Where can I download the coordinates of navigation fixes/intersections? Is there an exportable public database that I may get a copy of all navigational fixes and their corresponding GPS coordinates (latitude, longitude)?
p.s. Only US airspace navigation fix information is needed.

The closest I can think of would be the Navigraph FMS data, however this is provided in multiple formats. Otherwise you can use Skyvector to look at them graphically.


Why Search for MH 370 in this area? Consider the above figure:

Why the search is conducted to the red boxed area in the figure. while the actual route of Flight MH 370 is the green line.

The last known position is on the flight path, then

Why not search on East/South China Sea & Bay of Bengal ?

The initial search efforts did indeed take place in the South China Sea.

Interest moved to the Bay of Bengal after new evidence from military radar surveillance showed that the aircraft had turned west across the Malaysian Peninsula after contact was lost over the South China Sea. It took some time for this evidence to surface because the performance and capabilities of military radar systems are usually closely kept secrets -- presumably a lot of people in the military hierarchies had to sign off on releasing it.

Later still, additional analysis pointed to an area in the south Indian Ocean. It turned out that a single communication system aboard the plane had kept working for many hours after the South China Sea loss-of-contact. This is a satellite-based system that is usually used for routine maintenance messages, not for navigation or accident investigation. It took many weeks to get from "the plane was still alive for many hours" to "it went to the south Indian Ocean", through clever and painstaking analysis of data that the satellite company had originally collected for the purpose of tracking the health and performance of the satellite itself, rather than as a way to locate planes.

Part of the information used was how long it took for the aircraft to respond to the satellite each time it checked in (which gave the distance from the satellite to the aircraft at that time), plus minor variations in the RF frequency the aircraft responded at (which combines to give some information about its heading and velocity). The current search areas are the result of that information combined with "reasonable assumptions" about which speed the aircraft was cruising at during this period.

For some time the best analysis of the satellite data could only say that the last contact must have been either in the south Indian Ocean or somewhere around Afghanistan, but the "northern corridor" was later excluded by more detailed analysis. (It was never considered very likely, since it was much harder to imagine how the plane could stay undetected over land, where it ought to have been in view of many primary radar systems than over the ocean, outside of direct radar coverage).


Why do we need to know both groundspeed and airspeed? As far as I understood it correctly:

airspeed: is obtained by measuring the difference in airpressure (using Pitot tubes I guess?) around the aircraft and the airpressure caused by propulsion.
ground speed: is the speed of the aircraft relative to the (immobile) ground.

Ok, I see that there are two types of speed. But why do we need both? Why not just one?

Airspeed is critical for pilots, because it is what the airplane "feels" when it's flying. Too little airspeed and the wings won't generate enough lift to fly, too much and the plane can be damaged. (And you're right, the pitot tube, along with the "static port" is what allows airspeed to be measured.)

Groundspeed is how quickly you're getting where you're going. This is also important, because the engine (or engines) consumes an certain amount of fuel per hour. If you are flying between two airports that are 400 miles apart in a plane that goes 100MPH, with no wind your trip will take 4 hours. If you have a 20MPH headwind your airspeed will still be 100MPH but your groundspeed will be reduced to 80MPH, and your trip will take 5 hours instead of 4. If you've only got 4.5 hours worth of fuel, you're going to need to make a stop. It's really good to know this before you leave!

So airspeed is how fast the plane is flying through the air and groundspeed is, as you observed, how fast you're getting where you're going. Both are important!


What does the "T" on sectional charts mean in reference to airspace altitude? These are present in the San Francisco class bravo / Oakland class charlie and O'Hare class bravo / Midway class charlie.

T is used to signify that the top of Class C airspace that lies under Class B is the bottom surface of that airspace. This is important when the Class C segment lies under multiple layers of Class B, where no single top altitude applies.


What are the effects of headwind on ground speed and take off run? I'm just making sure I got this right.

For the take-off roll, having headwind is preferable, so there is a positive airspeed.

For the en-route segment, a headwind is not ideal and increases time to destination, whereas a tailwind is more favorable.

Short Answer: Yes, you have it right.
For a longer answer consider an example aircraft that has the following characteristics:

Takeoff Speed: 60 knots (Indicated Airspeed)
Landing Speed: 50 knots (Indicated Airspeed)
Cruise Speed: 100 knots (Indicated Airspeed)

Note that all the speeds are airspeeds, which are what we usually measure in flight.
To find the groundspeed you add or subtract the effect of wind, which will become important as you'll see:

A headwind gives the plane a lower groundspeed for a given airspeed.
If our example airplane has a 10-knot headwind it has the following practical effects:

On takeoff the aircraft only has to gain an additional 50 knots to reach takeoff speed:
It effectively has a 10-knot "bonus" from the headwind, and will thus reach takeoff speed in a shorter distance, and need less runway.
Once in the air the headwind works against the aircraft's progress: The groundspeed of the aircraft is equal to its airspeed minus the headwind, so while you're cruising at 100 knots airspeed you're only making 90 knots over the ground. A 100-mile flight will take an extra 7 minutes to complete.
On landing the aircraft will arrive at the runway with a 50-knot indicated airspeed, but because of the headwind will be making 40 knots across the ground. It will thus have less energy to get rid of once it lands, and will require less runway to slow to a stop.

A tailwind gives the plane a higher groundspeed for a given airspeed.
If we reverse our earlier example and give the aircraft a 10-knot tailwind it has the following effects:

On takeoff the airplane must accelerate to a 60-knot airspeed, however it's also being pushed along by a 10-knot tailwind, so it effectively has a -10 knot airspeed standing still: The wind is blowing forward over the wings. When it reaches its 60-knot takeoff speed it will have a 70-knot groundspeed because it's being pushed along by the wind, so it will have a longer takeoff roll.
In cruise the wind continues pushing our example airplane along, so its 100-knot cruise speed gives it a 110-knot ground speed. A hypothetical 100-mile trip would take a little over 54 minutes.
On landing the aircraft arrives with a 50-knot indicated airspeed, but a groundspeed of 60 knots (the wind is still pushing it along), so it will have more energy to dissipate when it lands: A longer ground run, and more braking required.

A chart of the effects of headwinds and tailwinds on takeoff and landing can be found in the Pilot's Handbook of Aeronautical Knowledge, it's reproduced below.

Effects of winds in cruise can be calculated using an E6B Flight Computer


Nemesis Champion Racer The Nemesis Formula 1 racer is a small plane 1991 to 2000 champion setting a lot of speed records.  It went over 260mph, it was fast for its size and engine.  Its fast wing helped it fly fast.  How exactly does its wings fly so fast and smooth?

Three major reasons:

1) Advanced aerodynamics using CFD analysis and wind tunnel testing as well as construction with lightweight and largely seamless composite materials provide a very 'slippery' airframe that doesn't create a whole lot of induced or parasite drag for a given speed.  Very thin, high aspect ratio wings are used.  Access panels are kept to a minimum.  All joints are smoothly blended together.  Landing gear is retractable and fully enclosed.  Fasteners are flush and heads taped over.   Gaps and edges are puttied or taped sealed prior to flight.  The airframe exterior has been waxed and highly polished for as smooth of skin as possible.  The entire aerodynamic envelope has been very carefully studied and optimized to minimize areas producing turbulence and as a consequence parasite drag.

2) Minimized flat plate area.  The cross section of the aircraft has been kept to the bare minimum needed for structures and systems and virtually nothing for crew comfort.  The cockpit is really tight and built around the shape of the pilot's body - even to the point of requiring the pilot wear an oxygen mask connected to a fresh air vent to facilitate breathing.

3) Sacrificing docile handling characteristics.  The wings and flight controls are maximized for high speed flight as opposed to easy and forgiving flight characteristics.  If you look at a Beech Bonanza or a Piper Archer, you'll note that they have very thick wings which handle well at low speeds and give an inexperienced pilot a lot of forgiveness in sloppy handling before departing from controlled flight at the expense of producing a lot more induced drag.  This isn't the case of the Nemesis and it demands a very good pilot at the controls to fly it at the correct speeds and numbers with little margin of error.


What's the best way to see accident rates for a particular make/model of aircraft? I'm looking for a simple way to get NTSB safety statistics for different makes/models of aircraft so I can answer questions like:

How does the Diamond Aircraft safety record compare to general aviation over the last 5 years? All time?
How does does the Diamond Aircraft DA42 safety record compare to general aviation?
What were the (statistically significant) safest aircrafts in general aviation over the prior 5 years? What were the safest jets?

These are examples of questions. I'm mostly wondering if there is a tool or website out there that can help you answer these sorts of questions, or help visualize the NTSB data.

Thanks!

You can search the NTSB's accident database here:

https://www.ntsb.gov/_layouts/ntsb.aviation/index.aspx

Results can be filtered by date, aircraft type, location, etc.

Another good reference source would be the General Aviation Manufacturer's Association.

https://gama.aero/

Their annual report publishes accident data on general aviation aircraft.  The organization may be contacted for further information on this subject.

https://gama.aero/wp-content/uploads/2016-GAMA-Databook_forWeb.pdf


Is a controller at a NFCT required to have an FAA physical? If so what class? Is there a mandatory requirement for a Tower Controller working at a Non-Federal Control Tower (NFCT) to have a current FAA medical certificate?  Is a Class III sufficient?

Yes, you would need a current medical certificate. Source is here (page 4).

Although the above document is for NFCT, they do not mention which class is the minimum. However, I found at other places that for ATC, you do require Class II (sources are here and here).

  Second-Class - Commercial Pilot; Flight Engineer; Flight Navigator; or
  Air Traffic Control Tower Operator. (Note: This category of air
  traffic controller does not include FAA employee air traffic control
  specialists).

This flight school indicates the same:

  Applicants must:
  possess a current, Class-2 medical certificate issued through an FAA certified examiner


Is induced drag not caused by tip vortices? According to most online resources, including NASA, induced drag is caused by wingtip vortices which induce downwash. However, in StackExchange I have found a few answers (Peter's and Jan's) that actually drag caused by vortices is a myth and induced drag is a simple inherent reaction force (vortices and induced drag are both consequences of downwash, which itself is caused by lift creation).
Although this theory looks quite intuitive, I am still confused. Could anybody give me some links to more extensive research of this issue or explain which one theory is scientifically correct and why?

Oh, but they are all* correct!

First, we have to say that we are not talking about cause here. There is a flow around the wing and it has certain properties and neither is cause of the other; they are both effects of the flow. What we are talking about here is explanations why every flow that produces lift also produces induced drag.

And as far as explanations go, there can be more than one, because the physical theories have a lot of redundancy in them. You can usually arrive at the result by multiple ways.

You can use the orientations of the normals (the Peter's answer), you can use laws of conservation of energy and momentum (my answer) or you can use the potential flow theory and that explanation will indeed involve the wake vortices. Because the potential flow theory is a mathematical apparatus for analysing fluid flow as a combination of vortices and from that angle of view, the energy is indeed carried away by the wake vortices.

However, the wake vortex explanation has one problem: it is often associated with different misconception, the one that the vortices are caused by transverse flow around the tip and the resulting idea that it can be eliminated by doing something with the tips specifically.

But that's not what the potential flow theory says. According to the potential flow theory, there is a vortex originating from every point along the span and they combine to form the two tip vortices. So like the other explanations, it also clearly says the induced drag is related to any generation of lift. And if you understand that, it is correct. I still consider it unnecessarily more complicated.

* All the three you listed that is. The ones that claim the wingtip vortex is caused by transverse flow around the tip are not, because it isn't. The wingtip vortex is just the vortex line of the overall wake (and should preferably be called wake vortex).


What is the structural impact on the wing if no fuel is stored in the wings and just in the fuselage? What is the structural impact on the wing if no fuel is stored in the wings and just in the fuselage and how to counter possible advantages/disadvantages? Has this topic already been researched?

This has been well-studied, here are the basics.
For the case of fuselage tankage for fuel: The structural loads caused by the weight of the fuel in a fuselage tank must be transmitted between the wings and the fuselage. This means beefing up the wing-to-fuselage attachment points, which is not required if the wings carry the tankage instead. Putting the tankage in the fuselage also means less room for passengers and cargo.
The best place for this fuselage tank would be right at the center of gravity so the CG shift with fuel consumption is minimized- which unfortunately puts the tank right where the passengers sit. And because this places fuel in close proximity to passengers, it creates a risk factor during a crash.
There are more subtleties involved, but these are the primary considerations. I invite the experts here to weigh in with more details.


Carbureted Rotax engines have no mixture control, how do they handle less dense air? Rotax engines have no mixture control, yet they don't seem to have any more problems than other engines at altitude. How do they handle the lower air density in order to not get a too rich a mixture?

According to this owners manual

4.5 High altitude compensator (H.A.C. kit)
H.A.C. is a high altitude compensator developed by ROTAX which adjusts the air/  fuel
mixture automatically from sea level to 6500 m altitude using a
special BING  carburetor.

This page has information on how the Bing carburetor works (with pictures!):

Here's how it works
Did you ever wonder what makes fuel flow up the jets, from the
carburetor float bowl, enroute to the engine? Is it vacuum at the
venturi?  That's not quite descriptive enough. It is better defined as
a differential pressure between the float bowl and the venturi. What's
the pressure in the float bowl? Here is an important hint, the bowl is
vented to outside atmosphere. So, it should be the same atmosphere, or
ambient pressure, that's feeding the airfilter.  If it is not,  the
differential between the venturi and float bowl is going to change and
so will the mixture...Maybe richer, maybe leaner. Just think of that
for a second. If  fuel air mixture can be thrown off, accidentally by
improperly venting the the float bowls, why not control the venting to
effectively control mixture? That's exactly what your Bing 54 can do,
automatically, when a High Altitude Compensator is added.  If
pressure in the float bowl is reduced, relative to the venturi,  less
fuel makes its way up the jets, and consequently, mixture is leaner.
The HAC unit has two chambers separated by a diaphragm. One chamber is
completely sealed (except during calibration) and air density within
remains constant. The other has airfilter, float bowl, and venturi
connections, so air density on this side is variable. It is in this
chamber, that ambient pressure can be reduced by feeding it to the
venturi via a connection on late model carburetors. The amount of
ambient reduction is controlled by a tapered needle which changes
position with deflection of the diaphragm. Think of the diaphragm as a
flexible wall between two chambers that allows the sealed side to
expand or contract as changes in ambient pressure occur on the other
side. The reduced  (from ambient) pressure gets routed to the float
bowl(s) via their vent lines with a resulting leaning affect..  If
that supply of low pressure is shut off, float bowl pressure returns
to ambient, and the mixture goes as rich as the jets will allow. With
HAC installations, standard jetting starts out several steps richer.
This is why we say the default, or failure mode is typically toward
the rich side.


How are elliptical winglets better than blended winglets? I've read in few papers that elliptical winglets give better performance than blended in terms of their L/D ratio. I am not able to find why elliptical winglets are better. the two differ by their profile followed.
Edit 1: Here  are few references
http://ijari.org/CurrentIssue/2017Volume4/IJARI-ME-17-12-148.pdf

http://www.iaeng.org/publication/WCE2015/WCE2015_pp1144-1148.pdf

Edit 2: The papers explain that elliptical winglets are better than blended just through observations from CFD study.But they do not draw conclusions on how it is better and I couldn't understand that from the contours also.

The best way to understand why elliptical winglets may be better than blended winglets is to read the text of the patent obtained by the inventor of the elliptical type, Dr. Fort Felker, a former NASA wind-tunnel researcher and expert in the field of computational fluid dynamics, and co-founder of Winglet Technology LLC.

The short answer is that the curvature of the winglets as they extend outward from the intersection with the wings approximates part of an ellipse (hence their name), and this apparently ensures an elliptical distribution of lift both horizontally and vertically, resulting in lower induced drag than a blended winglet.


What are those structures at Taif Regional Airport in Saudi Arabia? I was looking at airports in Saudi Arabia and noticed a strange one. At Taif Regional Airport near Mecca there are a bunch of taxiways all seemingly randomly intersecting at different angles, each with a bulge in their width and a structure built in the middle of the bulge. Based on the shadows, they seem to be sunken by some amount with the structure built to roughly the same height that the taxiway is sunk. I counted at least 30 of these structures. The measuring tool on Google maps shows them to all be around 135 feet wide, and of various lengths.

I couldn't find any information about these structures or their purpose. Are they hangars of some sort? If so, why the strange design?

Those are hardened aircraft shelters, and each hangar is flanked by two blast walls (revetment). Those are for combat aircraft (the airport is mixed-use: public/military).

Since in that hemisphere the sun is to the south, the shadows tell us they are not sunken structures, i.e. the hangars and walls are higher than the taxiways.

The numerous taxiways are for redundancy against bombing. And the overall pattern makes it harder for a single bomb run to affect all hangars.

Here's an aerial close-up from another Saudi Arabian airport, Tabuk Regional Airport:

  Source: flickr.com


What is the regulatory definition of AOG? What is the legal or regulatory definition of AOG (Aircraft on Ground)? For example, this is sometimes stamped on a repair order.

There is no regulatory definition of the phrase "Aircraft On Ground" as used in work orders or repair orders in the FARs (14CFR), it is used by convention to indicate that the order is urgent as the parts or repairs specified must be completed in order to fly the aircraft.

What causes the aircraft to be grounded can be a functional issue that (such as a damaged control surface: The aircraft is grounded until it's repaired or replaced) or a regulatory one (for example, an airspeed indicator is part of the Day VFR required equipment, if it fails even though the plane can physically fly it's not legal to do so - your new airspeed indicator would be an AOG parts order).


What are the effects of rotating airfoil sections to match wing's dihedral? While designing a wing, what are the advantages and disadvantages of rotating the airfoil sections to match a linear dihedral (airfoil sections always perpendicular to the dihedral line)? Does the lift force component tilts inwards and because of that, horizontal component  cancels out and there is a decrease in lift?

All you do by not tilting the airfoil (around its longitudinal axis) is to reduce the relative thickness of the wing. Since that effect is proportional to the cosine of the dihedral angle, the effect is negligible for realistic values of dihedral.

Lift will most certainly not be affected, because it, being at its root a pressure, always acts perpendicular to the local surface.


When do pilots actually use ‘wilco’? I know it means “I have understood the instruction and will comply.” However, any instruction that

is a clearance,
concerns runway use or
contains altitude/level, heading, speed or squawk code

should be read back. And that seems to cover most instructions.

So what is an instruction, but does not require a read-back and may be instead answered by just ‘wilco’ (+ callsign)?

When instructed to report something.

ATC: Cimber 626 turn left heading 120, cleared ILS approach runway 09, report established
Pilot: Heading left 120, cleared ILS approach runway 09, WILCO, Cimber 626

ATC: OYABC airborne time 33, report passing Dalhem
Pilot; (Roger), WILCO, OYABC

ATC: Lufthansa 135, traffic is a Boeing 737 on 5 miles final for runway 09, report in sight
Pilot: WILCO, Lufthansa 135


How does a pilot make sure they have received all applicable NOTAM's? I've always wondered how a private pilot makes sure they have read all the NOTAM's that might affect their flight. There must be thousands of NOTAM's out there. This question talks about the many types. Some will be just for the day, some applicable for months. Some affect large areas, some just one taxiway. If doing a cross-country flight, especially to an unfamiliar airport, how does one know how to wade through all of them and be sure they've covered all of those that might affect their flight?

A quick lookup tool is PilotWeb.

The pilots may receive NOTAMS during flight briefing.  The best way to ensure that you are getting proper NOTAMS is to request all NOTAMS for the route of flight you have filed when you speak with the flight briefer.  The briefers are trained professionals, and they know what NOTAM information to provide to pilots, but it must be requested!

The FAA says this in regards to a standard briefing:

  Notices to Airmen (NOTAMs)

  (a) Available NOTAM (D) information pertinent to the proposed flight,
  including special use airspace (SUA) NOTAMs for restricted areas,
  aerial refueling, and night vision goggles (NVG).

  NOTE- Other SUA NOTAMs (D), such as military operations area (MOA),
  military training route (MTR), and warning area NOTAMs, are considered
  “upon request” briefing items as indicated in paragraph 7-1-4b10(a).

  (b) Prohibited Areas P-40, P-49, P-56, and the special flight rules
  area (SFRA) for Washington, DC.

  (c) FSS briefers do not provide FDC NOTAM information for special
  instrument approach procedures unless specifically asked. Pilots
  authorized by the FAA to use special instrument approach procedures
  must specifically request FDC NOTAM information for these procedures.

  NOTE- NOTAM information may be combined with current conditions when
  the briefer believes it is logical to do so.

  NOTE- NOTAM (D) information and FDC NOTAMs which have been published
  in the Notices to Airmen Publication are not included in pilot
  briefings unless a review of this publication is specifically
  requested by the pilot. For complete flight information you are urged
  to review the printed NOTAMs in the Notices to Airmen Publication and
  the A/FD in addition to obtaining a briefing.

If someone is performing a self-brief via 1800wxbrief.com, which is the best internet briefing site in my personal opinion (because it will tell you if you make a mistake rather than purge your flight plan without telling you), they can see NOTAMS invoked by relevance to their proposed flight path.

So to be sure you're getting everything, call 1-800-WXBRIEF via phone and file that way and request NOTAMS from the briefer.

One last thing that needs to be reiterated here:

  "This
  question
  talks about the many types [of NOTAMS]."

There are various classifications of NOTAMS, but for all intents and purposes in the civilian world, we have two types of NOTAMS; Distant-(D) and FDC.  That's it.

Civilians haven't had local NOTAMS in the US since 2008 when an advisory circular announced that they were being packaged into NOTAM-(D)s


Is lift generated only by wings? In modern aircraft is lift only generated by wings or can other parts of fuselage generate a significant amount as well, to the point it needs to be accounted for when designing a plane?

The fuselage, and any other surfaces that air is flowing over, will contribute to lift.  This was one of my interview questions when I joined Airbus in 2003!


Why is the Priority Takeover button used? On the sidesticks of Airbus aircraft, there is a Priority Takeover button. Wikipedia has this to say:

In typical Airbus side-stick implementations, the sticks are independent. The plane's computer either aggregates multiple inputs or a pilot can press a "priority button" to lock out inputs from the other side-stick.

On US flight 1549, the CVR transcript shows that Sully hit the Priority T/O button, after the co-pilot (Skiles) handed over control of the aircraft:

15:27:23.2 - Sully: My aircraft.
15:27:24.0 - Skiles: Your aircraft.
15:27:26.5 - FWC: Priority left.

I'm curious as to why there's a need for this button at all?
Here's a short video on YouTube, demonstrating this:

It's been several years since I worked at United's flight training center, but if my memory serves me, it is there in case the system is receiving input that the pilot wants to exclude. As was explained to me, an example of this would be the other pilot becoming incapacitated, with their body leaning against the sidestick. In this case, one would want to use the Priority Takeover button to eliminate the other pilot's input.

In Captain Sullenberger's case, it is likely that he wanted to ensure that First Officer Skiles wasn't providing any control inputs that would work against his control inputs.

Now, it is also my understanding that such functionality is not useful in a "hostile takeover" event, since the other pilot can also attempt a priority takeover (or use physical force, due to the close proximity of the two pilots).


What is the outer kink on the airbus 340-600? I was checking some information about the a340-600 and got this statement: "thickness/ chord ratios 15.25 per cent at root, 11.27 per cent at inner kink, 9.86 per cent at outer kink and 10.60 per cent at tip"
I know where the inner kink is but what is the outer kink and where is it located?

The outer kink on A340-600 wing is located just outboard of the outboard engine, note trailing edge kink in planform drawing.


What responsibility does a pilot have for people on the ground when making an emergency landing? Recently, a Cessna made an emergency landing on a crowded beach in Portugal. The two occupants of the aircraft did not sustain any serious injuries, but two people on the ground died.
A couple of years ago, a similar incident occurred with a Piper in Florida. Again, the occupants were unharmed, while two people on the ground died — one at the scene, the other later succumbed to her injuries. The main difference is that here, the pilot hadn't noticed them and thought he was landing on an empty beach.
In Portugal, however, the beach was not just not empty, it was crowded. And the pilot could have known it would be, too — it was summer in Europe and a lot of beaches are crowded every summer.
It's hard to tell while the investigation is still ongoing, but in a situation like this, shouldn't a pilot choose another way to resolve the emergency?
I understand that a pilot's first responsibility is to the people on board the aircraft, but what are a pilot's responsibilities to people on the ground?
Are there any differences in the different legislations (FAA / EASA)?
Are there any other laws applicable? Have any precedents been set in court?

As noted in a comment, the flight instructor and the trainee have appeared in court, facing charges of negligent homicide.
"Portugal pair in court after fatal plane beach crash", BBC News.

Factors in pilot choices are often subject to political spins, as few people are able to objectively evaluate the information available to the pilot, the bandwidth to manage the events, and the conditions which may have added complexity as well as the experience level of the pilot. A student pilot logically is held to a different competency expectation than a commercial/ATP with 15,000 hours in type, intimately familiar with the conditions, etc.

In common law, the pilot is supposed to protect in order, innocent third parties, the passengers, the crew, and property of others.

Where there were people impacted (no pun intended) who were not seen or known to the pilot/crew, that becomes a mitigating factor.

The bulk of civil liabilities on flight crews is established in case law, as there are few statutes which address that, at least in the US and Canada.

Addendum #1 Protection of innocent third parties, is first order as they have not elected to become part of an aviation event.  Passengers need protection because it is the duty of the crew to protect passengers, even if non-paying. Of course passengers assumed some risk by electing to fly. Crew need protection because they are humans.  Property is last.

Addendum #2, incorporation of comments, per requests. Comments are largely unedited, simply included to preserve the record. The comments were in response to a challenge for authorities on the common law obligations of pilots.

HLS Torts 2, Aviation under the Common Law, Francis H. Bohlen , and for contributory relation: Recreational boating accidents: Which law applies? Kevin Donius, for duties: TRITCH, ALLAN M. University of St. Thomas Law Journal: Fides et lustitia 2014/04/01, Vol: 11, p331, for practicality, and legislative mix: Fifty Years of Torts Harvard Law Review, Vol. 50, No. 5, Kohr, 504 F.2d 400 (creating federal common law of contribution in aviation accident). Kohr figures prominently in Professor Field's theory of federal common law, see Field, supra note 14, at 913-15, but almost certainly does not survive the refusal to create a federal common law right of contribution in antitrust cases. Tex. Indus., Inc. v. Radcliff Materials, Inc., 451 U.S. 630 (1981)

But see Musick, Peeler & Garrett v. Employers Ins. of Wausau, 508 U.S. 286, 292 (1993) (creating "ancillary" common law right of contribution in implied Rule 10b-5 right of action). Indeed, within seven years of Kohr, even the Seventh Circuit did not think to use federal common law to deal with the complex conundrums of choice of law analysis in an aviation accident. In re Air Crash Disaster Near Chicago, Ill. on May 25, 1979, 644 F.2d 594 (7th Cir. 1981).

The Bohlen one, while dated (~1937) hits many of the foundations. But the boating one points out that by being a passenger you accept a greater risk than an independent third party. In the Torts class, I did a couple of papers on aviation torts. The rest of the cites become rather obtuse, because the focus in most litigation is not on common law, but on statutes. Yet, in NY, the bar exam covers common law. Go figure.

I cannot comment of EASA regulations, but generally the FAA regulations do not cover tort liabilities. Tort law and common law, where applicable, would appropriate references. This may be more relevant for SE Law. FAA regulations cover operational matters, certification, registration and administrative aspects of aviation.

Also the liabilities can be quite complex, for example in the Chicago crash, state Public Utilities Act was invoked, which added one of many local complexities to the litigation. That kind is stuff is, I believe, beyond the scope of SE Aviation.

This congressional intent not to exclude state statutory and common law from the field of aircraft safety is further illustrated by the existence within the Federal Aviation Act of a savings clause. 49 U.S.C. app. 1506 (1988)


Why doesn't frost form on a moving airplane? When I was a young student pilot, long before the FAA prohibition on polished frost went into effect, an instructor left a six-inch square of frost on the wing to demonstrate how fast it would disappear after takeoff.  Sure enough, we hadn't even reached pattern altitude and the frost was completely gone.  Furthermore, in my experience frost never forms on an airplane as long as it's moving, or as long as there's sufficient airflow moving across it.

I've never been able to find a satisfactory explanation for this.  Why doesn't frost form on a moving airplane?

Frost can be formed in two ways. On a colder object by water directly desublimating on its surface or on any object when air is saturated with water.

Frost can form on a moving airplane, but only the second way. Why would they have anti-ice on pitot tubes, propeller and leading edges otherwise?

When the air is not saturated with water, ice will sublimate. If the air is moving it carries away the sublimated vapour and thus increases the sublimation rate. When flying in visual meteorological conditions, that's generally the case, so frost won't form in VMC, thogh watch out when dew point is close to temperature; in such case light haze may form that already causes some icing while visibility is still above the VMC limit. Ram and friction heating also help sublimating the ice a bit.

However when you fly into a cloud in freezing temperature, the water droplets will freeze on the aircraft when they hit it. They will hit it on forward-facing surfaces: wing and stabilizer leading edges, propellers, engine inlets, pitot tubes and nose and windscreen. That's why these components have anti-ice, either using heating or deicing boots.

VMC-only aircraft will often only have pitot tube heating and carburettor heating, because those can sometimes gather frost in sufficiently moist air that is not yet forming cloud. This lack of anti-ice makes flying into IMC even more dangerous in winter than it already is for all the other reasons.

Icing only happens when the cloud contains supercooled water droplets, which occurs in clouds where the ambient air temperature is between freezing point (0°C/32°F) and around -40°C/-40°F when the droplets freeze to ice pellets. The exact point the droplets freeze varies somewhat because it depends on other parameters like amount of dust, but pilots can check whether they are accreting any ice by looking in the corners of the windscreen. Whether freezing conditions are to be expected will also be mentioned in the detailed weather forecast.


Why does Germany is not so advance in aircraft development? I tried to see what countries are the most advance in developing aircraft. I found that Germany is not so advanced (CMMIW). Indeed, there is Dornier there beside has share in AirBus. I don't know whether they are the biggest share holder or not in AirBus.

In another side, among of the G8 countries, US is the leader. They have lot of aircraft industries. Boeing, Lockheed Martin, GulfStream, and many other. Canada has Bombardier. British has BAe with their RJ70, RJ100, so do Roll Royce with their power plant. Italy has Avanti and Augusta Westland, beside small aircraft industries. France with Dassault, Mirage, also joint venture AirBus, and some more small industries. Russia has Sukhoi, Ilyushin, Tupelov, Mikoyan, Beriev, and there are more. And Japan has Mitsubishi, Kawasaki, and Honda, now they are massively develop and  research aircraft, both for civil and military. But Germany is look like not so aggressively take part in this technology like they do in another part. Even China is now growing. With Comac, they has now C919, and now with Russia is developing C929 which will emphasizes their presence in aviation manufacture. ABC, AirBus, Boeing, and Comac are considered as the biggest manufacturer, leaving Germany behind. Is any reason why? Germans probably can explain.

May i suggest, you read the wikipedia artikle "History of Airbus".History of Airbus
There are also other big aerospace companies in germany, like MTU, DIEHL and LIEBHERR just to name a few. These companies don´t build their own planes, but manufacture major components for the aerospace industrie.


What are the advantages of the angled flight deck layout used by some aircraft carriers? I've been flying aircraft carrier approaches in a flight simulator lately and noticed that the carrier has an interesting layout. I have an image below where the landing runway is in red and the takeoff runway is in blue.

I can understand the takeoff runway - taking off into the wind with the catapult so that you can get enough air flowing to take off. The part that confuses me is the position of the landing runway. It is at a slight angle to the direction of the carrier's motion, meaning that when I fly the approach I have to aim to the right of the carrier and let it move underneath me. It seems to me as though this would just complicate an already difficult procedure, particularly in rough weather conditions.

Why not just take off and land in the same direction? As far as I am aware the aircraft only take off forward of the jet blast shields i.e. at the tail of the blue arrow. This would leave plenty of room on the carrier for landing. The only time I can think this would be a problem would be when a pilot needs to abort the landing and quickly take off again when there is another jet waiting to take off ahead of him, though this would assume that aircraft were taking off at the same time as others were landing (I have no idea if this actually happens).

It would be great if someone could shed some light onto why aircraft carriers have this layout - I'm not a pilot, just been playing around in simulator.

This kind of layout is called the angled flight deck (also called 'skewed' or 'canted' deck) and was first used by Royal Navy. There are a number of advantages to this layout compared to using the same direction of landing and takeoffs:

It allows concurrent landings and takeoffs.
By having an angled deck, the aircraft which fail to connect (with the arrestor cables) during landing can go around and try again without risk of damage to other (parked and taking off) aircraft).

The main reason for the emergence of angled deck was the introduction of jet aircraft in naval operations, which due to their weight and high speeds required most of the deck available to complete an arrested landing. Also, in case of missed wires, it was possible to use a barrier in case of propeller aircraft, which was not possible in case of jet aircraft. According to Rear Admiral Dennis Campbell, the inventor of angled deck,:

  But with the advent of the heavier faster jets, it soon became obvious that the dimensions of the carrier's deck would impose a limit to the standard of aircraft that could be operated. The inevitable increase in weight and landing speed of the jets would make it impracticable to retain the existing combination of arrester wires/barriers/and deck park without a drastic reallocation of the deck space required to absorb the much longer pull-out of the wires.

Prior to the application of the angled deck, this caused significant problems and requirement of complex machinery to overcome.

  Ark sister ship and predecessor, the Eagle, was equipped with sixteen arrester wires and three different types of barrier (together with all their several hydraulic machines), and all this gear could only just cope with the first generation for (straight wing) jets.  No way would such a layout be good enough for the newer types.

The solution was to skew the flight deck by about 10 degrees (the HMS Ark Royal first had the flight deck angled by 5 degrees, which was then increased to 10) and use it for landing. This lead to:

  The saving in arrester gear units and barriers – Ark needed only four wires and one (emergency only) barrier.  The reduction in weight and the extra space that this conferred enabled more mess-decks to be fitted in, thus reducing congestion in living spaces.
  Since landing accidents would obviously be far less frequent, fewer aircraft and spare parts would be needed so costs would be greatly reduced.
  Similarly, death and injuries to aircrew and deck handlers could be kept to a minimum – with a big boost to confidence and morale, not to mention the saving in training costs.
  As experience was gained of the new scheme, less obvious advantages came to light.  New areas of parking, (abaft the island for instance); an added flexibility in the relative wind speed and direction, easier and faster deck handling, less wear and tear on the command, etc.

Perhaps surprisingly, though the USN has adopted this system in its supercarriers, the RN dropped it later on.


How are pitching and rolling moments transferred from rotor to the body? When a rotorcraft pilot moves pushes on the cyclic control stick, the swashplate tilts so that angle of attack of the retreating blades increase and of the advancing blades decrease, which creates forward pitching moment on the rotor (shifted 90° due to gyroscopic effect).

Now the first reaction is that the blades flap up aft and down forward, tilting the plane of rotation forward. But which is then the dominant effect that makes the helicopter body to follow the pitch?

Is is the blades pulling on the hub due to centrifugal force trying to align it with their own plane of rotation,
or is it that the lift vector tilts with the rotor so its action line no longer passes through the centre of gravity?

The impact of these effects depend on the rotor design.  E.g. a teetering rotor only includes the second effect you mentioned (tilted thrust vector), the 1st effect is absent.  The first effect you mentioned increases as the "flap hinge" is moved away from the hub, giving more control force utilizing CF.  You may be interested to know there's typically a 3rd effect - if the blades are restrained from flapping freely (in the simplest case a spring) that restraint creates a pitch moment about the hub which also pitches the aircraft.   Each of these is discussed here.


Why is the extra allowance for wheel installation on A380 in terms of degrees instead of torque/torque percentage? When installing a wheel on the A380, the nut is permitted to be torqued an extra X degrees if the holes do not align.

Any idea why its in degrees instead of X torque or percentage of torque value?

The reason is simple, the measurement from the point correct torque is achieved to the location of the hole for the bolt is in degrees, not ft-lbs (the number of degrees is absolute, whereas the force needed to get the alignment can vary). The torque specification has a built-in tolerance for additional torque needed for alignment. If you have to go more than X degrees to align it means you'll be applying excessive torque.


What are the differences between Normal and Utiltiy Categories In the operating handbooks for GA aircraft, there are often weight and balance limitations listed for both Normal and Utiltity category operation.  If I restrict the loading to the Utility category envelope, I want to know what regulations and prudence allow me to do over the Normal category envelope.

I am guessing that there are a set of regulatory certification standards for each category, as well as a list of specific restrictions for each type certificate.  What are these definitions and where are they found?

From a regulatory standpoint the governing regulation is FAR 23 (airworthiness standards for what we'd generally call "small" airplanes - Normal, Utility, Acrobatic, and Commuter category).

FAR 23.3 is probably what you're interested in, and tells us:

Normal Category is limited to airplanes that have a seating configuration, excluding pilot seats, of nine or less, a maximum certificated takeoff weight of 12,500 pounds or less, and intended for nonacrobatic operation.
They go on to specify that nonacrobatic operation includes:

Any maneuver incident to normal flying
(for very vanilla definitions of "normal" - they expect you to use some common sense here!)
Stalls (except "whip stalls")
What most pilots recognize as the "commercial flight test maneuvers": Lazy eights, chandelles, and steep turns, but with an angle of bank not greater than 60 degrees in any of these maneuvers.

Utility Category is the same type and size of airplane, but approved for "limited acrobatic operations" - this may include intentional spins, as well as the "commercial maneuvers" with higher bank angles (greater than 60 degrees, up to 90 degrees).
Acrobatic Category is the same type and size of airplane, but approved for acrobatics  without any restrictions "other than those shown to be necessary as a result of required flight tests" -- basically "airplanes that can go upside-down".

The commuter category is boring: It's basically the normal category, but with more engines (at least 2) and more seats (up to a maximum of 19). Commuter category aircraft can also have a higher maximum takeoff weight (up to 19,000 pounds).

An aircraft can be certificated in any combination of the Normal, Utility, and Acrobatic categories if the aircraft meets the requirements of the appropriate category (as specified later in FAR 23).  An aircraft certificated in the Commuter category may not be certificated in any of the other categories however.

Generally the restrictions you find on aircraft are not regulatory ones (from the FARs) but Operating Limitations (in the POH or placarded on the aircraft) which you must comply with (per Part 91 of the FARs).

For example, the Cessna 172 and the Piper Warrior are both dual-category aircraft (Normal and Utility), and specify a "Utility Category CG Envelope" in their weight and balance charts.

The Piper Warrior is not approved for spins in the utility category (they are placarded with SPINS PROHIBITED). they also have other restrictions for utility category operations which are found in the POH and on aircraft placards (e.g. UTILITY CATEGORY - NO BAGGAGE OR AFT PASSENGERS, and maximum entry speeds for other acrobatic maneuvers).

Most Cessna 172s are approved for spins in the utility category and are not placarded against them. (Certain aircraft with specific STOL kits installed are disapproved as a result of the kit, and have placards prohibiting them).


Pitching Moments CG vs CP vs AC Probably the question will be a little bit confusing but I'll try my best to make it clear.
Due the position of the CP with respect of the AC, symmetrical airfoils don't produce pitching moments, but cambered airfoil having the CP behind the AC produce a nose down pitching moment.
If we consider now the CG effect, a CG forward the AC will cause a nose down pitching moment, an aft CG the opposite.
Most aircraft with variable incidence tailplane have the possibility to trim much more degrees for nose up than for nose down.

Is this mainly due to the position (and range) of the CG, delianeated during the design phase and normal flight operation?
Is the pitching moment of the wing (only), much less relevant?

The root cause is the nature and theory of aerofoils. The design mission is to use the wing in an optimal way and finally the wing + body combination in the most optimal way to achieve the design goals. Most of the design goals answer to the following questions:

do you want to go fast (speed), or
do you want to lift more weight (payload),

For a given amount of fuel

do you want to go as far as possible (range), or
do you want to stay in the air for the longest period (endurance), OR, combinations such as
do you want to carry a specific weight a specific distance?

There will be an optimal aerofoil for each of these, and new designs can be attempted if there isn't one that fits the requirement or it is felt that there's room for improvement.
There are some aerofoil properties that tend to be common for the bulk of the commercial jet designs, as most of them are chasing similar goals:

generally best efficiency (in terms of L/D) is around 4˚ to 6˚ AoA. This angle is  achieved by combining a level flight pitch attitude of 2˚ to 3˚ with the wing mounted at a 2˚ to 3˚ Angle of Incidence**.

Stalling AoA in clean configuration somewhere around 15˚+, and

most of these aerofoils even produce lift till 1 or 2 degrees below 0˚ AoA.

With high lift devices extended, the typical AoA could vary between 7˚ and 10˚depending on slat/flap configuration.

(** Angle of Incidence: wings are mounted with the leading edge higher than the trailing edge, so the angle between the average chord line and the longitudinal axis of the airplane is fixed and it is called the Angle of Incidence. Thus an airplane rolling down a runway already presents an AoA of a few degrees and inflight, we don't have to cruise at an uncomfortable pitch attitudes of 5 to 6˚ nose up )
The physics of aerofoils and aerodynamics, as mentioned above, dictate that, the airplanes are mostly flown at different nose high attitudes of upto 20˚ including the slat/flap extended regime of flight, and climb phase. Much lesser part of the flight is spent at negative pitch attitudes of 0 to -4˚ for descents. Thus the 'lopsided' stabilizer range.
The Stabiliser settings for take-off depend on the CG, GW (Gross Weight) and T/O Thrust for the flight so as to present a 'standard' stick force and control effectiveness for the pilot and it must be understood that though weight acts through the CG, the GW is actually acknowledging the Lift being created by the wing to lift that weight.
BTW, a symmetric aerofoil produces no pitching moment only at zero Angle of Attack. Mount it at a small angle of incidence and it will produce a lift component acting through CP. It's just that there are other aerofoil shapes that have fewer compromises affecting the typical design goals.


Lights at the end of both wings of any airplane Can anyone please explain to me why there is one green light at the end of wing and on the other side there is red light? what is the purpose of it and why it uses different colors like red and green instead of same color light?

The question is not about the position of the lights but why they use different color lights? like red light on the left side and green light on the right side. Is there any specific reason for that?

Same as on ships, the navigation lights (green on right side, red on left side, white on aft tip) are there to allow visual judgement about another vehicle‘s position and orientation (and thus relative headings) at night. E.g:

if you see red and green, you are looking head on at another vehicle
if you see only green, you are looking at the right hand sector of the other vehicle
if you see red and white, you are looking at the left hand aft quarter

and so on.


What is the willingness of non-AME/pilot physicians to perform BasicMed exams? May 1st, 2017, BasicMed rolls out and for certain operations and certain pilots BasicMed promises a much more permissive and yet preventive oriented approach to medical approvals for pilots.

A concern is that one's physician may not issue BasicMed.

From AAFP's newsletter, where BasicMed was overviewed for Academy members (mostly Family Practice Physicians), I have extracted the following excerpts.

  In an interview with AAFP News, Cowl stressed that physicians should
  understand FAA medical guidelines as they pertain to potential
  liability.

  "There is the potential for liability to physicians, in part because
  the pilots most likely to use the alternative qualification pathway
  may be the very people who need the standard flight physical," said
  Cowl.

  ...

  "At that altitude and type of airframe, these planes are sharing the
  airspace with paying commercial passengers. As physicians, we need to
  maximize the health of our patients and promote aviation safety," he
  said.

  Simply put, "This comprehensive medical checklist is not a summer camp
  physical," said Cowl. Physicians should familiarize themselves with
  FAA guidelines, communicate with aviation medical examiners in their
  communities and understand the liability they take on when they put
  their medical license number on the FAA form.

  Cowl acknowledged that some family physicians may already perform
  commercial truck and bus driver examinations that are similar in
  nature to pilot exams. For those physicians, a certain comfort level
  may already exist.

  However, he added, "Physicians who do these exams need to be cognizant
  of the 'ask' -- and that is to perform a comprehensive exam and then
  sign an attestation statement that says, 'Based on my comprehensive
  exam, this person is safe to fly.'"

So I asked my non-pilot family practice doc whether he would be doing BasicMed exams.  "Absolutely not.  Truck drivers are one thing, but flying planes and the liability potential is too great for me to stomach."

I asked another FP doc, and she told me that she would avoid doing the exams, because as she understands them, they require a comprehensive physical that has higher complexity than other physicals she performs, and along with it there is an unknown liability potential, which is new to the risk market and she doesn't like being a guinea pig.

Then I talked with a former student of mine, who is an emergency medicine attending, and holds a Private Airplane-Instrument certificate.  He has been tracking BasicMed, because it is relevant to him.  He hauls his family around at vacation time in his Saratoga, and BasicMed meets his requirements. "Honestly, I will just see (my AME) and get a regular third class medical.  I don't know anyone who wants to touch BasicMed if they are in private practice.  If you get someone working for a hospital clinic, it might be different."

So my question is: Is there any preliminary data on the willingness of physicians to perform BasicMed exams, and in particular those who are not AMEs or pilots?

Addendum #1

https://generalaviationnews.com/2017/05/18/basicmed-is-creating-conversation/

An update article, after the start of BasicMed.

I have Kaiser insurance and tried really hard to get them to conduct my physical, to no avail. I was thwarted by some degree by the fact that my regular physician is not seeing patients right now, but my suspicion is that she may not have done it either. However, I have also heard of Kaiser members who did convince their physicians, so apparently there is some wiggle room. I ended up going to a clinic that does the DOT exam after asking if they would also do basic med - the doc turned out to be a pilot himself. Saved just a few buck compared to an AME.

As to why some folks would do basic med rather than a third class, at a certain age the third class is only good for a couple of years, while the basic med exam is good for five. That's why I elected to go with Basic Med. (I read recently that BM won't allow flight outside of the US, including Mexico or Canada, so that's something to keep in mind if you fly in those areas...)


What is the identity of this abandoned, wrecked Sudan Airways airliner? The other day, I was browsing Twitter, when I came across this picture of an airliner posted by a Sudanese local (thought it was a Boeing 737, but a friend of mine pointed out that it was an Airbus A300). I tried Google Image Searching it, but couldn't find any more details about how it got to be wrecked in this condition ...
Could anybody shed a light on this?

It looks to me more like an abandoned plane (that's fallen apart) rather than a crashed/wrecked one. A Sudanese A310 crashed at Khartoum in 2008 - but it caught fire and was destroyed, which clearly hasn't happened here unless someone came and repainted it afterwards.

This list gives ten A300s which have previously been owned by Sudan Airways; TC-OYC is stored at Istanbul (and this doesn't look like Istanbul), ST-ATA is stored location unknown, and ST-ASS was scrapped while last owned by Sudan. Of their A310s, ST-AST, is stored (location unclear); ST-ATN was destroyed by fire after a crash. So that's three A300/310s which might plausibly be lying derelict at a Sudanese airport.

For an alternative count, this thread lists four A300s "stored" at Khartoum, ST-ATA, ST-ATB, ST-ASS & ST-AST; all put up for sale as parts/scrap a few years back but never sold. No pictures but it's clear they're not in a great state.


Would the Gee Bee be allowed to fly today, with so little forward visibility? When looking at the Gee Bee:

Source

I wonder what the pilot is actually able to see, when rolling on the runway, when flying level, or trying to locate a possible emergency landing place. It seems this aircraft puts the pilot and the people on the ground at risk.

Wouldn't a mirror improve safety, or is there a hole in the bottom of the fuselage?

How could such an aircraft be allowed to fly at the time? Did flying it only require to hold a recreational private pilot license or additional qualifications? Would it be allowed today in Europe, or in the US, based on existing regulation?

At least it has a forward looking windshield.

(Source) Spirit of St. Louis that was flown solo by Charles Lindbergh on May 20–21, 1927, on the first solo non-stop transatlantic flight from Long Island, New York, to Paris, France.

(Source)

(Source) A 777-300 needs a camera too to make cornering easier.

Like all tail-draggers, the pilot can be guided by a wing-sitter, or by taxiing in an S-shape.

For landing, a little cross-control to crab will allow a side view of what's ahead.

Above methods were/are very common for WWII-era planes with huge noses and a tail-dragger undercarriage.

(Left, right) Taxiing with wing-sitter assistance.

Landing on big grass-fields makes it easier too.

  Would the Gee Bee be allowed to fly today?

The Gee Bee was still flying airshows until 2002, so the answer is yes.

(Source) Gee Bee R2 flown by Delmar Benjamin at Oshkosh 2001. Benjamin flew an aerobatic routine in this aircraft at numerous airshows until he retired the aircraft in 2002.


How is horsepower measured for aviation piston engines? As far as I can tell, aviation piston engine power output is typically measured in HP (horsepower).

Automotive engine power output is typically measured by running the host vehicle on a rolling road, or dyno or dynamometer.  This directly produces a torque curve, which may be integrated with respect to RPM to provide a power curve.

Obviously it wouldn't make much sense to put a piston-engined aircraft on such a device.  Instead, how is horsepower measured for aviation piston engines?

Like anything else a Dynamometer is used except the engine is bolted directly to it (most likely on a test bench). In a car a rolling road is simply a way to couple the tires to the dyno without having to have any custom fittings. For what its worth cars lose a bit of horse power in the transmission/drive shaft/differential so shaft horse power and wheel horsepower are not always the same. However in a plane the prop is bolted more or less to the end of the crank (with the exception of some planes with stepper gear boxes). In any case shaft horsepower on a plane engine is more or less whats available at the prop.

Here is a lycoming engine on a dyno

(source)


What modifications are necessary to the airframe and or instrument panel to add an autopilot to a light airplane (like a Cessna 172 or 182)? If you were going to add an autopilot to a light airplane that never had one, what all needs to be done? I know they need to connect servos somewhere (where exactly), and add instrumentation to the panel, but how invasive is the installation?

I participated in a project to do this to a light aircraft some time ago. The requirements will vary on the basis of the type of autopilot you select and the requirements of the STC that comes with it, and which allows it to be installed on your aircraft. There might (and likely will be) one or more of the following requirements: panel mods, electrical mods, servos need to be installed (type, placement and installation procedure as per the STC), there will also have to be ground and flight testing, and if you intend to interface the unit to navigation equipment, then it gets really interesting. It all depends what other avionics you already have in your aircraft. You may or may not have to upgrade your existing equipment to achieve that.

To get a complete answer to your question for a specific aircraft you need to go to a reputable avionics shop that has done the work before (read: has references) and pose the question to them.

You should also expect to have to pay for a detailed quote and time estimate -- it takes quite a bit of work to prepare that, and avionics shop owners have to pay bills and put food on the table, just like you. :)


Why do NOTAMs consist of code instead of plain language? I'm currently getting thru a PPL course book and I don't understand this. Is there any purpose of sending NOTAMs in this format:

"RWY 08R/26L DUE WIP NO CENTRELINE, TDZ OR SALS LIGHTING AVBL"

instead of plain language

"For runway 08/26, due to work in progress, there is no centreline, touchdown zone or simple approach lighting available"

Why do they force pilots to learn common ICAO abbreviations when they could simply send the text message without encoding it? The same questions goes for TAFs and METARs.

The NOTAM format is from the time when people still would call the value of individual bits over a phone line.

Ok, that may not have happened, but my point is that data transfer was incredibly slow compared to current day standards. Therefore a compact format saved significant  transmission time and cost without losing any information. The format didn't change since.


How to avoid getting trapped on top VFR? This question addresses whether it is legal to fly VFR over-the-top.

One of the comments mentioned the difference between safety and legality, i.e. doing so may not be safe even if it is legal (in some places, for some pilots). The most obvious concern would be whether a VFR-only pilot could find a hole in the clouds to descend for landing. (There may be others.)

How exactly does one mitigate this risk to an acceptable level? Or is it generally accepted that, even though regulations don't say so, that it should only be done by pilots with an instrument rating?

By regulation you just have to be sure that the conditions at destination allow you to maintain VFR clearance from cloud for your descent.  Pretty much all you have to go on is the TAF for the area of your destination.  If there isn't a TAF for an airport within say 20 or 30 miles from destination that would be a problem for me.

Assuming a TAF is available, you technically could go if the forecast was for broken cloud below you, hoping for a large enough hole to get down (basically a hole at least 4000 feet across, with you in the middle of it).  But that's taking a bit of a risk.

It would be imprudent to go with anything more than scattered cloud in the TAF at any level below you at the time of your planned arrival.  And even scattered cloud in late afternoon is pushing it.  On top of that you are continuously monitoring the METAR at destination for detrimental changes, and you also have a planned alternate that has better forecast conditions than your destination.

One of the more important factors to keep in mind on a trip like that is the temperature/dew point spread at destination (which will determine the cloud base if there is enough humidity), and the time of day.  When I was bush flying in Northern Ontario many many years ago, with many hours spent scud running under low cloud, the dew point spread was the most important bit of weather information and a tighter spread was more acceptable in the morning than in the afternoon.

A morning trip, with a decent temp/dew point spread that makes unexpected cloud formation below your level unlikely with temperatures naturally destined to increase until early afternoon, is lot safer than an afternoon trip where the spread will be decreasing and more-than-forecast cloud formation at a level below you is more likely.

Personally, I would never do VFROTT because I'd be biting my nails the whole time worrying about the engine quitting (I've had a mechanical engine failure) and being forced to descend through a cloud layer and then trying to find a landing area underneath it, if there was a decent ceiling.

And there's the rub; you not only have to come up with good weather margins, you have to have iron clad confidence in your engine if you're doing it in a single (which lots of single-engine IFR pilots do - me not so much).


How to reduce the landing roll distance If I want reduce the landing roll distance, for example to clear the runway at the nearest exit, I was told by some instructors that to increase the drag using following methods:

Pull up and hold the elevator at the upper extreme position.

Question 1: does that mean I should try to keep the nose wheel in air as long as possible?Is there any risk I leave the ground again due to aggressive pitch? Will there be any effect after all the wheels touched the ground, like keep the elevator up can increase the friction of the main wheels?

Retract flap to reduce the lift to create more frictions.

Questions 2: when flap is retracted, I will have less lift so more friction force could be induced but does that mean the aircraft is in a cleaner config, so the drag is also reduced?

1) This does mean you should keep the nose up as long as possible, increasing the angle of attack when you are behind the drag curve increases the drag the wing produces and uses the elevator as a spoiler in effect. If you have done a full stall landing pulling up cannot get you back into the air, but if you land with extra speed pulling up could mean you start flying again, so you should only use this technique if you are sure you have a low enough airspeed. Good technique is not to yank the stick back, you pull it back while paying attention to the "feel" of the airplane, if it seems to want to fly again ease off on the back pressure.

2) Retracting flap after landing decreases lift and puts more weight on the wheels, making the wheel brakes more effective. It does decrease drag, however your wheel brakes are much more effective at slowing the airplane than drag from the flaps.


Is drag higher when flying in a crosswind? Is this true that during a flight with a crosswind the drag increases due to the fact that the relative wind blows at a certain angle to the aircraft's nose but not precisely in the opposite direction to its flight path as it would be without a crosswind?

No, it's not true-- have you ever seen a birds feather's blowing sideways?

We fly INSIDE of the wind, not AGAINST the wind.

You should draw the airplane symbol on the left-hand leg of the triangle, pointing in the same direction as the left-hand leg, and you should draw the "relative wind" arrow equal in magnitude and opposite in direction to the airspeed vector, i.e. the left-hand leg of the triangle.

Consider the fact that many of us have had the experience of actually BACKING UP in flight, relative to the ground.  Now, do you think the air was flowing backwards over the wings?


Why did this aircraft re-route? I was looking through my ADSB Virtual Radar outputs couple days ago and saw a weird re-route for one of the aircraft that looked out of place.

Can one of the pilots/ATC guys pitch in to help me understand what may have caused this A/C to do this?  Is this "normal"?

I would expect if this was a wake turbulence from A/C ahead they would have just asked the rerouting A/C to just slow down?

Tail #: N39463

Its hard to tell from the picture, but assuming you are talking about the yellow airplane and the "wiggle" in the course, that was probably just an S-turn for spacing.  Sometimes the controllers don't get the spacing exactly right, or one airplane slows down early and messes things up.  In those cases, in visual conditions,  the controller can ask the following airplane to make an S-turn.  This causes the plane to take a bit more time to cover the same distance as flying straight and spaces the planes out.

This may be used instead of a speed assignment for a number of reasons

Planes on approach may not be able to slow down further as configured
There may already be a speed assignment but it wasn't enough
Slowing down takes time, and S turn may be more efficient.

An ATC instruction may assign a heading and follow up with a new heading and approach clearance or other instructions to join final, or they may simply ask for an "S turn to the right for spacing".  The vectors would be more likely in instrument conditions and the S-turn more likely in visual conditions.


What is this white smoke like thing, seen inside the cabin before takeoff? I saw this quite thick white smoke like thing in the cabin in my last flight, before takeoff that is, while it was taxiing and loading passengers:

Video
Please watch in HD to best notice the phenomenon.

It seems to be coming from the AC vents of aircraft. I think it's a quite common phenomenon as the cabin crew didn't even pay any attention to this.
But I saw it for the first time. What is this?

Aircraft Details : VT-IDE (A 3.5 year old A320)

The departure location was Bhubaneshwar and the approximate weather was:
Temperature : 28 °C
Humidity ~ 85%
Clear Sky, good visibility

Direct answer
Air conditioning causes a large drop in cabin temperature, air humidity present in the air condensates into water droplets. It is similar to mist, fog and clouds. If water droplets enter in contact with a solid they form dew and moisture. Accurately, it is an aerosol of water droplets.
Water droplets appear in air when air temperature is lowered below its dew point (see further down). This phenomenon is exactly the same than when a freezer is opened and air over the freezer is in contact with cold air from the freezer tank:

Marcellus ̶̶̶̶̶̶̶̶ freezer. Source.
Quick explanation
In your case, before air conditioning is started the cabin is filled with air from the outside, which happens to be warm and nearly saturated in water vapor. The ambient temperature is close to the dew point. The injection of colder conditioned air in the cabin decreases the temperature around the AC vents (inlet air on the picture below):

Air circulation in large pressurized aircraft, from this answer
The temperature quickly goes below the dew point causing invisible gas (water vapor) condensation into visible liquid water droplets (fog).
Due to the limited instantaneous capacity of the air conditioning system, the temperature is decreased only around the AC vents, not in the whole cabin. When the water droplets mix with the warmer air in the rest of the cabin, they immediately return to the gaseous form (vapor), and doing this they also make this air a bit colder (evaporative cooling).
As pointed out by @JanHudec the humidity level must be kept low during the flight to prevent structure oxidation. Humid air from the cabin returns through the decompression panels to the air conditioning system where it is mixed with dryer air from the packs. After some cycles the cabin air is rather dry and condensation doesn't occur anymore.
Another case of condensation:

Detailed explanation
Why does water vapor condense?
The quantity of water vapor in air is named water saturation ratio (or relative humidity) and is expressed as a percentage: 0% for dry air, 100% for air fully saturated. Saturated air cannot contain more water vapor. If vapor is added then it immediately condenses into visible water droplets.
Saturation occurs at certain combinations of temperature and pressure. For a given pressure, the higher the temperature, the larger the quantity of vapor than can be present without condensation. So condensation can occur when the temperature decreases.
Psychrometrics, the branch of physics studying how liquids and solids boil or condense, revolves around the notion of equilibrium vapor pressure, but for us mere mortals, the notion of dew point is more practical.
Dew point
The quantity of vapor air can contain before being saturated is called its water vapor capacity, it increases exponentially with temperature:

(Source)
Let's define two cases:

Full saturation: If the quantity of vapor is the maximum allowed for the current temperature (100% relative humidity), decreasing the temperature or adding vapor will cause some vapor to condensate into water.

Partial saturation: If air is not fully saturated, there is a (lower) temperature for which it becomes saturated. This temperature is referred to as dew point. So whatever the current temperature, fog can be created by decreasing the temperature until the dew point is reached.

For sake of accuracy: When water vapor is present in air, it is continuously condensed and evaporated. The dew point is the point where condensation occurs at a greater rate than evaporation and water droplets start accumulating.
Whether fog will form depends on the the dew point spread, that is the difference between current temperature and dew point. When the spread is large, the change in humidity or in temperature must be large. In your case, the spread is small, because air is wet and temperature is high.
Bhubaneshwar case
Before air conditioning system is started, cabin air is the same than at the airport: 28°C and 85% humidity. AC is going to inject air at 20°:

Quantity of vapor for 85% RH at 28°C is 23g per kg (85% * 27).
Vapor capacity at 20°: 17g per kg.

When air is injected and temperature is decreased to 20° around the vents, air becomes fully saturated, and the 6g of vapor in excess per kg of air are condensed into fog.

Cabin air relative humidity and AC fog
This air returns to the AC system, and is mixed with air from packs which condition air entering the cabin at the 20% RH targeted for the flight. The 13.6g/kg of vapor in excess (for 20% RH) are progressively extracted by outflow valves, which regulate pressure in the cabin by releasing overboard as much air as packs push in. After some cycles, air contains only 3.4g/kg of vapor (the cycle is simplified, actually we would also account for passengers perspiration and breathing, fog re-vaporization and AC air humidity)
For typical cabin of 150m3 containing about 175 kg of air, 3.5 kg of water are extracted.
Fog in the aircraft is indeed a problem, fog outside the aircraft is another one as visibility is strongly impeded. It requires flying using Instrument Flying Rules (IFR). IFR is allowed only with a specific pilot rating and aviation certification. Knowing the dew point is important to plan a flight, in particular to know whether IFR will be required. Therefore the dew point is measured and published as aeronautical information.
Measuring the dew point
The dew point may be determined with a psychrometer (a system with dry and wet thermometers):

Whirling (how to use it) and digital psychrometers
Pressure, dry and wet temperatures, dew point and relative humidity are linked by the mean of vapor pressure. By knowing three elements, the two other can be determined. So knowing pressure, dry temperature and wet temperature allows to determine the dew point. It exists precalculated charts (Mollier diagrams) to read dew point directly. There are also online calculators.
Here is a vertical profile of the temperature and moisture information (emagram) collected by a radiosonde in Ireland:

Emagram from Valentia Observatory (Ireland). Source meteociel.fr
The vertical scale is the pressure (hPa on the left, equivalent altitude on the right) and temperature is on an oblique scale, with the quantity of water at saturation for this temperature. The dry temperature is shown in read, the wet temperature in blue, and the computed dew point in cyan. When the dew point curve is close to the temperature, moisture is hight (%RH on altitude scale) and cloud/fog can occur (like under 1,600 m for this example).
Dew point and fog/mist information
KLAX ASOS report:

As previously mentioned, when the dew point is close to the ambient temperature and the humidity percentage is high, the visibility is low and fog occurs.
Common examples of condensation

Frost around the freezer pipes: Air with water vapor enter the fridge when the door is open. When air starts to be cooled below the dew point by the pipes, condensation occurs and ice forms around them.

Air exhaled when the weather is cold. Air in our lungs is not saturated due to the high body temperature, but becomes saturated when it starts cooling.

Air saturated by water vapor coming from a pressure cooker.

As pointed out by @RyanMortensen, saturated air on car windows (when the temperature decreases during the night, or when air is saturated without temperature change, because there is more water/rain in the air that can be evaporated naturally -- Increasing car temperature above the dew point is the solution).

Fog and clouds formation: Fog because the ground is colder than the surrounding atmosphere (early in the morning), cloud because air is cooled below the dew point while it climbs (pressure and suddenness play also a role).

Dew :-)

When water vapor changes into ice
When the dew point is below 0°C, water vapor is not condensing into water droplets, it is converted directly into ice crystals (frost).
This effect is particularly dangerous and can lead to icing in the carburetor of a piston engine. This condition can happen in areas of low pressure and low temperature, commonly created by the sudden pressure drop in the throttle venturi, due to venturi effect and the temperature drop due to fuel vaporization.
For a typical piston engine, this effect is centered on a external temperature around 10°C but extends to a large range of temperature when the engine is slowed down (descent):

Induction icing conditions
The remedy to carburetor induction icing is to heat the carburetor and raise the due point to a safe area, especially when descending.
For jet engines, induction icing (not to be confused with flying in atmosphere with ice crystals or supercooled water droplets) can cause ice to form at the engine inlet. Blocks of ice can then break, causing damage to blades, compressor stall and/or combustor flameout. It can also cause EPR probe (PT2) reading errors and subsequent FADEC fatal behavior.


Why does elevator dropdown occur in some loss-of-flight-controls accidents, but not others? In some instances of an aircraft suffering a catastrophic failure of its primary flight controls, the loss of control force on the elevator allows said elevator to drop down under its own weight, causing an immediate crash.

Examples:

THY 981 (DC-10, 1974, Paris)
LOT 007 (Il-62, 1980, Warsaw)

In other loss-of-flight-controls accidents, however, the elevator either stays stuck at its position immediately prior to the control failure, or floats in the airstream:

JAL 123 (B747, 1985, Mt. Takamagahara)
LOT 5055 (Il-62, 1987, Warsaw)
UAL 232 (DC-10, 1989, Iowa)
DHL OO-DLL (A300, 2003, Baghdad)

Why does elevator dropdown occur during some, and only some, loss-of-flight-controls accidents?

The mechanical or hydromechanical control system transmits the forces both ways, potentially amplified in the later case. When the pilot trims the plane so he is not applying any force on the control column, all the forces on the elevator are balanced and this includes gravity.

So when the control links are broken, the elevator will return to its trimmed position. In that condition, the plane will maintain speed with pitch, oscillating around the equilibrium in a Phugoid oscillation.

In the later four cases, the planes were likely trimmed, and had engine power left, so they remained controllable for some time.

In the LOT 007 case the aircraft was almost certainly not trimmed – the pilot could just hold the control column and not bother with the trim – and it lost most power, so it pitched down immediately.

The THY 981 either for some reason was not trimmed, or maybe the stabilizer moved a bit as the control links severed. I don't think there is enough information to tell for sure.

Also in the LOT 5055 case it is not clear the plane did not initially pitch down as the trim was still operating (until the spreading fire burned the power supply to it) and they had enough altitude to regain control by using it.


What kind of input is used by NASA's TASAR? I've found the Aviation SE to be a really interesting read so far, I'm excited to be here! I'm fairly new, but I'm also old!

What are the inputs for TASAR to crunch flight path optimization? Is it taking a look at the aircraft performance model, wind and weather, and ADS-B IN? Maybe TCAS-II traffic info? Would the weather data come from the onboard WXRadar or ground data?

I've read a few data-points that the long range weather info pilots tend to use is from received data (maybe ground radar or sat based weather data? both?), but the data is delayed to the point of being less useful, would the weather data need to take inputs from both Weather RADAR and NEXRAD type inputs?

The answer is "All of the above." The left hand side of this slide from a NASA Powerpoint deck pretty much covers your question.

The full slide deck from the presentation can be seen here.


Using pure O2 for jet engine combustion In addition to my previous question, I am mainly concerned with burning all the fuel.

Why isn't the combustion process using all of the Oxygen in the air?
Is it because other gases are in the way and it isn't in the right place to help the reaction?
Are engineers limiting the amount of fuel into the process because they know some of the Oxygen won't be available for combustion due to its proximity(lack thereof) to the fuel?
How much fuel remains un-burnt in a modern jet engine?
I thought that an after-burner was meant to use the fuel that somehow got through the whole process without combusting?
Wouldn't using pure O2 allow for a complete fuel burn?
I do get that the added weight may not make it worthwhile since we need to weigh the value of complete burn against other non-monetary concerns(like pollution).

Finally, I assume the 2000-2500 degree C temp mentioned (in this answer) in the last post is to actually burn Oxygen. Although I know Oxygen is not flammable, I am sure everything does burn at some point. I do not want to actually burn the Oxygen.

The compression in the forward part of a jet engine heats the air, and combustion raises its temperature again. In order to achieve efficient operation, this heating must be restricted. If air is heated above approx. 2,000 K, adding more energy will result in dissociation of the gas with less further heat increase. Since thrust is produced by expanding air through heating, raising combustion temperatures above 2,000 K will result in less thrust increase for the amount of fuel consumed. The most advanced engines (F-119 and EJ-200) have turbine entry temperatures of 1800 K, and civilian engines operate a few 100 K below that. The number of 2000 - 2500°C (2300 - 2800 K) you got from a previous answer is way too high.

Oxygen starts to dissociate already between 2,000  and 4,000 K, depending on pressure, while Nitrogen will dissociate mainly above 8,000 K. The 2,000 K figure above is a soft limit, but this temperature is also a challenge for the materials of the combustion chamber and the turbine, and techniques like film cooling are mandatory. As you can see, using pure oxygen would greatly increase the efficiency loss due to dissociation once technology allows to run the turbine at higher temperatures than 1800 K. It would be better for jet engines if air had a lower oxygen content.

To make the best use of the fuel, much more air than would be needed for stochiometric combustion is used in a modern turbojet or turbofan core. The idea is to heat the gas just as much as technically and economically possible.

Too much oxygen does create problems, mainly by raising the amount of nitrous oxides a jet engine produces. However, it helps to achieve largely complete combustion, even if some of the reaction happens not in the combustor, but at later stages. Combustion is never fully complete, and the remaining unburnt constituents are proportional to an inverse exponential function over time.


Why evacuate upwind? Evacuation procedures after a forced landing recommend directing passengers upwind of the aircraft.

What is the reason why evacuating upwind is better than other directions?

There are two problems linked to the wind after accidents:

Inflating the slides.
Running away from the aircraft when on the ground

@DavidRicherby listed the reasons related to running away upwind to try to avoid the effects of flames and fumes (visibility, heat, toxicity). This is part of the IATA guidelines for post-evacuation:

  Post-evacuation. Once outside the aircraft, the cabin crew is
  responsible for the passengers until relieved by the authorities or
  emergency services. Until this help arrives, the cabin crew should:
  - Direct passengers upwind and away from the aircraft;
  - Assemble passengers;
  - Direct passengers away from fuel, fire and vehicles;

Source

While it appears running upwind is a good choice, deploying slides upwind has not always been a good idea.

A study was conducted by the National Aerospace Laboratory (NLR) in Netherlands, about slides issues during evacuation. It was published by the Flight Safety Foundation in 2005:

Analysis of Evacuation-slide Problems
Calls Attention to Recurrent Issues

The scope of the search was the period 1970–2003 and covered aircraft operations worldwide. NLR researchers identified 150 accidents in which slides were used. A total of 89 slide problems were identified:

One problem was slides not inflating due to the wind:

  Wind had an adverse effect on the use of slides in 11 slide problems
  (12.4 percent) analyzed by NLR researchers. Typically, wind blew the
  slide against the side of the aircraft, preventing its use.

To allow using the upwind side of the cabin for slide deployment, today, aircraft certification include this requirement for slides:

  4.20 Wind. The device must be shown, in 25-knot winds directed from the most critical angle, to deploy and, with the assistance of only
  one person who has evacuated down the device, to remain usable after
  full deployment to evacuate occupants safely to the ground.

Source

See also:

IATA - Cabin Operations Safety - Best Practices Guide
EASA ETSO-C69, Emergency evacuation slides, ramps, ramp/slides, and slide/rafts


Why are these carrier aircraft landing with the canopy open? I was reading this answer here Aviation.SE, which includes the following video of multiple F7U-3 Cutlasses landing aboard the USS Hancock in 1955 (warning, video includes footage of a fatal rampstrike):

I notice that each and every pilot is landing with the canopy open. Why is this?

I'm not a pilot, so these are uneducated guesses:

It could be opened for visibility reasons, except I'm guessing it'd be forward visibility that's be most important, and the sliding canopy doesn't do that any obvious favors. And according to Wikipedia, the plane's high cockpit was already designed for good visibility for carrier landings.

My other guess would be that the canopy is opened in case of a bad landing/fire (less bad than the rampstrike later in the video), and the pilot has to get out in a hurry. But I doubt it'd make a huge difference as the pilot's (presumably) still strapped in. And if he can open the canopy while on approach to a carrier landing, it's probably fairly straightforward.

Last guess would be that it's in case the pilot has to eject, yet he should be able to do that, open canopy or no. Besides, the seat would still hit the canopy upon ejection, it seems - maybe just-in-case to avoid the pilot's head hitting first?

Because it is the standard operating procedure, not only for this aircraft, but also for others. In the book U.S. Naval Air Superiority: Development of Shipborne Jet Fighters - 1943-1962, [Tommy H. Thomason notes](By Tommy H. Thomason):

  Leaving the canopy open for landings and takeoffs would still be standard for many years as it facilitated egress in the event of a water landing.

Here's the Grumman F9F Panther, one of Navy's first jet fighters landing with its canopy open:

Grumman F9F-5 Panther, Bu. No. 126034, of VF-781, catches an arresting cable when landing aboard USS Oriskany (CVA-34), 15 November 1952. (U.S. Navy); image from thisdayinaviation.com

This followed through the time of Cutlass, as thanlont.blogspot.in notes:

  The ... F7U pilots all have their canopies open for landing. Although open canopies for carrier takeoffs and landings had been standard since canopies were introduced, this became pilot's choice on straight-deck carriers at some point following the addition of the barricade ... after an incident or two when the upper strap of the barricade went into the cockpit of a crashing jet. Note that the FJ-3s are taking off with open canopies.


When an airliner gets lost, and receives warning shots from interceptors, how should the pilots react in order to save the aircraft? In 1983 KAL007 was shot down by the Soviets, as it got lost due to navigational errors and entered restricted airspace. The Soviet interceptors reportedly fired warning shots "which were likely not seen by the KAL pilots", and after then they proceeded to destroy the airliner with an air to air missile.

So, let's suppose you are flying a commercial flight, when a military aircraft catches up to you. If your communication equipment wasn't malfunctioning, you would have already gotten demands to change course and you could have identified yourself, answered that you will comply, and could more easily avert the problem. For this case, let's suppose your comms are down due to technical problems.

You then see you are fired upon (how? smoke trails of a missile flying by? Tracers from guns whizzing past?). It is only then when you realize you got intercepted, and you suddenly realize they just fired warning shots at you.

What now? How could you maximize your chances of survival? I would guess you have to indicate surrender, that you will comply to any instructions, and that you mean no ill will. How can you do that without a working radio? If you just entered a country's territory, the most obvious way would be to change course to the shortest path leading out of that territory, but if you are deep inside, or you are lost, you might choose the wrong heading and make the problem even worse.

Is there a custom how a civilian aircraft can indicate "I yield, please don't shoot me, I will follow your orders!"? And, lastly, how would it differ between the incident happening in 1983 versus 2019?

First off there are established interception procedures under international law so they are not going to shoot at you upon overtaking you.  Typically an element of fighters form up on the jet with the leader maneuvering into formation on the jets 9 O’Clock and the Wingman stays on the jet’s six.  They will do so in a manner which allows the intercepted aircraft to see the lead fighter.  There are a series of established visual signals ie rocking wings for compliance, deploying flaps and landing gear, etc.  if the intercepted aircraft cannot communicate with the fighters or ATC, they will squak 7600 and ATC can relay this to the fighters.  Other means can be employed to get the attention of the intercepted aircraft such as the lead fighter cutting in front of the intercepted aircraft while in afterburner, etc.

If it does come down to where the authorities determine you are a threat and use of deadly force becomes authorized, the fighters are going to let you know in a clear and unmistakable way.  Unless you are armed and intend to engage, you better comply!


Was the 727 the last airliner whose doors could be opened in flight? The Boeing 727, put into service in 1963, had the distinction of a rear doorway with stairs that could be lowered so that passengers could embark and disembark at rural airports which did not have their own airstairs.  As initially designed, this door could be opened even whilst in flight as it is not the usual "plug" style.

In 1971, the hijacker known as DB Cooper famously used the rear door to make his parachute escape mid-flight. According to wikipedia, the CIA also used this feature to drop passengers and supplies mid-flight.

In the wake of the DB Cooper incident and other hijackings, the FAA mandated in 1972 that cooper vanes to be installed to prevent the opening of the rear door while in flight.

Does this make the pre-cooper 727 the last passenger airliner which had a door (either passenger or cargo) that could be normally opened while in flight without depressurizing the entire cabin?

Small Print: There was a rear cabin, pressurized bulkhead door on the 727 that you had to transit through to get access to the ventral stairways which was in the aft, unpressurized bulkhead. The actual ventral stair door itself was not a "plug" style. Thus the ventral stairways meets the requirement of being able to open in flight (even if you couldn't get there because the rear cabin bulkhead door might not open).

Animated image from wikipedia and cc.

The door of an airplane can be opened in any of the aircraft only when the airplane is depressurized. When an airplane is pressurized, the extra pressure inside the hull of the plane forces the door outwards which in turn presses on a seal and hence, to open a door in such a configuration, where 6 p.s.i. (pounds per square inch) of pressure is acting against several square feet of the door, one would need a tremendous amount of force, and even if the door was to be opened electronically or hydraulically, one would still expect rapid decompression of the cabin after opening the door.

Hence it is categorically incorrect to claim that modern (new) airplanes can't open their doors mid flight. It is quite achievable, but after depressurizing the cabin. Here is a source for your further reading.

Edit

The following airplanes have Air-Stair installed. I'm not sure which of them has an over-ride to open this Air-Stair mid-air, but any airplane which does not have a cooper vane installed (Or any other external barrier) can open the Air-Stair midair (technically):

Lockheed L1011

Boeing VC 25

Ilyushin Il-86

DC-9/MD-80/MD-90/B-717

Boeing 737

Some modified Airbus and Boeing planes have Air-Stairs too.