Is it correct that a jet fighter can be used as a non-lethal (sonic) weapon?

Sonic booms from low flying aircraft, while loud, don't seem to cause hearing damage, as this F-14 pilot demonstrates during a Tiger Cruise air wing demonstration.

Now military fighters will sometimes make a 'show of force' in the form of a low altitude, high speed pass against threat forces which don't have a substantial IADS capability in order to motivate them to disperse under threat of employing ordanance on them if they continue belligerence.

UPDATE:  I found this story about an F-16 2-ship over Iraq on a CAS patrol mission.  The pilots get a radio call from desperate SOCOM operators pinned down by enemy troops at night.  The pilots cannot get a IR strobe to track for bombing, so the lead Viper uses a sonic boom delivered from a dive to frighten off the combatants.


Why $\frac{\Delta p}{\overline q}$ is depending by weight, flap deflection and other parameters? Which are other parameters?

The formulas deal with the relationshop between calibrated airspeed and indicated airspeed. The difference is due to two factors:

instrument errors: these errors occur within the airspeed indicator instrument when transforming the pitot pressure to a speed indication.
position errors: these errors are caused by the position of the pitot tube on the airframe causing the pitot pressure from being different than the freestream pitot pressure.

Since the pitot tube is usually close to the fuselage of the aircraft, the local airflow around the pitot tube is influenced by the aerodynamic properties of the aircraft itselfs. The pitot tube's location is chosen such the the local flow characteristics deviate as little as possible from the freestream characteristics but there will be a measurable difference in pressure between the freestream total pressure and the pitot pressure. The pressure differences depends on airflow around the aircraft which is infuenced by the angle of attack (and thus weight) flaps, slats, gear, turn rate, side slip angle etc.

In order to analyse the position errors during a flight test programme, test aircraft are often fitted with additional pitot probes protruding ahead the airframe and/or trailing cones (for static pressure measurement) far behind the aircraft.


Is there any alternative to isolating the vibration of an ultralight engine other than using engine mounts?

You can prevent engine vibrations from being transmitted to the airframe by motion cancellation techniques. Similar in principle to Active Noise Reduction headsets that generate an inverse pressure wave to cancel sound, motion cancellation generates an inverse displacement of a mass to cancel vibrations.

Sensors determine the vector(s) required, and electronics control the mass actuator(s). These can be added to any engine. Predictable, repetitive vibrations are most successfully treated. Actuators tend to be heavy, so better engine/prop balance and more effective isolators (mounts) are preferred.


Why don't all pilots receive at least basic instrument training?

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

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

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

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

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


What is the Boeing 727 AC Generator Panel Part Number?

The part number is 69-17528-XX, where XX (the dash number) varies based on customer preferences and when the aircraft was produced. Without knowing specifically about the particular airplane the module came from, there is no way to know the part's dash number without physically examining it. See the image below from a search of Icon Aerospace's capability list. Directly searching the capabilities lists of FAA/EASA-licensed repair stations usually yields more reliable results than searching parts "aggregator" or "locator" sites. For example, this list links the part number specifically to a 727.


Which was the last Boeing crash that didn't send its black boxes back to the US?

Please refer to the following website for more details

https://slate.com/technology/2019/03/ethiopian-airlines-737-max-black-box-sent-to-paris-why.html

The International Civil Aviation Organization, which sets the standards for aircraft accident investigations, says that the country where an incident occurs is in charge of the investigation

If the concerned country has the tool to analyse the black boxes, they are analyzed locally and if necessary with the help of the aircraft manufacturer, therefore

When the concerned country has the knowledge to do the analysis there is no point to send the boxes to the manufacturer country.  What is particular to the Ethiopian case is that even though not having the tools to do the Analysis they preferred the help of a third party, rather than sending the boxes to the US, but this is beyond the scope of the question.

So the Ethiopian government asked Germany to analyze the black boxes, but according to CBS, the Germans also lacked the necessary software, consequently Ethiopia asked the help of France, thus the boxes have been sent to the Bureau of Enquiry and Analysis, the BEA.


How to correct a roll due to turbulence?

Your instructor needs some... instruction.  Inducing roll using rudder alone is something you do when you are right on the edge of a stall because a downgoing aileron can potentially induce a stall when right on the edge.   In a normal climb, using rudder alone is totally nuts.

Apply only the rudder required to keep the ball centered with the application of whatever aileron is necessary.   If you needed all the roll power you can possibly get, you would apply full aileron and full rudder to use the resulting skidding to increase the roll rate.


Would discharging a firearm in-flight cause an explosive decompression?

No, there was actually an episode of Myth Busters about this exact subject:

http://www.youtube.com/watch?v=Fi1_1l7M8FA

They had to try really, really hard to cause an explosive decompression, resorting to actual hollywood style explosives to make it happen.

Most airliners can actually even maintain normal pressurization even with a coffee can sized hole in the fuselage.

As far as firing their weapon on board the aircraft, they are trained to not shoot towards areas like the cockpit or the floor where most of the "important" stuff is.  Avionics, hydraulic lines, electrical wiring, etc. don't take bullets well.  The rounds that they use would put holes in the aircraft, but as the above episode shows it won't create a pressurization problem.


Is there a physical argument for the Kutta-Joukowski theorem?

The question as asked in the title is one of the great debates of the discipline of aerodynamics (and you can see by the number of times I've edited this answer that it's still bouncing around in my own head). If you've gotten this far in Anderson and are making this kind of inquiry, you must read McClean. The first 300-or-so pages are devoted basically to answering this very question. Basically: Yes, there is a physical argument (see Peter Kämpf's answer and Anderson 4.5), but saying that lift is caused by circulation is too much of a stretch (which Anderson notes in section 3.16).

Let me turn to your specific example.
Unfortunately, I think Anderson is trying to force the mathematics into the physics rather than start with the physics and describe why the mathematics is a good representation (as McClean sets out to do from the beginning). "Make this physical argument by drawing a closed curve around the body..." basically tells us to make a physical argument by first using a mathematical construction, which to me doesn't actually shed any light on the physics. Further, then we're supposed to be thinking about infinite distances (not physically useful), a "speck on a page" (which has nothing to do with airflow), and really just make use of $\Gamma$ (which is defined purely mathematically) rather than describe a physical flowfield. In short, the closest thing to a "physical" argument here is saying more or less that any two things look the same when viewed from far enough away. This explanation does not seem convincing to me. If you put lots of little vortices around the profile of a cow then reduce it to a "speck on the page," will the cow generate the same lift as an airfoil? To get at the physical generation of lift, we need to remain close to the lifting bodies and determine why their specific geometries create flowfields that produce lift. (Consider, for example, why we need a Kutta condition on an airfoil but not on a cylinder.)

Actually, the mathematical proof (based on conformal mapping) uses the same basic "physical" argument that Anderson makes. Conformal mapping tends to be more of a graduate-level topic, though, so beware of feeling like you need to understand all the underlying math at this point.

In summary, Anderson does not do a good job here of explaining physically why the airfoil has the same lift as the cylinder. If you truly want to understand the physics, read McClean. Anderson's "physical" argument is really just a boiled-down mathematical one.


Does a pilot have to request altitude changes when receiving flight following?

No, you wouldn't need to advise of changes if all that they instruct is "maintain VFR."

  91.123(b): "... no person may operate an aircraft contrary to an ATC instruction in an area in which air traffic control is exercised."

It would depend on the instruction received.  Let's say, after departing from class 'C' airspace, they told the pilot, "maintain VFR and resume own navigation," they are giving him freedom to choose his own headings and altitudes.

On the other hand, if the controller said, "maintain 5,500 and turn heading 030," then the pilot would need to cancel flight following or make a request to change instructions.

Bottom line: don't not do something they do tell you to do.


Attempting to determine whether a flight took place

That flight did indeed happen:

https://flightaware.com/live/flight/AAL2953/history/20190516/1632Z/KSAV/KORD

It was scheduled for 12:22PM, but actually left the gate at 1:43PM (about 1 hour and 20 minutes late).

It was scheduled to land at 1:28PM, but actually landed at 3:25PM (about 2 hour late).

It looks like it took an extended detour to Missouri to avoid a weather system, resulting in the extra delay.

While the flight was not canceled, it is possible that passengers were offered free re-booking opportunities due to the weather system.  Your house guests may have taken that on the belief the flight might be canceled.


Is it possible to ping ACARS repeatedly and track an aircraft?

When ACARS communicates via INMARSAT satellite (other options are VHF or HF to ground stations), the satellite can ping the receiver on the aircraft and determine the distance from the delay of the reply. The satellite is geostationary, meaning that it is a fixed point 35786 km above the earth. Based on the distance from the satellite you can calculate a circle where the aircraft must be on. This has been done for MH370.

Since the geostationary orbit is so high, a single satellite covers a large portion of the earth. Only a single satellite covered the MH370 flight.


Is the Fortran language still being used in aviation?

FORTRAN is not used much that I'm aware of in aviation, but it is significantly used in aeronautical engineering.  I work with people that use Mark Drela's 'xfoil', 'xrotor' and 'aswing' programs on a daily basis for the design and analysis of airfoils, propellers and aerostructures. And I've used the 'CHARM' model of rotorcraft dynamics.  All of these are written in FORTRAN and you often need to know the language to debug them or integrate them into other programs e.g. for global design optimization.


Do I need a PPL license for a CPL license?

Yes, with a couple of exceptions. FAR 61.123 contains the requirements for a commercial certificate, while 61.153 contains the requirements for an ATP certificate.

FAR 61.123(h) states than an applicant must:

  Hold at least a private pilot certificate issued under this part or meet the requirements of §61.73

FAR 61.73 refers to the option for military pilots to apply for an FAA certificate based on their military qualifications. For non-military pilots, the commercial certificate can only be earned after obtaining the private pilot certificate.

FAR 61.153(d) includes the ability to use a foreign commercial or ATP certificate as a prerequisite. An applicant must:

  Meet at least one of the following requirements:

  (1) Holds a commercial pilot certificate with an instrument rating issued under this part;

  (2) Meet the military experience requirements under §61.73 of this part to qualify for a commercial pilot certificate, and an instrument rating if the person is a rated military pilot or former rated military pilot of an Armed Force of the United States; or

  (3) Holds either a foreign airline transport pilot license with instrument privileges, or a foreign commercial pilot license with an instrument rating, that—

    (i) Was issued by a contracting State to the Convention on International Civil Aviation; and

    (ii) Contains no geographical limitations.


Does dihedral improve roll stability in gusty conditions?

Dihedral does not help roll stability to a side force gust.  Quite contrary, a gust will roll the plane into a slip, which then will turn the plane downwind (courtesy of your elevator turned rudder).
Firstly, I would not recommend setting a model plane with excessive "static stability" in windy conditions.  You want to be staticly stable, but not so much that a gust will pitch you up into a stall.  Higher wing loading also helps.
But roll stability from dihedral is good for cruising flight, but no match for a side gust, especially in a model.
What you must do to keep dihedral is to put side area below the CG.  This is known as "anhedralling".  Sea gulls lower their wingtips.  Cessna put the wing (and fuel) on top.  Consolidated built their famous PBY 3 Catalina with the engines on top too!  All 3 want to roll into the wind, not away.  This is the key.
A fourth design, the common paper airplane, does this with gusto.  The side "keel" balancing with the upraised wing around the center of gravity is best for cross wind roll stability.
So you may experiment by raising of lowering your CG, adding side area, and glide testing in a cross wind.  Your second model seems to have more of a chance.  You may try a shorter and more square vertical stabilizer, and a bit of weight (a coin or two) on top of the wing at the expected Center of Pressure.


Before answering the questions, let's try to see how simple is the notion of a geodesic. In planar construction, we use latices to rigidify a structure, e.g. a truss:

The structure is made of straight segments that don't deform when axial forces are applied. If we switch from the plane to an arbitrary curved surface, something similar can be done, but geodesics take the place of the straight lines (actually the line is the geodesic for the plane).

The idea behind a geodesic construction is that its rigidity is obtained from segments on the surface of the truss, and the inner volume is left empty and available for other uses.

What is the relation between geodesic airframe and geodesic curves?

Are geodesic frames related to geodesic curves? If yes, in what way?

Geodesic airframes are indeed constructions made of geodesics, a technique first applied to aviation by Barnes Wallis. From the Barnes Wallis Foundation, and article Geodetic Aircraft Design:

  A geodetic (or geodesic) airframe makes use of a space frame formed
  from a spirally crossing basket-weave of load-bearing members. By
  having the geodesic curves form two helices at right angles to one
  another, the members became mutually supporting in a manner that the
  torsional load on each cancels out that on the other. In addition to
  being comparatively light and strong, the fact that the geodetic
  structure was all in the outer part of the airframe meant that the
  centre was a large empty space, ready to take payload or fuel.

A close-up view of the geodetic structure designed by Barnes Wallis (source)

Vickers Wellington's under construction (source)

[The wikipedia article] does not seem to deal with  geodesic curves. It is mostly about about a structure made by triangles or other polygons

Geodesics are curved lines. Using 2 or 3 geodesics on a closed surface creates repetitive and symmetrical curved polygons, e.g. curved triangles and curved lozenges. Providing the supporting geodesics are angled so that "the torsional load on each cancels out that on the other", the resulting geometry belongs to the family of geodesic modeling.

Whether the actual construction is an approximation of the perfect model is a different engineering/costing problem. This is related to the actual cancellation of the torsional loads after approximation and the effect of the residual loads on the structure. This residual load could potentially be absorbed by additional engineering device if appropriate. This dome is made of straight segments only, the triangles are planar.

The geodesic dome at Amundsen Scott South Pole Station by Ernie Mastroianni (source)


Is this XKCD comic list about autogyro features accurate?

Flies like a plane.

To a certain extent in that the controls are plane-like, you do not have helicopter controls (no cyclic, etc.), but you also do not have wing control surfaces, so in some respects like a plane, but not exactly.

  Big blade on top is not powered.

True, the blades are unpowered; they rotate due to the wind. Some autogyros use power to rotate the blade to speed before take off, but the power is removed for flight.

  Never stalls.

You can put it into a stall attitude, but it self-corrects; it is basically a rotating parachute.The fatal mistake that pilots made with early autogyros was that when they entered stall conditions they instinctively pushed forward on the stick which resulted in the 'fuselage' tipping forward and the blades chopping off the tail. There have been a few fatalities this way.

  Sort of like a powered parachute.

Fairly good description. It is more like a powered paraglider than a helicopter or plane.

  Common in Europe (I'm fairly sure I've never seen one in the UK)

Maybe this should be more common in Europe. They are still uncommon in Europe, but they are more common in Europe than the US. Wallis Autogyros used to make them in the UK in the 1960s. Check out the Bond film "You Only Live Twice" for one in action (ignore the missiles, etc.; they are not standard fit on autogyros).

  Can often be flown without a licence.

Not in anyplace I have flown in Europe. The US may be different.


Would an Aero L-159 Alca air frame be able to withstand a supersonic engine?

By 'supersonic jet engine', I presume you mean an engine which would make an L-159 capable of supersonic flight.  Could you mount such an engine on this aircraft?  Possibly, but why would you want to?

An L-159 isn't exactly engineered to be a top of the line high performance fighter; its design and intended use is as an advanced subsonic trainer aircraft based upon the earlier L-39 and L-59 airframes.  Its job is to prepare student pilots for more advanced tactical aircraft and has handling qualities similar to fighters while retaining forgiving flight characteristics for new students so they can more easily build time and experience in high performance jets.  In addition, the aircraft is designed to be affordable and easy to maintain for third world air forces.  Supersonic flight never was considered as a requirement for the role by Aero Vodochody.  Therefore a much more expensive and exotic engine is not needed here.


What does the solid black star symbol on this VNC chart mean?

Here's how to decode S2 Fl R 209:

S1 - Identifier. Bearing relative to an aerodrome (N, W, NE). If there are multiple with the same bearing, they are numbered

Fl - Light pattern

R - Color

209 - Elevation

Source


Is it legal to land in bad visibility conditions without ILS?

The answer is "Maybe".

An ILS is actually comprised of two signals - a localizer (which lines you up with the runway) and a glideslope (which guides your vertical descent).
If the glideslope is out of service (as it was when KAL801 was flying its approach) you fly a localizer-only approach, which requires visual contact with the runway at a higher altitude.
In this case as shown on the plate below the ILS can be flown down to 531 feet (in red); the Localizer-Only approach can only be flown down to 1440 feet (in green).

So as long as the crew had the minimum visibility and cloud height requirements (and observed the altitude restrictions on the approach) they could legally fly into the airport on a localizer-only approach

In the case of KAL801 there were a few contributing factors to the accident (go ahead and skip to page 142, unless you really like reading NTSB reports):

The glideslope may have been receiving false signals.
The crew should have disregarded the glideslope indication anyway as it was NOTAM'd out of service, but it's possible the crew followed the needle anyway.
The DME fix for the approach is not located at the airport.
This may have caused the crew to believe they were closer to the airport than they actually were.
Because of (1), (2), or some other reason, the crew flew below the Localizer-Only minimum altitude.
This is ultimately why they hit the hill -- they were too low during the approach.
Had they been at or above the localizer-only minimum altitude they would have cleared the obstacles.


How do you figure out which frequency to contact approach on for a class bravo transition?

The example KFCM to KRNH starts under the Class B shelf, in this case you check KFCM's chart supplement, and it says, "MINNEAPOLIS APP/DEP CON 134.7":

Which also agrees with the sectional (shown below).
Zoom out in the sectional, and you'll note different frequencies to the NW and NE of the Class B, so if you're transitioning through, the frequency will depend on which direction you're coming from.

Minneapolis-St Paul TAC chart via skyvector.com

Definitely don't use liveatc for frequencies, as that's a hobbyist site.
If you're departing during the tower's operating hours, requesting flight following would be more practical. Also, see related:

On a chart, how can I find the frequency for flight following?
Where is flight following available?
Why did the tower at a Class D airport not set me up with flight following on the ground?
Is a VFR flight following request implied when talking to tower and advising them of your intended airport?
How do I contact Flight Service while in flight?


Is there a Flights API to get flight information months in advance?

A similar question was asked on Stack Overflow: https://stackoverflow.com/a/2899086/178673 (and marked off-topic, but it did have some answers)

When you are booking a flight, you are typically providing more information than just the flight number, in fact, the query is usually "here is my date/time and arrival/departure information, what is available?"

You are providing the departure date (or range) and arrival date (or range), as well as the city-pairs, and when you have that data you can use the API from FlightStats to find out the list of flights: https://developer.flightstats.com/api-docs/scheduledFlights/v1

If you just knew the flight number, you could use the API call for "Scheduled Flight(s) by carrier and flight number, departing on the given date. /v1/json/flight/{carrier}/{flightnumber}/departing/{year}/{month}/{day}, but again, you still need something to put in as either the departing or arrival date.

Programmatically, perhaps if it didn't return a hit for the date you specified, you could search on x days of either side of the date.  For example, October 19, 2014 didn't return a hit for LH2014 (I know this is a daily, Monday-Friday flight), and the API would return that it didn't hit, so then we (arbitrarily in this example) check two days on either side

Psuedo-code example:

day = 19
/v1/json/flight/LH/2014/departing/2014/10/{day-2}
/v1/json/flight/LH/2014/departing/2014/10/{day-1}
/v1/json/flight/LH/2014/departing/2014/10/{day+1}
/v1/json/flight/LH/2014/departing/2014/10/{day+2}

And find out that it is scheduled on the 17, 20 and 21 of October and that it flies MUC-DUS, in an A319/20.

So, the API isn't going to do all the work for you, but you could probably wrangle the API to give you the information you want in a format you want.  With some built-up logic around the question you're really trying to ask and multiple API calls (Is this flight number available on this date and what are the city-pairs, and if it's not available what date(s) is it available?).

Hope this is helpful. :)


How useful would the space shuttle OMS actually be in atmosphere?

Not all that useful - the OMS engines had 6,000 lbf of thrust each.  For comparison, the Allison J35 (used in the F-84) produced 5,600 lbf of thrust.

Comparing weights, the shuttle weighted 165,000 pounds empty (reference) while the F-84G weighed 11,470 pounds empty.  Since we have two OMS engines on the shuttle, we're double that to 22,940 pounds. So we have to push approximately 8 times the weight.

There are a few other considerations - The OMS engine only had enough fuel for 1,000 ft/sec of delta-V, fuel would be needed for entering orbit, and later 200 ft/sec for reentry, along with whatever else was used for maneuvering during the mission. Therefore there probably wasn't a whole lot of fuel remaining. Also in my comparison don't forget that the shuttle is not known for being very aerodynamic, so you might be able to manage small changes, but nothing of significance.


How does the FOVE system work with the Airbus FMS?

(Source)

Whether the FMS is capable or not of calculating the V-speeds, it should be checked and may be overridden. It is because the airplane database wouldn't know if there's a temporary crane that will affect the climb limit weight, or if 400 ft of the runway are unusable due to maintenance, for example. In other words, 10,000' corrected-length runways are not always the same.

As to FOVE, it is an Airbus tool made by Airbus. The Airbus LPC (Less Paper in the Cockpit) is a laptop* used by the pilots. Essentially an EFB (electronic flight bag). This laptop serves two functions. One, is having the manuals in electronic format, two, is the FOVE—which handles all the performance related calculations.

* Depending on the company, the laptop can be a tablet, or an integrated EFB. I can't speak for the integrated, but the laptop/tablet do not communicate with the FMS, and changes are done manually.

It is more accurate than manual calculation, because manual calculations rely on approved graphs. Interpreting graphs inherently reduces accuracy. See below for a 737-800 example:

(Click to view)

And that's for one flap setting and one condition.

Even if converted to table format, still there will be gaps between any two values, whereas a computer can produce those 'in-between' values, which may provide a takeoff performance advantage.

(Source)

See here for FOVE training manual that has lots of screenshots, etc.


Im not sure on military but its still used by GA and Commercial pilots frequently. Although as has been noted in the comments it is slowly being downsized. It should also be noted that Commercial planes and GA planes use the same facilities and the same ATC. Once in the air a C172 may be given the same instructions as a 777 with the only differences being altitude and speed.

On one hand some VOR's are used for approaches to some airports. There is an effort to replace these with GPS approaches but there are still active VOR approaches out there today so anyone flying IFR to these airports needs them.

They are used for all sorts of IFR navigation and are often the terminal points on an airway, so you may be cleared after departure direct to a VOR.

VOR's can be used as a fixed point for a hold in IFR flying.

VOR navigation (and the use of paper charts for that matter) is still taught during PPL training since GPS is not necessarily installed in every plane.

Some FMS units use RNAV as a backup to GPS or inertial navigation.

This AOPA article covers most of their uses.

Personally, I am a big fan of GPS and fly direct when the airspaces and clearances allow for it (VFR). That being said, the planes I rent generally have dual Nav/CDI installations which I frequently use to cross check my position with the GPS.


What are the regulations regarding the safety briefings and harness designs for open-door helicopters?

The flight was a "doors-off" photographic "experience" conducted by a company called FlyNYON, as seen in this video. The doors of the helicopter are either removed completely or latched in the open position, and the passengers are secured with tethered harnesses which allow them to sit or stand in the open doorway whilst in flight. Unfortunately, the harnesses used by FlyNYON do not have any quick-release mechanism (supposedly because of the risk of suicides) and so the only means for a passenger to free themselves from the harness is to either undo the carabiner-type shackle in the middle of their back or cut through the harness with a knife!

Note: FlyNYON operate these flights as chartered "photographic missions", not as tourist/sightseeing flights which would require quick-release belts and harnesses.

Helicopter harnesses ‘did too good a job,’ trapped crash victims underwater

  All of the victims were upside down and wearing tight-fitting safety harnesses when rescue divers found them trapped dozens of feet underwater inside the capsized chopper, FDNY Commissioner Daniel Nigro said.

When a Device Meant for Helicopter Safety Becomes a Death Grip

  The helicopter that crashed was owned by Liberty Helicopters and flown by FlyNYON, a company that specializes in doors-off helicopter photo tours. The company promoted its safety standards on its website and singled out its “proprietary eight-point Safety Harness System” worn by passengers. It is a complicated system of straps, carabiners and an emergency blade for cutting it off in case of trouble.

Doors-Off Helicopter Flights Under Scrutiny After East River Crash

(Update)
FAA statement on 16 March 2018

  Helicopter operators, pilots & consumers should be aware of the hazard from supplemental restraint devices during an emergency evacuation during “doors off” flights. The FAA will order operators & pilots to take immediate action to control/mitigate this risk. Until then, the FAA will order no more “doors off” operations that involve restraints that cannot be released quickly in an emergency. Additionally, the FAA will conduct a top to bottom review of its rules governing these flights to examine any potential misapplication that could create safety gaps for passengers.


What is the procedure when being vectored for an approach and ATC allows you to pass through the final approach course?

Usually when ATC has a need to vector you across the final approach course, they will tell you about it before they do.  Something along the lines of "N1234 fly heading 230, vectors across final for spacing.".  If they don't and you see that you are getting close, you should ask them if they want you to intercept the course.

The AIM addresses this in paragraph 5-4-3 Approach Control:

  (b) After release to approach control, aircraft are vectored to the
  final approach course (ILS, MLS, VOR, ADF, etc.). Radar vectors and
  altitude or flight levels will be issued as required for spacing and
  separating aircraft. Therefore, pilots must not deviate from the
  headings issued by approach control. Aircraft will normally be
  informed when it is necessary to vector across the final approach
  course for spacing or other reasons. If approach course crossing is
  imminent and the pilot has not been informed that the aircraft will be
  vectored across the final approach course, the pilot should query the
  controller.

  (c) The pilot is not expected to turn inbound on the final approach
  course unless an approach clearance has been issued. This clearance
  will normally be issued with the final vector for interception of the
  final approach course, and the vector will be such as to enable the
  pilot to establish the aircraft on the final approach course prior to
  reaching the final approach fix.

The FAA Air Traffic Control Order Section 9 - Radar Arrivals also has the following directive for approach controllers:

  5-9-3. VECTORS ACROSS FINAL APPROACH COURSE

  Inform the aircraft whenever a vector will take it across the final
  approach course and state the reason for such action.

  NOTE-
  In the event you are unable to so inform the aircraft, the pilot is not expected to turn inbound on the final approach course unless
  approach clearance has been issued.

  PHRASEOLOGY-
  EXPECT VECTORS ACROSS FINAL FOR (purpose).

  EXAMPLE-
  “EXPECT VECTORS ACROSS FINAL FOR SPACING.”


How does Boeing Deliver single aisle jets to South east Asia?

Magic. More specifically, science.

Even regional aircraft are generally designed with 3,500+ nmi range with some load, and more without. It's more than enough to travel to anywhere in the world, given some refueling stops.

In fact, even WWII combat aircraft, which had a fraction of modern airliner range (though it took a big dip once we went from props to jets), were able to travel to both Europe and Japan for duty.


Who legally owns the Flight Data Recorder?

Who legally owns the Flight Data Recorder after an aircrash?

Whoever owned it before the crash!

I'd guess this might be the aircraft owner (e.g. an airline or a leasing company) or an aircraft operator (e.g. an airline).

Ownership is less important than the obligations imposed by the relevant regulatory authorities, and probably by international treaties and agreements, effective in the area where the FDR is located after an accident.

For relevant discussion see NTSB FDR Handbook

  And how is it decided who carries out the crash investigation?

There are a complicated set of rules agreed internationally. From memory I think it goes something like this:

The government appointed body in whose territory(airspace?) the accident occurred. Or
The government appointed body in whose country the aircraft was registered.

EMSA state

  5.1 The State of Occurrence shall institute an investigation into the circumstances of the accident and be
  responsible for the conduct of the investigation, but it may delegate the whole or any part of the conducting of such
  investigation to another State by mutual arrangement and consent. In any event the State of Occurrence shall use
  every means to facilitate the investigation.

  5.3 When the location of the accident or the serious incident cannot definitely be established as being in the
  territory of any State, the State of Registry shall institute and conduct any necessary investigation of the accident or
  serious incident. However, it may delegate the whole or any part of the investigation to another State by mutual arrangement and consent.

Example 1

  The UK Air Accidents Investigation Branch (AAIB) is part of the Department for Transport and is responsible for the investigation of civil aircraft accidents and serious incidents within the UK and its overseas territories.

Example 2

  The NTSB is an independent Federal agency charged by Congress with investigating every civil aviation accident in the U.S.

Normally an air accident investigation organisation takes the lead role but co-opts experts from the airline, the manufacturer and other air-accident organisations with an interest in the incident or with special expertise. Involvement of interested parties (airline, ATC, manufacturer) obviously has to be handled very carefully to avoid detracting from the independence of the investigation.

Most investigations focus almost exclusively on determining facts and recommending actions to prevent recurrences. They generally are not mainly concerned with assigning blame, that may be the focus of a separate legal inquiry.


Are these ballast bags for a hot air balloon?

Almost definitely not.

Hot air balloons control their height by changing their temperature, they don't typically use ballast bags. It's possible that these were ballast bags on a gas balloon, but ash seems like a strange choice for weight considering how light it is.


What is the cause of the noise heard when the landing gear is deployed?

The locks release and typically the gear falls free into place.  It is often aided by hydraulic motors (i.e. to overcome anything that might be trying to hold the gear up, such as slush from the takeoff runway that froze after the gear was in the well), but most landing gear will freefall into place within a couple of seconds even without hydraulic assistance after the uplocks are released.

What you're probably hearing is the sudden onset of the wind noise -- when retracted the landing gear is streamlined, but when extended there is now an open cavity where the gear had been, and this open area in the fuselage creates a lot of wind noise from the suddenly turbulent airflow.  Going from a relatively quite state to a loud one suddenly gives the impression of a "bang."  This is possibly enhanced by whatever noise is made by the uplocks that hold the landing gear in place releasing, and perhaps some louder noise as the initial moments of the gear extension may be noisier than the steady-state noise of being fully extended.

Also, the noise due to the turbulence will subside as the airspeed slows, and extending the landing gear often comes during a phase of flight when the airspeed is being reduced in preparation for the final approach segment and the subsequent landing.


Why was the 737 main rudder servo valve’s vulnerability to causing uncommanded reversals never discovered in testing?

After the accident the NTSB did very extensive testing on the PCU to determine the cause of the failure. In addition to the flight 427 PCU they tested new units, units that had been removed from other aircraft, and the units from three other crashes (SGR517, UAL585 and SLK185) as well as one selected by Boeing that had minimum tolerances.

They subjected the units to numerous tests. They could not get any of them to fail under any conditions expected during flight. The only test they could get a failure on involved an extreme temperature differential of injecting very hot hydraulic fluid suddenly into a very cold PCU. The report states "The extreme temperature differential produced during this test condition would not be expected during normal flight operations." (NTSB report page 79)

All of the PCUs passed the testing procedures for certification even after the failure testing. The temperatures of the PCU and hydraulic fluid on a 737 during flight were tested by Boeing and did not match those used for the testing.

So the PCU can only be made to fail under specific, fairly unrealistic conditions that would not be expected during flight. There was no evidence that those temperature conditions were even present during any of the flights where PCU failure was suspected. There was no reason for testing the part during design or certification in conditions that would not be expected to occur.


Redundancy in Integrated modules avionics

Your question is originally asking for "hardware" redundancy, of which there is none. However, there is operating system and software redundancy built to alleviate hardware issues.

Typical computer based avionics like the EFIS must be FAA-compliant with ARINC 653. Of course, in an experimental aircraft, you could potentially get non-compliant avionics, but there's not much of a market for them.

ARINC-653 requires that there be an real time operating system layer implemented as a form of redundancy. This is a special "round-robin" form of operating system, which in layman's terms, means that the operating system will only spend up to a fixed amount of time on a process before hopping to the next one, meaning that a single process hanging will not halt the rest of the partitions. You might have a navigation process that dies, but the GPS process can continue to operate as it is in a separate partition. It also has partial requirements that partitions are not dependent on each other, but instead retrieve their data directly from sensors. This gives another layer of redundancy in case a dependency crashes.

Running three displays off one processor is ill-advised, and would never be FAA-compliant, but it is technically possible. You would however have to heavily modify the operating system, and the "Guest OS" (ARINC 653) layer.

I'm happy to go far more indepth into this on StackOverflow if you choose to ask a follow up answer there, but the technical specifications are a bit out of scope for the Aviation StackExchange.


What does stick fixed and stick free longitudinal stability mean in simple terms?

Trim the aircraft. Do a "doublet" (means stick forward and back to the trimmed position for a short moment, or rudder deflected and neutral again) to upset the trimmed state.

Now watch the response while you keep all control surfaces at their trim position, making sure the control surfaces don't move when the aircraft goes through its motions. This is quite easy on GA aircraft and big aircraft with powered controls (if you do this on an Airbus, switch it to direct law).

Next, repeat the maneuver but let go of the stick respectively the pedals. Watch how the stick or pedal position moves with angle of attack respectively sideslip changes: This is your control surface floating freely. Again, watch the response. Normally, it will now take longer for the resulting oscillation to die down and the oscillation frequency should be slightly lower.

The first is the fixed-stick aircraft stability, the second the stick-free stability. Normally, stick-free stability is lower and proportional to the stick forces when flying away from the trim point. The difference between both is determined by the hinge moment coefficients of the control surface. For the elevator the floating angle $\eta_f$ is
$$\eta_f = -\frac{c_{r0}+c_{r\alpha}\cdot\alpha}{c_{r\eta}}$$

with $c_{r\alpha}$ the hinge moment coefficient over angle of attack $\alpha$ and $c_{r\eta}$ the hinge moment coefficient over control deflection. Both coefficients are normally negative and the absolute value of $c_{r\eta}$ is larger that that of $c_{r\alpha}$. When $c_{r\alpha}$ is zero, both stabilities are equal because the floating angle is zero.

Another way to study stick-fixed pitch stability is to trim the aircraft at two different speeds or load factors and to measure the trim change necessary between trimmed state 1 and trimmed state 2. The result is the speed stability rsp. the maneuver stability.

Stick-free stability is only relevant in case of manual controls. FBW aircraft only exhibit stick-fixed stability except for the very unusual case that the control surface actuators are overpowered by the aerodynamic forces.


What is the best time to run runway friction tests?

The friction will change over time due to temperature and moisture and other factors.
So, the best time to measure is shortly before a plane is about to land. In order to allow planning of alternatives, allow a longer time.


What do the remarks of this metar mean? "RMK SC1SC5AC1 AC TR SLP116"

So the posted parts means the following:

  RMK    = REMARKS
  SC     = Stratocumulus Clouds
  1      = 1/8 (0/8 = no clouds / 8/8 = overcast clouds)`
  SC     = Again Stratocumulus Clouds
  5      = 5/8
  AC     = Altocumulus Clouds
  1      = 1/8
  AC TR  = Traces of Altocumulus
  SLP116 = Sea Level Pressure of 1011.6 mBar (just add a 10 before the given number and divide by 10)

Cloud Types:

Ac-Altocumulus
As-Altostratus
Cb-Cumulonimbus
Cc-Cirrocumulus
Ci-Cirrus
Cs-Cirrostratus
Cu-Cumulus
Fc-Fractocumulus
Fs-Fractostratus
Ns-Nimbostratus
Sc-Stratocumulus
St-Stratus

(Source: Wikipedia)

Octas:

(Source: Navcanada)


Why is there a maximum altitude to restart a jet engine?

Basically, it gives the pilot the altitude and airspeed at which the engines can be relighted in flight. Based on these values, the pilot has to take a decision to descend etc. A jet engine requires (compressed) air, fuel and a flame source for (re)starting. So air density plays an important part in determining the maximum restart altitude.
In addition, there are other factors at play as well. In case of unassisted (without APU, for example) windmill restarting, the airspeed must be enough to overcome the inertia of the components. In certification memorandum on Turbine Engine relighting in flight, EASA says,

.. as core - bypass ratio of engines continues to increase,  higher  airspeeds  are  generally  required  to  enable  unassisted  windmill   restarting.  The  inertial  effects  because of the increased size, mass,  and number of engine driven gearbox accessories may also contribute  to   increased  rotor  drag  loads,  decrease  starting  performance,  and   possibly  contribute  to  rotor-lock  conditions.

In case a starter is available, the airspeeds required go down (as APU itself is usually a small turbine, the altitude effects are not as pronounced). According to CFR § 25.903 Engines:

(2) An altitude and airspeed envelope must be established for in-flight engine restarting, and each engine must have a restart capability within that envelope.
(3) For turbine engine powered airplanes, if the minimum windmilling speed of the engines, following the inflight shutdown of all engines, is insufficient to provide the necessary electrical power for engine ignition, a power source independent of the engine-driven electrical power generating
system must be provided to permit inflight engine ignition for restarting.

The engine restarting envelope is decided both in terms of altitude and airspeed. It also depends on aircraft. For example, in ETOPS aircraft, the APU must be designed to have airstart capability throughout the normal flight envelope. Regarding this envelope, EASA says,

2 Envelope of Altitude and Airspeed
2.1  Sufficient flight tests should be made over the range of conditions detailed in 2.2 and 2.3, to establish the envelope of altitude and airspeed for reliable engine restarts... The effect of engine deterioration in service should be taken into account.
2.2 Altitude and Configuration. From sea-level to the maximum declared  restarting altitude in all appropriate configurations likely to affect   restarting, including the emergency descent configuration.
2.3 Airspeed. From the minimum to the maximum declared airspeed at all altitudes up to the maximum declared engine restarting altitude. The airspeed range of the declared relight envelope should cover at least 30 kt.


Why are emergency-instructions by cabin crew like "heads down!" not given via PA?

Not knowing that specific video, impossible to tell the scenario.

But in general, you want to not have to rely on technology in an emergency situation. What if you were trained to use the PA system but there is no electricity?
So you train to shout and use non-verbal communications to get your point across in an emergency.


What is the air crash featured in Queen's Innuendo official video?

It was a test crash of a DC-7 conducted by the Flight Safety Foundation under contract to the FAA and in conjunction with NASA (among other organizations) in 1964.

Here is the FAA film, and a NASA report.


Why is a class 2 medical not valid in Canada?

The Cat 2 medical in Canada is only for Flight Engineers, Navigators (once upon a time) and Air Traffic Controllers.  https://www.tc.gc.ca/eng/civilaviation/publications/tp13312-2-menu-2331.htm


How do I enter the traffic pattern if I am coming from a nonstandard direction?

I am answering this question based on U.S. operations and a plan to land on runway 36 using left traffic:

My opinion -

Option 1: If you are arriving from east of the airport (from 090 or 020) you should fly over the airport at an altitude well above pattern altitude, observing the traffic (if any) then descend to pattern altitude west of the airport well beyond/outside the traffic pattern.  After that enter left downwind at midfield from a 45 degree angle at pattern altitude.

Option 2:  If you are arriving from east of the airport (from 090 or 020) and have determined (visually and monitoring the CTAF) that traffic is extremely light or non-existent, flying over the airport and entering directly to a left downwind at pattern altitude (not descending) is an option.

Entering the traffic pattern after approaching the airport from the south or west (from 180 or 200) should be done by maneuvering west of the airport, well beyond/outside the traffic pattern, until you are able to enter left downwind at midfield from a 45 degree angle at pattern altitude.

See the examples from the illustrations below and familiarize yourself with AC 90-66B, which is an excellent guide.(illustrations below are from AC 90-66B)


What is the reason for setting flaps 1 on the ground at high temperatures?

From the A320 Flight Crew Operating Manual (FCOM):

And the image to text:

  On ground, hot weather conditions may cause overheating to be detected around the bleed ducts in the wings, resulting in “AIR L (R) WING LEAK” warnings. Such warnings may be avoided during transit by keeping the slats in Configuration 1 when the OAT is above 30 °C.

(Emphasis mine)

Basically it lets the leading edge anti-ice [hot air] leak sensors breathe, and not display a false positive.

Note that moving the lever to 1 from 0 or 2 at slow speeds (on ground) is called config 1+F, which deploys the flaps as well as the slats (see below).


Why is New York-London used in time measurement for aircraft?

They are (and historically, were even more so) two of the biggest cities in the business world (ranked Alpha++). That specific route has some of the highest rates of business travel and is, therefore, a fairly prestigious, famous route which is popular with fairly wealthy, prestigious people.

They are also two of the most famous cities in the world, and most people know roughly where they are on a map. The fact they're separated by an ocean which is large but was just small enough to be possible to cross safely in the early days of aviation also helped, because it gives the impression of being further than it is.

For example it's a comparable distance to London-Dubai, but that doesn't "feel" as big due to being overland through Europe. Equally while many people know roughly where Dubai is nowadays, it wasn't anywhere near as famous 30-80 years ago.


Is TBO an airworthiness item or just a recommendation?

Unless there is a TBO Airworthyness Directive for that particular engine/airframe/serial number, it is not illegal for GA operations to fly beyond TBO. I can't find an example of a TBO AD but I do remember seeing some.

TBO is a manufacturer recommendation for that particular engine, and does not have any legal enforcement with the FAA. An engine that is well cared-for and has good compressions and clear oil screens (along with other positive inspections) is perfectly fine to fly beyond TBO. There are even stories of people flying 1000 hours or more beyond TBO.

Here are some good reads from around the web:

The Savvy Aviator - Debunking TBO
AOPA Engine Overhauls
Aviation Law - Flying Past TBO, Negligence or Smart Economics

In any case, flying beyond TBO is controversial. Some say that an engine near or over TBO is less likely to fail than one that has been recently taken apart, or at least less likely to fail suddenly.

The key aspect though when buying used aircraft is you don't know how the engine was treated in its run up to TBO. Was it shock cooled? Used for training? Operated out of a grass strip? Poor maintenance? Flown rarely? There are way too many conditions to consider when buying an aircraft near TBO to make the judgement of going beyond it safely or not. The only person who can answer that question is an A&P. That is why TBO is tied so closely to the value of an aircraft. Engine overhauls are expensive, running $25k or more.


What are these two holes on the forward fuselage of a Boeing 747?

The forward opening is the forward outflow valve or forward overboard valve (depending on reference consulted) which opens automatically if airflow in the forward compartment is low. It is independent from the two large aft outflow valves at the lower aft hull used for pressurization.

The second valve is the smoke override valve used in case there is smoke sensed in the the E&E compartment. Basically you try to get rid of the smoke by dumping it overboard. The second function is in case the fans used for ventilation of the E&E compartment fail. Then this valve is opened as well and the differential pressure ventilates the E&E compartment in reverse flow direction. The duct who was supplying the air is now sucking it out of the compartment.

The opening close to the pack inlet on the R/H side is the ground exhaust valve used to dump the air used for E&E cooling on ground overboard in case the temperature is high. This valve is always closed in flight.

Reference:

Boeing 747-400 System Schematic Manual, chapter 21, valves V462 (forward overboard valve), V447 (ground exhaust valve), V448 (smoke override valve)
internal documentation provided by employer of the author


Should I avoid testing unnecessary equipment?

The best practice is to pre-flight everything for every flight:

If you have different pre-flight procedures for different situations then sooner or later you'll use the wrong one and miss something that you should have found. Consistency is really helpful in procedures.
Even if something isn't needed for the flight, checking everything gives you an accurate picture of the state of the aircraft. One broken light is probably just a light bulb, but 3 broken lights and inop pitot heat may be a more serious electrical problem. If you don't know the state of the aircraft then you can't make informed decisions.
Plans change. You might set off for a day VFR flight on a clear, sunny day intending to be home hours before sunset. But if the weather changes quickly or you get delayed then your flight home might have to be night VFR or IFR. If you have equipment issues that restrict your options then it would be best to know that before you depart.

There's nothing wrong with flying with inop equipment provided that you know about it, you've complied with the rules in 91.213 on minimum required equipment and deactivating and placarding, and you've made a conscious assessment of the risk. But not inspecting the aircraft properly or deliberately ignoring inop equipment is a really great way to put yourself in an "up there wishing you were down here" situation.

And from a regulatory point of view, if you don't preflight properly then you're probably in violation of 91.103 ("become familiar with all available information concerning that flight") and of course 91.13 ("No person may operate an aircraft in a careless or reckless manner").


Can high-bypass turbofans cruise at high altitude?

Yes in principle, but some modifications are advisable.

What limits the maximum operating altitude of a jet engine (besides the thrust needed to climb up there) is the length of the combustion chamber and the absolute pressure of the air entering it. Since the atmospheric pressure drops with altitude and the compression ratio of the compressor stays constant, the absolute pressure in the combustion chamber drops with altitude.

For combustion to take place, first the fuel droplets injected into the air stream need to evaporate. This is made easier by higher temperature and pressure, and the lower both are, the more residence time of the fuel-air mixture (caution, PPT link) in the combustor is required for good combustion. Longer combustors have higher pressure losses and weigh more, so engine designers try to limit their length.

Just throttling down can already cause the ignition to stop at high altitude. If a flame-out occurs, the engine cools down quickly and a restart at a lower altitude might not be possible. Turbofans suitable for high altitude operations use special measures to stabilize the flame. When they are in place, there is no reason the B-52 can't continue to fly at 50,000 ft.


Is it possible to perform a spin recovery in IMC?

I do not want to speak for civilian training here, and I do know that each aircraft has its own set of emergency procedures. Those procedures will depend upon the instrumentation that you have available to you. In my case I had full IFR instrumentation with a state of the art inertial navigation system. Spin recovery should be in the set of immediate action emergency procedures that you have memorized, and you should be able to perform them in your sleep. Can you recover from a spin while in IMC? Most definitely, and I speak from experience.

I flew high performance tactical jets for the US Navy. This included the T2, the A4, and the A7E. We only did spin recovery training in the T2. It was a lot of fun. High performance jets are often flying on the edge of their performance envelope. Consider air combat maneuvering where you can easily find yourself in uncontrolled flight, departing the aircraft in a high-g turn, or even nose high at 0 airspeed. I was told it was quite difficult to spin the A7E, which is what I flew in the fleet.

In the Navy we were trained never to look out the cockpit if we thought we were in a spin. There was unusual attitude recovery training under the hood, as well as learning how to recover from departed flight (approach turn stall), and spins. It was drilled into us from day one to come in to your instruments for spin recovery. It would not have mattered to me whether I was IFR or VFR, the decision on recovery was strictly based on instruments. We were told if you look outside the cockpit during a spin you might misinterpret the visual cues, and while not actually in a spin, place the aircraft in one by applying spin recovery techniques. The procedures were something like:

Altitude: below 10,000 feet eject
Angle of attack: oscillating above 23 units of attack
Airspeed: oscillating between 110-140 knots
Turn needle: pegged
All four conditions met: apply spin recovery procedures

I flew over 30 years ago and I still remember these procedures. You might enjoy how I came to appreciate the seriousness of spin recovery. I had a decorated Skipper who had flown all through Vietnam in the A4 as an attack pilot. He stood up one day in the ready room and told us young'uns, "I don't care what you do out there, just make sure you brief it before you do it. Too many of us die because we impulsively decide to do something without thinking it through completely. Know your emergency procedures."

One night I was out at 25,000 feet tooling around after completing my mission, waiting to recover at the ship. A bit bored I had the thought, "I do loops in the simulator where it is blacker then this back home all the time. I have plenty of altitude to get the airspeed I need ... Why not?" And down I went. Unloading the aircraft to negative 1 or 2 G's I picked up airspeed well above what I needed and started pulling back up into the loop. It was dark out, no moon, with a solid cloud layer at 5,000 feet. I remember having an uncomfortable, anxious feeling at some point. Something wasn't right. I started paying attention. It was quiet. There wasn't the usual engine and wind noise! I came into the cockpit and the first thing that caught my eye was the full white of my rather large attitude indicator located in the middle of the instrument cluster. I had relaxed back pressure on the stick at some point. Oh my God. Not what you wanted to see in an A7: nose pointed straight up. Quickly glanced at my airspeed indicator to the left and watched it drop like a rock to the peg at 0 knots. Then the aircraft dropped backwards pushing the tail, and then entering a roll. I was along for the ride though. I wasn't thinking. I wasn't present. Spin recovery didn't enter my thoughts. Never checked my altitude. The aircraft dropped like a leaf for a bit and then settled in a descending roll. I put in opposite aileron and came out of it. Whew! Of course my gyros were toast and the inertial navigation system useless. I ended up coming through the solid overcast and doing my instrument approach to the ship on pressure instruments. I always followed my Skippers advice after that.

Eventually we came ashore and I found myself doing regular emergency procedure training in our simulators. Towards the end of one of these sessions I decided to practice spin recovery. I knew we couldn't get the simulator into a spin, but I thought it might be useful nonetheless. So every time I got to the simulator I made sure I practiced.

The next time I found myself at sea I had finished my flight, and was getting together with a section to practice air combat maneuvering: 1-v-2. We had agreed to meet at a point over the ocean, at a given time, with an altitude separation between flights. I had everything below 15,000 with 5,000 as the hard deck. they had 16,000 an above. You could get there early, or late depending on how you wanted to try to set up the fight. Eventually we set up radio comms. The rule was that we had to talk to one another until one of the flights had gained sight and could then maintain separation.

As I came in to the fight I decided to make a gamble. I unloaded the aircraft with 2 negative G's and descended quick to 5,000 feet. They wouldn't be looking for me that low and so I would be outside their scan for bogies. The top of my aircraft was painted this dull off gray and it blended in with the haze and blue-gray of the ocean underneath. The sky above was clear blue. The tactic payed off and I saw the flight at around 18,000 feet. They knew they were in trouble when I stopped answering their radio calls. I pulled up into an Immellman, but had bled off a lot of airspeed from the dive as I was level at 5,000 feet in the denser atmosphere. As I got to 18,000 feet I was directly behind the two airplanes and I saw my airspeed hit the peg. I quickly called 2 Aim-9 missile shots to win the fight. Then on my back at zero airspeed the automatic flight control kicked the rudder inadvertently, and the A7 entered a spin. How do I know? Well, the AOA was above 23, the airspeed was between 110-140, and the turn indicator was pegged. It was second nature and I was in full control of the situation. As I was assessing the situation I got a call from the other flight lead asking, "Hey where are you?" I replied calmly, "I am a bit busy hold on ..." After recovering from the spin we headed home.


What controllers are used in Airbus/Boeing fly-by-wire systems?

The systems used by complex aircraft are typically made specifically for an aircraft platform and all the different manufacturers of both air-frames and the control systems will have slightly different system architectures.

For example, a system will have a flight control "computer" made by one manufacturer, this will send commands via a data bus to the actuator control unit which will move the control surface via a hydraulic actuator.
Another may have the flight control computer directly control the actuator.
Remember that with flight control computers there will be multiple computers all performing the same task, providing redundancy should one fail. Duplex and Triplex flight control systems have historically been used.

Companies like BAE Systems, Thales, Rockwell Collins, GE Aviation, Parker Aerospace, Safran are just some examples of the many companies involved in the complex supply chain for aircraft parts.

Flight control systems for a single aircraft may be made by separate manufacturers to ensure that no single design fault causes a catastrophic failure or loss of control. This is known as dissimilarity. One manufacturer might make a flight control computer with a PowerPC processor and another will use something totally different.

In other cases, the same ASIC (Application Specific Integrated Circuit) will be specified to two separate integrated circuit manufacturers who will both build the same part.

This interesting article covers some of the points covered above
https://www.aviationtoday.com/2001/10/01/a380-more-electric-aircraft/


What are the eyesight requirements for a medical certificate in India?

The DGCA's relevant requirements adheres and refers to ICAO Annex 1 (see pages 3 and 4). Here's the relevant text from Annex 1:
Class 1

6.3.3.2 Distant visual acuity with or without correction shall be 6/9 or better in each eye separately, and binocular visual acuity shall be 6/6 or better. No limits apply to uncorrected visual acuity.

Class 2

6.4.3.2 Distant visual acuity with or without correction shall be 6/12 or better in each eye separately, and binocular visual acuity shall be 6/9 or better. No limits apply to uncorrected visual acuity.

(Emphasis mine.)
The above is for the requested uncorrected visual acuity, but it is not the full text, e.g., if the correction is surgical, there is more fine print to read.


What regulations or procedures address runway-taxiway interference for aircraft with large wingspan?

Yes this can and has happened with what is considered a "super-jumbo" like the A380 or the 747-8 (Aircraft Design Group VI aircraft).

The FAA must issue waivers to airports to legally accept these types of aircraft due to spacing rules that are in place. A lot of larger airports built quite a few years ago didn't have the foresight to handle aircraft of this size, so special precautions have to be taken when handling those types of aircraft. For class VI aircraft, an airport must have taxiways that are 100' wide and runways that are 200' wide. Note though that an A380's wingspan is 262', so even on a 100' taxiway, the wings hang over 81' on either side.

Usually ground controllers get special training to handle the larger aircraft and maintain separation, but its even a problem for the ground crew before talking to ground control because there are quite a few notable incidents of aircraft being backed into other aircraft.

Here are some interesting reads:

Miami International A380 Preparations
Los Angeles LAX A380 Operational Plan


In case you want to know at what angle does the blade 'see' the incoming wind, you first choose an station of the prop, say at 70% of the prop radius, measured from the axis. If the prop has a radius of 1,2 meters, that station is at a distance 1,2 x 0,7 = 0,84 meters from the axis. Let's imagine, to start with, that the plane is stationary, and the prop turns at 1500 rpm. That's 25 revs per second. In every revolution, our station moves a distance of 2 x π x 0,84 = 5,27 meters. Thus, the chosen station sees the wind coming parallel to the plane of rotation, at an speed of 5,27 x 25 = 131,75 m/s.
But if the plane is moving forward at 150 mph, that's a frontal airspeed of 67,04 m/s. That additional, frontal wind is 'seen' by the station as coming from 90º to the plane of rotation. If you now draw the triangle of velocities, you have one side measuring 131,75 and the other 67,04. The angle (with the plane of rotation) of the total relative wind obtained by (vectorially) adding the two winds is arc tan 67,04/131,75 = 27º
Hope that helps...


How does the wheel speed sensor in a Boeing 777-300ER work?

From this Aviation Studies project report of group 2A2I at the University of applied Sciences in Amsterdam, for a Boeing 777-200:

  Every wheel is equipped with an anti-skid transducer (appendix VII),
  which is installed in the axle. The transducer consists of a rotor and
  stator. According to the speed of rotation, an electrical signal is
  send to the BSCU.

  This computer compares the rotation speed of all the
  wheels and detects when a wheel is rotating slower than the other
  wheels on the MLG. The BSCU will send a signal to reduce braking power
  when the rotation speed of one wheel reduces more in comparison to
  other wheels.

The principle is the wheel axle drives a permanent magnet within a 3-phase winding. The frequency of the signal generated is proportional to the wheel angular speed.

From B777 General Familiarization Manual:

Antiskid and Autobrake Diagram, source

Note: I initially believed the tacho-generator was a Socitec ST80, the same than on A320 (part number is C20105000). However when I wanted to provide a supporting document, I couldn't. So please take this as an assumption only until someone provides the part number from a Boeing document (I don't think there would be a big difference between B777 and A320 tacho-generator anyway).

Tacho-generator, part C20105000, source

More information: Bodet Aero. According to Bodet Aero, their tachometer equips A300, A310, A319, A320, A321, A330 and A340.

More about tachometers: TheAirlinePilots (section "Three Phase AC Electrical Tachometer").

This is a typical installation of the transducer (not a particular aircraft):

Source


What is this thing between the engines on the F-14 Tomcat?

This is the line for dumping fuel in an emergency. If the F-14 needs to land quickly but is too heavy for landing, fuel can be pumped overboard through this pipe. To the left of it is an antenna, and the rod below the fuselage is the arrestor hook.

The Australian F-111s use the same arrangement to great effect during flight displays.

From the F-14 Walk-Around Photo Index Page:

  Back end of the "beaver tail".  The red hole is the fuel dump point.
  The beige item is the rear ALQ-126 antenna, paired to the ones on the
  wing glove area.  This antenna, like the forward ones, was introduced
  with block 110 F-14As and all subsequent aircraft.  Also visible is
  the hook portion of the arresting hook.


Why doesn't the landing gear get raised on the first flight of a new airplane?

Test flying is thoroughly planned, and of the many things to test during development, the landing gear is just a minor part. In the first flight the goal is to check out basic functionality and how well the low-speed performance was predicted. The landing gear can wait for one of the later flights. You can see in the photo of the A350 that the slats are extended and the flaps are in take-off position. The pilots are busy testing handling in take-off configuration, and for that the gear must be down. You can be sure that they also tested the landing configuration at altitude before going down to land.

Generally, the tested envelope of the aircraft will be expanded step by step. Since every flight will contain a take-off segment, it is prudent to check out this part of the envelope first. Once the low-speed regime is tested, consecutive flights will take the aircraft to higher speeds, and only then will it be necessary to retract the gear.

Also, the first flight of a newly developed aircraft has become a ceremonial affair. After having spent hundreds of millions of dollars or euro, and with all the media attention, nobody wants to live through the embarrassement of a gear failure on occasion of the first flight.

This was not always the case. The F-100 went supersonic on its second flight; taking this kind of risk would be unimaginable today without the pressure of an arms race.


What happens to the pressure and density of air passing through shock waves?

Please rethink your understanding of shocks.

In compression shocks, pressure and density increase suddenly without any change as the air gets closer or flows away from the shock front. All change happens momentarily as the air passes through the shock front. A compression shock is caused by an obstruction to the flow.

Supersonic speed means that the obstruction (a speeding bullet, or an airplane, for example) is moving faster than information about its presence will move through the surrounding air. This information would be a pressure change (like sound waves), but the propagation speed of such sound waves is determined by the physical properties of the medium through which they travel. Only exceptionally violent pressure changes can move faster than this limit - this is why you see first a rapidly expanding ball in movies of nuclear explosions which then abruptly changes to a much more leisurely speed of expansion as the ball grows and the magnitude of the pressure change at its boundary drops. (Note the spikes at the bottom of some of the fireballs in the linked movie: They are caused by the steel beams and tension ropes of the towers on which the bombs were placed. The speed of sound in steel is much higher than in air).

Still from high speed movie of a nuclear explosion (picture source)

The opposite of compression shocks are expansion fans: They let pressure and density drop over a region and are caused by a receding contour of said obstruction. Again, ahead and past the fan region the parameters do not change, but the fan region is protracted the more you move away from the contour change causing it.


How is the air traffic managed at a field with many privately owned aircraft?

How is this high amount of air traffic managed?

Air traffic is managed at many levels by many people and is heavily dependent on the airports specifics when it comes to GA. First off not every airplane in the sky is talking to or under control of ATC, for that mater in some airspaces you don't even need a radio on board. The following is pursuant to US FAA regulations, other countries may handle air traffic differently.

The first level of traffic management is the pilot, its the job of every pilot to "see and avoid" other traffic, this goes for both commercial and general aviation traffic. Even if issued a command by ATC you can deviate to avoid an emergency (i.e. hitting another plane).

The next level of traffic management is the various FAA regulations on both ground and air flight operations. These regulations (like traffic rules) are laws and must be followed. They are designed to mitigate traffic in certain areas and will also force you in some areas to at least be on the radio with ATC (e.g. class B airspace). You can read up on the full regs here and you will find most of what you are looking for under "flight rules". Much of the country (below 18,000Ft and above 1200ft generally) is actually class E airspace which does not require ATC communications. This is where most GA traffic lives although small turbo props and the boldest of piston singles can now make it into the levels, most GA planes cant. There are also pre set cruising altitude intervals for VFR and IFR traffic to help keep separation.

Above that you will have ATC who is controlling all IFR traffic, traffic in Class A, B, C, and D airspace and will provide limited radar services to VFR traffic when load permits. When flying under VFR (depending on where you are) you may not need to ever talk to ATC. It is possible to depart an un-towered airport in class G or E airspace, fly around and return with out ever having contacted an ATC facility.

On the ground control depends on the airport. At an uncontrolled field (lots of smaller general aviation airports) the pilots decide. Taxing around is much like driving a car and there are pre determined radio calls to enter the traffic pattern and use the active runway. At a towered airport ground control will monitor and control the flow of traffic on the ramp and the tower will control the traffic from the runway thresholds until the plane departs its airspace.

The only exceptions to the rules here in the US are 5 airports (LaGuardia, Newark,  O'Hare, Ronald Reagan National, and John F. Kennedy) which are subject to the FAA's high density airport rules (specific to the airports) generally speaking the operations are the same in terms of how ATC will handle a given aircraft but departures and arrivals are limited and must be reserved ahead of time.

Another note on IFR operations, ATC will treat all planes the same and will only give priority to a plane in an emergency. Your little Cessna 172 on an IFR flight will receive the same services as a 747 30,000ft above you.

  Do they have an separate air traffic controller?

No. See above but for what its worth the big planes contact the same ATC facilities as the little guys.

Spruce Creek

For what its worth Spruce Creek sits under a Class C shelf as you can see on the sectional here.

Departing from RW 5 and staying below 1200 puts you right between the Daytona Class C and New Smyrna Beach Class D so you may find your self contacting ATC on departure depending on your route you are somewhat boxed in there. Even departing from 23 you may find your self contacting Daytona approach to punch into the Class C there. Technically you can get out of there with out contacting ATC but you may find your self needing to depending on the situation.


Can a non-US citizen (or entity) own an N-registered aircraft?

Nothing in the regulations seems to preclude it - but there are some conditions you have to meet per the FAA:

  An individual who is a United States citizen,
  A partnership each of whose partners is an individual who is a U.S. citizen,
  A corporation or association:

  organized under the laws of the U.S. or a State, the District of Columbia, or a U.S. territory or possession,
  of which the president and at least two-thirds of the board of directors and other managing officers are U.S citizens, and
  in which at least 75% of the voting interest is owned or controlled by persons that are U.S. citizens,

  An individual citizen of a foreign country lawfully admitted for permanent residence in the U.S.,
  A U.S. governmental unit or subdivision
  A non-U.S. citizen corporation organized and doing business under the laws of the U.S. or one of the States as long as the aircraft is
  based and primarily used in the U.S. (60% of all flight hours must be
  from flights starting and ending within the U.S.)

(emphasis added)

So Toyota could not buy an aircraft and register it to their main company in Japan  on the US registry, nor could they buy & register it under a US Subsidiary and subsequently fly it off to Japan to live out the rest of its days shuttling executives around Asia.
A Toyota executive with Permanent Resident status could buy themselves a nice Cirrus and register it on the US Registry though.


Why the lack of faster piston-powered planes?

The power requirement of an airplane grows with the cube of speed. When you fly fast with an airplane which needs to comply with a set minimum speed imposed by regulations, your drag coefficient is nearly constant, so flying faster does two things to a propeller aircraft:

Drag goes up with dynamic pressure, which is proportional to speed squared
Thrust goes down with the inverse of speed.

Power is thrust times speed, so if the the 350 hp get you to 210 knots, doubling the installed power can only bring you to 264 knots. A turbine can still make limited use of the increased dynamic pressure by ram recovery, so here the thrust decrease over speed is not quite as bad as for piston engines.

Expressed in an equation, the power $P$ demand for a given speed $v$ is:
$$P = \frac{D\cdot v}{\eta_{Prop}} = \frac{\rho\cdot v^2\cdot S_{ref}\cdot c_D\cdot v}{2\cdot \eta_{Prop}} \rightarrow v = \sqrt[\Large{3}{}]{\frac{2\cdot P\cdot\eta_{Prop}}{\rho\cdot S_{ref}\cdot c_D}}$$

If you want to fly fast with better efficiency, you need to increase the minimum speed - note that the landing speed of many fast piston aircraft was around 100 mph. Now you need a long runway, and for operation in bad weather or at night infrastructure for instrumented approaches, and you will end up at airports where turbine fuel is easy to get and cheap, but piston fuel will be hard to find and expensive.

As with all expensive machinery, you need to use it often to justify the expense. Now your fuel cost will factor in, and will make a piston engine rather unattractive.

Fast piston aircraft were only built while turbines were not yet available. As soon as turbines emerged, all fast piston designs were obsolete. And aerodynamics in the early 1940s were already very advanced; engineers back then built airplanes which would be impossible to design with the engineers of today. Back then, they got fully manually controlled airplanes into the air when today everyone would refuse to do it without hydraulic boosters at only half the flight speed. They could design cooling ducts which actually increased thrust, an art which is (almost) lost today.


Is it legal to fly without a radio in Germany?

paragraph 3 clearly states that the only exception to the requirement to carry a radio set is when you're not leaving the immediate vicinity of the airfield, and then only when there's no ATC coverage.
That effectively means you can fly a few circuits at low altitude over a small field, but even then many of those would be close enough to a larger airport that has ATC coverage that they'd be covered by that airport's ATC system rather than having their own.

The only "loophole" would be if you could convince authorities that your flight wasn't planned, good luck with that.
Effectively that'd most likely mean you're having to prove to them that you went to the airfield without wanting to fly, just jumped into an aircraft, took off, and started zooming around the sky. Something that's so far out there nobody's going to buy it.


What is the minimum allowed altitude for helicopters over a residential area in the US?

It depends on where it is.
A residential area/houses may or not be "congested" -- that term is not defined. But we typically use 500 feet for helis.
When hovering in an area for a specific purpose, such as photo shoots or other surveillance operation, or for some other operational reason, then we can use a lower altitude.

Sec. 91.119
Minimum safe altitudes: General.
Except when necessary for takeoff or landing, no person may operate an
aircraft below the following altitudes:
(a) Anywhere. An altitude
allowing, if a power unit fails, an emergency landing without undue
hazard to persons or property on the surface.
(b) Over congested
areas. Over any congested area of a city, town, or settlement, or over
any open air assembly of persons, an altitude of 1,000 feet above the
highest obstacle within a horizontal radius of 2,000 feet of the
aircraft.
(c) Over other than congested areas. An altitude of 500 feet
above the surface, except over open water or sparsely populated areas.
In those cases, the aircraft may not be operated closer than 500 feet
to any person, vessel, vehicle, or structure.
(d) Helicopters,
powered parachutes, and weight-shift-control aircraft. If the
operation is conducted without hazard to persons or property on the
surface--
(1) A helicopter may be operated at less than the minimums
prescribed in paragraph (b) or (c) of this section, provided each
person operating the helicopter complies with any routes or altitudes
specifically prescribed for helicopters by the FAA; and
(2) A powered
parachute or weight-shift-control aircraft may be operated at less
than the minimums prescribed in paragraph (c) of this section.]


Does a line up and wait instruction clear me to backtrack the runway?

Your instructor was correct. According to the CAA Radiotelephony Manual[pdf], since the clearance you received included "via A" your clearance was not for a full length takeoff.

From the Radiotelephony Manual, chapter 4:


If planes can go faster, why don't airlines fly faster?

The key issue that determines the aircraft speed is economics. Airlines fly the aircraft that make most sense economically- which is rarely, if ever, the fastest speed possible (more speed equals more drag usually, which reduces fuel economy). More fuel efficient the aircraft is, better the range/passenger capacity, making airlines more money.

The top speed of the (subsonic) aircraft has changed only a little in the past few decades- most developments have been geared up towards improving fuel efficiency, not increasing speed (speed alone doesn't make economic sense to airlines; look at what happened to Concorde).

There is another issue here- most of the passenger aircraft fly in high subsonic (transonic) regime. As a result, the airliners are flown below the drag divergence mach number, beyond which the drag increases rapidly. This limits the aircraft speed.

As a related point, due to the high altitudes at which the aircraft are flown is that there is little speed range to chose from between the stall speed (lowest speed possible) and critical mach number (highest speed possible beyond which flow separates due to local supersonic flow). This limits the practical options available to the pilot.


Why was the Sikorsky Firefly built but never flown?

The director of Sikorsky Innovations Chris Van Buiten called it a

technology demonstrator and research platform that will let us explore the technology, partnerships and technical collaboration...

On 2010 July 29 Verticalmag.com reported

First flight is anticipated later this year, upon completion of ground tests and safety of flight reviews in accordance with Sikorsky standard practice for all aircraft programs.

It vanished from the news a few months later.
Ten years later, it may be hard to get someone from Sikorsky Innovations to speak on the record about Firefly's abandonment, something that the company might consider embarrassing.  But it seems likely that some ground tests failed (cooling? software?), and either the partnerships with the companies providing the batteries, motor, software, etc., weren't important enough to the company (or its owner, Lockheed Martin?) to address those defects, or its other projects became more important.


Why did the MSA for Taipei (RTCP) change?

In 2012 South Korea presented to ICAO design issues with regard to PBN, of those design issues was the reference point for the MSA:

(...) in terms of PBN procedures, every component which is used for RNP approaches or RNP AR approaches, such as waypoint, variation, track and buffer value etc. is based on the airport reference point (ARP). Therefore, it is more reasonable that MSA for PBN Procedures should be centered on the airport ARP, instead of the navigational aids.

Since the old sectors were based on the VOR radials, which is now no longer the reference point after the introduction of the PBN elements, they simply take the highest sector (8,800 ft) and round it up (9,000 ft) to be the MSA for the whole 25 NM.
For uniformity, even the radio based approach (see below) now uses the same reference point as the RNP (RNAV) one. (The one on the left is an old MSA from 2016.)

ICAO's PBN mission is to have uniform specifications and cost-controlled implementation of procedures. So this 'common area' as opposed to the different sectors makes certifying and approving a procedure much easier and cheaper, and puts less strain on the minimum capabilities required from the airborne navigation equipment.
A basic GNSS unit doesn't say which radial/track to a point it is on if it is following a different point, whereas for the VOR reference point, looking at the RMI or spinning the OBS knob for the tuned VOR is pretty straight forward.
This is echoed by the FAA in the TERPS manual, page 2-17. However, note the different points required by the FAA:

RNAV procedures. For RNAV straight-in approach procedures, establish a common safe altitude within the specified radius of the runway threshold (preferred) or the MAP waypoint (WP); for RNAV circling procedures use the airport waypoint (APT WP).

The charts are from the official Taiwanese AIP: http://eaip.caa.gov.tw/eaip


Who manufactured the 737 MAX flap track fairings?

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


Any script to plot multi axis FDR / flight-test data (such as the ones used in air crash investigation)?

I don't think these plots are generated from Matlab or Python, but from special-purpose software. This was discussed in chat a couple of months ago, and one example is Insight Analysis, which offers a GUI interface to put together the kind of chart you're looking for. It's definitely not the only such tool, though.


Could the cabin crew open the lavatory door from outside when someone locked the door from the inside?

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

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

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

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


What is the gross weight limit for a Light Sport Aircraft?

Yes, 1320 pounds is the regulatory Gross Takeoff Weight for Light Sport aircraft.
From the AOPA website:

Light sport aircraft are defined as simple, low-performance, low-energy aircraft that are limited to-
1,320 pounds maximum takeoff weight for aircraft not intended for operation on water; or
1,430 pounds maximum takeoff weight for aircraft intended for operation on water.


Why does spin recovery involve cutting the throttle?

Applying engine power can indeed help to end a spin. But the added thrust will make an overspeed in the ensuing spin recovery much more likely. Also, applying asymmetric thrust on the wrong side will flatten and stabilize a spin. These are the main reasons why the engine should be idle in spin recoveries.
Remember the Boeing 307? The first passenger airliner with a pressurized cabin and the civilian version of the B-17. It was test-flown by KLM personell on March 18, 1939. It entered a spin after a stall and the rudder became stuck in spin direction. The pilot applied asymmetric power in order to stop the yawing motion and succeeded in doing so, but in the subsequent recovery the aircraft oversped and the outer wings broke off. Here is the official accident report.

Boeing 307 in flight (picture source). Note the small fixed vertical surface which was replaced after the crash with a much bigger one.
Symmetrical thrust can be helpful or adverse for spin recovery, depending on circumstances. NASA TN D-6575 from December 1971 says that

no systematic study of the effects of applying power during a spin

is known and

The effect of applying symmetrical power in a spin is believed to be insignificant. A number of varied observations have been made through the years by many people, and the conclusions regarding power effects on spins range from favorable to adverse. […] In almost all cases, the results were not obtained under controlled conditions. Therefore, the type of spin, the center of gravity, the angle of attack, the spin rate, and the line of thrust with respect to the center of gravity were not identified.

Therefore, a general recommendation for applying symmetric thrust for spin recovery cannot be made and only asymmetric thrust has shown to be helpful if applied correctly:

the application of thrust had no effect unless the thrust axis was displaced from the center of gravity and thereby produced a moment.
[…]
For asymmetric power for a twin-engine configuration with the engines mounted on the wings, power from only one engine can produce a large asymmetric yawing moment, which will be favorable or adverse to the spin and recovery, depending on the direction of the moment. Both model and full-scale spin-test results of multiengine airplane designs have shown that power on the outboard engine (e.g., the right engine in a left
spin) can create a large prospin yawing moment, which can cause a flatter and faster spin. On the other hand, power on the inboard engine can create an antispin moment to aid spin recovery. Normally, the manipulation of thrust can be confusing and disastrous if the power is applied to the wrong engine. Therefore, unless asymmetric power is necessary to aid recovery, it is generally recommended that for a multiengine airplane, the throttle be retarded to the idle position on all engines during a spin.

It should also be mentioned that the extreme angle of attack at the inboard engine will produce an extreme sideways displacement of the thrust vector on a propeller or uneven flow in a jet intake. In both cases such a flow condition was most likely not anticipated during design and could result in the loss of the propeller rsp. a compressor stall in the jet engine if full thrust is applied.
While I do not know of a propeller having been lost in a spin, during the flight test of the Dornier 328 an extreme sideslip did indeed overload the left propeller, parts of which tore a massive hole into the fuselage.


What are the mandatory elements of an ICAO flightplan?

About the special characters at the beginning or in the body of the form: They are:

Formatting characters inserted when sending the FPL with a teletype interface on the AFTN network. e.g. < is a carriage return, = is a line feed

Routing indication, e.g. FF is the priority level for a message of type FPL.

These characters are not part of the flight plan data of course.

Parser assumptions

All fields from 7 to 18 are mandatory and included in a Filled Flight Plan message (FPL). Being mandatory doesn't prevent some field to be filled with some dummy value, e.g: Field 18 may contain "0" to indicate no information is provided.

Field 19 can have survival items and remarks left blank. Field 19 is not part of the FPL message, but of the SPL message. The latter is transmitted to other ATS units by the ATS unit having registered the flight plan only in specific situations, e.g. when the contact has been lost with the aircraft (ALERFA).

ATS consistency
While they are mandatory, some fields are used only in specific conditions, in particular the ones related to navigation capabilities.

Example: Not all approaches or routes are PBN required. Not mentioning some navigation capabilities may not be a problem if the capability is not required by an ATS unit to provide the desired routing, but if you use a RNAV approach, the flight plan will be rejected.

For more information on the combinations that are consistent, see the interactive Eurocontrol Flight Plan Guide for IFPS (Integrated Initial Flight Plan Processing System). Example:

When PBN is specified in the item 18 of a flight plan, it indicates the Performance Based Navigation (PBN) levels and/or the Required
Navigation Performance (RNP) levels that can be met. It can only be
present if the aircraft is PBN approved which shall be notified by the
letter R in the equipment of that flight plan.

**Filling instructions**
The content of the ICAO flight plan is detailed in appendix 2 of ICAO Doc 4444 (PANS-ATM) and a filled sample is provided (page 361), but filling instructions are also available separately, e.g.:

ICAO Flightplan Form Basics
Flight Plan Filling at SKYbrary (Eurocontrol)

Note that FAA and ICAO flight plan forms have been different in the past, and while FAA is pushing for the adoption of the ICAO form, it seems the FAA form is still used for US domestic flights.


What are the consequences of throttling up past 100% of N1?

The consequences are always explained in the flight manual. It has graphs which specify what you should do if you exceed the speed, temperature, etc., by how much and for how long. For example (this is for FJ33-5A):

Note that the 100% mark is, in a sense, arbitrary. It does not necessarily mean the absolute max (even the 'normal' max), as can be seen from the example. (I don't know how it is for CFM56). This happens for several reasons; typically, the 100% value corresponds to a fixed RPM number for the whole family of engines. As the engine undergoes modifications, the permissible RPM may increase (or, in some cases, decrease), yet the 100% RPM number is usually not changed, moving the red line instead. In some cases, a civil engine is installed on a military aircraft, and is then allowed to run at, say, 108%, at the cost of much reduced lifespan and service intervals.


How does a departure off a runway used for LAHSO operations work?

The LAHSO line and pulsating white light bar applies only to landing traffic (when in effect and when accepted).

A phraseology example is:

  ATC: "(Aircraft ID) cleared to land runway six right, hold short of taxiway bravo for crossing traffic (type aircraft)."

There is no phraseology equivalent to a departing plane that has to do with LAHSO operations. If a runway is shortened for any reason, "shortened" will be added to the taxi and takeoff clearances, but this is another matter.

When a departure is involved as shown above, it is the landing traffic that needs to land and hold short.

Image source, reference, and further reading: AIM