to whom are PAN PAN PAN calls addressed?

A PAN call is like a MAYDAY call in that you are broadcasting to whomever may hear it.  However, if you broadcast a PAN call on an active ATC frequency, ATC will naturally respond to it and it's sufficient to just state PANPAN-PANPAN-PANPAN and your registration and any other information and ATC will answer, and everybody else will know to stay off the frequency momentarily.

You can broadcast a PAN call on any other frequency like a unicom, or 121.5, and whomever is listening in will likely respond.  I was once downed in the bush in a seaplane by engine trouble, becoming stuck on a remote lake, and couldn't raise anybody on the normal unicom channel even if I heard other seaplanes passing in the distance.  I saw a contrail above, and knowing airliners monitor 121.5 over sparsely settled areas, I broadcast a PAN call with my registration on 121.5. To my surprise the airliner heard me and answered.  I was able to get him to contact base on the Unicom frequency and let them know what lake I was on before he was out of range of my radio's transmitter, and was rescued with my two fisherman passengers later that day.  The only other choice was to set off the ELT and hope an airliner or SAR aircraft heard it (this was pre-SARSAT), which would have meant spending the night there at least.


You can still use some small bags with flour or other soft material inside.

For the wing load test, the bending moment is more critical than the torsion. Therefore, the flour-bags could work fine.

If you want to add torsion and a more precise loading, you can build some sectional fixtures that transfer point loads to the wing.


Structural rating of aircraft to withstand storm induced structural stresses

All aircraft can in theory be overstressed by either a vertical gust (flying into an updraft) that is severe enough or a maneuvering input (pulling on the stick) that is hard enough.  Both increase angle of attack suddenly increasing the lift force, and bending, on the wings.  Increase the lift force enough to exceed the bending strength of the wing's spar, and that's all she wrote.

The protection from this comes from the fact that if you are below a certain speed, you will exceed the stalling AOA before the bending load exceeds the limit, and the stall will partially unload the wing before it gets over stressed.

So there are two speeds you have to observe; Maneuvering Speed and (on larger airplanes) Turbulent Air Penetration Speed (also called Rough Air Speed).   Maneuvering Speed is the speed below which you'll stall before over stressing the wings if you just yank the control column back as hard as you can to full travel.  Instead of pulling the wings off you'll just snap roll (which is in fact, with rudder added, how you do a snap roll).

Turbulent Air Penetration Speed is the speed below which an extreme vertical gust will take the wing past its stall AOA before the gust can exceed the wing's bending strength.

On transport airplanes, if you know you will, or expect there is a significant risk that you will, enter turbulence, you slow the airplane to Turbulent Air Penetration Speed as protection against over stress.  You would do this if there are thunderstorms in the area (you still give storm cells a wide berth in any case), or there are reports of Clear Air Turbulence, or you are crossing the boundary of a jet stream at altitude, where CAT is typically found and you are being cautious.

On the CRJ700, the Turbulent Air Penetration Speed is actually in the lower end of the normal cruise range, 280kt/.75 Mach, so it's not a major inconvenience.  Maneuvering speed is well below that.

Light aircraft like the Piper Saratoga in the video don't usually publish a Turbulent Air Penetration Speed, just a Maneuvering Speed (134kt for the Saratoga), and the pilot should have slowed to that to avoid being over stressed from turbulence.

Problem is, light airplanes bumbling into thunderstorms usually end up in spiral dives where limiting the speed becomes impossible and they typically come out the bottom of the storm in pieces from over speed and/or over stress, and it comes down to staying out of them at all costs.


Can single engine planes glide from a falling position?

It's remotely possible, assuming you can find a suitable UFO :-) If you drop an object from an aircraft it starts falling with the same airspeed that the aircraft has, until drag or other factors slow it down. If you've ever seen a flour bombing competition (or just watched some WW2 movies or documentaries) you may have noticed that you drop bombs before you reach the target, not when you arrive directly over it.

So if the UFO is moving forward at an airspeed greater than the Stinson's stalling airspeed (65mph) - let's say 80mph - then the Stinson will fall into the air at an airspeed high enough to generate lift immediately and it will fly. If you already have the engine running and throttle up as soon as you fall out of the UFO, you will generate thrust and maintain the flight.

In reality - if there is such a thing when a UFO is involved - the Stinson is almost certain to lose some altitude and the wake turbulence from the much larger UFO will have a significant (and potentially very dangerous) effect if the Stinson can't stay ahead of it.


Does the FAA always require a neuropsychological assessment battery for applicants with a history of ADD?

If you have ever in your life been diagnosed with any mental health condition, such as ADD/ADHD, then the FAA presumes you to be mentally defective until proven otherwise to their satisfaction, by their own experts at your expense. They do not care what your personal doctor says, or what other pilots say.
You will need to get evaluations from a HIMS Psychiatrist and/or HIMS Neuropsychologist, which will likely take you months to arrange since there are only a few in the entire country. Then you will need a HIMS AME to process the paperwork and send it to OKC, which will spend a few months reviewing it to make sure the file is complete. Then your file will be sent to DC, where it will sit on the Federal Air Surgeon’s desk for several more months before he reviews your file. If all goes well, he will issue a Special Issuance medical, conditional on renewing the above evaluations every 6 or 12 months until he is eventually convinced you are mentally stable enough for a regular medical certificate. That may take up to 10 years, depending on your exact condition.
If your AME is not a HIMS AME, they will have no idea how this process works or what paperwork is required, so switch now and save yourself months of wasted time and money.


How much fuel does an A380 hold and where?

The total capacity of fuel tanks of Airbus A380 is 320000 liters.

The fuel tanks in Airbus A380 are shown in this image.

Image Source

The capacities of different tanks are1 (in liters):

Tail tank: 23,698
Inner tanks: 90,600
Mid tanks: 72,000
Feed tank 2 and 3: 28,130 each
Feed tank 1 and 4: 26,974 each
Outer tanks: 9,524 each

1 The only place I found this information is in the book Airbus A380: Superjumbo of the 21st Century. Luckily, it is on Google books. This excerpt from the book about the relevant information says:

  The horizontal stabilizer runs through section 19 and includes an integral fuel tank between ribs 8 left and right. The fuel level in the tail tank, which can take up to 23,698 liters, is adjustable in flight for trimming purposes. Overall, the hard-line A380-800 fuel-tank capacity is 315,292 liters, most of which is contained in two inner tanks with more than 90,600 liters. Two other mid-tanks hold about 72,000 liters between them, with inner engine 2 and 3 feed tanks containing 28,130 liters each. The outer engine 1 and 4 feed tanks each hold 26,974 liters, while the two outer tanks each hold 9,524 liters.


What effect does the Space Shuttle have on the Shuttle Carrier 747

@fooot beat me to it in the comments but the linked podcast answers all your questions

The shuttle effected lots of factors of flight, in quick summary (from the info in the podcast) the whole assembly was:

...aerodynamics not neutral as is answered in this question
...Speed limited due to the braces that held the shuttle on
...VFR only due to the fact that impacting rain could cause water build up issues in the heat shield tiles
...Altitude limited
...Bank angle limited
...Quite short range by default
...Required the orbiter to be empty (although hypergolic fuels were left onboard. All payloads had to be removed if the orbiter was returning something.
...Required rib re-enforcements where the braces were mounted
...Was quite noisy due to the brackets used to hold the orbiter on


What is the best way to retrieve (and transmit) location (GPS) of plane in real time?

There are a few consumer-facing easy-to-obtain devices that you could use for this, although they don't quite transmit in real-time (they'll transmit updates down to every 2 minutes).  Spot and inReach are aimed at more casual users, and Spidertracks offers real-time tracking that might be considered targeting more of the commercial or "prosumer" market, but they still transmit updates every 1-2 minutes.

They all work in a similar fashion: rather than some kind of ground-based radar, they utilize a combination of GPS to calculate your location and use the Iridium Satellite communications network to transmit it (so it doesn't rely on cellular signals and has global coverage), they transmit on an interval you decide to a website that your interested party could monitor.  This is the key difference from other answers that use an app on a device: even if the app is linked to a real-time tracking service like Map my Tracks, your phone or tablet will still be relying on the cellular network (which you're technically not supposed to be using in flight), and even if it does work, it could be intermittent. These devices link into the Iridium Satellite network for global coverage.

The three devices are: Spot Satellite Communicator and the DeLorme (now owned by Garmin) inReach, and Spidertracks.

This isn't a free service, there is a monthly fee for using the devices.

Spot is around USD$150

inReach is around USD$350

Spidertracks start at USD$1000

In July 2016 ($USD)

inReach: Allows tracking updates every 10+ minutes ($15/month) or the 99/month package allows for updates every 2+ minutes.

Spot: 50/year allows 5, 10, 15... minute tracking update intervals or $150/year: 2.5+ minute tracking updates.

Spidertracks has various plans, basically you pay by reporting point the range is $0.05 - $0.13 per reporting point.

DeLorme inReach:

Spot Satellite Personal Tracker:

Spidertracks

Example of the web interface from Spidertracks for real-time tracking


Do pilots of commercial aircraft have ready access to a map or data showing nearest airports in case of a need to make an emergency landing?

Since you asked about commercial aircraft, I will answer for a modern airliner: The Boeing 777. The details will differ between aircraft models, but the general functionality should be available in every modern airliner.
With a modern airliner equipped with an EFIS (Electronic Flight Instrument System), there is no need to carry paper maps with possible diversion airports any more. Selecting a suitable alternate and navigating there can be done with the FMC (Flight Management Computer).
On the 777, the FMC has a page with alternate airports that are selected automatically from the navigation database, but can also be overridden by an uplink (where the airline dispatch sends suitable alternate airports to the aircraft) or manually (e.g. required for ETOPS flights with selected ETOPS alternates). This page looks something like this:

(Boeing 777 FCOMv2 11.43.21 - Flight Management, Navigation - FMC Descent and Approach)
The list of four airports is shown in 1 and the estimated time of arrival (ETA) as well as the fuel at the diversion airport is shown in 4 and 5 respectively. 2 allows a request of alternate airports from the airlines dispatch via ACARS. In order to divert to one of these airports, you select the respective line from 1 and the press DIVERT NOW (9). This will set up the flight plan with a direct line towards the selected airport.

Alternate Airport Diversions
ALTN page 1/2 data aids the flight crew in finding a suitable alternate airport.
The page displays up to four airports in ETA sequence. Each airport on the list has an XXXX ALTN page with more data. [...]
Three alternate airport uplinks can be received. ALTN LIST page 1/2 can get an uplink for the entire page or just the ALTN INHIB line. ALTN LIST page 2/2 can receive an uplink of alternate airport names.

(Boeing 777 FCOMv2 11.43.20 - Flight Management, Navigation - FMC Descent and Approach)
These four diversion airports can also be displayed on the Navigation Display (ND):

(Boeing 777 FCOMv2 10.10.35 - Flight Instruments, Displays - Controls and Indicators)
This is particularly helpful if adverse weather is in the area (e.g. thunderstorms) because the weather radar would depict areas with large amounts of precipitation on the ND as well. Should an alternate diversion airport be out of display range, it will be shown like this:

Displays the FMC or pilot selected primary alternate airport. Displays up to four alternate airports when the EFIS control panel ARPT map switch is selected on.
Offscale airports (those beyond 640NM with 640 scale selected), directional arrow relative to the airplane position or PLAN center point and distance (distance remove in PLAN).

(Boeing 777 FCOMv2 10.40.20 - Flight Instruments, Displays - Navigation Displays)
All of this allows a fast decision for an alternate diversion airport. Nonetheless, communication with ATC (Air Traffic Control) is of course essential in an emergency and ATC will assist in finding a suitable diversion airport if necessary. I don't quite agree with

I'm thinking that seconds could mean the difference between life and death [...].

If you only have seconds to make such a decision, it means you are at very low altitude, meaning either just after takeoff from your departure airport or already very close to your destination airport. In this case, the usual choice in case of an emergency is to return to the departure airport or continue to the destination. There are exceptions of course, like e.g. a takeoff alternate:

A take-off alternate aerodrome should be specified in the operational flight plan if either the meteorological conditions at the departure aerodrome are below the applicable landing minima or in case it should not be possible to return to the departure aerodrome for some other reason.

(SKYbrary - Alternate Aerodrome)
In this case the takeoff alternate would however be chosen before even departing, so no quick decision is necessary.


Is there a dedicated emergency frequency?

If a pilot is already speaking to ATC (or monitoring a frequency) they should continue to use that frequency for any emergency or abnormal situation.
If they are not currently receiving ATC services or on an ATC frequency, attempt to use 121.5. Many ATC providers and enroute airliners monitor this frequency and can relay or provide assistance.
The FAA's AIM (6-3-1) describes emergency use of 121.5 in the United States:

h. Although the frequency in use or other frequencies assigned by ATC are preferable, the following emergency frequencies can be used for distress or urgency communications, if necessary or desirable:

1. 121.5 MHz and 243.0 MHz. Both have a range generally limited to line of sight. 121.5 MHz is guarded by direction finding stations and some military and civil aircraft. 243.0 MHz is guarded by military aircraft. Both 121.5 MHz and 243.0 MHz are guarded by military towers, most civil towers, FSSs, and radar facilities. Normally ARTCC emergency frequency capability does not extend to radar coverage limits. [emphasis mine] If an ARTCC does not respond when called on 121.5 MHz or 243.0 MHz, call the nearest tower or FSS.


What is the wingtip station number on a Boeing 747?

For the wing tip station , just divide the wingspan by two and multiply by 12.  The stations are in inches.  For a 747 with a 195' 8" wing span, the tip station is 195.66 divided by 2, times 12 = 1173.96, so the tip will be Station 1174.

For X and Z you need to know where the datum point is longitudinally and for the X axis, and what the waterline is that defines the Z axis.  Waterline is often the cabin floor.  X datum on a jet is often the forward pressure bulkhead surface.


Can TS-1 fuel be used in an aircraft that takes Jet A?

The answer is maybe.  You would have to check the Fuel System Limitations in the Operating Limitations in the AFM of the aircraft in question to find a table or list of the approved fuel types, which may or may not include TS-1, and if it doesn't you're kind of stuck.

For example, if I look up the allowable fuel grades for the CRJ700, it includes several worldwide standards (American, British, Chinese, NATO etc), and a fuel type is listed as "RT" under CIS (Russia's official name - Commonwealth of Independent States I believe).  But there is no listing for TS-1, so unless RT and TS-1 are the same thing and you have official documentation confirming that, it can't be used in the RJ (I'm retired and the pilot reference handbook I'm using is quite old and out of date so perhaps TS-1 is listed in current ones, but in any case you get the drift).

You can't use wide cut fuels in the CF-34 family (gasolene-kerosene) but if TS-1 is equivalent to Jet A there is a good chance it's approved for a particular airplane, but don't be surprised if there is a temperature limitation or other restriction.


Can airplanes benefit from this "roughness" on bird wings?

It may seem counterintuitive, but by introducing a small amount of turbulence, this interrupts the slower boundary layer which is directly in contact with the wing, thereby delaying local airflow separation and aerodynamic stall. Essentially, at the expense of a small amount of parasitic drag, the stall performance and control effectiveness of the wing can be improved.
Aircraft add small fins called Vortex Generators to achieve this effect on otherwise smooth wings, flaps, ailerons, rudders, and elevators.

Here is a link to check out:
https://en.m.wikipedia.org/wiki/Vortex_generator


Are there experimental aircraft regulations in Germany?

Yes, there are. Everything is regulated in Germany.

Your regular experimental aircraft would have to follow JAR 23 and the LBA has transferred the supervision and certification of experimental aircraft to the Oskar Ursinus Vereinigung (OUV). Before you begin work on your experimental, be sure to contact them and talk to an OUV assessor. This assessor will follow the progress of your work and will regularly check if all work is done properly. You need to prove that you have a heated workshop and document your work sufficiently (like keep samples of every resin mixture that was used for building composite parts). This assessor will also help with contact to experts if you got stuck or with the insane amounts of paperwork, which - this being Germany - often seem baffling and pointless.

You do not need a full certification but at least a load test to 100% design load. The aircraft will get a vorläufige Verkehrszulassung (VVZ; provisional airworthiness certificate) which needs to be renewed regularly. Also, operation of that experimental will be restricted to overflight of sparsely populated areas. But others have succeeded before, so good luck!


(planespotters.net)

The flag is an easy giveaway. It's one of two* British Aerospace Avro RJ85's operated by Dubai Royal Air Wing.

* Probably it's the A6-RJ2 (but the registration is blurry).


What are some good resources on Jet Design?

That one depends on a lot of things.  Real jet engine design is going to require an understanding of advanced physics, computational fluid dynamics, thermodynamics, heat transfer, and metallurgy.  It will also require college level engineering coursework as well as at least calculus and in some cases partial differential equations on order to properly design such an artifact.

Not to be deterred, amateur jet engine builders have constructed self sustaining gas turbines using old turbochargers and a custom built isobaric combustion chamber as this YouTube video shows.  Both the reactive thrust and/or mechanical power one can get out of such a device is limited.

There are some existing plans available on the market for building small jet engines as this Instructables shows.

RC Aircraft modellers can also buy small scale turbine engines for around \$3,000-$5,000, depending on manufacturer, type, thrust output, etc.

Designing a proper jet engine from scratch is going to be much more difficult, though it is possible. It will be expensive and time consuming, but if you really want to learn the art of building turbine engines, it's possible.  I would advise waiting until college and pursuing a degree in aerospace engineering. The major aero schools (e.g. Michigan, Purdue, MIT, CalTech, etc. all have extra curricular clubs as well as design and testing facilities and equipment for this sort of stuff and as I said before you will need higher level engineering and mathematics education in order to do it right.  That's not to say this is impossible; the Rocket Boys, a pack of coal miner's sons whom the film October Sky was based upon, were designing Di Laval nozzles using differential equations in high school, so if you really want to learn, it's always possible, though not always easy.

If you do want to start down that path and want a challenge, I'd recommend The Design of High Efficiency Turbomachinery and Gas Turbines by Wilson and Korakianitis.  I'd also recommend primers on thermodynamics and heat transfer as well.

You might attempt the earlier turbocharger projects first or disassemble an RC jet engine to get a much better familiarization first, then attempt the engineering of an engine from scratch.

In addition, seek out other jet engine builders and talk with them.  They will be a wealth of information for you at the beginning of the project.

You might also seek out professors at a good aerospace engineering program somewhere and ask them what direction they would recommend you to begin such a project.  Remember: Old people find nothing more flattering than a youngster who will sit patiently and listen to what they do for a living; employ that to your advantage.

A long shot but it might work as well - get involved with Linkedin and look for profiles of engineers who are employed at places like UTC/Pratt & Whitney, GE Aircraft Engines, Rolls Royce, Eurojet, etc.  You might just find someone there who designs jet engine parts for a living and can be a good resource.

Also, as with any kind of engineering or programming, start simple and work up to complex.  Your not just building an artifact, you're building a database of knowledge of how to build such an artifact as well, which can be built upon in increasingly more complex designs.

Oh, and one final caution: gas turbines belch large, noisy quantities of high temperature, high pressure gas and operate at very high temps, creating the possibility of serious injury, explosions and/or fire hazards.  Approach the design and testing process with caution and take appropriate safety measures i.e. don't test this thing in your parent's basement, etc.


How much data is stored in the flight data recorder per hour in a typical flight of an A380?

I don't have the numbers for the A380 but have some for the Dreamliner. On a typical flight a Dreamliner will record about a half a terabyte of data:

  This level of operational insight will involve generating large amounts of data from each 787 aircraft, he explained. “We can get upwards of half a terabyte of data from a single flight from all of the different devices which are internet connected," Bulman said.

source

Depending on the airline this data is stored/processed/compressed/uploaded to HQ.

The flight data recorder or "Black Box" stores far less parameters as only 88 are required by the FAA:

  (1) Time;
  (2) Pressure altitude;
  (3) Indicated airspeed;
  (4) Heading--primary flight crew reference (if selectable, record discrete, true or magnetic);
  (5) Normal acceleration (Vertical);
  (6) Pitch attitude;
  (7) Roll attitude;
  (8) Manual radio transmitter keying, or CVR/DFDR synchronization reference;
  (9) Thrust/power of each engine--primary flight crew reference;
  (10) Autopilot engagement status;
  (11) Longitudinal acceleration;
  (12) Pitch control input;
  (13) Lateral control input;
  (14) Rudder pedal input;
  (15) Primary pitch control surface position;
  (16) Primary lateral control surface position;
  (17) Primary yaw control surface position;
  (18) Lateral acceleration;
  (19) Pitch trim surface position
  (20) Trailing edge flap or cockpit flap control selection
  (21) Leading edge flap or cockpit flap control selection
  (22) Each Thrust reverser position (or equivalent for propeller airplane);
  (23) Ground spoiler position or speed brake selection
  (24) Outside or total air temperature;
  (25) Automatic Flight Control System (AFCS) modes and engagement status, including
  autothrottle;
  (26) Radio altitude;
  (27) Localizer deviation, MLS Azimuth;
  (28) Glideslope deviation, MLS Elevation;
  (29) Marker beacon passage;
  (30) Master warning;
  (31) Air/ground sensor (primary airplane system reference nose or main gear);
  (32) Angle of attack ;
  (33) Hydraulic pressure low (each system);
  (34) Ground speed ;
  (35) Ground proximity warning system;
  (36) Landing gear position or landing gear cockpit control selection;
  (37) Drift angle
  (38) Wind speed and direction ;
  (39) Latitude and longitude
  (40) Stick shaker/pusher
  (41) Windshear
  (42) Throttle/power lever position;
  (43) Additional engine parameters
  (44) Traffic alert and collision avoidance system;
  (45) DME 1 and 2 distances;
  (46) Nav 1 and 2 selected frequency;
  (47) Selected barometric setting
  (48) Selected altitude ;
  (49) Selected speed
  (50) Selected mach
  (51) Selected vertical speed
  (52) Selected heading
  (53) Selected flight path
  (54) Selected decision height
  (55) EFIS display format;
  (56) Multi-function/engine/alerts display format;
  (57) Thrust command
  (58) Thrust target
  (59) Fuel quantity in CG trim tank
  (60) Primary Navigation System Reference;
  (61) Icing
  (62) Engine warning each engine vibration
  (63) Engine warning each engine over temp.
  (64) Engine warning each engine oil pressure low
  (65) Engine warning each engine over speed
  (66) Yaw trim surface position;
  (67) Roll trim surface position;
  (68) Brake pressure (selected system);
  (69) Brake pedal application (left and right);
  (70) Yaw of sideslip angle;
  (71) Engine bleed valve position
  (72) De-icing or anti-icing system selection
  (73) Computed center of gravity
  (74) AC electrical bus status;
  (75) DC electrical bus status;
  (76) APU bleed valve position
  (77) Hydraulic pressure (each system);
  (78) Loss of cabin pressure;
  (79) Computer failure;
  (80) Heads-up display
  (81) Para-visual display
  (82) Cockpit trim control input position-pitch;
  (83) Cockpit trim control input position--roll;
  (84) Cockpit trim control input position--yaw;
  (85) Trailing edge flap and cockpit flap control position;
  (86) Leading edge flap and cockpit flap control position;
  (87) Ground spoiler position and speed brake selection; and
  (88) All cockpit flight control input forces (control wheel, control column, rudder pedal)

Source

Some modern airliners such as the A330neo store up to 1200 parameters, making it easier to traceback what caused a crash.

Exact numbers are difficult to provide as the data from a black box is considered to be highly confidential.


What is the purpose of a small wing near the cockpit on the front of some planes?

That would be a canard you see on the airplane.

An aircraft designer may adopt the canard configuration to reduce the main wing loading, to better control the main wing airflow, or to increase the aircraft’s maneuverability, especially at high angles of attack or during a stall

Canard foreplanes, whether used in a canard or three-surface configuration, have important consequences on the aircraft’s longitudinal equilibrium, static and dynamic stability characteristics.

Many pioneers initially followed the Wrights' lead. For example, the Santos-Dumont 14-bis aeroplane of 1906 had no "tail", but a box kite-like set of control surfaces in the front, pivoting on a universal joint on the fuselage's extreme nose, making it capable of incorporating both yaw and pitch control.

I hope this has helped.


Does the 2020 ADS-B -Out requirement apply to aircraft with only a wind-driven generator (electrical system)?

Part 91 is mostly clear on the subject:

  §91.225   Automatic Dependent Surveillance-Broadcast (ADS-B) Out
  equipment and use.

  (a) After January 1, 2020, and unless otherwise authorized by ATC, no
  person may operate an aircraft in Class A airspace unless the aircraft
  has equipment installed that—

More detail, that describes 1090 MHz ADS-B out equipment...

  (b) After January 1, 2020, and unless otherwise authorized by ATC, no
  person may operate an aircraft below 18,000 feet MSL and in airspace
  described in paragraph (d) of this section unless the aircraft has
  equipment installed that—

More detail describing 1090 MHz or UAT ADS-B out...

  (c) Operators with equipment installed with an approved deviation
  under §21.618 of this chapter also are in compliance with this
  section.

If you have this deviation, you're good.

  (d) After January 1, 2020, and unless otherwise authorized by ATC, no
  person may operate an aircraft in the following airspace unless the
  aircraft has equipment installed that meets the requirements in
  paragraph (b) of this section:

  (1) Class B and Class C airspace areas;

  (2) Except as provided for in paragraph (e) of this section, within 30
  nautical miles of an airport listed in appendix D, section 1 to this
  part from the surface upward to 10,000 feet MSL;

  (3) Above the ceiling and within the lateral boundaries of a Class B
  or Class C airspace area designated for an airport upward to 10,000
  feet MSL;

  (4) Except as provided in paragraph (e) of this section, Class E
  airspace within the 48 contiguous states and the District of Columbia
  at and above 10,000 feet MSL, excluding the airspace at and below
  2,500 feet above the surface; and

  (5) Class E airspace at and above 3,000 feet MSL over the Gulf of
  Mexico from the coastline of the United States out to 12 nautical
  miles.

That's all airspace where ADS-B is required. A summary is shown in the following graphic:

Source: FAA

  (e) The requirements of paragraph (b) of this section do not apply to
  any aircraft that was not originally certificated with an electrical
  system, or that has not subsequently been certified with such a system
  installed, including balloons and gliders. These aircraft may conduct
  operations without ADS-B Out in the airspace specified in paragraphs
  (d)(2) and (d)(4) of this section. Operations authorized by this
  section must be conducted—

That specifies which aircraft have an exception (with following detail on specifically what airspace they can operate in.) It has, however caused confusion as the wording is very similar to Part 91.215(b)(3) which specifies "an engine-driven electrical system" as opposed to "an electrical system".

Subsequently the FAA has published a Legal interpretation that clarifies the intent was not to create a more stringent requirement for ADS-B Out than for transponders; specifically from the interpretation:

  As such, we have concluded that the same aircraft excluded from the
  transponder requirement are excluded from the ADS-B Out equipage.
  Accordingly, an aircraft that subsequently has been installed with
  batteries or an electric starter would not be required to equip for
  ADS-B Out.

So it appears that your J3 is exempt and would remain so unless you installed an engine-driven electrical system.


How do pilots travel from remote private airports after landing?

You do whatever you can.

Sometimes you call a taxi/Uber, sometimes you walk, sometimes you pack a small folding bicycle into your plane, and sometimes you borrow the airport car.

Many small airports in the US have a car (often a retired police car) available for itinerant pilots to borrow.  It's usually a scary rusted out pile of junk, but it works.  If you borrow it you're expected to return it promptly & with a full tank of gas.

It's wise to make arrangements for ground transportation before you arrive - there's no guarantee that any particular option (except walking) is going to be convenient and available.


What is the cost of the engine Boeing 747 Model 400?

The actual prices paid for an engine are likely to not be released publicly. However, list prices are advertised, and other sources may help give an idea of the price range for such engines. The 747-400 model has three engine options available: PW 4056, GE CF6, and RR RB211. These engines are also used on other aircraft, which will help in finding the prices.

The CF6 engine has a list price of about $11 million (from an A330 order in 2009, higher thrust version; \$12.2 million in 2015 USD1).

The PW4056 engine has a price of $5.8 million (from a 1994 report; \$9.3 million in 2015 USD).

I haven't found good pricing for the RB211. An older, lower thrust version was priced at £340,000 in 1971 (\$4.8 million in 2015 USD2), or you could buy one right now for $35,000 (the seller hopes it can be put on display, mentioning "very high end art displays" but also "top dollar in scrap").

The list price for a 747-400 was about \$240 million, which means that 4 engines at a list price of \$10 million each would be about %17 of the cost of the plane.

1Inflation calculator
2exchange rate


Can you fly the plane manually without disengaging autopilot?

The autopilot will always disengage when you try to override the controls. Manual control has priority over autopilot.
For the Boeing 737, the control mode changes to CWS (Control wheel Steering), which is an autopilot mode but follows control column inputs. So if you manually set it on 12 degrees pitch down (please do not do this in real life) then the autopilot will keep it there.


How much humidity is being maintained in cabin and cockpit of B787?

These sources say that most airliners maintain a humidity of 4-7%, while the 787 maintains 10-15%. Of course these values can vary with conditions, and other sources put them lower or higher.

The cabin and cockpit will not have very different air qualities. While some cockpits may humidify the cockpit air slightly, the cockpit tends to have a greater amount of circulation, leading to drier air than the rest of the cabin.


Who performs repossessions of airplanes?

Yes there are a couple of reality TV shows that have been done on repos.  There are companies who specialize in the business, and the pilots have to be type rated where appropriate.  They have to be legal to fly the airplane.
It takes a special kind of risk taker pilot to do that kind of work, in view of the risks of getting into confrontations with irate owners, and flying airplanes that may or may not be airworthy.  The companies are usually hired by the holder of the chattel mortgage on the aircraft; the lender in other words (and who is, ultimately, the owner).  Banks and leasing companies generally, and even government foreign aid financing organizations from time to time.
Yes the scenarios presented on the tv shows are semi-fictional BS,  with dopey staged chase scenes, but even dialing the drama back closer to reality, it's not a job for the faint of heart.


Was the introduction of the A320 flight control system controversial?

Summary

No. The aspects that are talked about now are not the ones talked about then.

My (hazy) recollection is of concerns that the A320 lacked a system of cables and pulleys of the sort used by the Wright brothers. Perhaps pilots of the time had more focused concerns but I don't recall them making the front pages of newspapers.

In the 1980s there was discussion of Airbus flight control systems but the discussion focused on factors that were not involved in the most notable A320 crashes in the late '80s and early 90's.

Several Airbus accidents seem to be at least partly the result of pilots lack of familiarity with sophisticated aircraft systems in general rather than with features that are not found in other aircraft.

The Airbus control system

The main innovations by Airbus were the application to civil airliners of designs that had previously only been used on other types of aircraft.

Fly by wire. No mechanical cables, pulleys and associated friction.
Sidesticks. To provide clearer view of displays and greater pilot comfort.
Flight envelope protection. To prevent excessive inputs stalling or damaging the airframe.

Transfer of control

Airbus spent some time comparing and investigating support for transfer of control between pilots, including in emergency situations. They investigated pilot preferences for several approaches to this. They revisited this aspect over the years and it has become a point of focus since the AF447 report. However it doesn't seem to have been a particular point of controversy in 1987. Perhaps few people in the 1980s fully realized the extent to which pilots can operate independently and antagonistically in severe emergencies and the degree to which teamwork and communication disappears.

  There were multiple severe accidents briefly after the entry into service of the A320

You mean these:

26 June 1988, Air France 296. Pilots flew aircraft into trees during unrehearsed demonstration flight at unfamiliar aerodrome after mistaking trees for grass on approach.
14 February 1990 India Air 605. Idle/open descent mode engaged and pilots failed to act as aircraft descended into terrain near airport.
20 January 1992 Air Inter 148. Aircraft flown into terrain after autopilot incorrectly put into vertical speed mode and entered numbers appropriate for flight-angle mode. Air Inter had chosen not to equip aircraft with ground proximity warning system.

The total number of hull-loss accidents for the 320 doesn't seem high compared to other aircraft, but it's hard to compare the numbers if you don't take into account fleet size, cycles flown etc.

  the A320 seems to have a very aggressive manipulation of the aircraft controls

I'm not sure what you mean by "aggressive manipulation" but that seems an extreme view. The Airbus systems are a progressive development of existing trends. The accidents were largely the result of pilots setting inappropriate modes in systems like the autopilot. The accidents apparently didn't arise because of, for example, the way the control sticks operate.

  Was there ever any questioning of the Airbus augmented control prior to the introduction to service?

By "augmented control" I guess you mean features like the flight envelope protection that prevents pilot inputs from overloading the airframe. That doesn't seem to have been controversial.

The only controversy was over two items that had been used in military aircraft but not in commercial passenger aircraft

fly by wire
sidesticks

These don't seem to have been a large factor in the specific accidents mentioned above.

Further reading:

Indian AIr 605 - A320 Special Final Conditions - FAA
Pilots in the loop?
Electrical Flight Controls
Fly by Wire
AF447


Can computer imposed inputs be overridden on the Boeing 737-MAX?

The new 737 MAX has a more advanced pitch control system called maneuvering characteristics augmentation system (MCAS), which automatically adjusts the stabilator trim in case of high thrust and high angle of attack (AOA). This makes it very hard to overcome the down force with elevator input alone (pulling up).

In case of a wrong trim adjustment (e.g. due to an erroneous AOA sensor), the pilots have to adjust the trim manually and maybe even turn off the stab trim via the cutout switches in the center pedestal (shown below). This was apparently not conveyed properly in the MAX differences training and the FAA has since issued an Emergency Airworthiness Directive.

737 NG:

(image source: flaps2approach.com)

737 MAX:

(image source: feitoffake.wordpress.com)

So compared to an Airbus, the Boeing pilots can still have all manual control, but they have to use manual pitch trim.


What turn rates are expected by ATC when given expedited turn instructions?

The air traffic controller expects you to 1) start your turn immediately and 2) turn as quickly as can safely be done. We do not have all the facts, and do not know exactly what sort of turn you are capable of doing. Using a phrase such as "expedite turn" or "turn immediately" basically means - I've screwed up, you're in danger, watch out and get out of the way. It is then up to you as pilot in command to avoid a collision, by flying your aircraft and knowing its limitations.

When ATC separation has been lost, you should respond promptly to any instructions issued with the purpose of re-establishing separation. We will also, as far as practical, issue traffic information, and expect you to look out the window and take any avoiding action you find appropriate to prevent a collision.

Finally, as a side note, if you have a TCAS, please remember that a TCAS RA takes precedence over any instruction issued by ATC.


Could passengers realize a possible emergency?

One of the survivors (a passenger) of Air Florida Flight 90 was a Private Pilot and

  ...Stiley, a pilot himself, said he realized that something was wrong as the plane headed down the runway. He said there was still snow and slush on the wings and he remembered wishing he could get off the plane.

source


How does the Guardian counter-MANPADS system work?

I have worked on and designed DIRCM systems.  Most of the technical specifications on these systems is classified.  Also, the U.S. is not the only country with DIRCM systems.  In particular, Israel is equipping their airliners with the C-MUSIC system.

How does this system work?
Basically, a laser at the wavelengths of the Infrared Missile seeker is directed at the incoming missile.  It is pulsed in such a way as to cause the missile to think that the hot spot that it is tracking (generally the engines) is not in the right spot for proportional steering. Without proportional steering, the missile avionics thinks that the missile will miss the target, so it corrects for this.  As it corrects, the laser signal continues to misinform the missile as to where the target is in its reticle, eventually causing the missile to "break lock" and fly off into a random direction. Before the laser can be directed at the missile though, there are several other steps, which is why you have a complete pod.
First a missile warning system needs to pick up the fact that a missile has been launched at the aircraft (generally the job of a series of IR cameras that give a lower hemispheric view of the aircraft's environment). Then the system tells the turret to turn to a specific point in space. The turret has its own IR camera that is responsible for tracking the missile, and once it has achieved this tracking, only then does the laser start to fire.

Does this successfully work in countering all types of missiles?
This is only effective against purely infrared guided missiles (mainly MANPADs and some varieties of air to air missiles, such as the AIM-9).  If the missile has any sort of radar assist, or is radar guided, a laser will do no good.  There are some classes of laser riding missiles that could potentially be confused by these type of systems, but no anti-air types of laser guided missiles are deployed.

Many IR guided missiles do try to counter these countermeasures, so the more sophisticated DIRCM systems need to be employed. IR missiles come in many different varieties of seekers and wavelengths they use, so the DIRCM system needs to have a laser on those wavelengths.  Not only that (and this is where the secret sauce comes in) each seeker operates on different frequencies of their reticles (and reticle patterns). So to truly confuse a missile, one needs what is known as a Jam Code. These are generally classified.

Can it be reused over multiple missile strike incidents?
As long as the laser is operational, the system can be used over and over again.  Some lasers have limits to how long they can fire, and how often they can fire (the Northrop Viper laser is notoriously power limited and has a horrible MTBF).  However, as long as there is power, it doesn't run out of ammo.  This is the main advantage of DIRCM systems over using infrared countermeasures such as flares, which are limited by the number of flares one can carry.

Are all commercial airplanes compatible with this system?
The Guardian, as well as BAE's JetEye, and Elbit's MUSIC system is designed as to be integrated onto any large airframe.  Israel has already flown it on 707 and 737 airframes, and plan to integrate it to the A-320, 747, 757, 767, and even some Embraer airfrmaes.

Is it economical for a major airline to fit all of its fleet with this system?
Not really, unless one gets shot down by a MANPAD.  The DIRCM system will cost well over a million $US (probably closer to two).  And then there is the aerodynamic penalty of hauling a 350-500lbs pod on your belly.  The concept Elbit is employing is to install aircraft with a B-kit (an interface plate and the necessary wiring).  Then the airline can buy a limited number of A-kits, and install them only on the aircraft that are going to an area that may be dangerous. Notionally, this operation can be done in an hour.

As to the danger, all I can say is that over 500,000 MANPADS have been manufactured, and many thousands are in the hands of people that wouldn't mind causing a "problem" for anyone they can inconvenience. Thankfully, the training required is a bit more than firing an AK-47, so most attempts have been unsuccessful.


Are VOR airways being replaced by RNAV routes as VORs are decommissioned?

Short answer: there seems to be no general plan to replace airways with Q and T routes. The FAA originally proposed replacing them, but the final rule doesn't include it.

You can review the source rulemaking documents in the Federal Register and it looks like the idea of replacing (or retaining) airways seems to have been discarded, possibly in response to comments.
The initial notice suggests that the idea was indeed to replace the airways:

Existing airways, routes, and procedures eventually would be replaced
by RNAV Q (high) and T (low) Routes, and RNAV STARs and DPs.

The proposed rule got some negative feedback on the T and Q route idea from two major industry lobbies:

Comment #20: AOPA and the National Business Aviation Association (NBAA) both expressed support for direct routing and avoiding
excessive implementation of additional T and Q routes.
FAA Response: In the NextGen environment, T and Q routes increase capacity and efficiency while maintaining safety by minimizing impact
to air traffic control. T and Q routes allow controllers to safely
manage air traffic during peak periods and to ensure predictable
transitions between busy traffic areas. T and Q routes overlaid on
existing airways defined by VORs could mitigate potential impacts to
the discontinuance of VOR navigation services.

The final rule has only one mention of airways, and doesn't mention T and Q routes at all:

Retain most VORs in the Western U.S. Mountainous Area (WUSMA),
specifically those anchoring Victor airways through high elevation
terrain.

My reading of all that is that the FAA originally intended to move airways to Q and T routes, but dropped the idea after receiving feedback. Or perhaps they just floated the idea to see what the reaction would be.


How do pilots manage to remember ATC instructions?

It depends.  Some instructions are really simple and with a little practice, are very easy to remember.

Runway 27 right, line-up and wait
Turn left heading 250, descend flight level 120.

Other ones will be so common, they are just remembered:

Taxi to Gate 1 via Alpha, Alpha 1, Lima 3, cross runway 24, hold short Delta.

But this is where the danger creeps in.  It is possible, and has happened, that the crew think they heard something but actually, the instruction was different today.

Taxi to Gate 1 via Alpha, Alpha 3, cross runway 24, hold short Delta.

The prudent crew will write it down.  Large aircraft have tables, or boards clipped to the control column on which to write taxi clearances, complex airways clearances and so on.

In some large aircraft, many light aircraft and in helicopters, pilots might wear a kneeboard to write instructions on.  It is a minor advantage to me that I am left handed and as a helicopter pilot, this means that my kneeboard is on my left leg where I can easily write without taking my hand off the cyclic and having it right next to the collective.

TSGT LANCE CHEUNG, USAF. - This Image was released by the United States Air Force with the ID DF-SD-01-07429

Most instructions come in the same order, every flight.  For example, here is a simplified list.  This happens every time so the crew know what's coming next, what it will likely contain, and how to respond:

Clearance for the flight plan.
Permission to start and push back.
Taxi instructions.
Departure instructions.
Take off clearance.
Hand-off from departure controller to area controller.
etc etc.

Note that any instruction which will cause the aircraft to change it's configuration or location must be repeated.  The controller then also gets to check they've got it right.  This includes things like speed, direction or altitude changes, taxi and departure instructions, frequency and squawk changes etc.

There are also some words which are only ever used at certain times, e.g. "takeoff" is only ever said when an aircraft is cleared to take off.  For example, "ready for departure" tells the controller that the aircraft is prepared to take off immediately.  The crew should not say "ready for takeoff".

You can sometimes hear a pilot receiving a long instruction, start to read it back, pause, then ask for a repeat.  Very frustrating when you are sitting there waiting to get your request in.  You just know they thought they could remember it, but didn't.  Write it down if it's anything except a simple instruction or clearance.

Here's an example of a complex one.

  SuperAir 123, cleared to Barcelona via vector departure, fly runway track, climb altitude 5000ft, after passing 2000ft turn right direct Hamm VOR, route as filed, squawk 1234, information Alpha current, startup approved

The crew might write it down like this.  Each pilot develops their own preferred shorthand:

  VD RWY TRK 5000 / 2000+ RT HMM / SQ1234 ALPHA / SU

Very brief since they know what each part is and the order they come in.

Since it contains instructions, the crew will then read it back.

  Cleared Barcelona via vector departure, runway track 5000ft, after passing 2000ft right direct Hamm, squawk 1234, Alpha on-board, startup approved. SuperAir 123.

Finally, a good reason to write stuff down is because sometimes (and we've all been there), you think you remember, then turn round to your co-pilot 2 minutes later and ask "what was that altitude?".

Here's a great example of someone who didn't have a pen and an approach to writing down clearances.


How does a lean die-out occur in a turbine engine?

With these conditions, how would this exist?

The comment by @mins appears to answer the question for modern engines, although I'm not quite sure if I'm interpreting your question as you intended, but if your intent is to find out how this happens from an operational standpoint, here's an answer for the P&W JT9D-3 through -7 engines as used on 747-100/200 aircraft. In 10 years of flying with these engines, I only had a flameout once, so it wasn't a major problem, and the -3 engines were more susceptible than the later variants.

The scenario is that you're above 35,000 and you've reached your descent point and need to reduce power from full cruise to idle. We were taught to first lower the nose to ensure that we wouldn't lose any airspeed (a little gain was okay) and then to slowly bring the thrust levers all the way back. As I remember, we typically took at least 5 seconds to get the levers back.

In other words, if you suddenly reduced power or lost airspeed, you risked a flameout.

From the pilot's standpoint, if you had a flameout, all you did was tell the flight engineer to restart it when low enough that that was possible.


Can a jet engine be restarted after a catastrophic failure?

I have no desire to dispute what a fellow retired 747 captain said, so I'm wondering if there was some miscommunication between you and the captain.
Or perhaps his definition of catastrophic is different than mine. My understanding of catastrophic would preclude any attempt to restart the engine.

During my time on the 747 I had three engine failures. One simply quit during descent, and I had the flight engineer restart it. One we shut down when the oil pressure started dropping precipitously. There was no thought of trying to restart it as that could well have trashed the engine. Neither of these two shutdowns was catastrophic.

However, on one occasion, shortly after takeoff from Lima, Peru, the #1 engine failed with a loud report, shaking the entire airplane. We were told later that the boom had been heard throughout Lima. The tower reported fire flaring out of both the front and rear of the engine for a few seconds.
After dumping fuel and landing, an inspection of the engine showed a lot of re-solidified melted metal on the inside of the tail cone.

That was a catastrophic failure.


From which rating would it be easier to transition to an Osprey? Fixed-wing or rotary-wing?

The Osprey is closer to a helicopter and if I was going to chose from a fixed wing pilot or rotary pilot to train on it I'd choose the rotary pilot.  The rotary wing physical skill set is so much more demanding than the fixed wing one.  A helicopter pilot could master fixed wing cruising flight in the Osprey far easier than a fixed wing pilot could master hovering the Osprey (you can pretty much train a monkey to fly an airplane in cruising flight - airplane physical demands are mostly when you slow down).


Why does a dual-axis autopilot not allow operation in single-axis?

It is neither a design nor regulation limitation. Best explanation I have is that manual control on one axis with the autopilot on another is a bit impractical and goes against normal piloting training techniques. For example banking left/right involves using both ailerons and rudder, but also adding a little bit of pitch up to increase the wing load in the turn.

I used to fly like this a while ago when the pitch axis of one of the autopilots was inop (failed auto-test). It was actually allowed to dispatch (and use the autopilot) but only lateral (HDG/NAV) control was available, with manual pitch. It was uncomfortable to use, counter-intuitive, and we usually just disconnected and flew the thing manually (well, maybe except cruise).


Why don't airlines place some physical separator between passengers in the planes to prevent the spread of COVID-19?

Cost. Those would be expensive, and the business is bad already. Now, you might think that just any mesh, fabric or membrane would do, but but to be effective against the sperad of viruses, nope.
Discomfort. Imagine how it would feel to be bagged up like that for hours. Again, despite the membrane being a "breathing" sort, it would still get rather hot and huimid inside that contraption very quickly.
Restrictiveness. Imagine an evacuation situation with people in those. Very dangerous, not gonna work.

Masks are very effective, cheap, and people are quite willing to use them (excluding some mentally challenged cases). The ventilation in planes is also rather safe when considering the spreading of viruses (see this ASE Q&A), especially when combined with the use of masks. Planes usually have very good filtering of recycled air, and much of the air is not even recycled.


Why are no HAPS (High Altitude Platform Station) solar planes of a biplane design?

A biplane is more robust than a monoplane per unit weight. This is because the monoplane supporting beam has to live inside the max vertical depth of the wing. With a biplane the beam can be as deep as the vertical distance between the upper and lower wing. The biplane has a worse lift to drag ratio than equiv monoplane. But drag increases dramatically with air speed. As the HAPS is only slow flying maybe the drag is acceptable. At high altitude the Reynolds number decreases, this raises stall speed. Stall speed goes down with lower wing loading (plane weight / wing area). Biplane wing loading is lower so will have a lower stall speed. Of course it's all trade offs. These are arguments for the biplane.


Are there legal limits associated with the use of the autopilot in the US?

This varies based on if you are VFR or IFR certified.

Basic currency requirements for general aviation flying under part 91 which I presume is the target of this question. The comments to the answer outline the commercial implications, can be found in

  §61.57   Recent flight experience: Pilot in command.

  (a) General experience. (1) Except as provided in paragraph (e) of
  this section, no person may act as a pilot in command of an aircraft
  carrying passengers or of an aircraft certificated for more than one
  pilot flight crewmember unless that person has made at least three
  takeoffs and three landings within the preceding 90 days, and—

  (i) The person acted as the sole manipulator of the flight controls;
  and

  (ii) The required takeoffs and landings were performed in an aircraft
  of the same category, class, and type (if a type rating is required),
  and, if the aircraft to be flown is an airplane with a tailwheel, the
  takeoffs and landings must have been made to a full stop in an
  airplane with a tailwheel.

  .... [read on for IFR and night currency]

However the FAA actually views using the auto-pilot as manipulating the controls. You can find the full legal interpretation here. But in short,

  The FAA considers a pilot's use and management of the autopilot to be
  the equivalent of manipulating the controls, just as one manages other
  flight control systems, such as trim or a yaw dampener. The autopilot
  system's sophistication does not affect a pilot's responsibility to
  manipulate and manage all control systems, including an autopilot,
  appropriately. Therefore, a pilot may log PIC flight time as the sole
  manipulator of the controls for the time in which he or she engages an
  autopilot.

With that in mind you can maintain your currency using only auto-pilot and in theory if your plane and the desired airport was equipped for auto-land (which, as far as I know, no GA planes are) you could maintain your currency without physically manipulating the yoke aside from takeoff and climb to autopilot altitude. So no there is no legal obligation to physically touch the controls to maintain currency if your plane is capable of some kind of completely programmable flight (I don't think any are currently).

There is however one notable exception to this regulation. On an IFR checkride you must fly a manual approach,

  From the ACS...

  • The applicant must accomplish at least two nonprecision approaches in simulated or actual weather conditions.

  At least one must be flown without the use of autopilot and without
  the assistance of radar vectors. The yaw damper and flight director
  are not considered parts of the autopilot for purposes of this Task.

  It claims to do everything for you within 50 feet of the ground.

This is a bit misleading. First off, most, if not all GA planes lack auto-throttle so power management is in the hands of the pilot and is fully manual in most cases. Some more modern airplanes like the DA-42 have FADEC which loops prop and throttle controls to one lever minimizing but not eliminating manual control.

There are lots of autopilots out there and function varies heavily: some only have a single axis (heading hold and adjust capability). Some have 2 axes which can hold altitude and headings and some which have the ability to follow GPS courses, fly approaches down to different minimums etc. It should be noted that some units can be set to create situations that can stall the aircraft or otherwise put it in a dangerous flight scenario, the auto in autopilot does not mean absolute protection or full automation.

  If so, can it be remotely piloted?

This is actually a completely separate question if you are asking "do I need to physically be inside the aircraft" i.e. "can I maintain currency with a drone if it's properly equipped". I don't think the FAA has fully fledged regulations on this yet. If by remote you mean by use of autopilot, see above.


What is happening with this aborted flight?

It wasn't "circling around a built up area" - it was placed into a holding pattern.

At this point we can only speculate, but holding patterns are exactly as the name implies - aeroplanes obviously can't pull over and stop like a car can, so a holding pattern is a known position where they can just fly around without causing problems for other air traffic.

It could have been to sort something out on the ground, it could have been to give the pilots time to diagnose or work on the issue, it could have been giving time for the airport to handle the unexpected arrival.

It's next to impossible to guess - the only one I'd rule out is burning fuel as they look to have only done three patterns which is nowhere near enough to burn useful quantities of fuel.


On all occasions when flaps are deployed.

Slats are a necessity when the wing uses slotted flaps or Fowler flaps for maximum lift. Those flaps cannot reach over the whole span of the wing to leave room near the wingtips for ailerons.

Once the flaps are extended, they increase the incidence of the wing along the flap span. This leaves the outer wing at a lower incidence, but in the vortex field of the inner wing. This vortex field induces a high local angle of attack over the whole wingspan, which would produce a local stall at the wingtip, where the ailerons prevent the use of slotted flaps. This stall would in most cases be asymmetric: One wing tip loses lift while the other barely manages to get along with the high angle of attack. The result is a strong rolling moment which will even increase once the aircraft starts to roll, because the local angle of attack at the down-moving wing will increase further. At this condition, the ailerons are of little help, so the roll cannot be controlled.

Angle of attack change due to movement (own work)

Now consider when flaps are used most often: Close to the ground, during take-off and landing. Then imagine what happens when the airplane rolls over one wing uncontrollably. To avoid this, slats are very helpful: They give the wing an extra stall margin by shifting the stall angle up.

While the Airbus in your picture uses slats over the whole wing, they are strictly needed only at the outer wing. Adding them ahead of the slotted flaps will increase the maximum lift and reduce the minimum speed over what is possible with flaps alone, so full-span slats (sometimes combined with Krüger flaps on the inner part of the wing) are now standard.


What are the limits of ground effect over water on an airliner plane at cruising speeds?

Ground effect only comes into play within about 1 wingspan’s height above a surface and it is largely unnoticeable until approx 1/4 to 1/10 of a wingspan above the surface.

While it is true that ground effect greatly increases the lift to drag ratio of the wings, it does not reduce parasite drag nor does it account for the fact that it is more efficient to fly at higher altitudes where the atmosphere is much thinner for greater speeds per unit of fuel consumed.  Flying low to the ground is dangerous as there is less margin for error if something goes wrong and would limits operations to day VFR conditions.

Transport airplanes have been test flown and certain flight profiles have already been determined to offer the greatest range.  These occur at altitude and on reduced power settings.

Heavy sea transports which to use wing in ground effect for lift  have been proposed in the past, but been found to be in efficient compared to existing jetliner designs. WIG craft have been used for short transport missions like island hopping, where that kind of a craft would be faster than a ship, and more efficient than a light airplane.


Which items are allowed on passenger flights but not on cargo ones?

I don't know of anything that is prohibited on a cargo flight but not on a passenger flight. There are some things that are the other way around.

On a cargo flight you must declare any dangerous goods and usually pay a DG surcharge. Certain types of DG require seperation from other types. Some need to be segregated into a container that is accessible to the crew in an emergency or has a fire-suppression equipment.

Each country has its own laws as to what is acceptible and the proper documentation required. And each company will have their own set of rules. At my employer we use the slightly more stringent IATA guidelines. This ensures compliance with each country.

The passenger airlines are also required to follow these rules. Passenger luggage is contained in class C cargo holds which are required (at least in the US) to have a fire suppression system as well as a smoke detection system. In an all-cargo aircraft much of the plane is a class E hold, which must have smoke detection, but not a fire suppression system. Therefore certain types of DG have to be segregated into a class B or C area.

So, you can carry perfume in your luggage because the holds on a passenger plane are all class C, where there is fire suppression. But if you send a box of perfume in a cargo flight without declaring it, then it will most likely be loaded in a class E hold where it won't be compliant.


In what scenarios would one want to maximize or minimise rate of climb in an aircraft?

Dogfight is about energy management. You care less about climbing than about being able to turn your nose and weapons into the right direction as quickly as possible without falling out of the sky.

Maximum climb would be required in those scenarios:

Fly as efficiently as possible. Flying higher means flying faster and in colder air, so the engines are more efficient. Note that todays airliners climb as fast or faster than fighter aircraft in WW II.
Evade ground threats. After delivering its ordnance, an attack aircraft would desire to get away from hostile fire as quickly as possible. Sometimes this is achieved by flying with the best climb angle, though.
Break off combat: If you know you can climb faster than your opponent, you can choose whether you fight or get away, a luxury the other guy does not have.
Intercept: If you were ordered to intercept an unknown aircraft flying high above, maximum climb speed is helpful. If you need to be fast as well, your optimum climb profile is that of highest energy gain, though.

I interpret minimum rate of climb as maximum descent rate. Typical scenarios are:

Pressure loss in an airliner, when higher density air should be reached in order to continue the flight safely.
Dropping parachutists: If the aircraft lands ahead of the skydivers, it can fly more often and earn more revenue.
Extreme case: Dive bombing. Actually, most dive bombers employed air brakes to limit the speed in a dive.


What classifies as an ultralight vehicle?

A typical ultralight looks like this, although there are plenty of different designs:

Source: wikimedia.org

Ultralights in the US are defined and regulated by 14 CFR 103. The definition in 103.1 is:

  For the purposes of this part, an ultralight vehicle is a vehicle
  that:

  (a) Is used or intended to be used for manned operation in the air by
  a single occupant;

  (b) Is used or intended to be used for recreation or sport purposes
  only;

  (c) Does not have any U.S. or foreign airworthiness certificate; and

  (d) If unpowered, weighs less than 155 pounds; or

  (e) If powered:

  (1) Weighs less than 254 pounds empty weight, excluding floats and
  safety devices which are intended for deployment in a potentially
  catastrophic situation;

  (2) Has a fuel capacity not exceeding 5 U.S. gallons;

  (3) Is not capable of more than 55 knots calibrated airspeed at full
  power in level flight; and

  (4) Has a power-off stall speed which does not exceed 24 knots
  calibrated airspeed.

And 103.7(b) says:

  (b) Notwithstanding any other section pertaining to airman
  certification, operators of ultralight vehicles are not required to
  meet any aeronautical knowledge, age, or experience requirements to
  operate those vehicles or to have airman or medical certificates.

But, just because you can fly an ultralight without any license or training doesn't mean it's a good idea! You should definitely look into local ultralight clubs to help get you started safely. For example, the EAA has a lot of members who fly (and sometimes build) ultralights and they have some useful information on getting started.


What‘s the thrust of two stacked propellers?

There's a really interesting paper by Manikandan Ramasamy (Hover Performance Measurements Toward Understanding
Aerodynamic Interference in Coaxial, Tandem, and Tilt Rotors, Journal of the American Helicopter Society, Vol. 60, 2015) that talks about this question, which is of great interest for multirotor UAS (which, for rotorcraft, is a substantial number of aircraft): how does stacking two rotor change their efficiency and thrust output?

His test apparatus looked like this: two rotors located exactly one on top of the other, and his apparatus allowed him to measure both torque and thrust produced by each one independently.  He could also vary the distance between the two rotors.  For reference, the rotors are ~4.3 ft in diameter.  Also, just to explain the graphs I'll throw up from his paper, he used blades both with and without twist.

The reason why he has torque sensors is going to come into play with the results.  For a coaxial rotor helicopter (not necessarily for a coaxial prop airplane -- I am not sure which you care about), it is desirable to have a coaxial rotor setup wherein each rotor produces the same amount of torque.  Multicopter UAS then disturb that torque balance to control themselves in yaw.  For the tests Ramasamy performed, they were all done when the rotors were torque balanced, so each rotor produced a torque equal and opposite to the other rotor.

His results are pretty striking, as shown below.  This is a plot of how "interference factor" for each rotor changed with respect to how close the rotors were to each other.  "z/D" refers to the vertical separation of the rotors, z, as a fraction of the rotor diameter.  The interference factor is a measure of the extra power required to turn the upper and lower rotors, ($\kappa_u$ and $\kappa_l$, respectively) as compared to an isolated rotor.  An interference factor of 1 means the rotor is equivalent to an isolated rotor.  Greater than 1 means that it is less efficient than an isolated rotor and vice versa.

As you see, as the rotors get further apart, the upper rotor acts as if it is all by itself ($\kappa_u=1$).  However, the lower rotor is always more inefficient than an isolated rotor due to downwash from the upper rotor.  That said, as the two rotors get closer, the effects get a little more wild.

As the lower rotor approaches the upper rotor, it helps pull air through the upper rotor, so you might think that the angle of the air hitting the blades is getting steeper (also called a higher inflow angle).   This also leads to a lower angle of attack on the blades, leading to the following effects for the upper rotor: decreased thrust production (reliant on high angle of attack to produce more lift) and increases torque input (reliant on inflow angle).  Consequently, $\kappa_u$ increases.

However, since the upper rotor is producing less thrust, the downwash on the lower rotor decreases...and, as you might imagine, it sees the opposite effect that the upper rotor sees: higher thrust production, lower torque input, and $\kappa_l$ actually decreases.  Due to this, you now need to either slow down the upper rotor or speed up the lower rotor in order to achieve a torque balance.

Hence, the first answer to your question is...it depends, but it looks like you actually can get a more thrust out of the coaxial configuration (as opposed to two isolated rotors) if you can space the rotors out well.  This is due, at least in part, to some "swirl recovery" performed by the lower, counter-rotating rotor.  In other words, since a rotor not only pushes air down but also forces it to spin (like a tornado), the lower, counter-rotating rotor sees faster moving air and can take advantage of this to operate at a lower angle of attack: producing the same amount of thrust with lower drag penalties.  However, the effectiveness of this, as said, varies with the separation of the two rotors.

And, again, the larger issue, I think (from a performance perspective) in coaxial setups is not thrust production but power requirements.  One of the two rotors (if not both) is always going to be less efficient than an isolated rotor producing the same thrust.  This is shown more clearly below in a comparison of Figure of Merit (Fig. of merit = (Idealized power requirement)/(Actual power requirement), so a measure of rotor efficiency) versus coefficient of thrust (analogous to the amount of thrust produced by the rotor) for the rotors with untwisted blades.

In short, while you can get more thrust out of a pair of coaxial, counter-rotating rotors, there is no free lunch.  And the lunch can get pretty expensive, at least from a performance point of view (not to mention the extra structure, etc. required for larger axial separation distances).


Why mount multiple autocannons on a fighter or CAS aircraft as opposed to a revolving barrel auto-cannon with a higher rate of fire?

Image source

Same difference as between a shotgun and a rifle: if you need to hit a moving target, like a clay trap target or pigeon or aircraft, it's best to spread the projectiles out so that there is more of a chance that the target meets them. If however the target is (almost) stationary, nothing beats lining up carefully and inflicting the maximum damage with the projectile.

Heavy machine guns are mounted on swivels to create an effective area instead of a line, and only one bullet would be required to stop a soldier. A trap shooter swivels while overtaking the spinning disk, thereby spreading out the spray of shot. But an A-10 lining up for a tank kill wants to maximise impact upon this one tank only - just the one bullet landing anywhere on an armoured tank may not do the job.

When multiple cannons/machine guns are mounted across the wings, the aircraft is set up for dogfighting. Which they are not designed for anymore.


How does wind speed affect helicopter rotor speed?

From your image, the advancing blades (right side) would indeed be faster (relative to the air).
The rotor RPM is fixed all around, but in forward flight—say at 10 knots forward flight like your example—the advancing rotor will have an additional free 10 knots of airspeed (check image below). The other side will be rotating away from that airstream, losing 10 knots.
Red arrows indicate direction of motion, dotted arrows indicate airstream direction, same direction add, different subtract.

The faster side will produce more lift compared to the slower side. This is called dissymmetry of lift.
Solution?
The blades are allowed to flap (change angle) independently from each other, to be able to counter this phenomenon.

If this condition were allowed to exist, a helicopter with a counterclockwise main rotor blade rotation would roll to the left because of the difference in lift. In reality, the main rotor blades flap and feather automatically to equalize lift across the rotor disk. Articulated rotor systems, usually with three or more blades, incorporate a horizontal hinge (flapping hinge) to allow the individual rotor blades to move, or flap up and down as they rotate. A semi-rigid rotor system (two blades) utilizes a teetering hinge, which allows the blades to flap as a unit. When one blade flaps up, the other blade flaps down.
— danubewings.com

Video in French explaining the flapping (good video even if you don't speak French, it's well illustrated).
Animation for flapping.


Are drones used in firefighting, agriculture and pest control?

I once worked in the UAV company, which was contracted to supply a system to identify trees. To achieve this, all you need is a good camera and an image recognition software (now to be easily written using .NET).

I have not heard about drones carrying such large amounts of chemicals, so sorry about that. In this part of the world (eastern Europe) we have enough of our own, conventional planes which do the job just fine (like PZL-106 Kruk). I guess buying drones to do that would not be economical (again I'm just speaking for my country)


Class B and C Airpsace Ring Data in Text

For the US, the FAA National Flight Data Center (NFDC) is the place. There is this set of files: Class B,C,D,E Airspace Shape Files, which is free and contains borders of airspaces in the GIS shapefile format.


When is the use of reverse thrust recommended in airline operations?

The main use of Reverse on landing for big-fan engines is to kill the residual forward-thrust rather than to actually supply braking airflow. This offloads the (wheel-)brakes.

If the runway is short, then the wheel-brakes will need assistance to get the aircraft stopped in time, and then you'd use more Reverse. Some aircraft have an Intermediate Reverse click-stop, which allows you to use a standardised mid-level of Reverse; and then there's Full Reverse, but that gets noisy, which some airports don't like (especially at night).

The level of Reverse used is the P1's decision, while complying with aircraft performance on that runway, the airport's noise policy and the airline's balance between engine wear and brakes wear.


Does the direction of counter-rotating props affect efficiency?

It might. Depending on how close to the wingtips your props are.

If you put the props right at the wingtips, then the conventional rotation to minimize precession and torque actually decreases efficiency by promoting tip vortex (the direction of the prop is the same as tip vortex thereby adding to tip vortex). This reduces lift for the same amount of airspeed.

On the other hand, rotating it the other way round - away from each other - reduces tip vortex by twisting the slipstream the opposite direction as the tip vortex. This increases lift (technically, it reduces the reduction of lift due to tip vortex) for the same amount of airspeed.

One plane that exploited this was the Vought XF5U - the Flying Pancake. The direction of prop rotation is fairly obvious in this picture:

The interesting result of this was that even though the XF5U had very short wingspan it could do short take-offs.


What are the specific number of passengers and conditions required to select HI, NORM, or LOW on the pack flow knob?

From the A320 flight crew operating manual (FCOM):

The selector is kept to NORM in most conditions.

It can be turned to LO:

When the number of passengers is low. 115 passengers is indicative and there are local regulations about the quantity of air which must be delivered per passenger. Operators may have different instructions in their SOP.
When fuel is low for some reason. Using more bleed air increases fuel consumption.
It is also tempting for an operator to reduce fuel and maintenance costs by also reducing air flow. See this thread on PPRuNE.

Air flow can be increased to HI:

Automatically:

When the other pack is turned off.
When APU provides bleed air.

Manually:

When air is too wet due to perspiration and breathing. Dampness increases with the number of passengers.
Air in the aircraft contains smoke.
To intentionally increase tapping of bleed air from the engines, which increases compressor stall margin. This would be desirable while flying in a volcanic ash cloud.

Packs also provide air for pressurization purpose (PACK stands for pressurization and air-conditioning kit). In case of leakage, air flow can be increased. In emergency situations, bleed air can be replaced by ram air (ram air is normally only used for cooling bleed air, but doesn't enter into the pressurized sections of the aircraft).


Do software simulations and wind-tunnel tests accurately predict Cd and Cl in real-world conditions?

It depends.
In computational fluid dynamics (CFD) there are limits for the calculation of turbulent flow. This means that large flow separation cannot be modeled precisely; especially its time-dependent characteristics are computationally much too complex to be modeled. Instead, statistical methods must be used.
For attached and far-field characteristics the methods are refined enough to yield very accurate results, so much that what had historically been studied in wind tunnel tests or only on the finished aircraft can now be calculated with confidence up to hypersonic speeds. Errors still exist - after all, if the geometric model does not include the manufacturing irregularities of the real aircraft, the results will not be in total agreement, but close enough for engineering purposes.
In wind tunnel testing you cannot expect the same results as long as the Reynolds number and Mach number are different from the real thing. This is adjusted with correction factors, and again the results become good enough for engineering purposes. Cryogenic wind tunnels even remove this restriction, but are very expensive to build and operate, because they run with pure nitrogen at very low temperature and several bars of pressure. Small errors remain, because all the details of the real aircraft cannot be modeled in a wind tunnel model and their ratio between dynamic pressure and stiffness cannot be adjusted for all flow conditions, so aeroelastic effects will remain different.
Windtunnel tests are still valuable for predicting forces in post-stall conditions and for calibrating new CFD codes. Most of the operational envelope can then be covered with CFD. The combination of both is enough to predict the force coefficients with confidence, and only aeroelastic effects and details of the stall behavior might turn out slightly differently than anticipated from tests.
As @TrebiaProject points out in the comments, CFD can help with the corrections. The influence of the sting the model is mounted on would be a primary example. CFD can help to understand its influence and correct for it. This makes CFD complementary, so both techniques will lead to better results if combined correctly.


Why is max power time limited for jet/piston engines?

Maybe Nothing....

Maybe Catastrophic Failure...

Any number published by an engine maker (or any aviation part maker for that matter) is the numbers they have tested it to. Thus if Continental or GE claims a 2000 hour TBO but puts a 5 minute limit on max power, that in turn means that the 2000TBO number is based on operations within these published limitations. Exceeding these limitations may cause TBO to arrive sooner than expected and could possibly cause undesired operating characteristics. It is of course possible that if you drive the engine at max power for a time greater than suggested, it will throw itself to pieces. However, this is unlikely.

In some cases there are physical limits based on the materials used in the engine. If exceeding maximum run time provides a way to generate internal temperatures that exceed the limits of an internal part you could very well have an issue very quickly. From my experience with piston engines it's generally a wear and heat fatigue issue when flogging the engine at max power. That being said if the POH calls for a maximum of 5 minutes at full power and you spend 5 minutes and 30 seconds at full power on a climb out chances are you will be fine. If you do this routinely you may find that your engine hits TBO long before the published numbers.

This article also alludes to the fact that there may be other limiting factors such as the strength of the gear box the engine is connected to.

  The shp of a turboprop engine is restricted by the strength of the gearbox that drives the propeller, and by the ability of the airplane to handle the thrust developed by the prop.

On any note I would think that most manufacturers publish numbers that are on the conservative side for many reasons.

Since this question is highly related to TBO number you should check out this article about some common myths around engine overhauling numbers and engine wear in general.

Definitions:

TBO: Time Between Overhaul. This is generally the lifetime of an engine. Although some people commonly think this is a legal number it is only manufacturer suggestion and you are free to exceed it (and plenty of people do).

POH: Pilots Operating Handbook. The document that outlines the limits and safe operation of a given airframe.


How much are noise-related landing costs for a long-range aircraft at Heathrow?

As DeltaLima states, the 787 is a Chapter 4 aircraft.

Directly under the table in your question is another table listing the requirements for each category.

So the categories are based on the certified Chapter, and the margin to Chapter 3 standards. Based on these values, the 787 would be categorized as Chapter 4 Low.

You can look up aircraft in the NoisedB here. Each aircraft is tested for its noise margin. I looked at ID:BOEING_14816, which is a 787-8 powered by a GEnx-1B. It has a noise margin of 30.9, which is compared to the Chapter 4 standard. From looking up a Chapter 3 aircraft like a 747-400, it can be seen that the cumulative reduction between Chapter 3 and 4 is 7.3 EPNdB. I did not see any aircraft that would be above the Chapter 4 Low levels, and most are in the "30 or more" category.


What are these "portholes & panels" on the fuselage of the Omega Tanker DC-10?

The things circled in red are static ports. They are used to measure static air pressure. You can see a close up (from a different aircraft) here:

(taken from this answer)
What you circled in green is an outflow valve used for controlling the pressurization. See also:

What is this device below the door of a 737 (and other aircraft)?
How does the outflow valve work on a cabin pressurization system?
How does a DC-10 flight engineer manually raise the cabin altitude?

It is technically called a Thrust Recovery Outflow Valve:

The actual nomenclature is the "Thrust Recovery Outflow Valve"
[...]
The thrust recovery outflow valve is essentially the valve that controls cabin altitude throughout the isobaric selection range. It can be controlled electrically through 2 electric motors receiving input from the automatic and semi-automatic cabin pressure controller/computer. On the -10's with Flight Engineers, the clutches could be disengaged via a handle at the FE station, and the valve was then controlled through a manual wheel.

(Airliners.net)
Both items are unrelated to the fact that this is a tanker. The following image shows the same items on a Northwest Airlines DC-10-40:

(Airliners.net)


How are wing tanks sealed around the internal wing structure?

The tanks are generally sealed with some kind of putty/resin/epoxy like material. Keep in mind that only the joints between exterior panels need to be sealed. On many aircraft this is done through inspection panels. The material is, in a manner of speaking painted/applied.

Here is an example from a Mooney, which are pretty infamous for having in wing tanks

(source)

Tanks on larger aircraft are not all that different, much like this one off a 747

(source)

its worth noting that tanks don't need to be continuously open, they can have structures with in them as long as the fuel is free to flow around. Large and small tanks alike may very well have structural elements inside with flow holes drilled to allow fuel to move around. These elements also help reduce the effects of large quantities of fuel sloshing around as the aircraft changes attitude.


There are indeed several steps between a pure glider and a powered aircraft. The criteria were historically quite simple:

Gliders with an auxiliary engine, which is just for getting them home in adverse weather, but not powerful enough for take-off. The propeller is in almost all cases retractable, so their aerodynamics is identical to their pure glider version, apart from a slightly higher minimum wing loading.
Motorgliders with an engine powerful enough for autonomous take-off, but with aerodynamics which gives them less than 1 m/s minimum sink with the engine switched off. This minimum sink decides if they are still powered gliders. This would be the TMG category.
Powered aircraft with an unpowered minimum sink speed in excess of 1 m/s. The Cessna 152 belongs into this category.

With the introduction of glassfiber motorgliders with their higher wing loading, the minimum sink rule could not be maintained, and manufacturers lobbied for a change in regulations. As it currently stands, CS-22 defines sailplanes to be within its scope if the maximum weight is below 750 kg. Powered sailplanes must not have more than two occupants, weigh 850 kg or less and have a span loading of 3 kg/m² (mass per span squared) or less.

CS 22.71 restricts minimum sink in unpowered flight to 1.0 m/s for single seaters and 1.2 m/s for two seaters.

Please note that suitable instrumentation should also be added for a motor glider to be counted as a sailplane, such as a variometer.


What are some of the fastest UAVs? How do the pilots ensure that their controls are being transmitted to actions?

The question of the "fastest drone" is not entirely answerable, since whatever answer I give, I'm sure the United States military has a secret drone that goes twice the speed that we have no idea about. I will however put forth the Lockheed D-21 as one of the fastest piloted drones. It tops out at 2,500mph, and was used as a high altitude aerial reconnaissance UAV.

On the other hand, one of the workhorses of the US Air Force is the Global Hawk, a surveillance drone that travels at 400mph.

Regardless of which one you are flying, the speed of communication is the same. Radio transmissions travel close to, or at, the speed of light. That's roughly 670,616,629mph. That's enough to go around the earth more than seven times per second. Due to this, you have near instantaneous feedback from the drones sensors, and near instantaneous control. Yes, things happen faster at 2,500mph, but it is still very controllable.

Beyond the fact that lag is a non-existent problem, take a look at the control stations these guys use.

Due to the fact that they are on the ground which has no meaningful weight limitations, they can equip themselves with a ton of equipment, information, and controls that they would not otherwise have on an aircraft. A few items shown on their screens are sensor feedback for avionics, navigational data, and mission data. With all of these, you really have no human-based excuse for a trained pilot to "lose control" of their aircraft, excluding instances where their transmission may be jammed by a hostile actor. In this situation, the drone has an automatic "Return To Base" function that activates after you have lost control of the drone for a set amount of time.