Fighter jet with two rudders, the deflection angle it is not identical. One have more angle of deflection. Why?

The jet in the top picture is turning slightly left using nose wheel steering, which is generally the same control as the rudder. I'm not aware of any fighter jet that has a tiller. Therefore the computer has commanded the rudders to deflect left. This is likely combined with a "toe in" (a characteristic of some fighters that aids in stability) of the rudders so it looks like only one has moved.

In the bottom picture, the flight control computer has decided that the best way to maintain the pilot's commanded attitude is to asymmetrically deflect the rudder. Flight control computers move surfaces in fly-by-wire systems, not pilots. Pilots just ask the computer if it is okay to do that. The computer decides if it is okay and how. It will use a combo of all the available surfaces to achieve the desired attitude within the programmed flight envelope and it doesn't have to do it symmetrically.


How should I interpret this TAF involving TEMPO and BECMG blocks?

TEMPO means that there were be fluctuations in the weather in the time period specified, lasting as long as 50% of the time range specified. TEMPO 0406 0150 FG VV001 means that in the period between 04:00 and 06:00 UTC the visibility will at some point go down to 150 in heavy fog, and it could last up to an hour in total.

One thing I would point out is that the time range for the TAF ends at 06:00, so its very likely the fog will last longer than that.


What is the main difference between 'continental fuel injection system' and 'Bendix RSA fuel injection system'?

First of all, both of these systems are continuous flow fuel injection systems, therefore they do not inject fuel directly into the cylinders. Since the fuel is flowing continuously from the injector nozzles, the spray is directed into the induction system just before the intake valve. That way, the fuel will only enter the cylinder when the intake air charge is drawn into the cylinder as the intake valve opens. Both systems have a throttle body to house the throttle valve, and a fuel servo/regulator to meter the correct amount of fuel and control the air to fuel mixture. The primary difference is how the fuel is metered. The RSA system (originally manufactured by Bendix Corp.) is found on Lycoming engines and is the next evolution after the pressure injection carburetor. The RSA system uses a combination of differential air pressure and differential fuel pressure to regulate and meter the fuel flow. The two sources of air are the low pressure air in the throat of the venturi and the high pressure air from the "ram air" entering the throttle body. At wide open throttle, these two forces have the greatest differential pressure, so they move a diaphragm and a valve in the fuel regulator to increase the fuel flow and pressure. The Teledyne Continental Motors fuel injection system does not use air metering force. This system relies only on differential fuel pressure.


What percentage of airliner flights globally are freight flights?

The National Air Traffic Controllers Administration states that:

  "On any given day, more than 87,000 flights are in the skies in the United States. Only one-third are commercial carriers, like American, United or Southwest. On an average day, air traffic controllers handle 28,537 commercial flights (major and regional airlines), 27,178 general aviation flights (private planes), 24,548 air taxi flights (planes for hire), 5,260 military flights and 2,148 air cargo flights (Federal Express, UPS, etc.). At any given moment, roughly 5,000 planes are in the skies above the United States. In one year, controllers handle an average of 64 million takeoffs and landings."

Therefore, if there are 28,537 commercial flights and 2,148 cargo flights;

28,537 + 2148 = 30685
(100 / 30685) * 2148 = 7.00016294606%

Thus there's for all of the airline flights taking off daily, 7% of them are cargo, and the rest are commercial.


Why does avgas 100LL smell different than automobile gasoline?

The sweet smell of 100LL AvGas is due in large part—if not entirely—to the additive Tetraethyllead (TEL). TEL is included in the formulation of 100LL as an anti-detonation additive, octane booster, and lubricant.

A fuel tester stored in the aircraft cabin should not induce crew illness because the tester should be drained of all but residual fuel, that residual fuel will evaporate very quickly—usually long before startup, and aircraft cabins are typically well ventilated.


Safety regulations for take off spectators around airports?

Most airports are intentionally built away from other areas because of practical problems like noise and potential structures getting in the way. There's also the rather significant requirements to build a runway itself (long, relatively flat and level). But there doesn't seem to be any hard minimum safety distances. It seems to be left up to the airport itself to determine safe distances.

One of the best examples I can think of (with limited clearance around the airport) is Princess Juliana International Airport in St. Maarten. The runway approach passes directly over Maho Beach, a road, and then you have a 7000ft runway (the largest flat spot the island can muster). In the picture below, the fence marks the end of the airport.

It produces some spectacular videos of planes passing less than 100ft over the beach and people watching on the beach are impacted by the blast of jets, who must stop at the end and bring their engines up to speed before starting their roll.

The incident mentioned happened at Skiathos Airport, which is also an island airport with limited land for a runway (shorter than St. Maarten at 5300ft).

So it seems to be that if you have a long, flat, and relatively level spot to build a runway, there's nothing to prevent you from building an airport there.


What exactly is a hot air pressure regulating valve, and what is its purpose?

The hot air pressure regulating valve does not generate hot air. The hot air is generated from the engine bleed air.

But that air does not go straight from the engines into the cabin, it would be too hot. If you want to adjust the temperature, you need a way of limiting the amount of hot air going into the cabin. That is what the regulating valve does (in conjunction with a couple of other components).


What is the best major to study for a career in propulsion systems design?

While the question is certainly subjective, I wanted to help you out as much as possible. I spoke to a friend who works as an electrical engineer at NASA and asked him your question. Based on his advice and some of my own research on your behalf, the most direct route would be to pursue an aerospace engineering degree in a good university program - CIT, MIT, UM Ann Arbor, etc. (there are plenty of schools to choose from). Most aerospace engineering students will choose a specialty in either an area of design or even in a specific type of vehicle - many universities will allow you to specialize in propulsion - essentially tailoring your electives to include subjects like fluid dynamics, multivariate and non-linear controls, combustive thermodynamics, and turbomachinery. That said, my friend indicated that the field can be very competitive, and that many propulsion system designers probably did not begin their career doing that kind of work. Be prepared to be flexible and plan on playing the long game when it comes to reaching your dream job. Also, as is the case in any competitive industry, networking can be key. Be sure to find opportunities to meet people in your field, ask questions, and get to know others who can give you the inside track on openings and opportunities.
Hope this helps.


Are there differences in air traffic services between western nations?

One of the big differences between regions is how aircraft operators pay for the service. In the US, the FAA is funded by taxpayers and fuel levies. In New Zealand (for example), aircraft operators are billed for use of air traffic control services. I don't know what the billing situation is in Europe.


You should refer to the published IAPs for an airport to determine if it has non-standard takeoff minimums (for AeroNav charts, this is the T in the black triangle). There's a section on this in the Instrument Procedures Handbook, Chapter 2 (2-6):

The FAA establishes takeoff minimums for every airport that has published Standard Instrument Approaches. These minimums are used by commercially operated aircraft, namely Part 121 and 135 operators.

14 CFR 135.217 describes the requirements for the alternate airport:

No person may takeoff an aircraft under IFR from an airport where weather conditions are at or above takeoff minimums but are below authorized IFR landing minimums unless there is an alternate airport within 1 hour's flying time (at normal cruising speed, in still air) of the airport of departure.

...and so does 14 CFR 121.617:

(1) Aircraft having two engines. Not more than one hour from the departure airport at normal cruising speed in still air with one engine inoperative.
(2) Aircraft having three or more engines. Not more than two hours from the departure airport at normal cruising speed in still air with one engine inoperative.

Part 91
14 CFR 91 does not require a takeoff alternate. I'm going to quote the IFH again because it's an authoritative FAA source and because I very much agree with it (2-6):

Aircraft operating under Part 91 are not required to comply with established takeoff minimums. Legally, a zero/zero departure may be made, but it is never advisable.


Is the Bendix/King KMD-550 airplane icon always oriented to the north?

According to the Source:

  The bottom is for the icon in track up mode. For the North up mode, It
  Depends on the Heading. The fix icon should be placed on one of the 8
  positions (up left, up right, up center, bottom left, bottom right,
  bottom center). For example, if the Heading is 45°, the fix icon is
  placed on the bottom left part of the screen.


Why is using opposite rudder and aileron necessary in left turn for coordination?

First and foremost you should always be looking at the turn coordinator to see what is going on and applying rudder as necessary.

In your specific case (if we want to discuss the physics), basically what your instructor is saying is that you are using the ailerons to bank (turn) the plane and the rudder to counteract the propeller's yawing moment. The rudder is simply counteracting the Adverse Yaw: the inputs will change depending on how steeply you are banking. If opposite rudder is called for on your ball, then step on it.

Perhaps more importantly, what your instructor is actually stressing is during your crosswind, base and final turns you should really be paying attention to staying coordinated. A great deal of Stall -> Spin -> Crashes happen in the pattern as planes slow down and dirty up, thus it's extremely important in the pattern to watch your speed and your turn coordination.


Is there a maximum horizontal acceleration for passengers?

It depends on several factors:
1) How long is the body subjected to these forces?
2) What's the posture of the body?
3) To what extent are the passengers used to g forces (for example due to training)?
...

However, early experiments showed that untrained humans could withstand g forces as much as 20 g for less than 10 seconds, to 10 g for 1 minute, and 6 g for 10 minutes.


How did the Boeing 777X's main landing gear lift before the nose on its first takeoff?

Correct on both guesses to some extent I would say.  The airplane is pretty light, and with flaps down the flapped area of the wing is operating at a positive AOA (remember that the chord line is from the LE of the slat to the TE of the flap, so with flap down there is positive AOA even while 3 point).

Also as it's an initial test flight I wouldn't be surprised if the pilot delayed rotation past normal Vr 5 or 10 kts just to have some extra energy margin if something went amiss, so not necessarily holding the nose down, but delaying pulling it up.

Added together, maybe helped by a bit of crosswind coming from that side, you get the truck starting to come off before rotation.


Are being +30 and having a Ph.D. considered as barriers to become an air traffic controller in NAV CANADA?

As a general answer (not pertaining just to Canada): any aspiring air traffic controller is very thoroughly tested before acceptance to a training program. Having any kind of previous education has little effect, say, higher academic merits, in my experience, may only represent someone's ability to function in academia.

Being a doctor of this or that certainly is not bad, but if an applicant holds many different credentials, it usually is, if not a red flag, a signal of the person's tendency to like studying more than doing.

ATC work is very demanding, and it requires a specific type of person: calm, focussed, extremely high tolerance to stress to mention some traits, etc. It is not a profession that I would recommend at first hand to anyone.

Regarding age, well, 50 is +30, so a bit vague definition there. If one is closer to 30, probably not a problem. Closer to 40, things are getting increasingly difficult. Thing with age limitation, or the lack of one is that declaring that age is not a limiting factor might be a politically dictated statement. Legislation probably demands that age cannot be a limiting factor when hiring people.


Can you be a pilot after being diagnosed with Generalized Anxiety Disorder?

The first thing is to determine if you were evaluated for anxiety, or diagnosed with an anxiety disorder.  Your primary physician's office can answer that because it will be in their records.

Often (not necessarily applicable in your case) symptoms which do not require ongoing therapy or medication may not have hard diagnosis.

Avoid assuming that you have a disqualifying condition.  Contact your physician and ask if you have that diagnosis.  It might help to explain why you are asking, specifically that you would like to fly and get an FAA Medical, so that they know the context of the question.

You might also want to read this FAA writeup on Item 47:

https://www.faa.gov/about/office_org/headquarters_offices/avs/offices/aam/ame/guide/app_process/exam_tech/item47/et/

As a final note, as an instructor I have had several students over the years who had serious, diagnosed psychiatric issues.  Most of them got effective help. A few became ineligible for a FAA medical. One refused to seek treatment as they were concerned about losing their medical. (I discontinued providing instruction, which aggravated the problem.) However, I know of no pilot or pilot wanna-be who had to take a class on anxiety or anger management, or personal relations, or similar to be denied an FAA medical on that basis alone.

In your case, the anxiety may have been situational, and developmental (as an adolescent) and clarifying whether you have a diagnosis (as opposed to just an evaluation) before you spend the big bucks for an AME exam would be appropriate.


Can heat from the engine inlet be used to produce thrust?

I guess the heat you ask about is the temperature increase that goes with the precompression of air ahead of and in the intake. This heat is further increased in the compressor, according to the ideal gas law. If there were no temperature increase during compression, the engine could burn a lot more fuel and produce a lot more thrust.

To use the precompression heat would mean that first the air flows through a heat exchanger in order to transfer that heat to something that can produce thrust from it. That something would have to heat the air in the combustion chamber or after the last turbine stage in order to increase thrust. At both stations the gas temperature is a lot higher than the heat that can be harvested from the intake air. Now you first have to run that heat through a heat pump to make it useable (or, if you turn this around, you need a heat pump to produce a medium cold enough to harvest heat from the intake air in the first place!).

I hope you start to see how much more complicated and heavy this kind of engine will become. There have been attempts to recuperate the heat of the exhaust flow in turboprops, but so far nothing of that kind has ever entered production.


Why are combi airliners no longer being built?

While combi configurations are rare, they do have a place -- for instance, when operating narrowbodies into remote locations which have a demand for cargo that exceeds what can be put in the belly, but also need pax transport.

The most recent combi configuration I can find a source for is the 2008 work done by Aviation Traders to configure Iron Maiden's touring plane.  In this case, they used the existing seat rails to mount pallet fittings in order to avoid structural changes to the floor, and also are taking special steps (such as firebagging of cargo) to mitigate against a main deck cargo compartment fire.

As to why they aren't made otherwise?  It clearly isn't operating economics, at least for Alaska Airlines, Canadian North, First Air, and other current combi operators -- otherwise they'd have retired their combis by now.  The main issue, I strongly suspect, is actually the unsolved problem of fire suppression in large, main deck class B cargo compartments, such as those found on combi aircraft.  Aviation Traders' work on Class F is intended to solve this problem, made famous by the crash of SAA 295 after its main deck class B bay experienced a fire of unknown origin that proved catastrophic.


Why is LGA's Instrument Approach Procedure VOR-H misaligned with the runway?

Not all approached are aligned with a specific runway; some like this VOR approach into KLGA is not and just uses circling minimums.

It is anticipated that the aircrew will, after reaching the MAP at MDA, visually confirm that they have the intended runway of landing in sight, thence circle to land on it visually at or above the circling minimums published.  The landing runway would be given by ATC or requested by the flight crew thence approved by ATC.

Nonprecision approaches with circling minimums only are quite common.  They are created this way only if:

  The final approach course alignment with the
  runway centerline exceeds 30°.

  The descent gradient is greater than 400 ft/NM from
  the FAF to the threshold crossing height (TCH). When
  this maximum gradient is exceeded, the circling
  only approach procedure may be designed to meet
  the gradient criteria limits. This does not preclude a
  straight-in landing if a normal descent and landing
  can be made in accordance with the applicable CFRs.

  A runway is not clearly defined on the airfield.

See the FAA’s Instrument Procedures Handbook.


Why are delta wings not commonly used in commercial airliners?

There's a thread on airliners.net about the same topic.

  One of the most prominent and useful aspects of the delta wing is the fact that it increases an airplane's critical Mach number (the speed at which some air passing over any part of an aircraft - usually the wing - reaches Mach 1.0).

By increasing the critical Mach number, it makes supersonic flight much more feasible on delta wings than on conventional wings.

Delta wings are particularly happy even at a high AoA (angle of attack). This is because of the reaction lift generated by the wing, and the vortex created at the leading edge of the wing. Hence, airplanes with delta wings have a much higher tolerance to stalling. This makes it easier to attain higher vertical speed, also known as "rate of climb" safely.

But on the flip side:

  One of the downsides of deltas is that they create more drag, because of the bigger surface area, but they do have a bigger internal volume (for fuel, for example) which could lead to a smaller fuselage, or more space in the fuselage for other things. Another disadvantage is higher landing and take off speeds.

The last point is particularly important. The Concorde's already small number of usable airports was reduced because the runways needed to be long enough to accommodate for the 160 KIAS landing speeds (for comparison, typical turbofan-based airliners lands at 130-140 KIAS).

As a result of the higher takeoff/landing speeds, the  cost of maintenance of vital components such as the brakes and tyres is higher. Moreover, the high landing speeds can even lead to greater stress on the airframe. So, indirectly delta wings do contribute to a higher cost of maintenance.

Other disadvantages of delta wings I can think of is the lack of a flaps/slats system. Delta wings don't require flaps as they can simply reduce their airspeed by increasing the AoA, but the lack of flaps reduces their subsonic efficiency, and increases the takeoff distance and takeoff velocity. For instance, the Concorde's delta wings produced very little lift during takeoff prior to rotation, necessitating high takeoff speeds of nearly 220 knots!

As an answer to your second question, I could not find anything about regulations relating to the use of delta wings on airliners.

All in all, delta wings work well for niche purposes such as supersonic aircraft, but their disadvantages and poor operating economics make them impractical for subsonic flight.

However, as you can see here, the now-scrapped Boeing Sonic Cruiser attempted to make the best of both worlds by combining a conventional wing with a delta wing, to form a wide, "cranked-delta" wing design.


Outlook VFR is usually found in the so called "Area Forecast". It is the last part of the portion which describes clouds and weather, which could affect VFR operations.

The area forecast for every region is valid for 12 hours, followed by a 6 hour categorical outlook.

There are three types of outlooks, VFR, IFR and MVFR (marginal VFR). As mentioned in Jeppesen's Guided Flight Discovery Instrument/Commercial Manual:

  A ceiling less than 1,000 feet and/or visibility less then 3 miles is
  considered IFR. Marginal VFR areas are those with ceilings from 1,000
  to 3,000 feet and/or visibility between 3 and 5 miles.

Everything "better" (as in higher ceiling and/or visibility) is considered VFR.

Here is an extract from an Area Forecast:

CLDS/WX VALID UNTIL 062100...OTLK VALID 062100-070300
[...]
NRN PEN...BKN010-020 TOP 100. OCNL VIS 3SM BR. BECMG 1214 BKN025
TOP 120. ISOL -SHRA. 18Z BKN040 TOP FL220. WDLY SCT -SHRA/TSRA.
CB TOP FL420. OTLK...VFR TIL 02Z SHRA TSRA.

The first part is an extract from the Heading Section. here you find the time for which the Clouds and Weather part as well as the Outlook part is valid.
The second part consist of the mentioned Clouds and Weather as well as the Outlook. I'm not going to decipher the whole thing now, but here is a short explanation:

You can see the more detailed forecast, valid from the time of loading the Area Forecast to 062100, which means the 6th of the month, 21:00 Zulu time. After that, from 062100-070300 so from the 6th at 21:00 Zulu until the 7th at 03:00 Zulu, the outlook is what counts. In this case it is VFR until the 7th of the month at 02:00 Zulu, where showers and thunderstorms (in connection with rain) are expected.

Conclusion: The outlook gives a general idea what the weather will be like up to 6 hours after the forecast part of the Are Forecast. This can help in flight planning.

For more information about VFR refer to DannyBeckett's detailed answer.


How is health monitoring of large aircraft engines and components done?

Methods of recording data and what's monitored differ between manufacturers but speaking as a Rolls Royce employee, the engine I'm responsible for, the AE2100D3 on the Hercules, is done via downloads. The flight computer records many different channels during flights and ground runs which are downloaded daily, then trended and analyzed. RR HQ then flag any anomalys and send out data for customers to act on, i.e. vibration problems, reduced performance etc. Big engine such as Trents are monitored in real time whilst they fly which is really impressive.

As regards to what exactly is measured, I could list lots of stuff but primarily it's broken down into vibration (all rotating components vibrate, and have allowable limits for this) and performance (referencing pressures and temperatures through the engine to give a performance margin or figure) Anything that either exceeds or drops below set limits raises a maintenance alert.
Engine control units/FADECs constantly monitor all sensors, as do the crews, again anything that needs attention will trigger some sort of warning or information system
Generally through trending and graphs, or in terms of component lifing, etc there will be a count.


Why are geodesic airframes no longer produced?

Geodesic (sometimes also spelled geodetic) designs were used in aviation as early as 1909, in the Schütte-Lanz SL1 airship. It had a wooden structure with fabric covering, and Professor Johann Schütte, the scientific head of this design, used the most efficient method conceivable. However, planning the shape of all structural members was an enormous amount of work, and stretching an existing ship by inserting a new section was almost impossible. For those reasons, the late Schütte-Lanz airships used aluminum frames with conventional design, just like Zeppelin did from the beginning. Diagonal wire bracing was used to take up shear loads.

Geodesic frames are good in transferring both bending and shear loads. This is helpful when the aerodynamic covering is not stiff enough to contribute any shear stiffness, as in the case of fabric covering. However, when the skin is made from the same material as the frame, it can carry shear loads and a geodesic frame would not improve matters. Now it is better to carry longitudinal loads in longerons and shear in the skin.

But geodesic constructions are not dead. CAD makes the design effort manageable, and in some cases they give a weight advantage. Look at the casing of the EJ200 engine: It uses a geodesic reinforcement to make the casing light and strong and to prevent harmful vibrations. In the end, a jet engine casing is a big pressure vessel and needs to be strong, stiff and light.

photo by Julian Herzog, CC-BY


Is there a benefit to representing a SID/STAR in 3D?

I have flown aircraft with Augmented Enhanced Reality built into their PFDs. They represent a desired flight path on the PFD with a rectangle whose unit of measure is dependent on the phase of flight. For example purposes, you would see a box on the PFD roughly 200 feet high by half a mile wide with 1 to 5 miles between each box in the enroute phase of flight. Your goal is to fly through each box. There is a dot or crosshair target on the screen to represent your actual current flight path based on trend vectors and statistics like airspeed, ground track, vertical speed, and rate of turn. Keeping the target centered in the boxes will keep you on your flight plan entered into the system. I have seen this system in Garmin and Dynon equipped aircraft.

Flight Directors and autopilots with Flight Directors can give you visual cues for pitch and bank corrections based on your programmed flight plan and actual flight vectors.

Also, apps such as Foreflight will graph out your entire flight plan including instrument procedures in virtual reality. It will then allow you to virtually fly the plan in 3D for preflight planning.

I don’t find this last resource useful in actual flight. Any other tablet based 3D representation would be just as bad. A simple piece of paper would be preferable in actual IFR flight. Any technology that would increase pilot workload any further than it already is in IMC would be dangerous. More than a couple of seconds to look at the information you need clearly displayed would be too long. The current charts facilitate rapid information retrieval by using standardized formats for every chart. There is no need to fiddle with gadgets unnecessarily.

One way this can be very useful is for at home training. Get a few pictures as large as possible taped under your tv or monitor. Have all of your charts, sectionals, and checklists applicable to a real, normal flight out and ready. Then, chairfly the entire flight from preflight planning to hangaring the aircraft in detail. Play the 3D virtual reality representation of the flight on your tv or monitor when it comes time for the flight phase.

By the way, your standard ILS or GPS approach in a linked standard six-pack already represents the information in 3D. You just have to be able to interpret it as such.


How can I properly model paper airplane physics?

I would model the energy flows between kinetic and potential energy. Start with a full bucket of potential energy plus the appropriate speed and drain kinetic energy away over time depending on flight speed.

To know how much energy is lost to drag, you need to model the drag using two components:

Friction drag, which grows with the square of airspeed, and
Induced drag, which drops with the square of airspeed.

If your drag is the sum of both, its minimum will be at some moderate speed. I plotted the drag components for a glider below, but since the physics are the same for a paper airplane, this plot should do for now.

The nonlinear behavior of the induced drag curve at low speed is due to flow separation, and something very similar will happen for a paper airplane. The important thing is: The drag curve has a minimum.

The energy loss over time is drag $D$ times speed $v$. This energy $E$ has to come from the reduction of height $h$ over time $t$:
$$\frac{\delta E}{\delta t} = \frac{\delta(m\cdot g\cdot h)}{\delta t} = D\cdot v = m\cdot g\cdot v_z$$
with $m$ the mass of the paper airplane, $g$ gravitational acceleration and $h$ its height above ground. Only $h$ changes over time, so derivation is easy and the derivative of $h$ is $v_z$, the vertical speed.

For picking a realistic drag it helps to rephrase the equation above by introducing lift $L = m\cdot g\cdot n_z$. $n_z$ is the load factor and is approximately one in straight flight. The ratio between lift and drag for a paper airplane is somewhere between 4 and 10 - just pick a number which results in a realistic simulation. To calculate the sink speed $v_z$ as a function of flight speed $v$ use this formula:
$$v_z = \frac{c_{D0}\cdot S\cdot v^3\cdot\rho}{m\cdot g\cdot 2} + \frac{m\cdot g\cdot 2}{v\cdot\pi\cdot b^2\cdot\rho}$$
S is the wing area of the paper airplane and $b$ its wing span. $\rho$ is air density, and for the zero-lift drag coefficient $c_{D0}$ you should pick a number which makes the paper airplane look realistic. Start maybe with 0.05.


What is situational awareness and why is it important?

A simple definition of situational awareness that you are aware of the different situation happening around you, know why they are happening and can think of an action you need to take to tackle with those.

In aviation, situational awareness means:

  For a pilot, situational awareness means having a mental picture of
  the existing inter-relationship of location, flight conditions,
  configuration and energy state of your aircraft as well as any other
  factors that could be about to affect its safety such as proximate
  terrain, obstructions, airspace reservations and weather systems. The
  potential consequences of inadequate situational awareness include
  CFIT, loss of control, airspace infringement, loss of separation, or
  an encounter with wake vortex turbulence, severe air turbulence, heavy
  icing or unexpectedly strong head winds.

As far as your second question, hypothetically speaking, one can say that going through the preflight checklist, pilots are more focused inside the cockpit mostly and the situation outside the airplane is not too much of concern until they pay attention to that.

Generally speaking, when the airplane is not moving, situational awareness can be lesser. It is same as when you are driving, at what time you have lesser situational awareness?


What is the correct range of the 787-10?

The range of an aircraft depends on the payload. The value you typically find is the range at typical payload.
You can find the payload/range diagram in the Boeing 787 Airplane Characteristics for Airport Planning document:

As you can see, at maximum zero fuel weight, the 787-10 range is only ~4200 NM. According to Wikipedia, the typical passenger configuration for the 787-10 is 330 seats in a 2-class layout. Assuming 195 lbs per passenger (FAA average adult passenger weight in winter) plus 50 lbs baggage per passenger, gives a typical payload of 80,850 lbs. This would result in a range of ~6000 NM. If not everyone onboard is an adult and not everyone takes the full 50 lbs for baggage, the range can be higher of course. Completely empty, the 787-10 can easily fly over 8500 NM.


Why don't NK-12 powered contra-rotating propellers turn in equal rpm?

The NK-12 engine uses a differential epicyclic (planetary) gearbox. Unlike the typical planetary gearboxes where one of the gears is fixed, here all three parts are moving: the turbine drives the sun, the planet pinion drives the front propeller, and the ring drives the rear propeller.

The gear ratios are the same between the front and rear, but the torque is not. The difference you see has to do with this torque difference, as well as with different rotating masses and friction during start. The torque is what is actually important.

If you hold one part, then the other two will be in the expected sync. Say, if you jam one prop and start the turbine, it will simply spin the other prop twice as fast. (But if you jam the turbine, things will be less intuitive: the props should turn in the same direction if you move one by hand). Now if you allow the turbine to free spin, you'll have two degrees of freedom, and the eventual relative RPM in such system will depend on the torque on each prop.

In the explanation below, I use this work by S. Falaleyev et al (pdf in Russian). Here is the diagram of the gearbox:

If we assume the torque balance such that the RPMs are the same (except the sign), the gear ratio will be (I skip the derivation):

$$i = 1 + 2(\frac{z_2 \cdot z_4}{z_1 \cdot z_3})$$

($z$ are the teeth numbers according to the diagram). For the given numbers we get $11.33$ (or rather, it should be $1/11.33 = 0.088$ reduction). The nominal speed of the props was just 735 RPM!

At the same time, the torque ratio (front to rear) is

$$\frac{M_f}{M_r} = -(1 + \frac{z_1 \cdot z_3}{z_2 \cdot z_4}) \approx -1.19$$

Thus, the front prop gets almost 20% more torque than the rear prop. This is why it spins up faster on start-up. (It is also lighter than the rear one).

At the nominal speed, the governor automatically sets a finer blade pitch on the rear prop to equalise the speeds. (Why not just accept higher speed/thrust from the front prop? Apparently, because the prop is limited by the tips speed, and we don't want the front one go supersonic while the rear one is relaxed).


How would a fighter be changed from having static stability to having relaxed stability?

The first and most important step is to move the center of gravity back relative to the neutral point of the configuration. This is done either by shifting masses on the airframe back or by shifting the wings forward. This needs to be complemented by the addition of a multiple redundant and fast flight control computer.
Now the tail will add lift instead of downforce, so the wing area required for manoeuvring and take-off/landing can be reduced. Or performance improves - compare the minimum speed of the Mirage III to that of the Mirage 2000.
To see how much the wing area could be reduced, here is a comparison drawing of the regular SEPECAT Jaguar with one designed for the same requirements, but with relaxed stability (copied from this answer). The forward shift and reduced area of the wing should be obvious.

Comparison of conventional Jaguar (top half) and CCV version (bottom half) by Ray Whitford.
What is done to a specific airframe depends on the objectives for the move to relaxed stability: This could be much better supersonic range or better short field performance. For the first you will shrink the wing, for the second you better keep wing size but move it forward and heavy items back. The change from the one engine of the MiG-21 to two more powerful engines certainly helped to shift the center of gravity of the J-8 back.
Usually all of the methods you mention are used in combination (except for the clever aerodynamic device, unless you mean a sophisticated FCS):

The wings are resized/moved
The tailplane would be made smaller
Internal items will be shuffled around or exchanged to shift the center of gravity further back.


What is the purpose of fins on the empennage on some helicopters?

It's a stabilator used on the Blackhawk to reduce attitude changes with airspeed and to offset pitch effects from the tail rotor.  It's part of the automatic flight control system.

All "traditional" design helicopters have horizontal stabilisers to push the tail down to reduce the nose down pitch in forward flight.  Fixed ones are normally trimmed to provide a more level deck at typical cruise speed.

On the Blackhawk, it's fully movable. It is automatically adjusted according to collective pitch and airspeed. From here, the benefits are:

Align stabilator and main rotor downwash in low speed flight to minimize nose up attitude resulting from downwash.
Provide collective coupling to minimize pitch attitude excursions due to collective inputs from the pilot.
Decrease angle of incidence with increased airspeed to improve static stability.
Provide sideslip to pitch coupling to reduce susceptibility to gusts.
Provide pitch rate feedback to improve dynamic stability.


What do the different types of approach abbreviations used on the A320 MCDU exactly mean?

CI = course to intercept
CF = course to fix
FI = fix to intercept
CD = course to DME
FD = fix to DME
These are AIRINC 424 leg types. You can find more information on them here


How do I find the serial number and other important information of an old airplane I have?

There are three pieces of paper the FAA issues which would fall under the concept of "title" to an aircraft.

The first is an aircraft lien (typically held by a bank when you take out a loan collateralized by the aircraft). This is probably not what you're looking for, but you should inquire as to whether any liens are held against the aircraft before doing any work, just to be sure you have "clear title" to the results of your work.

The second is an Aircraft Registration Certificate - this is a record tying the N number (in your case N97554) to the aircraft itself.
In your case the registration is Revoked, so once reassembled the aircraft would need to be re-registered to be flown. This would be a "Call your local FSDO" situation - Presumably the registration was revoked when the aircraft registry changed to a 3-year expiring registration period.  Also as there are multiple owners listed on the registration re-registering may require more work.

The final piece of paper you need is an Airworthiness Certificate - this should be in the aircraft, and is valid forever. If it's not in the plane you can get a replacement - again, contact your local FSDO.

If you need information you don't have, or want to confirm it before talking to the FAA, look for the aircraft data plate. On Stinson aircraft (going by the N number you provided) the data plate is usually located on the firewall above the copilot rudder pedals as shown here.
On newer metal aircraft it is often located on the tail, under the horizontal stabilizer.

For more information on the aircraft itself check out stinsonflyer.com.


Why was blue hydraulic system chosen for RAT?

Because in A320 is the only hydraulic system independent from the engines and isolated from the other two hydraulic systems (while G and Y have the PTU in common). Also the B hydraulic system is able to control both elevators and ailerons, while Y cannot control ailerons and G controls only the left elevator. That's a design choice taking in account all the possible failures to reduce the risk of a triple hydraulic failure.

There are two switches that allow you to open the RAT:

The RAT MAN ON (on HYD panel), which open the RAT and feeds the B HYD
The RAT MAN ON (on EMER ELEC panel), which has the same effect of the previous one, but it also connects the emergency electrical generator

Please also note that in case of a dual engine loss, the RAT is automatically deployed.


The aircraft in question is an Embraer ERJ 175 the "dent" allows the tail trim to operate properly you can see it more clearly in this picture.

(source)


How do you communicate with a military drone operator over radio?

Some UAVs carry VHF or UHF airband radios to communicate with air traffic control and other aircraft. The voice channel is relayed to and from the remote pilot operator via satellite or another form of datalink. I've heard UAVs taking with Joshua Approach in the Mojave Desert, and one time Joshua called one out to me as traffic and vice versa. I agreed to maintain visual separation, the remote pilot acknowledged and overall it was very similar to dealing with any other aircraft.

I have no idea whether they monitor 121.5 as well as whatever enroute frequency they're using, but it seems plausible that they could.


Does this trip count for the commercial 300NM cross country requirement?

Yes.  It counts.  One leg needs to be at least 250NM and you have a 280NM leg.

§61.129   Aeronautical experience.
(4) Ten hours of solo flight time in a single engine airplane

(i) One cross-country flight of not less than 300 nautical miles total distance, with landings at a minimum of three points, one of which is a straight-line distance of at least 250 nautical miles from the original departure point. However, if this requirement is being met in Hawaii, the longest segment need only have a straight-line distance of at least 150 nautical miles;


Does anyone know where I can find old TFRs?

As you know, a TFR is published in FDC NOTAMs, so you can use the FAA's NOTAM search tool's "Archive" mode to search for past TFRs issued via FDC NOTAMs.

Use this link (https://notams.aim.faa.gov/notamSearch/nsapp.html#/). Press the Location button on the left and select "Archive Search." Then select a Date and Location designator to search for the NOTAMs (including TFRs) in effect on that date in that area.

By way of example, I did a search for Riverside Municipal Airport (KRAL) on 2/2/2016, and it returned these old NOTAMS (included TFRs).  See the California Speedway TFR.


Is it possible to buy a retired Boeing 747 aircraft?

Sure, the 747 is a Type Certified and airworthy aircraft, the FAA does not really care who owns it so long as they play by the rules. Boeing even sells them directly to the private market via their BBJ line.

There are even a few used ones listed for sale right now.

Some people even buy them for other purposes than flying them...

  for how long will boeing keep maintaining its aircraft in light of
  manufacturing spare parts and innovating it

this is impossible to speculate on as its their decision ultimately but considering how many 747's there are you will be flying it long into the future.


What are the most number of propellors that a rotorcraft has been flown with?

This guy is actually flying with 76 rotors.

But I might argue that your "more rotors is faster" idea may be flawed, smaller propellers are less efficient (because the further from the center you are, the faster the blade is moving, if I'm not mistaken), so the trade may be fewer, more efficient, propellers for a larger number of less efficient ones.


How are jet engines certified against birdstrikes?

There are hundreds of tests that need to be performed for certification of a turbine engine.

The FAA requirements and tests are listed in CFR part 33 E and F.

Amongst them are:

Maximum static thrust tests
Vibration tests
Endurance tests
Water ingestion test
Hail ingestion test
Ice cloud test
Bird strike test

A number of them can be seen in this video of the GE90-115 Engine

The specific requirement for bird ingestion are described in §33.76. The number of birds to be used and their weight depends on the area of the engine inlet.

There have been several changes to the bird ingestion requirements for certification since the A320 engine was certified in 1996. However, once an engine is certified there is no need to demonstrate compliance to the updated requirements; the engine remains certified as it was.

The latest update to these requirements was in 2007, prior to the Hudson accident. To answer your question: no, there have not been any changes to the bird strike testing requirements of engines in the aftermath of the Hudson accident.


Is there any clear picture or drawing, of a Wright brothers' plane, published before August 12, 1908?

I am not aware of any picture printed before August 1908 and showing a fully recognizable Wright plane, beyond any doubt.
As a remark, there exists a drawing, published in L'Auto, a French newspaper, on December 24, 1905, but it is just a rough sketch. However, this caricature is the closest drawing to what would become to be known as the Wright planes, much later, starting with August 1908.
As an explanation: Robert Coquelle, a French journalist, while in the United States for other purposes, visited the Wright brothers, did not see any plane and once back in France he made fun of them in L'Auto in an article titled: "The conquest of the air by two bicycle dealers". Coquelle does not clearly explain the origin of the drawing below that illustrates his article.

The true aeroplane of the Wright brothers.
Source: 1905-12-24, Robert Coquelle, “La Conquête de l’Air par deux Marchands de Cycles. Comment un ancien champion cycliste, Johanny S. Johnson, introduisit un rédacteur de « l’Auto » dans l’atelier des frères Wright.”, L’Auto, Paris, Saturday, December 24, 1905.


How do we derive Lift Coefficient of an airplane's wing?

The lift coefficient accounts for complex aerodynamic effects that are impossible to calculate by hand in any practical way. I'm not sure what you mean by "In my opinion, even it correct mathematically, but is not correct in the engineering as the it is not product of mathematic." My best guess is that you're pointing out that even though you can rearrange the lift equation to calculate $C_L$, it's not derived from first principles, which is correct. It's a convenient way to represent more complex interactions that are difficult to calculate.

Essentially, we know lift varies linearly with dynamic pressure ($\frac{1}{2} \rho V^2$) and it varies linearly with surface area. So the lift equation may be written, in its most reduced form,
$$L = C_L q S.$$
Notice the similarity to the drag equation:
$$D = C_D q S$$
And the pitching moment equation:
$$M = C_M q S c$$

Each of these quantities varies linearly with dynamic pressure and surface area, so it's useful to express them as products of these quantities. Changing either of these variables will probably affect the aerodynamic coefficient as well, but for modeling purposes that don't require extreme precision, in most cases, the aerodynamic coefficient won't change nearly as much as dynamic pressure can.

As a result, knowing $C_L$ and $C_D$ for a variety of flight conditions, you can model your body of interest with fairly good accuracy without having to go through the complexity of computational fluid dynamics, which is the numerical way to predict aerodynamic forces.

To answer your question about a formula to calculate the coefficient of lift, there are methods that will allow you to get a rough estimate (e.g. lifting line theory), but to get results comparable to wind tunnel testing, you have to use computational fluid dynamics, which will require a computer to achieve meaningful results.


Why do you have to keep your seat belt fastened after landing?

Ground operations are just as dangerous as air operations. Strictly speaking the deadliest aviation incident actually happened on the ground (not saying seatbelt played a role or not however severe accidents do happen on the ground). The comments cover things well, (keeping people seated, keeping people from accessing over head compartments etc.) Planes are not safe simply because they are on the ground, they are only safe from flight related incidents and once on the ground they are susceptible to ground related incidents. By some estimates 27,000 ground incidents happen a year. The fact remains there are plenty of things to hit on the ground and plenty that can go wrong in taxi. These accidents are classified by ICAO under (RAMP) and (GCOL) codes (and potentially others). Boeing has a breakdown of accidents by flight category (taxi and ground ops make up about 10%).

Furthermore here in the US under the FAA FAR 91.107 as well as FAR 121.311 in the commercial case(basically the same wording) requires it

  ...(3) Except as provided in this paragraph, each person on board a
  U.S.-registered civil aircraft (except a free balloon that
  incorporates a basket or gondola or an airship type certificated
  before November 2, 1987) must occupy an approved seat or berth with a
  safety belt and, if installed, shoulder harness, properly secured
  about him or her during movement on the surface, takeoff, and landing.
  For seaplane and float equipped rotorcraft operations during movement
  on the surface, the person pushing off the seaplane or rotorcraft from
  the dock and the person mooring the seaplane or rotorcraft at the dock
  are excepted from the preceding seating and safety belt requirements....


If your child is going to be around airplanes and flying with you for the next 12 years, they're not going to need to log time from back when they are 4 years old. They will have plenty of logged time later in life.

I would suggest that you pick an age, say at least 8 or 10, where your children can start to fill in log books of their own. If they keep an interest in aviation until that time, getting their own log book that they can fill in themselves will be a big step for them to look forward to.


Does anyone have free plans for a ultralight?

Your best bet is a Sandlin Goat, with free plans for download and quite a few built.  It's a soaring glider but some have added motors, although that eats into the useful load.  A motor would have to be a 2 stroke to have adequate power for the weight, (you want about 25 hp) and it would be best to use an off the shelf paramotor engine.  I would just purchase an old used paramotor cage/motor to get the motor/reduction drive/prop and rebuild the motor.  A goat itself is still going to cost you at least 5k to build from scratch, probably at least half that in the cost of fabric covering process, before the motor.  Then of course you have to engineer a way to attach the motor with adequate structure that can handle several Gs, doesn't screw up the weight and balance, etc etc etc.

Aviation, even at that level, ain't cheap.

But before all that, you have to get training to avoid killing yourself, so save up a couple grand first and go to an ultralight flying school for lessons.


Why is a large flashing "X" placed on a closed runway at Reagan National Airport?

The standard way of marking a runway as "CLOSED" is to put a big giant X on it - for fields which operate at night that X needs to be lighted. The specifications for the runway closure marker are outlined in an FAA advisory circular (AC 150/5345-55A)

The purpose of the marker is to indicate that the runway is temporarily closed (either administratively, as is the case at DCA, or for construction/repair/maintenance).  It is redundant with air traffic control measures (such as NOTAMs) indicating that the runway is out of service, in case some pilots didn't check NOTAMs or somehow managed to stumble into the airspace and happen upon the airport while it's closed.  (Obviously in the case of DCA they would have other problems were they to wander blindly into the area without talking to anyone, but believe it or not it happens far more often than any of us would like.)

The big flashing X doesn't "stop" you from landing on the runway - it just tells you you really, really shouldn't be landing there. There is a United States Senator who has achieved some notoriety in the aviation community after landing on a closed runway.

The X is also quite a bit bigger than you think it is to ensure it's visible from the air  (the arms are 14 feet long):

(I was looking for a good aerial photo of one at night, but unfortunately couldn't locate one. The intent is for the X to be about the same size as runway numbers so there's no good reason for a pilot to not see it.)


Are the requirements for an initial type rating the same across types?

Actually, it doesn't matter whether you are a Private pilot or an ATP, the requirements for a type rating are in the Airline Transport Pilot and Aircraft Type Rating Practical Test Standards, which apply regardless of the aircraft type.

In the PTS, it says:

  Practical Test Book Description

  This practical test book contains the Airline Transport Pilot and
  Aircraft Type Rating Practical Test Standards—Airplane.  The Airline
  Transport Pilot and Aircraft Type Rating Practical Test
  Standards—Airplane includes Areas of Operation and Tasks for the
  initial issuance of an airline transport pilot certificate and for the
  addition of category, class, and aircraft type ratings to an airline
  transport pilot certificate. These Areas of Operation and Tasks also
  apply for the issuance of an airplane type rating to a private or
  commercial pilot certificate.

You basically cover everything needed for the ATP.  The differences between the different airplanes come out during the practical test just like they do for any other checkride.  The examiner (who will be typed in the airplane) asks you about the things that are specific to each airplane, but this isn't really a lot different than him asking you questions specific to a Cessna or a Piper during your private pilot checkride.

The PTS specifies general Areas of Operation's instead of saying exactly what needs to be tested for every aircraft type.

Here they are for a type rating:

  Section 1: Preflight Preparation

  Areas of Operation

  I. Preflight Preparation
  Task A: Equipment Examination
  Task B: Performance and Limitations
  Task C: Water and Seaplane Characteristics (AMES/ASES)
  Task D: Seaplane Bases, Maritime Rules, and Aids to Marine Navigation (AMES/ASES)

  Section 2: Preflight Procedures, Inflight Maneuvers, and Postflight Procedures

  Areas of Operation

  II. Preflight Procedures
  Task A: Preflight Inspection
  Task B: Powerplant Start
  Task C: TAXIING
  Task D: Sailing (AMES/ASES)
  Task E: Seaplane Base/Water Landing Site Markings and Lighting (AMES, ASES)
  Task F: Pre-Takeoff Checks

  III. Takeoff and Departure Phase
  Task A: Normal and Crosswind Takeoff
  Task B: Glassy Water Takeoff and Climb (AMES/ASES)
  Task C: Rough Water Takeoff and Climb (AMES/ASES)
  Task D: Confined-Area Takeoff and Climb (AMES/ASES)
  Task E: Instrument Takeoff
  Task F: Powerplant Failure during Takeoff
  Task G: Rejected Takeoff
  Task H: Departure Procedures

  IV. Inflight Maneuvers
  Task A: Steep Turns
  Task B: Approaches to Stalls and Stall Recovery
  Task C: Powerplant Failure—Multiengine Airplane
  Task D: Powerplant Failure—Single–Engine Airplane
  Task E: Specific Flight Characteristics
  Task F: Recovery from Unusual Attitudes

  V. Instrument Procedures
  Task A: Standard Terminal Arrival/Flight Management System Procedures
  Task B: Holding
  Task C: Precision Approaches (PA)
  Task D: Nonprecision Approaches (NPA)
  Task E: Circling Approach
  Task F: Missed Approach

  VI. Landings and Approaches to Landings
  Task A: Normal and Crosswind Approaches and Landings
  Task B: Landing from a Precision Approach
  Task C: Approach and Landing with (Simulated) Powerplant Failure—Multiengine Airplane
  Task D: Landing From a Circling Approach
  Task E: Rough Water Approach and Landing (AMES/ASES)
  Task F: Glassy Water Approach And Landing (AMES/ASES)
  Task G: Confined-Area Approach and Landing (AMES/ASES)
  Task H: Rejected Landing
  Task I: Landing from a No Flap or a Nonstandard Flap Approach

  VII. Normal and Abnormal Procedures
  Task A: Normal and Abnormal Procedures

  VIII. Emergency Procedures
  Task A: Emergency Procedures

  IX. Postflight Procedures
  Task A: After-Landing Procedures
  Task B: Anchoring (AMES/ASES)
  Task C: Docking and Mooring (AMES/ASES)
  Task D: Beaching (AMES/ASES)
  Task E: Ramping (AMES/ASES)
  Task F: Parking and Securing


Why are airliner cockpits not shielded from lasers?

Money aside there is a bit of a practical reason as well. One of the simplest ways to protect against lasers is by filtering it using glass of a particular color, depending on the laser we are talking about red or green glass (and some other colors here and there as well). Generally they look something like this

Coating an airplane windshield in glass of this tint, or a green tint would potentially impair the pilots ability to properly view PAPI or VASI lights which require red/white or red/green differentiation.

It would also cause the pilot to perceive all lights (during a night landing) differently.


Why don't B747s start takeoffs with full throttle?

The other answers are spot on, but I'd like to address one part, which is the "later down the runway." It is by no means "later."

(YouTube)

In the frame grab above of a 747-400 (taken at 1:12), the captain had already called out "takeoff thrust," the TO/GA system had set the pre-programmed thrust setting, and the 747 wasn't even at the piano keys. (Auditory cues can be misleading to passengers or air side spotters.)

Typically, a low thrust setting is set to make sure all the engines are responding in the same way, and more importantly, will have uniform application of thrust thereafter. This can be done with (standing takeoff) or without the brakes on,$^1$ or during a rolling takeoff. Then it is TO/GA time. (In tail-wind conditions, the procedure may vary.)

Here's another video by JustPlanes from inside the cockpit. Again TO/GA was pressed while the plane was at a crawling pace far from being anywhere later down the runway.

$^1$ Boeing 747-400 FCTM § 3.4


In short, they are both scams that fall heavily into the category of Not Even Wrong or cargo cult science.Tesla's work is sadly a great favourite of conspiracy theorists who do not have the technical background to adequately understand why these devices do not function as intended.
Your "Cold Jet" link should scream "I do not know what I am talking about" not only because of the broken, rambling sentences (although admittedly thats not exactly a rare quality amongst many actual professors) but also because of the over reliance of handwaving any problems away to just an "on board compressed air source"; without any mention of exactly how this on board compressed air source will itself be powered.
As to the tesla gas turbine itself as pictured, just because some guy can poorly model something in Solidworks and take a screenshot of it does not make it a viable design, nor does simply claiming "it has a high efficiency!" make it so.
The disc shaped turbine design apparently works on the basis of the boundary layer viscosity. This is a real effect and to say that boundary layers have been studied intensively is like saying that Everest is larger than a grain of sand.
In this sense the turbine works, very much like an automotive plate torque converter with air instead of hydraulic fluid. It may be an "efficient" design (although I have not been able to find any kind of source that gives any source of figures, accurate/reliable comparison or indeed methodology; and it has never been in any single one of my undergraduate or graduate textbooks) but the torque it is capable of producing is minimal due to fluid shear.
Any kind of small deviation in the surface will lead to turbulence which, on the scale of the disc separation will cause a complete destruction of the boundary layer on which this device depends; which makes this an incredibly temperamental device probably only useful for a single speed which is no good for any practical application (apart from any other flaws it has).
Note that I have concentrated solely on the turbine aspect of this - again, I have not been able to find anything remotely approaching a scientific analysis of this concept with applications as a tesla compressor. Simply having a bunch of discs revolving in close proximity does not a compressor make. You might manage to raise the static pressure of the fluid in close proximity to the rotating elements by a few Pascals solely because of the velocity effect, but you will not experience anything like the compression needed to sustain efficient combustion.
In both cases (compressor and turbine) the close spacing of the plates of the devices will paradoxically probably rob them of any claimed "efficiency" due to their very model of operation (fluid shear) and the boundary layer drag that results. This will also severely limit the mass flow rate through any such device; which in turn severely limits the practical application.
You are better off looking elsewhere. Even model radio control jet aircraft use a conventional miniature centrifugal compressor wheel taken out of a super/turbocharger; with an two-stage axial turbine to provide power.


Do steam-gauge VSIs compensate for altitude?

Yes.  It appears to be the case for "steam gauges".  At least for a traditional vertical speed indicator.  It's a great question and not one I had considered before.  At first glance, I suspected you may be right, though I don't ever remember actually learning that.
To prove the theory, one pilot apparently took his airplane with a traditional steam gauge altimeter/VSI up to FL220 and found the following:

=>Your altimeter is perfectly accurate at the airport if you enter your barometric pressure correctly.
=>At the cruise altitude of about 8,500 feet or so, your altimeter is off by about FIVE-HUNDRED FEET.
=>At that altitude, it does not matter much that your altimeter is off, because everyone else’s is off by the same amount, and you are far from the airport, and thus landing.
=>The error always seems to be off in the safe direction: You are always HIGHER than you think. Clearly, when they designed the system in 50’s, they designed the altimeters to follow the most conservative lapse-rate we could encounter, so in real-world flying, we are almost-always much HIGHER than we thought, which must be the safest error we can make.
=>The vertical speed indicator perfectly tracks the PRESSURE-based altimeter, not the true altitude, so the vertical speed indicator can be perfectly used to see how much the altimeter will change over time, the ACTUAL climb or descent rate of the plane is actually considerably DIFFERENT… at high altitudes, by 1,290 parts in 24,000, or just OVER FIVE PERCENT.


In general, what are the RPM ranges/differences between the various compression stages on a 2 or 3 spool (LP,IP,HP) turbojet/fan engine?

RPM does not generally fluctuate in flight, or on the ground for that matter.
For 'fan' RPM, 100% N1, is somewhere between 2000 to 4000.(aka LP stage)
For 'core' RPM, 100% N2, is somewhere between 9000 to 14000.(HP stage)
The 3rd spool (IP stage) RPM would be in between the LP and HP nominally around 7000.
These are ballpark figures.


How can a glider pilot add sport pilot privileges?

The short answer is no. You can get student pilot privileges with only a CFI endorsement for a new Category and Class. You would not have Sport Pilot privileges, though. The regs for Sport Pilot certificate holders would be that you need endorsements from two different CFIs and file an application with the FAA for each Category and Class.

Although 61.303 and 61.321 can be confusing, they both make mention of category and class. A sport cert does not have Cat & Class. For Sport Pilot privileges you have to have a training endorsement from one instructor and a proficiency check endorsement from a second instructor before the FAA will issue you a Cat & Class endorsement.

  61.321 How do I obtain privileges to operate an additional category or class of light-sport aircraft?

  If you hold a sport pilot certificate and seek to operate an additional category or class of light-sport aircraft, you must—

  (a) Receive a logbook endorsement from the authorized instructor who trained you on the applicable aeronautical knowledge areas specified in §61.309 and areas of operation specified in §61.311. The endorsement certifies you have met the aeronautical knowledge and flight proficiency requirements for the additional light-sport aircraft privilege you seek;

  (b) Successfully complete a proficiency check from an authorized instructor other than the instructor who trained you on the aeronautical knowledge areas and areas of operation specified in §§61.309 and 61.311 for the additional light-sport aircraft privilege you seek;

  (c) Complete an application for those privileges on a form and in a manner acceptable to the FAA and present this application to the authorized instructor who conducted the proficiency check specified in paragraph (b) of this section; and

  (d) Receive a logbook endorsement from the instructor who conducted the proficiency check specified in paragraph (b) of this section certifying you are proficient in the applicable areas of operation and aeronautical knowledge areas, and that you are authorized for the additional category and class light-sport aircraft privilege.

Private, Sport, Recreational, Commercial, etc. are all separate certificates. You can have multiple category and class ratings on each. If you have a Private certificate already, you will not need to get another certificate for any further non-commercial privileges. All you need to add a different Category or Class is an endorsement showing appropriate training and a Checkride. You will retain Private Privelages for any Category and Class listed on your certificate. Glider is a separate Category to any powered aircraft.

  61.63 Additional aircraft ratings (other than for ratings at the airline transport pilot certification level).

  (a) General. For an additional aircraft rating on a pilot certificate, other than for an airline transport pilot certificate, a person must meet the requirements of this section appropriate to the additional aircraft rating sought.

  (b) Additional aircraft category rating. A person who applies to add a category rating to a pilot certificate:

  (1) Must complete the training and have the applicable aeronautical experience.

  (2) Must have a logbook or training record endorsement from an authorized instructor attesting that the person was found competent in the appropriate aeronautical knowledge areas and proficient in the appropriate areas of operation.

  (3) Must pass the practical test.

  (4) Need not take an additional knowledge test, provided the applicant holds an airplane, rotorcraft, powered-lift, weight-shift-control aircraft, powered parachute, or airship rating at that pilot certificate level.

  (c) Additional aircraft class rating. A person who applies for an additional class rating on a pilot certificate:

  (1) Must have a logbook or training record endorsement from an authorized instructor attesting that the person was found competent in the appropriate aeronautical knowledge areas and proficient in the appropriate areas of operation.

  (2) Must pass the practical test.

  (3) Need not meet the specified training time requirements prescribed by this part that apply to the pilot certificate for the aircraft class rating sought; unless, the person only holds a lighter-than-air category rating with a balloon class rating and is seeking an airship class rating, then that person must receive the specified training time requirements and possess the appropriate aeronautical experience.

  (4) Need not take an additional knowledge test, provided the applicant holds an airplane, rotorcraft, powered-lift, weight-shift-control aircraft, powered parachute, or airship rating at that pilot certificate level.

For instance, I have a Private Cert for Airplane Single Engine Land. I also have Rotorcraft Helicopter hours. I can not solo a helicopter without an endorsement from my instructor. Essentially, giving me Student Pilot privileges for helicopters without a student pilot license (minus the Class B restriction). I would need a Checkride to add Rotorcraft Helicopter to my Private Cert.


What does the German AZF radio license test comprise of in the oral examination?

There are a lot of differences in the US and European communication.

I got my AZF about a year ago and basically you have to do simulated IFR departure and approach. In addition you will have to fill out an IFR flightplan and answer 30 IFR communication questions.

I would say it is a similar difficulty like the BZF, it might be even a little bit easier, as you just have to repeat what the controller tells you (but you still have to be aware where you are).

An example on how radio communication is done can be found at http://www.caa.co.uk/docs/33/CAP413Supplement.pdf or http://training.ivao.de/trainingsunterlagen.html?tx_drwiki_pi1%5Bkeyword%5D=IFR-Funkbeispiel

I would however recommend a training at a flight school (which costs around 150 Euros).


Tracking freighter and charter planes between two specified airports

If you know the tail numbers of the aircraft, you can go to FlightAware.Com and request flight history there. Even if they have not filed flight plans (highly unlikely if they are commercial flights), if they are equipped with ADS-B the odds are high they will be picked up by the system at some point during their flight.


What are the scale effects of GA wing tip airfoils?

If you only look at the airfoils in isolation, the shorter tip airfoil will stall at a slightly lower angle of attack and lift coefficient (I use angle of attack instead of speed, as both should be equivalent). It has only half the Reynolds number of the root airfoil and, therefore, viscosity forces are twice as big relative to inertial forces. This is made worse by the ailerons on the outer wing: A downward deflection will strain the boundary layer more, moving stall to even lower angles of attack.

The exact difference depends on the airfoil. Below I pasted Figure 18 from chapter 4 of Sighard Hoerner's book Fluid Dynamic Drag. Your wing has a chord of 6 ft at the root and 3 ft at the tip, corresponding to a Reynolds number of 3.25 Million at the root and half as much at the tip at 50 kts speed. Note the logarithmic scale of the X axis below: The 2 million point is halfway between the 1 million and the 10 million point.

But there is more: With a 50% tapered and untwisted wing the highest loading is at maybe 60% of span - that is where the full wing will stall first. Next, you have to assume a fuselage at the root. Depending on the local pressure distribution, the root might even begin to stall earlier. You sure know comparisons like the one below for the lift distribution and stall behavior of different planforms (source). Yours is case C (moderate taper):

My recommendation is clearly against the proposed planform. Combined with aileron loads, it will be very prone to tip stalls. Given the "right" airfoil, it will show positive roll damping, that is, it will roll all by itself once the stall starts on one side. There are several steps to make the wing more benign:

Use a thinner airfoil (10%-12%) at the tip than at the root (here 15%-17% are a good choice). Why that helps is shown in Figure 23 below, again taken from chapter 4 of Sighard Hoerner's book Fluid Dynamic Drag.
Use less taper. 70% tip chord relative to root chord gives the best value for induced drag and leaves more margin against tip stalls.
Use an airfoil with benign stall characteristics. Definitely avoid 5-digit NACA airfoils.
Use at least 2° of washout. That sounds little, but has a profound impact on stall behavior.

  Q2) What would the stall characteristics be (root vs tip) if we scaled the tip chord 50% but did not change the thickness?

You mean the same absolute thickness, so the tip airfoil has twice the relative thickness than the root airfoil? This would guarantee very poor stall behavior and is clearly a poor layout. While the root will benefit from a thicker airfoil (lighter spar, more internal space for landing gear and fuel), the tip enjoys no such benefit. Fuel near the tips is more often a liability (roll inertia, tank internal pressure in spins). Manufacturing a spar with a single taper is only marginally more complicated than a spar of constant thickness. The flanges need to be tapered in both cases - this creates the most work.

In order to have the highest margin for aileron deflection, the recommended tip thickness is 10% - 12%, not more. Many designs even used a 9% tip airfoil successfully. Also, the use of differential aileron deflection is highly recommended. Let the trailing-edge-down movement of the aileron be only half as much than the trailing-edge-up movement. This will improve stall resistance and help to reduce aileron forces, especially at high angle of attack.

My favorite example for a poor wing layout is the Dornier Seastar. It was designed more than 40 years ago by a bunch of old Dornier engineers who basically repeated what they had done on the Dornier 17 another 40 years earlier. While the first prototype inherited a rectangular wing from the Do-28, the "new" wing design used a NACA 23015, no washout and had a taper ratio of 0.7. During an early test flight, the airplane flipped on its back during low speed trials. Fortunately, this happened with enough distance to the ground so this upset could quickly be corrected, but it necessitated the addition of a drooped nose on the outer wing.

Now look at the Beech Bonanza: Same planform and very similar root airfoil (NACA23016.5), but a NACA 23012 at the tip and 3° of washout. And much better low speed characteristics. Usage of a NACA 6-digit airfoil would improve those further, see the Piper Cherokee for example.


What clues would have indicated KAL 902 was off course?

According to the German Wikipedia the 707 has been equipped with LORAN-C and VOR. It most likely also had (at least one)
Gyroscopic Heading Indicator.

Wikipedia does not tell something about this concrete plane but these devices where available since the 1950s and there is no reason why this particular plane should not have them.

So from a technical point of view the crew should have been able to detect the deviation from the planned path, given that they had some training in using all of that equipment, and that not all of them broke altogether during the flight (before the rocket hit).


Do the DO-178 standards include guidelines on cyclomatic complexity?

Short answer is No.

From the note after 5.2.2.g

  The current state of software engineering does not permit a quantitative
  correlation between complexity and the attainment of system safety objectives.
  While no objective guidance can be provided, the software design process should
  avoid introducing complexity because as the complexity of software increases, it
  becomes more difficult to verify the design and to show that the safety-related
  requirements are satisfied.

DO-178C is focused on defining process objectives rather than design guidelines.  Your process (specifically Design Standards) might specify a certain maximum complexity value, but it wouldn't be driven directly from DO-178C


What's this part on the wing of BAE Systems Avro 146-RJ100?

They appear to be "Stall Strips" and are used to trigger a "premature" flow separation of the section of area of wing affected, that is, stall that section, before the rest of the wing gets to its natural stalling angle of attack.
Usually you see them near the wing roots but for some reason BAE saw fit to put them a little farther outboard, possibly to mitigate an excessive pitching moment if the wing was stalled at the root (due to the wing sweep which would cause the overall center of lift to shift aft when lift is removed from the root), or, possibly to the get the turbulence induced by the tripped zone away from the horizontal tail where it could cause a fair amount of vibration (they do appear to be placed to put their wake just clear of the tail surfaces).
Stall strips are one of the most "painless" of engineering band-aid mods to cure some kind of unpleasant stall behaviour, or other low speed behaviour, found during testing. At normal AOA's, the strip is in the leading edge stagnation zone (the point where the flow splits to go above or below), so there is little to no drag penalty, and all you are giving up is a bit of the potential maximum lift the wing can make, since you are taking out part of the wing's lift a bit before it normally would.
Stall strips are very effective at transforming light aircraft with very bad natural stall behaviour (sudden, without or with little warning) into very docile machines that can be flown around will full aft elevator just bobbing and shaking, all because the flow was tripped prematurely at that spot and which partially unloaded the tail, preventing further increase in AOA.  Sometimes they are just used to create the turbulence itself that impinges on the tail, just enough to create vibration that can be felt through the stick.


How heavy are the Boeing 747 landing gear?

It seems I misspoke in my comment in which I gave the moments for 747-400BCF gear retraction. I didn't realize the component weights were further on in the document I referenced. The weights for the BCF are:

body gear 6447 lbs (2924 kg) each

wing gear 6508 lbs (2952 kg) each

nose gear 3157 lbs (1432 kg)

However, @Gurkan's comment is relevant in that you have to decide what all should be considered as part of the gear. So, I put up a PDF of the WEIGHT AND BALANCE CONTROL AND LOADING MANUAL for each of two 747 freighter variants. You can access them at terryliittschwager.com/wbmanuals.php. The most relevant sections are 1-86-041 and 051.


How does the power requirement change when weight and speed change?

Short answer: No. $ P = F \cdot v$ and since $ D = \frac{1}{2}C_D\rho v^2S $ it follows that $P\propto v^3$

Let's take a more simple case: a block moves over a rough, horizontal surface in a vacuum and a force is applied such that its velocity $v$ stays constant. This force is always the same, since the "drag force" is given by the friction coefficient times the normal force. Here, the kind of relationship that you're thinking of would hold: if we're moving at $2v$, we need twice as much power ($P=F\cdot v$).

Look at a fixed distance along that trajectory: we do the same work in both cases ($v$ and $2v$), so we put in the same energy which dissipates through friction, i.e. heat. However, we now need to do the same work in half the time, so the power is double. In a certain way, it's "more difficult".

Now for an aircraft, the drag force itself is proportional to the square of the velocity. So, in conclusion, there are "two effects" which "add up": a quadrupling related to the increased force and a doubling due to the increase in velocity. Hence, the power is multiplied by 8.

Edit (in response to comments below):

Ok, let's do another thought experiment: we place a jet engine in a wind tunnel and keep it at constant thrust and constant mass flow (choked nozzle), which results in a constant velocity increment across the engine. The power contained in the jet (the airflow exiting the engine at higher speed $v_j$) is $\frac{1}{2} \dot m v_j^2$  and the power contained in the incoming flow is $\frac{1}{2} \dot m v_0^2$. The difference between the two is called the "propulsive jet power"; it's the power which is "available" from the acceleration of the flow. Now, you can see that because both terms are squared, it is not just the velocity increment which counts (as it was the case for the thrust), but also the magnitude of the two terms.

So alternatively to the "thrust power" given by
$$P_{thrust} = \dot m (v_j-v_0) v_0 = T v_0 = D v_0$$

we can also consider the "propulsive jet power"

$$P_{prop} = \frac{1}{2} \dot m (v_j^2-v_0^2)$$

where the proportionality to $v_0$ at constant thrust is maybe more clear. The difference between these two quantities is called the power loss ($P_{loss}=\frac{1}{2} \dot m (v_j-v_0)^2$) and is a measure of how much of the orginal chemical energy contained in the fuel is lost to kinetic energy in the jet.

You can see that if the velocity differential is constant, the power loss is constant. So if we have shown that the propulsive jet power is proportional to $v_0$ at constant thrust, the thrust power (which is the power that "actually moves you") must also be proportional in this way. And this proportionality is related to the fact that the kinetic energy of a mass is proportional to the square of its velocity.


Where exactly is the 700 and 1200 foot AGL for class E airspace measured from?

So where is it measured from
Well, quite literally the 700 foot and 1200 foot numbers are AGL as in the distance between your aircraft and the ground at any point. If there is a mountain in the transition area, the 700-foot AGL figure would have a mountain-shaped "bump" in it. It does not take the AGL figure from some highest figure in the area.

The number you refer to, the Maximum Elevation Figure, is calculated based on the highest obstacle in the quadrangle, see the FAA Website chart legend:

So as you can see, the blue number in the quadrangle does not show the MSL of the "sector" (quadrangle), but it is a simple calculation based on the height of the highest obstacle in the quadrangle + 100 feet and some rounding.
The FAA does a similar calculation for natural terrain features:

The big take-away here, in reference to your answer on another question, is that you cannot use this number to determine if you are within Class-G airspace since it takes an elevation figure from some obstacle (man-made or natural) that may not be anywhere near you. So flying at the MEF + 1200 feet does not mean you are in Class-G since, as in the second example, that mountain is a long way away from Ute Park or Red river (at Red River you would be more like 6200 feet AGL).
The AGL of the highest man-made obstacles are shown on the chart underneath the MSL elevation:

But it may be omitted in congested areas of the map and only shown as MSL.


How does ATC radar/ADS-B ground stations not get confused with signals sent from multiple aircraft?

The class of ATC radars that you are talking about is secondary radar.

Secondary radar works by transmitting an interrogation signal on 1030 MHz to which the transponder replies on 1090MHz. There are several modes of interrogation. For civil ATC, modes A,C and S are important.

The uplink signal (interrogation) is a simple pulse encoding (Mode A/C) or a Differential Phase Shift Key modulation (Mode S / TCAS) on 1030 MHz.

The downlink signal (replies, unsolicited squiters) is a simple pulse encoding (Mode A/C) or Pulse Position Modulation (Mode S / TCAS / ADS-B)

Originally only Mode A & C were available. Mode A and Mode C are unaddressed; every transponder receiving a Mode A or Mode C interrogation will reply*. This causes two problems,  garbling and FRUIT.

Garbling is caused by the overlap of replies from multiple transponders. A transponder replies on 1090 MHz in the from of a number of pulses. For Mode A & C, there are at most 12 pulses between a set of framing pulses. When multiple aircraft reply to the same interrogation, these pulses mix up and it becomes difficult to find out which transponder sent which pulse. This leads to false altitudes or false squawk codes.

FRUIT (False Replies Unsynchronised to Interrogator Transmission) is caused by replies that are triggered by other radars. When multiple radars operate in an area, transponders can be quite busy and the radar is easily mislead by a reply to another radar. In addition to the timing (range) being wrong, the reply can be Mode A (squawk code) while the radar interrogated Mode C (altitude). There is no way to see what kind (A or C) reply was sent.

To overcome these problems of Mode A/C, Mode S was introduced. Mode S is quite different from Mode A/C and requires a more sophisticated radar and transponder.

Most Mode S interrogations are addressed; the interrogation contains the unique 24 bit address of the aircraft it is interrogating. This reduces the probability of garbling since other aircraft will not reply
Unaddressed Mode S interrogations will solicit replies that contain the address of interrogator (radar). This prevents FRUIT since the radar can verify that the reply is correctly addressed.
Unlike Mode A/C which does not have any error checking, a Mode S reply contains a 24 bit CRC check code.
Mode S Altitude and identity (squawk) replies have their own identifier so they can be distinguished.
Mode S radars can be operated in clusters and coordinate between them  who is interrogating which aircraft at which time. This further reduces the message load and garbling / fruit probability.

Despite all the enhancements,  Mode S radars are still receiving garbled messages and FRUIT, but are much better equipped to cope with it than a Mode A/C radar due to the addressing and CRC checks.

Since TCAS works on the same frequency as secondary radar, radars will occasionally receive TCAS messages as well. But since these have another downlink format (DF 0, DF 16) they are ignored. The same holds for ADS-B (DF 17 / 18)

Garbling remains a concern. Modern Mode S radars are relatively resilient against garbling due to their narrow beamwidth and advanced degarbling processors. But other systems like TCAS, ADS-B in and Wide Area Multilateration systems with their omnidirectional antennas receive overlapping messages quite often. But when the signal strength of the messages differs the messages can be often untangled with modern digital signal processors.

In the Mode S (& TCAS) a reply can be either short (56 bit) or long (112) bit. ADS-B messages are 112 bit long. Every bits takes  1μs, and there is a preamble that takes 8μs. So a message takes either 64μs or 120μs.

Every second, a Mode S transponder sends 1 unsolicited short squitter, and at most 6.2 long squitters when ADS-B equipped.

*To reduce number of Mode A/C replies, Mode S radars will include an extra pulse when interrogating in Mode A or C, so that Mode S capable transponders will not reply to these A/C interrogations.


Are the panels in this vertical stabilizer part of the flight controls?

The part I have outlined below is the rudder. That is the only control surface on the vertical stabilizer.

The segments on the leading edge are just the leading edge surfaces. One may include an antenna, but they are only segmented for easier manufacturing and assembly.

The ones just forward of the rudder are panels that cover the rudder attachment and actuating systems. They can be removed for inspection or maintenance purposes.

The rest of the surface, in the middle, is the main structure of the vertical stabilizer. There is a spar on the forward and aft sides, and ribs that run between them. This is all covered by one piece of skin. This creates a structure that is both strong and light weight.

Below is a cutaway showing the internal structure.


This can be sensed by means of either an INS or GPS to determine a ground velocity and both the data from the pitot static system and a magnetometer to determine the true air velocity.  The local wind velocity is the difference between the ground velocity and the true air velocity.


What is flight inspection, as provided by Cobham Aviation Services?

From their website,

  Cobham conducts commissioning, return-to-service, engineering and
  periodic flight inspections in addition to trials work on a range of
  systems including, CAT I/II/III ILS, MLS, PAR, DVOR, NDB, U/VDF,
  TACAN, DME, AGL and PAPI and PSR/SSR.

  The specialist capabilities include procedure validation, ADS-B and
  MLAT-systems, ship borne navaids, FI programme management, technical
  investigations, communication tests and trials, windfarm trials,
  flight inspection advice, and training.

  Cobham has formal approvals from UK CAA Safety Regulation Group (CAP
  670), UK MoD, INAC (Portugal), ENAV (Italy), British Standards
  Institute (BS EN ISO 9001:2008), Germany BAF, and Air Safety Support
  International OTAR for UK Overseas Territories.

It looks like they test airport/en-route equipment such as approach systems and ADS-B systems etc. This can presumably be done in any aircraft equipped to fly/test those approaches and systems.


The short answer is: No. One cannot calculate the inlet mass-flow based on the velocity alone. However in order to "know" the velocity ( $v$ ) you most likely would have measured everything you need (see below).

Your confusion with regards to the in- and outlet mass-flow might be based on the fact that the intake does not "collect" all air upstream depending of the flight-velocity.

The key is not to think of the geometric area of the intake but the area of stream tube around the air entering the intake.

The velocity upstream of the intake is not equal to the air-speed (subsonic flight) because the potential field of the intake decelerates (or accelerates) the flow upstream of the intake and expands (or contracts) the stream tube (from Wikipedia):

In order to calculate the mass-flow we need to determine the speed and the properties of the air.(please observe that the air-speed ( $u$ ) at the intake is not equal the free-stream-spped ( $v$ ) )

Usually the measured properties are:

Total Pressure, $p_\mathrm{t}$ (Pitot Tube)
Static Pressure, $p_\mathrm{s}$ (Static Pressure Port)
Total Temperauter, $T_\mathrm{t}$ (info, examples)
Relative Humidity, $\varphi$ (for simplicity not used below. Humidity changes the heat capacity)

The following equations are used to calculate the mass-flow ( $\dot{m}$ ). Simplifications are commonly made for slow speeds unnecessarily excepting a 5% error. The following approach does not use these simplifications.

The equation which needs to be solved in the end is:

$\dot{m} = A \cdot \rho \cdot u$

Neglecting blockage effects and non-uniformities, the density ( $\rho$ ) and the velocity at the inlet ( $u$ ) are unknown and need to be derived from the measured values.

First the Mach-Number is calculated by solving the following equation (see Nasa) for the Mach-Number, $M$:

$\frac{p_\mathrm{s}}{p_\mathrm{t}} = \left( 1 + \frac{\gamma - 1}{2} M^2\right)^{\frac{\gamma}{\gamma-1}}$

Here $\gamma$ is the isentropic coefficient which is around $1.4$ for air depending on the humidity.

Second, with the Mach-Number, $M$, we can use another isentropic relation to calculate the static temperature, $T_\mathrm{s}$:

$\frac{T_\mathrm{s}}{T_\mathrm{t}} = \left( 1 + \frac{\gamma - 1}{2} M^2\right)^{-1}$

Third, using the ideal gas law the density ( $\rho$ ) can be calculated:

$\rho = \frac{p_\mathrm{s}}{RT_\mathrm{s}}$

Here $R$ is the Specific Gas Constant.

Forth, using the equation for speed of sound, $a$

$a = \sqrt{\gamma R T_\mathrm{s}}$

Finally Fifth, utilising the definition of the Mach-Number, $M$, the air-speed ( $u$ ) can be calculated:

$M = \frac{u}{a}$

Now all missing values are available to compute the mass-flow.
This approach can easily expanded to cover humid air by adjusting $R$ and $\gamma$ with respect to the relative humidity.

As mentioned in other answers: The inlfuence of non-uniformity of the flow caused by boundary layers or inlet distortions (e.g. inlet-ducting) need to be corrected using a calibration.


Is possible to do a private pilot license training and check-ride on a Light Sport Aircraft?

The answer is yes. The regulations make no reference to the TYPE of aircraft. Just to the Category and Class. You will need to have at least 3 hours of dual instruction under actual or simulated instrument conditions, flying solely by reference to instruments. As long as this can be done in the particular LSA you are flying, or you achieve it in a different aircraft, it counts.

LSA is neither a Category nor is it a Class of aircraft.

You will have to get a type rating to fly passengers (even not for compensation or hire) if one is required for that aircraft.


There are essentially two scenarios on departure: an initial vector, or flying the departure procedure track immediately "off the ground."

In the former case, the instructions might be along the lines of, "fly heading 120, expect vectors to JEBBB" or "... to join the WHOZT5 departure."  In that case, shortly after takeoff, the pilot would select Heading mode and fly the specified heading.  At some point after that, ATC would issue a clearance to proceed direct to a fix, and then the filed route would be flown from that point on.  So upon receiving this clearance, the pilot would proceed direct to the given waypoint by engaging NAV (or, given modern nomenclature, LNAV).

In the other case, the first leg of the departure corresponds to the "straight ahead" track of the departure runway, and LNAV is activated immediately after departure, and the aircraft will fly the magenta line as published.  So in this case, Heading mode isn't used, unless ATC needs to vector the aircraft off of the published track.  In that case, they can either issue a vector, or they can clear the aircraft to a later point in the procedure or along the route.

In modern ATC, it is very uncommon for an aircraft to be getting vectors enroute, simply because it is more workload for the controller with no benefit.  Once you're away from the terminal area, they clear you on whatever route you've filed (or been assigned), and they don't have to do any more navigating for you.  If they need to turn you off course for traffic, they will, but that's the exception, not the norm.


Does the Enroute Phase begin at a 30NM distance from the departure airport?

You are not getting anything wrong, I think you are simply overthinking something that isn’t actually important.  The 30nm distinction is somewhat arbitrary, and presumably captures most arrival and departure procedures.  There is nothing magical or binding in this number, and there is nothing pilots will do differently when flying a published route or procedure based on distance or phase of flight.

For example, let’s say the last point on a published departure procedure is less than 30nm from your departure airfield, and the next point on your filed route of flight is outside of 30nm.  Your question implies that there would be confusion as to whether you would be in the terminal phase or the enroute phase of flight as you flew between these two waypoints, is that basically correct?  My point is that this distinction does not matter.  You will not fly the aircraft any differently if it is one or the other, you will simply navigate to the next point on your route while climbing or maintain assigned altitude.

Now there are some things that are accomplished during arrival and departure phases that may be worth discussing to clarify things and satisfy your curiosity on the subject.  However, most of them are done as a result of passing a certain altitude.  For example, at a certain altitude during climb out power may be adjusted for noise abatement and efficiency.  Passing through 18,000 feet altimeters will be adjusted to 29.92 and perhaps switched into a different mode.  This will be captured as part of a climb checklist.  Reaching cruise altitude another checklist will be accomplish that will include things like adjusting cruise power, checking cabin pressurization, etc.

Preparing for arrival similar descent and approach checklists are executed that will include obtaining weather and local altimeter setting, approach briefing, etc.  Passing 18,000 on the descent altimeters will be set to local setting, passing 10,000 speed will need to be slowed to 250KIAS.  Checklists can be triggered by either altitude or distance from the destination, but again the distinction between exiting the enroute phase and entering the terminal phase is not really that important.  The thing that matters is understanding when you are established on the published procedure you have been cleared for.  The actual distance from the airport where this actually occurs is of no real concern as long as you fly what you are cleared for.

If IFR there will also be a hand off at some point between the Air Route Traffic Control Center and the local approach controller, but this will likely be tied to altitude as well.  Also, you may be handed from one approach controller to another, but this will occur as you cross sector boundaries and is based more in geographic radar coverage and not a concentric range ring from the airport.

Finally, most modern GPS navigation systems will automatically change the sensitivity of the course deviation indicator in different phases of flight with the least sensitivity in enroute phase, more in terminal, and greater yet in approach phase.  (This is basically what the section you quoted above is referring to)  However, they will cycle as the aircraft passes the first or last waypoint of a procedure that is loaded into the system and not at some distance in between.  In other words, if you are navigating to the first point of a STAR or instrument approach the system ought to retain enroute CDI sensitivity until this point is reached.  The upon passing the waypoint it will cycle to the greater sensitivity of the terminal or approach phase.  For this reason is it important to understand what phase of flight your GPS considers you to be in, but know that it will not cycle at 30nm or any other arbitrary distance in between, but at the waypoint where the transition occurs.

To reiterate, there isn’t a specific checklist or different way of flying related to the transition between terminal and enroute phase of flight, nor is there any such thing as a “no man’s land” in between phases if a point on a SID or STAR is within or outside of the 30nm distance referenced in your question.