Why aren't Rogallo wings or parafoils used in aircraft with fuselages? I was wondering why no aircraft with a cockpit and fuselage use Rogallo wings or parafoils. I'm guessing they would have the advantage of low weight, collapsibility (storage), and low cost.

Larger aircraft: Metallic wings

How much fuel could you store in the Rogallo wings if you need some?

Source

The wings provide lift, but not only. In large aircraft they usually receive thrust from the engines, in order to transfer it to the fuselage, they are also fitted with hyper-sustentation devices and aerobrakes. And finally they can transmit a good part of the aircraft weight to the outer landing gears when the aircraft is on the ground.

Source

The latter functions are not compatible with a flexible structure. Only metallic or composite wings are used. They can be adjusted for an accurate envelope with optimized performances.

Smaller aircraft: Wood and canvas or metallic wings

The structure can be stiffened, this is commonly done, and leads to the concept of wood and canvas, as the DR-400 and many other GA training aircraft (all first aircraft were built this way):

Source

However these airframes don't scale well, and are not compatible with fast GA aircraft, leaving alone airliners speed range. Larger and faster aircraft, which anyway must protect their wing tanks, use metallic wings.

Ultralights and paragliders: Only categories with Rogallo wings

The advantages provided by flexible wings (easy storage, light weight, low cost) is a significant choice criteria for use in ultralights and paragliders, and of course for parachutes. These advantages overcome their limited aerodynamic performances, which is of lesser consideration for vehicles that are not specially aerodynamically designed.

Source

To summarize: The flexible wings are more appropriate for smaller and slower aircraft, in particular those not requiring wing tanks, wing control surfaces, or wing landing gears. Namely ultralights.


What is the purpose of air that passes through the engine core in a turbofan engine? Is it mainly to spin the fan rotor? The majority of the air going through the bypass is producing most of the thrust and providing the air that cools the engine.
Does is also provide the pressurization and cooling/heating for the cabins?
What is the purpose of the air passing through the core? Is the objective to spin the fan rotor even though it still produces thrust? Does it provide air for any other purpose such as cooling?

The core is the Internal Combustion Engine - it has intake (of air), compression (of air), combustion (of the fuel/air mix), and exhaust (water vapor, CO2, air) that provides the motive force to rotate the turbine (N2) and provide perhaps 25% of the actual thrust of the whole engine when it exhausts out of the tailpipe.
From How Do Jet Engines Work? on this same forum, we get this diagram to aid us:

This core may also provide the motive force for electrical generators, hydraulic pumps, bleed air, ant-ice etc. (it would be inefficient and make no sense to get these from the fan air).
The thus driven turbine via it's shaft rotates the compressor blades at the front/intake of the core thereby completing a loop and making this cycle self sustaining as long as there's fuel to feed the engine.
The turbine rotation and the compressor rotation and the flow of air so induced also make the fan (bypass) part of the engine rotate (N1) through aerodynamic coupling. Thus the fan cannot function without the core, but the core can function without the fan.
So, yes, the objective is to drive the fan rotor, because the fan rotor by itself is not an engine and cannot self-rotate with purpose of producing thrust, but it is a device that can be driven by an engine  to produce thrust, around 75% of the total thrust of a typical combination.


How are aircraft protected from lightning strikes by conductive skin? I've read this question and this one, but they don't really answer my question.

How or why are aircraft protected (from lightning) by a conducting skin, such as aluminum? Conductors allow current to flow through you! Wouldn't it be better to have an insulating shell?

I realize its not possible to have an ideal bubble completely protecting you, because the engines need to breathe air. Presumably these metal engines would then take the brunt of the lightning strike.

So let me try an example with a glider. Let's say we have a glider completely surrounded by an insulating skin. Just for the sake of ideal example, let's say this skin is the best material insulator known: diamond. (Okay, it's not solid diamond. It's just a diamond coating. Yes, they can build that via chemical vapour deposition. I know it's not economical, it's just for the sake of an ideal example.)

What would happen if this craft gets struck by lightning? Please don't say "it explodes" without some kind of citation or explanation or I will be suspicious of hollywood falsehood.

Lightning striking a metal aircraft

  A commercial aircraft [...] is struck several times during its whole service life.
  In such a case, the airplane acts like a lightning rod. Its metal structure provides the lowest resistance for the electrical discharge on its way between the clouds and the ground. It is not uncommon that the airplane is thereby struck by a complete series of discharges, mostly between three and five, in exceptional cases up to 25.
  Since an airplane in flight has no form of grounding, the lightning first enters the structure and leaves it again a split second later. The principle behind this occurrence is known by most people from physics lessons in school. The airframe acts as a so called "Faraday Cage". Like an automobile body the aluminium structure, when struck by a lightning, passes the electric energy around the interior and keeps the passengers safe.
  The crucial technical equipment is thereby also kept safe from the high voltage and the aircraft can, in most cases, proceed normally with its flight. But to play it safe every lightning strike is documented by the cockpit crew and the aircraft is treated with a special inspection routine on its next check.

  Source: "Lightning Strikes During Flight", Lufthansa Technik

Lightning striking modern aircraft with composite structures (as noted by this comment)

  Composite parts that are in lightning-strike prone areas must have appropriate lightning protection. [...] Composite structures are less conductive than metal, causing higher voltages.
  Lightning protection on airplanes may include wire bundle shields, ground straps, composite structure expanded foils, wire mesh, aluminum flame spray coating, embedded metallic wire, metallic picture frames, diverter strips, metallic foil liners, coated glass fabric, and bonded aluminum foil.
  Lightning can also damage composite airplane structures if protection finish is not applied, properly designed, or adequate. This damage is often in the form of burnt paint, damaged fiber, and composite layer removal.

  Source: "Lightning Strikes: Protection, Inspection, and Repair", Boeing, 2012

New technology improving the lightning protection of modern aircraft

  Traditional methods to protect composite aircraft from lightning strike damage rely on a conductive layer embedded on or within the surface of the aircraft composite skin. This method is effective at preventing major direct effect damage and minimizes indirect effects to aircraft systems from lightning strike attachment, but provides no additional benefit for the added parasitic weight from the conductive layer.
  A new multi-functional lightning strike protection (LSP) method has been developed to provide aircraft lightning strike protection, damage detection and diagnosis for composite aircraft surfaces. The method incorporates a SansEC sensor array on the aircraft exterior surfaces forming a "Smart skin" surface for aircraft lightning zones certified to withstand strikes up to 100 kiloamperes peak current.

  Source: Szatkowski, G. N. at al.: "Open Circuit Resonant (SansEC) Sensor Technology for Lightning Mitigation and Damage Detection and Diagnosis for Composite Aircraft Applications", NASA, 2014

Further information can be found on the internet, see for example "Playing with Lightning in the Name of Aircraft Safety", NASA.

For the science behind the Faraday Cage and lightning striking insulators, please refer to Physics.SE.


Do companies based in non-English-speaking countries require intra-cockpit procedural communication to be performed in English? I was watching a video of an MD-11 landing in Quito, Ecuador

The crew is German (Lufthansa).

When they speak with ATC it's in English (obviously).
When they speak with each other it's in German (also obvious).
But, when they go through flight procedures, they speak in English.

Why do they not speak in German?
Is this required for the Cockpit Voice Recorder?

In this exchange the pilot is talking through part of the approach with her copilot, who then says

  Genau

which means "I agree" in German, then immediately afterwards he says

  Gear down

notice how both sound very similar.  Further in the flight the copilot, calls

  Flaps 50

why not

  Flaps fünfzig

This is common in many international airlines.

Lufthansa Standard Operating Procedure (SOP) dictates that all flight procedural communication (checklists, standard callouts, etc.) are done in English.

The only "German" I've seen on Lufthansa's checklists is "handy .... off" in the pre-startup checklist (German English for "mobile phone .... off").


Why are pilots asked to provide a reason for a go-around? Why does the tower ask pilots what the reason is for a go-around? This seems to be standard for commercial flights.

The reason 1 pilot goes around may also be the reason the next pilot goes around, The second pilot would like to know before hand whether the runway is safe to land on.

For example if it is wind related he can delay landing until it dies down.

If it is debris related then the tower can dispatch a cleaning crew.


Do rudder pedals slide or hinge? I am planning on making a pair of rudder pedals from scratch. I don't know whether they should be hinged, or slide forwards and backwards.

On real aircraft, how do they work? Does it vary from plane to plane?

I've never seen "sliding" rudder pedals in a light GA plane - though there may be such designs in transport aircraft, especially fly-by-wire planes.

If you're looking for simplicity for a homebuilt aircraft or simulator I'd go with hinged pedals pivoting at the floor similar to what you'll find on a Piper Cub (which can be made by welding tubes together into an I shape), or any number of similar floor-mounted designs:

(As shown in the first picture, toe brakes can be easily retrofitted onto such a design, and as shown in the second you can mount square pedals on them if you want to, though the round bar has some advantages.)


At what distance between two aircraft will the air traffic controller get an alarm? I am developing an air traffic control radar simulation.

At what minimum distance between two aircraft in mid-air should a conflict alert be given?

The STCA (Short Term Conflict Alert) or pre-alert settings depend on the radar client in use and the ACC's or ARTCC's own standard operation procedures. Some ATC systems give a warning before a loss of separation can occur if criteria are met, informing the controller of a possible conflict. Factors can be clearing aircraft on the same altitude / flight level, aircraft on converging flight profiles, lateral or vertical separation reducing below threshold values, e.g. where 5nm lateral separation is required, a STCA could be set to occur at 7nm lateral separation.

The minimum radar separation between aircraft depends on airspace (TMA area vs enroute area), aircraft equipment and airspace separation requirements (RVSM vs CVSM), flight rules (e.g. IFR to VFR is not separated outside class C airspace in Germany) or local rules imposed by the Civil Aviation Authority.

The general rule of thumb for IFR separation in most countries (as most countries follow RVSM rules):

5nm lateral separation enroute (upper airspace)
3nm lateral separation in TMA area (lower airspace)
1.000ft vertical separation in lower and upper airspace where RVSM is observed and aircraft equipped
2.000ft vertical separation in non-RVSM airspace or between aircraft not equipped for RVSM

Oceanic separation is achieved differently, as non-radar procedures are in place. The separation in non-radar environments is achieved procedurally and through position reports and timing.


Why would a turboprop be better than an internal combustion engine for a UAV? Let us consider a UAV, long endurance high altitude (~26,000ft). Why would a user (most probably military) go for a turboprop rather than an internal combustion engine?

Mostly reliability, and weight.  A TP is far more reliable than a piston engine, and much lighter.  The TP's lighter installed weight makes up some for its higher specific fuel consumption.
You would use a piston engine to get operating costs as low as possible, and you're willing to live with lower reliability (you're forced to use turbocharging or supercharging, which reduces reliability further), and one of the new turbo-diesels would be the best option in that case (close to half the fuel burn of a TP and able to run on kerosene, or diesel perhaps).


Does ICAO allow continued flight in RVSM airspace after a transponder failure? If a civil aircraft's transponder fails in RVSM airspace, can it still be allowed to fly in RVSM according to ICAO?

And could it be allowed to fly in class A airspace, according to ICAO?

Note: I assume bare ICAO requirements in this answer. Most states that have RVSM implementations, as well as operator approvals for RVSM, will have additional stricter rules that will change the answer for specific cases.

There are no requirements in the ICAO Annexes and SARPS that require and aircraft the leave the RVSM airspace if the transponder fails.

Note that RVSM airspace is not necessarily airspace where ATS Surveillance services are offered, so for ATC purposes, a functioning transponder is not strictly necessary in RVSM airspace.

The only other use of the transponder that could prevent flying in RVSM airspace (under bare ICAO regulations) is the Airborne Collision Avoidance System (ACAS/TCAS). There are no requirements to have a functioning ACAS/TCAS in ICAO RVSM requirements, so no transponder is needed in support of such requirement.

Even if a transponder would be necessary to enter RVSM airspace (which is the case in for example EASA regulations), a transponder failure while being in RVSM airspace does (under ICAO rules) does not necessarily mean that the flight has to leave that airspace ASAP.

The following is from ICAO Doc 4444 (PANS ATM).

  8.8.3.3    AIRCRAFT TRANSPONDER FAILURE IN AREAS WHERE THE CARRIAGE OF A FUNCTIONING TRANSPONDER IS MANDATORY

  8.8.3.3.1    When an aircraft experiencing transponder failure after departure is operating or expected to operate in an area where the
  carriage of a functioning transponder with specified capabilities is
  mandatory, the ATC units concerned should endeavour to provide for
  continuation of the flight to the aerodrome of first intended landing
  in accordance with the flight plan. However, in certain traffic
  situations, either in terminal areas or en-route, continuation of the
  flight may not be possible, particularly when failure is detected
  shortly after take-off. The aircraft may then be required to return to
  the departure aerodrome or to land at the nearest suitable aerodrome
  acceptable to the operator concerned and to ATC.

  ...

Flight in Class A airspace without transponder is possible under ICAO rules, as long as the airspace is not surveillance airspace. Procedural air traffic control does not require surveillance, and a transponder is therefor not required.


How does the ground effect affects longitudinal stability? I recently learned that the ground effect increases the effective AoA of the wing and thus increases lift, how does that translates in to the tail plane and it's stabilizing effects? does it reduce/increase stability?

It depends on general geometry of the aeroplane:

The vertical position of the main wing and the horizontal tail.
If the aeroplane even has a horizontal tail.
The sweep angle.
The angle of incidence in the landing flare.

When a wing enters ground effect, its lift coefficient rises: the wing creates more lift at a given speed and Angle of Attack. A wing is considered to be in ground effect if it is within about half wingspan distance to the ground. Since the main wing has a much larger span than the horizontal tail, it enters ground effect earlier, creating a nose up moment due to more lift on the main wing only.  Low wing aeroplanes have a more pronounced nose-up effect than high-wing aeroplanes do.

 Image source

An increased nose up angle brings the horizontal tail closer to the ground, which will enter ground effect as well at a certain point. Which will the counter the nose-up moment.

A wing with large sweep, at landing angle of incidence, will see the wing tip area enter ground effect earlier, creating a nose down moment.

Concorde enters ground effect with the wing trailing edge first, creating a nose-down moment. In flight this would be called Increased Stability, however in the landing a nose down moment may introduce nose wheel slam.


Which timezone do airspaces that cross a time zone boundary belong to on a VFR sectional? The Albuquerque VFR sectional claims that the airspace table in the margin use local time, but some of the airspaces in the table cross timezone boundaries. Which  timezone do those airspaces belong to?

BRONCO 3 MOA is an example that crosses the New Mexico-Texas border and therefore from Mountain to Central Time:

See this excerpt from the margin which states that local times are used and lists the effective times for the Bronco 3 MOA:

So, in the case of the Bronco 3, are the listed "local" times MST/MDT or CST/CDT?

The times listed on the margin of the VFR Sectional chart are generally local time. In fact, the effective times that the FAA lists are also published in local time. However, in the case of a Special Use Airspace (SUA) that covers multiple time zones, the FAA specifies which time zone is used for local time.

The FAA publishes these details of SUA in the JO 7400.10A "Special Use Airspace".

You ask specifically about the Bronco 3 MOA. In the 7400.10A, the following details are currently published for the Bronco 3:

So, while Fort Worth Center is the controlling agency, the times of use are given in Mountain Time. This makes sense since the using agency is out of Cannon AFB in New Mexico.

Compare this to the nearby Lancer MOA (entirely in Central Time) for which the 7400.10A only lists the time as "local time":


What endorsements does a student pilot need to practice maneuvers solo with no limitations on distance from the airport? A question regarding the purpose of 61.93(a) and the distance limitations on a student pilot solo'ing in the local practice area.
Scenario:
A CFI trains a student in accordance with 61.87. They endorse a student pilot with the endorsements required in 61.87(c)(1)(2) as well as 61.87(n). The student solo's out to the local practice area and performs several maneuvers, but while doing so, goes 30nm from the airport. They return back and land at their home airport.
Did the student pilot violate 61.93(a)(1)(i), which says

Conducting a solo cross-country flight, or any flight greater than 25
nautical miles from the airport from where the flight originated

If this would be a violation, what exact requirements are necessary to meet for the student to just perform maneuvers in a practice area without a distance limitation (i.e. 25nm)? 61.93(a)(1) just says, "must meet the requirements of this section".

In my opinion, I think the wording of 61.93(a)(i) is pretty clear.  Anytime a student pilot flies more than 25 NM from their home airfield they will need an endorsement.
I don't know where you are based at.  At my home airfield, all the practice areas are within the 25 NM radius of the airfield.
If a student pilot gets a little outside of the 25NM radius then I would tend to belief they have violated the wording of the regulations.  If the student pilot is performing maneuvers in the practice area and accidentally exceeds that radius I don't believe they violated the intent of the regulation but the student pilot should be cautioned to stay within the defined radius.
This is at the heart of FAA's compliance philosophy.
https://www.faa.gov/about/initiatives/cp/media/CP_Brochure.pdf


I just flew into class B airspace without a clearance, what should I do now? Hypothetical: Let's say (for whatever reason) a pilot became distracted or disorientated, and found themselves in class B airspace.

What steps should they take immediately and after landing to be safe and avoid any backlash from authorities?

While still in the airspace, you should contact the controller if you can, since it may be important to safety.

After landing, you may get the dreaded phone number from a controller (probably tower or ground) which you're supposed to call and speak with someone from the FAA. You should not volunteer any information about the incident during this call without talking to a lawyer or AOPA legal services first.

Then, most importantly, fill out a report in the Aviation Safety Reporting System. Any information you submit will not be used against you in an enforcement action by the FAA, and in many cases, people who volunteer information through the system receive much softer treatment, and sometimes forgo enforcement all together.

The reason the FAA incentivizes this self-reporting is so they can better collect information about accidents which inevitably happen. If they know why you accidentally strayed into the bravo, maybe they can improve procedures or charts to help keep other pilots from making the same mistakes.


Why aren't we using drone blimp/hybird airship for delivery? Currently, the heaviest weight a commercial drone (the type that delivers Amazon package, not the type that delivers tons of stuff) can lift is 4.5kg with a 30-45 minute battery life. A drone blimp/hybird airship might be bigger and slower, but it would take less energy--the lift is generated by the balloon or some lifting surface instead of the propellers. Since the Boeing 747 win against the Concorde because it can carry more people with a cheaper price despite much slower than Concorde, why aren't we using a drone blimp/hybird airship to deliver Amazon packages instead?

There are many reasons why that will probably not happen.
Number 1: As of right now drones/blimps are very big for 1 package. It is much more efficient to use a car that can take in hundreds of packages.
Number 2: There are may types of drones/blimps that can be flammable exposed to certain chemicals. Also...where is the drone gong to fly? In airspace where planes are? Where is it gong to land? What about apartment buildings?
Thats why this is not plausible. Maybe one day it will.


Why do we still need ammeters? I just received my private pilot's certificate 2 weeks ago, yay! Earlier today, a fellow at work who has 700ish hours walked in and asked my office-mate-electrical-engineer "why do we still need ammeters, cars did away with them years ago, voltmeters seem mostly enough." He happens to be nearly done building his RV-14a. Office mate and I were at a loss for making a compelling argument for why aircraft still use ammeters. Is it just for redundancy's sake?

Congrats on earning your wings!
Because ammeters measure the flow of current (positive or negative) they can immediately show when the alternator is no longer providing power and the battery is discharging instead. In a voltmeter, like most modern automobiles have, you would have to wait to see the charge level on the battery drop, and by that point, several minutes (or longer) may have passed. In an aircraft, where it may be important to quickly shutdown electrical devices and conserve battery power, every moment counts and the ability to see flow shift from positive to negative is very helpful.


How to interpret the term "standard" which is found in FAA's Obstacle Departure Procedures (ODP) and Standard Instrument Departure Procedures (SID)? This might be obvious, but I find it difficult to interpret correctly the term "standard", when it refers to the takeoff phase of the flight.

Take, for example, the takeoff minimums for the La Guardia airport, page L16. For Runway 13, it states 400' ceiling height and 2¼ statute (I think) miles visibility but it does not mention any climb gradient. Is it implied that it follows the "standard" climb gradient of 200 feet per nautical mile? Next, it states that alternatively one can takeoff with the "standard" visibility rules, but only with a climb gradient of at least 280 FPNM until it reaches to 500 feet altitude. Which exactly are these standard visibility rules? The only source I remember finding states a requirement for 1 statute mile visibility for 1-2 engines aircrafts and 1/2 statute mile visibility for aircrafts with more than two engines, but no requirement for ceiling height.

Another example can be found by looking at this SID. Its takeoff minimums description states that for runway 4 "Standard" takeoff minimums apply. In addition, for runway 13, it states "400-2 or Standard with minimum climb of 280' per NM to 500." Does this mean that for "400 feet ceiling height - 2 statute miles visibility" the "standard" 200' per NM climb gradient applies, while for "standard" visibility a 280' per NM climb gradient is required?

I would be really grateful if someone could help me clarify the above rules.

The definition of standard minimum visibility for departure is found in CFR §91.175 Takeoff and landing under IFR.

f) Civil airport takeoff minimums. This paragraph applies to persons
operating an aircraft under part 121, 125, 129, or 135 of this
chapter.
(1) Unless otherwise authorized by the FAA, no pilot may takeoff from
a civil airport under IFR unless the weather conditions at time of
takeoff are at or above the weather minimums for IFR takeoff
prescribed for that airport under part 97 of this chapter.
(2) If takeoff weather minimums are not prescribed under part 97 of
this chapter for a particular airport, the following weather minimums
apply to takeoffs under IFR:
(i) For aircraft, other than helicopters, having two engines or less—1
statute mile visibility.
(ii) For aircraft having more than two engines— 1⁄2 statute mile
visibility.
(iii) For helicopters— 1⁄2 statute mile visibility.

The AIM 5−2−8 confirms your intuition about climb gradients.

b. What criteria is used to provide obstruction clearance during
departure?

Unless specified otherwise, required obstacle clearance for all departures, including diverse, is based on the pilot crossing the
departure end of the runway at least 35 feet above the departure end
of runway elevation, climbing to 400 feet above the departure end of
runway elevation before making the initial turn, and maintaining a
minimum climb gradient of 200 feet per nautical mile (FPNM), unless
required to level off by a crossing restriction, until the minimum IFR
altitude. A greater climb gradient may be specified in the DP to clear
obstacles or to achieve an ATC crossing restriction.

Note that visibility minimums do not apply to Part 91 aircraft. Also note that standard takeoff minimums do not have a minimum ceiling while published departure procedures almost always have a minimum ceiling or climb gradient—and often have both.


Why don't TAWS systems provide automatic avoidance? After watching several episodes of "Air Disasters" where the pilots' response to a TAWS (terrain awareness and warning system) alert was, "huh, that can’t be right", and then they fly into the terrain. I am left wondering why don't these systems actively avoid the terrain (pull up) automatically?

I would have to disagree with most of what John K has said. I will try to provide my own answer as well.

  Theoretically possible, but it would have to be a very expensive and complex sort of system, because it would have to manage pitch and thrust together, meaning it would have to integrate an autothrottle function in addition to an autopilot function

Current generation fly-by-wire aircraft have massive amounts of computing power and are capable of linking together autothrottle and autopilot actions already. Yes, it's expensive, but modern airliners are.

  the risk level of that sort of incident, which are pretty rare outliers really when you think of millions of hours flown each year, doesn't justify the development costs.

Indeed, thankfully, all accident types are enormously rare in modern aviation. However, that doesn't mean we stop trying to improve and CFIT (controlled flight into terrain) accidents are actually some of the more common and certainly warrant the development of safer systems.

My answer: As ymb1 has shown, this system does exist already. Why is it not on airliners yet? Well, I think it will be soon. But there might be a number of issues.

Firstly: false positives, where a terrain avoidance command is issued without need. Say, for example, an aircraft is coming into land and passes over a tall tree, this sets off the system needlessly and could very well cause further issues with traffic avoidance and airspace incursions - pilots would be hesitant about allowing such a system.

Secondly, aircraft performance. For the jet fighter in ymb1's video the aircraft performance, it's agility and power, and the pilot protection (e.g., helmet and 5-point harnesses) mean that this type of rapid terrain avoidance command is possible and effective. For any large commercial airliner, those sort of commands are not possible (much lower thrust-to-weight ratios etc.) and so the aircraft would have to respond to a terrain avoidance command a long way out - this would increase the likelihood and issues associated with my first point. Additionally, things are not as secure in an airliner and so there is the very real possibility of hurting people and breaking things when such a command is followed - if this is a do-or-die situation, then who cares! But what if it's a false positive and now you've just injured 50 people for no reason.

I'm sure there are other reasons. But having said all that aircraft designer are looking for solutions for CFIT accidents. Currently, for airliners, the main solution seems to be greater awareness for the pilots. So, using HUD/HGS (Heads up display/ guidance system). Some even now have special cameras at the front so that the surrounding terrain is overlayed on the HUD for use in low-light, low-visibility conditions. I guess that is the current solution for now. So expect to see greater use of HUD systems with terrain overlays in airliner cockpits.


What are the "Start & Acc" and "Pitch stab" circuit breakers for on the Piper Dakota? I am learning to fly a piper dakota and I found two circuit breakers for which I can't find an explanation:

Start & Acc circuit breaker. I understand that 'Start' is for the starter. What does 'Acc' stand for?
Pitch stab circuit breaker. I would think that this is related to the electric trim control mounted on the yoke but there is another circuit breaker labeled as 'pitch trim'. So what is this one for?

It is for (two) accessories and the starter, they are on the same 15A circuit breaker. The page you want to look at in the POH is Section 7.17 (this is figure 7-11):

I know the image isn't all that clear, but the 15A breaker is on the right side of the alternator buss. It includes the cigar lighter, cabin light and starter solenoid.

  Why would the manufacturer combine the starter circuit breaker with cigarette lighter circuit breaker? If the cigarette lighter is not working in flight..is it really wise to mess with the starter circuit breaker?

I'm not sure why Piper put those two things on there, but they did. I don't see it as a problem though. If the cigar lighter isn't working that isn't a problem, you wouldn't mess with the breaker. If it is melting a hole in the dash then yes, you pop the breaker, hopefully you wouldn't need to use the starter in-flight. I would consider the need to pop that breaker (due to heating/smoke) an urgent situation (maybe not emergency, but I'd divert to the nearest airport).

As for the "PITCH STAB", that is probably for an autopilot or altitude-hold system. The Dakota was available with a number of different autopilot options that operate separately from the electric trim system.


Is it possible to hack an airplane while it's moving (in general)? I recently searching Airbus Careers section, and I can say that I saw too many Cyber Security job positions. It was saying in the job description that there is a need of having knowledge about avionics and of other related sections. It was not focusing on Computer Science part.

My question is this: Is there a way that someone can hack an airplane? I mean each airplane is moving. How can someone "touch" a moving airplane, have the time to identify it and then to hack it?

Also, the airports are having really specialized machines and systems in order to communicate with an airplane. How can someone, without having specialized machines, can hack an airplane?

The answer to

  Is it possible to hack an airplane while it's moving?

is "theoretically yes, movement has no effect on a plane hackability".

  How can someone "touch" a moving airplane, have the time to identify it and then to hack it?

All the people inside the airplane are touching it during the whole flight, they know which airplane they are flying with, and they have a flight worth of time.

  How can someone, without having specialized machines, can hack an airplane?

Theoretically, for some components, you don't need specialized machines (see below), you need a laptop and an ethernet cable

see here (TL;DR version ), or here, and finally, from here

  First, the airplanes. The problem the GAO identifies is one computer security experts have talked about for years. Newer planes such as the Boeing 787 Dreamliner and the Airbus A350 and A380 have a single network that is used both by pilots to fly the plane and passengers for their Wi-Fi connections. The risk is that a hacker sitting in the back of the plane, or even one on the ground, could use the Wi-Fi connection to hack into the avionics and then remotely fly the plane.

  The report doesn't explain how someone could do this, and there are currently no known vulnerabilities that a hacker could exploit. But all systems are vulnerable--we simply don't have the engineering expertise to design and build perfectly secure computers and networks--so of course we believe this kind of attack is theoretically possible.

As we read here, though, safety critical components are not that easy to compromise:

  it’s essential to understand that aircraft systems can’t be updated in-flight or on the fly. This means that if an attacker is seated on the airplane, there’s no way they could modify systems. There are only three ways to update a system on a modern aircraft:
  1. Take the hardware off the aircraft and return it to the manufacturer for a factory performed update.
  2. Some larger airlines have their own maintenance organizations with the required specialized equipment to perform a bench update of a particular system using a portable data loader (PDL) or some other type of specialized data-loader.
  3. On-wing update [...] Specialized hardware (physical switch(es)) must be set, to place the IMA and relevant systems in maintenance mode. Once the aircraft systems are in maintenance mode, a maintenance engineer needs to follow a sequence of steps to push the update to the target system. The concept of an automatic update does not exist for any safety-critical system.

So, to summarize: yes, researchers have identified non-critical systems that could be hacked (as the passenger entertainment devices), but so far nobody has demonstrated the feasibility of hacking a critical system


Advance ratio formula for drone propeller in vertical climb According to this wikipedia article. There are two expressions for advance ratio:

For propellers:
$$J = {V_\infty \over nD} \tag{1}$$
For helicopters:

$$\mu = {V_\infty \over \Omega r} \tag{2}$$

We know that: $\Omega = 2\pi n$, so by substitution in (2):

$$\mu = {V_\infty \over {2\pi nr}}= {V_\infty \over \pi n D} = {J \over \pi}$$

So $\mu \neq J$

My question:
In case of a helicopter in a vertical climb (no forward velocity) with constant velocity $\vec v = (0, 0, u_z)$, which expression should I use for advance ratio? $J$ or $\mu$?

I could not find equation (2) in my copy of J. Gordon Leishman' Principles of Helicopter Aerodynamics. Some relevant info on momentum analysis in forward flight can be found here on page 63.

Advance ratio as a useful measure of blade twist is less meaningful in helicopters, due to the much greater variety in the direction of the velocity vector. It makes more sense to optimise blade twist for forward flight than it is to optimise for vertical flight, a state with much higher fuel consumption which helicopters do not particularly like.

If you would like to use the advance ratio for helicopters as stated in the wiki article, it makes more sense to use the helicopter one. There may be a direct parallel between the states you describe in your question, but for the helicopter case it is not the design state while for the fixed wing it is.

Whether either is relevant to a propellor drone depends on the design of the drone, whether the propellor is shrouded etc. But for a drone, free velocity would usually not be close to perpendicular to the propellor plane, just like in a helicopter.


Why haven't the remaining TRSAs been converted to Class C airspace? The communication and radar equipment is already in place to provide radar services. ATC staff them. It seems like the biggest investment to get them converted to class C is charting. Why haven't they been converted in the 25 years since the airspace reclassification?

Class C airspace is established by a rulemaking procedure (i.e., Notice of Proposed Rulemaking, comments, publication, etc.).  TRSAs are not established by rulemaking action.

From FAA JO 7210.3Z- Facility Operations and Administration -para. 11-1-3 & 4

Class C:

  Class  C  airspace  must  be  officially  designated  by
  airspace action in 14 CFR Part 71 and is established
  solely to define the airspace in which all aircraft are
  subject  to  operating  rules  and  equipment  requirements specified in 14 CFR Part 91.[emphasis is mine]

TRSA:

  TRSAs
  are not officially designated
  by airspace
  action and were established solely to define an area
  within which a separation service will be provided.
  [empasis is mine]

Within a TRSA the (vfr) pilot is not required to participate.  However, within Class C airspace a (vfr) pilot is required to participate.

It is not as simple as a charting issue:

If a Radar Facility Manager wants to change a TRSA and make it Class C airspace a staff study must be done and proper justification has to be documented and approved. See Class C Airspace Processing (staff study protocol) FAA Order 7400.2L - Procedures for Handling Airspace Matters - para: 16-3-1

Since the implementation of Regulatory Class C airspace requires more ATC involvement to provide the service (Class C service) and requires mandatory participation on the part of vfr pilots, the process can be a significant challenge that has to be clearly needed for the area in question and fully justified with consideration of public comments, etc., and a variety of other procedural steps to comply with rulemaking procedures.

In short, unless the Facility Manager (for that area) has determined that a higher level of air traffic control  is necessary for safety/service, etc., and then provides justification and considers comments from the public (who may not want the additional restrictions of Class C), changing a TRSA into Class C airspace won't happen.


Why does the B-2 have a smaller payload than other bombers of comparable size? B-2 Spirit1

Payload
40,000 pounds (18,144 kilograms)
Wingspan
172 feet (52.12 meters)
Weight
160,000 pounds (72,575 kilograms)
Maximum takeoff weight
336,500 pounds (152,634 kilograms)
Range
approximately 6,000 nautical miles (9,600 kilometers)

B-52 Stratofortress2

Payload
70,000 pounds (31,500 kilograms)
Wingspan
185 feet (56.4 meters)
Weight
Approximately 185,000 pounds (83,250 kilograms)
Maximum takeoff weight
488,000 pounds (219,600 kilograms)
Range
8,800 miles (7,652 nautical miles)

B-1B Lancer3,4

Payload
75,000 pounds (34,019 kilograms)
Wingspan
137 feet (41.8 meters) extended forward, 79 feet (24.1 meters) swept aft
Weight
approximately 190,000 pounds (86,183 kilograms)
Maximum Takeoff Weight
477,000 pounds (216,634 kilograms)
Range
5,100 nmi (5,900 mi; 9,400 km)

The US Air Force web-site says:

  The revolutionary blending of low-observable technologies with high aerodynamic efficiency and large payload gives the B-2 important advantages over existing bombers.

But in comparison with the other bombers, including much older B-52, it appears to be less aerodynamically efficient and carries less payload.

Why does the B-2 carry a much smaller payload than the other bombers of comparable size? Does it signify, that B-2 has worse aerodynamic characteristics? If yes - what are causes of it?

The simple answer is that it is optimized for being low observable/stealthy, and long range, rather than for maximum payload.

When you design an aircraft, you make a variety of trade offs depending upon which features are most important for that design.  The design of the B-2, which reaches back into the 1980's1, put a premium on the ability to avoid being detected by radar.  This informed the shape.  The USAF's strategic purpose for that aircraft was to enable it to reach globally, so that it could be launched form the continental US or a forward deployed base.  This put a premium on range/fuel capacity.

@Durandal points to another detail/difference: The B52 and B1 both can carry ordnance on external hard points (and this is a must to get up to the cited payloads). The B2 has no such hard points because it would nullify its stealth capability. There is simply no room to put more munitions within the bomb bay.

With the advent of precision weapons, which were in parallel development to the B-2, the raw tonnage wasn't as important as getting to the target area, and getting out "without being seen."

Because aircraft are all constrained somewhat by the cube/square law in terms of size, the trade offs/compromises on that model arrived at a payload that fit in with the rest of the requirements.

Both the B-52 and B-1 were build under a different design paradigm, under different requirements combinations, and were "pre-stealth" bombers: the B-52 was meant to get the most range and raw payload together, while the B-1 combined speed (supersonic, back when speed was perceived to be at a premium) and payload foremost.  While both have since benefitted from the use of precision munitions, the original designs (all nuclear weapons carriage considered) had to account for the problem of non-precision munitions shortcomings with accuracy.  (Experiences in WW II informed this problem, as did experience in Viet Nam).  You need to drop a pattern of "x many bombs" to have a high probability of hitting a given target.

1 Insofar as the "flying wing" idea for the shape of the B-2, the initial attempts in that direction go back to the 1930's and the Ho_229 as so @paracetamol kindly reminds us.  Also, and FWIW, it is related to a DARPA  project that goes back to the 1970's (stealth / radar resistant in general) that was compromised publicly by President Carter during a press conference.  Actually, those paying attention had heard of it from Kelly Johnson: In fact, that existence was far from secret. On July 23, 1976, readers of Aerospace Daily were informed that Clarence L. (Kelly) Johnson, "the nation's premier aircraft designer" and architect of the U-2 and SR-71 spy planes, was bulding "a new 12,000-pound, one-man Stealth aircraft" at the Lockheed plant in Burbank, Calif. The magazine claimed that the $90 million program, sponsored by the Defense Advanced Research Projects Agency, was designed "to reduce aircraft visibility -- optical, acoustic, and radar signatures -- through new technology."


Could the cabin crew open the lavatory door from outside when someone locked the door from the inside? On a recent flight a passenger locked himself in the lavatory for almost the entire duration of the flight. It was only when the flight was in the final leg of descent that he could be persuaded to come out.
In similar situations, can the cabin crew open the door from the outside if it is locked from the inside?

Apparently yes. It has been mentioned in a number of places. One of the methods given is pretty simple:

Step 1: Approach locked lavatory
Step 2: Lift "LAVATORY" sign
Step 3: Slide the knob into the unlocked position

Thats all to it, though they may vary with the aircraft.

As @RalphJ points out in the comments, it should go without saying that unless you are cabin crew, you should not be doing this.


What does the number of white bars in runway's threshold mean? At the beginning of each runway there are some white bars.

Does number of bars in threshold mean anything?

For runways built, refurbished or repainted after January 2008, the number of bars in the Threshold Markings indicates the width of the runway, as is described in Section 3 of the AIM. Older runways may still use an outdated scheme.

Runway threshold markings come in two configurations. They either consist of eight longitudinal stripes of uniform dimensions disposed symmetrically about the runway centerline, as shown in FIG 2-3-1, or the number of stripes is related to the runway width as indicated in TBL 2-3-2. A threshold marking helps identify the beginning of the runway that is available for landing. In some instances the landing threshold may be relocated or displaced.

(source: faa.gov)

Runway Width   | Number of Stripes
==================================
60 feet (18 m) | 4
75 feet (23 m) | 6
100 feet (30 m)| 8
150 feet (45 m)| 12
200 feet (60 m)| 16

With regard to how to tell the difference between Configuration A and B, Advisory AC 150/5340-1J goes into significantly more detail. It states that

The threshold markings may have either of the characteristics in (1) or (2) below, but after January 1, 2008, only those characteristics in (2) will be acceptable.

The details:

Configuration A. The runway threshold marking consists of eight longitudinal stripes of uniform dimensions spaced symmetrically about the runway centerline as shown in Figure 1. The stripes are 150 feet (45 m) long and 12 feet (3.6 m) wide and spaced 3 feet (1 m) apart, except for the center space, which is 16 feet (4.8 m). For runways less than 150 feet (45 m) in width, the length of the markings is not changed, but the width of the markings, spaces between markings and distance of markings from the runway edge are changed proportionally. For runways greater than 150 feet (45m) in width, the width of the markings and spaces between the markings may be increased proportionally or additional stripes may be added to both sides.
The rule for Configuration A markings requires scaling the width of the stripes and their spacings (and the outboard spacings from the runway edges) proportionally, keeping the length fixed. For a runway 150 feet wide the Configuration A stripes are 12 ft wide with 3 ft spacings (and an 8 ft spacing from the inboard stripe to the centreline, leaving 10 ft between the outboard and runway edge). The Configuration B stripes are given a fixed width of 5.75 ft with spacings of 5.75 ft also. If a Configuration A scheme were used on a narrow runway such that the stripes were equal to the width of the Configuration B stripes, the runway width would need to be about 72 feet (12 ft stripe width for a 150 ft runway width scaled to 5.75 ft for 71.875 ft). For a 72 ft wide runway bearing the Configuration A scheme the spacing between stripes would be reduced to slightly less than 1.5 ft. The difference between the schemes therefore ought to be apparent.

and

Configuration B. For this configuration, the number of stripes required is related to the runway width as indicated in Table 2. The stripes are 150 feet (45 m) long and 5.75 feet (1.75 m) wide and spaced 5.75 feet (1.75 m) apart except the center space is 11.5 feet (3.5 m) as shown in Figure 1. The outboard edges of the outboard stripes extend laterally to within 10 feet (3 m) of the edge of a runway or to a distance of 92 feet (27 m) on either side of a runway centerline, whichever results in the smaller lateral distance.

This is further borne out by a May 2004 advisory (CERTALERT 04-04) which states:

The purpose of this CERTALERT is to remind Airport Operators, Airport Certification Safety Inspectors, and Program Managers that paragraph 9(d) states the threshold markings may have either the characteristics in (1) Configuration A or (2) Configuration B, but after January 1, 2008, only those characteristics in (2) Configuration B will be acceptable.


What do we hear, on the ground, from a helicopter in flight? Last week I heard a helicopter approaching from a distance.

The sound it made was a very distinct and deep wop wop wop at a remarkably slow two beats per second, more or less.

As it came closer, the sound suddenly changed, to something more like six beats/second, with a quite different and more familiar chattering.

What were we hearing from the ground? What do the two different sounds represent?

Rotor noise is relatively complicated, and is very highly dependent on the design of that particular aircraft. Here are at least a few components to consider:

Ultimately what you're "hearing" is of course pressure waves in the air, which in a helicopter are almost entirely caused by the rotors passing through said air[1].  If you're head-on and a fair distance away, you're primarily hearing the pressure wave that's generated as the rotor passes the point where it directly points at you, because that's where you get the strongest component of pressure "pointed" in your direction.

As the aircraft moves, your orientation to the sound profile changes: you get both the doppler effect which changes the pitch, but you also get a very different sound profile because the pressure waves from the main rotor are interacting with both the body of the aircraft and more importantly the pressure waves from the tail rotor in different ways.  I don't remember the exact percentage, but a very large part of the sound generated by helicopters is the interaction of the main and tail rotors - this is a main reason that you see a lot of modern helicopters with a "shrouded" tail rotor. If you're truly head-on, it's reasonable to assume that you're getting very little of the interference with the tail rotor, and as you get more side-on with the aircraft you get far more interference noise.

[1] You also, of course, get noise from the engine-- but that's usually drowned out unless you're quite close, OR if you happen to be sitting near a chopper with the rotor at zero-lift... in this case the noise from the rotor is actually pretty low and you can hear the engines and the tail rotor a lot more clearly...


Where do the compressed gasses of a charged engine goes? Good day to you here.
I'm working on a modified version of 2-stroke engine. My plan is to use a supercharger for the scavenging process, instead of the conventional Crank case scavenging technique, thereby excluding the Crank case from the entire scavenging process.

But I have a question that's bothering me, In a charged (super or turbo) four stroke engine, after the the inlet port has been closed by the inlet valve, where does the subsequently compressed gasses go? Do they find their way back through the air filter? Do they remain in the inlet manifold until the inlet port opens again? Does this part of the engine cycle has any negative effect on the overall performance of the engine?

Note: Do excuse my grammatical blunders.

As long as the rpm is kept up, the charge coming out of the compressor has quite a bit of inertial mass and is more or less flowing continuously even though there is a valve downstream opening and closing.  There will be a pressure and velocity fluctuation near the valve as the charge just upstream is admitted to the cylinder, then cut off.  But because the opening and closing is happening so fast, these fluctuations taper off up stream.

This is one reason for having long intake runners on a 4 stroke; to take advantage of the inertial mass of the long cylinder of air in the intake duct.  On a non-supercharged engine, this helps with the preliminary filling the cylinder during the intake stroke because the piston doesn't actually have to "suck" initially.  As the intake valve opens, air comes rushing in pushed along by the inertial mass of all the air back up the intake duct, like a crowd of school kids jamming up in the hallway and piling out the door when it's opened at the end of school.  The ones closest to the door don't have to be pulled out; they are pushed out by their mates behind.

Anyway, the main issue is managing the intake charge and its inertial effects, and the increasing difficulty in doing this at lower speeds or idling.  I would expect you would have to do a lot of experimentation with compressor gearing/speeds and intake runner length trying to get an engine to run smoothly across the full operating range.

Your project sounds like a variation of a 2 stroke diesel, which doesn't use crankcase pressure to drive air into the cylinder like a spark ignition 2 stoke, and therefore requires a supercharger or turbocharger compressor to push the charge along in the absence of a 4 stroke's intake stroke to pull air in.  Possibly looking into 2 stroke diesels would help.

I'd also look into using an electrically driven supercharger in your design which would make it easy to experiment with different speeds and could really improve operation over the speed range by using a computer to manage it.


How does a PFD handle unphysically abrupt changes in the parameters it's displaying? This question is about human factors requirements in the design of software components displaying instruments in a primary flight display. (It's not about how to implement the software.)

Let's take an airspeed indicator (ASI) as an example. In a "steam gauge" ASI, the needles add some inertia to the instrument, limiting the maximum rate of change it can display. This is OK, because the actual indicated airspeed (IAS) has a much smaller maximum rate of change in the real world.

In a "moving tape" ASI on a primary flight display (PFD), a software component receives updates of IAS and changes the display appropriately. The human readability of the instrument depends on the changes being gradual, so the numbers gradually "wind around" like a physical instrument: if the numbers abruptly jump, it's hard for the pilot to notice and understand what has happened.

In normal circumstances, an abrupt jump in IAS (or altitude, heading, or other important flight parameters) cannot occur, because there are physical limits on the rate of change. But the software component just receives a stream of values, and it's possible that an error elsewhere in the system could cause an abrupt jump.

Is there typically a requirement on this software component to smooth the instrument display or handle this possible situation? I can imagine some possible ways of dealing it:

The display component has a limit set on rate of change (guided by the physical limitations and the HF limit on how fast a change can be displayed understandably), and it has to reject out-of-range changes (presumably tied to an EFIS/ECAM message). When the changes are in range, the display is updated immediately without interpolation.
The display component has to interpolate between received values by animating, so that even abrupt changes appear to "wind" the instrument. This preserves the readability of the instrument but will introduce some latency in the displayed values.
The display component has no special requirement, and protections elsewhere in the system ensure that it never has to deal with unphysically abrupt changes.

I understand that per-component requirements are unlikely to be published by any vendor, so I'm happy to take an unsourced answer if it's backed by personal experience. Even information from an experienced glass-cockpit pilot who has seen this error state first-hand would be appreciated.

Generally, PFD will smoothen the indication for most of the indicated data.

I don't know any 'legal' requirements for it, but as you mention, basic ergonomics require it.

I have first hand experience with Garmin G1000, so I'll try to explain its PFD behaviour as an example. (It's a bit hard to capture and post a video).

Most (if not all) 'graphical' indications are filtered with the rate (characteristic frequency) consistent with the expected rate of change of the relevant parameter: pitch/roll quickly (but still noticeably, about 0.3 s), airspeed moderately, engine temperature slowly (3-5 s). Digital only indications (say, battery voltage) are also filtered, and in addition their precision is limited such that the updates didn't happen too frequently (e.g. round 0.5 V).

The filter seems to be a second-order low-pass in most cases. For some parameters, notably the indicated airspeed, it is underdamped, which means the indication overshoots slightly for abrupt changes, and generally tends to oscillate to and fro for normal changes. This provides faster response while still being smooth.

An abrupt, unrealistic change of parameters per se doesn't cause a fault for PFD. It's just filtered as usual. However, significantly out-of-range values will fail the indication, but only temporarily, until sensible values resume. Generally, it's the job of the peripheral computers (ADC, AHRS, etc.), as well as of the integration unit (GIA), to detect faults and convey them in special messages. PFD is, after all, just a display.


What Airfix model is this? I built this Airfix kit when I was younger, and don't know what it is. I'd love to know!

It is a relatively early Mirage IIIc. You can tell it from other common modifications by the longer rear fuselage, which accommodates the longer afterburner of the older Snecma Atar 9B engine.

The exhaust nozzle on your model is closed indicating military power. On most photos you will see it wide open (it has two buckets on a hinge, and a horizontal gap is clearly visible).
I know all this because not too long ago I built a similar model, but with a smaller 1:100 scale.


May an uncertificated pilot log non-PIC flight time for future certification? Let’s suppose I as a PIC take a friend up flying with me and this friend does not have a pilots license.  Now let’s suppose I teach him how to control the airplane and let him fly for a while.  I even go on a cross country flight and let him fly most of it.

Looking at the regulations regarding aeronautical experience for a private certificate, CFR 61.109, it states that the pilot must log 40 hours total flight time, 20 hours of instruction and 10 solo.  CFR 61.51 outlines documenting aeronautical experience and has caveats for the type of flight time but nothing for this type of situation however, 61.109 does not stipulate that all of the flight time come from solo or instruction.

So here is the question.  May an uncertificated pilot log non-PIC flight time and use it towards a certificate when another pilot lets him fly the plane as the sole manipulator of the controls?

Your friend can't log any time because he isn't licensed and qualified to fly the aircraft and assuming that you aren't a CFI then he isn't receiving training either. He's just a passenger, although if he wants to record the time for his own purposes that's fine, it just doesn't count for anything as far as the FAA's concerned.

First, 14 CFR 1.1 says that flight time is time acting as a pilot, not just time in an aircraft:

  Flight time means:

  (1) Pilot time that commences when an aircraft moves under its own
  power for the purpose of flight and ends when the aircraft comes to
  rest after landing;

So your friend needs to log time as a pilot. Obviously without a certificate there's no way to log PIC or SIC time, so that leaves training time. The regulations for that are in 14 CFR 61.51 (my emphasis).

  (h) Logging training time. (1) A person may log training time when
  that person receives training from an authorized instructor in an
  aircraft, flight simulator, or flight training device.


Can countries introduce new aviation policies unilaterally? Let's say some country intends to introduce a new aviation policy that conflicts with ICAO regulations, like only aircraft certified and approved by our government can fly in our airspace. Can they do that unilaterally? Has it ever happened?

For instance, Russia may declare a country as enemy country and it may use its equipment (e.g reconnaissance aircraft) to spy on this enemy country. In this case enemy country may start defining its own policies and make sure that defense or civil aviation equipment/software are used in compliance with these new policies.

Aircrafts need to be certified to operate under FAA/European/Russian... regulations in terms of safety, noise, etc.
For instance, in Europe EASA is the authority "for the airworthiness and environmental certification of all aeronautical products[..]".

Sometimes countries actually want to introduce new policies.
One of the most famous was in 1971, when "The US, India, and Malaysia all ruled out Concorde supersonic flights over the noise concern[..]" as reported here on Wikipedia.

Another one about aircraft noise was in 1999, when "The EU's proposed noise ordinances effectively prevented the use of hush-kit outfitted aircraft in Europe[..]".

So every country already has its own regulation.


How can pilots fly inside a cloud? I heard that sometime an aircraft fly inside a cloud, and I'm wondering how that works - how clearly can the pilot see while inside the cloud?
What if a cloud is "too large"? (Is there a maximum size of cloud a pilot can fly through?)

When aircraft fly inside clouds, they fly under "instrument rules". It doesn't matter whether the visibility is reduced (at night) or totally blocked (in a thick cloud), this mode of flying simply assumes the crew has no external visual reference, they fly solely using indications given by on-board instruments.
The following short video shows a situation frequently encountered, the crew doesn't see anything outside prior to being so close to the ground, they are nearly landed.

Landing without visibility, source: YouTube.
After the problem of replacing external references has been solved, the next most important issue is to safely stay away from other aircraft. To prevent collisions, pilots are supported by air traffic control (ATC) from the ground. ATC determines aircraft location and altitude by relying on an on-board transponder. ATC issues appropriate information and instructions for pilots in order to maintain aircraft separated.
Should ATC fail to separate aircraft, commercial aircraft are equipped with a safety net: In last resort, close aircraft, transponder-equipped, are detected and avoided by an on-board collision avoidance system. While this system is efficient when there are only 2 or 3 aircraft involved, the escape maneuver must be done quickly and can be therefore sharp enough for a passenger not belted to be injured. This doesn't work if the other aircraft isn't equipped of a transponder, but all commercial aircraft carry such equipment by regulation.
All large airliners we know fly under instrument rules, regardless of the weather, or the time of day. However for a few runways, landing can be done  by a circling maneuver (or circle-to-land maneuver) in which the crew approaches the runway using an instrumental guidance which is interrupted before landing (usually because the guidance is designed for another runway), leaving the crew under visual rules until touchdown (such maneuvers are known to be more hazardous).
For the sake of completeness, a special kind of visual flight, VFR Over The Top, may be allowed over the cloud layer, during the upper part of the flight, where the horizon and other aircraft can be seen.

1. Technical aspects of instrument flying
It's technically possible to fly inside clouds, fog, snow, at night, etc, but this type of flight is regulated, it requires technical elements both in the aircraft and on the ground, and mandatory additional training for the pilot.
Good sense, and regulation, require the pilot to be able, at any time, to:

a/ Maintain an aircraft safe attitude (flight conditions preservation),
b/ Avoid obstacles and other aircraft (collision prevention),
c/ Find their way to a landing aerodrome (navigation).
d/ Know where they are (position awareness),

Flying without visibility basically means knowing how to carry out these tasks without looking outside the cockpit.
A: Maintain a safe attitude
One of the main references a pilot needs is the horizon. When the horizon is invisible, An artificial horizon reproduces the horizontal plane using a gyroscope. This instrument indicates whether the aircraft is pitched or rolled.
Regarding altitude and speed, the same instruments are used both for visual and instrument flying: Barometric altimeter and airspeed indicator.

Main instruments, traditional presentation. Source: Aircraft Spruce
Image above (left-to-right, top-to-bottom):

speed, attitude (artificial horizon), altitude,
turn indicator, heading, vertical speed

Same instruments on the electronic primary flight display of a A330. Source
Being aware of the aircraft attitude without external visual clues is not natural and more difficult than usually expected. There was a famous study (180-degree turn experiment, Bryan, Stonecipher, Aron) in 1954 which showed a pilot not trained to fly with instruments loses control of the aircraft in 3 minutes in average if external references are lost.
B: Collision prevention
As mentioned, a collision prevention service is provided by radio from the ground. An aircraft flying without visibility is separated by air controllers (ATC) from all other aircraft. The exact type of separation provided varies with airspace category, in particular when radar coverage is missing, e.g. when flying over oceans. For EU countries, see Classification of Airspace at SKYbrary.
Civil ATC determines the aircraft location and altitude by interrogating a transponder on-board the aircraft, from the ground. Should the aircraft transponder be not cooperative, ATC might have access to a primary radar, and perform traditional echo measurement, which is less accurate. Primary radar stations are usually operated by military.

Typical ATC room, source: Learn To Fly Here

See also What is a TRACON? for a full description of control rooms in the US.

ATC is definitely a difficult four-dimension task done using 2D displays. Mistakes are made, most of the time they are fixed in time. In the picture below, VRG231 is descending from FL370 while the facing and climbing DCA337 is through FL262. ATC evaluates they will cross safely, but overlooks the closer XCM3018 approaching from the right at FL360 (more details at SKYbrary).

Loss of separation conditions in place: VRG231 is descending. ATC takes DCA337 into account, but overlooks XCM3018, source
Additional on-board equipment can be used for actual nearby aircraft detection. Such collision avoidance system, known as (TCAS or ACAS), detects transponder-equipped aircraft, typically only within a few minutes radius by using a technique similar to ATC interrogation. In addition, TCAS can provide coordinated conflict resolution advisories to the pilots, to increase separation and prevent collision.

B737 TCAS (TA/RA positions on the transponder panel). Source

C: Navigation:
After the two first tasks of the crew (aircraft in safe flight and collision risks under control), it's time to look at how the crew can reach the destination.
Navigational radio aids are positioned at important locations on the ground, and on-board instruments are used to take benefit of them. Today they include VOR (relative bearing determination) and DME (distance determination) for navigation to, from and between airfields. NDB are still used, but their decommissioning has started around the world, they are used as long distance and non-precision VOR.
Extract from Nice airport (LFMN, France) documentation for Runway 04 departures. Note how VOR (circled in green) and NDB (magenta) are used as waypoints. Also note how NIZ VOR-DME is used as a reference for relative bearing and distance (green stars).

Source
Space radio aids, namely GNSS (US GPS, EU Galileo, Russian Glonass...) are complementing or replacing ground aids for operations (ground aids are still used and required by regulation). For example, the same departures from Nice using Precision Area Navigation (P-RNAV) taking advantage of GNSS, inertial and ground aids to obtain a precise combined position:

Waypoints are not referring to any ground aid but defined by their coordinates in the flight management system database. Same source
A manual or an automated landing can be conducted with the guidance of an ILS (instrument landing system), which is a radio lighthouse usable to follow proper direction and proper slope:

ILS principle (magenta clues displayed on the pilot panel)
As you may have noticed, contrary to a persistent belief, pilots don't rely on ATC for navigation (the exception would be when a pilot has lost all instrumental references. ATC may usually be able to provide a position if the transponder is still operational).
In busy terminal airspace, typically around large airports, ATC role is extended. First, the risk of collision being large and airports being in densely populated areas, aircraft must follow more constrained paths, ATC operators constantly monitor these paths and request corrections from pilots when necessary. Second, runways are scarce resources, arriving aircraft (and departing aircraft to a certain extent) must be sequenced (e.g. by adjusting their speed) into orderly and dense landing queues.
D: Position awareness
Current horizontal position has been determined for a long time using VOR and DME and geometry: angle-angle (aka triangulation) or angle-distance equations.
Larger aircraft have also used inertial platforms which are able to provide no only the current position, but also the heading, the ground speed and most uniquely the acceleration, the rate of rotation and the attitude (from which the angle of attack can be obtained).
Today, those technologies are complemented by GNSS which is able to provide the current position and altitude.
The inertial platforms are still used for their complete independence from any external resource, and their precision which is better than GNSS in the short time. Their big con is they drift continuously and must be reset at intervals (e.g. using GNSS data). To take advantage of everything available, sources are often mixed to provide weighted values and cross checking (add to this air sensors providing altitude and airspeed data).

B737 Fight Management Computer page showing current position according to several sensors. Source
Aircraft are also equipped with ground detection, to help prevent so-called "CFIT", controlled flight into terrain. This sensor is based on on-board radar and stored maps and display ground obstacles around. It is used for horizontal monitoring (hill, mountain) as well as vertical monitoring (ground proximity during landing). Such systems are known as EGPWS, enhanced ground proximity warning system.. They warn pilots by loud advisories, e.g. "Terrain! Terrain, pull up!".

VSD/EGPWS display on Boeing aircraft, source

2. Regulation point of view
Visibility conditions are determined to be either visual (good visibility) or instrument (insufficient visibility) and there are two sets of rules when flying (visual and instrument). Flying in instrument conditions requires by regulation to perform the flight under instrument rules.
Flying with reference to instruments only, requires:

The pilot has received the proper training,
The specific equipment is available in the aircraft, and on the ground,
ATC is provided from the ground.

VMC vs. IMC
There is a set of minimum conditions to declare that the outside environment is visible: these conditions are known as Visual Meteorological Conditions (VMC).
When VMC are not achieved, the conditions are said to be IMC, for Instrument Meteorological Conditions.
VMC criteria depends on countries and airspace, though ICAO provides international recommendations, e.g. in France, generally:

Minimum horizontal visibility 5 km (8 km above FL100).
Minimum distance to clouds: Horizontally 1.5 km, vertically 1,000 ft.

VFR vs. IFR
Any flight must be done under one of the two existing sets of rules:

Visual Flight Rules (VFR)
Instrument Flight Rules (IFR).

The rules to be followed are dictated by regulation and are directly dependent on the meteorological conditions.

In VMC, both VFR and IFR flight are allowed.

In IMC, only an IFR flight is allowed, the pilot must be qualified to perform IFR and the aircraft must be certified for IFR.

Related:

Spatial disorientation which may lead to fly upside down without knowing. Related training.


Low-wing taildraggers pictured on 2021 ASA FAR/AIM cover? There are a pair of low-wing taildraggers on the cover of the 2021 FAR/AIM published by ASA. Can anyone identify them?
I tracked down the image source here, but the description does not identify the planes:
https://www.istockphoto.com/photo/motor-aircraft-on-the-ground-gm1131409963-299576828

Zwei farbige Motorflugzeuge Sportflugzeuge stehen am Boden auf dem Rollfeld eines Flugplatzes.
Translated to English:
Two colored motorized aircraft, sport aircraft, are standing on the ground on the tarmac of an airfield
Does anyone know what they are?

They are Jodels. All wood.  The D-11 was a very popular homebuilt once upon a time (a friend owns one), along with factory production of various models in France in the '60s.  Hard to say exactly which models those are.


Specific Acrylics for fabricating windscreen I've a experimental aircraft in need of a windshield due to crazing caused by fuel and cracking caused by stress. It is made of polycarbonate/Lexan and I want to replace it with acrylic because of its susceptibility to fuel and scratching. However, as there are a jillion kinds of acrylics I need recommendations of specific brands and types.

You need cast acrylic sheet (not extruded).  If you are in North America you can get it from Aircraft Spruce https://www.aircraftspruce.com/catalog/mepages/plexiglas.php?clickkey=7342.  The cast sheet made for airplanes has UV blockers as well.

Acrylic has roughly the same tensile strength as Lexan (8-9ksi - a 1/8" sheet of acrylic or Lexan has roughly the same strength as a sheet of .032 6061 aluminum) but is more brittle and has to be formed into as close to the final shape as possible, with the minimum possible preload on the sheet and at fastener holes.

On the plus side of being brittle, although it still scratches a lot easier than glass, the surface is way harder and doesn't scratch if you look at with furrowed brow like Lexan does (although it can come with hard coatings - which tends to get removed by polishing), and is immune to fuel to boot.

Lexan is popular because it can take a lot of pre-stress and you can force it into moderate curves and clamp fasteners on it without it cracking.  But acrylic is superior for the other characteristics important to airplanes.

If your homebuilt's windshield is made up of flat sheets, it's a no brainer - cast acrylic.  If it's a curved wraparound, you'll have to form the acrylic into the curve by heating it in an oven and draping it over a form.  If fuel was an unavoidable problem because of a gas cap in front, it's probably worth going to the trouble to form an acrylic windshield if you have an oven big enough to fit the sheet.  If the fuel exposure was an unlikely to repeat fluke and you need a curved windshield, it might be easier to just do another polycarbonate one that you can cold bend.


Who manufactured the 737 MAX flap track fairings? I can't seem to find the information online, would anyone of you know where / by who the flap track fairing for the B737 MAX is produced?

The fairing assemblies are made by Boeing itself. From ATS:


Why is carburetor heat use discouraged on the ground? I've been reading my private pilot books for when I start in February and Carb Heat has me stuck in a rut. I feel like I need to have a very solid understanding of this being that I live in a very humid area. The book says do not use carb heat on the ground and on taxi because it will draw unfiltered air into the engine(air from exhaust)... But what is the difference between using it in the air vs on the ground and isn't the risk of icing just as equal in the air as on the ground?

If you feel that you would need carb heat sitting on the ground, I'd recommend taxing back and waiting for conditions to improve. If you are set on going, usually doing a run-up at the runway before take-off will tell you if you have carb ice or not.

The other answer gave good reasons, sucking in some FOD (foreign object debris), but there are some other things you would want to consider...

Forgetting to push the carb heat back in before takeoff
 - Especially important when taking off from short fields, you want all the power your engine has to offer, as carb heat robs your engine of some power. If you have carb ice, applying carb heat will cause your engine to make even less power (hot air is less dense than cold air). 3/4 of the way down a 1200 foot runway is a bad time to realize the carb heat is still on, because it probably isn't on your takeoff checklist.

Carb heat is not very effective on a cold engine
 - This is a real problem when you are at idle or especially gliding, the airflow over the engine components and the exhaust just doesn't create enough heat to melt the ice in the carb (at least not very quickly). This is why you may be instructed to "clear" the engine periodically during low power operations. This involves adding power and then carb heat to help melt any ice.

That all being said, its not so much a rule as a recommendation. You'll probably find that during your flight training you'll end up leaving the carb heat on while on the ground for short periods. This happens a lot during landing operations when you are instructed to have carb heat on (my instructor taught me mid-field downwind, "Seat Belts, Gear, Fuel Selector, Carb Heat, Mixture, Prop, Power"). You'll end up leaving it on until you've cleared the runway (or set up for a touch-and-go) and are running your "after landing" checklists.


How can I determine the amount of trim drag? I fly an ASW27, which is a 15 meter glider with flaps.  I am flying with the CG at 62% aft.  I use down flaps while in a thermal and climbing; negative (up flaps) are used in cruise between thermals.  typical thermals speed is 50 to 60 kts (with ballast) and 90 to 100 kts in cruise.  This glider has a T tail and I need nose up elevator for thermal and nose down elevator for the cruise.

I notice that in cruise, the elevator is deflected down about 10 deg.  Is that deflection creating a significant amount of drag that could reduce my glide performance?  I have the ability to move the CG by dumping the ballast in the tail tank

As I mentioned in my comments. You could test this empirically with the experiment described there.  If you find the additional ballast improved the glide performance of the craft, is there an aftermarket STC kit available which installs new ballast tanks in a more optimum position for a more neutral cruise trim?

I am a little concerned with the idea of continuing to move the CG aft of its current position in order to optimize the performance at the expense of. Asking the craft less stable about the lateral axis.  No increase in performance is worth your life.


When do conditions permit doing a controlled fly-by over the runway of a commercial airport? A lot of people reading this probably saw Top Gun and remember Maverick performing a fly-by over the deck of the USS Enterprise (in spite of being explicitly ordered not to do so), or saw air shows where aerobatic pilots do all kinds of cool maneuvers for the entertainment of the people on the ground.

What I didn't know was possible is that a commercial aircraft with passengers on board would be allowed to perform such maneuver over an active civilian airport (you can find the video here). The video shows the last approach and landing of a commercial pilot before retirement, in which he's allowed to perform a fly-by over the runway of Jorge Newbery airport in Buenos Aires, Argentina. Throughout the video you can hear other pilots over the radio saluting the pilot who is about to retire, and near the end you can see the passengers applaud and airport and airline personnel on the taxi runway welcoming the aircraft. It's a pretty emotional video even for someone like me who's not related in any way to the aviation community, you should see it if you can spare a couple of minutes.

Anyway, I know that there are certain traditions involved in the last flight of a pilot before retirement but I didn't know that a flyby was one of them. In order obey the rules of this site, the main question I'm asking here is:

What would be the right circumstances where a stunt like this would be allowed?

But I would also like to know if this kind of maneuver has ever been performed on similar circumstances over airports with more traffic or using a bigger aircraft.

Essentially a flyby over the runway is nothing more than a planned and prepared go-around from a low altitude. If you say it is a stunt then it probably is not allowed under most legislations. And because of noise regulations airports aren't too happy with the manoeuvre either.
However, nobody will stop you from going around if you "forget" to put your gear down.
I have been in the cockpit on several flybys at several airports, all of them were dressed like a missed approach / go-around along the following lines:

Pilot > "Tower, Hotshot01, requesting permission for a flyby over runway XX
Tower > Negative Hotshot01, you know we can't allow that any longer due to noise restrictions. I can't prevent you from making a go around though! Cleared to land RWY XX.
Pilot > Hmm... ok, cleared to land, Hotshot01

<Hotshot 01 approaches the threshold and applies full power>

Pilot > Hotshot01, going around.
Tower > You owe me a beer now! .. <vectors back to final approach / final destination>


Why are the tails always painted, but not the fuselage, in test and delivery flights? Granted some airlines prefer to paint their own planes, but we always see planes like the one below, protective coating everywhere but the tail.

Why's that?

(Source)

Excerpt from McDonnell Douglas MD-11 by Arthur A C Steffen:

  The remaining eight aircraft were delivered bare-metal with a corrosion protection coating, except for the rudder which has to be painted prior to being installed and balanced, and was completed in the full livery in the carrier's modern paint facilities.

The above text is in reference to KLM's first batch of MD-11's.

The paint has to be applied so the manufacturer can balance the rudder after the added weight of the paint.

That extends to other control surfaces and engine cowls.

For the vertical stabilizer, the minimum requirement is the rudder, but if the airline's logo extends to the rudder, then for colors and shapes alignment the whole tail is painted by the manufacturer.

If the fin was repainted and the operator couldn't afford or didn't have time for the re-balancing, we end up with Frankenstein tails:

(Source)


How can I check that the GPS receiver is sending data to the transponder? I fly an ultralight aircraft. The GPS is a puck-type device from which the TX line runs to the mode-s transponder. The transponder does not readily show if it is receiving position data. The data is NMEA RMC sentences only, serial 4800 baud 1 message / second.

Is there any way to ascertain as part of the preflight check that the GPS is alive and sending some data (how correct is besides the point, for now)? I'm thinking along the lines of connecting an LED in parallel on the TX line which will flash to show data traffic if I press a test switch. Any ideas? Thx

Your puck (GlobalSat BR355) runs on 5v and the UART line idles high (it is pulled high when there is no traffic).   The first thing you need to do is find the power lines that go to the gps puck -- connect wires to these lines (5v and gnd) and run them to the spot where you want the button/led.   Then make this circuit:

The value for R1 should be 150 ohms (which will yield under 20ma of current through the LED, assuming your led has a voltage drop of 2.1v (which the ones in the link I provided do have))

Here is a link to a transistor that will work for Q1:

https://www.digikey.com/product-detail/en/central-semiconductor-corp/2N4403/2N4403CS-ND/4806893

Here is a resistor that will work for R1:

https://www.digikey.com/product-detail/en/stackpole-electronics-inc/CF14JT150R/CF14JT150RCT-ND/1830603

And here is a link to a selection of LEDs you can use (all with voltage drop of 2.1v; Any of these should work; just choose a color and form factor that works for your application):

https://www.digikey.com/products/en/optoelectronics/led-indication-discrete/105?k=led&k=&pkeyword=led&pv16=2&FV=1140050%2C4fc0015%2C1f140000%2Cffe00069%2C87c001d&mnonly=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

Here is a link to a selection of pushbuttons that should work -- just choose a form factor you like (look at the datasheet for the ones with 4 pins -- these are just two pairs of pins (each pair is connected) for mounting ease -- two pins can be harder to mount on a circuit board):

https://www.digikey.com/products/en/switches/pushbutton-switches/199?k=pushbutton&k=&pkeyword=pushbutton&pv130=7&FV=1140050%2C2dc0017%2C3ac000e%2C1f140000%2Cffe000c7&mnonly=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

I personally recommend you use something like this for the button:

https://www.digikey.com/product-detail/en/e-switch/KS-01Q-01/EG4791-ND/2116270

For this button here is a picture and a schematic (as you can see, the pins on either side of the flat side of the button are connected:

And something like this for the led:

https://www.digikey.com/product-detail/en/cree-inc/C503B-RAN-CZ0C0AA1/C503B-RAN-CZ0C0AA1-ND/6561758

Just wire these components up according to the picture and solder them together -- I'll leave how to mount the switch and the LED up to you but make sure once you are done you cover all the exposed wire with glue and/or electrical tape and/or liquid electrical tape so they don't accidentally short out.   Also make sure no exposed wires within the circuit are touching where they shouldn't touch (especially make sure you separate the pins of the transistor because if they accidentally touch the circuit will not work and you may damage your gps receiver -- long story short be careful in your wiring and make sure nothing is touching that shouldn't.


Will optimising the weight distribution of a commercial flight save fuel? Since the centre of gravity must lay in a certain location, I'm wondering if it would save fuel if it lays exactly in the right spot?

Let's assume that you have an A320 and weight distribution is fine (within tolerance). If ballast is shifted until COG is located at the perfect location, would you save fuel? How much would that be?

For precisely this reason the A310-300 had a fuel tank in the horizontal tail. However, the pilots I spoke with (Pan Am) did not understand the purpose and insisted that the tank is empty all the time. The A330 and A340 also have a tail fuel tank, and here its fuel level is automatically controlled.

A330 tank arrangement (picture source). Note the trim tank in the horizontal tail.

Shifting the c.g. a little back reduces drag slightly (less than 2% reduction in fuel consumption, depending on initial c.g. position) but also static stability. This is no problem when the FCS adds enough stability, but in case of a system failure you should make sure that the rear tank can be emptied soon. Hand flying an aircraft with relaxed static stability is tiring.

The A350 did away with this feature because it was felt that the added complexity would outweigh the benefits.


If the engine of a helicopter fails, is it possible to land safely? Imagine the rotor of a helicopter is not spinning anymore, can you control the aircraft to land safely?

You're asking two different questions, actually.

If the engines fails in a helicopter, the rotor will usually rotate and the pilot can land the helicopter by autorotation. The record is from an altitude of more than 12km by Jean Boulet when he descended via autorotation as the engine flamed out and couldn't be restarted.
If the rotor seizes for some reason in a helicopter, there is no lift produced and it will fall down. For tilt rotors like V-22, if the conditions permit (if it is in aircraft mode), the aircraft can be glided like normal fixed wing aircraft.


Can a turbofan maintain torque when spinning fast? I assume turbofan fan rpm could be increased only when:

Using most modern jet engines (Airbus A380 and the Boeing B747-800)
Using a magnetic gearbox which can handle more torque dor the same weight
Fan and compressor blades are reinforced
Design muffles and silences the fan sonic boom
Engine is designed to prevent a flame out.

Assuming the problems above are solved, and one was able to redesign the fan and compressor blades to be efficient at 10 times their current rpm, without changing the power rating:

Would the engine have enough torque and power to spin the fan at cruise altitude?
What would be the effect on thrust?

An initial thought is that at 10X the RPM, it is likely that the blades would be well into Mach numbers, which would have a negative effect on power requirements (that is substantially more torque in particular) to spin the fan, and more importantly the fan would not be effective at those speeds.  There would likely be blade damage as well from the loading.

However this is a rather hypothetical question, where if an engine were developed to do this, there would be other trades to be made in the design of an engine. Changing just one part of a system such as a jet engine, usually does not favorably alter the overall performance.


How do pilots board the B-1B Lancer? I've noticed that there isn't any type of hatch/plug door near the canopy of the B-1B Lancer. How do pilots enter and exit the aircraft?

The crew of Rockwell B-1 Lancer (4 in total) enter or exit the cockpit from the underside, using a ladder. It can be seen in this video.

This picture shows the ladder (the one on the right):

Image Source

On the top of the ladder, there is a door, which looks like this:

Image Source


Do aircraft manufacturers produce their own black boxes? Do the manufacturers who build airplanes use their own "black boxes" in the planes, or are there companies whose sole purpose is to develop black boxes?

For example, in 2010 in the Airblue Flight 202 incident, the black box had to be sent to France for data recovery:

  He stated that the box would be examined by "foreign experts" in
  Germany or France as Pakistan does not possess the equipment to decode
  the flight recorders. He also stated that the process of extracting
  information may take six months to a year. The Pakistani
  authorities decided to send the CVR and FDR to the Bureau d'Enquêtes
  et d'Analyses pour la Sécurité de l'Aviation Civile (BEA) in
  France.

It is not clear who developed that black box. Was it the same company that manufactured the airplane?

Also, can the buying airline use their own black box or their own security protocols for data encryption or encoding, to avoid having to send the black box out for analysis?

There's seldom a reason for manufacturers to design and build their own black boxes. It's expensive to run a production line to design, build a test a few. It's just cheaper to get an agreement with a company to make them for you. The second photo below shows a popular recurring model from Honeywell, which appears to have been used on the A330, B737 and B777.

Opening the black box can be a sensitive operation, especially if there's the fear that the chips might have been damaged. It's better to send it to somebody who's done it before rather than trying to master it on the first attempt, especially if you don't have the resources. Airplanes accidents don't happen very often.

Note that the case you're referring to, the Aircraft also appears to have been built by Airbus in Hamburg, and hence the German Accident Board automatically gets involved as well, much like how the NTSB gets involved in all Boeing crashes.

(source: naij.com)

A smashed up flight data recorder.

(source: dailymail.co.uk)

A photo from the NTSB with the Asiana flight 214 recorders

Another reason for this is if there might be political motives behind the crash, it's preferred to send it to a third party for analysis which is less susceptible to bias or interference.

If I gather correctly, data on the flight data recorder won't be encrypted at all- it will be fed out as serial data, but you will need the devices and software to understand this information, and if the outside connection is broken, you'll need to work your way to the chips themselves.

(source: com.au)

Photo showing apparently how black box are 'read'.

Furthermore, sending it to the company is not always a good idea- they might have motives to change the truth, especially if it was caused by dodgy maintenance or bad training, nor to the manufacturer, if it was production error. The accident investigation board is the best people for this matter.


Can I use actual IMC time for the requirements in 61.109(a)(3)? I needed extra instrument time for my VFR checkride but it was cloudy for my lesson. My CFII and I turned it into an introduction to IFR lesson and we flew 0.3 actual and 0.3 simulated (with the hood) and did 1 ILS approach in IMC.

61.109(a)(3) says that the following instrument training is required:

  3 hours of flight training in a single-engine airplane on the control and maneuvering of an airplane solely by reference to
  instruments, including straight and level flight, constant airspeed
  climbs and descents, turns to a heading, recovery from unusual flight
  attitudes, radio communications, and the use of navigation
  systems/facilities and radar services appropriate to instrument
  flight;

Is it correct to assume that I can use the IMC time for this?

Sure can.  FAR 61.109 makes no distinction between flight in hard IMC and simulated in an aircraft using a view limiting device.


How does ATC deal with apparent compass errors when giving vectors? Pilots should strive to fly precisely, but we sometimes reach task saturation.

When ATC gives a heading, receives the correct readback, but observes a 10- to 15-degree difference between the actual and intended tracks, does the specialist incorporate this difference into future vectors? Do approach and traffic separation vectors generally have a healthy margins of error?

How does apparent compass deviation or directional gyro precession factor into vectors that ATC issues?

This question is a partial duplicate of this one and this one.

  When ATC gives a heading, receives the correct readback, but observes a 10- to 15-degree difference between the actual and intended tracks, does the specialist incorporate this difference into future vectors?

Sometimes. The controller issues headings but observes ground track.  If the wind is causing drift, the controller will compensate for it when she provides vectors.  Sometimes, if an aircraft is suitably equipped, a controller will ask for a wind report in order to better judge the winds at altitude.

  Do approach and traffic separation vectors generally have a healthy margins of error?

Yep.  See here.

  How does apparent compass deviation or directional gyro precession factor into vectors that ATC issues?

It's up to the pilot, not the controller, to correct for compass deviation (since only the pilot can see the compass correction card inside the aircraft) and gyro precession (since only the pilot can turn the little knob to reset the gyro).


What factors come into play when reducing the total noise generated by a helicopter? I simply cannot understand how a helicopter can be made quieter. What are the things that would considerably affect the noise signature of a helicopter ?

I'm no expert but the RAH-66 Comanche can help answer your question.

It was a stealth attack helicopter prototype.

The Wikipedia page lists two main design elements:

A five bladed rotor, the more blades you have, the slower they'll turn, so less noise. Of course they are harder to balance, so it's not cheap.
Canted blades, kind of like winglets. They reduce the blade-tip vortices. The intricate shaping also is expensive, as the blades were 100% composite.

Sound proofing the engine compartment and muffling the exhaust can be expected as well. But that's added weight.