Why is the nose cone of Russian fighters pointing slightly down?

The nose cone position depends upon the mission profile of the aircraft. Su-30 is a multirole fighter for all-weather, air-to-air and air-to-surface deep interdiction missions, since its air-surface with deep interdiction it needs to have a view of the ground while targeting ground troops/equipments/artillery. This nose down config helps it to have that view. F-18/F-16/F-15 are air superiority aircrafts. Yes same cannot be said for F-18 but then F-18 has many variants, F-18D which has air-ground support is slightly elevated pilot view for better ground view. Same can be seen in Eurofighter Typhoon and A-10 Thunderbolt.
While Su-15, Su-24 and Mig-27 where interceptors and bombers, they have straight nose just like their companions from the west.


Why do super sonic fighter jets have narrow waist?

It is likely due to application of the Area rule, which helps to reduce drag due to shock waves in transonic and supersonic flight.

It basically is an attempt to keep the cross-sectional area of the craft from varying rapidly as you move along the length.  So at a point where the wings area is increasing a lot, the area of the fuselage may be reduced to compensate.

This reduction of area is mainly intended when these airplanes fly at transonic speeds (0.8-1.2) but not when flying at supersonice speeds where a front shock wave is created.


Can a commerical jet fly into a tropical cyclone?

If the wind shear (sometimes called wind gradient, which in my opinion is the better term) encountered in that part of the cyclone the aircraft is penetrating is less than what the aircraft can handle, then, yes, an aircraft can safely fly into a cyclone.

What the aircraft can handle varies greatly depending on the speed at which it is being flown. Large aircraft have a recommended turbulence penetration speed, both in terms of knots and mach. In the absence of such a recommendation, V speeds that are relevant are Va, Vb, and Vo. http://en.wikipedia.org/wiki/V_speeds is a good V speed terminology reference.

I do not know what typical wind gradient values within a cyclone are or what their distribution within the cyclonic area is. However, I would be surprised if they were significantly greater than gradients within tropical thunderstorms, and aircraft do penetrate such.

In season there's a roughly north-south line of thunderstorms that regularly develops between Sumatra and Sri Lanka with tops greater than 50,000 feet. Lacking the fuel to go around the line, we would regularly go through it using radar to avoid the worst. However, with those old radars (back in the 1990s in 747s), it was not uncommon for us to wind up in a cell.


Instrument Approaches which do not have a FAF

The Lakeland approach you show does not have a FAF (Final Approach Fix) because there is no defined point (fix), where you are established inbound and start to descend. In this case, the FAF is given by the FAP (Final Approach Point):

FINAL APPROACH POINT− The point, applicable
only to a nonprecision approach with no depicted
FAF (such as an on airport VOR), where the aircraft
is established inbound on the final approach course
from the procedure turn and where the final approach
descent may be commenced. The FAP serves as the
FAF and identifies the beginning of the final
approach segment.

(FAA Pilot/Controller Glossary)
The chart only says "Remain within 10 NM", so the actual FAP depends on how you fly and cannot be depicted on the chart. Note that the approach does not require DME, so the point AMBAZ cannot be identified by every aircraft (which is why the chart lists minima with and without AMBAZ). It therefore cannot be the FAF. The second approach you show (Savannah) requires DME or TACAN, which means it can have a FAF (FREMN) defined via DME (SAV 7.8).
The MAP (Missed Approach Point) of the Lakeland approach is the LAL VORTAC, which is also the IAF (Initial Approach Fix). The Jeppesen chart for this approach explicitly says "MAP at VOR" and the FAA chart you show has the MAP indication (dotted line with upwards arrow) at the LAL VORTAC.

The Jeppesen chart also shows a point FF27 5.7NM before the runway, where a CDFA (continuous descent final approach) at 2.96° should be started, which is probably the point an FMS would use:


The bypass air is accelerated by the fan at the front of the turbofan engine. This changes its velocity and therefore its momentum, which is the definition of a force (in this case: thrust):

$$ F = \frac{\text{d}}{\text{d}t} p = m \frac{\text{d}}{\text{d}t} v = m \cdot a $$

This thrust contributes to the total thrust of the engine. How much will depend on the bypass ratio of the engine and other parameters, but 80% is plausible for a high bypass turbofan. Bernoulli's principle has nothing to do with this.

You can see the accelerated airflow in the following animation:

(source: Wikimedia)

The air coming from the engine core will move even faster, but there is less of it in a high bypass turbofan resulting in less total thrust coming from the core:

  The fan airflow, referred to as the cold air stream, is accelerated by the fan and passes through the engine remaining outside of the engine core. The cold air stream moves much slower than the hot stream gas flow passing through the engine core.

(skybrary.aero)


How to identify shock waves and expansion waves on a representation of the mach number?

Your airfoil is traveling supersonic at around Mach 2.

First the flow encounters a bow shock. Away from the leading edge, the bow shock morphs into an oblique shock. You can clearly see Mach number rapidly decreasing after the shock.
After passing through the thickest point of the airfoil, the expansion wave begins due to gradually increasing expansion angle. You can see Mach increasing, all the way up to around Mach 2.2.
At the trailing edge, the flow encounters a compression angle if you consider the wake as a boundary. Here, an oblique shock is encountered. Since oblique shock is less powerful than a normal shock, you can clearly see that Mach isn't decreasing as much as after the bow.


Why would METARs and ATIS both report exactly the same wind direction?

For the US
From the FAA ATC manual:

2−9−3. CONTENT

NOTE− [...] The ASOS Operator Interface Device (OID) displays the magnetic wind as “MAG WND” in the auxiliary data location in the lower left−hand portion of the screen. Other OID displayed winds are true and are not to be used for operational purposes.

Which confirms the ATIS winds are magnetic.
I just listened to KCMA ATIS, the wind reported is 10 degrees more than the METAR.
Make sure you match the ATIS and METAR times. On liveatc.net they were not the same, I had to check the METAR from aviationweather.gov to get the correct reporting time.

For Europe
It's not the same.
Both METAR and ATIS report mean wind information, for the direction, both report in true heading. ATC report is magnetic.

ATIS wind velocity is latest two minute average. The wind direction broadcast is given in degrees true.
[...]
ATC plain language ad hoc wind directions given during final approach or just prior to or during the take off roll are likely to be given in degrees magnetic.
— skybrary.aero


How is the Angle of Attack influenced in the slipstream of a propeller?

Not all planes have propellers and not all of the wing is behind the propeller.

In fact only a small part of the wing is behind the propeller. The rest will get clean air depending on the attitude (orientation) of the aircraft. The wing is also not perfectly straight behind the propeller either, usually dropping down a bit so there is a positive angle of attack.

Jet powered planes generally have their engines away from the wings.

In most planes, thrust is surprisingly small compared to the weight, an empty A380 only has a thrust to weight ratio of 0.47 and most of that thrust will be applied horizontally. So as the plane will sink rapidly should there be no lift from the wings. That sink tendency is what provides the angle of attack.

This will max out the sink rate should the wings be level, angle them up a bit and the plane will try to climb.


Where is the pitot static drain located on a Piper PA-28?

This presentation gives a nice overview of various systems on the Piper Cherokee series. The buttons you describe are shown here:

(slide 9)

The full pitot-static tube including the drain is shown here:

(slide 11)

So the drain is incorporated in into the pitot-static tube itself.

The buttons are also acting as a drain themselves, for details see Alexander's answer.

Related:

What is the difference between a pitot tube and a pitot-static tube?


Are radar bars centered around the horizon or do they move with aircraft pitch?

If i understand your question, you are asking whether the vertical elevation direction of the radar antenna lobe is corrected for when the aircraft is in a pitched up position as compared to a level position. (Whether this correction would be done mechanically in older radars or electronically with AESA radars is secondary)

It probably depends on the particular aircraft and version.
But to my knowledge it is generally not. The antenna will keep its direction within the host aircraft and thus scan a higher altitude volume when the aircraft is pitched up.

Note that the pilot can change the vertical elevation range of the antenna by tilting it up or down manually at any time (if it is not locked on a target) and will probably do so in order to compensate for longer phases of pitch up flight.

As an example, this document is a description of the AN/APG-66 and -68 radar systems of the F-16 Fighting Falcon.
(It is a documentation for a general public simulator game, but you can be confident that it describes the function of the real aircraft very accurately)
See page 11, section "Elevation".
In the case of the F-16, the antenna tilt interface is part of the HOTAS controls, on the throttle:
http://falcon4.wikidot.com/avionics:hotas, see "Antenna Elevation Knob"

When a target is "tracked" or "locked" this is another matter. In that case, the antenna will generally move autonomously in order to keep the target within the center of its detection lobe as long as possible, both vertically and horizontally (azimuth), within what is physically possible taking into account the attitude of the host aircraft versus the target. (See the doc for this also)


What are the lines of triangles on the DCA RWY 19 River Visual approach chart?

So, applying some local knowledge, the Key Bridge is a high arch bridge in that it is a good distance above the water level, and the other ones listed, Rochambeau, Memorial , Roosevelt, and Chain Bridge are all "low" bridges, more like causeways.
I tried looking for a chart legend that said this, but I wasn't able to find one.


Why are both ATC and TCAS tasked to prevent collisions although TCAS takes precedence anyway?

While ATC's primary goal is to prevent collisions, it is also responsible for the efficient movement of aircraft through the airspace. That requires a strategic approach to managing air traffic to get aircraft from point A to point B safely and in a timely manner. The primary tool ATC uses is the flight clearance.

If air crews follow their clearances accurately and VFR traffic maitains adequate visual separation, there won't be any problems with separation being met.

TCAS can't issue a flight clearance. It doesn't know anything more than the traffic it can track via Mode C or Mode S interrogations. It's a tactical system that provides a backup when ATC or the crew makes a mistake and separation is lost. In this case, the TCAS is the automatic backup to resolve the loss of separation and avoid the collision.

The reason a TCAS RA must be followed, taking precedence over ATC, is that when there is a loss of separation immediate action must be taken.


Which external instruments are visible on the A350's nose section?

Here's a better picture showing all probes, and labeled:

Link to original, high-resolution, unnumbered picture

They are:

Ice detector
Multi-function probe 1
Static port
TAT probe
Side-slip vane
Pitot probe
Angle-of-attack vane

Airbus.com has a PDF (pdf page 125) about the various probes.

1
As the name suggests, the multi-function probes record different types of data. Here are more details:

  The piloting of any aircraft involves knowing the relative speed of
  the aircraft with respect to the airflow surrounding it, that is to
  say to the relative wind. This speed is determined with the aid of
  sensors of the static pressure Ps, of the total pressure Pt and of the
  angle of incidence “alpha”. “Alpha” provides the direction of the
  speed vector in a reference system tied to the aircraft and Pt-Ps
  provides the modulus of this vector. The three aerodynamic parameters
  therefore make it is possible to determine the speed vector of an
  airplane.

These are covered by a US Patent.

Someone asked a similar question here.


Is the ground clearance of the B737 engine low compared to similar aircraft?

Is the distance on a B737 engine really that little comparing to other Aircrafts (for example A320)?

The actual distance depends on the engine installed and the weight and balance of the airplane at the time. But there isn't a huge difference between the two planes. Comparing the figures, the current A320 is about 10 cm higher than the current 737 NG. The A320neo and the 737 MAX will be pretty close, with the MAX potentially getting 5 cm lower.

737 (MAX): 43-58 cm (1.42-1.92 ft)
737 (NG): 46-64 cm (1.5-2.08 ft)
737 (CL): 46-53 cm (1.5-1.75 ft)
737 (100/200): 51-58 cm (1.67-1.92 ft)

A320neo: 46-56 cm (1.84 ft)
A320: 57-85 cm (2.2-2.79 ft)

Those reports also show exhaust velocity profiles at takeoff thrust, but differences in the diagrams make it hard to compare. The IAE engines look to have much lower velocities than the CFM engines on either plane.

  Is this a design fault? Also have a look at the "Jet-blast pressure study" page 13-14.

It depends how you look at it. In the linked report, there are several recommendations for both blast pads and the operator's procedures, but nothing regarding the design of the aircraft. So rather than telling the designers to mount their engines higher above the ground, they are making sure that facilities and procedures are designed to prevent things like this from happening.

As far as being a "fault" unique to the 737, the study mentions:

  ...an accident very similar to that of G-DOCT, which involved an Airbus A320...

So it's not the only airplane that can cause problems. And the newest versions of both types will have similar and smaller distances, they probably decided that there is no facilities-related reason important enough to choose differently.


What is the trend of gender distribution among pilots?

At least for the FAA, you can get the U.S. Civil Airmen Statistics as a download that covers from 2005 to 2014. It includes data based on gender and license type. I'm not sure when they will update for 2015. If you download the 2010 one, it has data back to 2001, so about 13 years of data.

Here is an example of the data provided:

Similarly for the UK, you can download statistics from this website. I haven't downloaded them but it looks like what you are looking for is there.

You may be able to find similar data for Canada, Australia, and some other relatively "open" countries.


In an emergency situation just after take off, is fuel dumping useful?

You would not attempt this. Aircraft are certified to climb with engines inoperative after V1, they would just climb to a holding altitude and run the checklist. They would rather not attempt to any cruise altitude. Running the checklist you would determine if you are above the maximum landing weight (MLW) and decide to burn or if able, to dump fuel.

Dumping fuel during the takeoff/rotation phase is not advisable to be honest, as you would leave a contaminated runway behind. Sure, most of the fuel will evaporate, but there will be a contamination nonetheless.

I will quote Nate Eldredge's comment shamelessly for another item to consider:

  According to How is fuel dumped in aircraft? a 747 can dump 6000 pounds of fuel per minute. Given that (from what I found) it typically carries at least 200,000 pounds, and has an MTOW of over 800,000 pounds, it seems unlikely you'd dump enough fuel fast enough to make any difference.


Can I use dual time for the 10 night takeoffs and landings required in 61.129?

No being under the hood does not count as "night flying" see this question for the FAA's definition of night flight.
You dont need to be alone in the aircraft for these TO/LD's while the FAA definition of "solo flight" which this question covers could apply it does state that an instructor can be present

(4) Ten hours of solo flight time in a single engine airplane or 10 hours of flight time performing the duties of pilot in command in a single engine airplane with an authorized instructor on board (either of which may be credited towards the flight time requirement under paragraph (a)(2) of this section), on the areas of operation listed under § 61.127(b)(1) that include -

(ii) 5 hours in night VFR conditions with 10 takeoffs and 10 landings (with each landing involving a flight in the traffic pattern) at an airport with an operating control tower.


Why can't airline pilots listen to music while flying?

I don't know where he gets that.  Regulation wise there's nothing stopping an airline pilot from listening to music as long as he/she can hear ambient sounds or communications and modern headsets make it easy to link an ipod to headphones that are also receiving the comms.

Pilots are allowed to take naps in flight as long as they are awake within 45 min of arrival.  A pilot not flying (PNF), where the autopilot is on and the other pilot is monitoring everything, can be doing paperwork or reading a paper or watching a movie on a tablet or going for a dump or wandering around the cabin if he/she wants.  Once on an arrival however, forget it and certainly not once below 10000 ft.

If there is a prohibition in that Capt's case, it is probably a policy with that airline.


Which ATC instructions should be repeated back by the pilot?

ATC is, broadly speaking, required to ensure that pilots hear, understand, and acknowledge information that is delivered.  The way they do that is via read-backs, and although the AIM mentions a few of the things that are required it's a good idea to read back anything that's important (If you're not sure, err on the side of "It's important"), with your aircraft callsign (No callsign? Doesn't count!).

What are some important things controllers usually expect you to read back?

Clearances (headings, vectors, altitudes, transponder codes, and radio frequencies).
Like the AIM says, mutual verification.
Runway assignments, hold short instructions, line-up-and-wait, and takeoff clearances.
Taxi routes Instructions, ESPECIALLY runway crossings & hold-short instructions.
Wake Turbulence advisories.
Traffic point-outs.
The magic words here, by the by, are "Negative Contact" and "Traffic In Sight".
I think if you say "Tally Ho!" you're required to buy everyone on the frequency a bottle of 30-year-old scotch.
Instructions to "Maintain visual separation with" some traffic
ATC is handing off collision avoidance responsibility to you as the pilot.
They need to hear "Will maintain visual separation with" the traffic in question.
They also need you to tell them if you lose visual contact.
Airport Point-Outs (Especially if there are several airports close to each other)
You can also pre-empt this by calling the controller: "Cessna 12345 has Podunk Municipal in sight", possibly with a bearing and approximate distance.
Landing Clearances
If you're in a busy pattern and they give you a sequence ("Number 3, cleared to land") they want to hear that part too.
That altimeter setting you get after a handoff.
(I blame Don Brown for getting me into this habit, but it IS a good one unless the frequency is crazy)

This list is by no means exhaustive, but it's most of the big stuff.


What can a new commercial pilot do to build flight time?

For a commercial pilot (without a CFI rating) you've got some options, but the real golden goose of time building is flight instructing. Most folks I know who are time-building accumulate the minimum amount of time until they have enough to get the CFI rating, then go out and instruct to get to their end goal (time / types).

Without the CFI rating, some things to look in to include:

Banner Tow (if available in your area)
Crop dusting (again, if available in your area)
Glider towing
Skydiving
The FAA has a page on skydiving operations this that's worth a read.
Ferry Piloting (if you don't mind the travel)
Photo work - anything from costal erosion photos to event coverage depending on your location.
News work - Hand in hand with Photo work, but also traffic and the like.
Sightseeing flights
AOPA has a page on this which is worth a read, take care as you almost certainly want to be sure you fall under Part 91 and not Part 135!
Deliveries.
Someone needs a wedding cake moved across the state? You can often do that in a Cessna more efficiently than they can by car, and as a commercial pilot you can even charge for it.
Corporate Flight Jobs
Sightseeing within 25sm of an airport

There are some outfits that will "sell" you SIC in their cargo twins. It's a way to build TT, but it's considered an unscrupulous practice.

Many of these will probably require the very time you're looking to build, or experience in specific types of aircraft, but it can't hurt to investigate.


Is there any other category of aircraft in the FAA regulations besides 'Ultralight' that does not require pilot licensure?

Yes, there is at least one. This probably was not what you had in mind, but the FAA has been very explicit about the following, for a variety of reasons.

Unmanned aircraft are explicitly regulated as aircraft. However, certain model aircraft require no certificate if operated under the provisions of §101. This is in contrast to all other unmanned aircraft which do require some sort of certificate or exemption, Small Unmanned Aircraft Systems regulated under §107 for example.

The following definition is from 14 CFR 1.1:

  Aircraft means a device that is used or intended to be used for flight in the air.

The following is excerpted from the FAA's FAQ page on Unmanned Aircraft Systems:

  What is an unmanned aircraft system (UAS)?
  An unmanned aircraft system is an unmanned aircraft and the equipment necessary for the safe and efficient operation of that aircraft. An unmanned aircraft is a component of a UAS. It is defined by statute as an aircraft that is operated without the possibility of direct human intervention from within or on the aircraft (Public Law 112-95, Section 331(8)).


How might one fly from KRYN to SDRS in a de Hallivand DHC-6 Twin Otter?

I would recommend that you go to https://skyvector.com/ and create a flight plan.  It isn't too difficult, just click on "Flight Plan" in the top left corner and you should be able to figure out the rest.

You obviously have some familiarity with ICAO airport identifiers, simply look for airports along the way that will keep you under a 886.7 NM leg length, and enter them one by one to build your route.  I would use a cruising speed of around 150KIAS based on a quick Google search of Twin Otter performance.  The website will calculate the times for each leg based on this airspeed.

As far as researching suitable airfields that can provide fuel and other services, that will take quite a bit of additional work.  I don't have a handy reference for you, but you could start by searching for World or Latin American Airport Directories.  I wouldn't expect anyone here to do all that work for you and post it as an answer.  If you have any detailed questions as you go don't be afraid to ask.

Regarding your questions about avoiding immigration authorities, that's up to your fertile imagination to come up with fictional scenarios.  There is no aviation specific way to answer this, and most people would be hesitant to recommend methods to circumvent the law.


What is the ceiling altitude for the Airbus A320?

This question is a bit more generic. Ceiling altitude depends on many things such as (environmental conditions, engines operative, a/c aerodynamic characteristics, e.t.c), each factor by itself and in combination, can affect the ceiling altitude. You can get an idea and some definition from here: https://en.wikipedia.org/wiki/Ceiling_(aeronautics) .

  For most of the A319/A320/A321 aircrafts Maximum Certified
  Altitude according to FCOM is FL391 considering (2 engines operative
  and environmental allowing.)

Now according to FCOM DSC-22_20-50-10-28, (controls and indications) you can find the MCDU page,

REC MAX:
This field displays the recommended maximum altitude (in magenta), that is computed based on the current gross weight and temperature, and assuming that the anti-ice is off (Refer to QRH graphs, if icing conditions are expected). It provides the aircraft with a 0.3 g buffet margin, a minimum rate of climb at MAX CL thrust, and level flight at MAX CRZ thrust. This field is limited to FL 398.
If one engine is out, this field displays the recommended maximum engine-out altitude, that is computed based on the long-range cruise speed and assuming that anti-ice is off.

Note: The OPT or REC MAX field may display a value up to
FL 398. However, the current aircraft’s maximum certified altitude is 39 100 ft. Disregard the OPT or REC MAX value, if it exceeds FL 391.

Now for entertainment system, (again according to the books), reads and display data taken from the FMGC.

One scenario is the input from the pilots, in MCDU was the displayed LVL, and subsequently in the entertainment system, the displayed LVL
was that (after the CRUISE phase), even though the actual altitude was
different that the displayed.But again it's impossible to insert an altitude above the value of "FL398" MCDU says "ENTRY OUT OF RANGE".

  So the conclusion As kevin said already, possibly wrong data were
  displayed.


The concept of lift force per unit span comes from potential flow theory. It will need some background information to explain what it means, so bear with me.

In the early years of flight, electricity was new and exciting, and it just happened that the equations which could calculate the strength of an electromagnetic field worked equally well when calculating the local flow change effected by a wing. What is the electrical current in a wire became the vorticity in a vortex, and the strength and orientation of the induced magnetic field were equivalent to the induced flow changes. So the vocabulary of electricity was copied over to aerodynamics, just like brain research used vocabulary from computer science when that was a hot topic.

Now we are left with abstract concepts like induced drag or lift per unit span. It would be so much more descriptive to use proper names, but the authors of technical books learned it that way and are much too lazy to explain aerodynamics any better.

In potential flow theory, you have sources, sinks and vortices. Sources and sinks are used to generate the displacement effect of a physical body moving through air, and vortices are used to explain why wings bend the flow and create lift. In order to calculate the lift force $L$ of a single vortex in two-dimensional flow, the circulation strength $\Gamma$ of the vortex is multiplied by the airspeed $u_{\infty}$ and air density $\rho$. You will find an equation like $L = -\Gamma\cdot u_{\infty}\cdot\rho$ in many treatises about numerical aerodynamics.

To expand that into the third dimension (and, consequently, into reality), you need to add something measured in spanwise direction - but you have already lift, and adding the third dimension would give a moment (lift times distance) where only lift would make sense. Therefore, this two-dimensional lift is now called "lift per unit of span" so there is still space for a third dimension where two-dimensional flow did already produce lift (counter to any sound intuition).

And no, this is never constant over span. In all cases the vorticity is gradually reduced towards the tips, or explained in a better way, the suction force acting on the wing is gradually reduced when you approach the tips because when the wing ends, nothing can prevent the air from flowing from the high-pressure region below to the low-pressure region on the upper surface of the wing.

While the potential flow mentioned above is the mathematical way of looking at aircraft, lift coefficients are the engineer's way of expressing things. From tests it was soon clear that the lift force of a wing scales with the dynamic pressure $q$ of the flow, that is the product of air density and the square of airspeed: $q = \frac{\rho}{2}\cdot v^2$.

The next observation of engineers was that lift also scales with wing area $S$. To make the lifting force independent of wing size and dynamic pressure, they stripped both from the lift (physical unit of Kilopond, Newton or pound-force) so they arrived at a dimensionless figure which they called lift coefficient $c_L$. Doing so made it much easier to compare measurements or scale up known designs for the next, better design. The lift equation now becomes $L = c_L\cdot S\cdot\frac{\rho}{2}\cdot v^2$


Is there any technical reason that prevents installation of a jet blast deflector at Princess Juliana airport?

An immobile jet blast deflector could not be built far enough away from the runway end to be safely clear of the landing path. Large airplanes like 747s must touch down pretty close to the near end of the runway, which is right at the edge of the  beach, a blast deflector would be a serious hazard if an airplane came in a bit too low. Here's what I'm talking about:

A static deflector would be extremely close to the path of the landing gear.

It could theoretically be possible to install a retractable one, however sand does not make a good building surface and therefore it would be real engineering challenge.

It seems much more likely that the authorities, if they do anything, will install more fencing or other barriers to deter people from getting so close rather than install a blast deflector. This would be cheaper and achieve the same effect.


Are there advantages to slotted wingtips?

Slotted wingtips provide torsional flexibility.

  A bird’s wingtip feathers must twist in one direction during the upstroke of the wings and in the other direction during the downstroke to keep the local wind striking the wing at an appropriate angle to generate lift and thrust... The turning could be done at the base, with a completely inflexible feather; the aerodynamics are improved and material saved if the local flow forces twist the feather by just the right amount.

-- S. Vogel, Comparative biomechanics: life's physical world, p. 382, 2003.

They also reduce drag.

  The minimum drag of a Harris' hawk gliding freely in a wind tunnel was measured before and after removing the slots by clipping the tip feathers. ... the feathers that form the slotted tips reduce induced drag by acting as winglets that make the wings non-planar and spread vorticity both horizontally and vertically.

-- V. Tucker, Drag reduction by wing tip slots in a gliding Harris' hawk, Parabuteo unicinctus, J Exp Biol 198:775-81, 1995.

They are effective while flapping, not just while gliding.

  We used particle image velocimetry to measure the airflow around the slotted wing tip of a jackdaw (Corvus monedula) as well as in its wake during unrestrained flight in a wind tunnel. The separated primary feathers produce individual wakes, confirming a multi-slotted function, in both gliding and flapping flight.

-- KleinHeerenbrink et al, Multi-cored vortices support function of slotted wing tips of birds in gliding and flapping flight, J R Soc Interface 14(130):20170099, 2017.


What happens to Flight Testing Aircraft after Testing is over?

It depends. In most of the cases, the aircraft have been instrumented and pushed so much that it not possible to modify them for commercial flight. In these cases, they are either preserved or continued to be used as test aircraft. In other cases, the aircraft are modified and delivered.

Boeing 747- The first ever Boeing 747 was used exclusively as a test aircraft and was later handed over to museum. On the other hand all the 747-8s were converted back after test flights and delivered to customers.
Boeing 777- The first 777s were considered production models, not prototypes and were delivered to customers after testing.
Boeing 787- It is kind of a mixed bag here- The first three 787s are in museums across the world (two in the US, one in Japan). Boeing is still using one as a testbed, while one more is in storage. Another aircraft used for testing was later modified and sold to the Mexican Air Force.
Airbus A350XWB- Right now, Airbus is holding all the five testing aircraft and using them for testing or demonstration flights.
Airbus A380- Airbus has all the test aircraft.

You can check out the production lists of various aircraft here


What approvals do I need for a helicopter landing?

If you charter a helo, most likely they’ll fly you from KALB to KBVY, then provide you additional ground transportation to and from these airports.  As to landing directly onto school property, that would probably be at the discretion of the school itself; my guess is that they would frown on it unless it was an emergency, as helicopters are a noisy and somewhat dangerous nuisance to have around.


Why is it 'aileron right and elevator up' with a front-right wind in a tailwheel airplane?

The wind could pick up the tail in tailwheel aircraft which is why they recommend elevator up to prevent that scenario.  If the wind is really bad the tail could possibly get higher than the wings and flip the airplane over.  This will not be an issue for tricycle gear aircraft so elevator doesn't matter in this case.  This will be tested on the FAA knowledge exam so you will want to remember this.


How do I determine the engine thrust required to give a specific climb rate?

How do I know that the N1 that I get from the OPT is enough thrust to meet the required climb gradient in feet per minute published on the SID?

You can't, but read on please.
Variables
A few things out of the way first. A percent N1 is not a percentage of the engine's max thrust. 95% N1 at 20°C at sea-level is different from 95% N1 at 35°C at a 4,000 feet MSL airport in terms of thrust force.
Likewise for the lift; airport elevation, temperature, and pressure, also affect the lift. So for the same runway and SID, you'll get different climb rates at a given speed on different days. And since lift counters weight in a steady climb, how heavy you are plays an important role (as well as how the plane is loaded, i.e., center of gravity).
Gradient and OPT
A SID that shows a climb rate, will also show the corresponding ground speed (put together that's a gradient), in fact it will be multiple rates vs. speeds. Climb rate on its own is not a performance parameter. And while an angle of climb (flight path wrt air) does not depend on the wind, the climb gradient (wrt ground) is affected by the wind (yet another variable). Another variable, turns (bank angle) while climbing.
I'm not sure what OPT is, if it is the free Onboard Performance Tool app from Boeing on the App Store, then note that it requires contacting a Boeing representative for the configuration files, etc. If it is an OPT-like software in the sim, then I highly doubt it can calculate the climb rate; even relatively expensive performance calculators for PC flight sims don't go there.
If you have all the variables, you still can't know the gradient or climb rate at a speed. While a real Boeing 737 comes with an AFM or FPPM (manuals that include performance data), climb gradients with all engines operative are typically not included. The FAA AC 120-91 (Airport Obstacle Analysis) discusses this point:

(...) It is recognized that many AFMs generally contain only the one-engine-inoperative performance for loss of an engine at V1 on takeoff. All-engines-operating performance must also be considered to determine the airplane's flightpath in the event of an engine failure at a point on the flightpath after V1. The best available all-engines-operating data should be used consistent with best engineering practices. Operator's may find appropriate acceptable data in various sources, such as: community noise documents, performance engineer's handbooks, flight characteristics manuals, and manufacturers' computer programs.

How is it done?
So what do you do? Unfortunately not much. In the real world a program like the Boeing Climbout Program (BCOP) -- an example of the aforementioned "manufacturers' computer programs" -- is used to analyze each SID individually (this is different from the three or four takeoff limiting weights pilots are accustomed to).
But even then the analysis may not be presented to the pilots. The airline that is operating out of airport x -- your day-to-day typical not-in-a-hot-valley airport -- would have already checked the extremes (temperature, weight, etc.) against the SIDs for its fleet, and concluded early-on that airport x is not limiting.
The pilot will normally be presented with runway specific thrust setting / weight limit. If you're below this weight, then you may have more than one thrust/flaps setting to choose from. SIDs for the most part (for an airline flying a 737) are not limiting except in extreme airports. Note that the SIDs are designed with the planes/airlines that use them in mind, especially that noise is another important factor.
If you are not an airline pilot and you have your own business jet, then this is a different matter. But because business jets have limited payload/fuel compared to jet-liners, the performance tables are not as complex and indeed can be printed. In other words, those SID figures are more important to general aviation pilots (you may also notice that some SIDs are for turbine aircraft only).
Flight sim
For the purposes of a flight simulator, you can take this as an opportunity to test the impact of each condition one by one. If your 737 allows VNAV arming on ground, you may get "unable next altitude" if the plane thinks it can't make the first restriction, although this is not good practice, as the actual climb is divided into segments, each with a different performance, and the first waypoint may not be representative of the most demanding segment.
You can also test all the extremes at once and see what vertical speed you get. 1100 FPM can be achieved by a 737 in a wide range of conditions, if it can't get to 1100 FPM close to the ground, then getting to cruise will be quite the challenge, i.e., test the conditions to put that value in perspective.
I recommend browsing the aircraft-performance and performance-calculation tags, as well as checking the Airbus publication 'Getting to grips with aircraft performance'.


How do airliners with engines mounted on places other than wings suppress wing flutter?

Since flutter is a natural-frequency harmonics phenomenon, it's a matter of "tuning" the wing box structure with the required stiffness and damping to move its natural frequency range outside the range experienced with its C of G and torsional center offset and uncompensated for with engines on pylons.

It's a bit like with flight controls.  With manual ailerons, the aileron/wing system is flexible you could say, and needs mass balancing.  Like wing mounted engines.

With hydraulic controls, the connection between the aileron and wing is rigid outside of movement induced by the hydraulic actuator.  No mass balance required.  Like a wing box with no engines that has to be inherently stiffer than otherwise.

It's one reason wing mounted engines are more common than tail mounted.  Lets you make the wing box structure a little lighter.


Are the military tilted-thrust aircraft in the film Avatar feasible?

I presume you're talking about the fictional Aerospatiale SA-2 Samson. From that page:

  Ducted fan VTOL aircraft have been flown since at least the 1960s. A notable example was the Bell X-22, a quad-ducted fan experimental aircraft built for the US military. It has no relation to the later V-22 Osprey tiltrotor. Though successful, no military aircraft since have used that technology.

The Bell X-22 looked like this:

which has similar overall characteristics to the SA-2 depictions.


What is the maximum side slip angle that can be achieved by a F-16?

Knife-edge flight is an aerobatic maneuver where an airplane is flying on its side for an extended period of time without ascending or descending.

Notice it says aerobatic, i.e. for show. There is no point doing it on a mission (or otherwise) in an F-16.

Spoiler: it can't be flown in an F-16.

  The flight control computer (FLCC) of the F-16 further incorporates limiters governing movement in the three main axes based on attitude, airspeed and angle of attack (AOA); these prevent control surfaces from inducing instability such as slips or skids, or a high AOA inducing a stall. The limiters also prevent maneuvers that would exert more than a 9 g load.

  — Wikipedia

One source mentions 10° of beta (sideslip angle) as an extreme and unusual for an F-16.

  Departure from controlled flight / Rudder input

  The Aileron Rudder Interconnect (ARI) automatically provides rudder input according to pilot roll input
  to reduce sideslip during turns. Pilot induced rudder does not improve turn performance but increases
  departure possibility.

  Yaw FLCS

  Since the rudder is mostly controlled in flight by the FLCS through the ARI (Aileron Rudder
  Interconnect) the pilot should in theory have no need to use the rudder in flight. To prevent pilot
  induced rudder movement which can create adverse effects the FLCS automatically limits its use.
  Rudder authority is reduced as a function of AOA, roll rate and CAT config to prevent departure from
  controlled flight.

  — BMS manual

Note: Crosswind crabbed flight is not a sideslip. The flight is coordinated (ball centered). Since the wind pushes the plane off track, the pilot corrects by pointing into the wind, that's all.

Just as tailwind or headwind has no effect on the flight dynamics, so is the crosswind. A plane flies inside a mass of air, if the mass of air happens to be moving, it only affects the navigation (where the plane is actually going, and how fast/slow).


Is there any class G airspace that extends to 14,500 MSL?

Historically there was much more uncontrolled airspace in CONUS. There is less but it exists. 14500 is the old continental control area, sometimes called the continental control shelf.  It was designed with the highest natural obstruction in CONUS in mind.

In uncontrolled airspace IFR operations could be conducted without ATC involvement.  I used to do this frequently.

The idea was that in the Continental Control Area, IFR ops were controlled.

For the second question, some Class G exists because there is inadequate service coverage and traffic density and the blanket classification to Class E is inappropriate.


Is the flight management system software independent from the hardware?

If you are thinking of the analog of installing windows or linux on a given physical personal computer then the answer is more or less no. Not because its not possible but more because thats not how avionics are made or how the avionics pipeline has developed over the years. Avionics also work quite differently than your basic home computer as they are designed to be far more redundant and have far more real time conscious operations. You, as a user a free to run any software you like on your computer as its unregulated and does not matter if say one process blocks another, a process fails, a process produces erroneous outputs or a process all together destroys the machine, these things would not be great in avionics.

There are two basic flavors of avionics "software" components/updates:

Database updates:  these occur regularly when a new dataset is made available and update the waypoints, VOR's, Frequencies, and Maps in the system.

Database updates all ultimately contain the same information (generally speaking). Depending on where you are in the world the information is maintained by various regulatory authorities as well as some other companies. However to play nice with a given FMS the data may need to be delivered in a specific format. As far as I know there are no public FMS data formats and generally you need to get the database updates directly from the maker of the unit.

These could be interchangeable with some coordination but the various makers have a steady income stream from the updates so there is little incentive to change the model.

Data sets from someone other than the manufacturer will most likely not load and may come on the wrong card type or be incompatible with the loading system. Likewise not all units are capable of consuming/making use of the full data set.

Software Updates: these occur perhaps on a schedule or perhaps when needed and change the functionality of the system. Or if there is a bug in the system.

Avionics tend to be quite proprietary largely because it costs a lot of money to certify and design avionics on top of this manufacturers of avionics components have certain responsibilities to upholding certificates. If problems arise with the unit arise they may need to provide a fix, as such its simpler to have control over the whole unit, both soft and hardware. This also helps to cut down on the potential combinations of software/hardware units in the event of an issue either on the software or hardware side, it also absolves you from needing to certify all possible combinations.

One things thats very important is that due to the use case, avionics tend to blur the lines between hardware and software in terms of what is implemented where. Keep in mind that generally anything that can be implemented in code can be implemented in pure discrete logic. Similarly most things implemented classically in hardware can be modeled in software. As such the blurred lines and often tight coupling and required knowledge across the platform makes it almost required to do it all as one.

You can find a lot more about the FAA's hardware and software certification process here as well as some notes on avionics software here. There is also some decent tangentially related info in this answer.

This group seems to be building some kind of open source airplane with open source avionics and might be worth reading up on to see where they are at and how they went about doing it.

But its not all for naught, things like the ARINC standards have been developed allowing for the creation of Integrated Modular Avionics and pushed for standardizing at least parts of the equation and opening future possibilities of at least mixing and matching components.


What does the extending the flaps do (or any high lift device) to the Rate-Of-Descent of an airplane?

According to the FAA, lowering or extending flaps allows one to increase drag without an increase in speed.  This increases descent rate for a given speed.

One must be careful to consider what factors are held constant to evaluate the effect.  For example, one can lower flaps during level flight. This will result in a lower pitch attitude--since they produce more lift, less angle of attack is required.  If power/thrust is not increased, speed will decrease due to increased drag.

However, an aircraft flying at a constant speed will descend faster (higher rate of descent) if the flaps are extended compared to when they are not.


What do I do with fuel, distance, and time to descend and climb, on nav log?

Realize that both the climb and descent are taken from the en-route section.

I always calculate climb first and determine where I will reach top of climb on the sectional chart. I then calculate descent and figure out when I need to descend on the sectional chart. The distance in between is my en-route section.

From reading your question, it seems you calculated en-route from departure airport to destination airport. You don't want to do that.


Should "mayday" be preferred over "SOS" in an emergency?

SOS is a distress signal. In the context of aviation emergency calls it would be equivalent to a Mayday call, which is the standard voice signal for distress.

There is, as far as I'm aware, no standard equivalent for an "urgency" (pan-pan) situation in morse code.

As far as its use in aviation, most aviation communication today is by voice (radiotelephone), and "SOS" is not generally used in voice communication.
Its used by morse code stations is because it is a short and easily recognized pattern:
. . . - - - . . .

Its recognizability is part of the reason it replaced the old Marconi CQD general distress call code
- . - . - - . - . - . .
which was literally a general call to all stations (CQ) signaling "distress" (D).

I can't find a reference, but I would assume there's at least one case in history where the SOS code was used by an aircraft (back when morse stations were common on aircraft).

An SOS signal could of course be transmitted today using the unmodulated carrier from your radio by simply keying the microphone, but that would only be useful if the voice circuit of your radio has failed and you had no other means to communicate. Otherwise voice contact or setting your transponder to an appropriate code would generally be the preferred way to signal distress.


What medical history questions are asked for a UK Class 1 Medical?

In the general medical examination they will go through the medical history you have written in FORM MED 160.


Can airliners operate without an operating APU?

Yes, you can operate without an APU.  If the APU is inoperative you will need to write it up and coordinate with maintenance and dispatch to operate under the stipulations of the MEL.  This may restrict certain kind of operations but if we assume a route completely over land this has no effect other than needed ground services.

The requirements for no-APU is simply a ground start "huffer" cart at your departure airport.  Ideally you want one at the destination as well but if not available you can possibly coordinate leaving an engine running during the turn.  More generally though, if the destination does not have access to a huffer cart you will get an aircraft swap and the non-APU aircraft will be assigned to a route that does have those ground services available.

The general process of a non-APU flight is keeping ground power and ground air conditioning hooked up to the airplane for pre-flight activity and boarding.  Once the airplane is closed up the ground crew will coordinate with you to provide air via the ground start cart and you'll start one or both of your engines.  After you have an engine running, you'll disconnect all of the ground equipment and push back.  During the taxi, if you only started one engine earlier you'll perform a crossbleed start to start the other engine.  The takeoff engine bleed and pack configuration may be different for a non-APU takeoff but once you are airborne and set the bleeds and packs for post-takeoff you will be operating exactly the same way you would normally operate and the differences cease.

On arrival the only differences are to make sure you keep an engine running at the gate until ground power is hooked up.

The biggest downside to operating without an APU is the lack of decent air conditioning during taxi and ground operations.

Other considerations for operating without an APU are airplane specific.  For example, the EMB-145 has two generators per engine and one on the APU for a total of five generators.  The airplane will revert to "essential" power if less than 3 generators are available which means you will lose certain displays and systems that become unpowered.  This means if you had an engine failure during flight without an APU you will be in essential power and have to land in that condition because you cannot start the APU to get back up to 3 generators operating.


How can air travel be so safe if the aircraft skin is only 1-2 mm thick?

Simple maths. Cut a cabin in two, lengthwise, and check the forces involved. The halves are held together by 4mm of aluminium, and need to withstand a pressure differential wrt to the outside over the diameter of the cabin.

Let's assume that we have a wide body plane of 6m diameter (larger than a Boeing 777), and a pressure differential of 1atm (of course, usually a plane only maintains up to 0.8atm and does not fly in a vacuum, but let's have some safety margin).

The resulting tensile stress is then about 150MPa. Aluminium only yields at 275MPa.

Other forces are carried by struts, spars and in the case of the fuselage, stringers. The skin transfers shear forces between those perpendicular stringers, but I do not think those forces are significant compared to pressure loading.


Why are modern regional jet designs shifting towards under wing engines?

The underwing engine location allows for a lighter airframe.

Placing the engines under/ahead of the wings brings these benefits:

Bending relief: Engine mass is closer to where lift is created, so the structure has less stress to carry around.
Flutter suppression: Placing the engines ahead of the elastic axis of the wing shifts the flutter speed up, so the wing can be built less stiff.
Better evacuation: With wing-mounted engines a rear door is possible to create a second point for emergency egress.
Lower noise level in the rear cabin.
More useable cabin space at the rear.
Easier access to the engines for maintenance.
Shorter piping for fuel and bleed air. Especially in the narrow fuselages of regional jets the air ducts for ventilation take a lot of valuable space.
And don't discount psychology: The underwing engine design looks more like the bigger jets, which can be a big factor for some passengers. The airplane looks safer and more mature.

With modern CFD it is much easier to reduce the interference between the engine nacelles and the wing, so the biggest disadvantage of an underwing engine location can be reduced.

Note that early designs for the Boeing 737 used rear-mounted engines. By relocating them under the wings, the structure could be made 700 kg lighter. Quote from www.b737.co.uk:

  Overall, the wing-mounted layout had a weight saving of 700Kgs over
  the equivalent “T-tail” design and had performance advantages.

The rear-mounted engines were a fad from the late Fifties (started by the Sud Aviation Caravelle) to the mid-sixties and driven by the concern about the higher risk of low-mounted engines ingesting debris and the higher asymmetry in engine-out conditions. With more operational experience and more reliable engines, these concerns proved unfounded. Citing www.b737.co.uk again:

  Initial worries about the low mounted engines ingesting debris proved
  unfounded, this was demonstrated by the Boeing 720B whose inboard
  engines are lower than the 737's and had been in service for four
  years without significant problems.

Small business jets still prefer rear-mounted engines so they can operate from more airfields (on which the runway might not be as clean as those of big airports) and because the weight penalty of rear-mounted engines is less pronounced. Instead of bending and thrust loads, handling loads and manufacturability drive the minimum skin gauges on smaller jets.


Why is there no alert if shutting down a running engine during flight?

Because in an emergency situation you do not want to stand in the way of the pilot.(*)

Whoever designs the system knows that it could fail and it also knows that there are two pilots in the cabin. These pilots have been trained to deal with the emergency, have spent hours and hours in simulators to be ready when something happens, you do not want to treat them as clueless users, you want to treat them as professionals that are doing their jobs.

The system told them that there was a failure, if it would have been a black/white decision the system could have already shut off the engine, but it did not: it lets trained personnel to asses the situation and act accordingly.

*: as fooot correctly points out, you do not want to annoy the pilots with warnings (remember, you just told them an engine is not working!), they may be tempted to preemptively cancel them, causing them to miss other warnings that are actually important.


Could an explosive decompression trigger the smoke detectors?

In an explosive decompression the cabin air may fog, this is because of rapid cooling causing the moisture in the air to condense. How thick it is and how long it may last depends on a number of factors.

There are two types of smoke detectors, these are optical particle detection devices and ionization devices. Both types are used on commercial aircraft, some detectors have both methods built in.  Ionization devices are tripped by changes in the electrical conductivity of the air flowing through them and are not very sensitive to steam. Optical smoke detectors work on a different principle, detecting light being scattered by particles in the air. Optical devices are susceptible to false readings from moisture, in fact manufacturers of home devices recommend they are installed away from bathrooms to avoid false alarms.

However, airplane certified units are designed and built to a very high standard, the FAA states in the Aviation Maintenance Handbook that requirements for fire protection systems include:

  No false warnings under any flight or ground condition.

So it is very likely that the manufacturers have taken steam into account, after all cabins sometimes fill with steam when the air conditioning has been turned on when if the air is very moist. An extreme example is this flight at Shenzen. That did not set off smoke alarms, and although I've never seen it that bad I have personally been in the cabin when it's noticeably filled with steam and there were no smoke alarms.

So yes, the cabin can fill with steam in an explosive decompression, but it is unlikely - but possible - that the smoke alarms would go off.


Do you need type ratings for private flying?

In addition to a type rating, you cannot fly a 737 without a commercial pilot's license and 1,200 flight hours. Further, your flight and maintenance operation must be certificated by the FAA. You'll need FAA approved opspecs, flight manuals, pilot training and testing, a drug test program, hazmat program, a designated safety manager, and more.

Aircraft with 20 or more passenger seats, or 6,000 lbs payload capacity must be either flown under Part 121 air carrier rules or else they fall under Part 125 regulation. Except for limited circumstances, they cannot be operated under Part 91 (exceptions fall under Subpart F). Because your party isn't a training flight, you don't own the plane, it isn't a sports team, etc., you are under Part 125.

Once the aircraft is large enough, there is no longer a distinction between private and commercial operation, Part 125 covers commercial operations short of common carriage. Even if you're operating an aircraft privately, you have to comply with commercial level safety requirements.


Is there an efficiency measure for airports?

The Air Transport Research Society (ATRS) has a benchmarking system for determining the efficiency of the airports.

Basically,it takes the airport size and related infrastructure (runways, no. of gates etc.) as inputs and measures the airport efficiency in terms of aircraft and passenger movement,revenue etc.

There is a yearly Global Airport Benchmarking Report.


Is starting a jet engine without ground support possible?

Modern jet transport category aircraft have APUs and they will be running if no engines are.  Batteries on jets do not work very long with all electrical buses energized and the first thing you do after turning the batteries on is seeing that they are working correctly and then starting the APU (assuming no GPU is hooked up, if there is a GPU then starting the APU will be deferred until just before the GPU is disconnected).

Thus, any aircraft on a theoretical no-engine taxi to the runway will have a running APU providing electricity to run the airplane and bleed air for an attempt at air conditioning (some aircraft are better at this then others).  When it is time to start the engines they can be started using the APU as the bleed air source and this is a normal method of starting and no different than the method used currently when the plane leaves the gate (and for some airplanes they only start one engine and taxi on that as long as possible before starting the other engine).

As long as the plane has a running APU, it can complete a normal engine start with no ground assistance.  The only limitation will be turbine warm up time, which just means you'll need to make sure the engines are started a few minutes before takeoff thrust is applied.

Just an aside, but currently the only ground support strictly required is a tug to push the airplane away from the gate and someone to operate the jetbridge.  Aircraft and engine startup is self-contained unless the APU is inoperative.


Is the compressibility of air the reason high aspect ratio wings are more effecient

No. In fact, compressibility does not really come into play until you come into ground effect or high Mach numbers.

Let's consider placing an object (why don't you try your (empty) coffee cup?) in mid-air. The moment you release it, it will rapidly accelerate downwards and eventually disassemble spontaneously. This is because air can move out of the way of the coffee cup. The only reason the cup experiences some resistance is due to the viscosity in air (very minor effect) and the inertia of the air that's in the way.

Lift generation relies almost solely on the inertia of the air. You accelerate air downwards, and due to the inertia of the air mass, you feel a force opposite of this, that is, upwards.

The reason high AR wings are more efficient at this process has to do with reducing induced drag. Specifically, it is more efficient to accelerate a large mass of air a little bit, than a little bit of air a lot. Copying from an earlier answer of mine,

  The force to keep the object aloft is $$F=m_{object}g$$ The force generated by downwards momentum transfer is $$F=\dot{m}v$$ with $\dot{m}$ indicating mass flow (kilogram per second) of the air (not the mass of the object). The energy flow (power) required to  impart this momentum on the airflow is $$ P=\frac{1}{2}\dot{m}v^2$$ Here we can draw an important conclusion. The power requirement is arbitrarily small, by increasing the mass flow and decreasing the downwards velocity.

This is the main reason for high AR wings: by increasing the wingspan (so, for equivalent surface, we increase the AR), we increase the amount of mass flow $\dot{m}$ affected by the wing.


How can an aircraft turn if the horizontal force component is zero?

It is easier if we look only at the forces experienced by the aircraft, and in an inertial frame of reference

In this revised diagram, the vertical component of the lift balances the weight, which is vertical. There is a remaining horizontal component of the lift, and this causes the turning.

"Centrifugal force" does not exist (and is not needed) in an inertial frame of reference

The problem with the original diagram in the question is it superimposes an imaginary force, the centrifugal force, upon the real list of forces on the aircraft.

It is hard for the general public to understand Newton's first law of motion, that any object tends to travel in a straight line when no force is acting it. It is hard for them to understand that motion in a circle is dramatically different from straight-line, constant-speed motion, since both seem (in a sense) steady or continuous.

"Centrifugal force" is a term produced by humans to describe what they think must be happening

In the case of a passenger going round a corner in the car, this inward force is applied by the outer door of the car, against which the passenger ends up leaning during the turn. It is an inward (centripetal) force, but for the general public who is not aware of the special status of inertial frames of reference will likely use the car (which seems large and solid and therefore plausible) as a frame of reference and say "something must be pushing me against the door" rather than "the door is pushing me towards the centre of the circle".

Because of this use of a non-inertial frame of reference, the general public explanation needs to an extra force to explain why objects seem to accelerate towards the outer door of the car and the passenger feels pressed against it. In an inertial frame of reference it is the outer door of the car pressing in on the passenger, and accelerating towards any objects moving freely inside the car.

In everyday life we sometimes use special frames of reference for convenience

We say the sun "comes up" in the morning, rather than the earth "rotates bringing the sun into view". This is because it is convenient for humans to use a non-inertial, but readily identifiable, frame of reference. It does not mean that people really think that the sun orbits around a stationary earth.

It is perfectly reasonable to imagine the sun travelling around the earth, for convenience, but if we want to make calculations about space travel with multiple objects (stars, planets etc) affecting a body's motion, it will get very complicated indeed to add in all the numerous centrifugal forces etc we would have to add in. It would be simpler to use an inertial frame of reference, and all objects moving relatively simply in relation to that.

Likewise we can learn to be sophisticated about circular motion. Let the general public speak of "centrifugal force" as this simplifies conversation, but when trying to calculate things, use an inertial frame of reference to avoid agony.

Even apparently inertial frames of reference may have unconsidered rotation  in relation to a larger-scale environment

Jan Hudec in the comments below brilliantly deflates the above criticism of rotating frames of reference by pointing out that even my notionally inertial frame of reference (the earth) is in fact rotating, so that the gravitational force measured is lower than it would be for a plane moving similarly above a non-rotating earth, i.e. is attenuated by a centrifugal component. Ouch!

And of course the earth is rotating around the sun, and the sun around the galaxy, etc:

Big fleas have little fleas,
Upon their backs to bite 'em,
And little fleas have lesser fleas,
and so, ad infinitum.

So it is just a question of how much rotation one wants to accept as part of one's frame of reference. My suggestion is that when a questioner is feeling puzzled as the original poster was, a good way to break the problem down is to keep the frame of reference outside the rotation being studied, so that the studied rotation appears as a rotation: in this case the only acceleration (and therefore force on the orbiting object) will be centripetal.


What requirements are there for radio systems in aircraft?

What are the requirements for radio systems in aircraft?

Generally there aren't any, at least as far as "being required to have radios".

It is perfectly legal to fly around in most of the United States in a Piper Cub with no radios of any kind.
Indeed, unless it's been retrofitted with one a Piper Cub would have no electrical system at all - so you would only be able to fly under "daytime VFR conditions" in airspace not requiring communication with air traffic control (absent special arrangements).

If you elect to fly an aircraft equipped with radios (as most of us do) there are specific requirements those radios must meet, which are described in Technical Standard Orders (TSOs).

This is not a comprehensive list, but:

For Communication radios these are outlined in AC 90-50D and TSO C-169a.
Transponders must meet specific TSO performance criteria per FAR 91.215
Navigation Radios (VOR/ILS/ADF) must meet specific TSO performance criteria if used under instrument flight rules.
The TSO number for these escape me at the moment but I'm sure you can look them up.
GPS systems must meet TSO C145c / TSO C146c requirements (if used for IFR navigation).
The Emergency Locator Transmitter (ELT) must meet specific TSO criteria.

The requirements obviously vary based on the type of radio, and typically reference other industry standards (for example TSO C-169a for VHF communication radios sends you over to RTCA/DO-186B for the actual performance criteria).


What is the range of amplitude of vibration in a helicopter?

The amplitude of the vibration depends on the frequency and the acceleration: at a given acceleration, only at low frequencies do we get any significant displacement. If displacement is taken as the intensity indicator, the frequency plot is weighted towards low frequencies - the higher frequencies have a higher energy contents, that is why often a logarithmic relative scale is used (dB).

This document gives good information and background on measuring th severity of vibration. It can be done with an accelerometer: integrating acceleration yields velocity and displacement as well. From the document:

  Experience has shown that the overall RMS value of vibration velocity measured over the range 10 to 1000 Hz gives the best indication of a vibration's severity. A probable explanation is that a given velocity level corresponds to a given energy level so that vibration at low and high frequencies are equally weighted from a vibration energy point of view. In practice many machines have a reasonably flat velocity spectrum.

The vibration frequency plot in the previous answer is in dB acceleration, an earlier slide shows the reference. If it is displacement of a particular frequency in the plot you are after:

Read dB acceleration at the particular frequency
Convert into m/s$^2$ to get acceleration $a$
Amplitude = $\frac{a}{(2 \pi f)^2}$


What are the different steps to certify a new aircraft in Europe?

The EASA certification requirements are all publicly available online. Actually proving that an aircraft meets those criteria will certainly include all the steps you mentioned although exactly what happens probably depends a lot on the specific aircraft and manufacturer.


If cabin lights are dimmed during night landing so that your eyes will get used to the darkness, why do they let you use the reading lights?

That is a good question. It is most likely a compromise. Turning down the cabin lights allows for night vision adaptation for most. Its better to have at least some of the passengers adapted, than none at all. Its a compromise between optimal safety (night vision adaptation) vs customer service (being able to finish reading your Harry Potter book).


What is the minimum distance allowed between two parallel runways?

In the United States, the FAA has published Advisory Circular 150/5300-13A, Airport Design , which includes standards and recommendations for airport design, including parallel runway separation.

In summary,

"For simultaneous landings and takeoffs using VFR, the minimum
separation between centerlines of parallel runways is 700 feet (213
m)."
For simultaneous IFR operations, "Dual simultaneous precision
instrument approaches are normally approved on parallel runway
centerline separation of 4,300 feet (1311 m). On a case-by-case
basis, the FAA will consider proposals utilizing separations down to
a minimum of 3,000 feet (914 m) where a 4,300 foot (1311 m)
separation is impractical. This reduction of separation requires
special high update radar, monitoring equipment, etc." Note:
Simultaneous Offset Instrument Approaches allow as little as 750 ft
between runway centerlines.

International regulations do differ. ICAO have their own standards. Here is an example of a document which prescribes airport standards compliant to ICAO Annex 14.


(Source) Cool room in a cargo terminal.

  The rabbit arrived fine but there was some sort of mistake and he was locked inside a freezer overnight.

Goods that are perishable and human remains awaiting transport, wait in the freezer before being loaded onto flights.

Different rooms for cargo handling can be seen here, they include:

Cool rooms
Freezer rooms
Warm rooms (for e.g. perishable flowers)
Dangerous goods rooms

There are also specialized ULD's that come with refrigeration units.

(Source) Temperature controlled ULD.

  [Depending] on the nature of the goods to be transported, [ULD's] may have built-in refrigeration units.


Can a US airline add an employee passenger as crew?

First of all it depends on what type of "employee" and if the jumpseat is in the cockpit or the cabin.

According to the answers to this question there are no regulations on who may sit in a cabin jumpseat as long as it meets the specifications set out in FAR § 121.211 for proper airline seats. So the airline is free to set policy for cabin jumpseats.

As for jumpseats on the flight deck the restrictions are quite stringent. If the employee is a pilot FAR § 121.547(c)(3) allows off-duty pilots to fly in a jumpseat on the flight deck, so there would be no need to make them an active crew member.

FAR § 121.547(a)(1) allows an on-duty flight attendant to fly in a jumpseat on the flight deck. The person would have to be a certified flight attendant, so you couldn't just make any employee a crew member. Remember also that flight attendants have hours of service restrictions, so any time they are considered on-duty has to comply with the h.o.s. regulations.

Certain other types of employees are allowed to fly in the flight deck, but they have to be performing a specific function on the flight that requires their presence in th cockpit. For example, a mechanic could fly in the cockpit if he's there to monitor something on the aircraft. A flight dispatcher could be on the flight deck if they are observing flight operations as a part of training.

Even some persons who may be given access to the cockpit for operational need, like air marshals or training personnel, still must have a seat available in the cabin.

So they can't put someone in the cockpit just to transport them from place to place and they couldn't just plop a salesman or a ticket agent there and say they are a "crew member."

There are regulations stipulating the minimum number of flight attendants on a flight but not a maximum number. So, technically they could make a flight attendant part of the crew, but if that person was just listed as a crew member and wasn't actually performing any duties, the FAA would certainly interpret that as a violation.


How should a loss of communications in VFR be dealt with?

should I blindly continue in

First, never do anything "blindly".

The FAR and the AIM address the Class D question, so this part is the most easily answerable:

  FAR 91.129 (d) Communications failure. Each person who operates an aircraft in a Class D airspace area must maintain two-way radio communications with the ATC facility having jurisdiction over that area.

  (1) If the aircraft radio fails in flight under IFR, the pilot must comply with §91.185 of the part.

  (2) If the aircraft radio fails in flight under VFR, the pilot in command may operate that aircraft and land if—

  (i) Weather conditions are at or above basic VFR weather minimums;

  (ii) Visual contact with the tower is maintained; and

  (iii) A clearance to land is received.

  AIM 4-2-13 (3). Transmitter and receiver inoperative. Remain outside or above the Class D surface area until the direction and flow of traffic has been determined; then, join the airport traffic pattern and maintain visual  contact with the tower to receive light signals. Acknowledge light signals as noted above.

After that, 6−4−1 addresses more two-way comms failure actions:

  a. It is virtually impossible to provide regulations and procedures
  applicable to all possible situations associated with two-way radio
  communications failure. During two-way radio communications failure,
  when confronted by a situation not covered in the regulation, pilots
  are expected to exercise good judgment in whatever action they elect
  to take. Should the situation so dictate they should not be reluctant
  to use the emergency action contained in 14 CFR Section 91.3(b).

Since "best judgement" is very situational dependent, the rest of this is subjective:  I would not enter Class C, if there was another alternative. If you're already in Class C, and there are Class D/E/G airports available, divert. If you're already in Class C,and there are no other options, continue with the utmost caution (following the advice of the Class D procedures if able), using your own light signals to attempt to alert the tower.

Some "armchair lawyers" might even say that lost-comms (VFR) operations in Class C and even Class B could be conducted in the same manner as Class D, because each section starts with: "each aircraft operation in Class B/C airspace must be conducted in compliance with this section and 91.129."

I'd personally avoid B and C like the plague if I was VFR lost comms.


Why do airliners have to park so accurately?

This is to ensure that there is space for all equipment around the aircraft. It's not critical to the centimeter, but if it's off by a meter or more there may be problems. For example, the tail may stick out into the taxiway behind or the nose may stick into the service road in front of the aircraft. While most aircraft stop with the nose wheel on or very near the stop-mark, the main wheels can be off by a few feet, depending on how early/late the pilot turns into the stand.

Modern aerobridges have a wide range of movement to cater to various aircraft types, but nowadays there is a lot of equipment buried in the ground. You might see ground power and air conditioning hoses which plug into the ground next to the aircraft nosewheel area. If the aircraft is off by a few feet the hose/wires may cause obstruction to the ground crew. The hydrants for fuel also need to be near the fuelling ports - too far and the hoses might not reach.


To receive an SVFR clearance, does the airport need to be reporting IFR conditions?

A Special VFR (SVFR) clearance may be issued to a pilot when:

The weather is below VFR weather minimums, as reported at the intended airport
The pilot is able to remain clear of clouds
The pilot has at least one mile flight visibility (other than helicopters) at all times
The pilot is operating (or wants to operate) within the lateral boundaries of the airport surface area
The pilot specifically requests it.
The airport is not among those listed in 14 CFR Part 91, Appendix D (except helicopters)

If the weather is not reported at the airport, the pilot must tell ATC that they are "unable to maintain VFR" and request SVFR.

Side note:  The weather conditions that you describe above are technically "Marginal VFR" and not IFR.  It would be a perfect situation to operate SVFR though.


I don’t believe that airspeed directly affects fuel flow, but it may impact other variables that can have an influence.
I don’t have a flight manual for an F-104, but for the EA-6B the manual says the following about the fuel control unit on the J52P-408A engine: (straight turbo jet, non-after burning, 1970s technology)

“The engine fuel control is divided into a computing and metering
section.  The computing section monitors throttle position, burner
pressure, engine speed, and compressor inlet temperature.  These data
are translated into a fuel demand that is relayed to the metering
section, which measure the correct amount of fuel from the engine fuel
pump the fuel pressurizing and dump valve.”

Of those four inputs the primary would be throttle position, with metering occurring to dampen out pilot inputs and ensure smooth operation.  The other three may be influenced by environmental conditions such as airspeed, altitude, etc. but airspeed itself is not an input.
Modern FADEC, (Full Authority Digital Engine Control) engines might be different.


What is the difference between a stall fence and a vortex generator?

The wing fence is more or less what it is called- a fence. For swept wing aircraft, the local flow is not along the direction of flight, as there is a significant spanwise flow from the center towards the tips. It can be seen in the following figure.

Image from fuckyeahfluiddynamics.tumblr.com

The end result is that the boundary layer continues to grow (thicken) in this direction, with outboard regions more prone to stall than inboard ones. Basically, the wing fences stop the spanwise flow, with the result being a new (thinner) boundary layer starts on the other side of the fence.

In case of a vortex generator, the VGs basically create a vortex which re-invigorates the boundary layer by mixing free stream air with that of the boundary layer, thereby preventing separation.


What design feature prevents the fuselage skin from completely tearing off?

In the 1980's, manufacturers thought that they had solved the problems that plagued earlier models like the De Havilland Comet. Then Aloha Airlines Flight 243 had a large section of upper fuselage come off during flight. Manufacturers realized that the fuselage could accumulate more damage more quickly than expected, and when this damage went undetected, it resulted in catastrophic failure.

The result was both regulators and manufacturers emphasizing a focus on both damage tolerance and fail safety when designing these structures.

Damage tolerance means that the structure can tolerate a certain amount of damage while still performing its function. Inspections should be performed soon enough that they will detect the damage before it compromises the structure.

Fail safety means that even if a feature fails, the overall structure can still perform its function. One option for this is redundancy. In the fuselage, this means stopping cracks from propagating too far. The cracks in the Aloha Airlines incident were able to continue growing until a large portion of structure failed.

These ideas mean that the structure is designed so that any damage is caught before it becomes critical, but in the event that this is not sufficient, items can fail without endangering the safety of flight.

An example is what happened to Southwest Flight 812. A section of fuselage ripped open in flight, which resulted in a rapid depressurization but a safe landing. A crack formed in the fuselage and was not detected. However, the crack was contained in a limited section of the skin. This allowed the cracked skin to fail while the rest remained intact.


I assume that you're a passenger travelling on a flight and you want to know how long the flight will last, from takeoff to landing.

First you would need to get the route you're going to fly. Sometimes the published route is available on flight-tracking sites, for example this one. After that, you can plot the route on an aviation chart to get the distance. If the route is not available, you will need to construct the likely route by guessing which airways the flight will take.

Next you need to figure out your plane's groundspeed. The groundspeed is not constant. When the plane is climbing, part of the engine thrust is directed upwards, so ground speed would be slower. Engine thrust also varies with altitude, so the ground speed will vary throughout the climb. You will need an aircraft performance table, which typically has data at 1000 feet increments. You need to repeat the calculation for each 1000 feet until the aircraft reaches cruise altitude.

We will assume the aircraft remains at a constant cruise altitude for now. You can easily work out the flight time by looking up the cruise groundspeed (not airspeed).

Now we need to figure out when the plane will begin its descend. From the route you obtained earlier, you'd have known the flight's cruise altitude. Flights typically descend 1000 feet per 3 nautical miles. Work your way backwards from the destination, you will have your Top of Descent point. Again, the ground speed will be slower because the velocity vector has a component in the vertical direction. The plane will descend at its cruise airspeed until 10,000 feet, where it will slow to 250 knots.

For a start, this very simplified version would give you a closer estimate to reality. I have left out:

Winds aloft. At high altitude, usually there is a significant wind blowing at one direction. Depending on whether it is head wind or tail wind, it will slow you down or speed you up. Different areas will, obviously, have different wind conditions. Different altitude in the same area will also have different wind conditions.
SIDs and STARs. These are the waypoints which connects flights coming from all directions to a common arrival point for final approach at the destination airport (or the opposite at the departure airport). These waypoints will increase the total length of your route.
Altitude changes. Throughout a flight, the cruise altitude may change. With a new altitude, the engine performance (hence cruise speed) will be different.

In fact, flight time estimation is so complicated that we use software to calculate them. No sane human-being will go through all the data to calculate flight time today.

Note that I did not take into account:

Taxi time: the time it takes to move the aircraft between the gate and the runway on the ground
Holding time: the time which flights are asked to fly in circles near the airport when the airspace is too busy

Your airline will have included these estimates in the quoted time on your flight ticket.


How do pilots calculate the temperature to put Into the FMS for an FLX takeoff?

For Airbus Aircraft you use a tool from Airbus where you put in data like wind, air temperature, pressure, weight, runway characteristics (length, heading, elevation, etc)  and other elements that calculates the flex temperature. It also gives you some other parameter like required runway length among others.


What accident or safety data is available for ultralight aircraft?

This could match your need albeit this is a study from the Finnish Accident Investigation Board, based mostly on Finland numbers over 20 years:

Ultralight Aviation Safety and its Improvement through Accident Investigation (151 pages).

Chapter 9, page 87, also introduces information about other countries related to what they do regarding investigation: Croatia, Cyprus, Denmark, Georgia, Germany, Hungary, Iceland, Ireland, the Netherlands, Norway, Portugal, Spain, Sweden and the United Kingdom.

There is a comparison between ultralights and other types likes gliders and GA aircraft:

Source: Accident Investigation Board

Interestingly, while accidents are decreasing in Finland, this is the opposite trend in France (French article from UL federation, based on insurance notifications, from 15 fatalities in 2006 to 30 in 2010). Maybe just a matter of pilots number increasing.

Related:

Microlight/Ultralight Accident Statistics - Adventure/sport/aircraft: France, Germany, UK, Australia, Canada. From this document: "There is no good accident data for ultralights in the US".
Aviation statistics, including ultralights (1998–2007) Canada, TSB.
British Microlight Accident Analysis, many criteria (MS Word).
Recreational aviation risk survey -  Finnish
Transport Safety Agency.


First up, commercial pilots (both major airlines and cargo airlines): It depends on the country and airline, but the retirement age for a pilot is generally 65 in most countries, and almost always somewhere between 55 (e.g. British Airways) and 65 (standard in much of the U.S.)

There is no set last age at which you could be recruited, so in theory it's just before those ages, but in practice you're unlikely to be hired by a company if you can't work there for at least 5 years.

If you're not yet a qualified pilot, though, you'd have to account for this time too (no company is going to hire you and train you just in time to retire). In practice, therefore, the likely realistic age is at least 10 years prior to the retirement age for the country/company in question, and likely 15.

And if we move into pure conjecture for a moment, I'd hazard that you'd find it quite hard to find a company willing to take on an untrained pilot much after their early-mid 40s.

As for a private pilot: As long as you can pass the medical you can fly and, indeed, learn to fly, at any age. There's no maximum age, although as you'd expect most (but certainly not all) people start to struggle with passing the medical sometime in their 70s. By 80, there aren't too many pilots still flying around.


When must a pilot report Negative Contact?

The short answer is that in your example there's no reason to assume that the controller was asking the pilot to maintain visual separation. If the controller had wanted the pilot to do that, they would have asked if the pilot had traffic in sight and the pilot would be expected to answer the question.
The ATC orders have an entire section on visual separation (section 7-2-1) with lots of details. There are two types: ATC-applied and pilot-applied, depending on who's actually responsible for maintaining the separation. I think you're asking about pilot-applied separation, and there's really nothing in the dialog you quoted that suggests the controller intended the pilot to maintain their own separation. In fact, it's possible that the controller was maintaining visual separation themselves based on seeing both aircraft, and that doesn't require the pilot to have the other aircraft in sight.
If ATC assigns pilot-applied separation, they need to hear two things from the pilot: they have the traffic in sight, and they will maintain visual separation. See 7-2-1(a)(2)(c):

If the pilot reports the traffic in sight and will maintain visual
separation from it (the pilot must state both), the controller may
“approve” the operation

The Orders have an example and it's laid out as a three-step process: first the controller tells the pilot where the other aircraft is, then they ask the pilot to confirm traffic in sight, and finally if the answer is positive they ask the pilot to maintain visual separation. Since ATC is asking a question, the pilot has to answer one way or another, whether that's with "traffic in sight" or "negative contact".
Coming back to the example you gave, the controller simply told the pilot that they were number 2 behind other traffic. The controller didn't ask if the pilot had traffic in sight and while the pilot might volunteer that information, the controller didn't need it at that point in time (they might need it later if the aircraft are getting too close, or something else changes).
Long story short, if ATC needs to know if you have the traffic in sight then they'll ask you.


Could somebody please explain me the differences between using the OBS and the Heading Indicator

They are two very different instruments. The OBS is used to track inbound/outbound from a VOR station, whereas the HI (or, DI - Direction Indicator) shows the current direction of travel (assuming it has been aligned correctly with a compass).

"Turning the OBS to align the needle" is not really the usual way to use that instrument * - you set the OBS to the radial you intend to fly, and use the needle to align yourself with that radial.

If OBS and DI agree with the needle centred, you're on the radial selected by the OBS.

* There is of course a use-case where you just want to go direct to a VOR, and then you may just turn the OBS until it shows "TO" with a centred needle. But if you're doing this regularly you might be using it wrong.


Technical factors to consider for retrofitting aerial refueling for commericial aircraft

Yes, of course this is possible.

The main factor taken into account is pilot training. Mid-air refuelling puts the receiving aircraft into an unstable position which needs to be held manually for the duration of the operation. Without proper training, the refuelling operation will carry a high risk of being unsuccessful. Mechanically the modification is simple: Add some fuel lines, valves and the standard receptacle for the Air Force boom system of refuelling (at the fuel mass needed only the boom system would make sense).

The best example is a Boeing 747-200 B which has been converted as the US presidential transport. The fuel receptacle sits ahead of the cockpit on the upper side of the aircraft's forebody. From the linked site:

  Capable of refueling midair, Air Force One has unlimited range and can carry the President wherever he needs to travel.

modified Boeing 747-200 being refuelled by a KC-135 (picture source)

However, this capability has never been used with any US president on board and is likely to be deleted from the next version of the plane. From Popular Mechanics:

  As part of the effort to cut costs by $1 billion, aerial refueling was cut from the program as well, as reported by Defense One earlier this month. Proponents of the cut argue that aerial refueling is not necessary considering no president has ever used the capability, not even George W. Bush who loitered over the Gulf of Mexico in Air Force One for eight hours after the 9/11 attacks. Opponents of removing mid-air refueling say that the ability to take on fuel and fly for long periods of time, even days, is vital to ensure the government can continue operating in a crisis, including nuclear war.


It works the same way any radar works.  An antenna broadcasts a pulse of energy and listens for its reflection and interprets the power of the reflection to calculate the reflectivity factor Z, expressed in decibels dBZ (helpful because return power varies across many orders of magnitude).  Weather radar can see water, hail, bugs, birds, bats and bigger things, and the ground but not clouds.  Higher return power can mean more objects or bigger objects.  A basic single-polarization radar cannot tell the difference between a tons of small rain drops and a fewer big raindrops.

The particulars of the radar on any aircraft are generally going to be determined by the antenna size, as the optimal frequency of emission varies for a given antenna.  The large S-band* dishes that make up the ground based WSR-88D network are quite big (around 10m).  S-band is a good choice because they have low attenuation and can penetrate through storms and see things behind them.  Airplanes can't use S-band though, because the antennas are too big to put on the airplane and require too much power to fully utilize them.

Airplane radars are generally in the X-band*.  X-band can see smaller particles than S-band but attenuates easier.  This means if a big storm is in front of you, the energy doesn't penetrate far into the storm and may not show you the whole storm.  These are great short range radars and work well in airborne applications as long as you are aware of the issue with attenuation.

Airplane radar displays typically only display information from the on-board radar and do not downlink any additional information from ground stations.  Onboard radar are usually adjustable in the vertical by the pilots, so they can point the radar up or down as needed.

Here is an example of a radar antenna and associated electronics on a Cessna Citation 501:

Image by Dtom, Wikimedia Commons.   https://en.wikipedia.org/wiki/File:Cessna501_radar.JPG

*S-band is 8-15 cm / 2-4 GHz
 X-band is 2.5-4 cm / 8-12 GHz


Why does part 135 require a maintenance log on board the aircraft, but part 91 does not?

For the same reason truckers are required to keep logs in their trucks noting rest times, inspections, etc. but private vehicle owners do not. Part 135 is for commercial operations, part 91 is not.


What is the fastest single-engine civil turboprop aircraft with cabin seating?

In civil GA aircraft, TBM 900 is the fastest one with a top cruise speed of 330 knots (at 28000 ft).

Source: flightclub.jalopnik.com

However, if one considers all single engined turboprop aircraft, the fastest is the Pilatus PC-21, with a top speed of 370 knots.

"Pilatus pc-21 hb-hzc lands arp" by Adrian Pingstone (Arpingstone) - Own work. Licensed under Public Domain via Commons.


How does angle of attack vary during climbing flight?

Angle of attack is the angle between relative wind, a.k.a. flight path, and the reference datum (chord line in the below image, but might be just given relative to longitudinal axis of the aircraft especially since many aircraft have wing twist, so the chord line varies along span).

(figure from How It Flies section 2.4)

Now to you cases

  Just after rotation, I would assume that the angle of attack is equal to x, but after this I get confused.

As the pilot pulls on the control column and the elevators deflect up, the aircraft starts to pitch up. As it pitches up, the angle of attack increases. That increases lift, which is proportional to angle of attack (in the non-stalled region).

As the lift increases, the aircraft will start accelerating upwards, which means its flight path angle will increase. The pitch angle still increases at the same rate, but now the flight path angle also does, so their difference—angle of attack—increase will slow down until it stabilises at some value where the flight path angle rate catches up with the pitch rate.

If the pilot then pushes the control column back and neutralizes the elevator deflection, the aircraft will stop pitching up and the angle of attack will decrease again until the flight path rate stops as well.

In fact the angle of attack at which the aircraft will stabilise is proportional to the elevator deflection (for longitudinally stable aircraft), so if the pilot lets the control column return to its trimmed position, the aircraft will assume the original angle of attack again.

I'll refer you to the mentioned How It Flies chapter 2. Angle of Attack Awareness and Angle of Attack Management for further details.