake. The increased compression helps the engine generate more power. The turbine of a turbocharger is driven by engine exhaust gasses, and a supercharger is similar but is directly powered by the engine. See the Wikipedia page for more detail.


Why is the numerically determined location of the center of pressure inaccurate near Cl = 0?

If some parts of the airfoil create lift and others a downforce, the center of pressure can be outside of the airfoil's chord at low lift coefficients. This condition is fulfilled for cambered airfoils, airfoils with a deflected flap and especially for rear loading airfoils, which have low camber in the front and high camber in the rear part. Supercritical airfoils meet this last condition.

In airfoil theory, an airfoil creates lift and a moment, because the lift is assumed to attack at the quarter chord point. This point is special because here the moment coefficient does not change with the angle of attack (at least in the inviscid, linear potential theory, which is sufficiently close to reality at large Reynolds numbers to be useful). In reality, positive camber will cause the resulting lift force to act aft of the quarter chord point, and the pitching moment is negative. When lift becomes small and the pitching moment stays constant, the lever arm of that small lift needs to become large to achieve the same moment, and this is when the center of pressure can slip out of the airfoil's chord.

Below you see the result from XFRL5 V6.0.5. I plotted the local center of pressure as a green line. It's elevation over the plane of the wing shows the amount of lift locally created, and the location in streamwise direction shows that it leaves the local chord when lift becomes low. Note that when moving out in spanwise direction the location jumps from far aft of the airfoil to far ahead when the local lift turns negative. At the point of no local lift you have a division by zero error, patched over here by a straight connection between the results from the single panels.

Location of the local center of pressure on a swept wing (own work).

When angle of attack is increased, all additional lift has the Birnbaum distribution, so the local center of pressure moves towards the quarter-chord location.


Where is the compression on a compression strut in a tube and fabric airplane coming from?

You want a nice, taut fabric cover on this wing, don't you?

The main function of the compression struts is to keep both spar tubes from being pulled closer by the fabric cover. Of course, Niels is right, aerodynamic forces come on top of this and will also pull on the tubes in the wing's plane.

In order to calculate those forces, integrate the tension in the fabric over wingspan when loaded by maximum lift forces. Below I have sketched those lift forces – they want to pull the fabric up, increasing tension within it and so the compression forces on the struts.

I hope I got the basic structure about right. Please correct me where needed.


Is this "wing-wave" early after takeoff really a pilot tradition?

Is this really a pilot tradition and do they do this on passenger flights and most importantly, was this safe?

It wasn't a passenger flight, as the description reads, it was a delivery flight*. Furthermore the plane is a freighter, designed to carry cargo--the kind without feet.

Being a delivery flight, it's typically flown with a very experienced crew, and yes it is a tradition, and it's perfectly safe in that particular scenario (light plane, plenty of performance, no passengers). The crew will also typically let the tower know what they'll be doing, so the tower controllers won't be alarmed.

  The 'wing-wave', a gentle dip of the plane from one side to another, is generally done by cargo planes to say 'goodbye' as the aircraft will never again see the home airport where it was made.

https://www.dailymail.co.uk/travel/travel_news/article-2783901/Captain-dramatically-dips-wings-just-seconds-highly-skilled-stunt.html

* Not to be confused with the maiden flight and the subsequent test flights by both the manufacturer and the customer.

Related question about the same video: Is there any reason spoilers would deploy just after liftoff?


Does the US export the Mark 77 aerial bomb?

I cannot find any info on the export status of the  Mark 77 with a routine search, and plenty of reports of media attention to its use, which leads me to believe there is not a huge market for it among US allies due to the potential for negative press.

For your second question, the Russian equivalent are the ZAB-xxx series of bombs, where the acronym stands for incendiary airdropped bomb (Zazhigahtel'naya Aviabomba) and the number is the warhead weight in kilograms. It seems the most used version at the moment is the ZAB-500. Variations include the OZAB and OFZAB, where the O is for fragmentation (Oskolochnaya) and the F for high-explosive (Fugasnaya). I have not been able to find a link with info on the  OZAB version.

Similar munitions sometimes come with an RBK (Razovaya Bombovaya Kasseta) prefix, meaning cluster dispenser, for example RBK-500-ZAB, which is a standardized RBK-500 cluster dispenser with over 100 ZAB-2.5 incendiary sub-munitions, for an approximate 500kg of combined warhead mass.


What's the shape and place of the tip vortex in a propeller, depending on propeller sense of turning?

I too am unsure exactly what your question is but propeller blades shed vortices at the tips just like wings and rotor blades. This vortices and their paths can be seen when the weather conditions are right as in this photograph. (I don't own this image)

You can find many more of these types of images with a quick google search. The vortices roughly follow the advance ratio of the propeller at the moment they form. There would be little difference to the formation of vortices for push or pull configuration.


Why does power help us maintain altitude in slow flight?

It is not correct to say that power controls altitude. In slow flight, it is taught that power controls altitude and pitch controls speed. Yes, it works, but you have to always keep in mind that a power change will always require a pitch change and a pitch change will require a power change, if you want to maintain the same trimmed speed, altitude and angle of attack.
As you might very well know, in a slow flight, you reduce your power first and start putting down the flaps to sort of keep the aircraft in an approach configuration. Then you pull back on the stick until you are close to the stall speed. Once the speed you want is reached, you add power as required to maintain speed and altitude. If you lose altitude, a little addition of power will arrest it. But trust me, this will also increase the speed by small margin. This might not be registered in the air speed indicator of a smaller aircraft. Similarly, an increase in pitch in attempt to reduce an increasing speed, will change the altitude. So, it is not fixed. Pitch and power are not two separate entities. They always work together. Try flying a high performance aircraft with powerful engines and with a load of inertia and you will see how true my words are.
The reason why more and more power is necessary to successfully accomplish a slow flight is because you are operating below the L/D speed of the aircraft. Once you are below this speed, the increase in induced drag (due to high angle of attack) increases the total drag on the air frame. To overcome this drag you are required to add power or energy. We call this operating behind the power curve or the region of reverse command. Reverse because normally, you need an increase in power to fly at a higher speed. But behind the curve, to fly at a lower speed, you need more and more power.
Look at the graph below, the GD (Green dot) speed is the L/D speed. As you can see, as you go below the L/D there is a steep increase in drag.


Is the 737NG hydraulically controlled or electronically controlled?

Of course it's hydraulic.

Electric actuators or power-by-wire is actually a far more exotic technology than fly-by-wire, and the latter is a hard prerequisite for the former.

Normal fly-by-wire is still based on hydraulic systems, with the electrical FBW system controlling the valves. And even in power-by-wire systems, the final actuator is typically a small enclosed hydraulic unit.

The newer 737 MAX has a couple FBW elements (spoilers), but is still a manual system, well short of FBW or PBW.


What are the most efficient layouts of multiple runways?

In order to increase the number of operations that can be handled at a runway, you want them configured so as to allow "simultaneous independent approaches," which means that the 2 (or more) runways can be operational without the need to coordinate between them.

The biggest factor is the distance between the two runways. The greater the distance between them, the less impact they have on each other, not just in terms of number of operations per hour, but also in terms of visibility minima for instrument approaches.

The other factor that needs to be considered is the wind, and as you can see from the Chicago airport layout, there are parallel groups of runways that effectively form a triangle, such that there is never a crosswind component that exceeds 30 degrees. The layout at Las Cruces, NM, which is usually very windy, shows the format better than Chicago, even though they are single runways:

The last issue is the type of radar available, and the faster the radar sweep, the less delay there is between the position of the aircraft and their depiction on the radar screen, allowing the controllers to closely monitor the approaches.


What are the registration requirements for US aircraft?

Where can the requirements for US aircraft registration be found?

The registration procedure is outlined in FAA Form AFS-750-94, Information to Aid in the Registration of U.S. Civil Aircraft. See also the full list of FAA registration forms.

  3. The owner of an aircraft must apply to the Aircraft Registration Branch, P.O. Box 25504, Oklahoma City, Oklahoma 73125-0504, to obtain a certificate of registration. The applicant must submit an Aircraft Registration Application, AC Form 8050-1, accompanied by evidence of ownership and a $5 registration fee.

  Requirements for registration of aircraft are contained in the Federal Aviation Regulations, Part 47, “Aircraft Registration.” (For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402.)

Basically, the registrant (whether an individual or a corporation, trustee, etc., all of which are defined in Part 47) must be able to prove legal ownership of the airplane.

  What is the penalty for flying an aircraft without a valid registration?

The violator would be subject to any of the standard FAA enforcement actions: administrative action (a "Warning Notice" or "Letter of Correction" which goes on your record), reexamination ("709 ride"), certification action (suspension or revocation), or civil/criminal penalties. The exact penalty would likely depend on the circumstances: whether the violation was intentional and the degree of the pilot's negligence under the FARs.

  What should someone do if they believe an aircraft to be operating without valid registration, and how could they determine this?

The FAA's website recommends reporting FAR violations by calling the FAA's toll-free telephone number, 1-866-TELL-FAA.


What is this high wing, single engine aircraft?

Indeed a Douglas aircraft, namely the O-43, an improved version of the O-31 (longer wing and a new engine) which was Douglas's first straight-wing monoplane.

The O-43 was in turn developed into the O-46


Are there any situations where having high lift but low lift to drag ratio would be beneficial?

Landing phase would benefit from high lift but low lift-to-drag ratio. At most phase of flight you need about the same amount of lift to keep the plane in the air. However during landing you need to slow down to landing speed. Hence you lower lift-to-drag ratio by keep the same amount of lift but increase amount of drag. This is usually accomplish by selection of large amount of flaps.


What are the symptoms of vortex ring state?

Vortex ring state is characterized by rapid descent and reduced effectiveness of control inputs. At the onset, it is characterized by increased vibration and buffet of the airframe, with uncommanded changes in helicopter attitude. Also, any increase in the collective is ineffective and counterproductive.

From skybrary.aero:

  Incipient vortex ring conditions are typically:

  increased vibration and buffet,
  the onset of small amplitude ‘twitches’ in pitch and evidence of longitudinal, lateral and directional instability.

  Established vortex ring conditions are characterised by:

  a very rapid increase in rate of descent towards and beyond 3000fpm,
  reduced effectiveness of cyclic inputs in roll or pitch
  the application of collective pitch failing to arrest the rate of descent and usually increasing it.

From FAA Helicopter Flying Handbook- Helicopter Emergencies and Hazards:

  A fully developed vortex ring state is characterized by an unstable condition in which the helicopter experiences uncommanded pitch and roll oscillations, has little or no collective authority, and achieves a descent rate that may approach 6,000 feet per minute (fpm) if allowed to develop.

The best measure against vortex ring state is quite simple- go forward i.e. increase airspeed. Basically, you enter into forward flight so that the rate of descent doesn't oppose the induced flow. You need 'undisturbed' airflow over the rotor disc. Power is to be applied after gaining sufficient airspeed. From skybrary:

  Incipient Stage ... Keep the collective position unchanged and apply forward cyclic to achieve an accelerative (nose down) attitude so as to increase forward airspeed quickly. As soon as a steady increase in airspeed is indicated, and above 30 KIAS, more power can be applied if necessary without waiting until the best rate of climb speed is reached.

  If this action does not resolve the situation rapidly then it is best to treat the condition as established and take the actions below.
  Established Condition. Recovery can only be effected by changing the airflow around the rotor and will inevitably lead to significant loss of height, which makes recovery from a low level occurrence impossible.

  There are two theoretically possible actions: Moving the cyclic forward and lowering the collective. Combining these actions is likely to produce the quickest recovery with the least height loss.

  Application of forward cyclic should increase airspeed but a large input held for several seconds may be required before significant pitch attitude and consequent speed change is achieved, with a significant nose down attitude resulting. Lowering the collective to reduce power towards auto-rotation, so unstalling some of the inboard portion of the blades, may also be effective but forward airspeed must be gained before power is re-applied during recovery.

Autorotation has also been suggested as a measure for overcoming the vortex ring state (by the FAA handbook, for example), but it may lead to further loss of height, which has to be taken into account. Another issue is that there are some variations between the different helicopter types- in case of tilt-rotor aircraft like V-22, the only way is to go into forward flight.


Is the phraseology in the early portion of the movie The Net realistic?

"Radar contact lost" is standard phraseology.  Most typically it's used when an aircraft far from the radar antenna is no longer being picked up, and it's just an advisory that "we can talk to you but we can't still see you."  (Remote VHF antennas are cheaper & easier to put up in remote places than radar transmitters.)

As for the scenario itself, initial contact with the tower is hardly the point where ATC would first notice that the aircraft wasn't going where it should be.  To get TO the ILS course, you'd typically have Approach Control issuing radar vectors to the aircraft, ending up with "N1234X, 3 miles from Van Nuys, fly heading 100 until established, cleared ILS runway 8 at Burbank."  If the aircraft flies through the course (for whatever reason; it sounds like in the movie the implication is that his navigation equipment has been hacked), they'd issue another vector, cancel his approach clearance & tell him to climb, or whatever.

Also, ATC (i.e. Approach Control, even more so than Tower) will get automated low altitude alerts when an aircraft is below set altitudes.  If an aircraft in radar contact was descending into terrain (and not on final to a runway), well before the radar loses line-of-sight with the aircraft, the controller would issue something along the lines of "N1234X, low altitude alert, check altimeter 30.05, climb and maintain 2000'."

There are non-radar environments where pilot mistakes have put perfectly flyable aircraft into the terrain without any opportunity for ATC intervention.  There have been cases within radar coverage where misread instruments, usually only when combined with an additional pilot error, have put aircraft into terrain or obstacles short of the landing runway.  The smokestacks referenced sounds like a prominent feature well north of Burbank, so at a minimum there's some "artistic license" involved in claiming that a hacked ILS could put the aircraft that far off course in that direction without ATC catching it well in advance of things getting to the point of a crash.

Also, an ILS receiver would be awfully hard to hack, no matter what sort of evil programming genius you are.  You could disable it in several different ways (pair of wire cutters would do that), but the malfunction would be obvious to the pilot early on.  To have the receiver seem perfectly normal but in fact guiding the pilot down too soon would really require broadcasting false signals to the aircraft in real time in a way that an ILS ground station probably can't do -- at least not without triggering a warning in the monitoring equipment that ends up shutting it down.  And even then, when the pilot gets to 200' above the runway elevation, if HE doesn't see the runway lights, he should be going around.

All in all, this scenario has its weaknesses.  The idea that a hacker could create enough problems to bring down a plane is actually more credible now than in 1995, but even so, the most likely problems are a lot less dramatic than what's described -- "hey, where'd all my electronic charts go?"  Aviation has a LOT of safeguards to prevent exactly this sort of scenario from playing out, even with state-sponsored bad guys as the potential threat.

But, it made for a fun movie, so suspension of disbelief and all, right?


Why does this Garmin GMA340 have an Airway/Inner marker indicator?

The "A" is not an inner marker. The A is an airway marker. Airway markers were part of a now-obsolete system of "red" airways. They were placed along the enroute path and they could be picked up at cruise altitudes. The red airway system was mostly abandoned in the 60's and few "A" markers are still operational. Here's a map showing where they were located. They weren't at aerodromes.

Source

The airway markers transmit the same 3000 Hz audio frequency as inner markers so the airway marker can be used to pick up the inner marker. Since you say that unit is not certified for cat II it makes sense that they labeled it "A" instead of "I" although it can be used for inner markers.


Why/how is a downplane parachute configuration aerodynamically stable?

It appears that each parachute will tend to adopt a position where a line drawn from the skydiver through the center of pressure of the chute is aft of a line drawn through the skydiver perpendicular to the relative wind, by an angle equal to the L/D ratio of the parachute.  The higher the L/D ratio of the parachute, the closer to "straight overhead" the chute can be, in the reference frame of the falling skydiver with his body positioned horizontally as per the photo.  Much as the higher the L/D ratio of a kite on a string, the closer its steady-state position can approach a position straight "overhead" the kite flyer.  But a stable downplane should be possible even with chutes with a rather poor L/D ratio-- the chutes just wouldn't be positioned nearly opposite each other as is the case in the photo.  This would be analogous to a kite with a poor L/D ratio flying in a position that is far from "overhead" the kite flyer.  The speed of such a downplane would tend to be lower than the downplane illustrated in the photo.


How does the flap configuration affect the tailstrike limit on the A320 aircraft family?

A higher configuration number indicates that the flaps/slats are extended by an higher amount.

In turns this means that for the same angle of attack the wings will produce higher lift (and drag) in the higher configuration.

You achieve take-off when the lift is at least equal to the weight of the aircraft, and with higher flap/slat deflection you will have sufficient lift even when the nose is relatively low on the horizon, leaving plenty of margin against a tailstrike.

On the other hand, if you are using a low configuration, the flaps/slats will be mostly retracted, and you will need a higher AoA to produce sufficient lift, meaning that you have to raise the nose of the aircraft more, leaving less margin against a tailstrike.


What happens if a parachute does not open while skydiving?

The majority of the heat developed during reentry of a space-vehicle comes from air compression not friction. Remember, to go into space, you don't have to go very high, but to orbit you will have to go very very fast, and it's not the fall that produces the heat, it's the slowing down part.

If you had a human fall without a chute, the terminal velocity (where air resistance cancels gravity and you continue downward at a constant speed) would be around 100-200 mph, not nearly enough to cause any kind of heat (or cars would burn up by going normal cruising speeds). To get higher terminal velocities, you'd have to go a lot higher, where the air is a lot less dense, higher than any skydiver have, and as far as I can tell Felix Baumgartner did not experience any incineration during his jump.

The unfortunate skydiver will almost certainly die, but there'd definitely be a body, and it'll probably be in one piece.


Puerto Vallarta (MMPR) has a VOR/DME on the field (PVR), which is used in seven different approaches (that I can find) depending on where you're coming from and which runway you're landing on:

VOR DME 1 Rwy 04 (Teardrop)
VOR DME 2 Rwy 04 (DME arc from NW)
VOR DME 3 Rwy 04 (DME arc from SE)
VOR DME 1 Rwy 22 (Teardrop)
VOR DME 2 Rwy 22 (DME arc from NW)
VOR DME 3 Rwy 22 (DME arc from SE)
VOR Rwy 04 (Procedure Turn)

Your abnormal flight seems to exactly match the VOR DME 2 Rwy 22 coming from BLASK on airway V1/J141. So yes, that was the intended flight path.

What's interesting is that your normal flights don't match any of the procedures. I suspect that ATC is vectoring those planes to final, which saves the time, fuel and effort of flying a DME arc, teardrop or procedure turn.

If ATC can do that, though, why did that one flight do the DME arc as charted? It's possible ATC was too busy to vector at that time, or their radar was down, or there was a radio problem, or the pilot requested the full procedure to maintain proficiency, or something else. Without a recording of the ATC frequency, it's hard to say.


How do high-wing and low-wing aircraft compare in terms of structural damage in a crash?

Regardless of wing position, a crash will damage most or all of the aircraft structure. Since low wings have dihedral, mild cases like a wheels-up landing will mainly affect the center fuselage rsp. the wing box. But most crashes occur in an odd orientation of the aircraft towards the ground, so at least one wing and the fuselage will suffer damage.

There are a few designs which will tolerate foreseeable abuse. On the Su-27, two long iron bars run along the lower fuselage and are the first to contact the ground in absence of wheels. After such a landing, the aircraft is simply jacked up and put into service again.

Su-27 on the ground after belly landing (picture source). Just look at the paint job – the abuse this aircraft suffered is not restricted to this unorthodox landing style.

The main gear of the A-10 only partially retracts, so the bottoms of the wheels stick out of the gear bays and will contact the ground first. A belly landing with an A-10 will require a bit of repair but normally the aircraft is back in the air within a week.

A-10 on the ground after belly landing (picture source). The landing gear design is on purpose: It limits damage in a belly landing. Few aircraft have been designed with such foresight.

Similarly, for tail strike testing a bumper structure is added at the lower rear fuselage. In absence of such precautions, lengthy workshop stays are unavoidable.

But most crashes are less benign. The main factor in a crash is the relative velocity between the aircraft and the structure it crashes against. In most cases, this is a sizeable portion of flight speed, so the energies involved are immense (mass times velocity squared, divided by two).

Boeing 737 Crash site (picture source). As can be seen, both wings and fuselage are heavily damaged. The wing location was not a factor in the extent of the damage. That is how a real crash looks like. Unfortunately.


Does a high-pitching-moment symetrical airfoil exist?

What you probably look for is a symmetrical tail airfoil which produces high control moments. Since those moments are the product of force and lever arm, placing those control surfaces far from the center of gravity produces high moments.

A symmetrical airfoil will have zero pitching moment around its quarter chord point in attached flow. This is understood as zero pitching moment, since the pitching moment of an isolated surface is per convention defined around its quarter chord point. For a thorough explanation please consult this answer.

If, however, you choose a different reference point for your moment, even the symmetrical airfoil can produce a pitching moment. That effect is used in tail surfaces and for a given geometry, a higher maximum lift coefficient will produce a higher maximum moment. Traditionally, the NACA four-digit range of airfoils starting with a double-zero have been used for tail surfaces, but more modern designs will produce a higher maximum lift and lower minimum drag. A good choice would be the Wortmann FX 71 range of airfoils, like the FX 71-120 or the FX 71-L-150 which can often be found on gliders.


Does the transponder need to be on in the upper limit of Class B airspace?

Yes:
If you combine the two sections provided by SMSvonder Tann and Raaj Tram you get:

  14 CFR 91.215 - ATC transponder and altitude reporting equipment and use:

    (b)(4) All aircraft in all airspace above the ceiling and within the lateral boundaries of a Class B or Class C airspace area designated for an airport upward to 10,000 feet MSL; and

    (b)(5)(I) airspace of the 48 contiguous states and the District of Columbia at and above 10,000 feet MSL, excluding the airspace at and below 2,500 feet above the surface; and

You can't fly over B or C without a transponder.

There are some specific exceptions for aircraft not originally equipped with an electrical system.


Which en-route services are available to UK GA pilots?

According to UK AIP ENR 1.1 "General Rules", chapter 2 "UK Flight Information Services" the UK FIRs meet the ICAO requirements with the following Flight Information Services (FIS): Basic Service, Traffic Service, Deconfliction Service and Procedural Service.

This is an extract of the contents of the chapter:

  Basic Service
  Provides advice and information useful for the safe and efficient conduct of flights. This may include weather
  information, changes of serviceability of facilities, conditions at aerodromes, general airspace activity information, and any other
  information likely to affect safety. The avoidance of other traffic is solely the pilot's responsibility.

  Basic Service is available under IFR outside controlled airspace in any meteorological conditions, or under VFR. A pilot may change
  heading, route, or level without advising the controller. A controller will not issue specific heading instructions; however, generic
  navigational assistance may be provided on request.

  Traffic Service
  Traffic Service is a surveillance based ATS, where in addition to the provisions of a Basic Service, the controller provides specific
  surveillance derived traffic information to assist the pilot in avoiding other traffic. The avoidance of other traffic is solely the pilot's
  responsibility.
  Traffic Service is available under IFR outside controlled airspace in any meteorological conditions, or under VFR.

  Deconfliction Service
  A Deconfliction Service is a surveillance based ATS where, in addition to the provisions of a Basic Service, the controller provides
  specific surveillance derived traffic information and deconfliction advice.
  A Deconfliction Service shall only be provided to flights under IFR in Class G Airspace, irrespective of meteorological conditions.[...] A controller will provide traffic information, accompanied with a heading and/or level aimed at achieving a planned deconfliction minima.

  Procedural Service
  A Procedural Service is a non surveillance ATS where, in addition to the provisions of a Basic Service, the controller provides
  instructions, which if complied with, shall achieve deconfliction minima against other aircraft participating in the Procedural
  Service. Neither traffic information nor deconfliction advice can be passed with respect to unknown traffic. A Procedural Service shall only be provided to flights under IFR, irrespective of meteorological conditions. [...] the pilot remains wholly responsible for terrain clearance at all times. [...] A controller will provide deconfliction instructions by allocating levels, radials, tracks, routes, time restrictions, approach clearances and holding instructions, or use pilot position reports, aimed at achieving a planned deconfliction minima.


FAR 91.169 states that IFR flight plans must include an alternate airport unless the weather is at least 2000 ft ceiling and 3 miles visibility, from one hour before to one hour afterwards (1-2-3 rule).

The same regulation also states that the alternate airport must meet the following critera:

  (c) IFR alternate airport weather minima. Unless otherwise authorized
  by the Administrator, no person may include an alternate airport in an
  IFR flight plan unless appropriate weather reports or weather
  forecasts, or a combination of them, indicate that, at the estimated
  time of arrival at the alternate airport, the ceiling and visibility
  at that airport will be at or above the following weather minima:

    (1) If an instrument approach procedure has been published in part 97
    of this chapter, or a special instrument approach procedure has been
    issued by the Administrator to the operator, for that airport, the
    following minima:

      (i) For aircraft other than helicopters: The
      alternate airport minima specified in that procedure, or if none are
      specified the following standard approach minima:

      (A) For a precision approach procedure. Ceiling 600 feet and visibility 2 statute miles.

      (B) For a non-precision approach procedure. Ceiling 800 feet and visibility 2 statute miles.


Can you fly an airliner without an ATPL?

You don't have to be an ATP to fly an airliner. In fact, you can fly an airliner as a private pilot. John Travolta is the best example I can think of... He has a house right by a private airport and flies his own personal Boeing 707 (with Qantas livery) and another jet aircraft (Gulfstream I think). With any large aircraft like this over 12500 lbs or with turbojet engine(s), a pilot does need a type specific rating to fly such an aircraft as well as needing to be "current" in that type, but may do so as long as current at any certificate "level" of private pilot or above. However, to fly an airliner as a scheduled air carrier pilot, then yes, an ATP is required as this type of flight would not fall under part 91 or part 135 of the FARs, but instead part 121 which requires that all pilots have ATP certificates.


Do airliners have an "anti-pilot" warning system?

The system you're asking about is called radar: ATC should monitor it to see what the plane is doing and ask what is going on when something unexpected happens.

It's hard to "automate" these kinds of alerts. For example, a sudden dive can also be cause by an uncontrolled control-surface hard-over (like the boeing 737 rudder problems that brought down 2 planes), or a loss of cabin pressurization (which requires a rapid descent to an altitude where your passengers can breathe).

The other option is having a second person in the cockpit who can wrest control away from the disobedient pilot (or let people in the cockpit to help).


Can helicopters perform the Split S maneuver?

Yes, but you need a rigid head.

A rigid head does not have any hinges, instead, the blades flex up and down.

Wings don't know or care if they are upside down or right way up, indeed, most helicopter blades are symmetrical.  It only cares how much airflow there is and at what angle it hits it.

Here's an EC-120 performing a split S and a Lynx showing what's possible.

Perhaps the best around is Chuck Aaron, displaying for Red Bull.

Here, Dennis Kenyon shows about as good as it can get with a semi-rigid head.  He gets close to inverted but never actually flips over.


How to Tell Flight Following You Want to Change Your Destination?

Just tell them.  Like you told us in the question.  Seriously, plain old English works just fine on the radio.

Don't get all chatty, and be professional, but don't overthink things and feel you need to use a bunch of radiotelephony code words to get a simple point across.

The most important thing is to clearly communicate intentions.  Don't tell them you are going one place and then "change" it when you actually planned on going there all along.  That's phony and unnecessary, and could confuse things if there any sort of emergency where knowing your planned route of flight or destination would be useful.

Simply tell them you plan to fly VFR up the coast to VanNuys, then turn Eastward and proceed to destination XYZ.  Or, more briefly:  "destination XYZ, via Van Nuys".  It's just that simple.

And consider filing a flight plan.


How can I see all commercial destinations to a country from a particular airport?

There can be a number of websites which can provide this information. Wikipedia and the specific airline's website can be a great resource too.

OpenFlights gives you a graphical representation of direct flights from a particular airport. It appears that this service is for all major airports across the globe.
SkyScanner can provide the information you are looking for. As for your example, you'll enter Las Vegas in the From text area, and then leave the To area blank. It will search all destinations (grouped by countries) where there are direct flights (or with one stop) available.


What are the relative contributions of the body and wings to missile lift?

What is the proportion of lift coming from the wings compared to that of the fuselage?

It can be almost zero.  The ASRAAM's only fins or wings or lifting surfaces or whatever you call 'ems are at its very tail.  Any "lift" they impart, that far from the missile's center of mass, would pitch (or yaw) the missile instead of counteracting gravity.  So almost all the lift must come from the body having a slight nose-up attitude.

Another missile with a similar planform is the (ground vehicle launched) LOSAT.


Does the ICAO definition of an "aircraft" include a minimum altitude capability?

Is there a lower altitude threshold in the ICAO definition of an aircraft?

No.

Is a wing in ground effect craft an aircraft according to ICAO definition?

No.

I believe the ICAO is based on the Chicago Convention

The 2006 9th edition begins

  THEREFORE, the undersigned governments having agreed on
  certain principles and arrangements in order that international
  civil aviation may be developed in a safe and orderly manner
  and that international air transport services may be established
  on  the basis of equality of opportunity and operated  soundly
  and economically

Although this has a section on definitions, it doesn't define aircraft.

The ICAO ADREP taxonomy contains this definition:

  Aircraft. Any machine that can derive support in the atmosphere from the reactions of the air
  other than the reactions of the air against the earth's surface. (Annex
  8)

That appears to exclude vehicles whose support relies on ground effect only.

Why [was] the 100 ft threshold [...] put into the German (or other) laws?

That might be better answered in law.se


How do I optimize a turbofan engine to fly lower and slower instead of higher and faster?

As a summary, the engine generates thrust by changing the impulse (momentum) of the air. Please refer to this: NASA Genera Thrust Equation

So to optimize aircraft performance, the main options you can play with are that depend on your aircraft operation:
V0: flight speed
p0, r0: inlet pressure and density (function of altitude)

And the variables that depend on your engine design:
Ve, pe, re: exhaust velocity pressure and density (depend on the thermal cycle and actual operating condition of the engine)
A0, Ae: Inlet and nozzle areas (engine geometry, sizes derived from the design point)

Now what you need to see is that there is no single best option, aircraft design is an optimization problem, eg finding compromises. Flying lower and slower is actually an attractive option for greener aircraft, as it enables technologies that reduce drag, such as ultra high aspect ratio wings, laminar airfoils, boundary layer ingestion, electric propulsion and a few more.

Whether optimizing a turbofan for lower altitudes make sense can only be seen by comparing the wins against the losses, and it is hard to say absolute truths as it depends on many variables.

Now about the actual "how-to" optimize a gas turbine, essentially the key variable of the engine is the pressure ratio, PR, so how much it compresses the inlet air. For a given flight condition (thrust, speed and altitude) , there is an optimal pressure ratio. From that the number of compressor and turbine stages can be calculated (also if you need a multi-spool engine, do you use an intercooler, etc.), and also the geometrical dimensions of the engine. And this goes back to the comment I've made that it is a compromise. Building a very heavy, expensive, hard to maintain engine will not be a good choice as what you win by increased engine efficiency you will lose on the flight efficiency.

But suppose as an academic exercise you just want to alter an existing engine design to move its design point to a lower speed and altitude, then you need to change the design pressure ratio, and follow up with any internal changes (add/remove stages, change inlet, nozzle, etc.)


How is the wind direction and wind speed measured in flight?

Indirectly, as the difference between true air speed and ground speed.
Since aircraft cannot measure true air speed, several steps are needed to arrive at the correct wind speed:

The pitot tube (big aircraft have several of them) gives the stagnation pressure of the air, which is the sum of static and dynamic pressure.
The static ports (again, big aircraft have several of them) give the static pressure of the ambient air, so the dynamic pressure can be isolated.
With the static pressure and the ambient temperature the air density can be calculated.
With the density it is now possible to calculate the true air speed from the dynamic pressure.
From the compass you get the heading of the aircraft, so you know the direction of the true air speed.
The ground speed and track direction can be calculated by repeatedly measuring the location of the aircraft and dividing the distance by the time between measurements, or with modern aircraft it can be read directly from the GPS display.
Wind speed and direction can be calculated by subtracting the true air speed vector from the ground speed vector.

You will notice that there are a lot of possible sources of error in this procedure. All instruments involved have their own bias and scaling error. However, if everything is carefully calibrated and corrected, the result can be very accurate.


What is the incidence angle of a propeller in the terminology of the Wright Brothers and how did they obtain it?

According to various scholars, the Wright brothers were referring to "angle of attack" when they used the term "incidence." They actually published an article by the same title, so the fact is well-established.
References include the following:

In Wilbur's time, the "angle of incidence" was what we now call the "angle of attack" -- the angle at which the wing of an airplane meets the wind (wright-brothers.org).

and

In the Wright's own words: "The lift is thus balanced against the normal pressure on the resistance surfaces ... Therefore, the lift ... at the given angle of incidence (angle of attack) is to the pressure on a square plane of equal area at 90° as the sine of the (...)
(wright.edu)

The angle of attack of a propeller is defined in various ways, a summary of which is here.

The angle at which this air (relative wind) strikes the propeller blade is its angle of attack.


Why do different aircraft have different maximum operating temperatures?

There are a few different things going on here. For the best answer, see this blog post.

To summarize his points, there's a combination of factors:

The Bombardiers simply aren't certified at those temperatures.
Their combination of small wings and small jet engines makes high temperatures particularly problematic for them. With the air density decreasing as the temperature rises the wings get less lift and the engines suck in less oxygen. The bigger jets have larger wings and bigger engines which make up for their larger weight so they can fly while the regional jets can't.

So to answer your question ("Is this solely due to the size of the aircraft, or is it a difference of manufacturer?"): Yes


How are arriving aircraft assigned to runways?

Arrival and departure runways are mainly assigned due to airport flow. Each airport has its own set of plans of which runways to use, how to taxi to these runways etc. If everybody is moving in the same direction, things go smoother.

Pilots and airliners can request a specific runway, but the request may be denied unless the aircraft has an emergency. Generally the reason is to shorten taxi time, and ATC may grant the request if traffic volume is low. For example, in an airport with a parallel runway configuration, a cargo plane may request the one closer to the cargo terminal.

At some airports, a runway switch may be performed fairly late during the approach. For example, the visual approach to 13L/13R at JFK is largely the same - the only difference is timing the final turn*. Occasionally you will hear pilots requesting the other runway on ATC recordings on YouTube.

For specifics such as which runway goes to which airline, they are local to the airport in question and outside the scope of this answer.

*occasionally, the pilots got it wrong and line up for the wrong runway


Are helicopters impacted by fog more than airplanes?

No.  If anything, given a helicopter can fly a much slower cruise speed than an airplane typically does, they do not require the visibility minimums which fixed wing aircraft do.  VFR weather minimums for a helicopter in uncontrolled airspace are 1/2 mile versus 1 mile for airplanes.  Be that as it may, a helicopter is still vulnerable to Loss of Control Inflight (LOCI) due to pilot error just like any other aircraft.


What are the advantages and disadvantages of having landing gear doors?

Benefits of gear doors

With gear doors, there are fewer constraints on the retracted gear position. This is especially important in larger aircraft with larger and more complex landing gear. It doesn't need to be flush with fuselage or streamlined (737 also uses hubcaps).
The gear doors provide a good aerodynamic surface
Opening to gear bay can be larger and easier to access

Drawbacks of gear doors

Extra weight for the door and the mechanisms
Extra complexity of opening another door (possibility for things to go wrong)


The captain of an aircraft flying an international flight is required to have a Restricted Radiotelephone Operator Permit. How do you get one?

You have to use the remarkably obtuse FCC Universal Licensing System if you want to request a license online. You'll specifically need FCC Form 605, the apparently very-accurately-named "Quick-Form Application for Authorization in the Ship, Aircraft, Amateur, Restricted and Commercial Operator, and General Mobile Radio Services".

From there, you're on your own, I'm afraid. I applied for mine years ago and it looked identical.

Do note that this is essentially a fee on operators who fly internationally, as there's no exam to complete and no proof of eligibility to provide. You simply request the license and pay the application costs. It's a bit silly.


How do ADS-B and ADS-C get used on transoceanic flights?

1) ADS-B will stop working when the transponder is switched off at the gate after arrival in Tokyo. Airliners use the 1090 MHz Extended Squitter variety of ADS-B which is the worldwide standard.

2) I don't have hard numbers but I guess it is approximately 90 percent of the flights. At most economical cruise flight levels, ADS-C is mandatory.

3) ADS-C is a common system. For aircraft not equipped, position reporting of HF is the alternative. And soon space based ADS-B will be available as well.


How are ADS-B surface position frames decoded?

The Compact Position Report (CPR) coding in Surface squiters is different from Airborne CPR coding. The resolution is 4 times better (~1.25 m instead of ~ 5 m), at the cost of losing the 2 most significant bits.

Due to this, global surface position decoding gives an ambiguous solution. IIRC the solution can be at 4 points on the globe, you have to select the nearest to you. And you should validate that it is within a realistic range, like you should do with Airborne CPR decoding. After you validated the position using global decoding on a couple of odd- even squiter pairs you can use the more efficient local decoding. Of course, as with Airborne CPR decoding, you need to protect against position jumps and time gaps in your decoding algorithm.


Have there been any solo flights on airliners?

In normal operations there are regulations against this sort of thing (as Dave has said).  But there have been a few emergencies where the First Office or the Captain have become incapacitated (due to medical emergencies), and the remaining pilot has declined to ask if there is another pilot on board to help fly the plane.

Here is an example from 2011 of a Ryanair flight having this occur**, I have heard of others but can't find references.  So, admittedly, that may be the only actual occurrence.

So, to finally answer your questions:  Very rarely, in an emergency situation, there can be a single pilot on a commercial airliner.  Granted, there were passengers on board, so I'm not sure it fits your narrow definition of "solo", but it's about as close as it's going to get.

For completeness (though I don't think it counts), there have been a few instances of a single pilot stealing a commercial jetliner.

For example this 727.  There were actually two people involved, one was a mechanic, the other had a private pilots license (hence the pilot was "soloing").  The aircraft has not been seen since...so it's assumed it ended badly, and, for the record, it's also assumed the pilot was coerced (if indeed he was even flying the plane).

There are a couple more incidents, namely this Antonov-26, which was stolen by a mechanic, circled for an hour, then crashed.  And also this ATR-42-320, which was actually stolen by a Captain form Air Botswana.  He circled the airport for a couple of hours demanding to speak to everyone from his girlfriend, to his boss to the President of Botswana.  They were actually arranging to have him speak with the president when he crashed his plane into two other Air Botswana ATR-42-320s that were parked on the ground.  He was the only one killed.

Again, though, I'm not sure if these fit the criteria you are looking for.  But in that last one, at very least, he was the only person on board the aircraft, it was a commercial aircraft and he was in fact a Captain.

But to say all this an irregularity would be an extreme understatement...

** For clarification:  The reason I state this is the only example I could find is because it's the only one where I could find a report where it was specifically stated the remaining pilot had no help.  To quote from the report:

  Once the initial Cabin Crew assistance was complete, the Captain indicated that he did not need assistance in operating the aircraft, although this was suggested in the operator’s procedures for pilot incapacitation. The First Officer took no further part in the operation of the aircraft. No inquiries as to the possible presence on board the aircraft of either medically trained personnel or qualified pilots were made.

All other examples I saw either specifically stated that a new co-pilot was found, or they skipped that detail entirely.

All of that being said, I somehow doubt this is the only case, it's just the only one I could explicitly verify.


What are the circles/holes ahead of the wing of an MD-82?

The three large circles indicated in the question are static port plates. These measure the static pressure of the surrounding air, which is used to measure airspeed and altitude.

Original Source

Thanks to a link from Jonathan Walters, here is a closeup of one:

The four smaller areas in a row along the centerline are the radar altimeter transmitters/receivers. The radar altimeter uses radio waves to determine the aircraft's altitude above the ground. This diagram for the A345 has them further aft, they're in similar configurations on other aircraft.

Original Source


How much electrical power does one generator produce on a large turbofan?

This is one of the four Variable Frequency Generator (VFG) of the Airbus A380. It's apparent power is 150 kVA.

Rotor, source: Safran

The total power available from the engines is 600 kVA.

Seen from the other side:

Stator, source: Thales

The A380 is a one of these "more electrical" planes, where hydraulics tends to be replaced by electric devices, and the electric circuits have been optimized by electronics and variable frequency. There are secondary sources for electricity: APU (auxiliary power unit) and RAT (ram air turbine). Overall view from the book Civil Avionics Systems (Moir, Seabridge, Jukes):

Source: Civil Avionics Systems

In case of total failure, the ultimate RAT backup is totally electric-based contrary to conventional aircraft where some hydraulics is also provided by the RAT to move the control surfaces.


Should I add balloons in my Ultralight wing to help it float if I land in the water?

Not practical to put balloons in the wings.  They would expand at altitude, messing up the wing profile.  How would you control that?

The best option, possible if the fabric is reasonably impermeable, is to seal all possible ingress points in the wing, leaving a small vent hole at a point least likely to be submersed, like the wing root trailing edge.  This will at least delay the sinking.   You could use ripstop repair tape used for fixing tents.

That'll slow down the sinking process, giving you lots of time to get out.  Then wear one of those compact inflatable vests that boaters use that drape around your neck that you inflate when needed, for swimming to shore.

Even better, with all the weight you would add with various other solutions, might as well get a set of Puddle Jumper amphibious floats.  Might as well make it possible to land on water anyway.  Problem solved.


Does the flight crew in big airliners hear the cabin crew PAs?

Yes, when the pilot makes the selection to speak on the PA, he will hear if anyone else is using the PA. They would just wait until the other party is finished, or they can take priority and speak over them.


What are the different wing planforms? What are each's advantages? Where are they commonly used?

The wing planform (which is the shape and layout of wing) for each aircraft is mainly based on the aerodynamic requirements. There are other considerations like stealth, controllability etc. The basic terminology in the wing geometry is given in the figure below.

Source: grc.nasa.gov

Most of the wing platforms in use (or have been used) fall under one of these categories.

Elliptical Aerodynamically, the elliptical planform is the most efficient as elliptical spanwise lift distribution has the lowest possible induced drag (as given by thin airfoil theory). However, the most important disadvantage of the elliptical wing is that its manufacturability is poor.

Perhaps the most famous aircraft with elliptical planform is the Supermarine Spitfire, used in Battle of Britan.

"Spitfire mark19 ps853 planform arp" by Adrian Pingstone (Arpingstone) - Own work. Licensed under Public Domain via Commons.

Interestingly, the elliptical wing was not decided to minimize induced drag, but to house the retractable landing gear along with guns and ammunition inside a wing that had to be thin. As per designer Beverly Shenstone,

  The ellipse was simply the shape that allowed us the thinnest possible wing with room inside to carry the necessary structure and the things we wanted to cram in. And it looked nice.

Some aircraft like the Seversky P-35 had a semi elliptical wing, with only the leading or trailing edge elliptical.

"Seversky SEV-DS" by Unknown - http://www.flickr.com/photos/sdasmarchives/8392339249/in/set-72157631292290354. Licensed under CC0 via Commons.

Rectangular Arguably the simplest wing planform from a manufacturing point of view, the rectangular wing is a straight, untapered wing. A good example would be the light general aircraft like Piper PA 38.

"Piper pa-38-112 g-bppf arp". Licensed under Public Domain via Commons.

The main disadvantage of this wing is that it is aerodynamically inefficient.

Tapered Wing This is a modification of the rectangular wing where the chord is varied across the span to approximate the elliptical lift distribution. While not as efficient as the elliptical lift distribution, it offers a compromise between manufacturability and efficiency.

A very good example of aircraft using this type of wing is the North American P-51 Mustang, which became the premier USAAF escort fighter against the Luftwaffe.

"P51-d mustang 472216 arp". Licensed under Public Domain via Commons.

Constant Chord with Tapered Outer This is midway between the rectangular and the tapered wing, with the inner part having constant chord and the outer part having a taper.

A very good example of this type of wing is the English Electric Canberra.

Source:

Almost all of the wings seen so far are used in subsonic aircraft due to the large drag caused by them in the transonic regime. Most of the wings used in supersonic aircraft fall under one of the following categories.

Delta The delta is a very low aspect ratio wing used in supersonic aircraft, most notably in the European designs. The main advantages of the delta wing is that is efficient in all the flight regimes (subsonic, transonic and supersonic). Also, the wing offers a large wing area for the shape, reducing wing loading and improving maneuverability.

The delta wing design is also very strong structurally, offering large volume for internal fuel. The delta wings are also quite simple to build and maintain.

The main disadvantages are that they have high induced drag due to low aspect ratio and also that they should have high angle of attack at low speeds (takeoff and landing), mainly due to fact that at these speeds, lift is generated by vortices. To compensate for this, they have high stall angles.

A very good example for this wing is the Dassault Mirage 2000, which is an example of tailless delta i.e. without horizontal stabilizers.

Source: www.aircraftrecognition.co.uk

A variant of the delta wing used in some aircraft is the one with horizontal stabilizer (tailed delta), the most famous of them being the Russian Mikoyan-Gurevich MiG-21.

Source: hdwallpapers.cat

Another variant is the one used by the Eurofighter Typhoon, the so called cropped delta, where the tips of the delta are 'cut off' to reduce drag at high angles of attack.

"Eurofighter 9803 2" by Kogo - Own work. Licensed under GFDL via Commons.

Yet another variant of the delta wing (this planform is very popular in combat aircraft), is the so called double delta, where the leading edge angle is not constant, but has two different values. One good example of this is the Light Combat Aircraft 'Tejas' under development in India.

"LCA Tejas" by Rinju9 - Own work. Licensed under CC BY-SA 3.0 via Commons.

Trapezoidal The trapezoidal wing is a high performance configuration such that the leading edge sweeps back and the trailing edge sweeps forward. This is mostly found in combat aircraft from the US.

This wing configuration offers efficient supersonic flight and has very good stealth characteristics. However, the wing loading is quite high, resulting in reduced maneuverability, especially instantaneous turn rate.

This wing configuration is used most notably in the Lockheed Martin F-22 Raptor.

"F 22 raptor bomb bay display 2014 Reno Air Races photo D Ramey Logan" by WPPilot - Own work. Licensed under CC BY-SA 4.0 via Commons.

Ogive The Ogive is a type of supersonic wing used in high speed aircraft. This is a complex mathematical shape derived for minimizing drag, especially at supersonic speeds. They offer excellent supersonic performance, with minimal drag. However, they are extremely complex and manufacturing is difficult while their subsonic performance is poor in comparison.

The most important aircraft using this wing is the Aérospatiale-BAC Concorde, one of the two supersonic commercial aircraft.

Source: www.wired.com

The wing planforms can also be classified on their sweep and variability.

Swept Back wings The leading edges of these wings are swept back. This is done order to reduce drag in transonic speeds, which is determined by the velocity normal to the wing.

This planform is used in almost all high speed commercial airliners. A good example would be the Boeing 787 Dreamliner.

"Boeing 787-8 Dreamliner N787FT KBFI" by redlegsfan21 - Flickr: N787FT. Licensed under CC BY-SA 2.0 via Commons.

Swept Forward Wings One disadvantage of the swept back wings is that due to the flow characteristics, the ailerons stall before the flaps (i.e. outboard wings stall first), which can lead to controllability issues. In order to overcome this, swept forward wings were used  in a few (experimental) aircraft.

The man problem with swept forward wing is that it produces wing twisting as it bends under load, resulting in greater stress on the wing root than for a similar straight or swept back wing. One of the few aircraft to use this wing is the Sukoi Su-47 Berkut.

Source: tom-clancys-hawx.wikia.com

Variable Sweep Wings For high speeds (transonic and supersonic), the swept wing is most suitable while for low speed (subsonic) flight, unswept wings are better. Varaible sweep wings were used to optimize the wing planform over a wide range of speeds. The main problem with this type of wing is the mechanical complexity.

The first aircraft to enter service with the variable sweep wing was the General Dynamics F-111 Aardvak.

"F-111A Wing Sweep Sequence" by Unknown. - http://www.nationalmuseum.af.mil/factsheets/factsheet_media.asp?fsID=2321&page=3. Licensed under Public Domain via Wikipedia.

Though most of the aircraft have used these planform, a number of other wing shapes have also been tried.

For example, the Handley Page Victor used a Crescent shaped wing.

Source:

F-16 XL used a cranked-arrow double delta wing.

Source: www.nasa.gov

One point to note is that most of the aircraft in operation or development use wing planforms which are a combination of the above rather than any one of them.


When to use beacon, anti-collision, strobe, logo, and navigation lights?

The Aeronautical Information Manual (AIM) is a great place to look for questions like this, and has this on the subject:

  4-3-23. Use of Aircraft Lights

  a. Aircraft position lights are required to be lighted on aircraft
  operated on the surface and in flight from sunset to sunrise. In
  addition, aircraft equipped with an anti-collision light system are
  required to operate that light system during all types of operations
  (day and night). However, during any adverse meteorological
  conditions, the pilot-in-command may determine that the anti-collision
  lights should be turned off when their light output would constitute a
  hazard to safety (14 CFR Section 91.209). Supplementary strobe lights
  should be turned off on the ground when they adversely affect ground
  personnel or other pilots, and in flight when there are adverse
  reflection from clouds.

  b. An aircraft anti-collision light system can use one or more
  rotating beacons and/or strobe lights, be colored either red or white,
  and have different (higher than minimum) intensities when compared to
  other aircraft. Many aircraft have both a rotating beacon and a strobe
  light system.

  c. The FAA has a voluntary pilot safety program, Operation Lights On,
  to enhance the see-and-avoid concept. Pilots are encouraged to turn on
  their landing lights during takeoff; i.e., either after takeoff
  clearance has been received or when beginning takeoff roll. Pilots are
  further encouraged to turn on their landing lights when operating
  below 10,000 feet, day or night, especially when operating within 10
  miles of any airport, or in conditions of reduced visibility and in
  areas where flocks of birds may be expected, i.e., coastal areas, lake
  areas, around refuse dumps, etc. Although turning on aircraft lights
  does enhance the see-and-avoid concept, pilots should not become
  complacent about keeping a sharp lookout for other aircraft. Not all
  aircraft are equipped with lights and some pilots may not have their
  lights turned on. Aircraft manufacturer's recommendations for
  operation of landing lights and electrical systems should be observed.

  d. Prop and jet blast forces generated by large aircraft have
  overturned or damaged several smaller aircraft taxiing behind them. To
  avoid similar results, and in the interest of preventing upsets and
  injuries to ground personnel from such forces, the FAA recommends that
  air carriers and commercial operators turn on their rotating beacons
  anytime their aircraft engines are in operation. General aviation
  pilots using rotating beacon equipped aircraft are also encouraged to
  participate in this program which is designed to alert others to the
  potential hazard. Since this is a voluntary program, exercise caution
  and do not rely solely on the rotating beacon as an indication that
  aircraft engines are in operation.

  e. Prior to commencing taxi, it is recommended to turn on navigation,
  position, anticollision, and logo lights (if equipped). To signal
  intent to other pilots, consider turning on the taxi light when the
  aircraft is moving or intending to move on the ground, and turning it
  off when stopped or yielding to other ground traffic. Strobe lights
  should not be illuminated during taxi if they will adversely affect
  the vision of other pilots or ground personnel.

  f. At the discretion of the pilotincommand, all exterior lights
  should be illuminated when taxiing on or across any runway. This
  increases the conspicuousness of the aircraft to controllers and other
  pilots approaching to land, taxiing, or crossing the runway. Pilots
  should comply with any equipment operating limitations and consider
  the effects of landing and strobe lights on other aircraft in their
  vicinity.

  g. When entering the departure runway for takeoff or to “line up and
  wait,” all lights, except for landing lights, should be illuminated to
  make the aircraft conspicuous to ATC and other aircraft on approach.
  Landing lights should be turned on when takeoff clearance is received
  or when commencing takeoff roll at an airport without an operating
  control tower.


Is it possible that derated thrust takeoffs are safer than normal takeoffs?

The reasons presented at ground school for the benefits of de-rated thrust takeoffs were twofold:

less chance of catastrophic engine failure during takeoff
less overall wear between overhauls

It is from this standpoint that reduced thrust takeoffs are safer.

As you point out, these are only authorized when the weights, temperature and runway length allow, but for the EMB-145 virtually every takeoff we did was eligible for reduced thrust.

You point about ease of control with an engine out is countered by engine out procedures which involve setting max thrust on the remaining engine (for two-engine ops).  During takeoff roll in the EMB-145XR, this puts the other engine at 117% power.  With the exception of flying near $V_{MC}$ (for light twins) the extra thrust is a benefit and not a hindrance to control and if this is at or after $V_1$ you'll want the thrust to go flying.

Your question about a bird strike is going to go one of two ways:

the bird hits the N1 fan and goes through the bypass ducting
the bird hits the N1 fan and is ingested into the N2 compressor stages

In either scenario a reduced thrust vs full thrust takeoff is not going to make a huge difference, but scenario 2 will be far more destructive to the engine than scenario 1.


What were the make and model of the engine that failed in flight Southwest 1380?

According to this article published on news.com.au:

Engine model is CFM56-7B, debuted in 1997.
Manufacturer is CFM International, jointly owned by General Electric of the United States and Safran Aircraft Engines, a division of Safran of France.

More specifically, AirFleets.net reports:

Engine model: CFM56-7B24
Plane: Boeing 737 Next Gen, variant group 737-700


Is the taxi route omitted in low visibility (LVP)?

It has nothing to do with LVP, but with the fact that there are standard routes at Schiphol to the main piers;

From the AIP AD 2.1 (EHAM) section 2.1:

  Aircraft shall comply with the standard taxi routings to and from the stands as depicted on AD 2.EHAM-GMC. Deviations from the standard taxi routings will be given timely to the pilot by Schiphol Ground.

The AD 2.EHAM-GMC (Ground Movement Chart) shows the following in the legend:

Late at night, when there is almost no traffic, there is no need to hold aircraft or deviate from the standard route.

The crew is Dutch, they are at their home based, so they are well aware of the routing. So ATC only gives their stand, knowing they will find their way.

There's a double taxiway almost fully around the central terminal area. The outer ring is counterclockwise, the inner ring is for clockwise traffic. The exit for RWY 06 leads straight onto the counter clockwise taxiway. From there you can follow that until A10, which leads you to the D5 gate. There is basically no other way.


In the US, do ultralight aircraft have tail numbers?

Assuming that you mean an ultralight as defined in part 103, there is no requirement to be registered or have a tail number. 14 CFR 103.7(c) says:

  Notwithstanding any other section pertaining to registration and marking of aircraft, ultralight vehicles are not required to be registered or to bear markings of any type


Why are airplanes riveted and not screwed?

Rivets need to press the two parts together AND to transmit shear. The pressure results in friction which is responsible for a considerable part of the load transmitted between two riveted panels. In order to hold up to the maximum possible amount of shear, the rivet needs a smooth surface. A thread would make it much more vulnerable due to the notch effect of the thread.
Since skin panels and flanges vary in thickness, a LOT of different screw sizes would need to be kept on stock so that every combination of panel thicknesses is covered with a fitting screw which has just the right amount of smooth shank length. Rivets, on the other hand, will be hammered to the right length during manufacture, so only a few sizes are needed to cover all those panel thicknesses.
Historically, metalworking tools were much less precise than today. For optimum shear transmission, the bolt must sit tightly in its hole. In the past, this could  not be done with screws, but only with rivets which grow thicker when set in place. And since aviation regulation authorities are VERY conservative, the easiest to certify joints are those proven rivet joints.
Repairability is adequate when using rivets, especially if you can reach only one side. The rivets are drilled out with a drill bit which has a diameter slightly smaller than the original hole size. Great care is taken not to oversize their original hole. The rivets are then, in the case of sufficiently thick material, tapped out with a hammer and punch. If the material is too thin or fragile to allow a punch and hammer to be used, the rivet will be drilled out with a drill bit that matches the original size of the rivet hole, with great care taken not to oversize the hole. If the hole is damaged or oversized in the removal process, a larger hole may be drilled and corresponding rivet installed, depending on the conditions present. After inspection or repair the parts are riveted together again.
If you need the lowest mass for a given strength, again rivets win over screws. The difference might be small for the individual rivet, but it adds up for the whole airframe.


How does the F-16 side stick convert pilot input to an electrical signal?

The stick measures force by using strain gauges. These work by measuring the change in electrical resistance caused by stretching or compressing the thin metallic foil, which is bonded onto the stick shaft.

An accurate setup requires two strain gauges at opposite sides, which are measured using a Wheatstone bridge: the difference in resistance of the two gauges is used for the force signal.

There are other ways of measuring input force, but none are more accurate than the strain gauge/ Wheatstone bridge setup which can measure force in both directions and has little to no hysteresis.


How can I improve the reception of my coaxial collinear antenna (1090 MHz)?

If the antenna is located in your living room, then the incoming 1090 MHz signals will be blocked by your house. 1090MHz signals are more-or-less line of sight. They don't travel very far through concrete or wood and are severely attenuated by glass, especially is you have energy efficient windows.

I suspect you have a window towards the East or South East so that you have some signal reception from that direction. Try to put the antenna outside, preferably on top of your house to improve your signal reception.


Is inverted flight possible under these conditions?

Yes, based purely on the wing shape an airliner could fly upside down and maintain a straight inverted flight. The lift of the wing is a function of the vertical angle of the airflow, the angle of attack.

Image source

The picture shows an airfoil pointed upwards, but the same forces apply when the wing nose point downwards. Then turn the picture upside down, and you have lift pointing upwards again.

The situation is valid for an asymmetric airfoil as well, the only difference being that it provides lift at AoA zero. Zero lift is provided at a slight negative angle of attack, so the aircraft nose will be further up when inverted, still below the stall angle though.


For the elliptical wing, which property is actually elliptically distributed?

It is both the planform and the circulation distribution. Note that circulation is not lift coefficient but bound vortex intensity. You can interpret it as local lift coefficient times local chord.

On the untwisted elliptical wing the local lift coefficient is constant over span, and changes in angle of attack over the linear range will change the lift coefficient equally everywhere. This, when combined with the elliptical chord distribution over span, means that the circulation distribution will stay elliptical over the linear angle of attack range. This is the special characteristic of an elliptical wing: While any wing can have an elliptical circulation distribution at one angle of attack (given the right twist distribution), the elliptical wing will keep that elliptical circulation distribution over the whole operating range.

With an elliptic circulation distribution comes also a constant induced angle of attack and downwash angle over span. I guess this is expressed by some authors with the term "regular".

However, only the aerodynamicists will see that as an advantage. Both weight and stall characteristics of elliptical wings are less than optimum; the low induced drag coefficient is bought with higher structural mass and, consequently, lift. A more triangular circulation distribution will yield the lowest wing weight and overall drag for a given non-lifting mass (that is, all mass that is not involved in lift generation, especially the payload). Note that for such a triangular distribution drag will be highest near the center.

When people talk about elliptical lift distribution, they mean lift per span. I prefer to use the more correct term circulation, since lift is a force as in pressure times area and can only be produced by a whole wing or at least wing section, not one spanwise station.


What are the ways to burn fuel faster in case of emergency without fuel dumping system?

This question (sorry to say) is sort of moot because:

if you have an urgency to land (e.g. cargo fire), you don't care if you are overweight and you'd land anyway
if you have time to dump fuel, the situation isn't as desperate, and you can easily wait just a bit longer.

The large jets (e.g. Airbus A380, Boeing 777) have a fuel dumping system because, with full fuel, these planes can travel up to 12 hours or more! That is to say, if you don't dump fuel, you might have to fly around all day to get down to your normal landing weight.

Airbus A320 and Boeing 737 are different: they usually fly 1~3 hours route, and may stretch to 6 hours on a full tank. So, to begin with, you need less time to burn fuel. Plus, these (relatively) small planes can land on shorter runways, which means your airport choice will not be as restricted as with a large jet.

Now, as to actually answering your question......

Flaps and gears have speed restrictions. You cannot fly full throttle with these deployed. That being said, if the pilots put the airplane in landing configuration (full flaps + gear down), drag will increase significantly and they will need more thrust to maintain altitude and airspeed.

You can technically achieve that with spoilers, but it's dangerous. Spoilers destroy lift, so what you're really doing is reducing the effectiveness of your wings and compensate that by flying faster and/or increasing your angle of attack.

Then again, if you're desperate, just land right away......