How often are aircraft flown by two FO's? On Air France flight 447 the captain was on rest break and the a/c was being flown by two first officers. Most other instances I know of on long flights there is a relief crew of both a captain and an FO. How common is it to have two FO's and no captain in the cockpit?

I'd say this is quite common on flights that require at least 3 pilots due to length.  The third pilot is almost assuredly going to be qualified as a first officer and this is the common staffing strategy with the US carriers that I am familiar with.

Three pilots (by US flag rules) are going to be required for 8-12 hour flights and you'll find that US carriers often will staff a third pilot even on the shorter US east coast <-> western Europe flights.  But what must the three pilot composition be?  Lets examine 14 CFR 121.543 the requirement to relieve a PIC (excepted):

  §121.543   Flight crewmembers at controls.
  (a) Except as provided in paragraph (b) of this section, each required flight crewmember on flight deck duty must remain at the assigned duty station with seat belt fastened while the aircraft is taking off or landing, and while it is en route.

  (b) A required flight crewmember may leave the assigned duty station—

  (3) If the crewmember is taking a rest period, and relief is provided—

  (i) In the case of the assigned pilot in command during the en route cruise portion of the flight, by a pilot who holds an airline transport pilot certificate not subject to the limitations in §61.167 of this chapter and an appropriate type rating, is currently qualified as pilot in command or second in command, and is qualified as pilot in command of that aircraft during the en route cruise portion of the flight. A second in command qualified to act as a pilot in command en route need not have completed the following pilot in command requirements: The 6-month recurrent flight training required by §121.433(c)(1)(iii); the operating experience required by §121.434; the takeoffs and landings required by §121.439; the line check required by §121.440; and the 6-month proficiency check or simulator training required by §121.441(a)(1);

The limitations of 61.167 mentioned above mean those under the age of 23 are not eligible to relieve the PIC. What does it mean to be "qualified as pilot in command of that aircraft during the en route cruise portion of the flight?"  The closest I can find to answer that is in 121.436 which says to be act as a PIC you must have an ATP and be at least 23 years old, have a type rating and have at least 1000 hours combined from part 121 SIC, part 91.1053(a)(2)(i) PIC, part 135.243(a)(1) PIC time.

What this means practically, is that a second in command who

holds an ATP,
is at least 23 years old,
is type rated in the airplane,
is qualified as a second in command, and
has at least 1000 hours SIC time with any airline

may relieve a PIC during en-route flight.

This is further reinforced by the remainder of the quoted portion of 121.543 that says an SIC qualified as PIC need not have any of the required checks a PIC must have (line check, 6 month sim check, etc).

At a major airline it is likely that SIC have ATPs and are type rated during initial training and most major new-hires will be older than 23.  It is also likely they have prior airline experience to give them 1000 hours SIC.  Even if they don't have that experience, they'll have it in a 18 months or less after being hired.

This means that pretty much any FO at the airline and surely any FO who has been there for a year or two is going to be qualified to relieve a PIC.  Because an FO can relieve the PIC and can also relieve an SIC, the third pilot need only be an FO.  This means our crew of three will be one captain and two first officers.

Given the economics involved and the behavior of US airlines when it comes to costs, they will staff an FO wherever they can versus staffing a captain.

To bring this full circle, back to our 8-12 hour flights to/from the US by US carriers that require 3 pilots they will almost always be flown by two first officers during the en-route portion of the flight.

I'm not familiar with non-US regs, so this might not apply.  Given that air carrier rules by the FAA are compatible with ICAO though, I'd guess that this is the common case in other jurisdictions as well.


Why do aircraft on Flight Radar 24 jump around randomly sometimes? I use Flight Radar 24 on my iPad to track friends/families flights when they are traveling (not paranoia, just curious).  I've noticed that, quite often, their plane will jump from one location to another, or jump backwards down the flight path, or zoom forward, or any other number of motions that I assume the plane isn't actually making.  (My personal favorite being when they miss the runway on touchdown and the plane disappears.  If that actually happened as often as Flight Radar 24 made it look like it was happening...)

What makes the planes do this on Flight Radar 24?  Why can't it just track the planes correctly?

FR24 relies for most of the tracks on ADS-B data. Part of the ADS-B transmissions is the position. There are three causes of the behaviour that you observe:

1). Aircraft landing next to the runway

The position source onboard the aircraft is not always GPS. Mainly older aircraft (e.g. Fokker 100) have their Inertial Navigation System (INS) coupled to the ADS-B transmitter. The INS relies not on external radio measurements but only on measured acceleration and rotation to track its position. It is usually correct at take-off, but it develops biases over time and therefore the landing appears quite often next to the runway. I can assure you that this is mostly misleading.

2). Short time track offset

In most aircraft the ADS-B position is from GPS. When the GPS loses its  position fix, the system falls back to INS. As described above, the INS position is slowing drifting from the truth during the flight, so the ADS-B track will shortly jump aside to the INS position until the GPS comes back. When short (e.g. 1 position update) the offsets appear as spikes.

3). Long distance jumps (180 NM, 360 NM)

Due to the limited number of bits available in the ADS-B messages, position is encoded in a complex format called Compact Position Reporting. It requires at least two position messages to decode the first position of a track, from that point onward, every message will constitute a position update. When no proper verification algorithms are used in the software, it may occur that a receiver station initializes the track wrongly, usually causing a jump of 180 or 360 NM.

Also note: When INS is used a the position source, the ADS-B data contains an indication that the data is not to be trusted, but that is silently ignored by FR24.


Can the center of gravity ever fall outside the mean aerodynamic chord? Can the aircraft center of gravity be outside the mean aerodynamic chord (i.e. %MAC being negative or more than 100%), at least theoretically?

I'm not an expert in aviation. All I've heard is the safe CG range on nearly all aircraft lies between 10 and 50% MAC.

Yes it can be. Whether the aircraft can fly with the centre of gravity outside this range is a different matter altogether.

When flying, the aircraft is balanced around the centre of gravity of the aircraft. Aerodynamic forces from the wing and the tail provide the balance, but up to a maximum. At some point the aerodynamic lift capacity of the tail is saturated.

In order to make sure that the balance can be achieved, the centre of aerodynamic force must be within certain limits of the centre of gravity. Or the other way around: CoG must be within certain limits of centre of lift, which is the better way to define it, making the CoG the variable.


What is the fuel burn of the APU on the CRJ900? Looking for a reference from an FCOM, AFM or other manual for the fuel consumption per hour in pounds or kilos of the Honeywell RE 200 APU on the CRJ900.

It's surprisingly hard to come with that sort of data.  It's hard to come up with a fuel burn number because the fuel burn varies widely, because the loads vary widely, between electrical loads and bleed demand.  However, it's not too hard to come up with a theoretical maximum and estimate from that.
The best way to make an educated guess is to take the baseline HP rating of the Honeywell RE200 APU used in the CRJ7/900, around 325 hp, and work out the fuel burn at maximum power from the typical specific fuel consumption of turboshaft engines, which is somewhere around .5 to .6 lbs/hp/hr.  Say to be conservative, we'll use .6 lbs/hp/hr.
So wide open, the APU will be burning .6 x 325, or just under 200 lbs/hr.  It might get close to that if you are running all of the electrics off the APU gen and both packs.
Normally however, the demands are going to maybe 1/3 to 2/3rds of that.  If it's idle, it might be burning 30-50, and with bleed loads due to running the AC packs, maybe 100-150.
So I think you could use 100-125 lb/hr as a ballpark value when you want to allow for fuel used by the APU while on the ground and providing air conditioning and powering the electrical system. Or if you just want to assume the worst case and go by that, for an hour of sitting on the ground with the APU running everything, you can safely assume it's going to use not more than 200 lb of fuel.


To what degree do airline ops specs preclude hand flying? I retired in 1999. I'm curious to what degree typical airline ops specs now discourage or prohibit doing what I used to do as a matter of course insofar as hand flying.

For example, I usually hand flew the aircraft until leveling at the first cruise altitude (FL290 or FL310 on fully loaded 747-100/200 aircraft). For the step climbs as fuel was burnt, I nearly always disengaged the autopilot and did the climb manually. At the top of descent I clicked the autopilot off, and I flew approaches manually.

Many of my fellow crew members thought it odd that I did so much hand flying, but as I would explain when asked, I didn't get to the 747 until I was 50 and didn't get to its left seat until a couple of years later, and I wasn't about to forego any of the fun.

None of the hand flying I did was prohibited by our ops specs of the time. My question is: to what degree, if any, do current ops specs discourage or prohibit the hand flying I did?

There are no Ops Specs that preclude hand flying, however company policy and operational considerations do in specific situations:

Level flight within RVSM airspace
Cat III approaches (and I believe Cat II approaches)
High workload, critical phases of flight (company specific policies here)

The FAA even came out with a SAFO not too long ago recommending that pilots do more hand flying during periods of low workload (and during training) with the goal of maintaining hand flying proficiency.


Why do outboard spoilers deploy more than the inboard spoiler on the A320? I was reading in the FCOM about the speedbrakes and ground spoilers when I came across the below lines.

The maximum speedbrake deflection in manual flight is:

40° for spoilers 3 and 4
20° for spoiler 2.

The maximum speedbrake deflection with the autopilot engaged is:

25° for spoilers 3 and 4
12.5° for spoiler 2.

Why is there a difference?

Airbus prefers simpler single-slotted flaps, which offer a weight advantage, but require higher-lift wing, which in turn slows the cruise speed. This is covered in a paper by an Airbus engineer, which I've used to answer a question about why the Airbus wide-bodies use different flaps when compared to the competition.

The single-slotted flaps are usually thicker as well, which in turn lead to thinner spoilers (so both can fit when retracted). Here's what the paper says:

  However, the reduction of the spoiler thickness increases the deformation tendency of the spoiler and the necessary higher stiffness would then result in higher weight of the spoiler parts.

The inboard flaps/wing generate more lift because the wing is thicker there, and the flaps are generally longer there. Which in turn is more suction behind the inboard [thin] spoilers. So a solution is to decrease the inboard deflection angle.

In comparison, this question about the 777 spoilers, shows that for all but one panel on each side, the deflection is uniform. This is a deductive answer. So kindly keep that in mind.

The following side drawing from an unrelated patent may help visualize the interaction better:


Why are the modulation depths of the localiser and glideslope different? Why do we use a modulation depth of 20% (for 90Hz and 150Hz each) in the case of the localiser and 40% (for 90Hz and 150Hz each) in the case of the glideslope? Why not use 20% for both?

From the book "Principles of Avionics" By Albert Helfrick:

  The amount of modulation is twice that found in the localizer. Because the glide slope does not have ident or speech audio, the percentage modulation for 90 and 150 Hz tones is increased.


In the US, will the tower likely think my aircraft has been hijacked if I taxi with the flaps down? In the US, will the tower likely think my aircraft has been hijacked if I taxi with the flaps down?
Related:
Why are flaps retracted when an aircraft is parked on ground?
https://fsims.faa.gov/wdocs/orders/ps_orders/a_7110.49d.htm

will the tower likely think my aircraft has been hijacked if I taxi with the flaps down?

No.
For the twenty-some-odd years I owned my plane, I only taxied with the flaps down (for important operational reasons), even at towered airports, and not once had anyone think I was being hijacked.
Indeed, it would be quite disconcerting (to say the least) for ATC to treat any behavior or condition not officially designated for the purpose as a signal that the aircraft has been hijacked.
For many airplane types, there are of course good reason not to leave the flaps down while taxiing. But worrying that ATC will think you've been hijacked isn't one of them.


Will Thrust on Rotor (Main) increase with altitude? Can some one please let me know,if the thrust required on the rotor head increases with the increase in altitude in an Helicopter or decreases with increase in Altitude?.

Thanks in advance,
Pawan

I presume that OP means torque on the rotor, since thrust must always compensate weight to maintain altitude. Thrust T, torque Q and power P equations for momentum theory in the hover:

$$T = C_T \cdot \rho A (\Omega R)^2$$

$$Q = C_Q \cdot \rho A (\Omega R)^2  R$$

$$P = C_P \cdot \rho A (\Omega R)^3$$

with $C_Q$ being identical to $C_P$.

At any altitude, thrust must equal weight. Air density $\rho$ decreases with increasing altitude, so $C_T$ must increase with increasing altitude which it does linearly.

Above graph from Leishman shows the relationship between $C_P$ and $C_T$, which can be approximated as:

$$C_P = \frac{\kappa \cdot {C_T}^{3/2}}{\sqrt{2}} + \frac{\sigma \cdot {C_D}_0}{8}$$

with $\kappa$ = loss factor and $\sigma$ = blade solidity.

So power required increases with $T^{3/2}$, and therefore increases with increasing altitude. Since $C_P$ = $C_Q$, torque does as well. Note that the weight at altitude has decreased due to the fuel burn required to reach higher altitude, which will compensate some of the additional torque required.


How to calculate the Glide Ratio from Drag & Lift? I know that $c_{d}=0.03 + 0.095c_{l}^2$.

What is the glide ratio?

The glide ratio for a given angle of attack is the ratio of lift to drag. Both of these are proportional to the respective coefficients (with a proportionality constant of $\frac12\rho v^2A$), so the glide ratio is simply $c_{\mathrm L}/c_{\mathrm D}$.

Practically, what you're looking for may be the maximal glide ratio. Finding the global maximum of
$$\frac{c_{\mathrm L}}{c_{\mathrm D}} = \frac{c_{\mathrm L}}{0.03+0.095 c_{\mathrm L}^2} = \frac1{c_{\mathrm D}}\sqrt{\frac{c_{\mathrm D}-0.03}{0.095}}=\sqrt{\frac1{0.095}\frac1{c_{\mathrm D}}-\frac{0.03}{0.095}\Bigl(\frac1{c_{\mathrm D}}\Bigr)^2}$$ should be a simple matter of algebra -- for the last expression you don't even need calculus, just finding the apex of a parabola.


How much water does the Emirates A380 carry in order to provide onboard showers? Do you realize that we are living in a world where you can get on an airliner and disembark cleaner than when you got on?

Video: Shower in A380 First Class

This just blows my mind.

How much water does the Emirates A380 carry in order to provide onboard showers?

570 litres, apparently:

  To cater for the showers, the airline's 489-seat A380s are fitted with
  two optional auxiliary potable water tanks installed in the centre
  wingbox, which increases capacity from the standard 1,700 litres
  (450USgal) capacity in six tanks to 2,270 litres - ie around 2.3t.

That's assuming that the 570 litre increase is entirely allocated to the showers, which may not be literally true.


What are the benefits of a pivot wing? The answer to another question mentions the rather unusual pivot wing. From an aerodynamical standpoint, what are the benefits of an oblique wing compared to a delta, a trapezoid or a forward swept wing?

Are there any other differences?

Note that I am asking about the oblique wing when it is oblique. The advantages of variable-sweep aircraft have already been discussed at length.

The pivot wing, also called oblique wing is a type of wing design that tries to minimize the drag over the entire speed range of the aircraft.

At low speeds, the main concern is the induced drag, which can be reduced by increasing the aspect ratio. That is why low speed aircrafts like gliders have very long slender wings.

As the speed increases, the induced drag falls off quickly and the wave drag comes to dominate at supersonic speeds. This is the reason why supersonic aircrafts have highly swept wings with very small aspect ratios.

One way to reduce the drag at high speeds is to sweep the wing. The velocity component perpendicular to the wing is reduced, reducing the drag.

The delta wing is a highly swept wing used in supersonic combat aircrafts. A good example is the Eurofighter Typhoon, which is a tailless delta. The delta wing provides excellent supersonic performance and has a high stall angle. However, the wing 'bleeds' energy rapidly during turns and the requires high takeoff and landing angles.

"Eurofighter Typhoon line drawing" by Inductiveload - Own work. Licensed under Public Domain via Commons.

The trapezoidal wing is a  version of high speed wing with small aspect ratio. The most famous example of the use of trapezoidal wing was the Lockheed F-104 Starfighter, which had excellent high speed performance. However, the aircraft had high takeoff and landing speeds and comparatively less low speed performance.

"Lockheed F-104C Starfighter" by Kaboldy - Own work. Licensed under GFDL via Commons.

Almost all the swept wings in use are swept towards the rear. One disadvantage of this kind of wing is the th airflow is from the root to the tip and as a consequence, the (outboard) ailerons stall before the inboard portion of wing and this results in loss of roll control in high angles of attack. This can be prevented by sweeping the wing forward. However, the bending stress in the wing root is increased due to aeroelastic twisting.

source: NASA

The issue with fixed sweep wings is that what is efficient in one regime will not be so in the other. One way to reduce the drag in all speeds is to change the sweep and aspect ratio of the wing.

The variable sweep wings change the aspect ratio by rotating a part of the wing.

"Three F-111s with different wing configurations" by Jason B from Australia - 3 Configs. Licensed under CC BY 2.0 via Commons.

The pivot wing is an extreme version of the swept wing where the entire wing is rotated. So far, it has only been implemented in one aircraft, the NASA SD-1.

"AD-1 ObliqueWing 60deg 19800701" by NASA - http://www1.dfrc.nasa.gov/Gallery/Photo/AD-1/HTML/ECN-15846.html. Licensed under Public Domain via Commons.

The main aerodynamic advantage of the oblique wing is that by adjusting the sweep progressively, the aircrafts can be optimized for drag reduction over a wide range of Mach numbers. Also, the AD-1 was designed with elliptical wing for minimizing induced drag.

However, on the downside, as the entire wing is rotated, one side of the wing is swept forward, while the other side is swept towards the rear. This means that their stalling characteristics are entirely different. On one side (forward swept side), the inboard region stalls first, while its the opposite on the other side. This makes controlling the aircraft difficult. A follow on project of AD-1, the Northrop Grumman Switchblade was canceled over control difficulties.

The aircraft also exhibited aeroelastic and pitch-roll coupling effects that adversely affected the aircraft's handling qualities at over 45 degrees sweep.
Also, the aircraft exhibited unusual trim requirements and inertial coupling. For instance, it was reported tha the AD-1 required about 10° of bank in order to trim the aircraft with no sideslip at 60° wing sweep.

Though the pivot wing aircraft had excellent aerodynamic characteristics, its poor and unusual control characteristics prevented further development.


Are the cockpit and crew rest area considered part of the cabin? A few days ago, a travel blogger wrote about smoking on a China Eastern flight, and the smell of cigarettes came from either the cockpit or the crew rest area:

  So I’m not sure who is smoking, though I have to assume that it’s
  either the pilots in the cockpit, or otherwise the flight attendants
  in the galleys and crew rests

The CAAC's (Civil Aviation Administration of China) decree #71 banned smoking in the cabin and toilets in domestic and regional (HK, Macau and Taiwan) scheduled flights, as well as smoking in non-smoking areas and toilets for international flights. The major Chinese airlines don't have smoking areas on international flights anyway.

In reality, many pilots and first officers on Chinese airlines smoke in the cockpit, regardless of whether it's a domestic or international flight. It seems that the cockpit and crew rest area are not part of the cabin according to Chinese standards.

Are the crew rest area and cockpit considered as part of the cabin according to ICAO?
Does any major civil aviation authority consider them to be part of the cabin?

Speaking as an ex cabin crew with one of the world's largest airline. I can definitely say that the CRC is part of the cabin, as safety and security checks are completed by the crew as part of cabin checks.

Flight deck if I'm not mistaken is not considered part of the cabin. However smoking is usually not allowed according to general aviation rules everywhere. Not even e-cigarettes are allowed. Why are e-cigs not allowed if they have no smoke you may ask?

Reason is that many people might see someone using an e-cig and think that it's ok to smoke, hence lighting up a real one. This has happened before.

I've even had faulty no smoking lights on flights and passengers thinking that smoking in that specific area of the plane where the light is faulty is fine.

When travelling people tend to pack so much stuff for their trips but leave the most vital thing behind - their brains!


Why fluids are forbidden in flights, while nitrate- and peroxide compounds aren't? As I know, passangers on most international airports aren't allowed to take any fluid with them into the deck.

But, for example, I can't remember for any deeper examination for nitrate- or peroxide compounds. Although they had been much dangerous, as a glass of water.

Why is it so?

First of all, your statement, that it's not allowed to bring any liquid (gels, spray cans, ...) with you on most airports is simply not true.

In the EU, any liquid must be in containers of not more volume than 100ml, and all containers must be in a transparent, close-able plastic bag of not more than 1000ml.

In the US, the rule is the same, but the limits are a bit lower for smoother numbers, like 3 fluid ounces (~90ml) and 30 fluid ounces (~900ml). (I'm not absolutely sure about this values...)

The reason behind this is... not very clear. There is a big anti-terrorism stamp on this rule, but if you question the rule, there is no reasonable answer. You can bring enough toxic substance in that bag to kill everyone on board, or even explosives to put the aircraft down.

If you ask me, the entire rule is there because the authorities wanted to make a rule to demonstrate that they are taking action. Remember that liquid baby food and personal medicine is excluded from the rule. Do you think terrorists would not abuse these exceptions? I still think this was the biggest coup ever of cosmetics and plastic bag sellers... (The latter could advertise explosion-proof bags... )

Sorry, I went a bit off-topic.

In general, it's easy to check carry-on luggage for liquids, as they (or their cans) are clearly visible on X-rays.

Explosive or oxidative material like your nitrate- or peroxide compounds are also in general banned from aircraft, from carry-on as well as from checked baggage.

However, they are hard to see on X-rays, especially if you put them into a less obvious shape. Manual inspection of your luggage would be the only way to search for these substances. In case of doubt, the staff at the safety check can do a wipe test, which means they wipe a small, special card over your carry-on (also from inside, and may be, they also check you). The card is then inserted into an analysis device, which can identify traces of forbidden substances, like explosives and drugs.

Here is a picture of a wipe test, with the analyzer in the background:

Demonstration of wipe test. Source: http://noe.orf.at

I remember flying from Zürich with a bag full of electronics. (Laptop, Laptop charger, mouse, another mouse, headphones, camera, camera charger, camera-to-laptop-cable, custom PCB, ...) and they did a very, very, really very careful wipe test.


What were the Concorde's emergency procedures for an uncommanded droop-nose extension in flight? The Concorde had a droop nose, which swung down during taxi, takeoff, and (especially) landing, so that the pilots could see where they were going without the long nose getting in the way.  During cruise, the nose was raised to the horizontal faired position, and held there by a pair of mechanical latches; the nose (as well as a heat-resistant visor that slid in and out of the nose) were normally raised and lowered by means of hydraulics, but could also be dropped by means of gravity if need be.

While obviously essential for landing, takeoff, and (to a lesser degree) taxiing, I'd imagine that the nose drooping uncommanded during supersonic cruise (for instance, due to a failure of the nose uplocks, or a nose droop actuator hardover sufficient to break the latches and force the nose down) would have been a Bad Thing, due both to the nose-down pitching moment generated by the drooped nose1 and to the windscreen suddenly no longer being protected from the superheated air flowing over the aircraft (probably in addition to some other things that I haven't thought of).

1: I've no idea if this would be sufficient to cause a loss of control if it happened during supercruise, but it could hardly have been a good thing.

As commented, reducing speed (and replanning flight) is all there is to it. From the Concorde abnormal procedures:

The nose has three positions:

Up
5° down
12.5° down

Holding the nose at 12.5° requires hydraulic pressure. If hydraulic pressure is lost, the crew can manually release the two uplocks, and the nose (and visor) would fall and stop at the 5° position – two additional jack uplocks stop the motion at 5°.


How is Calculated TakeOff Time (CTOT) calculated? This answer mentions:

  How these CTOT times are calculated is very complex, and deserves
  another question if you are interested.

I'm interested. How does it work? What is the level of complexity involved? What factors must be considered? If possible, what is the complexity class (P, NP, NP-complete, etc) of this problem?

I do not know the exact algorithm used for calculating CTOT's, but I can give you some background information about what information is used, and how pilots and air traffic controllers use CTOT's.

A CTOT, or calculated takeoff time, is a tool used within European air traffic flow and capacity management (ATFCM) to regulate the flow of air traffic through individual enroute sectors or airports.

The overall purpose of ATFCM is to prevent overload and ensure that capacity is utilised to the maximum extent possible and subsequently to ensure a fair distribution of delay.

Every area control sector and airport in Europe has a declared capacity, expressed as a maximum number of flight per hour. For enroute sectors, the capacity is determined by factors such as size of the sector, complexity of the route structure and military areas. For airports, the capacity depends on the runway and aerodrome layout, available approach types, weather etc.

For every IFR flight taking place within Europe, at least 3 hours before departure, a flightplan has to be submitted to the Integrated Initial Flight Plan Processing System  (IFPS), which is based in Brussels and Paris. The system will check that the flightplan is in correct format, and that it complies with any restrictions that may have been published, affecting the flight (for example, a certain route may only be available in a certain range of levels due to military activity).

The IFPS will process all these flightplans, and based on this information calculate the number of flights in any given sector or any given airport in Europe. If the number of planned flights (demand) exceeds the declared capacity, IFPS will start issuing CTOT's. A CTOT is a precise departure time, at which the affected flight must depart in order to ensure that, when the flight reaches the overloaded sector or airport, the demand does not exceed the capacity. This has the advantage that flights will spend their inevitable delay on the ground at their departure airport, instead of in airborne holdings. The IFPS will distribute delay fairly between flights. If an airport can handle 44 flights per hour, and there are 46 flights planned during some hour, the system will issue small delays to many flights, instead of just giving large delays to two flights. In case CTOT's are issued to flights as a result of an overload during a single one hour period, CTOT's will also be issued to flights planned in one hour before and one hour after that time, to avoid simply pushing the problem forward one hour.

In order to calculate these CTOT's, the IFPS must have access to up to date information about all flights. When submitting a flightplan, the aircraft operator includes an estimated off block time (EOBT), which is the time at which the aircraft is planned to leave the gate at its departure airport. If a flight is ready to leave its gate more than 15 minutes before the original EOBT, or is delayed more than 15 minutes, the airline must submit a new EOBT to the system, since the new departure time might result in an overload somewhere along the route. This may or may not result in the issuance of a CTOT time. Similarily, if a flight has been given a CTOT, but is unable to depart within the CTOT tolerance, which is -5/+10 minutes, the airline or air traffic control must submit a delay message to the IFPS, and a new CTOT will be issued. Obviously, IFPS must also be informed of any cancelled flights.

IFPS must also be provided with information about average taxi time at airports. The taxi time is the time it takes from the aircraft leaves the gate (EOBT) until it is ready for takeoff at the runway. During winter time especially, where de-icing operations at airports may reuslt in a very long taxi time, updating the taxi time in IFPS is very important. This is done by ATC. IFPS must know the taxi time because for each flight is only knows the EOBT time. Obviously, the system should not issue CTOT's that are earlier than EOBT+taxi time, since the aircraft would not be ready for takeoff at that time.

Air traffic controllers must depart any flights that have received a CTOT within a tolerance windon of -5/+10 minutes. If a flight is ready to depart before its CTOT, ATC must either have the aircraft wait on its gate, or some other place at the airport. At many airports, aircraft cannot be allowed to wait at the gate, because other arriving aircraft need to use the gate. It is then up to ATC to figure out what to do with the CTOT restricted flights until they can depart.
If a flight misses its CTOT, ATC is not allowed to issue a takeoff clearance. A new CTOT must be requested through IFPS, and the flight will potentially be delayed.

When a flight has received a CTOT, it is not set in stone. IFPS may send a slot revision message (SRM) if, for some reason or the other, the system has calculated a new CTOT. This can be both a better (earlier) or worse (later) CTOT. IFPS may also send a slot cancellation message (SLC), in which case the flight may depart without delay. Flights that are ready to depart within a short period of time, but are subject to a CTOT delay, can ask ATC to send a ready message, indicating to IFPS that if an earlier CTOT becomes available, the flight will be ready for it. In addition, an airline can request to swap CTOT's between two of their own flights, if the airline finds it more important than one flight arrives on time compared to another.

Finally, some flights are exempted from ATFCM restrictions, meaning that no CTOT delays will be issued. Examples of such flights are ambulance, fire fighting and search and rescue flights, and flights carrying heads of state. Flights departing outside of Europe will not receive CTOT's either, because no global ATFM system exists (yet) - but of course IFPS still has information about these flights, and they will be included in the calculations.

I hope the above gives you a better understanding of how air traffic flow and capacity management works in Europe. See this related question for information about ATFM in the USA.


How can I convert a non-ICAO (Taiwanese) pilot's license to FAA or EASA? So I'd like to know from somebody what's the process of converting a non-ICAO license. In particular, I'm trying to understand how a Taiwanese PPL can be converted to FAA PPL (I personally know people that have done it).

Taiwan is not a member of ICAO due to it not being recognised as a country due to China. So does that mean that a Taiwanese license is considered as a Chinese one and maybe that's why the FAA does the conversion?

I'd also be interested to hear about anyone who has tried to convert to EASA. I've never heard of anyone doing that.

I can't tell you anything about the EASA regulations, but there seems to be no way to convert a non-ICAO license directly to an FAA one. 14 CFR 61.75 says (my emphasis):

  (a) General. A person who holds a foreign pilot license at the private pilot level or higher that was issued by a contracting
  State to the Convention on International Civil Aviation may apply
  for and be issued a U.S. private pilot certificate with the
  appropriate ratings if the foreign pilot license meets the
  requirements of this section.

As you said, Taiwan is not a signatory to that convention, so the FAA can't issue a license under 61.75. (61.153 allows converting a foreign ATP license to an FAA one, but it also requires that the license come from a contracting state.) I couldn't find any special regulations or exemptions for Taiwan on the FAA's site.

You said that you know people who have "converted" a Taiwanese PPL to an FAA PPL, but do you know exactly what they did? My guess is that they applied for a regular FAA license, and used their flying time in Taiwan to count towards it.


Would it be viable to use jet blast deflectors as a power source? From an environmental point of view would installation of windmills just before jet blast deflectors provide enough power to power up all machinery at airports? How much of a reduction in reliance on fossil fuel sources of energy would that be? By how much would that reduce landing fees and could the energy provided at least power a mechanism that could tow All aircraft (including the Airbus A380 and the Boeing 747) during the entire taxi phase pre flight and post landing along with ALL airport machinery in busy airports like Heathrow

From an environmental point of view would installation of windmills just before jet blast deflectors provide enough power to power up all machinery at airports?

From an environmental point of view? Not sure what that has to do with providing power, but no, here's why: First, many airports do not have jet blast deflectors at the ends of runways or in a place that sees most of the jet blast.

Aside from that, windmills (wind turbines) can't spin at unlimited speed. Here's what happens one one goes too fast (small turbines have the same issue, but can stand wind speeds up to 100-ish mph). Turbines are designed such that they have an optimal output within some speed range, below that they don't generate much power, and above that they can get hot and fail, or have to be throttled back to stay in the power band.

So seeing as how you would need to have them close to the ground where they aren't useful for natural breeze, providing major power to the airport is not going to happen.

  How much of a reduction in reliance on fossil fuel sources of energy would that be?

Why do you assume that the airport runs on fossil fuels? Many airports are running "green" initiatives, installing solar panels and bio-diesel reactors. They may also be purchasing renewable energy credits so that they try to get a good portion of the power used from renewable sources, such as wind farms.

  By how much would that reduce landing fees and could the energy provided at least power a mechanism that could tow All aircraft (including the Airbus A380 and the Boeing 747) during the entire taxi phase pre flight and post landing along with ALL airport machinery in busy airports like Heathrow

Such a tow system would almost undoubtedly increase landing fees. You are looking at it purely from a fuel savings view, but lets look at it from other angles:

Cost: There would be an extremely high acquisition cost, all the taxiways would have to be reworked to include this system. Even if it were an autonomous tow vehicles, the structure is not free. The tow's have to be created, programmed, vetted, certified, etc.
Maintenance: There is a lot of infrastructure to maintain, the tow vehicles, the electronic systems, mechanical systems, etc. This requires a full-time crew, and I'm sure they aren't going to work for free, plus enough on-hand spares to be able to quickly repair the system when it goes down.
Logistics: You have to have the tow mechanisms in place to catch the aircraft as they come off the runway. This means enough tow mechanisms to tow all aircraft and transit back to the runway possibly empty to catch another aircraft.
Other issues... Aircraft can't just shut down engines right after they land. Many engines have cool-down times before they can be shut down. They also can't just fire them up at the end of the runway, there are start-up times and warm-up periods. Aircraft also need to power systems on the way to the runway, air conditioning, avionics, hydraulics, etc.

Honestly these tow systems are not economically viable at this time. Aircraft are extremely fuel efficient (although not on the ground), but they have procedures to mitigate fuel expense on the ground. They shut down unused engines, turn off anything that isn't required, and reduce power consumption.

If you are looking for ways for the airport to save energy or generate it themselves, then solar panels or these tiles that generate electricity are more viable.


Are there rules governing the conduct of flight attendants? What are the rules and regulations specified by FAA about the code of conduct of flight crew members?

And, are there any rules which specify behavior of passengers with crew members?

The FAA is responsible for safety regulations and standards, not for code of conducts or courtesy regulations for interactions between flight attendants and passengers. Flight attendants are bound to certain behaviour only by their employer and their code of conduct, additionally to any national law that prohibits insulting others or harming them otherwise.


Why don't short runways use (downhill) ramps for takeoff? This is a followup on question: Why don't short runways use ramps for takeoff?

There are multiple answers to that question that answer why an uphill ramp at the end of the runway does not make sense. But what about going the other way?

I would imagine a downhill ramp at the beginning of the takeoff roll could give the aircraft more energy on takeoff (converting potential energy to speed), and that could indeed improve takeoff performance. This would be useful at places where extending the runway is not possible.

How the aircraft would get up there is another question, but worst case scenario it could always back-taxi on the runway before turning around and taking off.

Is this practice ever used? If not, what are the reasons?

it could always back-taxi on the runway before turning around and taking off.

So ... that would limit the steepness of the slope significantly, and thus the potential benefit.

Most other aspects are already covered by Bjelleklang's answer: Landing aircraft would either have to clear the obstacle before being able to touch down, or they'd fall over the edge if they don't brake in time (rather than, as these days, get stuck in the grass behind the runway end)


Is it technically feasible to make a solar hang glider? Is there any hang glider with solar sheets on top that can charge the e-trike or the e-Lift's battery in flight ? Just like the Sunseeker...

I think you've got your terminology crossed here (but it's not your fault - your sources don't seem to clear on it either).

A hang glider is by definition a solar vehicle: They're non-motorized, and the pilot keeps them aloft by seeking thermal lift (created by the sun shining on the ground and heating it up) or ridge lift (created by wind striking the side of a mountain/hill (ridge) and being deflected up.
Both of these rely on the sun (either directly heating the local ground, or unevenly heating various parts of the Earth's surface, ultimately creating wind).

What you're referring to would be a solar-powered ultralight aircraft -- basically a hang glider with a motor strapped to it, or possibly an electric powered paraglider.

One could conceivably create a solar-powered ultralight using flexible solar cells on the wing  - in fact a little Googling reveals that it has apparently been done with an electric paramotor (a type of powered parachute) (A little more Googling reveals this wasn't as cool as I previously thought - they seem to have been using a support vehicle to recharge their battery packs (with solar cells).

As far as I'm aware no such vehicle is commercially available at this time (May 2014), but the materials and technology to construct such a vehicle are certainly available (the folks over at the Experimental Aircraft Association could probably provide guidance on building something like this), and it wouldn't surprise me if commercial or kit-build solar ultralights become available at some point in the future.


Why do cargo flight companies reposition their crew via passenger airlines? U.S. airlines prepare plans to virtually shut down domestic service amid outbreak : Coronavirus

  This will cause massive issues for cargo as well. Cargo operators use commercial airlines to reposition crews.

What exactly does 'reposition' mean here?
Why do cargo airlines need passenger ones to 'reposition' crew?

Reposition is just what it sounds like, to move a crew from one place to another, generally the move occurs in a plane other than the one they are slated to fly.

Both cargo and passenger airlines reposition crews all the time for various reasons. Some but not all reasons are:

Crews are not always required to live in the place they are based. Some crew members may chose to live elsewhere and can generally fly their carrier for free to get to their starting point of the day. Cargo airlines may have deals with passenger airlines to allow this flexibility for their crews as well.
A crew trained on a given airframe may be needed to fly a different plane than the one they just operated.
Commercial crews have duty time limits and at the end of a "shift" they may need to get home if the cargo airline does not keep them wherever they are. On the same note a crew may be needed elsewhere to start a flight.

A cargo airline may not fly as many back-and-fourth routes as a passenger airline so they may utilize airline flights to fill the movement needs of their crew. It is worth mentioning that some cargo aircraft do have limited seating that can be used to re-position a crew.

This cargo pilot describes it quite nicely in her blog:

  Or you expect to operate a flight, but it is changed to a positioning
  flight. A positioning flight is a flight you do for the company as a
  passenger, to get you to a certain destination from where you will
  operate, either straight away or after a layover, or sometimes you
  position after a duty. Positioning flights can be with the company, or
  booked with another airline. You might anticipate returning home on
  Tuesday, but when your block of working days finishes Friday, big
  chance you will get some more flights and will not return earlier than
  Friday. Due to these roster changes, you also might end up in a
  completely different part of the world. So in my suitcase I pack all
  kind of electric adapters, and even if I go to a subtropical
  destination, I still pack jeans and a jacket. I learned this the hard
  way by ending up in Alaska, while having packed for my trip to high
  summer Colombo.

Note: If commercial planes stop flying a fair bit of cargo stops moving any way.


What good reference books for aviation (ATC & AOC) systems are there? I am looking for a good reference book or research paper that describes the services and applications offered by air traffic control and Aeronautical Operational Control in detail.

Everything I have read so far just outlines briefly what these services are intended for. I need something very thorough with all the standardizations and details that are being used in current aviation systems, particularly from a communications point of view. Any suggestions?

What are the best textbooks or reference books that aviation researchers or experts use?

I'd start with the Global Operational Data Link Document published by ICAO.

It covers pretty much everything data link.  What it doesn't cover, you'll find in the referenced documents.


What safety mechanisms prevent thrust reverser deployment in mid-flight? I just came across the Wiki article on Lauda Air Flight 004, which was destroyed when a thrust reverser activated in mid-air.

In the article, it says:

  The incident led Boeing to modify the thrust reverser system to prevent similar occurrences by adding sync-locks, which prevent the thrust reversers from deploying when the main landing gear truck tilt angle is not at the ground position.

But that can't possibly be enough. Landing gear is lowered and locked while the plane is still flying. That means these "sync-locks" would be released while the plane is still in the air.

Edit: Looks like I misunderstood what "not at the ground position" meant. Apparently the truck tilt angle is not flush except when the wheels have pressed onto the ground. Nevertheless, the general question of what safety mechs there are, still stands.

Are there any other safety mechanisms? Are there any that detect, somehow, that the wheels have actually touched down? Maybe a wheel RPM sensor?

On a Boeing 777, the thrust levers need to be at their idle stops otherwise the thrust reverse levers physically cannot be moved aft. Once the thrust levers are at their idle stops and the  reverse levers are moved to the reverse thrust position there will be three signals provided to the thrust revereser actuation system (TRAS).

These three signals to the TRAS energize the thrust reverser sync lock valve
(SLV), the directional control valve (DCV), and the isolation valve (IV). At a reverse thrust lever angle of 11 degrees, the SLV is energized by closing a microswitch in the thrust lever assembly. The SLV then sends hydraulic pressure to the sync lock on each thrust reverser sleeve to accomplish release.

At 24 degrees reverse thrust lever angle, the DCV is energized by a microswitch in the control column assembly where the thrust levers and reverse thrust levers reside. The valve is shuttled by system pressure to the deploy position.

At thrust resolver angle of <31 degrees the IV is opened by a signal from the electronic engine control (EEC), and system pressure, by way of the DCV, is ported to the actuators. The IV command, from the EEC, also requires the engine to be running and the airplane to be on the ground.

Air/ground logic uses radio altimeter signals, with ground mode for the thrust reversers being < 5 feet. The locks within the locking actuators release and the thrust reverser sleeves move aft. After the thrust reverser sleeves move aft by a measure of 60%, interlock releases and the levers can then be moved to their maximum reverse thrust position.


What is the proper procedure for leaving class D airspace? So one thing that always struck me as kind of odd was when you depart a class D tower (VFR) and you get your departure instructions, that's kind of ... it. You just go on your merry way and switch off frequency whenever you want to.

Do people just stay on the tower frequency listening until they're outside of the airspace? Or do you give the tower a courtesy call (N123 leaving the class D) when you get to the boundary, and then switch off?

Or, is it legal to switch immediately to another frequency as soon as the tower says 'left turnout approved, resume own navigation'? It always seemed a bit of a hole to me. But, are controllers bothered by a extra "check out" on leaving the class D?

The AIM covers this from an operations / legal standpoint:

  3-2-5. Class D Airspace

    4. Departures from:

      (a) A primary or satellite airport with an operating control tower. Two‐way radio communications must be established and maintained with the control tower, and thereafter as instructed by ATC while operating in the Class D airspace. [emphasis mine]

While operating in Class D airspace, you must maintain two-way radio contact with the tower – monitor the frequency and be prepared to respond.

You may leave the frequency once you are either clear of the airspace, or receive instructions to that end from ATC ("N1234, frequency change approved").

Whether or not controllers are bothered by you letting them know that you've left, I can't say, but it would probably qualify as frequency congestion. If they want to get in touch with you, they'll try ("N1234, are you still with me?"), but once you're outside the Class D airspace they're generally only providing advisory information.


Would a 737 pilot use flaps in nose dive? Since flaps help lift the plane, would they deploy flaps if the plane was nosediving? And what would they do if the back pressure was too much? I know speed increases lift, but can full throttle make the plane difficult to level out?

No, flaps are never used during a nose dive.

We need to distinguish between two scenarios:

Intentional nose dive: this is actually called a rapid descent maneuver. The FCTM (Flight Crew Training Manual) has a whole section dedicated to it. The general procedure looks like this:

From the Boeing 737 NG FCTM (7.5 Maneuvers - Rapid Descent - Level Change (LVL CHG)):

  Because of airspeed and altitude protection and reduced crew workload, use of the
  autopilot with LVL CHG mode is the recommended technique for rapid descents.
  Use of the V/S mode is not recommended.

  Initiate a turn, if required, using HDG SEL. Set a lower altitude in the altitude
  window. Select LVL CHG, close the thrust levers and smoothly extend the
  speedbrakes. Autothrottles should be left engaged. The airplane pitches down
  smoothly while the thrust levers retard to idle. Adjust the speed as needed and
  ensure the altitude window is correctly set for the level off. During descent, the
  IAS/MACH speed window changes from MACH to IAS at approximately 300
  KIAS. Manually reset to VMO as needed.

  When approaching the target altitude, ensure the altitude is set in the MCP altitude
  select window. Altitude capture engages automatically. Adjusting the command
  speed to approximately LRC or 300 knots before level-off aids in smoothly
  transitioning to level flight. The pitch mode then controls altitude and the thrust
  levers increase to hold speed. Smoothly return the speedbrake lever to the down
  detent during the level off maneuver.

  When descending with the autopilot engaged and the speedbrakes extended at
  speeds near VMO/MMO, the airspeed may momentarily increase to above
  VMO/MMO if the speedbrakes are retracted quickly. To avoid this condition,
  smoothly and slowly retract the speedbrakes to allow the autopilot sufficient time
  to adjust the pitch attitude to maintain the airspeed within limits.

  When the speedbrakes are retracted during altitude capture near VMO/MMO, a
  momentary overspeed condition may also occur. This is because the autopilot
  captures the selected altitude smoothly by maintaining a fixed path while the
  thrust is at or near idle. To avoid this condition, it may be necessary to reduce the
  selected speed and/or descent rate before altitude capture or reduce the selected
  speed and delay speedbrake retraction until after level off is complete.

In case a higher descent rate or lower descent airspeed is required, the landing gear can be extended additionally to the speedbrake, but flaps are never mentioned:

  Landing Gear Extended Descent

  The rapid descent is normally made with the landing gear up. However, when
  structural integrity is in doubt and airspeed must be limited, extension of the
  landing gear may provide a more satisfactory rate of descent.

  If the landing gear is to be used during the descent, comply with the landing gear
  placard speeds.

Accidental nose dive: this would fall under the general term of upset. The recommended procedure is described in the FCTM (7.26 Maneuvers - Upset Recovery):

  Nose Low, Wings Level

  In a situation where the airplane pitch attitude is unintentionally more than 10°
  nose low and going lower, the airspeed is increasing rapidly. A pilot would likely
  reduce thrust and extend the speedbrakes. Thrust reduction causes an additional
  nose-down pitching moment. Speedbrake extension causes a nose-up pitching
  moment, an increase in drag, and a decrease in lift for the same angle of attack. At
  airspeeds well above VMO/MMO, the ability to command a nose-up pitch rate
  with elevator may be reduced because of the extreme aerodynamic loads on the
  elevator.

  Again, it is necessary to maneuver the airplane's flight path back toward the
  horizon. At moderate pitch attitudes, applying nose-up elevator, reducing thrust,
  and extending speedbrakes, if necessary, changes the pitch attitude to a desired
  range. At extremely low pitch attitudes and high airspeeds (well above
  VMO/MMO), nose-up elevator and nose-up trim may be required to establish a
  nose-up pitch rate.

Also here, flaps are not mentioned, so only speedbrakes should be used to increase drag (and increase the nose-up pitching moment).


Why does gas turbine engine have pressure oil supply tube and the scavenge oil tube? What is the function of pressure oil supply line tube and the scavenge oil tube on turbo shaft engine?

Oil Pressure lines typically sends oil to the Bearings and Gearboxes of the Engine, from the oil pump.

The Scavange lines typically collects the oil from those areas and send it back to the Oil tank, getting cooled and filtered along the way.


When replying to ATC, callsign first or last? When I was in flight school, some instructor told me that it is the unknown ICAO standard that you should reply to an ATC call with your callsign first, like this:

"XYZ123, climb FL350"
- "XYZ123, climb FL350"

But I only know one airline that operates like this. In all other parts of the world, I hear:

"XYZ123, climb FL350"
- "Climb FL350, XYZ123"

So can someone tell me the definite ICAO standard on that and where it is written down?

ICAO Annex 10 - Aeronautical Telecommunications Vol 2

When replying, you end the message with the call sign.

  5.2.1.9.2.2 PANS.— An aircraft station should
  acknowledge receipt of important air traffic control messages
  or parts thereof by reading them back and terminating the
  readback by its radio call sign.

  Note 1.— Air traffic control clearances, instructions and
  information requiring readback are specified in PANS-ATM
  (Doc 4444).

Exception to rule:

  5.2.4.4.1 PANS.— When an aeronautical station initiates
  a call by SELCAL, the aircraft replies with its radio call sign,
  followed by the phrase “GO AHEAD”.

However, local procedures should be followed if they are different. See the post, 'Is it bad practice to say my callsign first in a transmission to ATC?' for an answer about UK and Germany. Basically when replying you finish with the c/s, when requesting you begin with the c/s.


Anybody know the reason for the ‘Star Wars’ themed STARs into KATL? There are new RNAV STARs for arrival into Atlanta Class Bravo for KATL.  Does anybody know the reason a Star Wars theme was chosen for waypoint names eg TYFTR, WOKIE, NWHPE, etc?

It's a long established practice for the procedure developers to build the procedures around a theme. It helps with coming up with the necessary distinct pronounceable names for the waypoints.

My personal favorite is the RNAV (GPS) RWY 16 approach into KPSM. Flying from the IAF to the MAP and the Missed Approach Holding waypoint you fly:

ITAWT --> ITAWA --> PUDYE --> TTATT --> IDEED

which mimics Tweety Bird's comment when he sees Sylvester the Cat chasing him (for those readers who didn't grow up watching Warner Brothers cartoons).


Can I pilot a plane while having a chronic mental health condition? I want to claim to have flown, it is a dream of mine.

My medical condition disqualifies me from being a pilot. I have one of the following ADHD/OCD/depression/mania/bipolar. Is there a way I can fly as a copilot without a pilot's license?

I want something preferably cheap and not a simulator.

You have a couple of options here:

As Skip Miller said, you can take flight lessons. Up until you want to solo, you don't need a medical certificate. Often flight schools have "Discovery Flights" for a reduced cost that still allows you to fly left seat and get half an hour to an hour of flight. Careful though, its addicting.

Actual costs for this range from \$75 to over \$300 depending on the type of aircraft you are going to fly. Hourly rates for a Cessna 152 average around \$90 an hour, to a 172 up to \$150 an hour, and more sleek aircraft like a Cirrus SR-22 at \$300 per hour or more. Instructor rates go from \$35 per hour to \$65 per hour (typically) depending on the type of instruction.

Another option is to find a pilot who wants to build hours and go flying. They may let you fly the airplane around a little bit, but you'll most likely be flying right seat and probably won't let you do the more complicated phases of flight like take-off/landing and operations in controlled airspace. If you find a pilot willing to do this then you can share costs (split down the middle).

By the way don't get discouraged about your medical condition if you really want to fly. There are also a few options there too. First, you could go through the rather lengthy process with the FAA to have your case reviewed and if possible issued a special issuance medical certificate. Some of what you list are automatically disqualifying depending on the medications you may take, but the AOPA has a good read on mental health and getting medicals issued.

Second, you could get a sport pilot license, which also does not require a medical (just a drivers license). There may be hiccups with your conditions here too, so its best to talk to an AME or flight instructor before getting too deep.

Let me answer your specific question:

  Is there a way I can fly with a copilot without a pilot's license?

I take this to mean that the "copilot" is a non-pilot rated passenger. Unless you are a certificated pilot, then no. A "co-pilot" must be just that, a pilot. Otherwise they are just a passenger sitting in the front seat. Since that person is a passenger, you must be a fully licensed pilot to fly with them (students cannot take passengers).

If the copilot is a pilot rated individual, then yes, you can go flying with them (provided it is not a Part 135 flight). That person must be rated for the aircraft that you are flying and must meet currency requirements to carry passengers (you). You as a passenger are allowed to manipulate the controls under the supervision of the pilot provided the pilot is pilot in command and unless the pilot is a CFI, they are not providing instruction.


How do disks generate lift? Disks and disk-like objects (frisbees, pie pans, round cardboard piece, hats of all sorts, and many other things) can fly well when thrown along with a spinning force which creates a gyroscopic effect stabilising the object. What causes disk objects to be able to generate lift?

As with regular wings, the angle of attack and the dynamic pressure determine the lift of a frisbee.

This short paper by V. Morrison gives a short overview. If you want to dig deeper, Sarah Hummel and Eugene Motoyama (sorry, paywalled) have done more detailed work on flying discs. The following pictures were shamelessly copied from the work of Kevin Walsh. They show that the rounded edge improves airflow over the disc by delaying flow separation.

Flow around a frisbee (source)

The frisbee can be seen as a wing with an airfoil that looks the same from both directions. This incurs a small separation area at the rear end, but prevents much larger separation at the leading edge at medium angles of attack. Morrison found the farthest flying distances with an angle of attack of 12° and a starting speed of 14 m/s.

Since the center of pressure is close to the leading edge, a disc would quickly topple over due to the different locations of the center of pressure and the center of gravity. By spinning, it can be stabilized:

Difference between spinning and non-spinning frisbee (source). Inertia / gyro forces prevents the spinning frisbee from pitching up.


What are these blades on the engine cowling of a Wittman Tailwind? The Florida Air Museum in Lakeland has a Wittman W-8 Tailwind with four wooden, propeller-like blades on the engine cowling:

Source: own work

What are the blades for? It's an experimental aircraft so it's possible that they're unique to this specific airframe.

After calling the Florida Air Museum, I have discovered that this seems to be a local mystery to the employees at the facility, as well. The museum’s director assumed that they “were an attempt to counteract P-factor or torque. Something to do with balancing required power.”
Since this was little help, I did some more digging and decided that the “blades” on this Wittman seemed to function as adjustable strakes - albeit located far from any control surface and of dubious utility.
Finally, I discovered that there have been numerous experiments performed with ‘Actuated Forebody Strakes’ aimed at controlling forebody vortices as a means of complementing thrust vectoring. Additionally, a NASA study found that a large increase in yawing moment may be brought about through the manipulation of actuated forebody strakes.
In every case that I could find, the tests were concerned with fighter jet aircraft operating at high angles of attack, but it is conceivable that the owner of this Wittman W-8 was attempting to implement some of the same advantages here.
Here are the abstracts to the vortex thrust vectoring and NASA yawing moment studies:

The desirability to enhance the controllability of fighter aircraft at high angles of attack, particularly yaw control, has fostered an interest in both vectored thrust and active control of forebody vortices... The methods investigated include pneumatic or blowing techniques using surface mounted jets and slots, surface suction, variable-height deployable strakes, and rotatable-tip strakes. Flow visualization, and force and moment measurements have shown that all of the methods are effective at manipulating the forebody vortices over a wide range of angles-of-attack and sideslip, primarily through control over flow separation on the surface of the forebody. All are most effective when applied near the forebody tip.

Extensive pressure measurements and off-surface flow visualization were obtained on the forebody and strakes of the NASA F-18 High Alpha Research Vehicle (HARV) equipped with actuated forebody strakes. Forebody yawing moments were obtained by integrating the circumferential pressures on the forebody and strakes. Results show that large yawing moments can be generated with forebody strakes. At angles of attack greater than 40°, deflecting one strake at a time resulted in a forebody yawing moment control reversal for small strake deflection angles. At α = 40° and 50°, deflecting the strakes differentially about a 20° symmetric strake deployment eliminated the control reversal and produced a near linear variation of forebody yawing moment with differential strake deflection. At α = 50° and for 0° and 20° symmetric strake deployments, a larger forebody yawing moment was generated by the forward fuselage (between the radome and the apex of the leading-edge extensions), than on the radome where the actuated forebody strakes were located.

References:
Malcolm, G., & Ng, T. (1990). Forebody Vortex Control as a Complement to Thrust Vectoring. SAE Transactions, 99, 1515-1543. Retrieved August 16, 2020, from Journal of Aerospace
Fischer, D.F., Muriel, D.G., & Lanser, W.R. (1996). Effect of actuated forebody strakes on the forebody aerodynamics of the NASA F-18 HARV. NASA Technical Memorandum 4774. Retrieved from NASA.gov


How are the wing control surfaces configured for takeoff? For regular aircraft (i.e. a typical airliner), how are the wings configured before or during takeoff? Are there any adjustments needed for climb?

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.


Can someone tell me what kind of airplane this is? It says Capt Nungesser on the tail. I’ve researched him but can’t find out what type of plane this is. French?

The aircraft with the inscription on the rudder "Capt Nungesser" is the French aircraft "Potez VIII" 1922 model type, the second version, equipped with a 70 hp. Anzani engine.
http://www.airwar.ru/enc/law1/potez8.html
Here is one picture from that site:


How do you calculate the wing moment coefficient knowing the moment at each spanwise station? A lot of theoretical formulas exist for finding the moment coefficient for airfoils, but I have been confused by how to get the moments for a wing. I came up with three related questions that have been confusing me a lot:

If I know the moment coefficient at each spanwise station for the wing (so the moment coefficient for each airfoil used along the span), how can I get the moment coefficient for the whole wing? Is it just a weighted integral? If so, what's the formula look like?

How does one find the moment coefficient for a straight tapered wing?

How does one find the moment coefficient for a swept wing?

You can use the Lifting Line Theory to first calculate the downwash at each spanwise station, which are then converted to the induced AOA ($\alpha_i$).
The sectional moment coefficient and lift coefficient are:
$$c_m = c_{m_0}+c_{m_\alpha}(\alpha-\alpha_i)$$
$$c_l=c_{l_0}+a(\alpha-\alpha_i)$$
To get the total moment of a straight tapered wing (about the root chord leading edge for simplicity), it's a simple integration away, noting that the sectional moment is usually about the 1/4c of the local chord:
$$M_{LE} = q_\infty \int_{-b/2}^{b/2}{\left[ c(y)c_m(y)-\left(x_{LE}(y)+\frac{1}{4}c(y)\right)c_l(y) \right]c(y)dy}$$
where $c$ is the local chord length, $x_{LE}$ is the distance from the root LE to the local leading edge, and $q_\infty$ is the free-stream dynamic pressure. You'll have to normalize against a reference chord (e.g. MAC) to get the moment coefficient.
Finite large sweep wings have crossflow gradient that would render Lifting-Line Theory unreliable. You'd have to use a vortex surface method, such as Vortex Lattice, to derive accurate predictions.


Is an FAA Pilot License valid in the U.S. if held by a foreigner? My question is relatively simple.

Suppose I come to the U. S. and get my whole flight training over here. I hold a green card but the academy only used my Venezuelan passport for the enrollment process. Would my licenses be valid here in the United States even though I'm a foreign person?  I'm taking about the validity of my licenses regardless my status (I'm a permanent resident, green card holder)

Yes. Tens of thousands of foreigners - both inside and outside the US - hold FAA certificates, including me. Your nationality is only relevant in these situations:

Foreigners must have TSA approval before starting flight training (US citizens need the approval before soloing). See this question.
Getting the TSA approval might be more difficult for people from certain countries (this is mainly a security/political issue, not an aviation one)
An FAA certificate isn't an immigration document: it doesn't give you any right to enter the US, or to work here. That means, even if you hold an FAA commercial or ATP certificate, you still need a work visa or green card in order to work as a pilot in the US. See this question.

But once you get an FAA certificate, your nationality is irrelevant. The FAA only cares about your license being "valid" in the strictly aviation sense: is your medical current, is your flight review current, is your instrument rating current etc.?

Even if you surrender your green card and leave the US permanently, that won't change anything about your FAA certificate (unless maybe you get expelled and the DHS requires the FAA to revoke your certificate on security grounds). You just send them your new address in whatever country you're in, they update their airman database, and that's it.


Why aren't passengers sorted before embarking? Boarding a plane takes a bit of time.

Especially if passengers enter the plane in a random order as those stopping to store their baggage might block the lane for others.

Why  airlines don't sort passengers, for example during the dead time in between checking boarding pass and actual boarding?

Many airlines do, to a degree.
That's why airliners are often boarded in sections (for example row 1-10, then 11-15, etc.).
Problem is many of the passengers don't listen to instructions, and rush the boarding agent the moment the lights go on indicating boarding has started, in part because they're afraid there won't be space for their 4 bags in the cabin, each of them oversized, if they're not the first on board.

And THAT's the real problem, many airlines not being rigorous about enforcing cabin luggage allowances and pushing people with excess to the back of the line and having them gate check (at additional fees) those bags consistently.


How can dynamic and static pressure be explained? How exactly do you explain dynamic pressure? If someone asked me what the ASI reads, I would say it reads the dynamic pressure, which is the

ram air pressure (total pressure) - static pressure = dynamic pressure

But would explaining dynamic pressure as "the pressure the pitot tube experiences through the air?

As for static pressure, how would you explain that? Would you say static pressure is the pressure the aircraft feels whether it is in motion or not?

You are very close. Your explanation of static pressure is correct, but not your dynamic pressure. Ram air pressure is what the pitot tube measures, in other words the total pressure experienced. It is your airspeed gauge which measures dynamic pressure by mechanically (in the case of a traditional pitot-static system) subtracting static pressure from ram air pressure.

If I was explaining this to a layman I would say that ram air pressure is equivalent to sticking your hand out the window of a moving car, while static pressure is the pressure inside the car. That's a bit of an over-simplification as the pressure inside the car will be lower than outside due to the movement through the air, but it gets the point across.


When do pilots facing bad weather turn back (U-turn)? Passenger aircraft are not supposed to cross red areas on the weather radar. But what if the weather system is too large to circumnavigate and red areas inside the system are too large/prevalent to avoid ?

What are pilots supposed to do if the required detour around red areas would be impractically long ?

divert to an alternate airport in front of the storm (on the near side) ?
go back to the departure airport ?

Most importantly:
When/where (at what stage of the flight: e.g. PNR minus x minutes, or at a specific distance to the weather front ahead, etc.) is the decision made whether to fly through the bad weather or to abandon the destination airport ? And which criteria is this decision based on ?

I assume this decision takes place between the conflicting priorities of assuring the passengers' safety and the (real-world) pressure exerted by (some) airlines on their pilots to reach their destination airport for financial reasons ?

Please distinguish in your answer flight over land and sea, assuming different considerations apply. For example, the pilot may need to take the decision before reaching the critical point or point of no return. What are the implications of ETOPS for this question ?

The premise ("a weather system too large to circumnavigate and red areas inside the system are too large/prevalent to avoid") may be a particularly common situation when crossing the ITCZ:

   a broad band of high total precipitable water along
  the Intertropical Convergence Zone (ITCZ) (source)

Let me take AF447 as an example – not to say that red areas were unavoidable in this case, but just to illustrate how this flight through the ITCZ had to cross a weather system too large to circumnavigate entirely. Unless turning back, the pilots had to pick and choose "holes":

There is no definitive, objective, commonly agreed upon set of criteria that I am aware of that provides an answer to your question.

Certainly airline dispatch departments strive to send aircraft along routes that will minimize exposure to extreme conditions if that's an option, and there may even be changes of schedules involved, but in the end, it's the aircraft captain who has to make the decision in the cockpit, in flight.

As such, and as illustrated by the answers to your previous question, individual captains will employ different criteria. In my experience in the ITCZ and given my outlook, you did your best to pick your way through avoiding the "red" if reasonably possible, and if not possible, you minimized your time in the red.

Doing a U-turn was not an option that we typically considered. This was the attitude and practice of all of my peer group save one. As I remember, he turned back once, and he subsequently left the company. By his own admission, he wasn't cut out for the type of flying we were doing.

Having to cross any of the red during en route flying was not something you had to often do. You could almost always avoid that.

And remember, what the red means is heavy precipitation, which, while potentially accompanied by severe turbulence, does not always mean that will be the case. Thunderstorms with heavy precip would sit over Victoria Harbor in Hong Kong along the IGS approach to the old Kai Tak airport, and we would shoot the approach through the red. There would be turbulence, but nothing abnormal.

Conversely, the absence of red does not ensure there will be no severe turbulence. The worst ride I ever had was going through a "clear" area the radar showed between two cells.

Concerning making a U-turn, and especially flying in the ITCZ westbound during the day, if you did a U-turn you might well find that your return route of flight has closed in and might well be worse than the forward route to your destination. If the heat of the day is building in front of you westbound, the sun's insolation has been building more behind you than in front of you.


What is this device on the nose of a Bombardier Global 6000? What is the circled object?

(jetphotos.net)

That is the sensor for the aircraft's Enhanced Vision System (EVS) - a combination of a visible low light and infra red video cameras which are combined together via computer into a composite image for display on either the PFDs or HUD in the cockpit.  It provides better situational awareness in poor visibility and during night operations for the crew.  See demonstration video here, and a video for how it can light up high terrain here (frame below):


Does oxygen become less available during night-time? The following excerpt is from the FAA's Pilot's Handbook of Aeronautical Knowledge (page 7-37):

  Some people flying above 10,000 feet during the day may experience
  disorientation due to the lack of adequate oxygen. At night,
  especially when fatigued, these effects may occur as low as 5,000
  feet. Therefore, for optimum protection, pilots are encouraged to use
  supplemental oxygen above 10,000 feet cabin altitude during the day
  and above 5,000 feet at night.

The book, in vague terms, suggests that the amount of oxygen (i.e. oxygen molecules) available at a certain altitude at night is less than in daytime.

The regulations do not differentiate between day and night in regards to supplemental oxygen.

What would be the scientific reasoning behind this?

Night vision is one of the first things affected by reduced oxygen levels, and that effect is masked in daylight, but can become consequential at night.  But no, the O2 molecules are the same night or day.

BTW, airline pilots in our 8000' cabins do not have different guidance for putting on the masks -- it's 10k, day & night both. Air Force was, IIRC, the same 10k, with no difference in the rules day vs night.


What is the status of "Notes" in ICAO Annexes? As per the forward to ICAO Annex 11, the status of a "NOTE" in any annex is - "Notes included in the text, where appropriate, to give factual information or references bearing on the Standards or Recommended Practices in question, but not constituting part of the Standards or Recommended Practices."
So, does it mean, a note given in the Annex does not hold any authority as it is not a part of the SARPs ?

Yes. But there should not be a contradiction to the standard. Additional material usually serves to guide the user of the standard.


What is ETOPS and how does it work? According to this press release by Boeing earlier this year, the 747-8 has received its ETOPS 330 rating. This is required by all 4-engined planes made after February 2015 to fly beyond 180 minutes from an en-route alternate airport.

Does this apply only when one engine has already failed? I understand four-engine jets usually continue to their destination on three engines. And how does this compare to the 747-400. Can it fly ETOPS 330+ routes? I remember them doing missions that twin-engine aircraft couldn't because of their lack of ETOPS.

A follow-up question for those who are interested: Why does ETOPS not apply to older 4 engine aircraft?

ETOPS stands for Extended-range Twin-engine Operational Performance Standards, a rule which permits twin engine aircrafts to fly routes which, at some point, is more than 60 minutes flying time away from the nearest airport suitable for emergency landing. ETOPS may also be interpreted as Engines Turn or Passengers Swim.
It is not a rule which applies after an engine has failed. Rather, it is a set of regulations and standards which must be met if an airliner wishes to fly its planes more than 60 minutes away from a suitable emergency airport.
History
Early combustion engines were noticeably unreliable. It was not uncommon for a 4-engine piston aircraft to arrive at its destination with only 3 engines running. Twin engine aircrafts, as a result, were required to fly dogleg paths to stay close enough to an adequate airport.
Aircrafts with more than 2 engines were not restricted by this rule. Thus, many transatlantic flights were flown with Boeing 747s and L-1011s, since airliners can fly a more direct route with these aircrafts.
As engineers gained more experience in jets, they slowly recognized that jet engines are much more reliable than their piston counterparts. The FAA began to approve flying twin engines 120 minutes away from a suitable airport. This made twin engine aircrafts popular, because the fuel efficiency of flying a twin is much better than flying a 4-engine 747 or A340.
Certification
ETOPS certification requires both the aircraft and the airline to comply with a set of standards.
For the aircraft, the manufacturer must demonstrate that flying with only one engine is relatively easy for the flight crew, safe for the airframe, and an extremely remote event.
The airline must demonstrate that its flight crew training and maintenance procedures are up to a higher standard. Pilots, engineers and staff must be specially qualified for ETOPS.
Recently, more operators are adopting the ETOPS approach to non-ETOPs routes. They discovered that the approach offers significant improvements in reliability, performance and dispatch rates. The cost of application is later offset by reduced maintenance costs, and costs associated with diversions, delays and turn backs.
Flight Plan
An ETOPS flight plan may look something like this:

Let's say the aircraft's ground speed (with one engine inoperative!) is 450 knots. By drawing circles with radius 450nm around alternate airports, we can obtain areas which the flight must stay within. The flight path always stays inside one of these circles. If we are operating under ETOPS 120, we will draw the circles at 900nm.
Actual flight plans are slightly more complex, since winds aloft (sometimes more than 100 knots) will affect the aircraft's ground speed. Dispatchers use software to calculate a route, taking aircraft weight, fuel consumption and winds into consideration.


Statistically, how safe are para-motor craft compared to other GA planes? I know there are very well kept records for death and accident rates in GA aircraft, but I was wondering if there were numbers for para-motor aircaft that are easy to compare?

In the US, there are no records kept nationally, because they fly under FAR Part 103, and are, for the most part, unregulated. Neither para-motors themselves, nor their pilots are required to be certified. Para-motors are not required to be registered. In fact, there is no actual government regulation requiring training of any kind to fly a para-motor. It is recommended, but not actually required.

There is no requirement to report accidents to any governing body, beyond those of the organization (flying club) the pilot may belong to.

Pilot certification -

  At this time, however, pilots of ultralight vehicles are not required by Federal regulation to be certificated.

Aircraft Certification -

  However, the FAA presently has no intent to require certification of these vehicles by Federal regulation.

Aircraft Registration -

  However, registration of ultralight vehicles will not be required by Federal regulation at this time.


What type of flow is preferable for jet engines? I would like to know how laminar/turbulent flow affects engine performance. Any additional thoughts on the topic, even if not strictly related to the main question, are welcomed.

The noise within the engine will make all flow turbulent. There is not much liberty for the engine designer to choose the type of boundary layer.

Generally, a laminar boundary layer is preferable as long as the flow is accelerated, because viscous drag will be lower, and a turbulent one is better when it is decelerated, so separation can be delayed.

Outside of boundary layer phenomena, turbulence is helpful for keeping the combustion process going in the combustor and especially in the afterburner. Ahead of the combustor all engines have a diffusor to slow down the compressed air, so it has time to mix with the fuel and burn as much of it as possible. Note that the diffusor only slows down the axial movement of the air, so radial velocities will not be affected and be relatively larger relative to the axial flow at the entry of the combustion chamber. This makes the flow more turbulent, which is helpful for better fuel-air mixing.

In the afterburner, flame holders are needed to produce pockets of slow-moving, hot gas which can ignite the fuel-air mixture. Again, they cause more turbulence.

Flame holder (10) with annular selectors (9) of an afterburner (picture source)

At the nozzle, turbulent mixing of the hot core flow and the bypass flow reduces noise. Engine nozzles use a variety of means to speed up the mixing process.


Where can I find the exact definition of VFR and IFR? Although I have worked as ATC more than 5 years(not US), I don't know the exact definition of VFR and IFR.

Of coure, I know that under VFR, pilot mainly use their eyes to navigate, but I want to know more exact and offical reference.

I tried to search these via google but failed to find offical reference such as ICAO annex or FAA regulations.

Could you guys help me to find the offical reference relating to VFR and IFR?

The Rules of the Air are defined by ICAO and made applicable with few deviations in the ICAO member states.
ICAO Annex 2 Rules of the Air, defines in addition to the general rules, the Visual Flight Rules (VFR) and the Instrument Flight Rules (IFR). Flights shall be in compliance with either of them.

2.2 Compliance with the rules of the air
The operation of an aircraft either in flight or on the movement area of an aerodrome shall be in
compliance with the general rules and, in addition, when in flight,
either with:
a) the visual flight rules; or
b) the instrument flight
rules.

Chapter 5 of Annex 2 contains the Instrument Flight rules.
Chapter 4 of Annex 2 contains the Visual Flight Rules.

4.1 Except when operating as a special VFR flight, VFR flights shall be conducted so that the aircraft is flown in conditions of visibility and distance from clouds equal to or greater than those specified in Table 3-1.

Table 3-1 is summarized below.
+---------------------------+-------------------+---------------------+-----------------------------+
|      Altitude band        |   Airspace class  |  Flight visibility  |     Distance from cloud     |
+---------------------------+-------------------+---------------------+-----------------------------+
| At and above 3 050 m      | A*** B C D E F G  |        8 km         | 1 500 m horizontally        |
| (10 000 ft) AMSL          |                   |                     | 300 m (1 000 ft) vertically |
+---------------------------+-------------------+---------------------+-----------------------------+
| Below 3 050 m (10 000 ft) | A*** B C D E F G  |        5 km         | 1 500 m horizontally        |
| AMSL and above 900 m      |                   |                     | 300 m (1 000 ft) vertically |
| (3 000 ft) AMSL, or above |                   |                     |                             |
| 300 m (1 000 ft) above    |                   |                     |                             |
| terrain, whichever is the |                   |                     |                             |
| higher                    |                   |                     |                             |
+---------------------------+-------------------+---------------------+-----------------------------+
| At and below 900 m        |   A*** B C D E    |        5 km         | 1 500 m horizontally        |
| (3 000 ft) AMSL, or 300 m |                   |                     | 300 m (1 000 ft) vertically |
| (1 000 ft) above terrain, +-------------------+---------------------+-----------------------------+
| whichever is the higher   |        F G        |        5 km**       | Clear of cloud and with the |
|                           |                   |                     | surface in sight            |
+---------------------------+-------------------+---------------------+-----------------------------+
* When the height of the transition altitude is lower than 3 050 m (10 000 ft) AMSL, FL 100 should be
  used in lieu of 10 000 ft.
** When so prescribed by the appropriate ATS authority:
    a) flight visibilities reduced to not less than 1 500 m may be permitted for flights operating:
        1) at speeds that, in the prevailing visibility, will give adequate opportunity to observe
           other traffic or any obstacles in time to avoid collision; or
        2) in circumstances in which the probability of encounters with other traffic would normally
           be low, e.g. in areas of low volume traffic and for aerial work at low levels.
    b) HELICOPTERS may be permitted to operate in less than 1 500 m flight visibility, if manoeuvred
       at a speed that will give adequate opportunity to observe other traffic or any obstacles in
       time to avoid collision.
*** The VMC minima in Class A airspace are included for guidance to pilots and do not imply
    acceptance of VFR flights in Class A airspace

For Air Traffic Management purposes, ICAO Doc 4444 gives more detail of how both types of flights are treated by ATC.

National regulations may deviate from ICAO regulation. If they do deviate, the deviation have to be published in the Aeronautical Information Publication of the country.


What are mechanical requirements for flying over water? What are the mechanical requirements to fly over a large water body? Are multiple engines required? Do the engine/s need to be a certain kind (turbofan, turboprop, piston)?

Private operations - no requirements. Single-engine is legal, you can argue as to the safety.

Commercial operations...
Single-engine: within gliding distance of the land.
Twin-engines: always within 60 minutes of the land... unless specially approved airplane and operator, and airplane maintained according to much higher specs - this is ETOPS.
More-than-two engines: no problem.


What is a good flight simulator for a beginner? I'm in the UK and I wish to learn to fly starting with a home computer simulator.
I have never flown and I am only interested in light aircraft. I need instruction from scratch: what the instruments are for, starting the aircraft, everything from the very start.

I need someone to recommend to me a good home computer simulator which comes with basic flight instruction.

Most commercially available flight simulators (MS FSX, X-Plane, Prepar3d) can make excellent training tools for a budding pilot.  But do take this caution to heart.

The cup has to be empty before it can be filled.

Applied to flight training, do not attempt to instruct yourself how to fly.  At best, you will develop a lot of bad habits which a CFI will have to root out and correct prior to being able to teach you correct airmanship techniques.

On the other hand these kinds of games, when set to use realistic flight models, can be excellent tools for practicing skills you learned when you flew with a CFI in the real thing.  Using a realistic simulator game in parallel with real world flight training can save you a lot of time and money in your training.  These sim games are also excellent for instrument training as much of the required instrument skillset is easily modeled by the computer.  While not approved as an official Flight Training Device for logging official flight time, these sims are extremely realistic - so much so that the same mistakes I make in FSX I will make in the real thing!

One cautionary note:  sims like FSX do model a number of details correctly whereas other ones like dangerous weather, flying at the extreme edges of the envelope, etc are not.  There are a number of scenarios (eg flying into thunderstorms) you can do in FSX which will get you killed in the real world.  Approach learning to fly in a game with caution and any instruction you receive from a CFI should supplant game derived knowledge.


What is the offset in a seaplane's hull? I noticed there is a little offset in a seaplane's hull (highlighted in the following picture). I suppose this is useful as it exists in all the seaplanes I know.

It appears to be neither a hydrodynamic nor aerodynamic feature. I could not find clue by myself as I don't know this feature's name.

My question, what is its name and purpose?

(wikimedia.org)

That's called the step. Without it, you'd have to fight against the buoyancy of the rear end of the hull when you rotate for takeoff.

However, a seaplane float or hull must be designed to permit the seaplane to be rotated or pitched up to increase the wing's angle of attack and gain the most lift for takeoffs and landings. Thus, the underside of the float or hull has a sudden break in its longitudinal lines at the approximate point around which the seaplane rotates into the lift off attitude. This break, called a "step," also provides a means of interrupting the capillary or adhesive properties of the water.
The water can then flow freely behind the step, resulting in minimum surface friction so the seaplane can lift out of the water. The steps are located slightly behind the airplane's centre of gravity, approximately at the point where the main wheels of a landplane are located. If the steps were located to[o] far aft or forward of this point, it would be difficult, if not impossible, to rotate the airplane into a pitch-up attitude prior to planing (rising partly out of the water while moving at high speed) or lift off. Although steps are necessary, the sharp break along the float's or hull's underside causes structural stress concentration, and in flight produces considerable drag because of the eddying turbulence it creates in the airflow.


Are overhead bins airtight? This question is prompted by a recent news about a dog dying while transported in the cabin overhead bin for about 3.5 hours.

Are those bins airtight enough to cause death of a (relatively) small animal by asphyxiation? According to some pics on the internet, the dog in question was a French bulldog or similar.

Screw the cap back on a plastic water bottle while in cruise, by the time you land the bottle will be crushed due to the change of cabin pressure.

If overhead bins were airtight, they would have been forced open or ripped during a climb. Best case scenario they will fail (e.g. crack) slowly after repeated cycles.

Answer is no, they are not.

Related: At which point does an airliner start to pressurize/depressurize the cabin? A typical cabin altitude is between 6,000 and 8,000 feet during cruise for a jetliner.

While this is best suited for Health.SE, the smaller the mammal the faster the breathing / heart rate. And if panicked, it is even more. In a confined space the CO2 from breathing won't be replaced quickly, which can eventually lead to asphyxiation.

See this from Biology.SE: Sitting in a closed room filled with regular air - for how long will the air last?

From BBC:

  Although, overhead lockers are not air-tight, lack of oxygen could have been the cause of the dog's death, US media report.


Could Malaysia Airlines Flight 370 have sunk without leaving any floating wreckage? With all the searching on the surface of the Indian Ocean for evidence of Flt. 370, I'm wondering if there's any conceivable scenario in which the Boeing 777 could have sunk without producing any floating wreckage.

Is it possible for a 777 or similar model to hit water without leaving a trace of remains on the surface?

Yes, but only under highly unlikely circumstances.  An airplane contains all sorts of materials that float, from fuel to seat cushions to the plastic cups in the galley.  In order to sink without leaving any floating wreckage, all of that material would need to be trapped within the airplane while it fills with water.

In order for this to happen, the airplane needs to land intact on the water.  As any number of ditchings indicate, this isn't going to happen -- even US Airways 1549 had the rear of the fuselage tear open on landing.  More often, the engines or wings will tear off, leaving oil and fuel slicks.