Is optimal landing flare related to ground effect? Based on other questions it appears that a "flare" is always part of a healthy airplane landing.

This question asked when a flare should be started, and I found it interesting that the accepted answer expressed it in terms of altitude.  Which got me wondering: Is the need for a flare a consequence of ground effect?  And the optimal flare height for a particular airplane a function of when it enters ground effect?

It depends on the type of landing.  If you are doing a normal landing on a normal runway, the round-out and flare are required steps to put you in a position to be in level-ish flight just above the runway (the roundout), and controlling the touchdown by trading inertial energy for increased lift by pitching as you feel for the surface (the flare).

Ground effect has an effect on the flare phase by giving you more energy margin if the ground effect is strong.  So a low wing airplane with large flaps with a strong ground effect will have a lot more support from ground effect than a high wing airplane with small flaps that has weaker support from ground effect.  If ground effect wasn't there, it wouldn't really change how you land too much, except you may tend to carry power into the landing more, or arrive with a bit more energy by increasing the approach speed a bit.  In some airplanes the ground effect is much more pronounced than others (they like to float).

There are landings where you don't really flare at all.  In an extreme STOL approach, you fly to the surface already in the landing attitude, controlling descent rate with power and maybe little pitch adjustments only as required for speed corrections.  If the engine quits during such an approach close to the ground you are out of energy, already "flared" and will land hard and you live with that risk if you're doing that sort of thing.

And of course, there is no flare in aircraft carrier landings.  You fly a constant descent into the ocean, and the carrier's deck just gets in the way of your descent.


When I use a plotter to identify a direction from a VOR, what heading or course is it exactly? When I use my ASA IFR plotter and I'm working off a VOR, what direction am I getting? True course, true heading, magnetic heading, magnetic course?

If you are using a sectional chart and a plotter only, with no other information, remember the following:

If you are using the plotter relative to the sectional grid lines, you are measuring True Course.
If you are using the plotter relative to the compass rose around the VOR, you are measuring Magnetic Course.
True and Magnetic Heading can not be measured directly using the sectional and plotter. It must be calculated. You need to have the wind speed and direction to calculate any heading direction. You can calculate True Heading from Magnetic Heading. You can calculate Magnetic Heading from True Heading.
If you are in the aircraft, you can measure your Magnetic Heading by looking at your Magnetic Compass. You can calculate your True Heading from the Magnetic Heading, using the Magnetic Deviation, and the Magnetic Variation. Conversely, you can calculate your Magnetic Heading from your True Heading using the Magnetic Deviation, and the Magnetic Variation.


Why did some Spitfire variants have their wings clipped? Some Spitfire variants have clipped wingtips instead of the round, elliptical wingtip. The reason for this is to increase the roll rate and low-altitude performance. My question is: How would clipping the wings of an aircraft increase its low altitude performance?

It would increase the roll rate, and it would increase the maximum possible airspeed at lower altitudes.  Generally speaking, decreasing the wing loading doesn't help to maximize the achievable airspeed unless an aircraft is near its service ceiling.  At low altitudes, increasing the wing loading by reducing the wing area often increases the maximum achievable airspeed, by reducing profile drag.


How do I say these situations, according to the runway's status? There is an accident on the runway, for example, the aircraft is disabled on it, so, the runway is_________.
The runway is flooded, or there is oil spill on it, so, the runway is______.
Closed? Unserviceable?

In the US, you would use "closed". From the FAA's Pilot/Controller Glossary:

  CLOSED RUNWAY− A runway that is unusable for aircraft operations. Only
  the airport management/ military operations office can close a runway

And this is part of the example ATIS broadcast from the same document:

  Left approach in use, Runway Two Five Right closed, advise you have
  Alfa.

I don't know if ICAO uses a different term, but "closed" is probably going to be clear to most pilots (and non-pilots, for that matter).


How long is maximum time to investigate an airplane crash? Lion Air flight 610 was crashed on 29 October 2018. It was Boeing 373 Max 8. Almost one year ago. I have not heard any news from National Transportation Safety Committee (NTSC) when they will release the investigation report to media.

From the previous accident, AirAsia QZ8501 occurred on 28 December 2014 with Airbus A320 airplane, NTSC took less than a year time to release the investigation report to media. On 4 December 2015, the NTSC did the release the report.

Then my question is, how long is maximum time to investigate an airplane crash?

According to ICAO, a preliminary report must be released after a year. There is no hard timeline for the full report:

What are a State’s reporting obligations during and after an aircraft accident investigation?
Under Annex 13 to the Chicago Convention, States in charge of an investigation must submit a Preliminary Report to ICAO within thirty days of the date of the accident, unless the Accident/Incident Data Report has been sent by that time. Preliminary Reports may be marked as confidential or remain public at the investigating State’s discretion.
The State conducting the investigation of an accident or incident shall also make the Final Report publicly available as soon as possible and, if possible, within twelve months.
If the report cannot be made publicly available within twelve months, the State conducting the investigation shall make an interim statement publicly available on each anniversary of the occurrence – detailing the progress of the investigation and any safety issues identified.

Keep in mind there is no established penalty for not complying with the above. Indeed in some cases (or countries) it can take up to a decade for a final report to be published.


Are there any training maneuvers that are only allowed when flying with a flight instructor? My understanding of dual instruction training with a flight instructor and a student in a cockpit is, that certain maneuvers, that else would be not permitted, are okay, e.g. simulated engine failure and forced landing on some field (until doing a go-around from 100ft AGL). Is that correct?

For a trained and licensed pilot who currently isn't in training for a new license and just wants to train those things for him-/herself to stay trained, is there a way to do those maneuvers as well without a flight instructor in the cockpit? If that's not possible, does it change, if the single pilot is a flight instructor themselves? Or do they also need to have another flight instructor in the cockpit to train that?

Per the regs, no.  That’s the purpose of solo flying - to allow a student pilot to practice their skills on their own within a limited and safe environment.  However if you are renting the airplane, there may be prohibitions on certain maneuvers or operations eg spins, landing on unpaved runways, etc, so you will have to abide by those agreements.  Your CFI may place limitations on your solo endorsement at their discretion prohibiting certain flying for safety reasons which a student pilot must abide by.  As to any maneuvers required for a practical examination for a pilot certificate or rating, no there are no restrictions against flying them solo, provided they don’t conflict with other regulations eg operating an aircraft in controlled airspace on instruments without an instrument rating, etc.

Some schools also have limits as to what a student pilot can do solo.  I worked for a part 141 flight school once which forbade doing virtually every maneuver ie slow flight, stalls, steep turns, ground reference maneuvers, etc.  This just left the four fundamentals and changing heading, altitude and airspeed during flight.  They were training foreign students for the airlines and were pretty stringent.  I always though excessive.  But I’m sure they have plenty of bad memories where “you give ‘em an inch, they’ll take a mile”


Where exactly are the heating elements in the PA-28-180's pitot mast? I am flying a PA-28-180 but have been unable to find where inside the pitot mast the heating elements would be.

I would like to know this to verify my assumption it does not work in the airplane I am flying. The Pitot-heat has been on for about 40 minutes while flying through 5C weather, upon landing I checked if it was at least warm and it was not.

Can anyone verify or reference me some documentation of where and if you would be able to feel the heater?

You don't actually need to get into the mast to know if the pitot heat is working. I fly a PA-28 and during your preflight check if you engage the pitot heat and allow it to run for a minute or two the pitot tube should be warm to the touch. If it is not your pitot heat is not working (or is not reliable enough for flight).


How would I read a departure chart? How do I read charts like these?

I don't know how to read it, or where to get started on IFR departures and approaches. I can talk to ATC and fly VFR, but I am still unable to fly IFR and would really like to start.

What else do I need to know to start on IFR?

What are fixes, airways, and routes? How do I plan a route myself?

So there's a lot going on in your question to address. First, and most importantly, the info you linked is for ATC, not pilots. you won't get any usable info of how to fly IFR in this airspace. You won't need to know any of this to fly IFR. You won't need any of this to fly VFR either, for what it's worth.

When you fly IFR you file a flight plan that includes your route, destination, and nav points, which are those funny named things like WAVEY in the chart you linked. This is done before you even step in to the plane. Generally a day ahead or early in the morning of your flight, but you can file it right before. a lot of pilots (this is for non-commercial) will take off VFR and then "pick up" their filed flight plan after they are en route. this means you don't have to wait for an IFR release on departure. You just take off, fly in the general direction you are headed, and then ATC will direct you via nav points the rest of the way (or if you're lucky tell you to proceed "as filed", which means no changes to your original plan). For commercial they don't usually have to wait for the release because they are scheduled flights. Thats kind of a different world. I bring up how it happens for non-commercial because you will do a LOT of that kind of flying before you have to be worried about how United and Delta get off the ground.

an IFR approach plate for pilots is still confusing, but there isn't nearly as much going on as what you have linked. Approaches are very very specific for the runway, type of approach (look up types of instrument approaches), and a number of other factors. specific to the point of each has a special thing you do if you can't land for any reason and have to "go missed". This is a huge portion of the IFR training, and nobody can really be self taught this or know how to do it right away. IFR is the hardest rating for a reason.

Don't get too cocky about being able to talk to ATC while VFR. Thousands of experienced pilots a year go through comms training because it's hard. In vatsim is one thing, but the real world of radio is one of the most stressful and elusive parts of the flight. get something wrong and you can lose your license or your life.

If you want to get started with reading charts go to sportys.com and buy their VFR sectional training chart. It's 3 dollars and gets you a manageable section of a navigational chart to learn how to plan and plot and read an aeronautical chart. Theres a lot going on there, you have true longitude and magnetic longitude lines, VORs, airport info, waypoints, obstructions, ground levels, airspace, MOAs. Don't think of VFR as "the easy flying".


What is the material and font used on the panels of most cockpits? I am working on a project for one of my aerospace engineering classes and was curious to see if anyone knew what type of material is used to make the panels of a cockpit (preferably a 737) as well as the font used for the lettering?

Materials: You'll find several materials used for visible 737 flight-deck panels and structure. Most of the panels themselves are aluminum plates, with fiberglass, kevlar, and other plastics rounding out the space.

Font:  Boeing uses something close to a flavor of Futura on its panels.


Is there a technical name for a several mile stretch of flight before landing? A friend of mine lives exactly 5 miles from a small but busy airport that accepts commercial traffic (small commercial jets). Yesterday I noticed that many airplanes were flying low right over his house on the approach to the airport. They seemed to be following the same route. The main runway points in the direction of this house. Is there a technical name for the several mile 'air road' that leads to the airport runway?
Edit: Airport is Teterboro Airport (TEB).

The best term to describe it would be the 'final approach segment', which is defined by ICAO as:

  This is the segment in which alignment and descent for landing are made. Final approach may be made to a runway for a straight-in landing, or to an aerodrome for a visual manoeuvre.

The FAA defines the same as:

  The FAS begins at the PFAF and ends at the landing threshold point (LTP).  The FAS is typically aligned with the runway centerline extended. The segment OEA is divided into the FAS OCS and the visual segment obstacle identification surface (OIS).

Note: Both Eurocontrol (which refers to the ICAO document) and Jeppesen define it only for instrument approaches.


Why don't airliners have any mirrors or cameras? It seems odd that airliners do not have an easy way to monitor critical components on the exterior of the aircraft, should for example, a bird or something else strikes hard enough to cause damage. A mirror or camera would allow a pilot to see and react to a possible dangerous situation quickly. Also, a camera helps a pilot to see what's behind.

Aircraft rarely collide with any objects. Cameras would only be helpful if the extent of the damage is visible from the outside. Instruments, on the other hand, can be used to diagnostic the problem even if the system fails "internally".

E.g. Many hydraulic lines and cables run across the wing. If these is damage on the leading edge, is it the slats? A hydraulic leak on system A? system B? Is the de-ice working? You need instruments to get a better picture.

Some aircraft indeed come with cameras. The Boeing 777 has cameras on the bottom of the fuselage and the tail to aid pilots during taxi operations (the 777, especially the 777-300 variant, is really long...)

The Airbus A380 also has a tail mounted camera. Passengers can enjoy a spectacular view of the clouds, the high speed takeoffs and landings:

As for mirrors, pilots don't overtake other planes or back off like drivers do. There really is no need to know what is behind the aircraft. Pushback is accomplished by the tug on the ground, who has a much better view of the area than the pilots.


How is performance downgraded if the windshield is damaged in flight? A cracked windshield in flight will decrease the performance. To what extent can it disrupt the flight? Can flakes of glass be ingested on tail-mounted engines? Is it possible to blow out the windshield because of the high speed?

The biggest restriction will be the reduced flight speed and cabin pressure which need to be observed with a damaged windshield. No pressurization will restrict the flight altitude to 10,000 ft or less. The crack will not increase drag, but force the pilot to continue flight at a less efficient speed and altitude.

Why high altitude is good for engine efficiency can be found here.

How to find the most efficient flight speed can be read here.

If pieces break off, the aircraft should not continue the flight, but land immediately.

To answer the other questions: Yes, sure, tail-mounted engines are known for ingesting stuff which has broken off from the fuselage. Ice from a leaking lavatory has caused engine damage and the imbalance made the engine shake so hard that it fell off. The whole windshield or substantial fractions of it could have this effect, but I doubt that flakes will damage the engine.

The aerodynamic pressure at the windshields tends to press them into the fuselage. Suction only starts above of the windshield with the curvature of the fuselage contour. However, with cabin pressurization added, the windshield is indeed forced out if it fails. One accident which was caused by using the wrong screws to secure the windshield is BA Flight 5390. The captain was sucked out of the opening left by the window and only his ankles, which got stuck in the flight controls, prevented him from falling out entirely.


What is the purpose of the "Mirror-Thing" over the Mig-29 Cockpit? I noticed that some Mig-29 Fighter Jets have a little mirror-like-thing over the cockpit. I can't imagine a possible usage from it (If it's really a mirror).

Here's a picture from Wikipedia:

As you can see on the following picture, not every Mig-29 has this thing:

What is this "Mirror"-like-thing supposed to do?
Why can't I find it on every Mig-29?
When is this thing used? In combat, training etc.?
How does it help the pilot / trainer in flight?

Additional details to Marco's selected answer.

On the two-seater version, the instructor seat (aft) is not high enough, contrary to other training aircraft, to see the runway. A forward view mirror replaces the rear view mirror and allows the instructor to see ahead. The runway is projected on a second mirror inside the cockpit, creating a full periscope system:

Photo by Pavel Vanka. Modified.

(Source)

Note how the projected part of the image fits very well into the direct view of the exterior.

An opening is created in the canopy when the top mirror is deployed. From below this is what it looks like (not exactly the same model):

Photo by Burkhard Domk. Modified.

The bottom mirror unfolds down to instructor eyes height:

(Source)


Do bluetooth aviation headsets and/or music negatively affect safety? I'm in the process of getting my private pilot's license, and I've come to the point where it's probably time to think about buying a headset.

As I understand it there are a few options ranging from a standard mic and speakers, to passive noise cancellation, active noise cancellation, and even bluetooth for use with iPhones/MP3 players, which I think is awesome, however I'm concerned about distraction while flying.

Has listening to music and/or noise cancellation been at all shown to increase pilot error?

My main concerns are

What if I have a noise cancelling headset on, and the engine undergoes detonation, or what if the aircraft does something I should be alarmed about based on auditory cues that I can't hear?
Same situations as above, but even worse because I'm rocking out to some sweet tunes, is there the possibility that having music will exacerbate the aforementioned issues, or what if ATC comes on, and I hear them, but I don't register what they say because I was jamming to some Kenny Loggins?

Additionally, are commercial pilots permitted to use bluetooth headsets for phone calls? For music? Do crash statistics indicate that music and flying leads to more pilot-error? It certainly can't help...

To my knowledge there are no studies correlating ANR (or good quality passive) headsets with an increase in pilot error, but a several have been done on noise fatigue. There's even an old FAA advisory circular on the subject which basically boils down to "Multi-hour flights listening to the engines drone on and on will make the pilot cranky and error-prone"  - so from that perspective any good-quality headset is a safety enhancement.

As far as missing auditory cues because of ANR (things like the stall warning, funny engine noises, etc.) it's generally not a concern: ANR headsets are good, but they're not THAT good. Because of the way ANR works sudden sounds will cut through. You'll miss "long-term noise" (like the beat frequencies Falk mentioned from unsynchronized propellers), but you're not likely to miss anything safety-critical.
(One notable exception: ANR headsets are good at cutting out wind noise, so if you have a partially unlatched door you won't hear that.)

What you will notice with ANR headsets is that when the battery dies things get loud - sometimes louder than cheap passive headsets. Carrying extra batteries is a must with ANR headsets since having your noise reduction go away in the middle of a flight would be somewhat unpleasant.

As far as music, that's a mixed bag.  Much like having a CD playing in your car, I don't believe it's a significant safety impact unless you're being irresponsible with it (blasting it at a volume that drowns out everything around you, or rocking out when you should be watching for traffic).

Additionally, all the intercoms and headsets I've seen give the com radio priority, and will either cut out or substantially mute the music input when there's radio traffic.  This makes you less likely to miss radio calls, but it also makes listening to music in the plane an absolutely DREADFUL experience (in the northeast where I am there's always somebody talking on the frequency - if you hear half of the song between the radio cutting in it's a good day).

I personally find the distraction from the music muting/unmuting to be more of an issue than boredom from not having music in the first place (if you're that bored you can always look out the window, or tune a local CTAF frequency and listen to the antics), but your experience may vary substantially if you're in an area where the radio is quieter.

Policies for commercial pilots would vary depending on the operation, but for airline pilots using your personal cell phone is forbidden, and before it was forbidden by the FAA it was usually prohibited by the airline.

Part 91 operations (a ferry flight, or a crop duster spraying the local fields) wouldn't be subject to that restriction though, and making a phone call or listening to music would be permissible under the FARs. With all the studies on the negative safety effects of using a cell phone while driving I wouldn't recommend the phone call, but I imagine crop dusting is more fun if you have some music to listen to…


Another airplane almost hit me, but an ACAS Resolution Advisory told me to climb first. Now what? So when a pilot is flying along and suddenly hears a "Climb...  Climb..." Resolution Advisory (RA) from ACAS/TCAS, we are trained to immediately climb to avoid a collision with another aircraft.

There is a reporting requirement in NTSB 830 which states (bold added by me):

  49 CFR 830.5 -  Immediate notification

  The operator of any civil aircraft, or any public aircraft not
  operated by the Armed Forces or an intelligence agency of the United
  States, or any foreign aircraft shall immediately, and by the most
  expeditious means available, notify the nearest National
  Transportation Safety Board (NTSB) office when:

  ...

  (10) Airborne Collision and Avoidance System (ACAS) resolution
  advisories issued either:

  (i) When an aircraft is being operated on an instrument flight rules
  flight plan and compliance with the advisory is necessary to avert a
  substantial risk of collision between two or more aircraft; or

  (ii) To an aircraft operating in class A airspace.

  ...

So my questions are:

Is the phrase "compliance with the advisory is necessary to avert a substantial risk of collision between two or more aircraft" defined somewhere or is there any guidance to say when the report is required?  I.e. is it anytime that we get an RA (even if we visually have the aircraft in sight), only if we actually respond to an RA, or is it if the two airplanes get within a certain distance from each other?
When a report is required, how do we report it and what information is required?  Is there a form that needs to be filled out?

Well, #2 is actually surprisingly easy. At the top middle of the NTSB website, under "Other ways to Contact NTSB" there is an innocuous-looking link that says "Submit a TCAS Notification" (which has you send an email to tcas@ntsb.gov).  Personally I'd follow that up with a phone call to the appropriate regional NTSB office as well, just to be sure you've discharged your obligation under NTSB 830.

The minimum required information for NTSB reporting is described in 49CFR830.6:

  Type, nationality, and registration marks of the aircraft;
  Name of owner, and operator of the aircraft;
  Name of the pilot-in-command;
  Date and time of the accident;
  Last point of departure and point of intended landing of the aircraft;
  Position of the aircraft with reference to some easily defined geographical point;
  Number of persons aboard, number killed, and number seriously injured;
  Nature of the accident, the weather and the extent of damage to the aircraft, so far as is known; and
  A description of any explosives, radioactive materials, or other dangerous articles carried.

There is also a FAA website (www.tcasreports.com) which pilots are encouraged to use for reporting TCAS events - this site is not connected with the NTSB, and would not seem to cover that reporting requirement, but including the information that site asks for in your report to the NTSB would probably be helpful as well.

For #1 things seem a bit murkier: I too could not locate anything from the NTSB or in FAA AC 120-55C that clearly defines "necessary to avert a substantial risk of collision", but broadly I would imagine any Resolution Advisory (RA) is reportable, while Traffic Advisories (TA) would not be.
(The reportability of RAs would seem to be doubly true if you're operating in IMC, where you have no chance of visually assessing the hazard -- Complying with an RA there would seem essential to me.)

Note that AC 120-55C does allow a pilot to disregard a TCAS RA if they're certain that they have visual contact with the aircraft causing the RA - but it also cautions that it's difficult to be that certain:

  Unless it is unequivocally clear that the target acquired visually is the one generating the RA and there are no complicating circumstances, the pilot’s instinctive reaction should always be to respond to RAs in the direction and to the degree displayed.

Presumably in a case where you're operating in VMC, it's "unequivocally clear" that you're looking at the aircraft responsible for the RA, and it's "unequivocally clear" that the traffic does not pose a substantial risk of a collision then following the RA is not "necessary to avoid a substantial risk of a collision" (i.e. you wouldn't have to report the incident).
I'd err on the side of reporting those events anyway though: If nothing else it serves to make the NTSB aware that something happened, and if they see a particularly large number of "somethings" in a given area they may take that up with the FAA to try to isolate and address possible underlying causes...


How does one choose the number of blades and the diameter required for a turboprop propeller? I am interested in the preliminary design of a regional aircraft that uses turboprops as the propulsion method.
Following considerable research online about propeller design (disk theory, BEM...) I am rather lost on where to start.
To put it short, what parameters must be considered when designing the propeller of a turboprop device?
I am mainly interested in obtaining an idea of how many blades would be required and the diameter of the prop.
I have obtained values for the engine power requirements, and from what I can gather the main reason to have an increased number of blades is due to the requirement of absorbing the power from the engine. The latter therefore implicating an increased solidity ratio.
Is the any standard formula/theory that can provide such answers?
Thanks,
FZ

The prop diameter is chosen to provide suitable ground clearance for the desired installation. Then the reduction gearbox ratio is chosen to keep the prop tips subsonic. Then the number of prop blades is chosen to absorb full engine power. Compromises then get made to take advantage of off-the-shelf props in the market and standard gear ratios offered by the engine manufacturer.


What was the first commercial aircraft to have a 'built-in' oxygen system? (Source) Boeing 307 of TWA, the 307 was the first pressurized passenger aircraft.

The 307 (c. 1938) flew as high as 23,300 ft, lower than the jets of nowadays, and did not have a built-in oxygen system as evident by the picture above.

So what was the first passenger aircraft to have a built-in oxygen system, as opposed to carry-on oxygen?

The B307 may have been the first pressurized airliner, but it was usually flown at 12,000', and did not have a passenger supplemental oxygen system.

Boeing 307 / C-75 Stratoliner
1938

"Captain Frank E. Adams, 23.02.2011
I flew the S-307 2 years for Pan American Airways (1943/1944) and today remain one of the few pilots in the world who is still rated for this aircraft. My biggest complaint about this description is that the aircraft could only be pressurized to a maximum of 2.4 psi so that the advertized service ceiling of 26,200 feet is greatly exagerated. A flight altitude of 22,000 feet would result in a cabin altitude of 14,000 feet and we had no passenger emergency oxygen on board. Also,the Wright engines had no turbos and so were basically sea-level engines which could not retain cruising power output above 12,000 feet. For this reason we flew the S-307 at 12,000 feet southbound and 11,500 feet northbound between Miami and Panama."

Later pressurized airliners like the Douglas DC-7, Lockheed Constellation and De Havilland Comet were flown much higher and I expect they would have had some form of built-in supplemental oxygen system for the passengers. (unfortunately I can't find any evidence online)

I did find an advertisement from January 1957 which shows a Scott passenger oxygen system which would represent what was used on the Boeing 707. (first entered service in October 1958)

Flying Magazine Jan 1957


What are the pros and cons of putting a propeller immediately before a slipstream pylon vs. immediately after In the following situation with a slipstream pylon for a self-launching glider, what are the tradeoffs in sticking the propeller before vs. after the pylon?

The wind turbine industry has the same conceptual problem, and their consensus is that the turbine is better with the blades in front of the support tower. However, their support tower is circular and so induces unacceptable turbulence and pressure pulses in the turbine blades. Their system is also designed to operate for decades.
Contrast this to the case in question, where the pylon is slipstreamed and so has significantly lower drag and wake turbulence. My hunch, then is that it seems that behind the pylon is better because the airspeed across the pylon is much lower.
However, I am loathe to reject the wind turbine industry findings with some hand waviness about "slipstreamed" profile.

If it's for something like an airplane or powered glider, for best thrust efficiency and noise level, you want the prop on the front. If behind, the turbulence from the pylon causes both efficiency loss and a loud buzz as the blades pass through the pylon's wake. This is a bigger deal than the effect of the prop's wake hitting the pylon when mounted forward.  The characteristic buzz sound that the Lake Buccaneer makes is from having the prop behind the pylon.
For an engine on skinny pylon with little frontal area, the difference between pusher and tractor is not that much, so noise effects are probably a bigger issue.  The efficiency difference grows when the body in front of or behind the prop gets large. From an article by designer Peter Garrison in FLYING:

Now, how to compare this with the efficiency efficiency of a pusher propeller? For this I'm obliged to turn to books, since it's not possible to do a rule-of-thumb calculation from basic physical principles, as it was for the tractor. In Roskam and Lan, Airplane Aerodynamics and Performance, there is a chart showing the effect of what you might call the occlusion ratio -- the ratio of fuselage diameter to propeller diameter -- on the efficiencies of tractor and pusher propellers. The efficiency of the pusher prop is lower than that of the tractor, but negligibly so, until the fuselage diameter reaches half the prop diameter, at which point the two curves begin to diverge. When the fuselage diameter is 60 percent of the prop diameter the pusher has dropped behind by about 3 percent; by the time the fuselage diameter is 70 percent of the prop diameter, the decrement is 8 percent. An equation is provided (it is also found in Dan Raymer's Airplane Design: A Conceptual Approach) that yields roughly the same result.

The Volmer Amphibian is a good illustration of this.  It had the option of doing either; you could design the mount to point the engine forward or backward.  Part of the attraction of the tractor option was it didn't limit the engine choices (you need an engine with thrust bearings for pusher installation if you want to install it that way, as well as a prop designed for pushers).
Having the prop forward is widely seen as more efficient, with better thrust for the same horsepower and a simpler installation.  I would say most Volmers were built as pushers however, mostly due to discomfort with having a propeller blade tip passing a foot and a half behind the pilot's head (I'd not be too happy having to put the thing into trees with that head chopper right behind my head, and if I was building one, there is no way I'd have the prop on the front).
The consensus however, seems to be that the tractor arrangement is superior performance wise, while the pusher is safer.
In the case of an electric motor glider (which I assume is what you are contemplating) there is another factor, which is the desirability of an aft folding propeller if the mount is fixed.
Recognizing that the efficiency difference may not be enough to worry about although the noise effects could be significant, if the pylon retracts, I'd put the prop on front. If the pylon is fixed and the prop feathers, I'd also put it on the front.  If the pylon is fixed and the prop folds, then it goes on the back.


How do I know which airports have ILS and for which runways? I have been into flying for years but something I can't figure out is how do I, as a pilot, know if an airport I am going to has ILS, which runways would have it and why do only some have it but the other side of the same runway does not?  (I.e. RWY 9 has ILS but 27 does not and they use same frequency.) Do I have to look for something specific like localizer vs localizer DME etc.?

There are published instrument approach procedures for all airports served by an instrument approach.  These are commonly referred to as Approach Plates.  (In paper form). Your local pilot shop should have them, or you can order online.
Just look in the section for the airport you are going to and all the available approaches will be there.  Browse to the ones for the runway in use, and choose one that matches your equipment capabilities.  That’s the one you should request with ATC.  (After you get your instrument rating of course!)
If you have a tablet EFB application and the appropriate subscription they can be brought up on your device.
Your question about ILS glide slope not being available on the reciprocal runway has probably been answered before, but the best answer is because it requires a separate transmitter, which costs more money, and needs to be justified based on need and usage.  (I.e. Perhaps the runway without GS is favored by winds when weather is typically clear...)


Is it possible to control the inlet Mach no. of the engine during flight? While calculating the off design conditions of the engine, we need to know the off design characteristics, such as inlet additive drag. In the book Mechanics of Flight, by Warren F. Phillips, its expression has been derived as a relation between free stream and inlet Mach no. Further while calculating the drag,in one of the example (2.6.1), the inlet Mach no. has been assumed constant at 0.6 whereas the flight is accelerating from Mach 0 to its design Mach no.

This implies that the inlet Mach no. has been somehow achieved as 0.6 even at takeoff, is it practically possible? If not, then how is the drag actually calculated during flight with varying free stream and inlet Mach numbers?

The inlets of supersonic aircraft routinely control (reduce) the Mach number of the engine (at compressor inlet) during flight. This is done using either a 2D ramp type inlet (like Concorde) or a center body (like Mig-21).

These inlets convert the incoming supersonic flow to subsonic flow by forming shock waves in the path of the airflow.

Source: sturgeonshouse.ipbhost.com

In subsonic conditions, the inlets perform two functions:

At cruise condition, diffusion of the free-stream flow to the compressor inlet condition.
At takeoff, acceleration of static air to the compressor inlet condition.

So basically, the inlet design can be optimized such that the Mach number is constant (within some variation) over the engine operational range.

In your case, however, I think that it is a simplifying assumption made for the problem.


Where do the forces exerted on flight yoke/stick comes from and how do they vary with flight conditions? What are the forces felt on the flight yoke/stick based on the deflection of control surfaces and the aerodynamic forces acting on the control surfaces with respect to different aircraft attitudes?

For example: At low airspeed, the controls usually feel soft and sluggish, and the airplane responds slowly to control applications. At high speed, the controls feel firm and the response is more rapid.

Are there any equations that represent the same and how is the force exerted on the flight control yoke calculated?

My question is based on the control loading system of professional grade flight simulators for general aviation aircraft. I want to design a force feedback mechanism for a flight simulator to enhance realism.

I've worked with control loading systems quite a bit. What you describe is a reversible system, where the flight crew feels the aerodynamic forces acting on the primary control surfaces (elevator, ailerons, rudder).

In the aircraft, the pilot pulls on the flying control, which is connected via a steel cable to the control surface, which then deflects. Airflow blows back on the deflected surface, with a force proportional to deflection of the surface. In the picture above $H_e$ is the hinge moment on the elevator, the aerodynamic part of which is $$H_{ea} = C_{he} \cdot ½ \cdot \rho \cdot {V_h}^2 \cdot S_e \cdot \bar{c_e}$$ with $C_{he}$ = moment coefficient, $\rho$ = air density, $V_h$ = airspeed at horizontal tail, $S_e$ = elevator area, $\bar{c_e}$ = mean aerodynamic chord of elevator.

The hinge moment coefficient is a function of trim tab deflection and angle of attack, and is measured in flight tests. Figure below shows $C_{he}$ for the Fokker F27.

On ground, at airspeed zero, $H_{ea}$ is zero but there is contribution of friction, bob weight and down spring.

In the simulator, the same flight control is installed as in the aeroplane, but now is attached to an active actuator that is programmed to push back at the stick with the same force that would be experienced in the simulated flight state in the aeroplane. The actuator features an inner (control) loop and an outer (force feedback) loop.

Force vs. position and position vs. time measurements are taken from flight measurements, which must be tightly reproduced in the simulator in order for the sim to be certified. Reversible controls of small, simple aeroplanes are much harder to simulate than the irreversible, hydraulically actuated flight controls of larger planes, since these do not change as a function of flight state.


Zenith-Add horsepower, NASA-add drag: to create lift. How is this possible? Available horsepower and adding drag to an airplane both create extra lift?  How is that possible?

Available Horsepower

According to the Zenith, available horsepower not used to overcome form drag and induced drag contributes to rate of climb.
Adding drag

NASA's report on the X57, states that drag might need to be added to get rid of excess thrust to create more lift.

From the conclusion of that NASA report on span-wise propellers generating lift:

  A potential constraint on the design of the high-lift propellers system is the total thrust. If large amounts of lift augmentation are required from the propellers, then high thrust values from the high-lift propellers are likely. If these propellers produce excess thrust, then the aircraft will be unable to sustain flight at the desired speed. This implies that drag producing devices may need to be added to the aircraft or the primary propellers operated as windmills to produce additional drag.

(High-Lift Propeller System Configuration Selection for NASA's SCEPTOR Distributed Electric Propulsion Flight Demonstrator, NASA)

This concept seems to be exactly opposite of the first concept!!
Rumours: Ultralights reach a max speed, any extra power is then converted to lift. Is this true?

How do these concepts work?

Equating rate of climb with more lift is wrong. In order to climb the aircraft needs more thrust but a bit less lift. Therefore, the first statement is wrong: Adding more power does not create more lift. The only case where this happens is at high speed and the maximum sustainable lift coefficient: More power allows to fly at a higher load factor, but depending on the flight envelope, might result in a crash. The explanation does not make that connection, so it is wrong.

The second explanation is special for the X-57 because the concept uses the propeller slipstream to create blown lift. At low speed, the thrust needed to maintain flight speed is low and might not be sufficient to create enough lift on the small wing. Adding some drag allows to fly at higher thrust without climbing away. But only in this special case when most of the wing is in the propeller slipstream. So the second statement is correct but only for a single case.

Artist concept of the NASA X-57 Maxwell (image source).


People in a rollercoaster or falling elevator feel the rapid descent, so why don't pilots in the cockpit? Judging from the CVR transcript, the AF447 pilots didn't realize for most of the plunge that they were stalled and rapidly losing altitude.

Why don't pilots in the cockpit get the same sensation of falling down as people in a rollercoaster or a falling elevator ? Both are situations in which you would unmistakeably know you are falling. (If you have never experienced a rollercoaster descent, believe me, it's noticeable ;-). So why and how does it differ for the pilot in the cockpit ?

You only feel the acceleration downward. In roller-coaster this sensation is maximized for maximum thrill. A stall isn't instant: some parts of the wing can be stalled while the rest still provides proper lift. Once the airplane is near or at terminal velocity in a stall it will feel no different from regular straight and level flight.

The onset of the stall was paired with some turbulence which would mask the downward acceleration.

Pilots are also trained to ignore their own sensations because they can be misleading leading to spatial disorientation. You can be in a spiraling dive and still feel as if you are flying straight and level.


What is a passenger disturbance level? I was listening to RealATC for a United Flight UAL1074 which declared an emergency needing to return to Washington Reagan National Airport. During the ATC recording, the flight declares an emergency due to a passenger disruption.

ATC asks for something called the Passenger Disturbance Level. The Copilot replies with a Disturbance Level of 2. As I had never heard this asked for before, I was curious as to what the levels are for and what they each mean?

The FAA has categorized disturbances into four levels:

  Level 1: Disruptive behavior - suspicious or threatening
    Level 2: Physically abusive behavior
    Level 3: Life-threatening behavior
    Level 4: Attempted or actual breach of the flight deck

These are also ICAO standard classifications from the restricted Doc 9811, according to IATA. I'm not sure who came up with them first. That IATA document also provides sample things that might be considered to be each level.


What wind change gradient is necessary to be classified as wind shear? Wind shear is defined as a sudden change in the speed or direction of the wind with altitude.  There's got to be some ratio of speed to altitude or directional change to altitude beyond which it's defined as shear, but I can't figure out what it is.

What is the actual change in wind direction or speed over altitude for a wind shift to become considered wind shear?

On one hand this has to do with how wind shear is actually reported which makes it tough to put an official value on it some times. Wind shear is often reported by pilots when they experience it on landing, takeoff or in the air. This may come in as a PIREP and be disseminated out to other pilots. When you are actually in the left seat you will see the manifestation of wind shear as a sudden loss of airspeed or severe weathervaning of the aircraft. There are many conditions that may cause a pilot to report wind shear. Since different planes at different times may experience different conditions its somewhat subjective.

The Wikipedia definition puts it at:

  Airplane pilots generally regard significant wind shear to be a horizontal change in airspeed of 30 knots (15 m/s) for light aircraft, and near 45 knots (22 m/s) for airliners at flight altitude. Vertical speed changes greater than 4.9 knots (2.5 m/s) also qualify as significant wind shear for aircraft.

The FAA has a nice briefing on it here and their definition (as official as its going to get) is:

Frontal Wind Shear

  As with so many things associated with weather, there is no absolute
  rule, but a couple of clues tell you that wind shear may occur:

  The temperature difference across the front at the surface is 10 °F
  (5 °C) or more.
  The front is moving at a speed of at least 30 knots.

Thunderstorm Wind Shear

  These winds can change direction by as much as 180 degrees and reach
  velocities of 100 knots as far as 10 miles ahead of the storm. The
  gust wind speed may increase by as much as 50 percent between the
  surface and 1,500 feet, with most of the increase occurring in the
  first 150 feet.

Temperature Inversion Wind Shear

  One particularly bothersome aspect of temperature inversion shears is
  that as the inversion dissipates, the shear plane and gusty winds move
  closer to the ground. In some areas of the Southwest, a 90-degree
  change in direction and 20- to 30-knot increases in surface winds in a
  few minutes are not uncommon

Wind Shear From Surface Obstructions

  Some airfields are close to mountain ranges, and mountain passes are
  close to the final approach paths. Strong surface winds blowing
  through these passes can cause serious localized wind shear during the
  approach. The real problem with such shear is that it is almost
  totally unpredictable in terms of magnitude or severity

From personal experience low level wind shear can really do a number on small planes. Bigger planes with more mass will still be affected but less so from what I hear. I have seen speed drops of 15kts momentarily and heading shifts upwards of 30 degrees on final approach in a Piper Warrior in even light shear conditions.

Here is an overly dramatic (and personal favorite) rendering of a micro burst causing wind shear

(source)

Some airports (110 in the US so far) have been lucky enough to have Low Level Wind Shear Detection Systems installed which are pretty neat units, they will detect that as:

  LLWAS wind shear alerts are defined as wind speed gain or loss of between 20 and 30 knots aligned with the active runway direction. "Low level" refers to altitudes of 2,000 ft (610 m) or less above ground level (AGL)

Here is a pretty neat overview from NASA of the various methods to detect it in the air.


What are the costs of 1 hour flight in modern low-cost airlines? Thinking about "low cost" airlines that often tickets of about 40 Euros for 2 flight hours, I was wondering how these companies can cover their costs.

Considering for example EasyJet that fly with Airbus A319 (150 seats), with a unique cost of about 90 million dollars, on a typical 2 hours flight (common average European route) every flight could gain about 6000 Euros in tickets.

I can't understand where is the "gain" considering fuel, crew costs, maintenance etc...

Can you give some references?

For the low-cost model there's an article called The true cost of flying revealed, which uses a 154-passenger A320 for its figures.

  According to the calculations, each passenger on board an Airbus A320, which has a capacity of 154, costs the airline $68.50 (£47.06) for the 260-mile journey.

  The one-hour flight costs the airline an estimated $2.50 per passenger [for fuel].

The total cost equals \$10,549 per hour "with profits as low as \$10 [per passenger] on some flights".

Also from the article—

  If you want to be a millionaire, start with a billion dollars and launch a new airline.— Sir Richard Branson


Do airliners use light alloy wheels, like cars do? Do large and small airliners - up to jumbos like the Boeing 747 and Airbus A380 -
 use light alloy wheels in their landing gear to reduce weight?

If not, why not? Are there reasons unrelated to weight? Do extreme temperatures and rapid temperature changes affect the material in a way that could pose a danger to the aircraft?

Here's a description of small aircraft wheels:

  Available in 4", 5" and 6", these wheel & brake assemblies are cast from 535.2 aluminum alloy for superior strength and corrosion resistance.

And some info on 535.2 AL alloy
http://www.matweb.com/search/datasheettext.aspx?matguid=9347211fc1e1476988dfee51d8241c3c


How is it an advantage for the L1011 to not right itself? A friend who flew the L1011s loved them because of their stability. His joke was that you could put the plane into a banked turn , go to the bathroom, come back, and you would still be in the same banked turn. He felt that other planes like the 767 require far more concentration.

Quote from Source
Can a pilot explain to me how an aircraft not returning to straight and level flight on it's own decreases workload? Would you not have to correct every small bank error just to not go off course?
Edit Jan Hudec is correct when he says that it may involve s comparison of spiral dive tendency. But

still be in the same *banked" turn. H

Makes me wonder why it doesn't right itself

It's because, while neutral roll stability (tendency to stay at a bank angle until disturbed) is an undesirable characteristic for an aircraft that is flying straight and level because more attention is required to keep it there, it's a desirable characteristic while maneuvering.
Normally, you have to choose one or the other, so you choose positive roll stability because that's the priority for an airplane designed to cruise.
Airplanes that spend a lot of time, or are optimized for maneuvering, like aerobatic aircraft and gliders, tend to make neutral roll stability a priority.  This is a really desirable feature on a glider that spends perhaps a majority of its time in thermals in 30 degree banked turns.  When you spend extended periods turning, the tendency to hold a bank angle is a great feature.
As well, when flying on instruments, a tendency to hold a bank angle naturally is a useful feature.  You are generally either in level flight where you want positive roll stability, or are in a standard rate turn, where a tendency to retain the turn rate without input is nice to have.
So, an airplane that had positive roll stability while level and neutral roll stability while maneuvering (on purpose) can be the best of both worlds.


Do crew rest seats count towards the maximum allowed number of seats per flight attendant? We work as flight attendants on a 737-400. We were taught that we must have one FA per 50 seats. Normally our planes have 150 seats and with three FAs we have no issues.

Recently the seat configuration was 152 seats. We called our company and told them that we were not legal to work like that since there were only 3 of us. They stated that 2 seats were for "crew rest" and that we were legal as long as we didn't seat passengers in those 2 particular seats. Is this correct? No one ever said anything said to us about these crew rest seats.

The applicable regulation, CFR121.391, says this:

  (4) For airplanes having a seating capacity of more than 100 passengers—two flight attendants plus one additional flight attendant for each unit (or part of a unit) of 50 passenger seats above a seating capacity of 100 passengers.

Note that the regulation only refers to seating capacity, not whether or not the occupants are "passengers" under the legal definition (fare paying person), or airline employees.  With 152 seats, that airplane has 2 seats, a part unit, of the next "50 seat unit" above 150 seats. So I would say your concern is correct and you need an extra FA to be compliant with 121.391, or at least I would assume so until the airline is able to show that the seats are not counted as "passenger capacity" due to some language in its operating certificate or some other document.  Probably something for your union's legal rep to confirm.


What is the airfoil used in the SB13 flying wing? (Source)

What airfoil is used for the wing of this aircraft?

According to the Wikipedia Page on SB-13 Arcus, the airfoil used are,

  HQ 34N/14.83 at root, HQ 36N/15.12 at tip. Winglet Wortmann FX 7-L-150/K30


Would increasing the number of wheels of a Jumbo reduce the braking distance? If weight was not an issue, would increasing the number of main gear wheels on a jumbo such as the Airbus A380 from 20 to 40 wheels, each equipped with braking disks and braking equipment, considering their extra weight, reduce braking distance.

Would it be any different if the current set up was used but with longer wheelstuds and each wheel was paired with an extra wheel, as with most semi-truck's (articulated lorry's) rear wheels?

Typically, a little gain is obtained.

Larger airplanes use anti-skid technology. Anti-skid works by modulating brake pressure to ensure the tires never skid. It's important to understand the relation between a tire's load, brake pressure, and actual retarding force. First, look at this image :

It shows how as you increase pressure and the wheel starts slipping a bit (turning at a rate slightly slower than when free rolling), the friction coefficient rises sharply. Then after the 10% slippage, the peak coefficient is reached and thus the retardation force reduces. Anti-skid aims to keep the slip raitio as close to 10% as posssible. Therefore the retardation force is maximized.

The brakes of airplanes are strong enough to fully lock the tyres, but this is detrimental (results in 100% Slippage, so maybe 20% retardation force loss). So they can and do maintain optimal slip, therefore using the entire available 'grip'.

Now what happens to this picture if you add wheels?

If the added wheel is not braked (like the nose wheels are) then you lose braking. Indeed, the braked wheels will have a reduced vertical load, so they will provide less retardation force. It's quite useless.
If we add braked wheels then we see the tyiniest bit of gain. Let's see why.

First look at this picture of tire load sensitivity (this one shows lateral force while cornering, but longitudinal force while braking exhibits the same features):

What is important to note, is that as a tire gets more loaded, its capacity to generate friction decreases.

Now for a jumbo: When 20 wheels share 500 tons of load, each tire sees 25t. with a default friction coefficient of 0.8, each tire generates 20t retarding force, so total of 400t retarding force.

Let's add 2 wheels in there. Now each wheels sees 22.7t of load. Their friction coefficient could now rise to 0.82, therefore providing 18.6t, for a total of 410 tons. Certainly far of the 40t that could be naively expected from adding 2 braked wheels! Only the load sensitivity nets us a gain.

It then becomes the usual game of trade-offs. How much mass is spent on bigger landing gear and wheels and additional brakes, versus the gain of harder braking (and thus even stronger landing gear legs?)

Apparently the Airbus guys decided the trade stopped at 20 wheels (because 25t of load on a single tire is the maximum the ground could handle) but they didn't even bother to brake them all, if I remember well only 4 of the 6 wheels of the main boggies are braked! So if you wanted to improve brake efficiency:

Install better tires on braked wheels
Brake the non-braked main wheels
Make some smart aero changes to increase aero downforce & drag
Add braked wheels (and prepare to house them in the main body... good luck!)
Brake the nose wheels (but that would be terribly hard because it was never designed for that)


What exactly is a "coordinated" turn? I am wondering what turn coordination really means and what makes a turn uncoordinated?

I know that when the turn is coordinated, there is no slip and skid, an aircraft is flying a perfect circle etc. and that in one case there is too much rudder input or too little bank etc. etc. But I am interested about forces during the turn. Can someone tell me which force during an uncoordinated turn is too big or too small and literally what makes a turn uncoordinated in terms of forces?

It's important not to overthink it.  I'll keep it simple.  A coordinated turn means you are keeping the tail lined up with the nose in the airstream.  If you are uncoordinated, you are flying sideways in the airstream to some degree or another; the side of the fuselage is being presented to the airflow.

If you learn to fly in gliders, it's obvious because you have a yaw string on the canopy to tell you that the tail is lined up behind the nose in the airstream, since the string itself allows a direct visualization of the airstream.  In power planes with a propeller up front, you are forced to use an inclinometer to tell you the same thing, because it detects the lateral acceleration relative to the vertical axis that is present if the tail is not lined up behind the nose.

Practically speaking, whether you are banked in a turn or in level flight, it really doesn't matter.  The fuselage is lined up in the airstream or it's not.  The ball is centered, or it's not.  Just use your feet to keep it lined up as required using the skid ball.


How do I determine the center of gravity on aircraft? What are the parameters considered and what formulas are used to find the Center of Gravity on an aircraft?

You ask particularly about the Center of Gravity (CG), but not the weight. Any CG calculation will necessarily include the weight as a component of the calculation; therefore I refer to the calculations as weight and balance (or CG) calculations.

The two primary ways that weight and balance measurements are determined are by physically weighing the aircraft and by mathematically calculating based on additions or subtractions to the previous weight. The former is performed by maintenance personnel and forms the empty weight and CG for any given aircraft. The later may be performed by either flight operators or by maintenance and uses the predetermined empty weight and CG as the basis for the calculations; this may be needed due to the installation of new equipment, for example, or a pilot may do such a calculation to determine the weight and CG for a given flight with, for example, fuel and passengers.

For maintenance operations, most aircraft have a section in the maintenance manual or operating handbook that prescribes the process. For flight operations, most aircraft have an information manual or operating handbook that will prescribe the calculation.

One necessary parameter is an established reference datum.

The basic formula is:

$$
C_G=\frac{(W_1\cdot A_1)+(W_2\cdot A_2)}{W_1+W_2}
$$

Where:

$W_n$ is the weight of the aircraft scale's measurement, predetermined empty weight, fuel, or payload, etc.
$A_n$ is the moment arm, in reference to the datum, of the of the aircraft scale's measurement, predetermined empty CG, fuel, or payload, etc.
$C_G$ is the solution to the center of gravity for the aircraft.

The cancelled FAA Advisory Circular AC65-9A contains an entire chapter (Chapter 3) dedicated to the subject of weight and balance, including exactly what you ask, the parameters that must be considered and the formulae used to perform the calculations. Though cancelled, the AC is still available online (I have a print copy).

EDIT: See the comment below from @voretaq7 referencing the excellent "Aircraft Weight & Balance Handbook" quoted here:

  In addition to AC 65-9A the current Aircraft Weight & Balance Handbook
  (FAA-H-8083-1A - available here) contains more than you ever wanted to
  know about computing weight & balance.

This is currently the direct link to the PDF of that document.


In Antonov An-225, why there are radioactive / nuclear signs? Looking at some An-225 images, i see some radioactive signs near the nose radome. Why they are there? I'm sure it doesn't have a nuclear reactor on board or any nuclear medical equipment. The only thing that comes to mind is nuclear density gauges or something related to the radar. Does other planes also use radioactive materials for the same purpose? I've never see, read or heard of any plane using radioactive materials except for propulsion.

Images source:

https://gelio.livejournal.com/193025.html

Find this link on this answer:

Does the Antonov An-225 have an Auxiliary Power Unit (APU)?

https://en.wikipedia.org/wiki/Nuclear_density_gauge

"Radiation" is a broad term and does not always imply radio active isotope material. High power radar units can have adverse effects on the human body.

  The power that radar systems emit varies from a few milliwatts (police
  traffic control radar) to many kilowatts (large space tracking
  radars). However, a number of factors significantly reduce human
  exposure to RF generated by radar systems, often by a factor of at
  least 100:

  Radar systems send electromagnetic waves in pulses and not continuously. This makes the average power emitted much lower than the
  peak pulse power.
  Radars are directional and the RF energy they generate is contained in beams that are very narrow and resemble the beam of a spotlight. RF
  levels away from the main beam fall off rapidly. In most cases, these
  levels are thousands of times lower than in the main beam.
  Many radars have antennas which are continuously rotating or varying their elevation by a nodding motion, thus constantly changing the
  direction of the beam.
  Areas, where dangerous human exposure may occur are normally inaccessible to unauthorized personnel.

The warnings are likely due to the emissions of the radar units in the dome.


How do aircraft steer on ground? How do modern aircraft steer on the ground? Do they have a steering wheel which moves the front wheel (left/right).

I see that there is a Tug vehicle which pushes the aircraft backwards, so the aircraft does not have a reverse gear for sure.

Does the aircraft use the Engine thrust to move forward on the ground or does it have separate motor which propels the wheels?

All of these methods are used.

Nosewheel steering is common on most commercial aircraft using a tiller.  Rudder, differential braking, differential thrust and even motors in the wheels (experimental only as far as I know) are also used, as seen in this video.

Engine thrust is used to move forward but differential thrust might also be used when negotiating tight turns. (Details here)


What happens when an airplane is retired? With launch of new models every few years, what happens to the older airplanes which was in service for more than decades? Where does it get stored.

Who buys old airplanes? Does manufacturers buys it back for reusing the parts or is there any specific companies which buys old airplanes?

There are a few things that can happen:

They are sold to another airline - In some cases the plane may still have life (cycles) left and may find it's later days flying for another outfit. Sometimes airlines for countries with emerging economies can only afford older aircraft and they may end up far from their original homes.
They are sold to cargo airlines - cargo airlines may buy old passenger planes as they may not always be looking to fly the fanciest new airliners since the customer rarely talks back ;)
They end up in the bone yard - aircraft with life left on some parts hold at least some value and may be relegated to a bone yard to be picked over for years to come.
Ultimately, scrap metal always has value...


What hardware and software is needed to put together a basic flight simulator? Due to financial impediments (other priorities in life) I had to postpone my PPL. While browsing the questions on the site here, I was having a look at this question: Can Microsoft Flight Simulator help me learn to fly (or make me a better pilot)?
In that question there is an answer by abelenky where he posts a picture of his old simulator rig. I was wondering about the process to put a similar simulator rig together.
What hardware and software would I need? I've heard about joysticks, but is it necessary to have pedals to move the rudder? To make things as specific as possible, here's how I imagine using it:

The purpose of the simulator
I would like to practice the use of the instruments while enjoying myself. Maybe flying some of my favourite second world war planes for instance, if possible.

What types of planes and flying is it for?
I would see what is available. I have been flying only Cessnas so far. I would love to fly a Focke-Wulf Fw 190 if it's possible.

What types of training or practice?
Navigation, landing, instruments, anything to help with the PPL.

(This is a similar question; it has been closed because it was too broad, since it asked about all possible solutions. I'm only asking which are the essential components to make a basic simulator for PPL-level skills.)

(first off, I need to post a new picture of my sim rig soon.  It's improved since then)

1. Yoke vs. Stick

Try to model it after a plane you're actually going to fly.

If it's a yoke-controlled model (like a Cessna), then you should have a Yoke.
If you're working towards a stick controlled plane (like a Piper Cub), then you should get a simple joystick (not a fighter-pilot-styled super fancy one).

I have this model:
But I want to upgrade to:

2. Throttle

After that, I think a throttle is important.
Making the throttle precisely mirror your chosen airplane is not as important.
(pushing a lever is pretty similar to pushing a control rod).

The three-lever model comes with the Pro Flight Yoke.
Or you can get a a Push-rod version like this:

(more updates when I have time)


Was the F-4 Phantom the only fighter to be in service for the US Navy, Air Force and Marines? As is stated here:

  Furthermore, the F-4 came in both ground- and carrier-based models and
  served in the U.S. Air Force, Navy and Marines. The only other
  frontline fighter to serve in all three services before or since is
  the F-35.

Is that correct? Was any other fighter used by all three services?

The statement is accurate.

Here is a list of all U.S. Fighter Aircraft, in service and retired on Wikipedia. The following is an excerpt from that list for relevant aircraft.

F-4 Phantom (Air Force/Navy/Marines)
F-5 Freedom Fighter (Navy)
F-6 Skyray (Navy/Marines)
F-7 Sea Dart (Navy)
F-8 Crusader (Navy)
F-9 Cougar (Navy)
F-10 Skynight (Navy/Marines)
F-11 Tiger (Navy)
F-12 Lockheed (Air Force, A12 Variant)
F-14 Tomcat (Navy)
F-15 Eagle/Strike Eagle (Air Force)
F-16 Fighting Falcon (Air Force)
F-17 Cobra (Air Force)
F-117 Nighthawk (Air Force)
F-18 Hornet/Super Hornet (Navy/Marines)
F-20 Tigershark (Prototype, cancelled)
F-21 Kfir C-2 (Navy)
F-22 Raptor (Air Force)
F-23 Black Widow II (Air Force, cancelled)
F-35 Lightning II (Navy/Marine Corps/Air Force)
F/P-80 Shooting Star (Air Force/Navy)
FH-1 Phantom (Navy/Marines)
F2H Banshee (Navy/Marines)
FJ-1 Fury (Navy/Marines)
F-86 Sabre/Super Sabre (Air Force)
F-82 Twin Mustang (USAF)
F7U Cutlass (Navy)
F-102 Delta Dagger (Air Force)
F-106 Delta Dart (Air Force)
F-104 Starfighter (Air Force)
F-101 Voodoo (Air Force)
F3H Demon (Navy)
FJ-2/FJ-3 Fury (Navy/Marines)
F-89 Scorpion (Air Force)
F-84 Thunderstreak (Air Force)

This list includes fighter aircraft introduced or in service after 1949, when the US Air Force was created until the end of 1960 when the F-4 Phantom came into service.

Table image was removed because the data is out-of-date. You can view the original image here.


Why is "heavy braking" recommended in an aircraft with carbon fiber brakes in order to prevent brake wear? That seems backwards! I get that standard brakes and carbon fiber brakes are made out of two different materials, but some of the procedures are different between them.

For instance, they recommend "heavy" braking on landing (even if it isn't required) in order to prevent brake wear.  Why is that?

What other differences are there between them that a pilot needs to know about before flying an aircraft with carbon fiber brakes?

I know nothing about this topic but it's quite an interesting one so I did some Googling and found a detailed Airbus document called "Proper Operation of Carbon Brakes". It includes the following information:

  All brake manufacturers highlight the fact that carbon wear is heavily
  affected by brake temperature

This is completely different from steel brakes:

  ...energy is theoretically not the primary parameter for carbon wear,
  whereas it is the  most important one for steel brakes.

The document goes on to say this:

  Generally speaking, to increase carbon brake life, brakes should
  either be operated cold or hot but not at intermediate warm
  temperatures

And this:

  All recommended braking techniques should aim at reducing the number
  of brake applications and optimizing the carbon brake temperature

The specific temperatures mentioned in the document are different for different manufacturers, but generally the intermediate range to avoid seems to be roughly 100-300C. That would explain why 'heavy' braking might be recommended: it's better to use one single brake action that generates more heat and gets into the higher temperatures than to brake multiple times more lightly. Nevertheless, the document also says that overheating is still unsafe and the use of max autobrake is not recommended.

I found a related discussion of exactly this question elsewhere that goes into the physical explanation (although it doesn't quote any sources): at lower temperatures, the carbon becomes a powder which abrades the brake pads, lowering its life; as the temperature rises, the carbon starts behaving like a fluid so the wear is greatly reduced. Most discussions of carbon brakes that I found say that their physical properties and behavior are well documented, but not well understood.


How is lift transferred from rotor to chassis (or weight, the other way around)? I am trying to find out how a helicopter rotor's lift is transferred to the chassis. Equivalently, how is the weight of the helicopter transferred to the rotor blades?

While looking for this online, I find a whole array of pictures of the drivetrain. The force enters the main gearbox (MGB), but leaves the MGB with a spinning axle going to the rotor. First I thought that something happens in the swashplate, but that is not well designed for bearing large amounts of force. So my thought is that somewhere in the MGB there is a nice piece of a bearing.

There is a question like this one for airplane propellers: How does the load transfer from a prop to the airframe? The bearings shown there cannot be found in the MGB of a helicopter (or, at least, I could not find them). It seems to me that a helicopter is hanging from its MGB. Can someone help me out? Pictures would be really appreciated.

The load path is rotor blade to hub, to mast, to mast bearing set inside transmission, to transmission housing, to transmission mounts/struts, to airframe.


Why doesn't Concorde stall when passing Mach 1, where a normal airliner does? As Jay Carr asked: What is a high speed stall?, Jan Hudec explained:

  A difference from normal stall is that after supersonic flow separation the lift remains proportional to angle of attack and so the aircraft continues to behave more or less normally except for the change in trim.

This has leaded me to a question: Why doesn't Concorde stall?

The phenomena you are referring to is better known as "tuck".  This is caused by buildup of a supersonic shock wave on the upper surface of an airfoil when a plane enters the transsonic Mach region of flight (approaching Mach 1).  This leads to a disruption of airflow behind the shockwave, resulting in a pitching down even without excessive AOA.  Concorde actually did this too, and trimmed for it with the help of fuel transfer pumps.  Discovery of this effect in the 1940s also lead to the creation of the "all flying" horizontal stabilizer.

The designers gave Concorde a very long, pitch stable design, along with a delta wing.
That, and 4 powerful Rolls Royce/Snecma 593 Olympus engines, easily pushed it past transsonic, cruising along at Mach 2 up to 60,000 feet.

"Normal" airliners simply are not designed for supersonic flight.


Why are airport firetrucks painted yellow green? In my city, most of, if not all of the fire-trucks that serve city emergencies are red, just like this one:

But every time that I see an airport emergency that requires the fire-fighters, I see this kind of truck:

Is there a reason why the airport trucks are yellow-green and not red?

Because yellow/green has been shown to be more visible than red, especially in low light conditions.  Yellow/green is also more easily identified by people with colour blindness and other visual disorders.

It's the same reason that safety vests are yellow/green.

This article gives some good references.


Is if safe/legal for an aircraft to return to cruising altitude after passenger oxygen masks have been deployed? I was reading reports [1,2,3,4] about a recent Air China flight where one of the pilots was allegedly smoking and, in an effort to prevent the smoke circulating to the cabin, accidentally de-pressurised the aircraft. The passenger oxygen masks were deployed and the crew performed an emergency descent. Eventually the problem was rectified and, after the cabin re-pressurised, the plane climbed again and completed the flight.

The bolded parts of this story are what I'm asking about. If the oxygen masks have been deployed and the plane returns to cruising altitude, then there is no supplementary oxygen available for passengers in the event of a second de-pressurisation incident. This seems unsafe. (I recall reading that the oxygen supply only lasts 12 minutes and is intended only to last for the duration of an emergency descent.)

What are the rules around this situation? Can an aircraft safely/legally climb again after passenger oxygen masks have been deployed?

Once the masks have deployed and any of them have been activated, you no longer have an emergency oxygen supply for all the passengers. Not having that, going above FL250 (may vary in jurisdictions besides the FAA) is not allowed. Up to 250, emergency O2 isn't required for the passengers, since you could descend quickly enough to a safe altitude in the event of a depressurization. Above that, though, having the masks available (and no, hanging down doesn't quite count) is required, both for legality and for safety.

To climb back up to a cruise altitude in the 30's is a pretty significant misjudgement, given the facts as they've been presented to date (which may have significant mistakes in the reporting). Up there with depressurizing the aircraft when you meant to turn off the Recirc fan. Or vaping in the cockpit. Or allowing vaping in the cockpit. Or not turning the packs back on immediately when your FO has incorrectly turned them off.

Sometimes you just have a bad day. And then there are some people who need to switch career paths, because they aren't cut out for the one they're in. We all have our own opinions about what the case is here...


Does the FAA have a document that details each step found in a Component Maintenance Manual? Is there a standard FAA document type for 'general' maintenance steps that a Component Maintenance Manual (CMM) can reference?

For example:

  Once the bulb has been locked into the socket, reference the bulb
  cleaning section in Document XYZ for the complete bulb cleaning
  procedure.

Where can I find Document XYZ?

In general aviation and even working in FBOs, I have referenced AC43.13 to approve repairs that the CMM does not cover. These processes and techniques are approved by the Administrator. In general terms, the FAA tends not to tell you how to meet a requirement but rather gives the requirement then the organization has to meet that requirement through a FAA approved QMS. This process is applicable regardless if you are working with the MIDO, ACO, or FISO. In order to get down in the weeds, you would have to be very specific in your question.

Here is the link to FAA AC43.13 for everyone's review.
https://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentid/99861

Best,
Mark


Could any complications arise if the two FMCs are using different OPS programmes, i.e U10.7 and U10.8A? B737-300
FMCs ARE OF SMITH INDUSTRIES 2907a4/10-6225-003

It wouldn't work. The two FMC's need to communicate & stay in sync; that process requires the same OFP in both.


Why did Lockheed abandon the Constellation II? It’s well known that Lockheed never designed a first-generation jetliner.

Not as well known: they actually did!

The L-193 Constellation II, a quadjet with four tail-mounted engines (a configuration Lockheed would later reuse for their Jetstar business jet, and which was otherwise seen only on the VC10 and Il-62), was designed in both an airliner and a tanker version, and it actually won the U.S. Air Force’s 1955 jet tanker competition, beating out Boeing’s KC-135.  However, since the Constellation II was still a couple years away from flying, the Air Force bought a few KC-135s for use in the meantime, soon decided that they were good enough for the purpose, and eventually cancelled the Lockheed order.

At which point Lockheed abandoned the Constellation II entirely.

Which is odd, because Douglas, in pretty much the same situation at about the same time, didn’t abandon the DC-8 when the prospect for a tanker version thereof vanished in the KC-135’s jet blast; they merely redoubled their efforts with the DC-8 airliner, and went on to great success in the marketplace.  Lockheed, on the other hand, gave up on their jetliner when they lost the Air Force tanker contract.  Why?

Douglas probably already had a few commercial operators interested and close to signing orders when their tanker bid fell through.

Lockheed didn't, and decided to not dump more money into what could very well become a black hole project that'd never pay off.

And it may well be that they decided the design wasn't feasible for commercial operators. Looking at the picture on Wikipedia, almost the entire rear third of the fuselage would have no place to fit doors or windows, making the aircraft useless for passenger operations.

And the air cargo market at the time was a lot smaller than it is today and still saturated with former military aircraft retired after the Korean war and WW2.


How are aeronautical procedures created in the US? In creating new procedures for an airport, does someone from the FAA go to an airport, examine all their information, and choose what kind of approach/departure (for example) will be created? Or do airport officials advise the FAA (chart creators)?

does a worker go to an airport and monitors all information, and choose what kind of approach/departure (for example) will be? Or do airport workers advise regulators (charts creators)?

Yes. :)

Airport/airspace procedures are mainly created by a country's local aviation authority, so if you want an instrument approach to your private airstrip in the US you would contact AFS-420, the FAA's procedures branch, probably through someone at your local FSDO, and ask them to work with you to develop the procedure.
The Procedures people will survey the approach and design a procedure that makes sure you won't hit anything on the ground, and ensure that your procedure won't conflict with other existing procedures.

Once the procedure is designed they'll test-fly it - that's done by another group - and if everything checks out they'll publish charts for it.

Once published the FAA will periodically re-evaluate then procedure, both through flight checks and other feedback (if your new procedure is generating a lot of noise complaints for example the FAA will work with you to reduce the impact).


Why do wing tip vortices tend to be most dangerous when there is a light quartering tailwind? I understand how wing tip vortices be effected under a headwind or crosswind. However, what are the differences in effect between tailwind and light quartering tailwind?

Why is it most dangerous when there is a light quartering tailwind?

According to the FAA's Pilot and Air Traffic Controller Guide to Wake Turbulence (section 2.4.5) it's because:

Light: in light winds the vortices stay around longer; if the wind is greater than 5 knots then the vortices move out of the way quickly and break up
Quartering: crosswinds blow the vortices across the aircraft's flight path, which means that if you're landing next then one vortex might still be over the runway. With no crosswind at all, the vortices will dissipate on each side of the runway, out of your way.
Tailwind: the vortices are blown in the same direction as the aircraft, which means that the vortices from a landing aircraft will be blown down the runway rather than away from it. Again, that's an issue for the next aircraft landing.

They have a handy diagram to illustrate the vortex paths from an aircraft at 0, 3 and 6 knots. You can see that a light, 3-knot crosswind causes one vortex to still be in the flightpath after 20 seconds, whereas with 0 or 6 knots of wind the vortex is out of the flightpath completely. You can't see tailwind on this diagram, of course, but the principle is the same: it blows the vortex down the runway (flightpath) rather than away from it.


Would a rotating skin design mitigate the heating problem limiting hypersonic flight? Would a rotating skin design - where the skin of the aircraft rotates (powered either by an electric motor or the colluding wind) - mitigate the heating problem limiting hypersonic flight?

Would a liquid cooling system (to cool the skin as it rotates along the aircraft) add additional benefit?

TL;DR Probably not.

Assuming we would have a very good mechanical solution/design we would still need a way to get rid of the heat, i.e. a heat-sink.

Imagine the panel (or what ever we will call a part of the skin) is rotated away from the flow (into the inside of the vehicle), than we would need to cool it but where would we store the heat? We cannot extend a heat-exchanger. So the inside of the vehicle would heat up indefinitely.

Essentially we need to come up with a way to discharge entropy from the vehicle. This can be done by either a heat- or mass-flux from the vehicle into the ambiance.

One possibility is related to your second idea: using a cooling system. This requires you to have a fluid propellant. Using the fluid propellant as a cooling fluid first you would not only cool your airframe but you would also enhance your efficiency. This also solves the heat/entropy problem because you would discharge mass (the propellant).

But given the fact that we assumed to have a matured mechanical design of the ‚skin-rotation‘ mechanism you could have multiple panels with ablative coating. So after the first panel is consumed you could (hypothetically) rotate a new one into the flow.


How to calculate the fuel flow using the thrust specific fuel consumption? Using the following parameters:

Static Thrust : $T_0 = 12 KN$
Thrust specific fuel consumption: $C_T=0.7 N/NH$

I know that the fuel flow is linked to thrust with the following formula:

$F=C_TT$.

And I need to calculate the fuel flow in Kg/s.

I started by converting $C_T$ in Kg/Ns:

$0.7 N/NH = 0.7 \frac{1}{9.80665} \frac{1}{3600} = 1.9828* 10^{-5} \frac{Kg}{Ns}$

Then I multiplied this value with the thrust:

$F = 12000* 1.9828* 10^{-5} = 0.2379 \frac{Kg}{s}$

However this does not seem to be the correct answer. What am I doing wrong?

As Peter Kämpf said, the units should be in kg per N per second/hour.
In your case assuming it's a typo, and assuming the formula is $\text{C}_\text{T}$ = 0.7 kg/h per Newton.

Then in static condition,

Fuel flow $= 12 \cdot 10^3 \cdot 0.7 \cdot \frac{1}{60} \frac{kg}{s}$

gives 140 kg of fuel per second. Seems correct.

As a side note TSFC is not a fixed value but a variable of velocity as well. So have to make sure this CT is for static condition.


When do flights get cancelled due to fog? When flights get cancelled due to fog, what triggers the cancellation? Fog is too thick, too wide-spread, blocks the view of tall buildings or other landmarks? Or is the problem the type of air traffic? Too many helicopters or small-ish aircraft?

Other answers have addressed the case of weather that's too bad for flights to operate, but another situation that can occur is congestion.

Take a look at the Average Arrival Rate chart for San Francisco International Airport (SFO) (more details on this in this blog post by an airline dispatcher). During visual conditions with favorable winds, they can operate in normal flow and accept 54+ arrivals/hour into two parallel runways, with departures using the perpendicular runways in between arrivals. But that only works when the cloud ceilings are above 3,000-3,500ft. That procedure relies on aircraft being able to visually see and avoid each other when flying in close proximity.

If there's fog (or low stratus clouds that don't touch the ground, as is typical), that can't happen; you can't send jets blindly into a cloud 750 feet apart from each other. If the clouds are high enough (per the chart, a minimum ceiling of 1,600ft and 4mi visibility), they can use a special SOIA procedure (Simultaneous Offset  Instrument  Approach)—essentially a guided, monitored way to direct jets into a cloud 2,000 feet apart—and accept around 36 arrivals/hour. And if the weather is too poor for that, the average arrival rate can drop to 25 arrivals/hour or below. The extra procedures and spacing required to safely manage traffic in the weather reduces the airport's capacity.

When this happens, there's nothing that stops any specific commercial flight from using the airport—they all have the necessary technology to land in most cloudy conditions—, but the airport's capacity is now too low to accommodate everyone. The FAA will impose a ground delay program to meter traffic into the airport until conditions improve (otherwise you end up with too many flights circling and diverting to other airports, causing many other problems), and the result is flight delays and cancellations.


What is the direction convention for Roll angle? This page from Wikipedia says:

  A positive rolling motion lifts the left wing and lowers the right wing.

Which means that if an aircraft has a roll of +20 degrees, it would bank towards the right. And for a roll of -20 degrees, it would roll to the left.

But when I used this flight indicators library, for a roll of +20 degrees the attitude indicator showed that the aircraft was banking left and vice versa.

Are there any conventions for the roll angle/attitude indicator?

That depends on the coordinate system, and the Wikipedia answer uses the most common convention. Flight mechanics uses a coordinate system with X in flight direction, Y sideways to the right and Z downwards positive. If you now apply the right-hand-rule for the positive direction of rotation around each axis, you will get a positive roll angle around X when the right wing moves down.

Right-hand-rule for rotation: Point the thumb in positive axis direction, then the other fingers will point into the positive direction of rotation.

If, however, X points backwards, then a positive roll angle would be as used in the linked library. Such a coordinate system is sometimes used to have Z point up, but is rather unusual for flight mechanics.


How does washout increase static pitch stability in subsonic swept wings? How does washout increase static pitch stability in subsonic swept wings, more specifically in slow moving aircraft (eg. ultralights), 15mph to 60mph?

I understand washout is used to delay full stalls ( at least in unswept wings), but isn't pitch stability related to cg and centre of pressure?

See picture below of a european designed Archon SF1 rg ultralight with swept wings and retractable landing gear. Mid engine single prop is shown forward of the twin vertical tails.

Since its earliest days during the pioneer era, washout on a swept wing has been accurately described as "putting the tail at the end of the wing." It works in exactly the same way as a tail stabilizer.

As long as the change in moment of the rear surface is greater than the change in moment of the forward surface the plane will be statically stable. It matters not whether the tail is inboard, outboard, moved ahead of the wing (as a canard), tacked on the end of a swept wing, or even tacked on the back of a straight wing in the form of a reflex trailing edge.

On a straight, unswept wing washout can delay the stall a little, but stalling is a complex subject and best treated separately.


Would an F-15 or similar stand in be able to continue flight at high speed if it lost its canopy? Let's say for whatever reason, miscued ejection system perhaps, a jet in flight at exactly mach 1 blew its canopy but did not eject the pilot.  And we can assume the altitude is fairly low (to exclude the attendant freezing/suffocation that would ensue).

My friend and I have been arguing about this.  He insists that it would result in catastrophic damage to the jet due to a sudden lack of aerodynamic stability and that the pilot would be grievously harmed or killed.

For my own part, I'm just not so sure.  It seems to me that if said pilot was wearing a JHMC or some helmet with visor that he'd have plenty of time to react and set the aircraft safely down.  And could probably do 400 knots comfortably on his way home to complain about the faulty ejection.

And I figured a jet is so very large and aerodynamic over its entire body, without the canopy it'd be less so, but still not so badly that the thing would be torn to pieces as a result, right?

The only similar story I could find was of an F-14 that lost its canopy, but the pilot only mentioned going 320 knots and it not being as loud as he expected.

So mach 1 is a key part of this question, I think.  I can't find a reasonable answer to settle our dispute, someone please help!  I really want to settle this.  Thanks in advance.

Several F15's have had incidents of canopy loss, and all the ones I have found came back and landed safely. The latest incident I can find was in 2014 off Okinawa. I see no reason why there would be any such catastrophic failure of anything on the aircraft unless the canopy impacted some part of the aircraft as it departed. Ejection systems are designed to allow the crew to exit the aircraft at pretty much the entire flight envelope. Yes, at supersonic speeds the crewmember will probably be sore for quite some time, but it's been tested and used in real life and it works.


Why might a too-wide runway be a problem? In the September 2020 issue of EAA's Sport Aviation, Budd Davisson writes

Runway width becomes a problem for some taildraggers when it gets to be less than 35-40 feet because of the lack of visibility.

Sure.  When you can't see the centerline, it's nice to have some lateral margin of error.
But later in the article (p. 74) in the caption of an overhead photo of a small airplane on a runway seven times wider than its wingspan, he writes

Oddly enough, super-wide runways can cause as many problems as very narrow ones, especially for taildraggers.

What might such problems be?  (Not wandering into the grass.  Even if you can neither look over the nose nor locate the runway's edges, if during takeoff or rollout you drift to one side, wouldn't you still notice the center stripe or the edge or the lights in time to correct?)
Do any NTSB reports mention a too-wide runway as the cause of an incident?

The issue has always been human perception.  Pilots are tasked with trying to make great landings.  One way they do that is with peripheral vision.  If the runway is too wide, they lose that extra clue on when to roundout and flare.  They may flare too early and stall the aircraft too high above the runway.  This perceptual clue is more important for tailwheel pilots than tricycle gear pilots.
From the FAA AIM 8-1-5.

Illusions Leading to Landing Errors.

(a) Various surface features and atmospheric conditions encountered in landing can create illusions of incorrect height above and distance from the runway threshold. Landing errors from these illusions can be prevented by anticipating them during approaches, aerial visual inspection of unfamiliar airports before landing, using electronic glide slope or VASI systems when available, and maintaining optimum proficiency in landing procedures.

(b)Runway width illusion. A narrower‐than‐usual runway can create the illusion that the aircraft is at a higher altitude than it actually is. The pilot who does not recognize this illusion will fly a lower approach, with the risk of striking objects along the approach path or landing short. A wider‐than‐usual runway can have the opposite effect, with the risk of leveling out high and landing hard or overshooting the runway.


Why would both wingtip lights be red? I live under Chicago's airspace. One evening I saw a plane approaching Chicago with both wingtip lights red and the front landing lights flashing. I've never seen that before, why would that happen?

You might have been seeing a general aviation aircraft from an orientation similar to the one pictured.

You'd see the left navigation light which would be red.

The rotating beacon would also be red, but if the airplane was positioned like this and the beacon was the rotating, not blinking type, you might just see two mostly constant red lights. Being that it was dark you might mistake the second red light for the navigation light on the other wing.

It is becoming more common on general aviation aircraft to have a pulse option on the landing lights. I flew for a 135 operation for a while under which our contract required this to be installed and operational for all our aircraft.

This seems to be the simplest explanation for what you are describing. If we consider Occam'z Razor it is likely to be what you saw on the occasion you described.


Can accelerations be used to calculate load factors? Can I use the z accelerations to calculate the load factor in that axis? Please explain how or why not.

It sure can; in fact, they are equivalent (with an offset of 1G).

In the body frame, the vertical equation of motion is:

$$Z+mg\cos\theta\cos\phi=m(\dot{w}+pv-qu)$$

Accelerometers can't measure inertial or gravitational forces, so vertical acceleration as measured is $N_z=Z/m$.


What are the differences between type B message format and EDIFACT message format? IATA say's the standard format for transmitting passenger messages is UN/Edifact. Somewhere else it says the standard is type B format.

what are the differences between these two? Or are they a same format?

There are many types of messages which are used very specifically within the aviation Industry and TypeA and Type B are the most notorious ones.

Its not the message format that differentiates them , its the characteristic message delivery and response that does.

Type A - Expect immediate application response, have timeout handling in place at the application level, delivery is not guaranteed and could expect loss of messages. EDIFACT is one of the well known industry accepted and following TYPE A message formats..

Type B - Guaranteed delivery and will make anything and everything possible to deliver the message . Does not expect an immediate response back.

Regarding the format of the messages, the type A message formats are governed by PADIS ( PASSENGER AND AIRPORT DATA INTERCHANGE STANDARDS MESSAGE STANDARDS DOCUMENT). It does differ for each applicaiton( reservation, ticketing, DCS etc). Here is a sample one for PNRGOV standards.

https://www.iata.org/iata/passenger-data-toolkit/assets/doc_library/04-pnr/PNRGOV%20EDIFACT%20Implementation%20Guide%2013_1.pdf

For TYPE B , always refer to the AIRIMP documents which governs the TYPE B mesasge formatting..

Here is a sample of the same..
ftp://ns.tais.ru/pub/doc/AIRIMP34.pdf

Thanks,
Jothi