Is there a preferred wind direction for a helicopter in hover? When hovering, how does a pilot deal with wind direction? As when landing is it preferable to point the nose into the wind? Is this a primary consideration for the pilot considering that he may need to maintain visibility on something, such as during a rescue or a news operation?

And is wind direction more of a factor when hovering in or out of ground effect?

In most helicopters, the wind direction when hovering is of concern to the pilot, as is which way you turn when hovering.

The following applies to a single rotor helicopter with the tail rotor mounted on the left and the rotor turning counter-clockwise.  The opposite applies to clockwise rotating rotors and mounting the tail rotor on the left versus on the right would take more pages of text!

  Hover with no wind.

As the rotor rotates counter-clockwise, the torque reaction on the fuselage wants to turn the nose to the right.  The tail rotor "pushes" the tail to the right to balance this torque.  It is by varying the angle of attack of the tail rotor that we can change the amount of thrust from the tail rotor and therefore have yaw control.

The tail rotor is no different to the main rotor, it just operates in the Y axis rather than the Z axis and is subject to vortex ring state.

The vortex from the tail rotor is to the left.  If the helicopter is yawed right, the tail moves left and the tail rotor moves into it's own vortex causing a reduction in angle of attack and therefore thrust.  If the turn is too fast, this reduction can lead to a loss of tail rotor effectiveness.

Also in a no wind hover, the vortex from the main rotor is forced downwards.

All of what follows is for a counter-clockwise rotating rotor and applies to all single rotor helicopters.

  Hover with the nose into wind, but not with enough wind to generate
  effective translation lift.

This state is more or less the same as for a no wind hover and is the easiest (and therefore preferred) direction in which to hover.  Turning the aircraft has the same risk as in a no wind hover in that turning too quickly to the right can lead to loss of tail rotor effectiveness.

  Hover into wind with enough wind speed to generate translational lift
  (let's say about 15 kts)

Now things start to get interesting.  If you turn to the left, the vortex from the front edge of the main rotor is blown backwards by the wind across the tail rotor and causes a decrease in the angle of attack of the tail rotor blades since the wind from the vortex is blown on to the right hand side of the tail rotor.  Therefore, a lot more left pedal is required as the helicopter turns from 0 degrees (relative to the wind) to 270 degrees.  As 270 degrees is reached and passed, the vortex is no longer interfering with the tail rotor and the angle of attack for the same pedal position is increased.  If the same pedal input is maintained, the rate of turn will increase rapidly and if not corrected, can lead to an uncontrolled spin.

If you turn to the right, the opposite happens.  More right pedal (less thrust) is required in the first quadrant of the turn from 0 degrees to 90 degrees since the vortex is blown into the face of the tail rotor causing an increase in angle of attack and therefore greater thrust.  As the nose passes 90 degrees, the angle of attack decreases and left pedal must be added to prevent a sudden acceleration in yaw.

You should be able to see that the amount of pedal required changes as the turn continues and without constant adjustment, a steady turn cannot be maintained and with enough wind, and a pilot who is not quick enough on the pedals, control can be lost.

Now let's take the turn out of the equation and consider steady hovers in wind that is not "on the nose".

  Wind from the left quarter, i.e. 270 - 0 degrees. This is effectively the same condition as that first quarter of a left turn with wind from the front.

This is the difficult one.  Wind is never constant. It is always changing slightly and turbulent.  As the main rotor vortex is blowing into the tail rotor, the tail rotor is operating in a very turbulent and unpredictable environment.  Rapid and constant pedal inputs are required to maintain control.  Any deviation not caught immediately can lead to a loss of control.  It is very difficult to hover with the wind from the left quadrant and is therefore usually avoided.

  Wind generally from the left (a left crosswind)

As the wind is blowing into the face of the tail rotor, its angle of attack is reduced as the airspeed through the rotor increases.  This can lead to the loss of tail rotor effectiveness or even a stall of the blades as the angle of attack exceeds the critical angle.

  Wind from behind.

The primary effect here is the tendency of the fuselage and vertical stabiliser to "weather cock" the aircraft.  It naturally wants to face into wind.  If a yaw begins and is not immediately corrected, due to the effects above, the yaw can increase rapidly and suddenly.  Additionally, the wind is never constant and varies between passing to the left and to the right of the tail rotor.  Therefore, hovering downwind needs immediate and constant corrections to yaw.

  Summary

Hovering into wind is very much preferred and is always chosen unless operations require something different.  Hovering with the wind from the right is the next "most" preferred position with quartering winds from the left and hovering downwind to be avoided if possible.

All of this said, it's a standard part of training to learn how to hover in these conditions and how to maintain constant rate turns.  It does require a lot of learned skill and you must be quick and accurate on the pedals with constant corrections.

Incidentally, early models of the UH-1 were particularly difficult to handle in certain wind conditions and the tail rotor was moved from the right to the left on later models to improve handling.

In a light helicopter with little power reserve, e.g. the R22, hovering in strong gusty winds is an intense part of operations.  I had some close calls when learning how to do this including a loss of control which I only recovered by pulling in power and accelerating into forward flight.  Not good on an airfield with other aircraft operating since my "low hours brain" focussed only on regaining control.  I am ashamed to say that looking around took second place but I did learn an important lesson and with hindsight, the right thing to do would have been to land and discontinue the flight as the wind got more gusty.


Does closing window shades save fuel? On a 13-hour flight all shades were ordered closed (entire flight—not cool), same airline on a 3-hour route, same thing.

Both flights took off in the morning, around 8 AM.

Only reason I can think of is to keep the cabin cool, lower the demand on the engine bleed, and burn less fuel?

I ruled out the minimize jet-lag reason as sleeping masks were handed out and same thing happened on the shorter flight.

It isn't due to "lowering the demand on the engine bleed" because the air conditioning is done as part of the standard pressurization of the cabin - the air is bled from the engine, cooled to a very low temperature and then heated to the desired temperature for the cabin, so shutting the blinds wouldn't affect that because the air is still cooled and then reheated.

It is purely for jet-lag and sleeping issues - a single blind open in a darkened cabin can disrupt even those people wearing the eye masks (those things arent perfect) and can disrupt people who have woken to go to the toilet during the cabins "sleep period" (think how horrible it is if you get up in the middle of the night and turn on a bright light - its easier to get back to sleep if you keep lighting muted throughout your activity than it is otherwise).


How many flights follow the North Atlantic Track relative to those that don't? What is the ratio of flights that follow the track system in the north Atlantic and those that don't? Also what is the general trend in this ratio over time?

According to ICAO NAT doc 007 (North Atlantic Operations and Airspace Manual, edition 2014/2015) (PDF), approximately half of the North Atlantic (NAT) flight use the Oceanic Track System (OTS).

  2.1.3: It should be appreciated, however, that use of OTS tracks is not
  mandatory. Currently about half of NAT flights utilise the OTS.
  Aircraft may fly on random routes which remain clear of the OTS or may
  fly on any route that joins or leaves an outer track of the OTS. There
  is also nothing to prevent an operator from planning a route which
  crosses the OTS. However, in this case, operators must be aware that
  whilst ATC will make every effort to clear random traffic across the
  OTS at published levels, re-routes or significant changes in flight
  level from those planned are very likely to be necessary during most
  of the OTS traffic periods.

Note that not all flights in the NAT do cross the Atlantic from East to West or vice versa. For example:

Flights from Northern Europe to Spain / Canaries / Portugal and v.v.
Flights from Portugal to the Azores and v.v.
Flights from Iceland

And then there are a number of fixed routes that allow aircraft that do no meet the minimum navigation performance requirements to cross the ocean. These tracks do not change with the daily winds like the OTS tracks.

All these are included in the 'about half'

But especially in the Northern part of the NAT airspace, covered by the Reykjavik FIR there are many random routes. According to the website of Iceavia:

  In 2010, 92.3% of the traffic in the Reykjavik CTA was on random
  tracks and 7.7% was on the NAT tracks.

But that is mainly because the OTS tracks are usual south of the Reykjavik FIR.

That same page says:

  In effect, where the preferred track lies within the geographical
  limits of the OTS, the operator is obliged to choose an OTS track or
  fly above or below the system. Where the preferred track lies clear of
  the OTS, the operator is free to fly it by nominating a random track.
  Trans-Atlantic tracks, therefore, fall into three categories: OTS,
  Random or Fixed.


How is that there is no leak through the fuel vents during aerobatics maneuvers? Can anyone tell me how aircraft such as jet fighters and stunt planes design the fuel tank vent system to prevent fuel leaking through the vents when performing aerobatics, 360 flips and complex maneuvers?
Surely jet fighters don't just let it leak out?

There are 3 common solutions,

1) do nothing, unless the airplane is flown for an extended period of time inverted, there will be no appreciable vacuum created from fuel use and the vent is so small that there will not be appreciable fuel loss.

2) point the vent into the slipstream giving a ram air effect.

3) use two vent tubes (can be mounted either top & bottom or same side), at least one extends to opposite side of the tank.

This picture is for RC or drone aircraft but the same principle is used for full scale aircraft.


Is there a database of radio-frequencies for airfields/airports in Europe? Is there something like a register of frequencies for airfields/airports in Europe? I am building a VFR flight planner and would be interested to autofill a form with the frequencies dependent on the given input data. Is there something like a database?

Try https://www.ead.eurocontrol.int/eadcms/eadsite/index.php.html . It is not a database but you have access to all AIPs from members of Eurocontrol .


Why does spoiler extension during touchdown cause a pitch up moment? There are reports that incorrect flight technique associated with spoilers extension during touchdown were contributing factors to pitch increase after landing, causing tail strikes in jet transport aircraft.
Why does the spoiler extension causes a pitch up moment in the aircraft after touchdown?

Pitch-up upon spoiler deployment would occur if the spoilers are positioned aft of the center of lift of the wing when in its landing configuration. In this case, the spoiler kills off lift on the aft portion of the wing while the leading side of the wing (in front of the spoilers) is still generating lift. The lift generated by the portion of the wing in front of the spoilers is then not balanced by lift generated by that portion of the wing behind the spoilers, producing a net upwards pitching moment.


When flying a glider in emergency situation, would it be more safe to bailout or to land in a forest? Is there any consensus when it comes to this question? If it depends then it depends on what exactly? I'm interested in the decision making in this kind of situation.

Thankfully, I never had to make this choice. In my training I learned to stay in the plane and flare at the height of the treetops, then let the plane sink into the branches and have them stop and suspend the aircraft. The fuselage is quite effective as a protective shell, and up on top the branches are thin and flexible.

Use the parachute only to hoist yourself down from the stricken plane, if necessary.

Two-seater after landing in trees at Boberg glider port (picture source)


What does it mean "the airport has the code A 129" (Nida airport, Europe)? It has been announced that Nida airport (Lithuania) officially opens again and obtains the code "A 129" (here). The source does not say that kind of code it is and what does it mean. Would it be possible to clarify? Is it a place designation, or the airport category?

Nida airport has been closed for many years. It is not very tiny, passenger planes used to land there many years ago. Recently it has been reopened for very small planes while probably something bigger would be able to land there as well. Basically this rather long runway has the status of untowered airstrip.

Nida airport has ICAO code EYND and no IATA code.

This is really just an educated guess, but it sounds like it was assigned that identifier by the Lithuanian civil aviation authority. It obviously didn't warrant an IATA code. Since it was closed to most traffic the ICAO code may not have been in use. The wiki page said it was just considered an "airstrip," so it was assigned an ID by the government. (It also mentioned lack of fuel service. That might be a requirement for an ICAO registration. I don't know.)

Here in the US large airports will have an IATA CODE, an ICAO code and an FAA location ID. [example: O'Hare airport - IATA: ORD - ICAO: KORD - FAA: ORD] A small GA airport won't merit an IATA or ICAO code but it will have an FAA location ID. The small airport near where I work has no IATA or ICAO code. It has the FAA location identifier K68.


Why are cockpit voice recorders limited to 2 hours recording? With today's technology in memory storage, where simple voice recorders can record virtually endless durations, why are CVRs limited to only 2 hours. Is it the eternal "cost vs benefit" reason?

Wouldn't more recording provide greater insight to investigators in case of any disaster?

Aviation manufacturers generally design the equipment to comply with legal requirements. Under FAA two hours is what is required by law.

14 CFR  121.359–Operating Requirements:  Domestic,  Flag,  and Supplemental  Operations–Cockpit  Voice  Recorders
(i)  By  April  7,  2012, all  turbine  engine-powered  airplanes  subject to  this  section  that are manufactured  before  April  7, 2010, must  have  a  cockpit  voice  recorder  installed that  also—
(1)  Meets  the  requirements  of  §23.1457(d)(6)  or  §25.1457(d)(6)  of  this  chapter, as  applicable;
(2)  Retains  at  least  the  last  2 hours  of  recorded  information using  a  recorder  that  meets  the standards  of  TSO-C123a,  or  later  revision;  and
(3)  Is  operated  continuously  from  the  use  of  the  checklist  before  the  flight  to completion of  the final checklist at the  end  of  the  flight.
(4)  If  transport  category,  meets  the  requirements  in §25.1457(a)(3),  (a)(4),  and  (a)(5) of this chapter.
[The following section has the same requirements for aircraft manufactured after April 7, 2010.]

The flight data recorder is required to retain 15 hours worth of data.
FAA allows pilots to erase anything on the CVR recorded 30 min (in some cases 15 min) prior. This is probably something that was negotiated between the NTSB and the pilots union to protect the pilots' privacy.  Since it's written into the statute that way I assume modern digital CVR'S must have a function to erase everything but the last 30 min. (@OSUZorba there's that word again)

14 CFR  121.359 (f)  In  complying  with this  section, an approved  cockpit  voice  recorder  having  an  erasure feature  may  be  used, so that  at  any  time  during  the  operation of  the  recorder, information recorded more than  30  minutes  earlier  may  be erased  or  otherwise obliterated.

This was most likely in response to the 1979 incident that occurred on TWA flight 841 where the pilot was accused of improperly extending flaps during cruise but had erased the CVR when they landed,  so they had no proof. At the time CVR's were still fairly new and pilots balked at having their conversations recorded for privacy reasons, so it was common practice to erase it after each flight. There is still some concern over privacy issues since in some situations the recording can open the pilot up to legal liability.
There are really only a handful of cases where a longer recording would have been useful, most of which involved pilot incapacitation. In 2014 EASA proposed extending the requirement. The European Cockpit Association, which represents pilots released a position paper .pdf stating that they would only support the extension if there were also systems in place to ensure that only the pertinent portions could be used and any other conversation could not be leaked to the public or used in jurisdictions where there are no legal requirements to maintain pilots' privacy.

ECA  stresses  the  following:

Pilots  submit  to such  recording  under  the  strict  condition  that  the  CVR  data is  to be  used exclusively by  accident  investigation authorities in  the  context  of  their  safety  investigations.  Pilots  are  one of  the few  professions  that  agree  to  being  recorded  at  their  workplace  and  the  consequent  infringement  of their  privacy

National  and  European  legislators  recognise  the  need  to  protect  CVR  recordings  (Reg.  996/2010). However,  despite  various  legal  provisions  at  EU  and  national  level,  as  well  as  best  practices  in many  airlines,  CVR  data  or  their  transcripts  have  too  often  leaked  to  the  public  and  media , exposing  data  with  private  and  personal  content  –  sometimes  the  last  minutes  of  the  crews’  lives  – to  a  wide  audience,  generating  speculation,  interpretations  and  apportioning  blame  –  in  a  way  that may  be  far  removed  from  what  actually  happened,  what  contributed  to  the accident  and why.

This  inappropriate  use  and  distribution  of  sensitive  CVR  data  beyond  accident  investigation agencies  negatively  affects  Just  Culture  and  the  safety  improvement  efforts  in  Europe.  Extending CVR duration would increase the  quantity  of  data  available for  misuse  significantly.

Leaking  of  CVR  data  results  in speculation that  increases  the  pressure on  accident  investigators,  on the  judiciary  to  act  quickly  to  hold  accountable those  ‘responsible’,  and  on  other  authorities  or  public figures  to  come  up  with  quick  answers,  rather  than  waiting  for  the  Final  Report  to  be  published  and generating  mature  safety  improvements.

Increasing  CVR  duration  would  also  increase  the  data  that  is  potentially  available  to  the  airline management.  While   many  companies  in  Europe  have  internal  procedures  –  and  sometimes agreements  with  the  pilot  representatives  –  in  place  to  ensure  sensitive  data  is  not  misused,  this  is not  the  case  for  all  companies.  Hence,  an  increased  recording  time  –  combined  with  very  powerful digital  storing  facilities  and  the  possibility  to  cross-check  CVR  and  FDM  data  –  would  also  increase the  scope  for  (un)intentional  (ab)use  of  such  data  by  company  management  for  other  than  safety purposes  (e.g.  any  form  of  disciplinary  measures).  Although  this  would  not  be  in  line  with  EU legislation,  not  all  airlines  are  as exemplary  as  some,  and not  all  legislation is adequately  enforced.

Increasing  CVR  duration  on  European aircraft  also increases  the  risk  of  CVR  data being  used  –  and potentially  made  public  –  by  non-European  authorities,  which  are  not  bound  by  EU  legislation  and the  protections  contained  therein.  This  is  the  case  especially  for  long-haul  operations  (at  which  an increase  of  the  recording  time  is  actually  aimed)  where  the  majority  of  the  flight  is  outside  Europe.  If an  accident  happens  outside  Europe,  the  national  safety  and  judicial  authorities  will  be  entitled  to seize  the  CVR  and  will  be  bound  by  their  own  local  laws,  by  local  political  considerations,  and general  public  pressure.  –  This  would be  an  unintended  –  but  very  real  –  consequence  that  must  be taken  into  account.


Why do blimps have fins? Why do blimps have fins? Can't the two (or so) engines already control direction?

What if the engines fail? In early airships this happened frequently, and many ships limped home on a reduced number of engines.

Note that all airships were both vertically and laterally unstable. The helmsman had to continuously adjust the rudder angle to keep the ship on course. In NACA TN 204, Frank Rizzo concluded that enlarging the fins would be beneficial, and reducing them would be unwise. They were just as large as needed to control the ship, but not sufficiently large to give it static stability.

Static stability in aircraft means any attitude change creates forces which return the craft to its old attitude. In airships, several types of static stability must be observed:

Buoyancy: If the ship rises or sinks, the rate of cooling of the atmosphere and the gas in the hull might differ. If the cooling rate of the atmosphere (lapse rate) is above the adiabatic rate, the ship is unstable.
Pitch attitude: If the ship pitches up or down, the lifting gas will shift towards the highest point, and the heavier gas in the ballonets will shift to the lower point, creating an unstable pitch condition.
Directional stability: When moving forward, any heading change will cause a side force which is centered at the forward hull and pushes the ship further off course. The fins create a counteracting force, but due to their size this force is too small to turn the ship back. Only by adding rudder the helmsman can keep the ship stable.
Longitudinal stability: In a similar way, pitching the ship up or down while in motion will create a destabilizing force on the forward hull which is mitigated, but not eliminated, by the horizontal fins. Elevator deflection is necessary to keep the ship at the desired pitch angle.
Roll stability: Since the center of gravity is below the center of buoyancy, the mass of the gondola will pull an airship right side up. This is also valid when flying turns: Then the gondola will roll the ship into the turn such that a rudder command into the turn will also cause a nose-down pitching moment. Now all control surfaces need to be coordinated to keep the nose of the airship up.

Note that only the first and last type of static stability are ensured, and the first only for special atmospheric conditions! The other three are lacking!

Zeppelin airships used two helmsmen, one for directional and one for pitch control. Due to the size of the ships any movement was very slow, so the task of keeping them on course was easier than it might sound. However, taking any of the fins away or even reducing their size would had made the ships uncontrollable.


How are METARs published? I use https://flightplanning.navcanada.ca to get METARs and TAFs for my local stations. While listening to CYPK tower at work I noticed something in the header of my VLC:

That's a METAR! But why doesn't it show up at NAV CANADA?

That got me wondering where those reports/forecasts actually come from. After the station observes weather, does it report it to a central service? Does the station itself predict the future conditions to create the TAF?

METAR

The METAR always refers to a specific airport and is obtained right then and there. That is at the airport.

It is a report of current conditions, usually hourly.

In the US, the FAA polls all systems remotely and disseminates the reports in METAR format. No word on wether this is via phone, mobile or radio, if that is what you are asking.

In Germany, the DWD, the german weather service, provides the reports. It can be assumed, that the situation is similar and that the stations are polled.

Weather stations have wide-ranging capabilities and operators, so the reported parameters may be different.

METAR reports may be reviewed by an individual before being transmitted, but the vast majority are reported automatically.

METAR reports are used for aviation weather, by definition, as a "Meteorological Terminal Area Report".

TAF

The TAF is a forecast. It is updated only 4 times a day and is provided by a human forecaster on the ground. Most larger airports have a meteorologist.

FORMAT

Both METAR and TAF use similar format, but each contains elements distinct from the other.  For example, a TAF may contain a FM (from) or BECMG (becoming), but a METAR never will.

DATA SOURCES

You can use https://www.checkwx.com/ to check both.
Or http://tgftp.nws.noaa.gov/weather/current/ if you want the raw data.


What are the handling effects of converting a dihedral wing to polyhedral? I'm looking at plans to build a radio controlled (RC) glider that is launched by rocket boost mainly as a park flyer. I've been given a set of plans for a model that is a dihedral wing (see attached photo), and I am thinking converting it to a polyhedral wing, as I read that polyhedral wings are more stable for people new to flying as I am.

The new wing shape (I haven't drawn it out yet), would have a flat section over the fuselage acting as a partial cover for the rc components, then a 6 degree angle from there to mid point of the wing, and then another 6 degree angle to the tip.

Wing length and total angles/measurements would be the same, as would the airfoil (Which can be seen in the rib segments on the plan). My other option is simply adding the central flat fuselage cover section, and leaving the rest of the wing as is. (One note, the reason for the thinning of the rib sections in the front is that it is a partially built wing, there is a balsa skin over those parts, then the entire wing is coated in a lightweight monokote type material).

Is there any value in making this change to a polyhedral wing, or is it mostly a wasted effort that I shouldn't worry about doing?

Wing section (I have full plans if other angles are desired):

In terms of in-flight behavior, the biggest change between dihedral and polyhedral (or tip dihedral) with the same overall stability is more roll response for a given yaw input -- this occurs because yaw-induced roll is caused by the skid presenting the outside wing at a higher angle of attack than the inside, and this effect is both more pronounced, per area, with the sharper angle of a tip dihedral or polyhedral tip panel, and is applied further from the centerline, so has a longer lever arm.

I'd agree, however, with the advice in another answer, not to modify your first kit.  Build to plans and instructions.  If you want to compare, get the kit built and the model flying correctly, then either buy another kit or buy materials (make photocopies or scans of the ribs and tip plates) and build another wing -- then you can compare the in-flight behavior for yourself.


Are aircraft pilots required to fly runway heading for a certain distance? If an aircraft rotates off the runway relatively quickly (runway mid-point for example), do pilots need to continue on the runway heading for a minimum distance before turning based on departure procedures? For example, for the Runways 31L/R CANARSIE climb at JFK, the established departure procedure is "Climbing left turn direct CRI VOR/DM". For this same procedure, can the departing aircraft proceed direct to CRI VOR/DM like the image below, if safely possible, or do they need to maintain runway heading till the runway is cleared?
Thanks!

The initial turn should be made at 400 feet AGL.
Unless otherwise specified in the departure procedure, the initial turn should be made when reaching an altitude of 400 feet above the runway elevation as specified in the AIM:

Unless specified otherwise, required obstacle clearance for all departures, including diverse, is based on the pilot crossing the departure end of the runway at least 35 feet above the departure end of runway elevation, climbing to 400 feet above the departure end of runway elevation before making the initial turn, and maintaining a minimum climb gradient of 200 feet per nautical mile (FPNM), unless required to level off by a crossing restriction, until the minimum IFR altitude. A greater climb gradient maybe specified in the DP to clear obstacles or to achieve an ATC crossing restriction. If an initial turn higher than 400 feet above the departure end of runway elevation is specified in the DP, the turn should be commenced at the higher altitude. If a turn is specified at a fix, the turn must be made at that fix. Fixes may have minimum and/or maximum crossing altitudes that must be adhered to prior to passing the fix. In rare instances, obstacles that exist on the extended runway centerline may make an “early turn” more desirable than proceeding straight ahead. In these cases, the published departure instructions will include the language “turn left (right) as soon as practicable.” These departures will also include a ceiling and visibility minimum of at least 300 and 1. Pilots encountering one of these DPs should preplan the climb out to gain altitude and begin the turn as quickly as possible within the bounds of safe operating practices and operating limitations. This type of departure procedure is being phased out.

(AIM 5-2-6 Departure Procedures, emphasis mine)
The Canarsie climb at JFK does not include any special instructions for when to make the turn:

CANARSIE CLIMB: Climbing left turn direct CRI VOR/DME. Make turn east of
CRI R-039 (remain within JFK 4.5 DME), then via CRI R-176. Cross CRI 2 DME
or JFK R-253 at or above 2500, thence . . . .

(Kennedy Five Departure)
I would therefore start the turn at 400 feet. In principle, this would allow turning before reaching the far end of the runway, but only for a very good climb performance or a very long runway.


What are the differences between the SR 71 variants? I read that all SR 71 blackbirds were different, what was different with each one and is one regarded as superior to the rest? Why?

Like every military aircraft built over the years, the aircraft evolve.  So to address the aircraft's history and all variants, let's refer to it as the Blackbird.

The Blackbird started out as the A-12 procured for the CIA. Fifteen of these were built with one being a 2-seat trainer. Two of the 15 were modified into M-21 aircraft prior to delivery.  The M-21 was designed to launch the D-21 drones. The SR-71 at the Intrepid museum (60-6925) in New York was built as an A-12.  One of the M-21's is at the Museum of Flight in Seattle with a D-21B drone.

Three high-speed interceptor prototypes were built and designated as the YF-12A and were capable of carrying 3 air-to-air missiles.  Two crashed and the third is at the National Museum of the AF.

The interceptor was cancelled and the RS-71 program, renamed SR-71 after LBJ's misstatement at the press conference, went forward for the AF.  Twenty-nine SR-71A's were built along with 2 SR-71B trainers.  When one of the trainers was lost in 1968, the surviving aft part of one of the crashed YF-12A's was mated to the front part the SR-71 static test aircraft to create the sole SR-71C.

There's a huge Blackbird community online.  Detail specs and history are available at blackbirds.net and at SR-71 Blackbirds.

The question of which is superior is an opinion, but one can assume that the SR-71's were "better" than the A-12's as they came later building on what was learned from both the A-12 and YF-12A.


How do you visually identify aircraft from the ground? Are there any good resources that teach you how to identify jetliners from the ground? I'd love to see some great comparative photos of their silhouettes. Books or websites are both ok.

For example, here's a plane that was flying over yesterday en-route to KSFO. I'm guessing it's a 747 or A380, but I can't easily guess from this angle.

The canonical reference for aircraft recognition would be Jane's All the World's Aircraft.

http://www.airliners.net is also a useful resource, but generally means working from photos - the line drawings in Jane's are often easier to use because they abstract away things like airline liveries and distill the aircraft down to its basic shapes.


Is there an efficiency measure for airports? For large, busy airports (such as JFK), how do they measure how well they are being utilized? I assume airport management wants to serve as many flights as possible, for maximum revenue. Any time their gates are empty, or runways aren't being utilized, the airport has more capacity to sell. Is there some sort of industry standard measurement for "airport utilization efficiency"?

The Air Transport Research Society (ATRS) has a benchmarking system for determining the efficiency of the airports.

Basically,it takes the airport size and related infrastructure (runways, no. of gates etc.) as inputs and measures the airport efficiency in terms of aircraft and passenger movement,revenue etc.

There is a yearly Global Airport Benchmarking Report.


How do airliner manufacturers come up with typical capacities of their planes? Instead of providing the maximum capacity of a particular model, airliner manufacturers often provide official typical capacities, like 280-366 seats for A350 series and 350/400seats for Boeing 777x series.

The question is: How do they generate this number?

These numbers are based on mixed-class configurations and use of floor space for other things. The A380 for instance can theoretically be configured with 853 "economy" seats, but no-one I know of has bought one configured that way. Typical first-business-economy configuration is 525, and Emirates seats just 489 because its first-class section is basically staterooms, and it has showers and a bar taking up floor space (it also has an excellent and large business class instead of using the back half of both decks for coach).

When designing an aircraft's seating capacity, especially for long-haul flights, total cabin weight (passengers and cargo) must be taken into account. The more stuff you're hauling, the less weight allowance you have for fuel, and therefore your range is reduced. Therefore, increased room per passenger on long-haul flights isn't just for passenger comfort, it's often a necessity to reduce total cabin weight and thus be able to max out the fuel load to get between the airports non-stop. Operators of shorter flights don't care as much because you can pack them in like sardines and still have plenty of fuel to get them where they're going.

Therefore, dimensions of various classes of seat differ by airline, aircraft and route (Lufthansa, for instance, operates three different A380 configurations based on the routes they run). The typical coach seat is between 17 and 19 inches wide (including half the armrest), and has a "pitch" (space between seats which determines the legroom and ability to recline) of between 31 and 35 inches.

For business class in three-class planes it gets a bit better; seat width averages about 21" and a pitch of about 38" (more for planes outfitted with lay-flat seats). First class ranges widely by aircraft type and airline (it's truly "first-class" in aircraft with three-class configuration; in two-class what's called "first" is closer to business class), but typically offers room to spare especially on long-hauls.

Coupled with required/desired aisle widths and additional amenities that widen the seats or replace them in certain areas of the cabin, it's fairly academic to count up how many seats you can fit aboard a particular airframe.


Where can I find US ARTCC sector boundary coordinates? For an academic purpose, I would like to map US airspace using GIS tools with coordinates. I found the airspace boundary coordinates from the eNASR, but no luck with the sector boundaries.

Any information you can provide me would be greatly appreciated.

For any ARTCC you can contact their Airspace and Procedures office. Be polite, and specific. They will have that information. It should be publicly available. The cities for the lower 48 where ARTCCs are (associated city name and actual location)
Albuquerque (NE side of town) 505-856-4500
Atlanta (Hampton GA you should hear it when the speedway fires up) 770-210-7600
Boston (Nashua NH) 603-879-6633
Chicago (Aurora IL) 630-906-8200
Cleveland (Oberlin OH) 440-774-0300
Denver (Longmont, my facility, tell 'em CD from training sent ya) 303-651-4100
Fort Worth (north side of DFW airport) 866-835-5322
Houston (just south of airport) 281-230-5600
Indianapolis (at the airport) 317-247-2234
Jacksonville (Hillyard FL) 904-845-1500
Kansas City (Olathe) 913-254-8400
Los Angeles (Palmdale) 510-745-3000
Memphis (NE of airport) 901-368-8101
Miami (North Miami in a warehouse district...) 305-716-1500
Minneapolis (Farmington MN) 651-463-5514
New York (Ronkonkoma) 631-468-1001
Oakland (Fremont) 510-745-3000
Salt Lake City (airport) 801-575-2400
Seattle (Everett WA) 866-835-5322
Washington DC (Leesburg VA)703-377-3401
These numbers are for their respective switchboards, select "Airspace and Procedures" from the menu.


With an EASA PPL, can I invoice my mother's company for airplane rental to fly her to a convention, with no other renumeration? My mother who owns a private company asked me if I could fly her to a convention. She asked if it was possible if the costs of the plane rental could be invoiced to her company. Since I only posses a PPL (EASA) I was wondering if I was allowed to perform this flight since you're not supposed to do commercial flights. I won't get paid anything for this flight so I don't think there would be a problem but just want to make sure.

In the UK, at least, the rules specifically state:

  Privileges and limitations:
    A holder of a PPL may, for compensation or hire, act as a crewmember of an aircraft in connection with any business or
  employment if—

  a. the flight is only incidental to that business or employment; and

  b. the aircraft does not carry passengers or property for compensation or hire.

Despite what this may sound like, this means you are not allowed to be paid for flying unless you happen to be an employee and flying for work -- e.g. an archaeologist (with a salary from University X) flying yourself and a colleague to a dig site (while employed at the University of X -- thus flying for compensation [because you are paid, indirectly, to do this] but incidental to the employment [the University of X is not an airline, and the colleague you are with is not a co-pilot or paying passenger]).

I have always been taught that the safest thing to think is this: As a PPL, you cannot fly for compensation, and each of your passengers at most has to contribute not more than their "fare" share of the cost of the flight.

By invoicing your mother for the cost of the plane rental you would not be contributing that value in kind, and thus would be in violation of this rule (with rather unpleasant consequences, should you be caught -- ranging from losing your license to a minor criminal conviction). Moreover, the fact that you mentioned the word invoice makes me think that your mother's company would be expecting you to provide a service -- all of these are commercial terms, and alarm bells would be ringing in the mind of any examiner looking at this from the outside, as it starts to really sound like you're providing a service for hire.

Ignoring for the moment that many organisations have rules about doing just the following with family members, I suggest instead keeping all of the receipts of your legitimate expense for aircraft hire -- Hobbs hour fees, fuel, landing, whatever -- and then getting your mother to claim exactly half their value as a business expense. That at least makes it very explicitly clear that you are paying your fair share of the cost of the actual flight, and highlights the nature of the compensation as covering an expense, not a fare.


What are the standard stability derivative formulas and typical GA values? What are the standard stability derivative formulas and typical GA values?

I suppose values for the C172 would be the best benchmark.

I don’t have it in front of me, but this book has the pertinent derivatives to consider, along with C172-ish values.

Aerodynamics, Aeronautics, and Flight Mechanics, 2nd Edition
Barnes W. McCormick
ISBN: 978-0-471-57506-1 September 1994 672 Pages


Where can I get airport diagrams of non-towered airports? I'm trying to find a couple of airport diagrams for right now: X26 and X59.

Neither of them are listed in the Chart Supplement or on the FAA site.
All I could get were those shabby diagrams presented by Airnav and Skyvector and sorts, and Google Earth images, both of which are not current. (The runway numbers are different from what are actually designated (painted) and used.)

Does anyone have a better idea about where to find the airport diagrams?

Plus, what the heck is the order of those airport diagrams listed in the Chart Supplement?! I couldn't find any rules.

Many non-towered airports have diagrams in the Chart Supplement, and there is an airport diagram for X26 but not for X59. The difference appears to be that X26 has instrument approaches but X59 doesn't. It looks to me like the airport diagrams are considered part of the terminal procedures.

But I have to say that the FAA is as clear as mud on this. The airport diagrams legend says:

  selected towered airport diagrams have been published in the Airport
  Diagram section of the A/FD

But obviously that's completely wrong, because a) many non-towered airport diagrams are in there, and b) the A/FD doesn't exist any more.

By inspection, it looks to me like airports without an instrument approach have no airport diagram (X59, X25, 2RR) and ones with an approach do have one (X26, X07, AVO). But I only spent a few minutes looking, so I may well be completely wrong on this.

As for your question about the order of diagrams, the legend says:

  Diagrams will be listed alphabetically by associated city and airport
  name


How many airport charts do airline pilots have in the cockpit? I always wonder how many "backup" approach charts and airport diagrams airline pilots have in case the plane has to divert. I imagine a few possibilities:

There are no approach charts in the cockpit. The only ones the pilots have are those with the flight plan: the departure, destination and any alternates they picked along the route. If the plane must land somewhere else, the pilots will ask ATC to guide them in.
All of the fleet's destinations are available in the cockpit. If the plane diverts to any one of these airports, it is likely that there will be a ground crew to serve the passengers.
Every airport that can accommodate the size of the airplane is available, irrespective of whether it is a destination of one of the airline's routes.
Every airport within the operation area, no matter how big or small, is available.

I imagine with more airlines using Electronic Flight Bags, this would be a non-issue as one can easily load all available charts in the world onto the tablet, and updating them is trivial. Still I am interested in knowing what airlines typically do.

In the 1990s I flew for two 747 carriers, the first primarily a freight carrier and the second primarily a passenger carrier. Both used Jeppesen for their airway manuals, and both supplied each pilot with a single, full-size and very full Jepp manual that contained as many as possible of the airports we might go into. Image below:

As I remember, the criteria for whether a plate would be in our personal binder included the airport having a runway at least 5000 feet long.

Both carriers did extensive charter work to every continent save Antarctica, and we would occasionally be dispatched to an airport that our personal Jepp manual didn't have. The freight carrier handled this problem by having aboard each aircraft a flight bag with full, world-wide coverage, 5 or 6 manuals as I remember. In theory the manuals were kept current by updating them each time the aircraft went through its base, but in practice they were almost always out of date, but at least they were there in case of an inflight diversion to an unplanned airport.

The pax carrier handled the problem of an airport not in our personal coverage by faxing the plates with our flight plans. In case of an unplanned inflight diversion, dispatch would read the pertinent information to us over HF, a very tedious procedure, obviously. I only had that happen once.

It was a different world back then with no ubiquitous Internet. I typically spent 300 to 400 dollars per month in international phone calls to my wife. No Skype, no WhatsApp, Compuserve for email until around 1996 or so, then sporadic Internet, but always dial-up and with ridiculous charges by the hotels.


How does change in aircraft's weight equal fuel mass flow rate multiplied by 'g'? Can someone help me understand how does
$$\frac{dW}{dt} = -\dot{m}_f \cdot g ,$$
where $\dot{m}_f$ is fuel mass flow rate.
This is the first equation laid down in the Breguet range equation derivation.
Here's where I encountered it. Alternative accessible source (link):

In the SI system the weight is measured in Newtons [N = kg*m/s^2], while the mass is measured in kilograms [kg].
To convert kilograms in Newtons, i.e. a mass measurement in a weight, you multiply by the acceleration of gravity g.
In this case you're converting a change in mass to a change in weight, the conversion is the same, but both sides have an additional time component in the denominator due to the derivative.
Given your comment, it seems you're confused by the good old mass-vs-weight thing. Let's have Wikipedia:

In common usage, the mass of an object is often referred to as its weight, though these are in fact different concepts and quantities. In scientific contexts, mass is the amount of "matter" in an object (though "matter" may be difficult to define), whereas weight is the force exerted on an object by gravity. In other words, an object with a mass of 1.0 kilogram weighs approximately 9.81 newtons on the surface of the Earth, which is its mass multiplied by the gravitational field strength. The object's weight is less on Mars, where gravity is weaker, and more on Saturn, and very small in space when far from any significant source of gravity, but it always has the same mass.


Can you become a CFI with only a PPL (EASA)? In Europe, can you get your CFI rating with a PPL only or do you need a CPL?

I assume that if you get paid to do flight instruction it's considered a commercial activity, so you'll need a CPL. But what if you do instruction without getting paid, do you still need a commercial licence to be a CFI?

The EASA requirements for a CFI ticket are:

Over 18 yo
Hold a Commercial Pilot License or a Private Pilot License with the CPL theory done.
A minimum flight experience of 200 hours as a Pilot of which 150 will be as Pilot in Command
Hold a Medical Certificate Class I or II in accordance with
the license


How is heavy cargo secured in military cargo carriers? Some big military cargo carriers carry tanks and other heavy equipment and I am not sure if they have some kind of special locks or tie-downs in the cargo space to manage those heavy loads.

How are these very heavy loads secured?

The cargo in a military aircraft are secured in the cargo hold using chains, straps etc. connected to stowage tie-down devices, which go into tie-down rings . The following image shows a M1 Abrams tank secured in C-17 Globemaster III using tie-down devices.

USAF uses three different types of devices to secure cargo in aircraft, which vary in their load capacity:

MB-1 tie-down device with 10,000 lb rated capacity.
MB-2 tie-down device with 25,000 lb rated capacity.
CGU-1/B tie-down device with 5,000-pound rated capacity

The MB-1 and MB-2 are similar in their form and function, with the only difference being their load capacity.This image shows a close-up of the MB-1 and MB-2 tie-down devices:

"C-17 Globemaster III no. 5139 stowage tiedown devices" by BrokenSphere - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons.

The hook goes into the tie-down ring, while on the other end, straps or chains (from the cargo) go.

The CGU-1/B is a 20-foot nylon web strap with two metal hooks at both ends. While one hook is stationary, the other hook has a ratchet device and can be moved and tightens the device when it is being used.

Note: Apparently, Military designation system refers to MB-1 and MB-2 as CGU-3/E and CGU-4/E respectively.


What are the benefits of long-haul airplanes servicing regional routes? Following this answer. This is actually a set of three different questions:

How often airlines "wastes" money, by putting long-hauls (widebody aircrafts) on regional or domestic routes?
Are there any (economic?) arguments for doing so (except special cases: like no other kind of replacement for broken small plane)?
Is there any example of any regional route, that is served by long-haul on regular basis?

But, I think, that all of them can be answered with one, quite simple answer.

TL;DR You're confusing concepts, planes come in high/low capacity and range, routes come in high/low demand and long/short haul distances. A high capacity long range aircraft can operate very profitably on a short haul, high demand route... a full 747 would actually be more profitable on a 1000km route than a full 737, because although the 747 uses more fuel, it also carries a lot more passengers.

You're assuming that putting a big plane on a short route wastes money. Airlines don't work in miles per gallon like you or I do with their car... they work on income/expense. I could fly 747s on 100 mile hops all day, but if they're full of 400+ passengers each paying more than 0.25% of the running costs of that flight, I'll still make money.

If they could have used a smaller aircraft, it might waste a
little money carrying the extra weight, but you seem to be
over-simplifying things

I'm guessing this question is actually more along the lines of "How often do airliners run an aircraft that isn't completely full, and how much of that time could they have actually run a smaller aircraft?" To which the answer is "Usually, and not very often"
The economics are about running the whole system as a profit. If I have enough flights in summer that fill the aircraft, then over 12 months that bigger aircraft (highly profitable all summer, breaking even all winter) may make all money than a smaller aircraft making a small profit all winter, and a small profit all summer, but not being big enough in summer to take the entire potential demand.

Essentially, though, airlines are in the business of getting the "best fit" for their fleet. They aren't trying to get a plane in every size to have the perfect profit ratio for each flight, they are trying to get a suitable plane on each flight. This involves moving planes around as routes change etc. In an ideal world you'd run each plane exactly full of every passenger who wanted to fly on that route. In reality, we probably want a plane which is just slightly bigger than that, to cope with the small amounts of extra demand
Again you're seeing "Long haul" and "Short haul" aircraft as different concepts. They aren't. There are only high/low capacity aircraft and high/low capacity routes. Long haul routes tend to have less frequent service with larger, higher capacity aircraft (if you're travelling for 18 hours, you don't need a service with departures every 3 hours). They also tend to involve people travelling from "The UK" to "Australia" for example, so one big plane can cover all of that, and split to smaller aircraft to disperse them

Short haul routes tend to have more regular service and smaller
demand levels, partially because people are less likely to want to depart at the same time every day, and partially because they can be more fine grained - you can go from an area of one country to an area of another.

What you seem to miss is that these things are not mutually exclusive... with enough demand, larger aircraft can run short haul routes very profitably. The fact a 747 is usually profitable on long haul flights, and the fact the demand on short haul routes do not usually have enough demand for such a large aircraft, don't mean that one could never be profitable if enough people wanted to fly on it. There are airlines using 777s for example for fairly short haul journeys, very profitably, all over the world.


How is the phraseology of IFR clearances different between the US and Europe? In this question, a comment says that the phraseology of IFR clearances is very different between Europe and the US:

  especially the VFR phraseology (but not only) is really different in
  europe and the US. If we just take the IFR clearance into
  consideration the differences are huge

What are those differences, at least the main ones?

It's not only the IFR clearance, in Europe (where ICAO regulations are used everywhere) the phraseology is very different to the one in the US.
In Europe the phraseology is clearer and easier to understand, in the US it's shorter, less formal but easy to misunderstand.

Some examples are:

  118.350
  FAA: one one eight point three five
  ICAO: one one eight decimal three five zero

  Holding over DKB:
  FAA: Hold over DKB to the west.
  ICAO: hold over DKB as published, FL90

To answer your specific question about the IFR clearance:
In America an IFR clearance would sound like this:

  American 590, Ft. Lauderdale clearance delivery, cleared to Atlanta Intl' Airport, ARKES1 departure, then as filed, climb via the SID, expect FL320 onezero minutes after departure. Departure frequency 126.05, squawk 5523.

According to ICAO (specifically german phraseology):

  American 590, Frankfurt Delivery, startup approved, cleared to Atlanta aerodrome via DKB8S departure route, flightplanned route, climb altitude 4000ft, squawk 1000

So to sum it up, what's different are the parts "flightplanned route", "climb via the SID", and the departure frequency. If it comes to vectored departures it gets even more different, as in the US the clearance just states "via radar vectors" whereas in Europe the whole vectored departure procedure is inside the clearance ("... via vectored departure, after departure runway 18 climb altitude 4000ft on runway track, passing 3300ft proceed direct DKB, flightplanned route, ...").


Why does X-Plane 11 show the SR-71 at 200 knots but Mach 3 at 80,000 ft? So I noticed on X-Plane 11, the SR-71 reaches Mach 3 at 80000 feet, but the equivalent airspeed is only around 200 knots. What explains this difference between the mach number readout and the EAS readout?

Edit: the reason I ask is because other questions such as How did SR-71 spy, flying at 80,000 ft and 3500 km/h? indicate the SR-71 flew at 1910+ knots at 80000 feet, but I'm not sure if this is with a conversion of some sort or not, i.e., is this simply a simulator problem or an accurate representation of airspeed and mach?

Indicated airspeed is derived from the measured total pressure and the static pressure, according to:

$$ V_i = \sqrt {\frac{2 \cdot (p_t - p_s)}{\rho_{SL}}} \tag{1}$$

At 80,000 feet, static pressure is 2761 Pa. Dynamic pressure as measured by a pitot tube, is measured after a supersonic shock wave according to the Rayleigh Pitot tube formula:

$$ \frac{p_t}{p_s} = \left[\frac{{(\gamma + 1)}^2 \cdot M^2}{4\cdot\gamma \cdot M^2 - 2(\gamma - 1)} \right]^{\gamma / (\gamma - 1)} \cdot \frac{1 - \gamma + 2\cdot \gamma \cdot M^2}{\gamma + 1} \tag{2}$$

with $\gamma = 1.4$ and M = 3, substituted in (2), gives $\frac{p_t}{p_s} $ = 12.06, so $$p_t = 12.06 * 2761 = 33\,290 ~\text{Pa}$$. Substitute this into (1) together with $\rho$ = 1.225 at sea level, and we get

$$ V_i = \sqrt{\frac{2 \cdot (33,290 - 2761)}{1.225}} = 158 ~\text{m/s} = 307 ~\text{kts}$$

In the order of magnitude of what the X-plane indicated airspeed indicates, a lot closer than the TAS: speed of sound @ 80,000 ft = 298 m/s, Mach 3 = 894 m/s = 1,738 kts


Why is the bypass ratio of a turboprop higher than turbofan? Whenever, I come across turboprop, the author always mentions that they have higher bypass ratio than turbofan but no one explains the reason for this.

So, is the bypass ratio higher due to higher disc radius of turboprop or is it due to less air flow through the core or the combination of both?

If it is only due to less air flow inside the core, then they can still have a higher bypass ratio in turbofan right? (Since advanced turbofan produce less noise due to the nacelle)

Bypass ratio is the ratio of the overall flow  to the core flow (which goes eventually through the combustion chamber). Overall flow is either the flow captured by the intake or going through the propeller disc. Even for piston aircraft it is possible to define a bypass ratio if you interpret the air which flows through the cylinders as the core flow.

A turbofan essentially uses a shrouded propeller of high solidity (or activity ratio) which helps to accelerate the flow through it as much as possible. It needs to produce the most thrust from the limited air volume captured by the shroud's intake. The limitation is needed to limit the tip speed of the fan and the overall size and drag of the shroud.

Propellers, on the other hand, accelerate a bigger flow by less and need to cover less of the propeller disc for doing this. To keep thrust constant, a bigger mass flow needs to be involved into the acceleration.

Plot of the thrust specific fuel consumption in lb of fuel per lb of thrust per hour of different engines over the logarithm of their bypass ratio (picture source).

A comparison is only sensible if we look at the same core component: If a turbofan and a turboprop share the same high pressure components. One example would be the Rolls-Royce/Allison 2100 and the Rolls-Royce/Allison 3007. Wikipedia gives the mass flow of the 3007 as 109 - 127 kg/s but gives no information for the 2100. Using the maximum flight speed of the Alenia C-27J of 167 m/s and its propeller diameter of 4.15 m, we can find a lower bound for the mass flow through one of its propellers if we make the heroic assumption that the maximum speed is reached in 25000 ft (7620 m) where air density is 0.55 kg/m³.

Mass flow through the propeller of one 2100 is at least 1242.4 kg/s or about ten times of what it is for the 3007. The mass flow though the core is the same because both engines share the same hot section. The static thrust of the 2100 is higher than that of the 3007 but drops more quickly with speed, so at high speed the 3007 produces more thrust.


How do modern avionics work without vacuum pumps or gyroscopes? I'm going to be taking my checkride soon on a Skycatcher 162. It has an all glass cockpit utilizing the Garmin G300, and its my understanding that it does not utilize gyroscopes or vacuum pumps for any of its instruments.

Seeing that if I were in something like a Cessna 172L, which uses both gyros and vacuum pumps for many of its instruments, questions such as "how does the attitude indicator work?" are fair game, I assume that the same questions are fair game for avionics like the Garmin G300.

The problem, I don't know how they work and its looking like the top google result for "garmin g300 gyroscope" returns a 404 error.

Also, do digital pitot/static systems work in essentially the same way as the old school ones in planes like the C172L? I'd hate to tell my examiner anything along the lines of "I have no idea".

If you haven't already done so, you should have a look at section 7 of the C162 POH. That section gives an overview of all the aircraft's systems and the information is at a good level of detail for a checkride (at least at the private level). The examiner isn't expecting you to explain how a ring laser gyro works, but he probably will expect you to be able to give an explanation like this (from the POH):

  AIR DATA, ATTITUDE AND HEADING REFERENCE SYSTEM (ADAHRS) AND MAGNETOMETER (GRS)

  The ADAHRS provides airplane attitude and flight characteristics
  information to the G300 displays integrated avionics units. The ADAHRS
  unit, located behind the instrument panel, contains accelerometers,
  tilt sensors and rate sensors that replace spinning mass gyros used in
  other airplanes. The magnetometer, located in the tailcone, interfaces
  with the ADAHRS to provide heading information.

  The air data portion of the ADAHARS compiles information from the
  airplane's pitot-static system to calculate pressure altitude,
  airspeed, true airspeed, vertical speed and outside air temperature.
  An outside air temperature probe, mounted on top of the cabin, is
  connected to the ADAHRS.

The G300 Pilot's Guide goes into more detail about the system's components (see Section 1), although it's still at a fairly high level.


What is the Scaling Factor in ARINC 429? I'm a newly appointed engineer in an avionics company and have been tasked with preparing a report on ARINC429. I understand most of it, and I certainly find it simpler that 664, but I still can't manage to wrap my head around what "Scaling Factor" is.
No resource on ARINC429 I have found goes into detail about this, and the best I could find is image below.

This is a screenshot from a link discussing the standard.

Could anyone please explain what this is trying to convey?

In the example you pasted, the value $1.5_{10}$ is being sent, which has binary representation $1.1_{2}$. The data is sent as an unsigned integer so some kind of multiplier needs to be applied. The value occupies 19 bits, at offset 11 within the packet itself being bit 0 of the data. The default multiplier is such that the "units" bit (ie the one representing $1_{10}$) is in bit 26 in the packet, that is the bit 16 of the value. You can see that in the first example, the lefthand $1_{2}$ is in bit position 16 (counting from 0 from right).

This allows only values up to slightly short of 8. Various scalings are applied to values, depending on the label, as this may not be a convenient range for the data conveyed. If a label conveys data in the range 0-6, then it is fine as is. If 0-65 must be conveyed by a label, then the value is shifted right four places (to give more space for the larger numbers, but with less precision). Which scaling is applied is determined by the label. If a negative number is possible in a type, two's complement is applied. The label definition determines the range of its various words.

You can see this example effectively repeated immediately with value $1.25_{10}$, which is $1.01_{2}$.


In helicopter's forward motion, how is the forward pitching moment taken care off? When the rotor disk is in the position shown by the dashed lines, the net Lift is at an angle. It should produce a forward pitching moment about CG (Center of gravity). That can cause the helicopter nose to go down with a further increase in the moment angle and further pitching. What stops/controls this from happening in the actual scenario?

It's a complicated answer, with many contributing factors in a multi-dimensional matrix. In a helicopter flying at forward speed, there are several stabilising stability factors and several de-stabilising ones.

Before the helicopter can fly at speed, it needs to take off in a hover.

The rotor provides the lift force to climb.
Gravity applies down force in the Centre of Gravity.
The rotor hub is hinged - one could picture the fuselage as hanging off of the rotor hub, like a pendulum.

From this answer, own work

In this situation, hinging freely, the CoG would move directly underneath the rotor hub without re-aligning the rotor - the helicopter would stay in place, and only the fuselage would tilt until the CoG is underneath the lift vector. There is a range of allowable horizontal CoG positions, which would result in a range of fuselage angles when climbing up in a straight hover. Of course, if the CoG is chosen excessively forward or rearward, this scenario would result in an impossible fuselage angle.
But the rotor hub hinge does transfer torque, from rotor to the mast and vice versa. The fuselage is not free to dangle underneath the hub. From Prouty, Helicopter Performance, Stability and Control:, describing behaviour in a vacuum:

The teetering rotor in a vacuum has no tendency to align the rotor and mast perpendicular to each other, while the very common hinge offset rotor does. And in the atmosphere, the teetering rotor also wants to align the mast perpendicular tp itself via the torque of the flapping effect described here.

So a helicopter taking off in a hover with the rotor horizontal, aligns both the fuselage and the rotor until the CoG is underneath the lift vector. If the CoG was not exactly underneath the hub centre, the fuselage rotation tilts the lift vector and the helicopter starts to drift, which needs to be compensated by cyclic stick input from the pilot. From FAA Rotorcraft Flying Handbook, Chapter 7 Weight and Balance:

  CG FORWARD OF FORWARD LIMIT. You can recognize this condition when coming to a hover following a vertical take-off. The helicopter will have a nose-low attitude, and you will need excessive rearward displacement of the cyclic control to maintain a hover in a no-wind condition.

Note that the above means that the rotor wants to align to the forward lean of the fuselage, which tendency must be compensated for by rearward cyclic.
In order to fly forward the pilot moves cyclic longitudinal forward, effectively tilting the rotor disk forward. As seen above, this also tilts the fuselage forward, moving the CoG to a new position further aft - this creates a nose-up moment, compensating for the nose-down moment of the thrust/drag torque.

When the helicopter picks up forward speed, air pushes at the fuselage: there is parasitic drag. This wants to tilt both the fuselage and the rotor further forward.

At increased airspeed, the rotor flapping provides an increased nose-up torque: the forward moving blade experiences higher lift at higher speed, and reaches a higher tip position when pointing forward. As explained in 2. above, this results in a fuselage nose-up moment as well due to the hinge coupling between rotor disk and fuselage.
The helicopter trim angle at speed can be further influenced by incorporating a horizontal tail, which applies a nose-up torque at speed. The horizontal tail incidence is often variable, in order to provide a wide range of stabilising moments at cruise speed, high angle descent etc.

The horizontal tail in cruise usually has a negative angle of attack, and is designed to make optimal use of the rotor downwash upon it. Horizontal tails are not required but highly desirable, for positive cyclic speed stability.
But a horizontal tail is ineffective in the hover, and a rotor on top has negative speed stability, as explained in this answer - the main reason for the instability in the hover of conventional helicopters, requiring constant stick inputs to maintain position.

Summarising, the nose-down pitching moment at forward speed is compensated by:

The flapping angle of the rotor disk.
The hinge moment coupling, either from hinge offset or from aerodynamic coupling in case of a teetering rotor. This effect wants to keep the rotor mast aligned perpendicular to the rotor.
The horizontal tail.
The useable horizontal range of CoG location.
And not mentioned above: in some cases canting of the tail rotor.


Why do private jets such as Gulfstream fly higher than other civilian jets? I heard in a TV show that private jets such as Gulfstream can fly at about 50,000 ft, higher than other civil jets.

Is it an aerodynamic reason (lighter aircraft to be sustained in a less dense air) or does it depend on the fact that a smaller fuselage is more resistant to lower outside pressure at a higher altitude?

I think that – if possible – flying higher, in order to fly faster and with lower fuel flow, is always better. Am I correct?

There are several reasons and none of them really have to do with a private jet being more aerodynamic than a commercial jet.

Private jets have better power to weight ratio than commercial jets so it is easier to ascend to greater heights. Commercial jets also carry more fuel which needs to be burned off to lighten the plane to go higher.

It’s easier to pressurize smaller cabins than larger ones (this is a significant factor for commercial jets).

Flying higher is usually better for avoiding weather that can even affect commercial airliners in the 30ks.

There is much less traffic up above 40k and it allows the private jets to fly more direct routes at a faster speed and more safely as well.


Substitute Suitable RNAV system for Inop Radar on approach “requiring” Radar Assuming my aircraft's navigation equipment is a "Qualified/Suitable RNAV System," as defined by AC 90-108, is it legal for me to fly the LDA Y Rwy 19 IAP to DCA  with ATC Radar out of service?

Here is a copy of FAA AC 90-108

Paragraph 7. a. (AC 90-108) states: (emphasis is mine)

  Uses of Suitable RNAV Systems.

  a.  Usage of Suitable RNAV Systems.
   Subject to the operating requirements in this AC,
  operators may use a suitable RNAV system in the following ways.

  (1)  Determine aircraft position relative to or distance from  a VOR (see first note in subparagraph 7b), TACAN, NDB, compass locator (see
     second note in subparagraph 7b), DME  fix; or a named fix defined by
     a VOR radial, TACAN course, NDB bearing, or compass locator  bearing
     intersecting a VOR or Localizer (LOC) course.

  (2)  Navigate to or from  a VOR, TACAN, NDB , or compass locator.

  (3)  Hold  over a VOR, TACAN, NDB, compass locator, or DME fix.

  (4)  Fly  an arc based upon DME.

Here is the approach plate in question:

Since "radar" means "ATC radar", I'm not sure how a pilot could substitute anything for it. The issue isn't that the pilot needs radar to navigate the approach; it's that's ATC needs radar in order to allow the approach in the first place.

Per this answer, ATC can only clear aircraft for an RNAV approach without an IAF if radar monitoring is available. I don't think we've found out why that's the case, but it's what the ATC orders say (4-8-1(h)). Since the approach above has no IAF, that means ATC can only clear you for it if they have radar monitoring.

4-8-1(g) also instructs controllers not to let pilots choose their approach if there's no radar available:

  g. Where instrument approaches require radar monitoring and radar
  services are not available, do not use the phraseology “cleared
  approach,” which allows the pilot his/her choice of instrument
  approaches.

In other words, ATC has to make sure that they clear pilots for approaches only if their own requirements are met.

But as it happens, ATC does have a possible substitution for radar. The ATC orders 5-5-4 say:

  The use of ADS-B only information may be used to support all radar
  requirements associated with any published instrument procedure that
  is annotated “Radar Required”.

I assume that means that - at least theoretically - if ATC lost radar but could still receive ADS-B, they could clear you for the approach. But that would be ATC substituting equipment, not the pilot :-)


What design feature prevents the fuselage skin from completely tearing off? For an example, I am talking about the Southwest Airlines Flight 812 where there was a small tear in the fuselage section caused as a result of metal fatigue.

Why didn't the tear affect other sections of the fuselage?
Is there any specific design feature involved to prevent such a situation or is it just plain luck that it did not happen?

In the 1980's, manufacturers thought that they had solved the problems that plagued earlier models like the De Havilland Comet. Then Aloha Airlines Flight 243 had a large section of upper fuselage come off during flight. Manufacturers realized that the fuselage could accumulate more damage more quickly than expected, and when this damage went undetected, it resulted in catastrophic failure.

The result was both regulators and manufacturers emphasizing a focus on both damage tolerance and fail safety when designing these structures.

Damage tolerance means that the structure can tolerate a certain amount of damage while still performing its function. Inspections should be performed soon enough that they will detect the damage before it compromises the structure.

Fail safety means that even if a feature fails, the overall structure can still perform its function. One option for this is redundancy. In the fuselage, this means stopping cracks from propagating too far. The cracks in the Aloha Airlines incident were able to continue growing until a large portion of structure failed.

These ideas mean that the structure is designed so that any damage is caught before it becomes critical, but in the event that this is not sufficient, items can fail without endangering the safety of flight.

An example is what happened to Southwest Flight 812. A section of fuselage ripped open in flight, which resulted in a rapid depressurization but a safe landing. A crack formed in the fuselage and was not detected. However, the crack was contained in a limited section of the skin. This allowed the cracked skin to fail while the rest remained intact.


Have there been fully pneumatic aircraft? Have there been any passenger aircraft that used pneumatics for all of their on board systems that required force actuation, such as:

landing gear;
wheel brakes;
nose wheel steering;
propeller brakes;
passenger door operation?

Yes there have been, and some of them are still flying.

This article is about the fully pneumatic actuation systems on board the F27s built by Fokker and by Fairchild. If there was a leak, it was leaking clean air. System pressure was 3,300 PSI = 228 bar.
Some of the advantages cited:

Many factors favored the use of pneumatic systems on the F-27, most significant of which was an approximate 100-lb weight saving over electrical and hydraulic systems.

Lighter weight
Faster operation
No flammable liquids
Cleaner and easier to maintain

The systems were designed 50 years ago, fully aeronautical lightweight design. Could most definitely be used to pump up the tyres in this question to 16 bar.


Could an amateur build a full-scale UAV? FAA section 333 provides permission to fly in the NAS with an airworthiness certificate. Obviously, the design would need to be perfect with extremely redundant control schemes. Going through the red tape, could an amateur build a UAV the size of, say, an RV-8 and legally fly it like a normal airplane?

You sure can,

The FAA provides a special airworthy cert for this kind of thing. There are a few types that you can apply for depending on what you are trying to fly. You can find the relevant info here

You can find the full Special Order that covers it here.

  Airworthiness Certification of Unmanned Aircraft Systems and Optionally
  Piloted Aircraft

  Purpose of This Order. This order establishes procedures for issuing special airworthiness certificates in the experimental
  category or special flight permits to unmanned aircraft systems (UAS)
  and manned aircraft integrated with UAS technology. For the purposes
  of this directive, manned aircraft integrated with UAS technology are
  referred to as optionally piloted aircraft (OPA).

In your specific example if it was an RV-8 (built as it usually is) with the ability to remote pilot it added in, it would be classified as an "optionally piloted aircraft"


How high could Concorde potentially reach by going fast and pulling up? If Concorde was travelling at mach 2 and FL 600 then pulled up, it would enter a trajectory that went above its normal flight altitude before diving back down. I assume that it couldn't pull up to full control surface deflection in those conditions without the wings folding, so without damaging anything, how how high could Concorde go using this method? Is there a way to calculate/estimate this, or is it only provable by testing? I've searched google for answers but I can't find anything on this subject.
(An unrelated question that I couldn't find an answer to: what was the structural G limit of Concorde at cruising speed)

There are a couple of ways to look at this question. The easiest is in first principals.
Therefore imagine that the concord (flying at Mach 2 at FL 600) can suddenly and without energy loss pull up, such that it flies for example 10 degrees upwards. Also we assume the following:

The engine flames out immediately, therefore no engine thrust.
We neglect air resistance

How much higher would it go? The formula to calculate this is suprisingly simple:
$$ \Delta x = 1/2 \cdot \frac{(V_I \cdot sin(\gamma))^2}{g} $$
with $V_I$ being the inital velocity (590 m/s which is Mach 2), $\gamma$ being the climb angle and $g$ being the gravity of $9.81 \frac{m}{s^2}$.
I have calculated it for a couple of angles:

$\gamma = 10°$: 535m
$\gamma = 30°$: 4436m
$\gamma = 45°$: 8871m
$\gamma = 60°$: 13307m
$\gamma = 90°$: 17742m

That gives us a first guess, but the question remains: Could it pull up at this high altitude? The answer is: Yes. Consider the formula to compute the dynamic pressure:
$$ q = 1/2 \cdot \rho \cdot V^2 $$
The concorde takes-off at around $113 \frac{m}{s}$ at an air density of around $1.225 \frac{kg}{m^3}$. The air density at FL 600 is around 1/10th of the air density at sea level. However the crusing speed is roughly 5.2 times faster, which yields 2.7 times higher dynamic pressure at that altitude. Thus, the rudders definitly work at that altitude.
The real limiting factor here are the structural limits when you try to pull up at Mach 2. For example if you try to pull up your aircraft at Mach 2 with a constant acceleration of 1 G, you will follow an circle with a radius of ~50km. Even with 3 G acceleration, you will still follow an (upward) circle with a radius of roughly 16km. My guess is that the Concord can safely handle around 3 Gs (For example to be able to handle gusts at altitude). Additionally, you will loose a lot of your energy while pulling up, due to additional drag (remember, because of the increase angle of attack, the aircraft has more drag) and of course you are getting slower as you trade velocity versus height. Thus as some point you will not be able to pull-up any further because you lost too much speed. I tried to estimate how much higher you would have to fly in order to go down to stall speed1, and my result is 11.2 km of additional height. That would mean that you could reach a $~70°$ climb. However I neglected air-drag etc. and the fact that you will definitly not pull 3Gs at stall speed.
To get a definit answer, one would have to perform some computer simulations. Perhaps one of the popular flight simulations can help. But I would guesstimate, that at FL 600 going at Mach 2, you can probably (safely) pull the airplane up into a climb of around $\gamma = 30°$, which would yield around ~4.4km of additional height.
P.S: However the assumption that the engine will flame out at higher altitudes is probably true. My guess would be that the engine was designed such that it can not substantially exceed FL 600. But that is speculation.
1 I simply assumed that the stall speed is at the same dynamic pressure as at take-off condition. This yields a stall speed of $357 \frac{m}{s}$


What is the GE90-115b turbine power output in horsepower? The GE90-115b is rated at 513 kN maximum thrust and is often said to have 110,000 shaft horsepower, but I have yet to find any document or specification that backs the claim on horsepower figure.
A comparable engine, the Trent XWB-97 rated at 430 kN and puts out 50,000 shp according to the Rolls-Royce website.
The vast difference in horsepower 50,000 shp vs 110000 shp and not all that huge difference in thrust 430 kN vs 513 kN makes me suspicious if the GE90 actually puts out 110,000 or if this has become a "thing" for the GE90 without being correct. Or, perhaps shaft horsepower and turbine horsepower is not the same?
Does the GE90-115b actually output 110,000 shp?

Based on the GE website, where they used a GE90-115B as a power generation unit, called the LM9000. GE cited 65,000 horsepower, which seems to scaled more reasonably when compared to the RB211 XWB
https://www.ge.com/news/reports/ge-oil-gas-just-turned-worlds-largest-jet-engine-65-megawatt-power-plant?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%253A%20gereports%252Ffeed%20%2528GE%20Reports%2529


Has there ever been an aircraft with three sets of flight controls? On every aircraft I know, there is either one set of flight controls if it is single-pilot operated, or two sets of flight controls allowing either the pilot or copilot full control.

Has there ever been an aircraft that has three or more sets of flight controls?

To clarify:

"aircraft" includes fixed-wing, helicopter, powered lift etc.
remotely operated aircraft do not count.
A set of flight controls consists of yokes, pedals and/or sticks that allow the operator to manipulate the pitch, roll and yaw axes.

Depends if you are asking about production or testbed stuff, NASA had at least one test bed aircraft that looks to have had at least 4 sets of controls (also covered in this question).

If you consider the space shuttle an aircraft, some of the thrusting capabilities (enough for pitch roll and yaw I belive) were operable from the arm control position.


How does aircraft weight affect the glide performance? Since the L/D ratio remains unaffected by the aircraft weight, will there be any effect to the gliding range?

The gliding slope, which equals $D/L$, does not change with weight. Hence, starting from a given height $h$, the longest gliding distance will be $d = h \cdot max(L/D) = h \cdot max(C_L/C_D)$, i.e., independent of weight.

However, the gliding speed, and, consequently, the gliding time, do change with weight, and significantly. If $C_{L,max}$ is the lift coefficient when $C_L/C_D$ is maximal, the gliding speed at best slope, $\bar{V}$, is obtained from $W = (1/2) \cdot rho \cdot \bar{V}^2 \cdot S_{ref} \cdot  C_{L,max}$.


Why does this B-52 carry a payload only on its right wing? Here is a picture of a B-52 located at the Pima air and space museum.

Source:(www.airplaneexhibits.com)

As you can see in the picture on the right wing next to one of the engines there is some kind of missile carrier, but the left wing has no missile carrier. Wouldn't the weight of the aircraft be very unbalanced with a missile on the right side, but no missile on the left side. I have noticed this in a lot of pictures of B-52's where they are carrying a missile on the right wing, but no missile on the left one.

@Peter is right.

The aircraft in question is the "The High and Mighty One" a NB-52A serial number 52-0003, which was used as a launch aircraft for the North American X-15, a hypersonic rocket powered aircraft. The 'missile carrier' (pylon) is used for carrying the X-15.

Here is a view of the carrier itself, just after launching.

"X-15 launched bw". Licensed under Public Domain via Commons.

This was used as the X-15 was not designed to takeoff under its own power; it was rather designed to be carried aloft and drop launched from under the wing of a NASA B-52 'mother ship'. As of March 2016, the X-15 holds the official world record for the highest speed ever reached by a manned, powered aircraft.

Image from air-and-space.com; Photo courtesy North American Rockwell.

The aircraft underwent significant modifications for installation of the pylon, including removal of the wing (no. 3) fuel tank, disabling the inboard flaps in the starboard wing and cutting a notch to accommodate the X-15's vertical stabilizer.

The heaviest weight the aircraft carried on the pylon was ~53,100 lb, for X-15 with external fuel tanks. A number of tests were carried out and it was found that the carrier aircraft were capable of trimming out the unbalance of the B-52/X-15 combination. So this caused few problems in flight in the operational range.


Any script to plot multi axis FDR / flight-test data (such as the ones used in air crash investigation)? I am looking for a script or tool to create flight test and/or FDR plots with several vertical axis, such as the ones used in aircraft accident investigations.

Does anyone have any hint on a MATLAB or Python script that does it? I have the data and I know how to code, just didn't want to reinvent the wheel here.

Example:

Source

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


Why does a hydraulic system failure increase the landing distance? Considering wide body aircraft, why do emergencies, related to hydraulic system failure, increase the landing distance?

Any hydraulic failure will affect the landing distance as most of aircraft controls are operated by hydraulics.

If the high lift devices (flaps) become inoperative (or become degraded) due to hydraulic failure, the aircraft will have a higher approach speed, which will increase the landing distance.
Hydraulics are also used for operating a number of other systems like brakes, ground spoilers and thrust reversers. Any degradation in their operation will increase landing distance.


How does the FAA compute the values in TPP's Climb/Descent Table? The inside back cover of the FAA Terminal Procedures Publication contains a table headed “CLIMB/DESCENT TABLE,” excerpted below.

Source: FAA, p. 19

How do required ascent or descent per nautical mile and ground speed combine to give feet per minute? What is the relationship between the values in the two leftmost columns?

Given a required climb or descent in feet per minute and ground speed in knots, compute the target VSI reading with required climb/descent multiplied by ground speed divided by sixty, or

$$\delta_{VSI} = \frac{\mathrm{RCD} \times \mathrm{GS}}{60}$$

Apply dimensional analysis to see why this works. Informally, we can think of nautical miles and hours in the numerator and denominator as canceling each other out to leave a figure in feet per minute.

$$
\delta_{VSI}\ \frac{\mathrm{ft}}{\mathrm{min}}
=
\mathrm{RCD}\ \frac{\mathrm{ft}}{\mathrm{nm}}
\times
\mathrm{GS}\ \frac{\mathrm{nm}}{\mathrm{hour}}
\times
\frac{\mathrm{1\ hour}}{\mathrm{60\ min}}
$$

Fundamentally, trigonometry determines the values given angles in the leftmost column and the FAA’s definition of a nautical mile being 6,076.1 feet. In a right triangle, tangent is the ratio of the opposite leg to the adjacent leg for a given angle $\theta$, illustrated below for a climb.

For the values in the table

the adjacent leg is exactly 1 nautical mile
the angle $\theta$ is the precise value from the leftmost column
the opposite leg is unknown and is the desired ft/NM value

The core formula is $6,076.1 \tan\theta$ for the ft/NM values, and this is the derivation of the values in the Vertical Path Angle box outlined with a heavy border. Outside this box, the climb rates are rounded to the nearest multiple of 5. The rest of the table values use the $\delta_{VSI}$ formula above.

For reference, see a Google spreadsheet that computes climb/descent rates using the above. The formula for altitude change for a climb or descent at 2.0° over 1 NM is of the form

=mround($O$1*tan(radians(B4)),5)

The value in O1 is the number of feet in one nautical mile. The trigonometric functions in Excel and Google Sheets deal in radians rather than degrees, where a complete circle has $2\pi$ radians.

The formula for the $\delta_{VSI}$ values in feet-per-minute is either

=mround(D$3*$C4/60,5)

or

=D$3*$C6/60

depending on whether the cell is inside the Vertical Path Angle box, i.e., whether the value should be rounded to the nearest multiple of 5 or not.

There are discrepancies, no more than 15 feet per minute. Some of the FAA figures are more conservative, some less. I was not able to discern a pattern; for details, see the color coding in the Computed sheet or the Deltas sheet in the linked workbook. The odd duck is for a 2.0° climb at 210-knot ground speed: the FAA table gives an unrounded value of 743 feet per minute rather than rounding as with its neighbors.

Stack Exchange does not support tables in their Markdown flavor, so a screenshot of the computed table is below.


Is there a global map of aviation waypoints? Is there such a map or database available to the public?

I think what you are searching for is SkyVector

Its a web-map where you can see waypoints, NDBS, DMES, FREQUENCIES, ETC


How do wing ribs withstand lateral lift force? During roll,there is a vertical component of lift that keeps the plane in the air and an horizontal component that actually rolls the plane,how are wing ribs designed to help withstand this vertical(now sideways to ribs) lift force since wing ribs are inherently weak laterally?

TL;DR: from the ribs perspective nothing changes.

Look at the three figures you posted: the lift is always straight in the middle of the aircraft. Tilt the aircraft, the lift tilts with the aircraft.

From the perspective of the ribs there is no side force, the lift is still perpendicular to the wings (actually, to the incoming airflow, but is a good approximation).

The only case where the wings will see some side force is when the aircraft is in a sideslip, i.e. $\beta \neq 0$.

In such a situation is not the ribs that carry the side load, but the wing beams, that run along the whole wing.


Why are some non-towered airports charted with an empty circle? Guntly Memorial Airport (62C) is shown as an empty circle with four hash marks around the edges. Why is it empty versus some of the other airports around (such as 96C, C89, BUU, etc.) that have a depiction of the runways inside a magenta circle?

Also, do the hash marks around an empty circle mean the usual - that there are fuel services available at that airport?

Your first stop for questions like this should be the FAA Aeronautical Chart User's Guide. In the VFR Sectional & TAC section it says:

  Runway patterns will be depicted at airports with at least one hard surfaced runway 1500´ or greater in length.

If you look up the details for 62C in the Chart Supplement or whatever other source you like, you can see it has two grass runways, i.e. no hard surfaced runways.

As for the hash marks, they do mean that fuel is available.


How do manufacturers engineer their aircraft to deal with tail strikes? I have been told that tail strikes on take off and landing are rare but do occur.  I think, in my mind, the tail touching the ground at all would just make the tail fall off, but it appears I was wrong.  In most of cases of tail strikes I've read about the plane is able to either continue on it's journey or can simply circle back to the field it departed from.

So I'm wondering, what do big commercial aircraft manufacturers (like Boeing and Airbus) do to keep tail strikes from turning into a major disaster?  How do they engineer the plane to survive the incident?

During testing, the rear fuselage is protected by a beam made of oak or even steel to distribute the tail strike loads and to protect the aircraft skin.

A340 during tail strike tests. This one is literally blazing along the runway …

For normal operations, the protection is removed. However, tail strikes must not cause flight-critical damage, so a few precautions are taken during design:

No hydraulic or electrical lines must run along the bottom of the rear fuselage.
If there are still mechanical control elements like pushrods, they and their collapsing supports must not be close to the bottom of the fuselage.
The tail strike location must be outside of the pressurized part of the fuselage.

The main protection against tail strikes, however, is procedural: The rotation speed must be high enough to allow lift-off before a critical pitch attitude is reached.

Delta wing aircraft are much easier to over-rotate, so the Concorde used a retractable tailwheel for tail strike protection:


Is it possible to fly VFR above the IMC floor or VFR-On-Top without a specifically filed route, both using an IFR flight plan to go through IMC? *Note, I'm not trying to recommend this, but I am curious if it can be done.

In this question, Steve V.'s answer made me wonder about this:

One time during my commercial training, my instructor and I received an "area clearance" over downtown Nashville for simulated aerial photography, which allowed us to circle over downtown with visual reference within class C airspace as we wished with no defined route.

In the above case, we were not on an IFR flight plan, nor were we above the IMC floor.

Scenario 1:

Is it possible to get an IFR clearance for an area as VFR-On-Top, without having to file a routed flight plan with fixes, effectively allowing an instructor and a student to practice with their own spontaneous navigation choices in VMC at an altitude above IMC conditions?

Scenario 2:

Same as above, but foregoing the VFR-on-top and accomplishing it purely as IFR.

Scenario 3:

File two IFR flight plans, cancel the first one once above clouds in VMC, do your thing, and then receive the next IFR flight plan clearance to shoot the approach back down.

Are any of those options?

This question probably covers some of your points but here's some more information. See the AIM 5-5-13 and ATC Orders 7-3-1 for more details.

Can I get an IFR clearance for an area and operate there VFR-on-top?

Yes. VFR-on-top by itself is only a clearance to use VFR altitudes, it isn't a clearance to deviate from your course. But ATC can clear any IFR flight to operate within an arbitrary, defined area (ATC Orders 4-4-1):

  EXAMPLE−
  1. “Cleared to fly east of Allentown VORTAC between the zero four five and the one three five radials within four zero mile radius.”
  2. “Cleared to fly east of Crystal Lake radio beacon between the two two five and the three one five courses to Crystal Lake within three
  zero mile radius.”
  3. “Cleared to fly northeast quadrant of Philipsburg VORTAC within four zero mile radius.”

Same as above, but foregoing the VFR-on-top and accomplishing it purely as IFR.

I don't know exactly what you mean here: VFR-on-top is an IFR clearance. If you're asking how to change altitude as needed under IFR without using VFR-on-top, you can request a block altitude clearance.

Can I file two flight plans?

What would the departure point be for your second flight plan? I suppose it might happen if you departed IFR, requested climb to VFR-on-top, cancelled IFR in VMC, then called back for a pop-up IFR clearance to shoot an approach. But I don't see the point: why not just work with ATC in the first place and stay in contact with them for the whole flight?

All in all, the simplest thing here is just to ask ATC for what you need. Except in very busy terminal areas, they're very good at accommodating pilot requests, whether VFR or IFR.


Why are videos call and voice calls prohibited on airplanes? I'm taking a flight to Japan this summer and noticed that on United, they may have wifi but it says everywhere that no voice calls or video calls are permitted and strictly prohibited during flight. They don't say why, but out of curiosity why is that such a big deal?

Voice/video calls have not been approved by the FAA, and no one is particularly interested in having them approved, due to the frustration it would cause amongst passengers, having to listen to a multitude of conversations in a confined space, throughout the flight. Not to mention the fact that it would clog the limited bandwidth if even a sizable chunk of the passengers wanted to do it.

Virgin comes right out and says it with something along the lines of "For the safety and comfort of our guests, VoIP and Video Chat is also prohibited".


Is white/brown-out effect hazardous during the landing roll out? Landing on unpaved runways or runways covered by snow or dust causes a white/brown-out visibility restriction.

Does it disrupt the pilot's visibility during the roll out in a fixed-wing aircraft?

From a partial accident list on Wikipedia, the issue seems to affect only helicopters.

A fixed wing rolling out should have no issue. As the dust/snow cloud will be behind the windshield. A plane landing in sequence should wait until the dust/snow settles.

Also an approach in poor visibility caused by a sandstorm would be no different than an approach in fog. An instrument approach will be carried out.