What does the practical CPL skill test contain?

https://www.easa.europa.eu/sites/default/files/dfu/Part-FCL.pdf

  Appendix 4 - Skill test for the issue of a CPL

  A. General
  1. An applicant for a skill test for the CPL shall have received instruction on the same class or type of aircraft to be used in the
  test.
  2. An applicant shall pass all the relevant sections of the skill test. If any item in a section is failed, that section is failed.
  Failure in more than one section will require the applicant to take
  the entire test again. An applicant failing only in one section shall
  only repeat the failed section. Failure in any section of the retest,
  including those sections that have been passed on a previous attempt,
  will require the applicant to take the entire test again. All relevant
  sections of the skill test shall be completed within 6 months. Failure
  to achieve a pass in all relevant sections of the test in two attempts
  will require further training.
  3. Further training may be required following any failed skill test. There is no limit to the number of skill tests that may be attempted.

  CONDUCT OF THE TEST
  4. Should the applicant choose to terminate a skill test for reasons considered inadequate by the Flight Examiner (FE), the applicant shall
  retake the entire skill test. If the test is terminated for reasons
  considered adequate by the FE, only those sections not completed shall
  be tested in a further flight.
  5. At the discretion of the FE, any manoeuvre or procedure of the test may be repeated once by the applicant. The FE may stop the test at any
  stage if it is considered that the applicant’s demonstration of flying
  skills requires a complete re-test.
  6. An applicant shall be required to fly the aircraft from a position where the PIC functions can be performed and to carry out the test as
  if no other crew member is present. Responsibility for the flight
  shall be allocated in accordance with national regulations.
  7. An applicant shall indicate to the FE the checks and duties carried out, including the identification of radio facilities. Checks shall be
  completed in accordance with the checklist for the aircraft on which
  the test is being taken. During pre-flight preparation for the test,
  the applicant is required to determine power settings and speeds.
  Performance data for take-off, approach and landing shall be
  calculated by the applicant in compliance with the operations manual
  or flight manual for the aircraft used.
  8. The FE shall take no part in the operation of the aircraft except where intervention is necessary in the interests of safety or to avoid
  unacceptable delay to other traffic. B. Content of the skill test for
  the issue of a CPL — Aeroplanes

  The aeroplane used for the skill test shall meet the requirements for training aeroplanes, and shall be certificated for the carriage of
  at least four persons, have a variable pitch propeller and retractable
  landing gear.
  The route to be flown shall be chosen by the FE and the destination shall be a controlled aerodrome. The applicant shall be responsible
  for the flight planning and shall ensure that all equipment and
  documentation for the execution of the flight are on board. The
  duration of the flight shall be at least 90 minutes.
  The applicant shall demonstrate the ability to: (a) operate the aeroplane within its limitations, (b) complete all manoeuvres with
  smoothness and accuracy, (c) exercise good judgement and airmanship;
  (d) apply aeronautical knowledge; and (e) maintain control of the
  aeroplane at all times in such a manner that the successful outcome of
  a procedure or manoeuvre is never seriously in doubt.

  FLIGHT TEST TOLERANCES
  4. The following limits shall apply, corrected to make allowance for turbulent conditions and the handling qualities and performance of the
  aeroplane used. Height normal flight ±100 feet with simulated engine
  failure ±150 feet Tracking on radio aids ±5° Heading normal flight
  ±10° with simulated engine failure ±15° Speed take-off and approach ±5
  knots all other flight regimes ±10 knots

  CONTENT OF THE TEST
  5. Items in section 2 (c) and (e)(iv), and the whole of sections 5 and 6 may be performed in an FNPT II or an FFS. Use of the aeroplane
  checklists, airmanship, control of the aeroplane by external visual
  reference, anti-icing/de-icing procedures and principles of threat and
  error management apply in all sections.

  SECTION 1 — PRE-FLIGHT OPERATIONS AND DEPARTURE a Pre-flight,
  including: Flight planning, Documentation, Mass and balance
  determination, Weather brief, NOTAMS b Aeroplane inspection and
  servicing c Taxiing and take-off Part-FCL – Appendices, AMC and GM V1,
  June 2016 Go back to Appendices Go back to the content 1168 | P a g e
  d Performance considerations and trim e Aerodrome and traffic pattern
  operations f Departure procedure, altimeter setting, collision
  avoidance (lookout) g ATC liaison – compliance, R/T procedures

  SECTION 2 GENERAL AIRWORK a Control of the aeroplane by external
  visual reference, including straight and level, climb, descent,
  lookout b Flight at critically low airspeeds including recognition of
  and recovery from incipient and full stalls c Turns, including turns
  in landing configuration. Steep turns 45° d Flight at critically high
  airspeeds, including recognition of and recovery from spiral dives
  eFlight by reference solely to instruments, including: (i) level
  flight, cruise configuration, control of heading, altitude and
  airspeed (ii) climbing and descending turns with 10°–30° bank (iii)
  recoveries from unusual attitudes (iv) limited panel instruments f ATC
  liaison – compliance, R/T procedures

  SECTION 3 — EN-ROUTE PROCEDURES a Control of aeroplane by external
  visual reference, including cruise configuration Range/Endurance
  considerations b Orientation, map reading c Altitude, speed, heading
  control, lookout d Altimeter setting. ATC liaison – compliance, R/T
  procedures eMonitoring of flight progress, flight log, fuel usage,
  assessment of track error and re-establishment of correct tracking f
  Observation of weather conditions, assessment of trends, diversion
  planning g Tracking, positioning (NDB or VOR), identification of
  facilities (instrument flight). Implementation of diversion plan to
  alternate aerodrome (visual flight)

  SECTION 4 — APPROACH AND LANDING PROCEDURES a Arrival procedures,
  altimeter setting, checks, lookout b ATC liaison - compliance, R/T
  procedures c Go-around action from low height d Normal landing,
  crosswind landing (if suitable conditions) e Short field landing f
  Approach and landing with idle power (single-engine only) g Landing
  without use of flaps h Post flight actions

  SECTION 5 — ABNORMAL AND EMERGENCY PROCEDURES This section may be
  combined with sections 1 through 4 a Simulated engine failure after
  take-off (at a safe altitude), fire drill b Equipment malfunctions
  including alternative landing gear extension, electrical and brake
  failure c Forced landing (simulated) d ATC liaison - compliance, R/T
  procedures e Oral questions

  SECTION 6 — SIMULATED ASYMMETRIC FLIGHT AND RELEVANT CLASS OR TYPE
  ITEMS This section may be combined with sections 1 through 5 a
  Simulated engine failure during take-off (at a safe altitude unless
  carried out in an FFS) b Asymmetric approach and go-around c
  Asymmetric approach and full stop landing d Engine shutdown and
  restart e ATC liaison – compliance, R/T procedures, Airmanship f As
  determined by the FE — any relevant items of the class or type rating
  skill test to include, if applicable: (i) aeroplane systems including
  handling of autopilot (ii) operation of pressurisation system (iii)
  use of de-icing and anti-icing system g Oral questions


What happens when flying on a Victor airway but through a class B or C airspace?

If you are flying your IFR flight plan which you got clearance for, then you have permission already.
If you are flying VFR you need to ask ATC for clearance.
Class B airspace requires clearance for all traffic and separation is also provided by ATC for all traffic.


To what extent is LLF forecast of icing conditions a concern in VMC?

Well if you have a forecast of icing, and you go outside and the sky is clear, the forecast is wrong no?

In any case, when you are flying around VFR and there is the possibility of icing on your route, your main concern is the freezing level, and whether you can stay well below it in the event you encounter rain or drizzle or whatever (aside from visibility requirements of course).  If you will find yourself close to or above the freezing level where you plan to cruise, you have to avoid visible moisture, period.

You're VFR so you will be avoiding cloud anyway, but if there is anything coming down out of the clouds you will pass through, you need to be a couple thousand feet below the freezing level to be safe.

So, if you're going from a to b, at 5000 ft, and the freezing level is 8000 ft, and there is light rain forecast with icing expected, say between 8000 and 15000ft, you're fine at 5000 ft IF, the freezing level is going to stay well above you on your route, but you need to be confident that temperatures aren't going to drop and force you lower part way there.

If the sky is clear or scattered, nice VFR in other words, you are unlikely to see icing in a forecast anyway.


Why does FAA not include certain SIDs and STARs in its CIFP file, even though they are regularly used in flight planning?

Yes it is possible and it is mentioned in the accompanying CIFP Readme pdf. Specifically, it states that

  Procedure types that are not yet included in the CIFP: ILS CAT II, ILS CAT III, ILS PRM,
  Converging ILS and Visual procedures are not included in the CIFP.

  Not-In-CIFP Spreadsheet: ILS (Category 1 only), LOC, SDF, LDA, VOR, NDB, GPS, RNAV
  (GPS), RNAV (RNP), GPS Overlays, GPS and RNAV (GPS) helicopter approaches, SIDs and
  STARs that do not appear in the CIFP will be listed in the Not-In-CIFP spreadsheet. Note that only
  FAA-developed procedures are included in the CIFP. Approach types listed above that are developed
  outside the FAA, such as Navy or Air Force procedures, will not appear in this spreadsheet.

In other words, even though you can at least acknowledge their existence by searching for the missing SIDs and STARs in the aforementioned xlsx spreadsheet, you do not have any information about their structure. As for why they are not included I can not tell for sure, but as far as I could realize from my own research, the few procedures not included in the CIFP file belong to the "old" IFPs (conventional, non-RNAV). This might mean something, but in any case it is my own (un)educated guess and by no means anything that can be confirmed from an official source.


How does flying below the freezing level in a thunderstorm help avoid the most critical icing?

The icing occurs due to the presence of supercooled liquid droplets. From FAA AC on Icing:

  The condition most favorable for very hazardous icing is the presence of many large, supercooled water drops.... Thus, heaviest icing usually will be found at or slightly above the freezing level where temperature is never more than a few degrees below freezing.

For ice to form on the aircraft, the following conditions are required:

The presence of liquid water i.e. rain or cloud droplets.
The temperature at aircraft structure should be at or below freezing point.

Now, as the altitude increases, temperature decreases. Using this, the best way to avoid these conditions would be to either:

Fly above the altitude where the temperature is below -15 degrees, where supercooled water drops are not present (they would've frozen already), or
Fly below the altitude where the temperature is above freezing point, where the water droplets, if present are not supercooled.


Is there a good resource for ACARS messages?

Unfortunately the term ACARS is one of the most misunderstood and misused terms in aviation. ACARS - Aircraft Communications Addressing and Reporting System - was created as an end-to-end datalink between aircraft and the airline dispatchers. It provided basic text data using the ARINC Specification 618-8. (Unfortunately not free.)

As datalink functionality has grown, ACARS has been modified and patched and added to to support these new functions. What is defined in A618 is now classified in the datalink world as AOC - Airline Operational Communications. AOC messages can be found in ARINC 633-3.

The issue with that is that it is communicating with the dispatcher not ATC. That falls under the title ATS - Air Traffic Services. Early versions of this will be found in ARINC 623-3. That has mostly been replaced by newer applications defined in ARINC 622-5 which supports bit-oriented protocol (over the older character based protocols.)

In the last 20 years or so, there has been a plan to provide ATS globally. The European industry which wasn't tied as closely to the ARINC systems as the US took a more more clean sheet approach referred to as ATN - Aircraft Telecommunications Network which isn't interoperable with the ARINC standards. So the industry now supports a mix of infrastructure. As it has moved towards global capability, the standards are migrating into the ICAO ecosystem.

So the best reference available to find answers to almost any aviation datalink related question is the Global Operational Data Link Document (GOLD) published by ICAO.


Is a certificated pilot in a rear seat with no access to flight controls a safety pilot or a passenger?

After looking through the FAR's, the answer is no, the rear passenger seat cannot be occupied by somebody claiming to be a "safety pilot".

FAR 91.109(c):

  (c) No person may operate a civil aircraft in simulated instrument flight unless—

    (1) The other control seat is occupied by a safety pilot who possesses at least a private pilot certificate with category and class ratings appropriate to the aircraft being flown.
    (2) The safety pilot has adequate vision forward and to each side of the aircraft, or a competent observer in the aircraft adequately supplements the vision of the safety pilot; and

(Emphasis Mine)

So the safety pilot basically has to be able to access the controls and have vision that supplements the pilot, meaning must be able to see as well as the pilot position would.


Is the "Red two standing by" dialog in Star Wars: A New Hope sensible for real fighter pilots?

Tactical call signs are typically given in the format "word" "number" - "number".  For example, Camel 1-1.  In this example Camel 1-1 is the lead Camel in the Camel flight.  As you may have guessed, instructions are always acknowledged in order.  This helps the lead aircraft determine who may not have received the instruction (and some instructions are extremely time critical), or worse, in the event of an accident, determine (by lack of communication) who might be involved.  If someone does miss a comm, then typically the flight waits a few seconds and the next guy in line makes his radio call with the lead noting the person that was skipped.

Tactical call signs change with each flight, and may or may not have any real significance to the event being flown.  Funny ones are usually best; i.e., Camel works really well if you want to Alpha check a point called "Toe".

Here's a typical scenario: While practicing a 2v1 in the MOA (military operating area), Camel 1-2 gets a HYD caution, and has to stop the fight.

Camel 1-2 initiates with, "Camels knock it off, knock it off."

Next the flight reports back in order:

"Camel 1-1, knock it off."
"Camel 1-2, knock it off." (Even though Camel 1-2 initiated it, he still reports in order)
"Camel 1-3, knock it off."

I would say that Lucas came pretty close to replicating the actual sequence.  Sure, they're out of order and they're missing the "# - #" format, but its a decent attempt for Hollywood.


Why does an elevator deflection (step) result in a nonzero short-term-steady-state response in pitch rate?

The equation is certainly oversimplified, hence the name 'short period': it only models short period pitch oscillations. In this model, there are only two states: pitch and pitch rate. Any other effect is thus neglected.

A step response in an elevator would in the short term definitely lead to a nonzero pitch rate, as the model predicts. In reality, the pitch rate will usually decay to zero, because the airspeed drops to zero (there may also be altitude density effects). Imagine what would happen if you would pull on the stick in an aircraft, and crank the throttle to make sure the speed does not decay. You would do a vertical loop, exactly like the $q$ term predicts.

Of course, then you run in to an extra complication: your model is linearized. The concept of large angles, let alone a loop, does not exist in the linearized world. Think of a linearized pendulum: that works fine for small angles, but as far as the model is concerned, a 360° angle means just a very large deflection, and not the reality of returning to zero deflection after a full loop. The model is then only valid for the small amplitude oscillations it is intended to predict.

A phugoid mode exchanges speed for altitude and vice versa. Neither of these states are represented in  your short period linearized model. This behaviour is impossible to see in your model. You might as well ask why you don't see the effect of the Moon position in your model; it's simply not in the state space!

A long story short then: simplified models like these are great tools, but cannot and should not be used outside of what they are supposed to do. If you want to estimate instantaneous pitch rate from elevator deflection then this is the model for you. If you want to check for trim conditions, large attitude deviations, or even roll behaviour, then you need a better model.


Does the USA government operate any business-jets with mid-air refueling capability?

Does the USA government operate any bizjets with mid-air refueling capability?

Yes. According to this article, it's being used by the Air Force and the Navy for autonomous air-refueling tests.

  As a surrogate for the carrier-based drone, the Lear is assessing its autonomous refueling capabilities and performance for both Navy and Air Force aerial refueling techniques.

This particular Lear in the photo was active just last week:

This looks like a test to me.

There is also this, but it doesn't have the probe.


Why is there a minimum altitude for at least some high-speed jet engine restarts?

Generally when you see those kinds of limitations it means that the engine or airframe developer had trouble getting successful, repeatable relights outside of the published envelope during development flight testing and you do see it with other engines (the CF-34 that I am familiar with has a similar but much less extreme limitation).

In that case it is probably related to density/velocity of the air flow into the burner can during windmilling and I would imagine that there were issues with getting a successful lightoff every time, or excessive peak ITT during the start, or maybe surging problems or something like that.

You'd have to talk to a Honeywell person for those details.


What is the maximal acceptable delay between pilot's input and flight control surface actuation?

Excessive phase lag is a direct contributor to Type I Pilot-Induced Oscillation (PIO). Phase lag comes from:

Rigid body dynamics of the aircraft (e.g. delay between elevator surface and pitch rate response)
Actuators (finite acceleration time between input and desired surface angle)
Structural compliance (e.g. cable friction)
Transport delay in signals
Finite computational bandwidth (e.g. loop closure bandwidth)

From NASA Report 4683, PIO susceptibility can be expressed assuming the pilot is compensatory; that is, the pilot input and the aircraft response would be exactly in phase, except for a constant time delay (across frequencies). This model is expressed as:

$$G(s)=\frac{K}{s}e^{-\tau_e s}$$

where $\tau_e$ is the effective time delay, or equivalently, phase rate as a function of frequency

From its research, it found that an effective time delay larger than 0.3 sec leads to PIO issues. Given a typical pilot time delay of 0.2 sec, this would imply an upper bound aircraft effective time delay of 0.1 sec at higher frequency (around 5 rad/s), end to end.


Where can I find (or how can I calculate) the glide ratio for a PA-28-181?

If you were to take off from an airport at 2,000' ASL on a standard day, and climb to 7,280' ASL you would be exactly 5,280' above the ground which means exactly 1 statute mile above the ground.

If you were to cut the engine, and then use the information available in the chart, you should be able to glide about 10 statute miles which yields about a 10 to 1 glide ratio.


How does the angle of attack vary in turns?

Just to avoid some confusion that I feel in your question:

It doesn't!

That is, it doesn't happen by itself. The pilot or autopilot must actively pitch up (and possibly do other adjustments, e.g. increase thrust). Without active control, the angle of attack will stay about the same (initially), and the airplane will start descending if it enters a turn, because the lift becomes insufficient for level flight (see pictures in other answers).


Yes and No.

The definition of a stall is that the airfoil stops generating lift, which happens when the critical angle of attack is reached.

In an airplane, this happens during normal flight by pitching up until the critical angle of the airfoil is reached.

In a helicopter, aft cyclic ("pitching up" in an airplane) will only serve to make the helicopter climb and slow down until it reaches equilibrium in the new attitude.

Helicopters, however, can suffer from what is called "retreating blade stall," when the blade is at full pitch on the retreating side of the rotor:

This doesn't happen under normal circumstances, but there are four factors which contribute to retreating blade stall:

fast -- close to Vne
heavy -- at max gross weight
hot -- above 35C
high -- at high altitude

Retreating blade stall is considered an emergency, and can be recovered from by reducing power.


What are the options for renting an aircraft in the Caribbean with an FAA certificate?

You would be much better off renting the plane in the United States. It will be difficult to find a rental anywhere in the Caribbean, except maybe Puerto Rico.

You may want to read Greenspun's Flying in the Caribbean. It's a little dated but has good information.


Why does the 757 fuselage bend more on turbulence than those of other airplanes?

This is really two questions

Why does a fuselage bend?
Why does the 757 fuselage bend more than others

I'll give the simple answers here. You can go into a LOT of detail, but the detailed answers are mainly just bringing more information on design/engineering differences into the simple answers (eg composites bend/break in a different way to aluminium)

Why does a fuselage bend?

Essentially, it's because the lifting force doesn't support the entire fuselage equally. Drag and the aerodynamic forces created by the fuselage itself will also affect things, but it's mainly due to the fact that the lifting force is centred on two points of the fuselage, while the weight is spread along it

The lift is generated, primarily, in two places: the wings and the horizontal stabiliser (some is generated in the body too, but relatively little). Most of that lift is generated at the wings, which are attached in the middle(-ish) of the fuselage. Imagine balancing a ruler (fuselage) on your finger (wings), then stacking coins along the top of the ruler. The heavier the rule, and the more "lift" your finger has to provide, the more the ruler flexes.

Of course, lift isn't constant - turbulence means that over a few second the lift provided by the wings can change quite a lot. Imagine you start bouncing your finger up and down, creating "turbulence": the ruler will flex and unflex as it absorbs that changing force. This is the fuselage flex seen in aircraft.

The fuselage will also bend while landing or taking off, because you're again changing how the weight of the fuselage is supported: the weight is transferred from the wing root/spar to the landing gear. And the final obvious one is that the weight of the aircraft changes during the flight due to fuel burn etc.

Why does the 757 flex more than other airliners?

Well, for one thing I don't see any sources for this other than "I've heard that" (the links you provided are mostly hear-say too), but I have seen it stated as fact. Let's, for the moment, assume it's fact... the theory applies regardless.

The 757 will flex more than some other airliners (although likely less than some others) because of its design, construction and the build materials. The simplest explanation is that it's one of the longest narrow-body airliners.

What does that mean? Well, it means it's one of the longest, thinnest fuselages around. This gives us two causes:

The 757 flexes more than other large airliners because anything bigger than it is a wide-body aircraft, which will resist bending more than a small, narrow bodied thin one
It flexes more than other small airliners because any other narrow body is lighter and shorter than the 757, providing less force on the fuselage and requiring a smaller lifting force.

TL;DR: Flex is caused by lift acting mostly in the middle(ish) of the fuselage, while the weight of the fuselage and other forces on it are spread out along the length.

Overall, then, the 757 is on the boundary between lighter, narrow bodied aircraft and larger, wide bodied ones. Anything smaller than it weighs less so stresses the narrow body less. Anything larger has a bigger, stronger fuselage.


Is thermal expansion/contraction a major design problem for large subsonic airplanes?

Not thermal contraction but condensation of vapor is a problem.

Immediately, fuselage pressurization is the far bigger problem that comes with the altitude changes. But if you operate in hot and moist weather, the moisture in all the air carried inside the fuselage will condense when this air cools down at altitude and will collect somewhere. If no proper drains are included (remember, drain valves and fuselage pressurization do not mix well) and maintenance is sloppy, this accumulated water can weigh several tons.

A special case are foam sandwich structures. PVC foam is the standard in composite gliders, but airliners use honeycomb sandwich structures. When fairings made from PVC foam were tried on airliners, it was found that pressure and temperature cycles damaged the sandwich core pretty quickly. The moisture inside the cells would condense, the cells themselves would crack and bacteria would munch up the soggy remains. Only with honeycomb cores could the sandwich be made durable enough for airliner use.


An airway (Victor or otherwise) is just a standard route for aircraft to fly on in the national airspace system - for all practical purposes they are literally highways in the sky (with the lanes being stacked vertically rather than horizontally).

This is part of the paradoxical logic of how ATC provides separation services for IFR aircraft: "You have to put them together to keep them apart." -- In an environment with no radar, or in crowded airspace, having everyone following a standard routing ensures that you know what each plane is going to do. If you have 10 aircraft all flying along an airway and each separated by altitude or time you know they won't hit each other

We define the attributes (width, minimum altitude, etc.) of a victor airway mainly for purposes of obstacle clearance:

A VOR has a specific degree of precision in its measurement, and if we assume the maximum distance from the VOR (the widest degree of arc) and the maximum allowable "slop" in the VOR receiver/indicator in the aircraft that means an aircraft that thinks it's "on the airway" will be somewhere within a given width around the defining radial: For Victor airways that width is 8 nautical miles - 4NM on either side of the centerline radial - or 4.5 degrees if the VORs are more than 102 nautical miles apart.
Those numbers may sound  like they're arbitrary, but they aren't: If the VORs are exactly 102 nautical miles apart then the width of the airway at the 51 nautical mile midpoint between the two VORs is - you guessed it - 4 nautical miles. The further apart the VORs are the wider the center of the corridor becomes, accounting for the fact that a degree of arc gets wider as you get further from the VOR.

Airways are an IFR construct so if we continue on the assumption that the plane is in the clouds and the pilot can't see anything then within the airway corridor the aircraft needs to be clear of any obstacles (towers, trees, etc.), and of course it needs to be able to receive the VORs that define the airway. The combination of those factors and a few others will determine the minimum altitude at which a given airway can be used.

Note that much like ground highways airways are not always the most direct or convenient way to fly from one location to another. In particular the Victor airways are defined by VOR radials (or the intersections of such radials), but they're not always a straight line between two VORs.
As an example, take a look at this utterly contrived flight plan for the purposes of illustration: The airway I picked (V451) will take me from Groton VOR (GON) to La Guardia VOR (LGA), but it bends in three places on this route: CREAM, KEYED, and NESSI (not labeled on the sectional, but its the bend southeast of Bridgeport). A straight line between the two VORs would be the 265 radial from Groton direct to La Guardia: A much shorter distance, but not a "standard" airway routing.


What is the difference between slice, segment and leg?

I'm pretty sure those terms are not used consistently across all organisations in the air travel industry.

They are not defined in an IATA glossary I looked at but I did find this:

  Definition of Flight Segment

  The International Air Transport Association (IATA), the international trade body for airlines around the world, defines a flight segment as the operation of a flight with a single flight designator between the point where passengers first board an aircraft and the passengers' final destination. A flight designator includes an airline code, which has two letters or a number and a letter in combination, and a flight number of up to four digits. A flight segment can include any number of stops where passengers board and deplane the same aircraft operated by a single airline.

  Comparison of Flights and Legs

  A flight is defined by the IATA as the operation of one or more flight legs with the same flight designator. Unlike a flight segment, a flight may involve one or more aircraft. The IATA defines a leg as the operation of an aircraft from one scheduled departure station to its next scheduled arrival station. A flight segment can include one or more legs operated by a single aircraft with the same flight designator.

From eHow


Don’t seats that recline flat defeat the purpose of having seatbelts?

I'm not sure that comparing car seatbelts to airplane seatbelts is that useful here. The acceleration involved in a car crash at highway speeds are much greater than even the acceleration, mostly vertical, involved in even severe turbulence.

For example, after a 2015 severe turbulence encounter, investigators determined: "In the first event, the peak vertical acceleration forces recorded were + 1.7 and + 0.14 g. In the second event, peak vertical acceleration forces recorded were + 2.21 g and −1.32 g," not that much greater than the kind of acceleration you might feel in a car if you drive really aggressively. That's enough to throw unrestrained passengers and objects about (just as if you slam on the brakes in a car), resulting in injury, but it's a much smaller acceleration than what you'd see in a 30mph car crash. Nobody would consider being slammed against their seat belt like that, whether they're seated upright or reclined, to be enjoyable, but it beats slamming your head into the ceiling.

Forces much larger than that exceed the design load limits required for the aircraft, and once you're beyond that and the required safety factor, your biggest worry is the structural integrity of the aircraft, and you're less concerned about whether people's limbs flailed about.

In the case of an actual crash (such as the 16g standard new airplane seats are tested to), lying flat could pose a much larger risk of injury, but that's beyond the design specifications of the seat, which are tested with test dummies in a normal upright position. There aren't a lot of survivable crashes that occur without warning during the cruise phase of flight (page 22).

Car seats can also be reclined, and the diagrams the NHSTA produced of the results of crashes in those cases (see, for instance, page 41) are remarkably similar to yours. This is why "bring your seat to the upright position for landing" is a standard requirement.


Why does An-225 have anhedral wings though it is a cargo aircraft?

Anhedral wings will induce roll instability and improve roll maneuverability.

In a large/heavy airplane with a high-wing configuration there is usually excess roll stability, so this type of wings can be pretty common.

Both the high wing configuration and wing sweep contribute a negative sideslip-induced rolling moment, and anhedral is necessary to limit this moment. If sideslip causes strong rolling, the aircraft will have a tendency to dutch roll.


How are the wing control surfaces configured for takeoff?

Based on environmental conditions (runway length, wind, temperature, etc.) a takeoff flap/slat setting is selected by the pilot prior to takeoff to provide for the required aircraft takeoff and climb profile.

Changing the shape of the wing by deploying takeoff flaps/slats allows the wing to generate greater lift at a slower speed.  Once the aircraft is airborne, as the airplane is accelerated, the flaps/slats are gradually retracted.


One would be the Aurora Flight Sciences Perseus, which started as an unmanned instrument carrier for flights into the south polar vortex, in order to study ozone depletion.

But guess what: Development took much longer than initially expected, and funding gaps could only be filled with DARPA money. In the end, military contracts keep many high-tech companies alive which could not support themselves exclusively with civilian money.

If your field of interest has military applications, it will be very hard to stay true to your ethical standards.

I would dispute your claim, however, that all advances take only place in the military field. Apart from GPS, many advances which make UAVs practical are connected to civilian-driven technological progress. Only when it comes to issues like reserving airspace for UAV operations, the military is in a much easier position than civilian operators which must wait for slow-moving government bureaucracies to adapt to progress. The discussions we had with the FAA in 1990 on how to operate UAVs were surreal.


Are the jet blast fences positioned other way around in this video?

They're being used in a different way than normal in that case.  That's just a taxiway, not an engine run-up pad, so they aren't there to deflect max thrust jet blast.  They've been arrayed "backwards" to kind of trap debris that gets blown toward the building as aircraft taxi by.  That's my guess anyway.


Is there a 3rd-party API for aviation weather forecast, which includes additional cloud information?

Short answer:

I wish this information were available, but what you are looking for is simply not available.

Longer answer:

  There has to be something out there else how would pilots know to
  climb to a destination altitude to get above the clouds?

You are looking for data that you rightly think should exist. I would that it did, but it doesn't. Thats where the art of airmanship comes in. The answer to your question I quoted above is a complex mix of years of experience reading the weather charts, eyeballing the view out the window, and networking through the radio.

Real world weather is too hard to predict, and is constantly in flux. The only way to know the actual cloud conditions is to get out there and see it in the moment. The ground based weather observation stations like AWOS and ASOS do a decent job, but they are very limited and often wildly inaccurate. They only provide an assessment what is visible straight up.

PIREPS are the only partial answer you will get, and these are sparse and dated. A PIREP is only a snapshot of what a pilot observed at one place at one time.

Area forecasts will sometimes include a cloud top forecast (look for "TOP FL200" or similiar). However, a forecast—especially an area forecast which often covers half a state—is vastly different than an observation.

You've already mentioned Skew-T charts, and they do have useful data. Depending on your application, this might end up being your best bet. If you want something that doesn't have a real world aviation application (e.g. for the SIM community), you could derive your sought information from this.


Does the Reynolds number on a smaller model need to match the one of the original aircraft?

In wind tunnel testing you need to match several similarity parameters; the most well known are the Reynolds number and the Mach number.

Since the Reynolds number depends on flow speed, viscosity and physical size while the Mach number also depends on flow speed, it looks like both can only be matched when the physical size of the model remains unchanged. But when fluid pressure and temperature are also changed, it is indeed possible to get both close to the real value. This requires an actively cooled, pressurized wind tunnel.

Such tunnels are expensive and have a long waiting list, so other tunnels exist which match both parameters less well. In that case, the researcher needs to pick which is more important and select one of the many facilities in existence.

For preliminary development, it is in most cases sufficient to test at a much lower Reynolds number and then apply correction factors, just as it has been done in the early days of aviation. If, for example, you need to find the lateral stability of a design or test its spin behavior, a smaller Reynolds number is not critical. In order to trip the boundary layer where it would have its natural transition between laminar and turbulent flow, the flight surfaces of such models have artificial roughness applied at the right chord location, so the flow is made as similar as practical.


What is the meaning of "Docile pitch behavior" in the context of Pugachev's Cobra?

"Docile" means no big pitching moments over the angle of attack range. Since the control power with fully stalled control surfaces is rather small, the airframe must not create strong pitching moments, but keep a small pitch-down moment so the airplane returns eventually to normal angles of attack which allow regular flight.

The maneuver is dynamic, so the pilot needs to build up a specific pitch rate. Inertia will keep the aircraft pitching up, and the small pitch-down moment (and aerodynamic damping) will reduce the pitch rate so that the pitch-up stops when the nose is pointing straight up. What follows is the consequence of the small pitch-down moment: The aircraft slowly returns to controlled flight, and once control authority is re-established, the pilot stops the pitching motion.

By selecting the initial pitch rate, the pilot can control the maximum angle of attack, but once he leaves the flight regime of attached flow, he has to wait until inertia and aerodynamics do their part.


What were the rules for logging "simulator" instrument time in 1994 (non-full motion)?

This answer is somewhat non-responsive but may be helpful.
In the 70's I utilized training devices, both in preparation for an instrument rating, and for currency. The training device had a plotter and would tract the path flown.  As I recall it was a regulatory requirement that a CFII or an IGI (Instrument Ground Instructor) provide training for all simulated time.  It was logged as simulated instrument time, and instrument instruction received.
Simulator time on the device was not acceptable for any ratings or currency, unless an instructor was present and endorsed the logbook or other record.
As I recall, two inspectors from the FSDO also used this facility.
When I accomplished my instrument airplane rating and my CFII airplane rating, there was no concern either from the DPE who conducted the instrument checkride, nor from the DPE and operations inspector who rode along on my CFI instrument ride.
I will amend this if I am able to dig out the guidance at that time, which as I recall was not an AC, but rather a collection of Letters of Determination from FAA Legal.


What is the weight of ballistic recovery systems?

The smallest BRS listed here is certified up to 600 pounds (272 kg) of aircraft weight. That should be more than enough for a small jetpack or personal quadcopter. This system weighs about 22 pounds (10 kg), not counting anything required to install it.

As GdD mentioned, altitude may be an issue. The FAQ for a Cessna 182 mentions an altitude loss of about 300 feet, and that is with a rocket deployment.

They make systems for many different types of aircraft and ultralights, some probably smaller than the 600 pound limit listed above. You should contact them if you have a serious interest in such a system.


Why are aircraft of Russian origin not subject to frequent weighing and CG calculations like western aircraft?

Western doctrine is to keep all aircraft of one type in identical conditions. Once you change one thing, you do it for all aircraft of this type at the same time (or create a subtype). Routine weighing makes sure that the individual aircraft conforms to the type certificate.

Russian doctrine sees every airplane as an individual, and if something is changed, it needs to be documented, but not necessarily done on all other planes of that type. To every airplane belongs a (mostly) metal box with all documents, and they should tell you exactly what has been modified since it was produced. Weighing is now part of maintenance, but needs not be done if nothing has been modified.


Why do tail dragging seaplanes not exist?

It's been tried before (there isn't all that much in aviation that hadn't already been tried by WWII).  The tail float means the aircraft CG is aft of the hydrodynamic center of the main floats, and like a tailwheel airplane, the machine will be dynamically unstable, steering wise, when on the step, same as a wheeled taildragger and you will have to prevent it from switching ends with your feet the entire time it's on the water moving.
It could be a real handful to take off and land, especially when there are waves and gusty winds (and seaplanes do have to cope with crosswinds from time to time).  You have to make the rear float steerable, and you have to give it enough lateral bite in the  water to have good leverage in steering the thing when below the speed that the air rudder is working.  I don't think there is any drag advantage to 3 smaller floats vs 2 larger ones.
Traildragger advantages, like prop clearance, aren't that much of a benefit here, and since the conventional float configuration is so much easier to control, why bother with a taildragger float setup?
Ideas come along for new configurations all the time, but if you dig enough you find that somewhere in the distant past it's already been tried, and while it may have been functional, the "old" conventional way that everybody uses has been around so long because it's simply what works best.


The Rotax 912 engine uses a dry sump, and does not have a scavenger pump to return oil to the sump. Instead it uses pressure escaping past the piston rings to force the oil back into the sump.
The "burp" you hear coming from the (open) oil tank happens when most of the oil in the crankcase has been returned to the tank: the air escaping past the rings bubbles up through the oil tank.

The propeller is pulled through "forward" (in the normal direction of rotation) for a few reasons, mainly that it's the direction that the gearbox & accessories are all designed to turn. Turning in the normal direction of rotation also ensures that oil is pumped through the rest of the system, particularly the valve train.
Reverse rotation can pump air into the system which may cause problems if you try to start/run the engine immediately after. I believe the recommended procedure is to "burp" the engine a few times to re-prime the oil system if it's pulled through backwards.


I did it in 17 days - start to finish.

Did flight school in Arizona.  Before I went, I got the PPL study guide, MS Flight Simulator complete with a yoke, pedals, and throttle quadrant... and put in dozens of hours just learning the instrument scan and practicing virtual stuff.

When I got to the flight school, I already knew the parts of the plane, and what each control did.  I knew about maps and plotting courses.  I understood the physics of flight.  I knew about VORs, VASIs, NDBs... I knew about stalls and corrective procedures - from an academic standpoint.

As such, my under-the-hood training was by-the-numbers.  My seat of the pants stuff was only hampered the first few days by the awful flying conditions of AZ in July heat.

That said, I aced the written, and did my 3 required solos in two days.  I went to a flight school run by a Gold Seal licensed FAA examiner so I didn't have to depend on the FAA to squeeze me in.  And I passed.  17 days.

ONLY flew tricycle gear stuff.  No taildraggers.

Other than the serious prep beforehand, there were three main drivers for my success:

I flew at LEAST once a day - many times twice.
I wanted this more than anything I had ever wanted before.
I only had enough money and vacation accrued to be there for 3 weeks total - no more.

Best of luck!


What is this abandoned airport between Montague and Rothbury, Michigan?

The airport is Ottiger Airport (2MI6) which is closed indefinitely. I cannot find any information on when it was closed or for what reason. The last update date that I can find for the charts is August of 2006, which is probably when the airport was closed.

Apparently there is one person who is trying to revive the airport for private use according to this post on Facebook.


Is it a literal hood that's used to simulate IMC?

When you read or hear the term "under the hood" as it relates to simulated IMC, it may or may not be an actual hood. The FAA does not require a hood, instead the FAA calls for a "view limiting device." Often the view limiting device used is a hood such as the ones depicted below. However, other view limiting devices can also be used, such as glasses with an opaque coating that limits your view such as the ones depicted in the last picture below the hoods.

Checkout this "superhood" at Sporty's!

This is the type I used for my IFR certificate back in the day.

This is another type of view limiting device that can be used to simulate IMC. It is commonly still referred to as "under the hood" or as "hood-word", but as you can see these are not a hood. There is a name brand of glasses like these called "foggles." And most people refer to these as "foggles", although, these, are a different brand.


How is the airfoil of a fixed wing ultralight constructed?

There are various ways to build a wing like this. Ultimately you need something to shape the rigid form which you then pull fabric over. The cables do not provide the wing shape they provide support for the length of the wing. This goes back to the fairly early days of aircraft design for heavier than air flight,

  In 1909,Frenchman Louis Bleriot produced an aircraft with notable design
  differences. He built a successful mono-wing aircraft. The wings were
  still supported by wires, but a mast extending above the fuselage
  enabled the wings to be supported from above, as well as underneath.

Mast/cable wings fell out of popularity as spar supported wings became viable in the early days of heavier than air flight.

  As early as 1910, German Hugo Junkers was able to build an aircraft
  with metal truss construction and metal skin due to the availability
  of stronger powerplants to thrust the plane forward and into the sky.
  The use of metal instead of wood for the primary structure eliminated
  the need for external wing braces and wires

You can use wood like this. Or wood with a foam core.

(source)

You can also achieve the same goal with a metal rib assembly.

(source)

If you have the budget carbon fiber is also an option.

There are a few ways to cover the wing frame once its complete but ultimately the fabric must be pulled over the form and, in some capacity, shrunk to make it taught.

Fabric covered wings have lead to some of the most successful airplanes in history. There is quite a bit of info out there on how to work with fabric in relation to aircraft. The FAA has a nice handbook on it here and more info here.

If you intend on building something I would take a look at this site about building a Breezy. It looks like you can even get a full kit for one here.


How to correct for crosswind in VOR holding pattern without wind information?

One you are established inbound on the VOR radial note the heading you are flying to maintain that course. The difference between that and the radial is your wind correction angle. Multiply it by 3 and apply it to the outbound course heading.

To do this you don't need to know anything about the wind.  You just need to be able to intercept and track the inbound radial.

You can repeat this every inbound leg so if the winds are changing you can update your correction every 4 minutes and you always know you are on course one of ever four minutes. With the generous obstacle protection area even small errors will not compromise safety.


What does "spark plugs appear yellow at the ignition point" mean?

Use the tip residue to evaluate the combustion process
The yellow the manual is describing is the normal condition found in the top left corner:

If the plug is not the yellow/tan shown in the top left, then it will almost certainly look like one of the other pictures. This is a strong hint that what is going on inside the cylinder is not optimal, and points in the direction of the problem.


Why UA954 was diverted to Houston IAH on 25th Feb?

They told ATC they had an unknown odor in the cockpit. When ATC asked for more detail they said they had narrowed it down to the cockpit heating element. They specifically said they were not declaring an emergency.
It just happened to have occurred while they were within range of the LiveATC receiver so the transaction is on the recording (normally you can only hear ATC on the en route feeds). The recording is here. After ATC tries to raise them several times they check in at about 17:22 on the recording and tell ATC about the odor and need to divert. About 5 min later, I presume after conferring with the company, they tell ATC they are not declaring emergency but they're diverting to IAH. When asked for further details the say it's the cockpit heating element. After a few more exchanges with ATC they fly out of range of the LiveATC receiver.
Here's my transcript.

Times are per the recording (MM:SS). The recording starts at 0630Z so add that to the times listed for UTC
16:15 [ATC] United 954 change to my frequency if you're not there, 127.75
16:28 [ATC] United 954 Salt Lake
16:38 [ATC] United 954 Salt Lake Center
17:10 [ATC] United 954 Salt Lake Center
17:23 [UA954] Salt Lake united 954 checking in 350
17:27 [ATC] United 954 Salt Lake Center, roger. Welcome
17:30 [UA954] Yeah, it looks like we've got some unknown odor in the airplane. Were gonna - were either gonna go to Houston or San Fran. I'll get right back with you.
17:40 [ATC] United 954 thank you
21:54 [UA954] Salt Lake 954
22:13 [UA954] Salt Lake 954
22:16 [ATC] 954 go ahead
22:20 [UA954] Yeah, we are not, I repeat, not declaring emergency. We just need to turn to Houston for an unknown odor in the cockpit.
22:27 [ATC] United 954 roger, clear to Houston airport via direct. Maintain FL350
22:36 [UA954] Ok, 350 direct to houston, thank you. United 954
22:52 [ATC] United 954 I just want to confirm that's India Alfa Hotel. Is that what you're showing?
22:57 [UA954] India Alfa Hotel, affirmative
23:00 [ATC] 954 roger, thanks
23:07 [ATC] United 954 they're gonna want to know maybe a little bit more details. Is there something else maybe you can tell me about the odor so I can pass that along?
23:17 [UA954] Stand by
23:23 [UA954] Yeah, we've narrowed it down to the cockpit heating element is, we believe, the source of the smell. But that's the best we can deduce at this point.
23:34 [ATC] United 954 roger, thank you.
There are a few further routing exchanges before 954 flies out of range.


What is the technical role of a flight attendant?

I flew for a major airline as a flight attendant for 7 years.  The FAA requires flight attendants on board for the safety aspect of passenger service and sets the minimum number based on the aircraft's passenger capacity.  We usually flew with at least one more crew member than the minimum required by the FAA.

Our FAA mandated duties include safe boarding, including stowage of personal articles, arming the evacuation slides after the doors are closed, a safety briefing prior to departure, verification that the cabin is safe for flight, inflight enforcement of pilot instructions (usually return to seats and fasten seat belts), and to render passenger assistance as necessary for flight safety.  Same for pre-landing and de-planing.  First aid training (including how to deliver a baby in-flight) was rarely seen by the public.

Annually we would be required to attend jet recurrent training where we reviewed NTSB accident reports with an emphasis on cabin crew responses to emergencies, review of first aid and CPR techniques, re-testing of our knowledge of the location and how to use all the safety equipment on board, including life preservers, life rafts, and emergency slide procedures.  We were also briefed on any changes to FAA mandated procedures and tested on everything.

We were trained to be current on every aircraft the company flew so that we had maximum flexibility for our scheduling.  At the time I flew, this would have been B-727, B-707,B-757, B-767, DC-9, DC-9 stretch, and L-1011.  That meant we had to know the location of every flashlight, first aid kit, supplemental oxygen bottle, safety briefing kit, life raft, life preserver, safety exit, safety lighting, etc. for every aircraft type we flew.

The normal passenger service duties that passengers see such as food and beverage services, in-flight entertainment and generally trying to be accommodating, were in addition to the FAA required duties and were entirely up to the company's discretion to provide and train us for.

The FAA mandated safety aspects of flight attendant duties have become so integrated with the normal flow of a commercial flight they can go nearly unnoticed, especially for routine travelers.

And no, we weren't trained how to land a plane in case all the pilots got sick at the same time and passed out.


What is this aircraft with pipes at the flight deck windows?

In most commercial aircraft, the cockpit windows are the most easily opened/removed.

(Image Source)

Why the windows typically open is a topic for another question, but mostly it is for the crew to be able to communicate with the ground personnel and for rapid evacuation.

Some older aircraft like the 707 in the original post are used primarily as training devices. The aircraft in the original post is a Boeing 707 in Germany used for evacuation training. The most likely explanation is that they put in portable air conditioning units to be able to cool the cabin while they filled it with people. The vents are angled down so that water does not enter the air conditioning system.

Specifically regarding the aircraft in the post, this is a Boeing 707 located at the Tegel Airport in Berlin, Germany. It has a lot of history being an aircraft that was hijacked and then later smuggled back into Germany in the night by an American crew as a gift from Boeing to celebrate the city's 750th birthday.

You can read more about the Tegel 707 on this website and some more information about the hijacking of El Al Flight 219.


How to determine if flow transitions or separates from a Cp plot?

Separation happens at the separation point, when the steep pressure gradient suddenly changes to a plateau, and transition happens at the transition point when the plateau changes back to a steep pressure gradient. Reattachment is a little harder to discern: Here the slope of the pressure gradient, which is quite steep right past the transition point, changes back to something close to its inviscid value.

It helps to plot the inviscid pressure distribution (dashed lines) together with the "real", viscous one (solid lines), as shown below for an Eppler 502 at 3° angle of attack:

The blue line shows the pressure coefficient on the upper side and the red one on the lower side. On both sides there are laminar separation bubbles, but the one on the bottom is much bigger, so I will focus on this one. In a way, the plot lines, or more precisely the difference between inviscid and viscous pressures, mirror the behaviour of the boundary layer: With the separation the boundary layer thickens as the outer flow lines move away from the wing contour. With the transition the flow lines bend towards the contour again and at the reattachment they continue to follow the contour.

Detail view of the plot above.


Why can military aircraft descend below the DA / MDA during an instrument approach?

The most simple reason is the military has its own set of flight rules (AFI 11-202, OPNAVINST 3710.7U) that for many years duplicated many of the applicable FAR/AIM regulations. In addition, the varied mission sets and training scenarios the military operates under sometimes require them to do non-standard things, so there are a number of "carve-outs" for them to perform and regulate their own maneuvers. In general, any exception to these rules are rare, unless specifically laid out in an instruction, and likely to be used only in times of national emergency or operational necessity.

One example of a reason to descend below an MDA or DA would be when shooting a self-contained approach. A self-contained approach (SCA) or IPRA (Independent Precision Radar Approach) is one where the aircraft uses its own navigational capability (INS/Radar/Radio Altimeter) to guide the aircraft to the runway without ground-based navigational aids. Referencing the old AFI 11-202v3 AFSOC Sup, it details when constructing SCAs,

  7.4.6.5 For AFSOC SCAs and IPRAs, the MDA/DA will be commensurate with aircraft equipage capabilities and mission requirements. The applicable obstacle clearance will be maintained until descent on the final approach segment.

While practice requirements for SCAs require good weather, operational weather minimums will be much lower, and specified by the MDS-specific operations procedure. This may in some cases allow an aircraft to shoot an approach to a runway and descend below any MDA/DA on an existing approach, based on on-board capabilities.


Why don't single-engine jets suffer severe gyroscopic effects?

Well, jet engines do have gyroscopic effects.  It is a major concern in the design of the turbomachinery.  When the plane pitches/yaws, the resulting gyroscopic moment causes the compressor and turbine blades to move closer to the case.  If excessive, this can cause the blades to rub into the case, causing loss of performance.

As to why the plane is not affected by the gyroscopic moment of the engines, let's compare a few numbers.

Take a typical WWI era plane such as the Vickers FB19 powered by a Le Rhone 9J.  The engine has a mass of 146 kg, the majority of which is rotating and produces 110 HP. The plane has a maximum takeoff mass of 675 kg, which includes the engine.  The rotating mass is a fairly sizable fraction (~20%) of the mass of the plane.  Therefore the gyroscopic effect of the engine has a big impact on manueverability.

Now compare that with an F16 powered by an  GE F110 engine.  The high pressure spool of the engine has a mass on the order of 200 kg (the whole engine is about 2000 kg and the high speed rotating spool is about 10% of that... sorry I don't have a specific reference).  The max takeoff mass of the plane is about 19,200 kg.  The rotating mass is only 1% of the total mass of the plane.  So the gyroscopic effect is not so important. i.e. compared to the moment required just to turn the plane itself, the gyroscopic moment is not large.

Further, to be more precise, the gyroscopic moment is not actually proportional to the mass, but to the mass moment of inertia, which is proportional to radius squared.  A lot of the rotating mass of an older rotary engine was at a fairly high radius, whereas a lot of the rotating mass of a jet engine rotor is at a fairly low radius.  Although I have not done the calculations, my guess is that a modern fighter jet engine spool probably has a lower moment of inertia than a WWI rotary engine, despite the higher mass.

Edit:

In response to the comment by J Walters, let me try to make this a little more precise.  The moment required to perform an angular acceleration is $M=I\alpha$, where $I$ is the moment of inertia.  Let's assume that the plane is a rod (length >> width or height).  That's not totally correct, but it's good for an order of magnitude approximation. Then from this formula, $I=(1/12)mL^2$.  So for the FB19, the moment of inertia is $(1/12)(675)(5.54^2)=1726 kg-m^2$.  For the F16, $(1/12)(19200)(15.06^2)=362885 kg-m^2$.  So, comparing these two, the moment that the control surface have to apply to turn the plane (at a given angular acceleration) is 200x higher for the F16.

Now, let's look at the moments due to the gyroscopic effect. The gyroscopic moment is $M=J \Phi \times \Omega$, where $\Phi$ is the angular velocity of the aircraft maneuver and $\Omega$ is the spin angular velocity of the engine, and $J$ is the polar moment of inertia.  I said before that I expected $J$ for the F16 to actually be lower due to lower radius, but let's just assume they are the same.  The Le Rhone spins at 1,350 RPM.  I don't know exactly, but I know the F110 high pressure spool top speed is between 15,000 - 20,000 rpm.  So the gyroscopic moment is about 10 - 15x higher for the F16.

And as Peter Kampf pointed out, the aerodynamic forces go up too. The FB19 had a top speed of about 100 mph whereas the F16 can hit 900 mph at sea level.  From NASA's excellent series, both lift and drag scale with velocity squared.  So the aerodynamic forces are 81x higher for the F16.

So, in summary, yes, the gyroscopic moment is one order of magnitude larger on the F16. But everything else that the plane has to deal with during maneuvers (the moment of inertia of the plane itself, aerodynamic forces), are two orders of magnitude higher.  So the gyroscopic forces are less relevant in comparison.


What is the best procedure for landing at my destination if I have a full electrical failure at night?

Here's an investigation report on this very sort of thing in Canada.  Note that the standard procedure to alert ATC that you have a total electrical/comms failure is to fly a left hand triangle twice with 2 minute legs, every 20 min.  If they can see your non-transponder target they will quickly get the idea, and then make allowances for whatever you do next  As with IFR comm failure procedures, you should be careful to make the "next" thing you do the most logical thing for the controller to expect.
If there was an operational controlled airport with lights that was the only safe place to go to get down in one piece, I would proceed there doing the triangles, then when in visual range of the tower do another triangle until I got the flashing green light from the tower. And if I didn't get the light, and I was running out of fuel, I'd just go ahead and land.
Important thing to remember in aviation is that the regulations aren't a suicide pact, and once it's life or death, you do what ya gotta do, end of story, and while you may have to do a lot of report writing, if you crossed some lines taking reasonable action to save yourself and passengers, you won't get busted for that - hopefully.
If you're stuck with no other airport to go to with lights, and your darkened destination is the only option, well, you kick yourself for being so foolish as to fail to make allowances for that eventuality (which is not really that improbable), take your chances, and hope it turns out.
Of course, it is the early 21st century, so you should have your phone with you no?  So unless you left it behind or the battery is dead, call somebody. The destination airport operator to turn the lights on.  Someone you know there that can light up the runway with a few cars.  An air traffic control unit.  911 even.


What licenses / permits are required to perform slingload operations in a helicopter?

This one I found in the FAA Helicopter Instructor's Handbook

In the United States, FAR Part 133 covers this.  For the Flight Crew, you are required to obtain either a commercial or airline transport pilot certificate - rotorcraft helicopter with additional ratings for external load carriage.  This rating can be obtained only at the behest of the chief pilot licensed for external loads and under the employ of an operator holding an external loads certificate and requires both a knowledge test and a practical test as prescribed in Part 133.

The helicopter in question must hold a valid restricted category airworthiness certificate and must have been designated for the carriage of external loads on its type certificate or by STC per Parts  21, 27 and 29.

The operator must hold a current Rotorcraft Helicopter External Load operator's certificate which must be renewed every 24 calendar months.


What's required for a plane certified to fly to Antarctica?

I'm not aware of any specific 'certification' for aircraft operating to/from Antarctica. The air operations to/from Antarctica varies greatly depending on the location of the airstrip and season.

Actually, there are airports in Antarctica that can handle 'conventional' aircraft (atleast seasonally), like the Union Glacier Blue Ice Runway, which has been certified to handle commercial flights. US Army CRREL Report 93-14, Notes on Antarctic Aviation identifies three broad flight categories:

  Long trans-ocean flights to and from well developed Antarctic airports.
  Medium-range flights to and from short substandard Antarctic runways with limited facilities.
  Long trans-ocean flights to and from expedient runways that are rough or soft.

According to the type, the aircraft requirement can vary significantly. For example, for the first case, (long range) civilian and military aircraft maybe more than enough. From the same report:

  For flights of the first category, exemplified by Christchurch to McMurdo in springtime, any conventional trans-oceanic transports, civilian or military, should be satisfactory as long as they have adequate useful range, with the ability to reach an alternate or to return to the point of departure, arriving with standard IFR fuel reserves.

  For medium-range flights to and from short substandard Antarctic runways with limited facilities, the aircraft can be smaller, but it has to be capable of safe over-ocean journeys, with appropriate range and engine-out performance.

  For long trans-ocean flights to and from expedient runways that are rough or soft, the aircraft requires both long range and robust, high-flotation landing gear.

The report also lists the desirable characteristics of aircraft for operations in Antarctica, which should explain why aircraft like C-130 and DHC-6 are used the most:

  General configuration: High wing; high engines; tee-tail or high tail; low belly; spacious flat-floor fuselage; large doors (tail ramp,side hatch, swing nose).
  Engines: Multi-engine; gas turbine (free turbine turboprop; turbojet or turbofan).
  Landing gear: Wide stance; short legs; low ACN/LCN; large tires; soft tires; multi-wheel, multi-unit assemblies; large wheel-well fair ings (for big wheels or ski retract).
  Speeds: Reasonable cruise speed; slow approach; low stall and landing speed.
  Robustness: Strong airframe, tolerant to vibrations; reliable engines and fuel system; rough-field landing gear; good hydraulics; instruments, avionics and electrical systems resistant to vibration.
  Maintainability: Easy access to problem areas and parts that need frequent changes; spares inventories based on failure probability, easy troubleshooting; access to additional spares at reasonable speed and cost

You can see where this is going. The aircraft used in Antarctica are varied, with anything from C-17 Globemaster IIIs to re-manufactured DC-3s in service, De Havilland Twin Otter being one of the most popular. You can see that most of the aircraft operating from there are high wing aircraft with excellent STOL capability. The report also lists some of the aircraft most suited for operations in Antarctica.

Aircraft with characteristics that are appropriate for Antarctic internal operations; Image from CRREL Report 93-14, Notes on Antarctic Aviation by Malcom Mellor

Most of the aircraft look similar with high wing with wide, short landing gear and multi-engined. Quite a few of these are excellent STOL aircraft too. Obviously, they will be modified with the required navigation equipment and long range fuel tanks (for example, with long range fuel tanks, the range of Basler BT-67 is extended to ~4000 km).

Operating in semi prepared fields require the aircraft to be equipped with skis- like the Lockheed Martin LC-130J. These aircraft have the provision for carrying out JATO operations. A number of smaller aircraft (like the Basler BT-67) are equipped with skis as well.

LC-130 skis, By NSF Contractor - US Antarctica Program Common Share Servers, Public Domain, https://commons.wikimedia.org/w/index.php?curid=5883002

Aircraft operating in Antarctica should also consider the effect of air operations on the fragile and unique environment. The long range of aircraft come in handy as this limits the need for holding fuel reserves at the Antarctic airport, reducing infrastructure requirements and ecological impact.

The aircraft operating to/from Antarctica have, in addition to the usual requirements, items like onboard stairs:

  The A319CJ is designed with ultra-long range tanks, enabling the aircraft to return safely to its original port without the need to land and refuel. .... Skytraders limit the need for extensive ground support infrastructure by equipping its aircraft with specialist remote field functions such as its onboard stairs.

Though quite a few types of aircraft can (and have been) operated in Antarctica, it should be noted that not all of them are equal. A good example would be the conclusion of the inquiry into RNZAF Boeing 757 that landed below published minima at Pegasus Field in 2003:

  ... a whiteout landing. However, in the event of this occurring the likelihood of injury was significantly greater for the Boeing 757, with its long landing gear supporting low-slung engines on a low wing, than it was for the Hercules with its rough-field landing capabilities

This, in addition to the additional navigational aids (TACAN) fitted in the C-13Js. It should be noted that RNZAF still flies 757s to Antarctica.


Do mono spar wings need compression strut(or ribs)?

The wing in your picture has a tubular spar. In addition, smaller tubes are used at the leading and trailing edge, and one is running diagonally through the inner half to add in-plane bending stiffness.

Tubes have the same stiffness in all directions, so using a tube gives already some in-plane and torsional stiffness. For the outer part of the wing in your picture, this stiffness seems to be sufficient to not use drag or anti-drag wires. Since loads accumulate from tip to root, the root has the highest loading, and here a bracing tube is added in the inner wing so in-plane stiffness and strength are sufficient. I expect that this wing also uses bracing for the out-of-plane loads, and I checked with the manufacturer's home page: Yes, it does.

Kolb Fire Star II side view, from the manufacturer's home page.

The ribs are supplemented by half ribs placed between the full ribs, so the forward part of the airfoil, where more aero loads and more curvature require more support, is adequately shaped and strengthened. The ribs themselves seem also to be made from rather thin tubes, and this being a rectangular wing, need only a single jig to be manufactured. An N-type truss allows the ribs to transmit shear to the spar.

In all, this is a very efficient and pragmatic wing design. There is nothing missing (well, except for the fabric covering, of course)


There are two reasons: the market changed, and seat economics favor larger aircraft.

The NG models were designed in the early 1990s, before much of the dramatic change in the air transport market wrought by deregulation and ascendancy of LCCs. Southwest for example, was using high frequency of narrowbody aircraft to attack the network carriers and drove the extinction of widebodies in domestic US air travel. Since the early nineties, airline traffic has more than doubled depending on how you count, and there is a maximum frequency that is appealing to travelers. If you have four flights a day on a particular route and you double traffic, you might decide that six is enough and use larger aircraft.

This is what Southwest is now doing, replacing -700 aircraft with Max8s. The Max8 acquisition and operating cost is only about 10% higher than the -700, but its passenger capacity is 25% greater. The math makes the smaller aircraft unusable, given that market demand now supports the larger aircraft. Ryanair came along later than Southwest and went straight to the lower seat cost of the larger aircraft. This is why even smaller aircraft like the Cseries are in trouble, forcing Bombardier to sell half of the program to Airbus for nothing.


Can an airliner land safely using only propulsion control?

Some airliners have in fact landed more or less successfully using only engine power for control. The 2003 DHL attempted shootdown incident is an example.

A major difference between United 232 and Fullerton's landings you cite is that Fullerton was working for NASA testing a system designed specifically for the purpose of assisting pilots in controlling an aircraft with power alone. United 232 had no such system. See https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-041-DFRC.html


Has a Russian Tu-95 ever had to make an emergency landing in Europe?

Not that anyone knows of. A couple of Bears have crashed within Russia's borders.

They usually fly over international waters only, so if one did go down there would be a chance it would sink without a trace.


This constructive solution can be dictated by a number of reasons:

Aerodynamics - for AN 225, 747 Shuttle Carrier Aircraft, A-10 (control surfaces are more effective outside turbulent air);

Some sort of redundancy - for military airplanes F-35, A-10;

Easier construction - since the surface being smaller aerodynamic loads are smaller the structure can be lighter wight;

Radar cross section - F-35, SR-71;

Stability considerations: the arm for the vertical surfaces is a little longer than the arm of a potentially single surface on the longitudinal axis of the aircraft, so the two vertical surfaces combined can have a less surface area than a potentially single surface.


Are taxiways numbered in a predictable order?

In the U.S., taxiway number/nomenclature is generally designed in accordance with FAA AC 150/5340-18F. Also, Engineering Brief 89 available here clarifies some of the information in the AC with respect to taxiway numbering/nomenclature. The two pages shown below summarize the guidelines for numbering (from Engineering Brief 89)

Also, note the general taxiway numbering/nomenclature schema for Los Angeles International Airport (KLAX) illustrated on the bottom of this page.  The letter "A" starts the taxiway nomenclature beginning on the south side of the airport and progresses alphabetically towards the northside of the airport.  Intersecting taxiways are numbered sequentially.

Airport taxiway nomenclature can be very complex depending on the airport.  Also, as modifications are made to the ramps and movement areas, etc., effectively designating taxi routes or other areas of the airport becomes challenging.

Finally, in the U.S., there is a taxiway numbering/nomenclature methodology that is framed within FAA guidance documents.  A close comparison of the design guidance with current airport layouts and taxiway numbering/nomenclature not only illustrates the complexity involved but also reveals, in most cases, a consistency that can be relied upon and proves to be extremely useful in actual practice.

Excerpt from Engineering Brief 89 (two pages):


Could a pilot incapacitate other crew/passengers by manipulating cabin air quality/pressure?

The answer depends on what kind of aircraft you're talking about, and how much control the crew has over the pressurization systems.

For example, in theory you could very well reduce or completely shut off the air to the cabin on a 777. This could also be done by a single crew member alone. The pilots have full control of this system should say the one of the engines produce bad air to that cabin and would needed to be switched off.

As for the oxygen masks- these are for emergency descent use and have a generator that runs out after about 15 minutes. The crew bottles last a bit longer I think, but these will also have a limit, and doing any attempt to break through the bullet-proof cockpit door in those conditions I'd imagine would be very difficult, since I'm not sure you're still picking up the amount of oxygen you normally would.

For a similar situation (though not a deliberate attempt) you can read up on Helios Airways Flight 522.

For an idea of how the pilot masks look, see this video.

Source: SmartCockpit


Was the Cessna 208 developed to meet Fedex's requirements?

Evidently, the idea for the Cessna 208 existed before FedEx got involved. Cessna started with a widened and stretched 206 fuselage. It was designed to replace the aging De Havilland Canada Otters, Beavers and Beech 18 aircraft in use with bush operators.

  Marketing surveys from the late seventies concluded that a modern, large capacity, rugged single engine aircraft for sale could compete successfully...

They completed the first flying prototype and were expecting orders mainly from the target market of bush operators. However, the CEO of FedEx saw it on the cover of Flying Magazine and sensed opportunity. (Whether this is true or not, FedEx was looking for a small aircraft to replace trucks on some routes, and the Caravan came along at just that time.) Cessna made some changes such as adding a cargo pod to create the Cargomaster. The big orders from FedEx helped to drive the popularity of the Caravan.

So FedEx was not the reason for designing the Caravan in the first place, but it was a big part of the success of the design and did influence some aspects of it.


Do you have to update weight and balance charts after installing new avionics?

For the US under the FAA, Yes you do!

From the FAA WB handbook

  Changes of fixed equipment may have a major effect upon the weight of
  the aircraft. Many aircraft are overloaded by the installation of
  extra radios or instruments. Fortunately, the replacement of older,
  heavy electronic equipment with newer, lighter types results in a
  weight reduction. This weight change, however helpful, can cause the
  CG to shift, which must be computed and annotated in the weight and
  balance record.

For larger repairs.

  Repairs and alterations are the major sources of weight changes. It is
  the responsibility of the FAA-certificate mechanic or repairman making
  any repair or alteration to know the weight and location of a change,
  to compute the CG, record the new empty weight and EWCG in the
  aircraft weight and balance record, and update the equipment lists.

Generally this is done by the shop that installs them. If you as the owner/operator installs them (which you are permitted to do to some extent) you may need to have a new WB drafted up.

This is also checked at anual every year,

  The FAA-certificated mechanic or repairman conducting an annual or
  condition inspection must ensure the weight and balance data in the
  aircraft records is current and accurate. It is the responsibility of
  the PIC to use the most current weight and balance data when operating
  the aircraft.


Reason why heavy aircraft are allowed to land but not to start

What could it be that allows the aircraft to land safely but not to start?

In the USA at least, to allow takeoff, a runway must be long enough to let an airplane reach takeoff speed, decide to abort, and reach a full stop.  That's longer than just landing.
The more ancient answer is: takeoffs are optional, landings are mandatory.  Refusing permission to land would damage Twente's reputation.
Even more ancient, before aviation, a ship in distress would not be forbidden to dock and ordered to head back into the storm.  (Only because COVID is mentioned, ships suspected of carrying plague are a different matter.  See the etymology of "quarantine.")

Greg's answer uncovers the Dutch report, which quotes Meiltje de Groot hoping that the 747's could be scrapped ("ontmanteld") in situ because of lack of demand, because of COVID's reduction of passengers, at Twente because they could land there with no intention of departing.


Moment Coefficient Variation with Angle of Attack

Its most likely from the AC. When it is said the moment does not change with AoA in AC it does not imply a completely straight line, it can vary a bit but is somewhat straight as yours also is around 0.1. And that 'rule' only goes for low speeds btw. Once AoA is increased above a certain point when separations effects come into play, it will no longer be 'straight' as your graph also shows around 8 degs.

If you think the line is not straight enough, maybe your AC is not calculated exactly (maybe it just uses the rule of thumb of 1/4 chord).


Do pilots really wear "pilot's watches"?

High end mechanical pilots watches are very little use in the cockpit whether you are in a commercial airplane or a cessna 152. I love watches and I've searched for years for a watch that was a) very cool looking and b) actually useful when flying and I haven't found one yet. They usually fail on b) because their analogue chronometer and/or timer functions are very hard to interpret, and cannot be read at night. The digital readouts on the analogue/digital types are often small and rarely have lights for night flying. Some have lights that will only work when in calendar mode, which is about as useful as a chocolate teapot. Often the functions are hard to use and require a fair amount of fiddling to get them to work, which is not good when you have a high workload.

Commercial airplanes are usually so full of technology that a watch is completely redundant anyway, so for commercial pilots it's a matter of style. I'm not a commercial pilot, I fly older light aircraft with less technology, so having a watch with timer and chrono functions is handy. For this I wear a Casio G-Shock as it has a large and easily readable face, a light activated by its own button, simple to use, and very rugged. Digital kitchen timers also work very well.


Can pilots turn off warning alarms? Re: Aeroperu Flight 603

Sometimes they can sometimes they cant, how to do it varies by aircraft but generally alarms can often be silenced by acknowledging they are going off and pressing some kind of button. On my little Piper Archer the alternator under volt it just a light and can't be shut off but if my G430 throws an alarm or warning it can usually be silenced.

On the 737 some alarms cant be silenced and some can

  Cockpit aural warnings include the fire bell, take-off configuration
  warning, cabin altitude, landing gear configuration warning,
  mach/airspeed overspeed, stall warning, GPWS and TCAS. External aural
  warnings are: The fire bell in the wheel well and the ground call horn
  in the nose wheel-well for an E & E bay overheat or IRS’s on DC. Only
  certain warnings can be silenced whilst the condition exists.

A lot of aircraft display failures on some kind of annunciator panel or glass cockpit equivalent. These lights typically can not be turned off until the error is addressed (fire suppressed, breaker pulled etc.). Master Caution lights (and audio warnings) can typically be shut off through the use of a Master Caution Reset switch.

  Once notified, the pilot may cancel the master caution, but a
  dedicated system or component annunciator light stays illuminated
  until the situation that caused the warning is rectified. Cancelling
  resets the master caution lights to warn of a subsequent fault event
  even before the initial fault is corrected.

The FAA's full advice on warning and caution light design can be found here.

They shed more light on the topic in this AC

  Clearing and Recalling Visual Alert Messages. Clearing visual alert messages from the current warning, caution, and advisory display
  allows the flightcrew to remove a potential source of distraction and
  makes it easier for the flightcrew to detect subsequent alerts. a. The
  following guidance should be applied for clearing and recalling or
  storing the visual alert messages:

  (1) If a message can be cleared and
  the condition still exists, the system should provide the ability to
  recall any cleared visual alert message that has been acknowledged. 11
  12/13/2010 AC 25.1322-1

  (2) Either through a positive indication on the display or through
  normal flightcrew procedures, a means should be provided to identify
  if alert messages are stored (or otherwise not in view). b. The visual
  alert message must be removed from the display when the condition no
  longer exists (§25.1322(a)(3)).

In short, if a message can be cleared you should be able to pull it back up easily and if the problem goes away the alert should clear as well.


Why does a jet engine acquire a metallic whine when in full power?

I found the following RPM limits for the GE CF34-10E: 6325 RPM and 18018 RPM for N1 and N2 stages. At 100% power, the RPM for the N2 stage is 17160 RPM.

So basically we're looking at a rotational frequency of about 300 Hz. Well above the 20 Hz threshold for hearing, even if not at 100% power.

Where things get interesting is the fact that the human ear becomes markedly less sensitive to sounds below 300 Hz. So when the engine spins up from 200 Hz to 300 Hz, not only will the increased power probably produce more raw noise, it's also at a frequency that's more audible. But exactly how strong that effect is, is hard to describe. There's even a standard for this, specifically aimed at airplane noises!


Why didn't Boeing or Douglas make a jet airliner before the British DH Comet?

So did Canada with the Avro  Canada Jetliner, at exactly the same time pretty much.  The Jetliner was complementary to the Comet, being a shorter range intercity airplane.  It made a sales tour of the US in 1950 and was a huge sensation.  Avro Canada was ordered to set the project aside for the  CF-100 All Weather Interceptor program during the early 50s so Avro Canada had to decline US airline interest resulting from its sales tour (and a bizarre Howard Hughes/TWA subplot) and the program never really got traction after that as the company went on to put all its resources into the Arrow supersonic interceptor program by the mid 50s.  Odd that the Jetliner had its legs cut out from under it by government politics (the Jetliner was initially designed to a state-owned Trans Canada Airlines specification, who later back out) and the Comet by a fatal design flaw, so in the end Boeing prevailed anyway.

The main reason for the US lag was that jet engines were considered by private US airlines to be too immature as a technology to be used for commercial travel in the late 40s, so there was little market interest in the US until an actual aircraft was demonstrated (one factor: first generation commercial turbojets with crude fuel controllers, like the Jetliner's RR Derwents, were very difficult to manage).  On the other hand, both the Comet and Jetliner were developed as products for state owned airlines (BOAC and Trans Canada Airlines) wanting to be bold, so they were ostensibly private ventures but with a "guaranteed" state buyer for at least initial production, providing a huge leg up.

There was no US equivalent in the private airline sector in the late 40s/early 50s, only the US military, where the 707 actually got its start.


Why did the pilot flying pull back in the moments after the auto-pilot disconnected on AF447?

It's not accident speculation when it has been investigated.
The full accident report is available online with a very adequate summary on Wikipedia.
There are many reasons, but from the human factors study:

The final BEA report points to the Human Computer Interface (HCI) of the Airbus as a possible factor contributing to the crash. It provides an explanation for most of the pitch-up inputs by the pilot flying (PF), namely that the Flight Director (FD) display was misleading.
The pitch-up input at the beginning of the fatal sequence of events appears to be the consequence of an altimeter error.

The crew present in the cockpit at the time of the pitot blockage lacked experience/training, and were bombarded with conflicting warnings and indications.
As I've been reminded in a comment, they were also in darkness over an ocean with no external visual references.

A note on how human factors studies can relate cause and effect. There is a certain reaction time that we are unable to exceed, roughly it's 200 milliseconds for a trained person anticipating an event. It's longer otherwise and there are many studies on that. When a control input is put up against the various indications, and taking into account the reaction times to the different aural and visual warnings, then scientifically the probable cause can be known within reason.

From page 42 in the BEA report:

The drop in Mach also impacts the SAT and thus the true air speed and the wind speed.
In the following table, the case an A330-200 flying at FL 350 at Mach 0.8 in standard atmosphere with a 30 kt head wind is given as an example to illustrate the consequences of pitot icing that would result in a drop in Mach from 0.8 to 0.3.

During Pitot probe de-icing, the same variations occur in the opposite direction.

From the table, you can see how the BEA may have assessed that the likely reason for the initial nose up reaction by the pilot flying was to correct a ~300' altitude error.
They also say (p. 157):

The report specified that the stall was caused by inappropriate crew reactions to erroneous speed and Mach displays that resulted from blockage of the Pitot probes through atmospheric icing. The report stated that contrary to standard operating procedures, the crew had not switched on the Pitot probe heating.


What is the proper procedure to change altitude when changing heading?

TL;DR:

  Do you change altitude after the heading change, before, or during?

When flying under Air Traffic Control, you are expected to execute instructions after you receive them, following the motto Aviate, Navigate, Communicate. When receiving a turn and climb instruction at the same time, you are expected to start both, e.g.

 DELME, turn left heading 220, descend FL80

  What's the proper procedure for changing altitude when you change headings?

You do not change altitude or flight level on your own when flying IFR. When flying VFR, you should adhere to the semi-circular rules when changing your direction and end up in one of the semi-circular areas. On turn techniques that allow direction change and altitude change at the same time, see Tyler's answer.

  Is this made more complicated if you are flying Visual Flight Rules instead of Instrument Flight Rules?

Yes and No, because remember: You do not change altitude or flight level without being cleared or instructed to do so when flying IFR. Whether having to choose the correct altitude or flight level when flying VFR is more difficult than having ATC select one for you, is debatable.

Additional Information:

The rule you are talking about is the semi-circular flight level rules, which depending on the country, can either be applied West to East or North to South. Let's assume the example you have already used and differentiate between westbound and eastbound flights.

(Image Source: TU Wien)

The above picture shows that aircraft on a eastbound general track between 000° and 179° are bound to odd flight levels, such as FL210, FL230, FL250, etc.

Opposite traffic on a general track between 180° and 359° is bound to even flightlevels, such as FL220, FL240, FL260, etc.

This flight level you are bound to use is also the flight level you request in your flightplan, called the Requested Flight Level or RFL.

Imagine you have a flight going westbound and you have requested FL280 as your cruise level. You would maintain this flight level until you are cleared to descend by ATC. Even if a portion of the descent or arrival route leads in the opposite direction of your orignal track, it will be ATC who is responsible to assign the correct desend flight level, but these do not have to be necessarily following the semi-ciruclar flight level rules.

There is one scenarion where a pilot may want to initiate a flight level change due to changing jurisdiction and use of the semi-circular flight level rules, which is when crossing borders between countries that use west-east and north-south rules. If are on a westbound flight (approx track: 200° that requires even flightlevels, such as FL280 and cross the FIR border into a country with north-south rules that require an odd flight level, you would have a step climb or descent in your flightplan to accomodate this, e.g.:

[...] FIXXA UZ123 CROSS/N0265F290 UZ123 FIXXB [...]

It would still be ATC who clears you to climb to FL290 at that fix, but this way your flightplan is in accordance to local semi-circular flight level rules. Remember that when flying IFR, you never change the altitude or flightlevel unless you have been instructed or cleared to do so.

The same semi-circular flight level rules apply to VFR, just with the added 500ft to stay clear of the IFR flight levels. In most cases however, VFR does not entirely follow these rules, as the are VFR and their separation is based on visual identification and the see-and-avoid principle.

I am not familiar with airspace class B procedures, but in class C airspace, you require permissions to enter the airspace and will thus be assigned restrictions, which can be either a single altitude or flight level, an upper or lower restriction or a level or altitude band. If you are assigned either of the two latter options, you could apply the semi-circular flight level rules.

See below on an overview how other countries handle these semi-circular rules.

(Image Source: Delta Virtual Airlines - Not for real navigational use)

See also these related questions:
What is the difference between “flight level” and “altitude”?
What differences are there in Flight Level rules, internationally?


Carrier frequency and transmit power of a commercial aircraft

At what (central) frequency does an aircraft communicate with a
  control tower?

This is different for every tower, although due to the limited discrete frequencies around the globe they are repeated, generally far enough apart its not an issue. Specific frequencies can be found for US airports on either charts or in the AFD.

  Is the communication over one frequency only?

Generally every tower only has a single frequency, there are some airports or enough traffic to warrant multiple frequencies. They are often segmented by approach direction or runway.

  How much is the transmit power of the antenna? Is it per hertz?

Transmit power may vary based on airport but should be constant across the frequencies.

  Also please correct me if I’m wrong: From my readings,
  aircraft-airport communications is analog only, correct?

Not analog only, digital comms are used. For the airport environment there are systems such as CPDLC for delivery clearances and D-ATIS for digital airport information.