Do GA gasoline engines have a tendency to cough, and splutter? I'm wondering if GA piston engines have a tendency to stall like some old carburetor car engines if the throttle is increased too quickly.

What would happen or what could be done if this scenario occurs?

When it happened in cars sometimes you could not restart until the residual fuel was burnt by cranking the engine for some time. Does this apply also to aviation engines?

The question arises from the fact that the design of the engines are quite old from my understanding.

The short answer to your question is: Yes

However...

Its generally advised to avoid making abrupt power changes to aircraft engines (piston and jet for that matter) to avoid surge and potential starvation issues. You are usually taught to apply and reduce power smoothly when learning to fly. Aircraft piston engines are not really all that different than older air cooled car engines (think VW and early Porsche (there was an aircraft certified Porsche motor actually)). As such they can (and sometimes do) suffer from the same pitfalls.

The difference you may see in aircraft engines is that they tend to be a bit better set up and less tinkered with than car engines.

Like any gas engine aircraft engines have been known to, on occasion suffer from vapor lock and fuel pump failure as well. The most dangerous and potentially serious issues in aircraft carburetors is ice build up due to high moisture and low temperatures at higher altitudes. Airplanes have carb heating systems that are manually controlled from the cockpit to solve this problem.

  What would happen or what could be done if this scenario occurs?

Generally speaking this is a rare occurrence and often happens on the ground. Keep in mind that plane throttles are (during a routine flight) adjusted far less than a car throttle. In a car you may be going through a street with lots of stop lights causing you to go from idle to cruise/launch power frequently. In an airplane this really only happens once on take off and to an extend when reaching cruise. When you taxi out and line up you will advance the throttle to full/takeoff power to get in the air. You may then keep it there for your climb or elect for a slightly reduced climb power depending on the situation. You will climb to your cruising altitude and throttle back to between 55% - 75% power for cruise. Fly your flight and at some point you will get where you need to be and throttle back to your decent/landing power.

In the case of entering the runway and lining up if you starve the engine when you apply power you are assumed to be either not moving or barely rolling and should be safe. If you pull the power to quickly on decent and stall the engine you may be gliding distance from an airfield and or have time for a restart.

  When it happened in cars sometimes you could not restart until the
  residual fuel was burnt by cranking the engine for some time. Does
  this apply also to aviation engines?

One neat thing that planes have which most cars done is mixture control. As a result you can pull the mixture control all the way out on a plane (how the plane is shut down), crank the engine, and draw the fuel out of the carb. Some cars will keep pumping fuel and filling up the carb while you crank (since you cant over ride the fuel pump). Generally a flooded car engine you have to wait for it all to evaporate out.

  The question arises from the fact that the design of the engines are
  quite old from my understanding.

Age has little to do with these issues. Fundamentally the internal combustion has changed little since its inception in terms of the way it physically works. While they have gotten far more efficient and reliable the physics are more or less what they have always been. Its our manufacturing technology that has made the engines better. Surging/starving an old engine and surging/starving a new engine will produce a similar issue. Aircrafts use older engines due to the complexity and cost of certifying anything for use in an aircraft. For what its worth Ford has been using the same basic V-8 for as long as some aircraft engines have been around likewise Porsche squeezed a remarkable 30 years out of the same basic air-cooled engine design in the 911 (911 up through 993 variant).

Side Note: As mentioned its expensive to get a new engine put into service. That being said there are common airplane engines out there (like the IO-550) that have fuel injection. As computers become more common place in aviation FADEC systems are becoming more common in airplanes. In the end of the day however, some of these choices come down to manufacture decisions. Some makers prefer to leave things in the hands of the pilots, in other words you can pull and advance the throttle how ever you like and the fuel/air delivery system will behave as such. Other makers have begun to put safe guards in place to prevent this, and they will (no matter how you operate the throttle) ensure proper advance and retard of all mechanisms as fast as possible should you operate the throttle vigorously.


Do pilots lose their licenses following a gross misdemeanor conviction? Can you have a conviction for a gross misdemeanor and still keep your private pilot's license?

The most important thing to say here is that the only way to get an answer for a specific case is to consult an aviation attorney. Don't rely on any answers you get here!

Having said that, the general answer (that may not apply in every case) is that the FAA is primarily interested in alcohol and drug actions and convictions, including driving offenses and drug transportation. Pilots have to report those per 14 CFR 61.15, and again in any future application for a medical certificate:

  Do I have to report anything other than alcohol and/or drug related
  convictions?

  Yes, under 14 CFR Part 61, you must report alcohol and/or
  drug related administrative actions, whether a conviction took place
  or not. Arrests, administrative actions and convictions are also
  reportable under Part 67, the airman application for a medical
  certificate.

AOPA has a good explanation of the reporting requirements and their Pilot Protection Service can help with medical and legal issues. But it isn't a foregone conclusion that you lose your certificate, at least in 'simple' DWI cases:

  A single driving while intoxicated (DWI) arrest, conviction and/or
  administrative action usually is not cause for denial provided there
  are no other instances or indications of substance dependence or
  abuse.

Leaving aside alcohol and drugs, if the misdemeanor had nothing to do with aviation then it's unlikely to come within the FAA's scope. There might still be some odd theoretical possibilities, like if the misdemeanor conviction attracts the TSA's attention and you're flagged as a security risk (see 14 CFR 61.18) but that's just playing with 'what if' scenarios. Again, you need to consult an aviation attorney for advice on specific cases.


Confusion about Aerodynamic center suppose, i assume Aerodynamic Center lies at Center of gravity.  Then apparently moment by lift will be zero about CoG. But in reality Centre of Pressure may be behind aerodynamic center and still be producing a moment. So isn’t using aerodynamic center absurd?

It's easy if we clarify your statement a bit.

When aerodynamicists say "moment by lift", this means the derivative of moment by lift. That is, the change of moment per change of lift, $\partial M/\partial L$, or shorthand $M_L$ (or their coefficients more commonly: $C_{M_{C_L}}$). Stability analysis (that's where the aerodynamic center is most useful) is all about derivatives rather than actual forces and moments: we are interested what changes when conditions change.

In this light, "moment by lift" will be zero, true, but "just moment" won't be.


Best Practices when removing/inspecting/mounting control surfaces? I am looking for a better way to essentially "mount" the control surfaces from a Boeing 737-747-777-787 and MD-11's. The current process is to just remove them and strap to a table. The issues with this is that it takes a lot of time to remove/inspect and possibly repair. the other issue as the way we are "mounting" them for said inspection. By strapping them to a table they can be bent, dropped, and it just isn't the best idea to have the control surfaces, like an 18 ft aileron, laying on a table...

I am just looking for any advice when it comes to mounting and servicing these parts as well as alternatives to strapping them to a table...

Your airline should have proper holding fixtures, basically a wheeled frame that mounts the surface at key attachment points, for control surfaces, either purchased from the manufacturer or designed in house.  The table strapping business is probably because the airline is too cheap to get the proper equipment.


What happens if a passenger dies mid-flight? Last month (December 2014), there were news that a passenger passed away during a flight. As mentioned in this answer, it appears that it is not a very uncommon scenario.

In an unfortunate incident like this, how is this matter handled?

In the event of a passenger dying on an airplane during flight, each case is different depending on the location of the airplane, the duration of that flight and the wishes of family or friends traveling with the deceased passenger.

What happens to the flight?
If the death occurs before takeoff or shortly after takeoff, the airplane is landed back to that airport or the nearest airport. If it happens mid-flight, normally the flight is continued to its destination.
Where is the deceased passenger placed?
If there is a seat available in first or business classes, the deceased person is moved there and covered with a blanket. If it is a full flight, that person may simply be strapped in more tightly and covered. This is done to ensure that the body is out of view of other passengers. A deceased person is never placed in the lavatory. It is not respectful and a major security concern.
What happens at arrival airport?
The arrival airport is informed in advance about the situation. Hence police, ambulance and coroner are available. Some airlines keep body bags on board. Normally the deceased person is placed on a stretcher and is carried from the rear exit of the airplane using a lift truck and then placed in an ambulance. This might be done after other passengers have exited the airplane.
What are the regulations?
FAA have regulations addressing several emergencies, but not specifically this one. An FAA spokesperson mentioned:

  FAA spokesman Les Dorr said he was unaware of any policies that
  specifically address what should be done if someone dies in flight.
  The airlines make those decisions on their own.

This article mentions some incidents of this situation happening.

MedAir is a company which provides airlines with medical help from emergency care doctors on the ground. They estimate that:

  ... there is one death for every 8 million passengers from the airlines [they] serve ...


What is this tube in a jet engine's air intake? I have long been wondering what is the official name of this little air intake tube located in front of the fan blades and its intended functions. I did search it on google but it was in vain. I guess that it may be a pitot tube installed inside a jet engine for gauging the airspeed of the engine intake air.

That's the EPR inlet pressure sensor (there's another one located aft of the engine in the exhaust).

EPR = Engine Pressure Ratio, one way to measure thrust.

(source)

See also:

What is the difference between EPR and rotor speed as thrust setting parameter?
How does the EPR reading behave in reverse, and in reheat modes?


Is data approval by DER/DAR still required under new FAR part 23? New FAR Part 23 rules have been enacted on August 30th 2017, simplifying certification for small airplanes.

Will the FAA still require:

Designated Engineering Representative (DER) approval for each drawing, and
Designated Airworthiness Representative (DAR) conformity of each part?

This is not required for Light-Sport Aircraft (LSA).

It's not entirely clear how the process will work. The FAA hasn't updated AC 23-17C in response to the rule changes. I also haven't seen any discussion of changes to Production Certificates.

That said, Part 23 is still "AIRWORTHINESS STANDARDS: NORMAL CATEGORY AIRPLANES"
and there hasn't been any change to Part 21, so it appears that there still will be Type Certificates, and per 21.20 you stll need to show compliance to the relevant standards, which for normal Category is Part 23.

The big change to Part 23 is that it is more performance based instead of design based (what it must do, instead of how to do it).  So the actual means of showing compliance will need to change. I don't see DERs and DARs going away with respect to Part 23. I do expect that what they review and how they do it will likely change.

To your point, LSA receive a Special Airworthiness Certificate (based on ASTM Concensus Standards), as opposed to a Type Certificate defined in Part 21.21.


What does the ASDE-X ground radar unit look like? Above is a picture of a primary / secondary surveillance radar combo (top is secondary, bottom is primary).

What does the ASDE-X radar unit look like in real life?

This page claims to show the Raetheon ASDE antenna at Boston Logan. However, Saab Sensis appears to be the prime contractor for the ASDE-X system. Boston does have an ASDE-X system, according to the FAA.

According to the above link, Saab provides the "Multi-Sensor Data Processor" that "fuses the surface movement radar, multilateration, ADS-B and terminal radar data into a single track that is correlated with flight plan information." So my guess is that Raetheon provides the radar antenna and Saab does the software integration, alerting, fusing, etc. Since the contract is in the US there may have been a requirement to use a US radar supplier.

As an interesting aside, Saab recently announced a third generation Surface Movement Detection antenna, the SR-3:


When are multiple hops more efficient than single leg? Considering a very long route (equal to the max ferry range of an aircraft[1]).

Would it be more fuel efficient to fly multiple legs or a single one ?

Multiple legs would allow you to use less fuel, decreasing weight and fuel consumption
Single leg would dispense you having to go through multiples takeoffs and time increased at low, high drag altitude

How does theses balance ?

I'm interested into any real world aircraft[!].

[1]: Results might differ for each models so you can pick any you like.

In a broad sense, if the flight distance is nearly equal to the max range of the aircraft, the route with shorter legs is prefereable from the point of fuel economy. The reason is simple- more the fuel you carry more the aircraft you have more weight, which requires more fuel.

All other things being equal, the fuel caried is payload- one can see it as the aircraft carrying extra payload or as the fuel eating into the regular payload. Either way, the extra fuel carried impacts on the fuel effeciency of the aircraft negatively.

According to this document, payload burns fuel at the rate of 2.5-5 % of its weight in fuel per flight hour. For the longest non-stop routes in service, the travel time is in the upwards of 15 hours. Taking a value of 3% fuel burn, this means that a significant portion of fuel consumption is actually to carry the fuel itself. This is a significant issue, especially when the oil prices are high.
The increased take off weight will result in more thrust requirement, TO length and time to climb (or more thrust again), adversely affecting the fuel consumption, while increasing engine wear.
While it is true that the longer distance flights spend more time in altitudes with less drag, it is questionable whether that translates into any significant real world benifits. For example, the latest 777 ULR version has a higher aspect ratio to reduce drag, requiring the folding of wings.
Of course, fuel use is only a part of the story. The other significant factor is time- most of the ultra long range flights are targeted towards business flyers, for whom the addition of more than 25% due to shorter legs may be unacceptable. In the end, the deciding factor may be the percentage of seats filled per flight. When SA cancelled the Singapore-Newark flight, one analyst noted:

  “The plane burns a lot of fuel but carries very few passengers,” says Siyi Lim, an analyst at OCBC Investment Research in Singapore. “It didn’t make sense to continue.”

The ultra long distance flights also require additional facilities- extra crew for rotaion, extra food items carried etc. In general, the straight long distance routes have higher fares compared to the ones with stops in between.


Do (did) powered airplanes exist where pilots are not in a seated position? Well... all is said in the title. I mean "traditional" powered airplane, with a cockpit and long flight capable, not a paraglider.

Upright pilot or prone pilot would qualify.
Likely experimental or military.

Source

The concept was once studied with the XF-90, but didn't get to reality.

In the first ones the pilot was rarely sitting. Inspired by ships, some early aviators steered their craft by standing upright:

Almost all balloons were and still are flown standing upright. Same goes for all Zeppelins, and they should qualify as powered aircraft.
All Lilienthal glider designs required the pilot to stick the forearm through a tube and grab a horizontal bar, so his weight would rest on the forearm. Steering was done by swinging the legs left or right rsp. back or forward. The legs also doubled as the landing gear, much like in modern hang gliders. Lilienthal experimented with carbon dioxide engines, so some of his gliders can be called powered.
Gustave Whitehead's Number 21 design of 1901 was flown standing upright, but it is disputed that he actually flew it successfully.
The early Wright Flyers were flown in a prone position. Sitting came later.
The Santos-Dumont 14bis of 1906 was flown standing upright. Similarly to the Wrights, Santos-Dumont's later designs like the Demoisielle had a proper seat.

Santos-Dumont training to fly his 14bis (picture source)

The Horten gliders were flown in a prone position so the pilot would present a lower cross section. The Horten IIId was a motor glider version using a 32hp Volkswagen engine, so this should count as powered, too.
Before anti-g suits were perfected, some designs used a prone pilot position to increase the possible g loads. Here is an answer which covers this aspect.
René Leduc's ramjet-powered experimental aircraft used an almost lying position for the pilot to keep the cross section of the centerbody small.

Yvan Littolff in the cockpit of the Leduc 021 (picture source)

Most hang gliders use a prone or almost lying position for reducing the drag the pilot causes. The powered ones should also qualify here. Same goes for motor gliders derived from sailplanes, where the pilot position is almost lying, too.


What does leading edge radius mean? What does leading edge radius mean amongst these parameters of a st cyr 24 airfoil?

The radius of the leading edge as a percentage of chord.


How to reduce the noise of the supersonic passage(bang)? as you know the transonic phase is often associate with the bang.
The principal cons of the transonic phase is the noise,it's why there is not supersonic passenger aircraft( cause the end of the concorde).Nasa (x59) and Boom(xb-1) do research to reduce this noise at door slam.
How is it possible? I know that we need a aerodynamic plane respecting the aera rule and have a thin fuselage. Have you" wind tunnel" images?or theorical explications?

Edit: for those who want i found more information about the bang on this vidéo. (2:35 to 4:45)

Most supersonic aircraft have points where the cross-section suddenly changes, such as the fuselage nose, the wing root leading edge or the wing trailing edge. The points of sudden change produce sharp changes in air pressure, i.e. loud sonic booms. Concorde was one example.

By designing the plane's cross-section to vary smoothly from end to end, the handful of points of major change are replaced by many more points of minor change. The booms are thus reduced in loudness and spread out in time, making them less intrusive.

Other factors which help include overall aerodynamic efficiency, light weight and high cruise altitude. A small, carefully-profiled and aerodynamically modern high-flying aircraft can thus be a lot quieter.


What is "spatted undercarriage"? The Socata TB-family wikipage lists the TB-9 and TB-10 as having "spatted undercarriage". What does that mean? From the pictures it appears to be a normal tricycle-gear-setup so I assume it's not referring to the layout of the landing gear.

If I'm not mistaken, a spat is a fairing for the gear to make it more aerodynamic.

  An aircraft wheel fairing, commonly called a wheel pant or spat or, by
  some manufacturers, a speed fairing. Wikipedia


Is there a model to calculate fuel burn over the Atlantic ocean given an arbitrary aircraft identification? Is there any accurate model that can take flight data, plane identifications and compute the amount of fuel that the aircraft would burn flying a set route over the Atlantic ocean.

I am sure every airline has such a model, which will include actual wind and temperature information, but it will contain proprietary data which is not publicly available, unless you have a proven interest and signed an NDA with the airframe and the engine companies. Boeing is actively marketing such software to it's customers. For first-order estimates, Federico's comment is a good start, but you will still need fuel flow and L/D values.

A range of similar software exists, but here the quality of the output depends mainly on the quality of the aircraft and engine models. While Boeing should know their aircraft well, the authors of independent software like Piano or APP have to guess the right values, but still sometimes such tools will be precise within one percent. Piano even offers a free version called Piano X, but you will need to burden yourself with a Windows installation to run it.

If you need even more precision, there are commercial packages which do this, first of all J2 Aircraft Dynamics. But this does much more; fuel flow is only a tiny aspect of the full package. Eurocontrol is supporting BADA, which is a tool for computing aircraft trajectories, but it can also compute the full flight and contains an extensive set of detailed aircraft datasets. Access to BADA is restricted, however, and you will need to acquire a license.

If you want to assemble your own tool, JBSim would be a good start. Write a wrapper which calls JBSim repeatedly and keeps track of the aircraft trajectory, and integrates the flight parameters along the way. But you will still need to get the aerodynamics and engine data from somewhere.


Can Approach cancel my special VFR clearance if I'm already cleared? Say I have requested a special VFR to enter Class D airspace. Approach acknowledges and clears me into the Class D airspace. After entering the Class D airspace the airport visibility drops < 1 mile.

Am I required to exit the airspace or can I continue as normal?

The clearance comes with the catch that you need to maintain the minimum visibility requirements and sky conditions, if you're not able to, you have no clearance, it's pretty much as simple as that. Either you need to navigate in such a way that you avoid the weather (which might require you to leave the airspace) or you can do one of two things

Request an IFR clearance if you're rated and equipped
Declare an emergency and land in the nearest suitable spot, assuming you can still see the ground

If it is deteriorating so quickly that you cannot go back to where you came from (i.e. the weather is not better outside the D), you'd be flying illegally outside the D as well, so no point in going there really, but more importantly, if the weather is deteriorating that dramatically, you don't have much time before you'll be completely blind, and by that time you'll want to be on the ground with as little injuries as possible, no matter where or the condition of the aircraft.

Note that the minimums are different depending on where you are (jurisdiction) and type of aircraft.


Can one pilot lock the other out of the cockpit? One seemingly plausible theory about the MH370 disappearance is that one or other of the pilots locked the other one out of the cockpit and then depressurised the cabin.

However, this answer mentions a code that can be entered to unlock the cockpit door. Could this apply in this case (on a 777)?

Yes, see the Ethiopian Airlines hijacking in February 2014.

From this BBC article about MH370:

  The security of the cockpit door offers protection against intruders, but it also prevents action being taken if something does go wrong. Last month the co-pilot of an Ethiopian Airlines flight waited for the pilot to go to the toilet before hijacking the aircraft and flying it to Switzerland.

As for higher authority codes, from the same answer you linked to:

  Even if the stronger code is entered that will open the door the pilots still have some time to cancel the unlock request.

Meaning that if a pilot is willfully locking the other out of the cockpit, there is no way for the other to regain access to the cockpit.


What happens if I don't remove the "remove before flight" pad before flight? Having just been to a bunch of air museums, I've seen quite a few of these:

 img credit http://www.thewire.com/global/2013/02/iran-new-stealth-fighter-jet-fake/61781/

Those red pads they put in the jet engines that say "remove before flight" - what happens if I try to start the engine with that pad in there? Would the exhaust just blow it out?

As Ratchet Freak says, it's going to blow away or cause the engine to fail. Latter might happen if it sits tight enough that it doesn't get blown away before overpressure develops in the engine.
Not a good thing, damage may happen.

My guess most likely outcome is that it will be blown back, possibly colliding with parts of the aircraft (and thus causing damage) or hitting the hangar wall or whatever else is behind the aircraft with some speed (unless there's a lot of clear area, in which case it'd flutter to the ground), if it's not overfastened.

And to be complete, it's a cover to prevent things from getting into the engine while the aircraft is parked. Dust, animals, anything.
There will be others on the air intakes as well.


Does Molecular Weight of a Gas affect its lifting properties at the same velocity over the same wing? Let's say we test the coefficient of lift of the same wing at the same AOA and the same flow velocity at the same pressure.

The difference is wind tunnel A will contain helium (molecular weight 4) gas and wind tunnel B will contain air (average molecular weight around 29).

Which test will produce a higher lift coefficient?  Why?

The wing will produce much less lift in helium than in air; all else being equal, lift is proportional to the molar mass of the gas in question.

The lift equation states that lift $L$ is proportional to the air density $\rho$ (rho):

$$L = \frac12 \rho \ v^2 \ S \ C_L,$$

where $v$ is the true airspeed, $S$ is the wing area, and $C_L$ is the coefficient of lift.

Meanwhile, one form of the ideal gas law tells us how the air density $\rho$ is related to the molar mass $M$:

$$\rho = \frac{MP}{RT},$$

where $P$ is the (static) pressure, $R$ is the gas constant, and $T$ is the absolute temperature.

Combining both of these equations, we find that

$$L = \frac{M P \ v^2 \ S \ C_L}{2 R T}.$$

In words, lift is

the molar mass of the gas,
times the static pressure,
times the square of the airspeed,
times the wing area,
times the coefficient of lift,
divided by the absolute temperature,
divided by a constant (the gas constant $R$),
divided by $2$.


Why don't all pilots receive at least basic instrument training? Given the frequency with which non-instrument-rated pilots get themselves killed attempting to continue VFR flights into instrument conditions, why don't all pilots receive at least basic instrument training (at the very least, knowing how to interpret the navball and headingometer) during their initial flight training?

While the number of pilots who die flying VFR into IMC is tragic, it's a miniscule percentage of pilots overall. The vast majority of us take the risk seriously and either stay clear of bad weather or get the additional training to be able to handle it safely. The former have no need for the additional training, and the latter are already getting it.

Every pilot in theory knows how to fly by instruments. The problem is that it is surprisingly difficult to believe them when your body is telling you they're wrong. And once you spend a few hours training yourself out of that problem, you still have to spend dozens more hours learning how to fly in the IFR system, which is an entirely different beast than flying VFR--and to many (perhaps even most) pilots not of interest at all.

Also, flying is a perishable skill. Having flown IFR once years ago doesn't mean you can safely do it today, especially if it happens unexpectedly. Worse, having had training may give people a false sense of confidence in their skills, leading them to knowingly fly into bad weather that they would have avoided if they'd never had that training.

FWIW, using your logic, the FAA does now require a few hours of hood time to get a PPL, but the purpose of that is to demonstrate to students how they are not prepared to handle it, other than to make an emergency 180 and return to safety. It's like how students practice stalls so they know how to recover from (and ideally avoid) them, not to encourage pilots to stall their planes in normal flight. And the stats haven't changed.

In the end, the root problem isn't the lack of instrument training; it's poor judgment. Take away one way for high-risk pilots to kill themselves and they'll just find another, so nothing changes except the cost of training went up for the vast majority of pilots who didn't need saving in the first place.


What are lateral, longitudinal and directional stability? When we talk about aircraft having a stable configuration, it refers to lateral, longitudinal and directional stability. Can someone give a practical explanation of what those are and how they work?

The answer here is found in the Pilot's Handbook of Aeronautical Knowledge (and probably elsewhere) and is as follows:

The longitudinal axis of an aircraft is more or less a straight line through the aircraft's nose cone or prop hub and the endpoint of the fuselage (the aircraft's center of gravity will usually lie along or just slightly above/below this line as well). It is the axis around which the aircraft rolls, controlled by the ailerons. The lateral axis is parallel to the wings and passes through the aircraft's center of gravity. It is the axis around which the aircraft pitches, as controlled by the elevators. Finally, the vertical axis is "normal" (perpendicular in all directions to) the geometric plane formed by the longitudinal and lateral axes, parallel to the aircraft's primary lift vector and (in level flight) its weight vector. It is the axis around which the aircraft yaws, controlled by the rudder.

Rotation about any one axis is the job of one linked set of control surfaces as mentioned above. Stability in that same axis, roughly defined as keeping that line passing through your aircraft pointing in the same direction, is the job of the other two surfaces in concert, but primarily the one that would move the endpoints of that axis up or down relative to the aircraft. So, elevators provide lateral rotation to achieve longitudinal stability, and vice versa for ailerons.

It differs slightly for the vertical axis, as if your plane is both longitudinally and laterally stable, it's also "vertically stable", however the plane is longitudinally and laterally stable, but completely out of control, in a "flat spin". Stability in the vertical axis therefore is secondary to "directional stability", which keeps the longitudinal axis pointing in a particular direction along the geometric plane formed by the lateral and longitudinal axes. In this case the rudder both controls yaw and provides directional stability.

In addition to control surfaces, weight and especially the aircraft's center of gravity is important in stability. Ideally, most small planes are most stable in level flight when the CG of the aircraft is exactly on the centerline of the aircraft (between the tip of the nose and the tip of the tail) and slightly forward of the aircraft's center of lift (which depends on the wing's angle of attack but is usually close to the thickest point in the wing's cross-section). In this configuration, while the aircraft is travelling forward normally, downwash from the wings flow over the top of the horizontal stabilizer, keeping the nose level. In a stall, the slight nose-heavy configuration along with the stabilizers in the rear will cause the nose to point downward gently, restoring normal airflow and allowing the pilot to recover.

If the CG is too far forward, the pilot will need to apply upward pitch or trim to keep the nose level. This will reduce the amount of travel he will have available to pitch up, and in a stall, the plane will nose down sharply and the elevator may provide insufficient force for the pilot to pull out of the dive.

If the CG is too far aft, the plane will want to nose up constantly, and the pilot will have to apply downward elevator or trim. In a stall, a plane with an aft CG won't nose down, preventing the pilot being able to restore normal airflow over the wings. This is especially dangerous in an uncoordinated stall aka a spin; the aft center of gravity in combination with the forward thrust of the engine will "stabilize" the plane in the spin and make it impossible to recover.

If the CG is off the aircraft's centerline, the plane will tend to roll towards its heavier side. This is compensated for with ailerons or aileron trim, and for most everyday flight it's the easiest to compensate for, but it can cause unfamiliar roll behavior and a tendency to spiral down, which the pilot must be aware of and correct for.


Why does the Information Manual say "C172S - Flaps 10 (Preferred) for Normal Takeoff", when the models before S-model do not have this note? Do Flaps 10 really do anything performance-wise other than reducing ground roll and distance over a 50-foot obstacle? If not worried about clearing an obstacle, does a Flaps UP-normal takeoff make more sense (Better climb performance since no drag from Flaps) in the C172S?

The Cessna 172S has more power (180hp vs 160hp for 172R) and higher MTOW
(2550lb vs 2400lb for 172R).
This means that folks used to rotating at 55 knots IAS in earlier models would be closer to stall if taking off "clean".  Another way of doing it would be to add 5 knots and rotate clean at 60 knots.
Vx is also a bit higher in the 172S at 62 knots IAS.
Vy is at 74 knots and Vbg is still at 65 knots, indicating few changes aerodynamicly, just a bit more weight requiring more airspeed to generate adequate lift, or flaps can be added to increase lift coefficient at a lower airspeed.


What exactly is the afterbody of an aircraft? In my understanding the afterbody is everything trailing behind the nose of the craft excluding the wings and fuselage, and will thus include the empanage.

What exaclty is meant by the afterbody?

Each vessel, whether land, sea, or air, should (might) have a defined afterbody. The afterbody is defined as:

  The afterpart of a vehicle; The part of a vessel abaft midships; A companion body that trails a satellite or spacecraft; A section or piece of a launch vehicle, rocket, or spacecraft that enters the atmosphere unprotected behind the nose cone or other body that is protected for entry

and Merriam-Webster Online defines it as:

  :  the after part of a body: such as
  a :  the part of a ship abaft midships
  b :  the bottom portion of a seaplane hull or float aft of the main step

To show you, visually, an easy to see set of examples, consider the following pictures of floatplanes (seaplanes):

In the first and second images, the afterbody is that part of the aircraft behind the step, which is the little 'notch' or, well, 'step' just behind the main wheels. In the third picture, the afterbody is everything after the step, which is the more steeply angled section under the wings. The step is generally just aft of the center of gravity of the plane.

Generally speaking, if one were to discuss the afterbody of a large airliners, such as the Airbus A380, the afterbody would be the fuselage from the wings back, but not including the tail (where the rudder and elevators are.) I could not find any Airbus references to 'afterbody' however. I did find some references to the afterbody of a Boeing 787, being that part of the plane behind the pressurized cabin, which is the very back of the plane, including the tail.

Not a very good solid definition where everyone agrees, sorry.


What is the minimum thrust needed to takeoff? In passenger airplane how much thrust is required to takeoff? What factors does it depend on?

You need at least enough thrust to keep the airplane flying at the speed of minimum drag. This is quite a bit higher than the minimum flight speed, so you should add something to quicken the acceleration to this point. Also, you want to climb eventually, so you better add some more thrust.

Normally, the static thrust of an airliner is at least a quarter of its weight. If the airliner is empty, this can become as much as half of the weight.

One reason is altitude capability: Since thrust goes down with the density of air, the static thrust in the cruise altitude is only a quarter of sea level thrust. The thrust of a modern high-bypass-ratio engine drops with speed, so at cruise speed and altitude, thrust is roughly a sixth of sea level static.

The second reason is safety: The take-off should be continued even after one engine fails in the late acceleration phase. Now a normally two-engined plane has only half as much thrust available and should still get into the air, so it doesn't crash into whatever follows at the end of the runway.

The thrust needed to sustain flight is about 1/18 of aircraft weight, and if you factor in the multiples given above, you will notice that if the aircraft can fly at full thrust in cruise, this fits nicely with a static sea level thrust force equivalent to one third of its weight force.

The factors for take-off thrust are:

Runway length: Short runways need more excess thrust for faster acceleration.
Runway elevation: Higher places have less dense air, so more speed is needed to get airborne, and less thrust is available from the engines than at sea level.
Runway slope. Taking off downhill is equivalent to having a little extra thrust.
Air temperature: Colder air is denser, so minimum speed is lower and the engines develop more thrust.
Wind speed: A headwind is equivalent to starting the takeoff run at this speed.
Minimum flight speed: A low wing loading and low-drag flap settings reduce the speed at which the aircraft can take off.


I have a European EASA license - what do I need to do to be allowed to fly in the US? I own a PPL(A) license following JAR-FCL. Recently, this license has been exchanged for a European EASA license.
My training was on a motor glider (TMG), I do not have ratings for SEP, but TMG and Ultralight only.
In Germany I will have to fly a one hour test on an SEP to get the rating (plus about 5h for training).

What do I have to do in the US to get the rating?

From a private pilot's perspective, there are two possible options: a foreign-based license or a 'full' FAA pilot's license.

The first type is defined in 14 CFR 61.75, which starts like this:

  §61.75   Private pilot certificate issued on the basis of a foreign
  pilot license.

  (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.

You apply to the FAA and they check with Germany (or wherever) that your foreign license is valid. If it is, they'll issue a foreign-based license "with the appropriate ratings" with no flight or theory test of any kind required. That's for VFR only; if you're instrument rated then you also have to do a theory test as well if you want to fly IFR.

That sounds great - and I suppose it is - but there are two big practical concerns. First, any limitations on the foreign license are applied, e.g. if your license is for daytime VFR only then you're still restricted to that, even if a regular FAA license would allow night VFR. And if your foreign license expires or becomes invalid for any reason, the FAA one does too.

Second, you won't have been required to learn anything about US regulations or flying practices. So you might not fly safely or legally because you simply don't know the rules or even what services are available to you as a pilot (FSS, Flight Following, TRSA etc.). One way to handle this is to get some general orientation or introductory training from a US instructor or school, but as a foreigner that will require TSA approval unless you can do it as ground school only (which is not defined as "flight training"). But you might find - as I did - that some instructors will not work with a foreign student at all until they have TSA approval, whether or not it's just ground work.

The other option is to get a normal, full FAA license. You have to pass the same FAA medical, written and flight tests as US pilots to the same standards. You can count your previous flight time towards the required hours but you do need to be able to pass the tests so you will certainly need some instruction. And as a foreigner you will need TSA approval before you can receive any flight training.

The big advantage of getting a full license is that it never expires. If you really want to get one and you have the time and money then you could look into spending a month somewhere suitable in the US (Florida? Arizona?) at a flight school to get it as quickly and cheaply as possible.


Do small or regional airports have maintenance staff or companies onsite? Do small airports or regional airports with just a couple of flights per day, maybe even from different airlines all have on-site aircraft maintenance staff? It hardly seems economical to have certified on call mechanics at most small airport? Are there regulations requiring such?
If there are not any, what happens if a hard landing is performed? From my knowledge an inspection by a mechanic is then required.

For scheduled commercial aircraft you will generally find:
If enough aircraft are coming and going from a particular airport, the airline may keep a line maintenance operation running there that can handle short-term maintenance and troubleshooting, or special inspection operations.
If not, and the airport has a AMO (approved maintenance organization) on site, the airline may contract with the AMO for line maintenance services, troubleshooting or special inspections.
If that's not the case, the airline will simply fly mechanics to the airport when airplanes are AOG.  This is typical when airplanes have problems that prevent dispatch at small remote airports.
So if an airplane needs a hard landing inspection at a remote "outstation", it'll be done by local contract staff if an AMO qualified to do the inspection is there, or barring that, airline staff flown out to the site.


Where can I get a graph of lift coefficient against AOA for a symmetrical airfoil? Where can I get get a graph lift coefficient against AOA for a symmetrical airfoil ? I am asking for a source or link to a graph or table of AOA against Cl of any symmetrical airfoil.

Search symmetrical airfoils in Airfoil Tools DB

Quabeck Sailplane 10 as an example


What is the runway holding short line on Taxiway B between B2 and B3 at KFAT for RWY29L? At Fresno Yosemite International Airport (KFAT), I was instructed to taxi to RWY 29L via B11, B from Signature Support. When passing B3 and approaching RWY 29L end, I noticed there is one holding short line between B2 and B3 and the next one is on B2, I was confused where to hold short for the instruction (hold at the first anyways).

The one between B2 and B3 seems extra, but it is a double-solid-double-dashed line, which is also shown the Google Map the same I observed. I am wondering how this can well-define a runway protection area? Meanwhile, the first holding short line (the one between B2 and B3) does not mark which runway it protects. I also suspect it should have been ILS protection marking instead.

Google Map Link to KFAT Airport

FAA Airport Diagram for KFAT

That’s a hold line for aircraft taxiing on Bravo while large aircraft are departing Rwy 29L to prevent aircraft from taxiing behind the blast pad for 29L and potentially being tossed around by the jet blast from the departing aircraft.


How does EEC/FADEC recognize/anticipate engine acceleration/deceleration? So I'm wondering, when the engine runs at idle and the pilot sets a higher thrust level, what exactly happens, that the EEC/FADEC recognizes, that I want to accelerate? My professor said, it's anticipating the upcoming acceleration through:

$TRA > TRA_{threshold}$
$pt_3 < pt_{3_{min}}$ (cabin bleed)
$N2/\sqrt\theta < N2/\sqrt\theta_{idle}$ with $\theta = Tt2/T_{t ref}$

I get that the TRA (throttle lever angle) is higher than my previous one, hence I just raised it. But why exactly would pt_3 be lower than pt3_min, and why is $N2/\sqrt\theta$ smaller than idle? That would indicate that Tt2 has increased.

You probably need to go ask your professor for clarification.  But let's look at it this way: what would it mean if $Pt3 > Pt3_{min}$ and $N2/\sqrt{\theta}>N2/\sqrt{\theta}_{idle}$. It means that the engine is probably NOT at idle. So in that situation, if you move the throttle, you probably do want to increase thrust, but not from idle.  The EEC may have different control schedules for idle vs above idle operation.


What training is required to become an air traffic controller? I'm curious as to what it takes to be an Air Traffic Controller. I sat in a preliminary online test after I got accepted in, but it was mindbogglingly difficult. One of the questions I had to do was to add two 8-digit numbers in less then 5 seconds. With such difficult questions in mind, there must be on the job training in addition to class room training as well.

Q: What sort of training is done in becoming an ATC, and what sets the difference between a good ATC and an average ATC?

Training for US path is(I'll take this information, post hiring, since they keep changing how they hire, and assign facilities, also length of times are approximate and might vary):

FAA Academy(Oklahoma City, OK):

~6 week AT Basics Course(If you went to a CTI(College Training Initiative) school, this course is skipped)
Then if you're split depending on which area you're going to, Enroute, Tower, or TRACON.
Tower course is ~8 weeks,  TRACON course is 1 month (or 2 if you're going to a bigger facility and they put you in a supplemental course), and Enroute, I'm not positive is around 10 weeks or so.

Then you move to your facility. At your facility, your first days you'll spend learning various materials, and then be given classroom training, including Computer based instruction, an actual instructor time(if the facility is large enough), and also lots of study time to memorize all the maps, and various items you will be tested on. Then, if your facility has the ability, you'll do some simulator problems. Note: you might only get the classroom and simulator for only a subset of positions at the facility, depending on how they break up the training.

Then after all that, you head out to the operation, and will usually start training on some subset of positions that are at the facility. You'll receive training on each position, until you've demonstrated that you're competent to work it on your own. Once/if you get to that point, you're given a certification check by your supervisor, and if you pass you're certified to work that position. And you repeat that process for each position, and possibly having to return to classrooms/simulators for any additional positions, and repeating the process again. Once you've finished all the positions you need you're a fully certified controller at that facility.

Each time you move to a new facility, you will have to repeat the classroom and simulator, and on the job training at the positions at that new facility.

There's far more detail and nuance than I can easily explain here, but this is a general overview of the process.


Is this just a generic B737 or does it have a specific name? Is this just a generic B737 or does it have a specific name?

(planespotters.net)

This is the A6-FZZ Dubai Royal Air Wing Boeing 737-8KN(WL). The other 737-800's they have have different liveries, namely cheatlines.


Can I fly the LNAV MDA when the GPS is set up for LPV? I am going to do my CFII checkride in a few weeks and my DPE wants to do RNAV approaches to satisfy the Non-Precision and Precision approaches tasks on the PTS/ACS.
According with the Instrument ACS an RNAV (GPS) approach with LPV minimums can be used to satisfy the precision approach task as long at it has a DH lower than 300 ft. I don't have a problem with that, the airport has an LPV approach with LPV minimum of DH 250 ft.
Now for the non-precision approach, I am going to use the same approach but flying the LNAV minima. So my question, since I haven't flown LNAV minima since my IFR training, my question is: Can I fly the LNAV MDA even if the GPS annunciator is on LPV mode? I guess the answer is yes, so, is there any consideration when doing that?
And just for future applicants, an LPV approach with greater than 300 ft DH can be used to satisfy the Non-precision approach task on the ACS (instrument ACS  page A-17).

GPS approaches are designed for you to fall back to LNAV if a 'higher' precision option like LPV fails during the approach. Just like going from ILS to localizer only if the glideslope fails.
The Instrument Procedure Handbook p. 4-26 says:

Flying a WAAS LPV approach requires an aircraft with WAAS-LPV
avionics. If for some reason the WAAS service becomes unavailable, all
GPS or WAAS equipped aircraft can revert to the LNAV MDA and land
safely using GPS only, which is available nearly 100 percent of the
time.

So you can just ignore the vertical guidance and fly the LNAV step downs using lateral guidance only from the GPS, and your regular altimeter (not your GPS) to identify altitude.
If you haven't done it already (or recently), I'd suggest practicing it before your checkride to see how your avionics behave. You might get alerts that you have to ignore and they could be distracting. It would be best to get a feel for that ahead of time rather than experience it for the first time with an examiner sitting beside you.
You can also just check with your examiner in advance that they're comfortable with what you want to do.


Do stratospheric business and military jets use the North Atlantic Tracks? The North Atlantic Tracks (NATs) are the airways generally used by airliners taking approximate great-circle routes between North America and Europe; due to the wild swings in wind strength and direction over the North Atlantic from day to day and place to place, the NATs are not fixed in position, but, rather, are plotted fresh every morning to allow transatlantic flights as much tailwind (and, thereby, as much groundspeed and as much per-flight fuel efficiency) as possible, and, then, sent to all the airlines preparing aircraft for transatlantic runs.

In contrast, the weather in the stratosphere - the layer of air lying above the tropopause (the upper boundary of the weather-prone troposphere; usually lying between 35 and 50 kilofeet at temperate and polar latitudes, but generally located at a much higher altitude over the tropics) and below the stratopause (the upper boundary of the stratosphere, and the lower boundary of the poorly-known mesosphere; usually located at around 165-180 kft) - is essentially uniform constant from day to day, changing (usually) only slowly, with the seasons.  This removes the raison d’etre for the moving NATs, as no particular stratospheric route is objectively significantly better than any other of comparable length.  For this reason, the Concorde (cruising at flight levels [FLs] 470-600, equating to an altitude of 47-60 kft, give or take a kilofoot or so)1 did not use the NATs, instead following, for open-ocean stratospheric cruise, one of a set of preplotted fixed airways, the locations of which did not change from day to day.

But the Concorde, even when it was still in service, wasn’t the only aircraft to cross the North Atlantic in the stratosphere; business jets (at least the many that are actually capable of doing so) routinely cruise at between FL 450 and FL 550 or so (the exact upper limit depending on the model of bizjet), and some smaller military jets routinely cruise above FL 600 in order to minimise aerodynamic drag on long-distance flights.  These other high-altitude jets would stand to benefit just as much as the Concorde did from being able to use fixed stratospheric airways rather than having to follow the variable and non-stratospheric-aircraft-benefitting NATs; yet, I’ve only ever come across mention of immobile stratospheric routes with reference to the Concorde, and in language that makes it sound like the Concorde was unique in its use of these routes.

So do stratospheric bizjets and military jets have to use the NATs (and, if so, why?), or do they get to use fixed stratospheric routes, like the Concorde did?

1: An aircraft’s flight level is the altitude, in hectofeet, that its barometric altimeter (if properly calibrated, and assuming the aircraft’s pitot-static system is working properly) indicates when set to standard pressure (29.93 inHg).

The tropopause is in the low to mid 30s in the mid-north latitudes that the NATs reside (and is in the 20s in the arctic in winter) so an airliner crossing on a NAT at 55 DegN at FL370 will be well into in the stratosphere.

Concorde didn't use the NATs simply because the NATs top out at FL410.  And in any case, the NATs are a large band of parallel tracks several hundred miles wide which are mostly just shifted more northerly or more southerly to accommodate weather patterns and the locations of polar jets etc.  The routings aren't really customized much more than that.

Anyway, because they top out at 410, if your jet can cruise above 410, like a Global or Gulfsteam, you can avoid the NATs and can pretty much file for whatever custom routing suits you that doesn't conflict with someone else.


How does Pack Flow work on the A320? I am referring to an Airbus A320. I have heard of Pack Flow but I don't understand it.

If you put it on High, does that mean that all the parts of the air conditioning system work faster and harder?

I have also heard that if you put it on High, that means the demand for air supply is high, and vice versa, i.e. if it's on low then the supply for air is low, but what about NORM, or Economy flow?

Source: FCOM A320 familly

From the flight crew operating manual (FCOM) about the pack flow selector (4):

  Permits the selection of pack valve flow, according to the number of
  passengers and ambient conditions (smoke removal, hot or wet
  conditions).
   LO (80 %)  - NORM (100 %) - Hl (120 %).

  Manual selection is irrelevant in single pack operation, or with APU
  bleed supply. ln
  these cases, Hl is automatically selected.

  lf LO is selected, the
  pack flow can be automatically selected up to 100 % when the cooling
  demand cannot be satisfied.

So to answer your question directly:

The normal flow (100%) is when the selector is on position NORM.
Position HI adds 20% to the air flow, and LO removes 20%.

In addition:

In LO position, the flow can be increased by the controller up to 100% in case the temperature cannot be obtained with only 80%.
In case of single pack operation, the flow is automatically set by the controller to 120%.


Why is the UAE the only country with two flag carrier airlines? The United Arab Emirates has two flag carrier airlines, Etihad Airways and Emirates. There are 195 countries in the world, and 147 of them have one single flag carrier airline. United Arab Emirates is the only one with two. Is it just a chance occurrence?

flag carrier airways

Because the United Arab Emirates is, as the name suggests, a federation of seven loosely-affiliated emirates (the largest and most populous of which are Abu Dhabi and Dubai, in that order), each with its own royal family.  Emirates is based in Dubai; the Emir of Abu Dhabi, Sheikh Khalifa (who also happens, by longstanding convention, to be the president of the UAE), wanted his emirate to have its own flag carrier, and so Etihad came into being (founded by Sheikh Khalifa's personal pilot, no less).


Does the stream of engine thrust act as a good drag shield against the nacelle? Taking a look at the typical large engine of a commercial plane, it looks rather unstreamligned. Nacelle drag is significant IIRC.

However, then I suddenly remembered these engines produce a large jet of thrust (most of the time). Does this air stream of thrust act as a good shield against nacelle drag? Does it effectively form a bell cone, or half of a seers-haak body, around the rear half of the nacelle?

If so, that would appear to cut the nacelle drag in half.

The nacelle is not some solid block. For the flow it looks like a hollow, slightly blocked tube.

The flow ahead of the nacelle is indeed slowed down in flight, but only a little, entering the intake face at a flow speed of around Mach 0.4 to 0.5. This compresses the air ahead of the nacelle when flying in cruise at around Mach 0.8, so what enters the intake is already slightly compressed. Note that this compression does not involve boundary layers or shocks, so it is very efficient. The effect of the compression is that some of the air flowing towards the nacelle is pressed aside to flow around it. To avoid flow separation, the intake lip is rounded.

Pre-compression helps, because it raises the pressure in the whole engine and increases its thrust. What might be looked at as drag is in fact increasing the thrust of the engine! Of course, by further compressing and heating the ingested air the engine accelerates it, so the outflow speed of the core flow is easily double its entry speed. The outflow fills up the cross section of the engine, so the outer flow never has to flow into a void and experience separation (which is responsible for most of the drag of blunt bodies). Instead, it meets a faster jet of air once it has passed the engine fairing and is accelerated during the mixing process.

Only if the engine is idling or off will the nacelle cause real drag.


Why don't DO guidelines have examples? As per DO-178 C section 6.2 Overview of Software Verification Activity

  b. When it is not possible to verify specific software requirements by exercising the software on a realistic test environment, other means should be provided and their justification for satisfying the software process objectives defined in the Software Verification Plan or Software Verification Results.

After reading this every/most of verification engineers would understand it as other verification methods like Analysis, Inspection etc...

As per the discussion and Arguments "The real intent of this objective is how do we verify the software when hardware is unavailable" like, using simulator to verify the software needs to be documented under SVP for this objective satisfaction.

The question is, DO (document Order) as evaluated from version A, B to C now and still have ambiguities and different understandings. Why don't FAA/JAA can come up with examples or layman language explanations for each objective?

RTCA documents are not FAA documents, although the FAA is usually a member of the Special Committee that creates the documents. If an example is to be added, it is the decision of the SC, not of the FAA.

The reason that no examples are given is that the recommendation is clear by itself. A good V&V engineer will read this recommendation and use his skill, experience and creativity to find an other acceptable means to validate the software requirements that can not be validated in a realistic environment. This alternative means is then documented in the SVP.

Giving an example is not helpful at all, since the solution will depend completely on the software under test and the nature of the requirements.

If the hardware is not available, an emulator may be the solution.

In other cases artificial test inputs have to be generated, because failing a test in a realistic environment may prove to be catastrophic.


Why does a Thrust Vector Control System increase maneuverability? So why can a thrust vector control system increase my maximum g-load capacity? Because still n=L/G is relevant and if I can not provide enough lift (pointing up) to counter balance the thrust (pointing down to spin a missile around c.g.), why should I use it?

The point of thrust vector control is post-stall maneuvering.
Control surfaces lose much of their effectiveness when the flow over them is separated. Pointing the jet exhaust in different directions works almost regardless of angle of attack. All that is required is good intake flow, and by placing the intake below the forebody (as done on the X-31, the F-16 or the EF-2000), this is still possible even at high angles of attack.
Post-stall maneuvering enables the airplane to point its sensors and weapons in the direction of an opponent within seconds of detection. Compare that to flying a turn at Mach 0.8 over maybe 150°. At 6g (= 80° bank angle), this takes 11.5 seconds, assuming a speed of 256 m/s (which is Mach 0.8 at medium altitude) and an instantly achieved maximum turn rate.
By attaining a very high angle of attack in order to slow down the airplane and thrust vector controlled rotation of the fuselage into the direction of the opponent (Herbst maneuver), an airplane can turn much quicker and, consequently, shoot earlier. This is critical for winning in air-to-air combat.


Under what authority can the AIM overrule the FARs? A commonly held belief among pilots is that the FARs are regulatory, while the AIM is not. Violation of a regulation in 14 CFR is punishable by the FAA, while the AIM contains mostly "good ideas" and violation of its precepts is only punishable to the extent that it rises to the level of FAR 91.13 (careless and reckless operation). The FARs must be published in the Federal Register and generally be subject to the rulemaking process, while the AIM can be updated by the FAA at any time, with no input from anyone outside the Administration.

With that background, consider a note in the AIM, at the end of section 5-4-5(l) about Fly Visual approach segments, on page 5-4-20 (page 346 of the current PDF version of the AIM):

  NOTE−
  The  FAA  Administrator  retains  the  authority  to  approve
  instrument approach procedures where the pilot may not
  necessarily have one of the visual references specified in
  14 CFR
  §
   91.175 and related rules. It is not a function of
  procedure
  design to ensure compliance with
  §
  91.175. The
  annotation  “Fly  Visual  to  Airport”  provides  relief  from
  §
  91.175 requirements that the pilot have distinctly visible
  and identifiable visual references prior to descent below
  MDA/DA.

This is, as far as I can tell, the only location where this exemption from FAR 91.175 is described. FAR 91.175 is quite specific in the elements needed before continuing beyond the DA/MDA, and does not stipulate that the Administrator has the authority to authorize exemptions. For an example of one that does, consider FAR 91.117(a):

  Unless otherwise authorized by the Administrator, no person may operate an aircraft below 10,000 feet MSL at an indicated airspeed of more than 250 knots (288 m.p.h.).

What authority gives the AIM the ability to carve out an exception to the FARs? Are there other situations where the FARs are contradicted by a non-regulatory document without explicitly allowing exemptions or authorization by the Administrator?

The issue you have appears to be that the AIM describes a case where procedures don't follow a rule (91.175) and you don't see where the authorization comes from for that deviation.

What you're missing is that the approach procedures are in fact rules themselves.  They just don't get published in Title 14 CFR.  Standard instrument procedures are covered by Part 97, Subpart C.  It essentially states that the procedures are controlled via the FAA Order 8260 series.

So if the approach procedure specifies minima or other procedures outside the norm of a separate rule, the procedure is the controlling rule.


What is the physical meaning of Mean Aerodynamic Chord? I have not been able to find a consistent definition of what it really is.

I have come across definitions such as: "Physically, MAC is the chord of a rectangular wing, which has the same area, full aerodynamic force and position of the center of pressure at a given angle of attack as the given wing has." which is contradictory with this one "The mean aerodynamic chord is (loosely) the chord of a rectangular wing with the span, (not area) that has the same aerodynamic properties with regarding the pitch-moment characteristics as the original wing."

I am very confused and I wonder if you could please give me a precise definition (maybe in relation to an equivalent rectangular wing, as those two definitions I found), that shows intuitively what it is

The mean aerodynamic chord is only identical to the mean chord for rectangular wings. For tapered wings it is slightly longer.

Why? Because the mean aerodynamic chord is the mean chord of a rectangular wing that has the same pitch characteristics as the "real" wing. Pitch characteristics need to include pitch damping, and pitch damping grows with the square of the local chord. That is why the formula for the mean aerodynamic chord divides the square of the local chord by the wing area:
$$\text{MAC} = \int_{y=-\frac{b}{2}}^{y=\frac{b}{2}}{\frac{c^2}{S}}dy$$
Here $b$ denotes wing span, $y$ the spanwise coordinate and $S$ the wing area. Since the chord is squared, deeper sections of the wing are overrepresented in the result. The resulting rectangular wing will have a larger area than the original, tapered wing but the same pitch damping! In case of a delta wing, MAC will grow to be ⅔ of the root chord, and for an elliptical wing it will be 90.5% of the root chord.

The MAC has been invented to convert arbitrary wing planforms into much easier to calculate rectangular wings. By doing all calculations on the correctly sized rectangular version, the more complicated calculations on the real one could be avoided. However, this works only up to a point:

if you want to calculate lift, you need a wing of equal area.
if you want to calculate induced drag, you need a wing of equal span.
if you wand to calculate pitch motion, you need a wing of the correct MAC. This rectangular wing can either have the same area or the same span as the real wing, but not both together, unless the real wing is rectangular, too.

You are right, the two definitions you quote are not compatible. The rectangular wing cannot have the same span than the real one, or its area and all associated forces and moments would be higher.


Is it allowed to mount fake missiles on a civilian aircraft? In this answer to a question asking to identify an aircraft, we can see a picture of a Aero L-39 Albatros with some missiles hanging from the wings:

(flickr.com) N915WE.

Supposedly, this is a civilian airplane, and another user pointed out the oddity in a comment. The author of the answer then replied that [those missiles] "are as real as this being a USAF L-39 ;)". This second picture shows an airplane with "United States Air Force" painted on it.
Does this mean that it is perfectly legal for a civilian aircraft to mount some fake missiles? And to write "USAF" on an airplane that doesn't belong to the USAF, even? Especially considering this airplane can really be configured as a military one, with real missiles!

To me this looks like going through security checks at the airport with a fake gun in your hands. Sure, it's fake and it can't harm anyone, but I'm not sure the police would appreciate my sense of humour.

Seriously, is this allowed? With all the attention to security (which often borders on paranoia), it is allowed to fly around with fake missiles? Won't this lead to unnecessary confusion, fear, and even false alarms?

Importing former military aircraft

  Former military aircraft imported from ANY other country require an import permit issued by the Department of Treasury, Bureau of Alcohol, Tobacco, and Firearms (ATF). This is granted by ATF using an ATF Form 6, Application and Permit for Importation of Firearms, Ammunition and Implements of War. Additionally, these former military aircraft are required to be demilitarized in order to clear U.S. Customs (FAA).

Getting a certification

  Unless the aircraft are used for an approved civil research and development (R&D) project, former military aircraft owners/operators must permanently demilitarize their aircraft before FAA certification (FAA).

So those aircraft are permanently demilitarized and cannot release ordnance or fire bullets. Since there are multiple examples, it is legal (in the US at least), and with the demilitarization there is no worry such aircraft would be able to release live ordnance if the owner somehow was able to obtain some.

Inert missile

I wasn't able to find text regarding mounting fake missiles, but a line from Dr. Strangelove came in handy:

  Air Force Base Guard
  You sure gotta hand it to those Commies -- Gee, those trucks sure look like the real thing, don't they? -- I wonder where they got 'em from? -- Probably bought them from the Army as war surplus...

I found inert ordnance for purchase, like the one above. And the blue line on the missile on the L-39 indicates it "does not contain a live rocket motor".

Livery

In AC 45-2E I did not find anything about using USAF or foreign military markings, but most probably that falls under freedom of speech in the US.

Related: Why can civilians not fly demilitarized US fighter jets?


What would happen if a plane lost half of its weight instantly? During the Second World War the RAF had a 10,000 kg bomb, the "Grand Slam", which was dropped from a Lancaster bomber.

I assume that when this was dropped the plane would lurch upwards.

Is there any way of knowing just how big and violent a movement this would have been?

According to Wikipedia, a 'loaded Lancaster' weighed 25,000 kg. I'm not sure if this includes a standard bomb load (approx 6,350 kg) or not, but either way it seems that when the "Grand Slam" was dropped the aircraft would, in an instant, reduce to about half or two-thirds of its previous weight.

Is there any way to estimate how big an upward jump this would cause?

In steady flight, the lift $L$ generated by the wings equals the loaded weight so that there is no vertical acceleration.  Thus, the lift just before the bomb is dropped is
$$
L = m_1g =  245\,250 \;\textrm{N}
$$
where  $m_1=25\,000$ kg is the loaded mass and $g=9.81$ m/s$^2$ is the acceleration due to gravity.

In the time interval just after the $10\,000$ kg bomb is dropped, the lift remains the same until the lift is reduced to again balance the new mass of $m_2=15\,000$ kg. During that transient period, the Lancaster will accelerate upwards at
$$
a = \frac{L-m_2g}{m_2} = \left(\frac{m_1-m_2}{m_2}\right)g
$$
which works out as an upward acceleration of two-thirds of a "gee":
$$
\frac{a}{g} = \frac{m_1-m_2}{m_2} = \frac{2}{3}
$$

As @sanchises pointed out, the steady increase in the upward velocity results in a decrease in the angle of attack, so that the aircraft will again settle in a steady climb.


Is airspace more crowded on days following cancellations or a large number of delays? I am looking at some data form the BTS and trying to understand some spikes in month to month Volume delays. From my understanding a Volume delay is due to the volume of airplanes, causing the ATC to manage more take offs and landings and therefore slowing down the whole process.

My problem is that for volume delays bts only provides monthly aggregates. So I have data with a spike for Volume but the number of flights on that same month is normal or sometimes less than average. So I am assuming that something is happening at the daily level that is completely lost in the aggregation.

This all boils down to my question. If we where to quantify the capacity of the airspace around say ORD and call it X and on average the airspace is occupied with N planes, such that N < X and airspace is operating at N/X capacity.

On days following mass delays or large number of cancellations, does the amount of planes in the airspace increase to alleviate the pressure of passengers who are behind schedule? or does the load factor simply increase?

For examples say that on average airspace at ORD operates at 75% capacity, then one day you have some event that causes a lot of delays and cancellations. Do the following days operate at say 90% airspace capacity to help relive that congestion? or do they still operate the same number of planes but those planes are simply almost guaranteed to be full.

All summed up, would a spike in delays for some reason other than plane volume result in a spike in volume delay in the following days as they deal with the extra passengers?

Sorry if this question is worded strange, I had a hard time putting it down in writing. If its unclear let me know and I'll try to clarify.

I would say generally no, because there are only so many landing slots available at busy airports and airlines frequently substitute larger aircraft to clear up a passenger backlog.


What will happen if satellite navigation fails? My understanding is that aircraft use GPS systems for navigation (maybe not the only way to navigate). I would like to understand what would happen if the GPS system fails.  Are there any other navigation systems to fall back on? What would happen if all of them fail? Could all the navigation systems fail?

It only takes 3 satellites for a GPS fix (4 if you want altitude). There are 31 operational satellites currently in orbit and at any given time you can most likely receive a signal from half a dozen of them at least. That being said the chances of them failing completely is almost 0%. But of course what if they did, well...

There is always the Russian version of GPS known as GLONASS so there is effectually an entire redundant global navigation system in space. While not all aircraft are equipped with GLONASS receivers it is of course becoming more common. Even the little tiny receiver I use for GA flights has it now. So there is that redundancy.

In controlled airspace you have ATC there to help you. They can effectively watch you on radar and tell you what to do which is basically what flying IFR is. For this you will need an operational altitude encoding transmitter so that ATC knows your altitude along with position. If you are flying VFR and require assistance you could call for Flight Following here in the US, load permitting. They can offer limited guidance but if you tell them you are lost they will generally help.
If there is no ATC you can hone in on VOR stations, or some of the older radio direction finders like ADF systems assuming your aircraft is equipped with such equipment. Some modern handheld radios can also hone in on VOR stations

If all that fails you have your good old magnetic compass and hopefully some way of keeping time. With close track of your airspeed, a clock, and a compass you can navigate pretty accurately even in the blind (although I don't recommend that).

No compass, no problem, you always have your ground reference points to get where you need to be. Basic VFR navigation which every pilot know how to do is learned this way. This will require you have a VFR map of the area which most GA planes will carry. Note the roads, power lines and other large things marked on the map that are easily identified from the sky.

Outdated/less popular systems:
Inertial navigation systems are still used in plenty of places however they are not as accurate as other systems available in modern aircraft but they work by knowing how fast you have gone and in what direction you have accelerated to that speed. Thus position can be calculated. INS systems suffer from integration drift which can add up over time and make the margin of error pretty big.
There was once a time in history when you could get a navigators rating on your license. These people were trained in many times of navigation including celestial navigation. Older planes were even outfitted with a sextant for that very reason.

LORAN C was officially shut down here in the US/Canada in 2010 but there are still active chains elsewhere in the world. Some planes out there still have the units in them (one of the Cherokees I fly still has it sitting there). So depending on where you are you may be able to use it.
What Time Is It:
The US GPS network is synced up via the USNO master clock and while it is unlikely that all the satellites will fail simultaneously or fall out of the sky, or be shut down. The master clock does provide a central point of failure for the system. While I am not up to date on the full function of the system I would imagine that a downed clock could introduce a margin of error into the system. Worse so an incorrect value fed from the master system may cause an erroneous reading.


Is pressure pattern navigation used in the real world? How effective is it really? Pressure Pattern Navigation is a method of capturing favorable tailwinds when flying long-distance trips.

The basic methodology can be found in this PDF.

I imagine that airline captains aren't all that free to choose their routes (correct me in the comments if I'm wrong!), but this seems to be perfectly suited for the corporate and charter crews among us. However, I've never heard of any crews using it in real life.

Does pressure pattern navigation work in the real world? How effective is it?

It is used in the real world, especially by airlines. The best example is the North Atlantic Track system. The tracks are tailored every day to maximize the tailwind on West to East crossings and minimize the headwind East to West crossings.


Under what conditions is a flight attendant required on an aircraft? Not all airplanes with passengers are required to have flight attendants.

What are the regulations that cover this and when are they required?

14 CFR Part § 121.391.

It depends on the size/weight of the airplane and how many passengers it can hold

  Except as specified in § 121.393 and § 121.394, each certificate
  holder must provide at least the following flight attendants on board
  each passenger-carrying airplane when passengers are on board:

  For airplanes having a maximum payload capacity of more than 7,500 pounds
  and having a seating capacity of more than 9 but less than 51
  passengers—one flight attendant.
  For airplanes having a maximum
  payload capacity of 7,500 pounds or less and having a seating capacity
  of more than 19 but less than 51 passengers—one flight attendant.
  For airplanes having a seating capacity of more than 50 but less than
  101 passengers—two flight attendants.
  For airplanes having a seating capacity of more than 100 passengers—two flight
  attendants plus one additional flight attendant for each unit (or part of a unit)
  of 50 passenger seats above a seating capacity of 100 passengers.

http://www.gpo.gov/fdsys/pkg/CFR-2011-title14-vol3/pdf/CFR-2011-title14-vol3-sec121-391.pdf

Parts § 121.393,394 relax these requirements when a plane stops, but denotes how close by the flight attendants must be, and other things like exit door requirements.

Remember, Flight Attendants are there for your safety :) which is the motivation for these regulations.

[Edit]
14 CFR Part 91.533 covers flights operated under "Part 91" regulations:

§ 91.533 Flight attendant requirements.

  No person may operate an airplane unless at least the following number of flight attendants are on board the airplane:

  For airplanes having more than 19 but less than 51 passengers on board, one flight attendant.
  For airplanes having more than 50 but less than 101 passengers on board, two flight attendants.
  For airplanes having more than 100 passengers on board, two flight attendants plus one additional flight attendant for each unit (or part
  of a unit) of 50 passengers above 100.

  No person may serve as a flight attendant on an airplane when required by paragraph (a) of this section unless that person has
  demonstrated to the pilot in command familiarity with the necessary
  functions to be performed in an emergency or a situation requiring
  emergency evacuation and is capable of using the emergency equipment
  installed on that airplane.

It looks like the "training" to act as a Part 91 Flight Attendant is just showing the pilot they are capable.

The big difference between Part 121 and Part 91, is number of seats (potential capacity) vs. people actually on board.  This is interesting in light of the recent 787 Boeing Business Jet deliveries (http://boeing.mediaroom.com/2014-02-05-Boeing-Business-Jets-Delivers-First-Two-BBJ-787-8s-of-2014).  So if it was just the owner and the pilot crew, there wouldn't need to be a flight attendant (assuming, of course, they're operating under Part 91), even though it is a huge plane.


Why does the QNH of an aircraft change or need to be changed? This is mainly a 3 part question.

First, is it the QNH of

of the aircraft?
of the aerodrome?
of the region or area?

Or am I understanding it wrong my looking at it like that?

If the QNH is set to show the airfield elevation above mean sea level, would it change at a specific aerodrome? And if so, why?
What are areas of low and high pressure and why would the QNH need to be changed in those areas?

The QNH is the reference pressure of the aerodrome, not the aircraft. It is calculated such that an altimeter, which assumes ISA conditions otherwise, shows the correct altitude above mean sea level at the aerodrome:

  Airfield QNH is obtained by correcting a measured QFE to sea level using ISA regardless of the temperature structure of the atmosphere. As your altimeter is calibrated using ISA, it will indicate altitude correctly at the airfield reference point. At other altitudes, the indicated altitude is likely to be in error, depending on the temperature of the atmosphere.

(skybrary.aero)

The altimeter uses the following formula to compute altitude:

$$ h = c T \log \left( \frac{P_0}{P} \right) $$

Here, $c$ is a constant, $T$ is the temperature (which is assumed to be the ISA temperature, not the actual temperature here) and $P_0$ is the QNH reference pressure. The altitude $h$ is then exactly correct at the aerodrome and also quite accurate above if the actual temperature does not deviate from ISA too much.

The QNH value is typically obtained from the ATIS or from ATC. It is given in units of hectopascals (average value of 1013 hPa) or inches of mercury (average value of 29.92 inHg).

The QNH changes whenever the pressure at the aerodrome changes because the altimeter is using the pressure to determine altitude. These pressure changes are a normal part of changes in weather. You can see an example surface pressure map of the US here:

(image source: Wikimedia)

Note that the pressure values (in hPa) on this map are not the QNH values. These are the current actual surface pressures.


Why do some military jets have needle-like structures at the nose and others don't? I have seen some military jets have a needle-like structure at the nose and some others do not have that. Lockheed SR-71 Blackbirds have that structure and Lockheed Martin F-22 Raptors do not, why so?

(Image Source: www.aviationexplorer.com)

(Image Source: www.wikipedia.com)

What you see on the SR-71 is an Alpha-Beta probe, with a pitot tube branching off the side of it. The nose cone of the SR-71 (and its variants) were changeable depending on its loadout.

From the A12 Configuration:

  The sharply tapered nose section was pressurized and contained navigational and communications equipment, a
  remote compass transmitter, periscope optics, air inlet computer and angle transducer, and other radio equipment.
  A combination pitot-static and alpha-beta probe was installed at the forward tip to capture airspeed and altitude data.

About the SR-71 versatility

  The SR-71 also served as a testbed for an Optical Air Data System (OADS), a fiber optic device using laser
  technology to replace the pitot tube (airspeed probe) on high-performance aircraft. It used laser light instead of air
  pressure to produce airspeed and attitude reference data such as angle of attack and sideslip normally obtained with
  small tubes and vanes extending into the air stream or from tubes

Both sources above: Design and Development of the Blackbird

The F22 serves quite a different purpose to the variants of the Blackbird, and thus probably has less need for sensitive sensor equipment of the SR-71. It still has a pitot tube which can be seen in the photo you posted

And it, no doubt gets other avionic information from a traditional pitot-static system rather than rely on an alpha-beta probe as the Blackbird did.


How to select the most efficient airfoil for low speed flight? What airfoil (or family) has the highest $C_L/C_D$ ratio at speeds in the $50\:km/h$ range.

The use case would be an ultralight with a max speed of $50\:km/h$

Please read the answer to this question first and try to answer the questions listed there. You need to provide more information!

Next, the best place to look is among glider airfoils. The Wortmann FX 63-167 is now 55 years old but still a good start. It was designed for the low speed of a human powered aircraft and has been used on gliders and motor gliders.

But the airfoil still can be improved, for example by adding flaps or by narrower tolerances for the surface contour, especially around the nose. But this will make construction more complicated, so the overall best compromise might still be the Wortmann airfoil.


What additional considerations do pilots have when deviating from the planned routing on flights dispatched under Method 2? This article about Method 1 and Method 2 gives a brief explanation of Methods 1 and 2 in terms of dispatching flights under 14 CFR 121. Here's an excerpt.

FAR 121.191 requires that we dispatch our aircraft on a routing, weight and expected enroute temperature, that complies with a minimum terrain clearance requirement after an engine failure.
It also requires that we have a plan in place that allows a diversion to an alternate airport enroute,  following an engine failure and drift down, with a specific terrain clearance if we do not have the performance to continue to the destination.

My question about flights dispatched under Method 2 concerns route changes. In practice, I'm quite sure that pilots operating aircraft with a Method 2 dispatch release deviate from the planned route on the dispatch all the time. Reasons might include a shortcut request to air traffic control or deviations for weather. Weather deviations seem like the most relevant here because they can sometimes be quite significant.
What additional considerations do pilots have when accepting route changes on flights dispatched under Method 2? Couldn't changing the route render the Method 2 calculations irrelevant?

As a Former Dispatch Examiner and an Airline Part 121 pilot for most of my career I think what you are looking for is this:

Unless the terrain is such that they must adhere to or close to the desired routing and they are notified of this, most deviations are inconsequential. It also depends on how many engines are on the aircraft. A twin engine aircraft must land at the nearest suitable airport in the point of time after an engine failure. Although it is wise to land with a greater than 2 engine aircraft, that is not the requirement. If an engine fails after takeoff before reaching cruise altitude the PIC should consider terrain clearance in his decision to continue, deviate or return. The PIC is responsible for his decisions and can deviate or not deviate if he feels his decision is as safe as the alternative. After drift down, most jets should clear all terrain with few exceptions but he should always consider obstacle clearance.

Remember everything in preflight must meet regulatory criteria. Once airborne the real world situation can alter and often does alter planning and some regulatory requirements. A lot of planning regulations go away after takeoff. The PIC is the final authority in all decisions after departure even though you both are considered responsible and should agree. If the crew has time to coordinate with Dispatch, then it is the dispatcher's job to warn the crew of all known hazards they may have overlooked while dealing with the in-flight problem even if they were briefed prior to takeoff.


Do headrests considerably increase safety on aircraft? When looking at newer GA aircraft, for example, Cessna 172s it is very obvious that the seat design has changed quite a lot over time. With the older ones having very short backrests and the newer ones being equipped with quite high seats including headrests the analogy to the automotive world is undeniable. Do the same reasons like impact safety apply to this development? Would it make sense to retrofit headrests for safety reasons?

You aren't going to get rear ended in an airplane, which is the primary safety benefit of headrests.  On the other hand, there is still some benefit to having them because in a hard forward crash, if you have shoulder harnesses on, you will probably get rebounded back into the seat to some degree or another, and the headrest will keep your head from snapping back too far during the rebound.  So better one there than not.

I've been following GA since the late 60s (I still have a FLYING magazine issue I bought at a corner store in 1969) and would say that they were mostly adopted in the 70s for "styling" purposes (keeping up with car interiors; there was a big effort to make GA airplanes as car-like as possible back then), but they aren't totally useless for protecting your neck in the right kind of crash scenario.

The really big sea-change in crash safety for GA aircraft was the adoption of shoulder harnesses, also in the 70s.  They made many crashes walk-away events that previously left you with fatal head injuries, or if you were lucky, you survived with a hamburger face.


What are the FAA/CS requirements for rubber chocks? What are the FAA/CS requirements for rubber chocks? Do they include material, manufacturing processes, etc.?

I could not find FAA requirements; however, there is an industry standard: SAE J348 (the details are behind a paywall).

A 1993 flightsafety.org publication emphasizes that chock placement and design are essential, for example:

  The chock’s height is very important and it depends on the size of wheel to be restrained. For heavy transport aircraft, a six-inch (15.2 cm) height for wooden or rubber chocks is effective in general ramp usage. For restraining an aircraft during ground run-up operations, most operators use larger, fabricated steel chocks of greater height, sometimes as much as 12 or 15 inches (30.5 or 38.1 cm).


Why was Pan Am Flight 103 flying over Lockerbie? Pan Am Flight 103 was a flight from Frankfurt to Detroit with stops in London and New York.

Why after taking off in London did it fly all the way to Lockerbie instead of going directly to New York? Take a look at these pictures.

The direct route you show is actually only a straight line on your map projection. The surface of the Earth is curved and the straight line between London Heathrow and New York JFK looks like this (courtesy of greatcirclemapper.net):

That still does not quite get you over Scotland, but the actual flight path over the Atlantic typically uses a North Atlantic Track. These are routes, which are redefined twice a day to make optimal use of the prevailing enroute winds. Here is one example for such tracks:

(image source)

The entry points to these routes can be quite high north, therefore resulting in an optimum route over Scotland.


Where can the ICAO recommendations be found? ICAO issues recommendations/rules/statutes/something? that standardizes the regulations for international air travel world-wide.

What are these "rules" officially called and where can they be found?  Are they available on the internet?

ICAO publishes and maintains 19 Annexes to the Chicago Convention. They pertain to all matters in aviation and provide the framework for national legislation in each of the member countries in the form of Standards and Recommended Practices (SARP).
In addition to the 19 Annexes, ICAO also produces more detailed guidance in the form of Procedures for Air Navigation Services (PANS): PANS-ABC, PANS-OPS, PANS-ATM. These are also usually referenced by their Doc number: 2007, 8168, 4444, etc
In addition to the PANS, for specific regions of the world ICAO publishes Regional Supplementary Procedures (SUPP) to incorporate regional variants/requirements.

Any ICAO contracting state may have local legislation different from SARP/PANS, but is obliged to notify ICAO of these differences. You will find these differences in the country's AIP section GEN.

Getting electronic copies of these documents is a bit more difficult.  ICAO sells these documents for a very 'aviation' price. Some CAA's and institutions will provide electronic copies in PDF form, but they will most likely be out of date and their legality is suspicious at best. Welcome to the world of international law.


Why is the speedbrakes rate of retraction 25 seconds when used at speeds greater than 315 knots/.75 Mach on the A320? While I was routinely reading the FCOM normal procedures I came across a note with regard to the speedbrakes retraction time going up to 25 seconds when we use them at speeds at or over 315 knots / .75 Mach.

Why is this ?

Please read the entire answer to understand the matter even if the answer goes a bit beyond the question.

On the A320 wings you have panels that may open upward and that could be used to fulfill 3 different functions: ground spoilers, speed brakes, roll spoilers.

The outer panels are used in addition to the ailerons for roll function, that is helping the ailerons only on one of the wing according to the turn direction.

The central panels are used in flight for the speed brake function as follows: when the pilot order is beyond a limit the Fly By Wire will provide protections because an excessive drag might damage the wing structure, so the higher the speed the lower will be their maximum angle of deployment and their speed of deployment even if the pilot gives a full order of deployment.

The drag produced by the air brakes causes a mechanical torque on the wings roots, a sudden removal of the drag would be similar to a stress cycle, therefore deployment and retraction are managed to protect the wing structure.  Any pitching effect of these surfaces in flight is automatically compensated by the FBW through the elevators.

At landing the ground spoilers function is as follows; all the surfaces are deployed fully if the function is armed.


How long is spin training good for in the USA? Written tests are only good for 24 calendar months before they must be applied to a certificate (or lost).  Spin training is a requirement of the flight instructor certificate.  Does the required spin training have the same limitation of life as a written test?  Or, is it like an endorsement where it's good "forever"?

CFI candidates receive a spin training endorsement with no expiration date. According to AC 61-65E (the endorsement appendix), it should look like this:

  46. Spin training: section 61.183(i)(1).

  I certify that (First name, MI, Last name) has received the required training of section 61.183(i). I have determined that he/she is competent in instructional skills for training stall awareness, spin entry, spins, and spin recovery procedures.

  /s/ [date] J. J. Jones 987654321CFI Exp. 12-31-05

The basis for this is that 61.183 doesn't specify a time period in which the endorsement must be received:

  §61.183   Eligibility requirements.

  To be eligible for a flight instructor certificate or rating a person must:

    [...]

    (i) Accomplish the following for a flight instructor certificate with an airplane or a glider rating:

      (1) Receive a logbook endorsement from an authorized instructor indicating that the applicant is competent and possesses instructional proficiency in stall awareness, spin entry, spins, and spin recovery procedures after providing the applicant with flight training in those training areas in an airplane or glider, as appropriate, that is certificated for spins; and


What are the bump outs on a Bell 430 helicopter for? On a Bell 430 helicopter, you'll see what look like short wings on the side. I've seen people fueling in them, so I assume they are fuel tanks, but do they serve another purpose? Do they have a name?

They are called sponsons and act as enclosures for the retractable main landing gear.  The 430's ancestor, the Bell 222, was equipped with the same fairings.


Why do Boeing planes have more flap settings than Airbus planes? The Boeing 737 and Airbus A320 are similar in size and performance. They are direct competitors. Boeing seems to have eight flap settings (1, 2, 5, 10, 15, 25, 30, 40) whereas Airbus seems to have four flap settings (1, 2, 3, Full).

What is the reason for Boeing having twice the number of flap settings? I believe it is similar on other models as well.

And some older Mooneys have infinite flap settings depending on how much you pump them up...

The reality is that there are no regulations on how many flap settings an airplane must have and on an airliner that may also have things like speed breaks or slats as well, flap settings may vary by design or simply by engineering choice.

Flaps are used for improved short field take off as well as to make a steeper approach at a slower airspeed. If Airbus can achieve desired performance with 4 settings there is no need to complicate matters and add to pilots work load.