How do airports with no ATC operate? I've heard that some airports don't have an ATC tower and nobody monitors the landings. Can someone tell me how those planes can land/takeoff safely without incidents occurring? I understand the fact that the airports without an ATC tower are small airports but wouldn't there be factors like weather which can cause accidents? So can someone please tell me how those planes can operate safely without ATC?

I will answer this for the regulations and general procedures in the USA as laid out by the FAA, operations may vary elsewhere in the world. AOPA publishes a nice guide on how traffic flow at un-towered/un-controlled fields works and I would advise giving it a read as it covers a wide variety of scenarios. Effectively planes self announce and monitor radio traffic as they approach and depart the airfield.

Basic right of way is established in FAA FAR 91.113 and provide guidelines for operations. While some more specifics can be found in FAA FAR 91.126 and FAA FAR 91.127 relating to un-towered/un-controlled operations specifically.

Ill provide a brief example of a departure and approach (as would be heard on the radio over the Common Traffic Advisory frequency "CTAF"). You as the pilot in command are always responsible to "See and Avoid" so you should always have your heads up on approach to a field looking for traffic.

  Plane is started and taxied to the run up area, checked, and lined up at the hold short line with out making any calls. You simply look around while taxing as you would when driving a car. The only exception to this is taxing on the actual runway which requires a "Piper Archer Back Taxing 05" call.
  (check downwind, base, and final for incoming aircraft as you monitor the radio for calls)
  (when you see its all clear) "Piper Archer taking 05 for a Northbound departure"
  Enter the runway, make sure its clear, takeoff
  Follow any procedures that the airport may have (noise abatement etc.)
  "Piper Archer departing the pattern to the north"

Then for a basic arrival you should fly the standard traffic pattern as outlined in the AF/D for the given field.

  Tune radio to CTAF and listen in if no one else is making announcements you can begin yours. For the most part everyone will make the following announcements or a similar variant there of.

  "Piper archer 5 miles to the north, inbound for a landing on 05"

  "Piper archer entering left downwind for 05" (General procedure calls for entering the traffic pattern on the downwind leg)

  "Piper Archer turning base for 05"

  "Piper archer turning final for 05"

  Land

  "Piper archer clear runway 05"

Some points to note. If you hear calls of others in the pattern you can still enter. Generally you want to be 1 or 2 legs behind the plane in front of you. This varies depending on what you are flying and what they are flying. For example I was landing one day in my Archer and a Seneca was inbound behind me but close, him being the heavier and far faster aircraft I let him in. Over the radio I allowed him to overtake me (I extended my downwind for him) since he was the faster plane I did not mind having some extra time to set up my approach.

On short final you should always be checking to make sure that no one pulls out onto the runway or that no one is departing. At an un-towered field dont be afraid to go around!

As Ron mentions in the comments below, there is, strictly speaking, no regulation requiring you to have a radio on board for VFR flight. That being said some older planes that lack full electrical systems also subsequently lack radios. Many have hand held units on board but again are not required to. In this case they must observe the traffic flow and enter the pattern in a safe manner, this is why you should always have your heads up looking out for aircraft doing this.

  wouldn't there be factors like weather which can cause accidents?

At both big and small airports weather is handled similarly. If the conditions are VFR then a visual approach is conducted and you can avoid other aircraft by simply seeing them. The scenario above is a standard VFR arrival and approach. If the weather calls for an IFR approach and and you are in an IFR equipped aircraft and furthermore the field has an IFR approach into it (be it RNAV or GPS etc.) you may conduct an IFR approach into the field. In this case you will make calls at the proper call out points on the approach (similar to a VFR call out). Since you cant physically see the other traffic in this case radio monitoring is key.


Did people really hand-start big bombers in WWII? I am not a pilot so I don't know anything about hand starting propeller aircraft. But I wonder how easily can the propeller fire up unexpectedly during the procedure even if it's done right. Whenever I see an old WWII movie and the guys are turning those big props on the bombers, I always think of that question.

When you shut down a radial the unscavenged oil in the case (oil coating the surfaces that didn't get pumped back to the reservoir tank) runs down and seeps past the rings of the cylinders directly below and to each side at the bottom.  In theory, it can create an hydraulic lock if there is enough oil collected in a cylinder, that happens to be on its compression stroke (both valves closed), and the oil volume is more than the cylinder volume at top dead centre.  Although an actual hydraulic lock is fairly rare (it takes quite a lot of oil), you still have to check for it because if a jug fires on start while one of the bottom cylinders is locked, it'll bend that jug's connecting rod and/or crack the head.

The engine has to be turned with no ignition/fuel to test for this.  Typically it's done by hand as shown in those films.  If you feel a hydraulic lock coming on as you pull through, you turn the engine the other way to back it off and can remove the lower plugs to let the oil drain out.

An aircraft could have propellers that are out of reach of the ground, or there may be some other reason, so you also have the option of doing it with the starter with fuel and ignition turned off.  If there is an hydraulic lock in a cylinder the starter won't be able to do any damage on its own (it'll either bog down or its clutch will slip), so it's safe to do, if done properly.

There is always some oil collected and when the engine is cranked it goes out the exhaust valve when it opens and coats the inside of the exhaust ducting.  The coating of oil takes quite a while to burn off the inside of the exhaust manifold, which is why they belch smoke for 30 seconds to minute after they start.

It IS possible to "hand start" a big radial in a fix, using things like tires slipped over the prop and pulled by a car with a rope, but not by hand unless it's a smaller radial, say under 1000 cubic inches.


What is the lightest weight operational jet/turboprop fighter ever deployed in combat? Since the beginning of WWII there was been a trend towards larger fighter aircraft. In about 1960 the United States continued with larger fighters (F4, F100, F111, F15) but also started a branch of very small light weight fighters (F105, F16, Tucano, etc).

What is the lightest weight jet/turboprop fighter any nation has ever deployed in actual combat?

Epilogue: I learned more from this discussion than I expected. As I recall, at least one South American country used the BD5J but it never saw combat. That's why I included the combat stipulation. - Thanks for the answers...

The A-37 Dragonfly is the smallest production combat aircraft I'm aware of.

Empty weight of  6,211 lb (2,817 kg). Max takeoff weight of 14,000 lb (6,350 kg).


How can adverse maneuverability due to a fuel tank behind the rear pressure bulkhead be mitigated in Airbus ZeroE hydrogen plane? Airbus recently announced three concept aircraft for commercial use, powered by liquid hydrogen, with an ambition to have the plane in operation by 2035.
https://www.airbus.com/innovation/zero-emission/hydrogen/zeroe.html
https://www.airbus.com/newsroom/stories/these-new-Airbus-concept-aircraft-have-one-thing-in-common.html
From what I can tell, the turbofan variant is in the same segment as the current A320, albeit with somewhat reduced range.
Considering hydrogen powered planes, the challenge is to carry enough fuel to make it compete with kerosene.
There are several options, and from this question it seems 3 options stand out:

Cryogenic: storing the fuel as a liquid
Compressed: requiring heavy and strong fuel tanks
Hydrides: bind hydrogen with another substance and release upon heating

Airbus intends to go with option number 1, that is storing the fuel liquid and cryogenically behind the rear pressure bulkhead.
The unbalanced weight distribution storing not only the fuel, but assuming also heavy tanks and cooling equipment in the far rear of the plane seems like a maneuverability issue to me, with a pitch-up moment from the shifted weight balance.
What measures can be taken to mitigate the (assumed) adverse handling this creates?

Airbus will store hydrogen by chemically binding it to carbon for a looong time. This way, it can be put into the wings, a belly tank and the horizontal tail and its gradual disappearance during the flight will not shift the center of gravity much.
What the PR department just published is just for political correctness. It has not been thoroughly checked for practicability by the engineering department. Nobody seriously expects to use hydrogen for airliners. The problems of storage are obviously putting it at a huge disadvantage, and your correctly identified issue of storing fuel far from the center of gravity is one of those problems.
When an Airbus is delivered today, its tanks are filled with a blend  containing hydrocarbons from a carbon neutral source. Beluga flights delivering parts between the Airbus plants use this fuel. Virgin Airlines tested a renewable fuel already in 2008 and Lufthansa flights departing from Frankfurt also use it.
Of course, most airlines will refill with regular, mineral oil based kerosene after this fuel has been used up because it is cheaper and availability is much better. But technically there is nothing holding back airlines today to use a carbon-neutral fuel.
Generating hydrogen today is mostly done using natural gas which is not quite as carbon intensive as kerosene but everything but carbon-neutral. Also, the energy source for refining and transporting fuel from renewable sources will make them less than 100% carbon neutral. The current sources for renewable fuels (plant oils and waste materials) are less than optimal and hard to scale up, but work on using direct sequestration from atmospheric carbon dioxide is progressing. Today, we waste excess solar power by shorting it to ground. I know better uses for that excess energy …


Which trigonometric algorithm does an FMS use to determine distance between waypoints? When entering waypoints into an FMS, the FMS calculates bearing and distance between them.

Does it use "normal" spherical trigonometry equations, or go for the more accurate Vincenty algorithm which takes the earth to be an oblate spheroid?

Short answer

Aeronautical data (fixes, waypoints, navaids, instrument procedures) are delivered to aircraft operators and avionics manufacturers referenced to the WGS-84 ellipsoid.

To make is simple the ellipsoid is the volume enclosed by the revolution of an ellipse which best approximates the shape of the Earth, generally in a given region only. WGS ellipsoid is a global one which approximates the whole Earth shape.

FAA provides rules for designing procedures, and algorithms to use to compute various elements, including the distance between two fixes and their relative azimuths. This is described in Order 8260.54 The United States Standard for Area Navigation (RNAV), Appendix 2. TERPS Standard Formulas for Geodetic Calculations:

  1.0 Purpose

  The ellipsoidal formulas contained in this document must be used in
  determining  RNAV flight path (GPS, RNP, WAAS, LAAS) fixes,
  courses, and distance between fixes. Notes: Algorithms and methods
  are described for calculating geodetic locations (latitudes and
  longitudes) on the World Geodetic System of 1984 (WGS-84)
  ellipsoid, resulting from intersections of geodesic and non-geodesic
  paths. These algorithms utilize existing  distance and azimuth
  calculation methods to compute intersections and tangent points
  needed for area navigation procedure construction. The methods apply
  corrections to  an initial spherical approximation until the error is
  less than the maximum allowable error, as specified by the user.

[...]

  3.4 Direct and Inverse Algorithms.

  The Direct and Inverse cases utilize formulae from T. Vincenty’s,
  Survey Review XXIII, No. 176, April 1975: Direct and Inverse Solutions
  of Geodesics on the Ellipsoid with Application of Nested Equations.

FMS use ellipsoid geometry to compute distances and angles, in order to match aeronautical data.

A visible consequence is that, except for meridians and equator, prlongating a geodesic on an ellipsoid doesn't draw a closed curve, as if it were a great circle:

Detailed answer: Need for WGS-84

New modes of navigation have emerged with a significantly better accuracy than using VOR-DME and inertial:

RNAV (area navigation) generally uses GNSS (global navigation satellite system, one GNSS being the US GPS),
RNP (required navigation performance),
and more generally performance-based navigation (PBN).

At the same time these new direct modes of navigation (compared to a navaid-to-navaid paths) can define paths extending to thousands of NM, and commonly crossing different geodetic reference systems where latitude, longitude, height and vertical can have significantly different values.

As an illustration, the measure of "height" used to be referenced to local MSL (mean sea level):

(source)

But a GPS receiver, which is now the main instrument to locate a point, can only provide the height above an ellipsoidal simplified Earth model. Latest receivers also provide the height above the simplified sea level model (geoid), but only as the result of a transformation of the ellipsoidal height, etc.

(source)

As visible above, the direction of the local vertical is impacted by the transformation, creating another problem for airborne vehicles navigation.

This can quickly become a nightmare with differences for the same point up to 100m depending on the reference used:

For these reasons, it appeared very early that all elements involved in mapping, navigation and ATC must use the same datum, in all countries. ICAO has selected WGS-84.

ICAO Doc9674:

  The Council [...] on 28 February 1994, adopted Amendment 28 to Annex 15,
  introducing the provisions concerning the promulgation of WGS-84-related
  geographical coordinates. [...]

WGS-84 on Wikipedia:

  The WGS 84 datum surface is an oblate spheroid (ellipsoid) with major
  (equatorial) radius a = 6378137 m at the equator and flattening f =
  1/298.257223563. The polar semi-minor axis b then equals a times
  (1−f), or 6356752.3142 m.

Current country compliance with ICAO selected datum: See Jeppesen WGS-84 Status Report.

Aeronautical databases

FMS uses aeronautical data (fixes, procedures) in the ARINC 424 format, where legs are WGS-84 paths.

Processing of aeronautical data

I've had difficulty to get the exact authoritative document making mandatory the use of ellipsoid geometry in a FMS, however, from FAA Order 8260.52 related to RNP, FMS are part of the so called GPN means which are referenced to WGS-84:

  Geographic Positioning Navigation (GPN).

  Navigation based on geodetic
  calculation of geographic position referenced to the WGS-84 ellipsoid.
  Global positioning system (GPS), wide area augentation system  (WAAS),
  local area augmentation system (LAAS), flight management system (FMS),
  RNP, and area navigation (RNAV) are examples of GPN.

When calculating distances between fixes, or angles, a FMS computes geodesics which are shortest paths between fixes. On a sphere this would be a great circle. On an ellipsoid this has to be adjusted, Vincenty's formulas are one of the methods that can be used for approximation.

Additional details on how geodesic calculations are done can be found in FAA Order 8260.58 related to Performance Based Navigation.


Are there regulations for unmanned aerial systems avionics? I know that there are documents such as DO-178B, DO-178C and DO-254 that provide guidance and requirements for the development of avionics in general.

In my opinion it's hard to believe that avionics developed for unmanned aerial systems (left) are subject to the same technical requirements than those on board manned aircraft (right).

Therefore I ask:

Are there any specific regulations for avionics on board unmanned aerial systems?
If so, how do they differ from those specified in documents such as DO-178B, DO-178C and DO-254?

The flight control software on military grade UAV/UAS has DO-178/DO-254 requirements, per briefings I attended, and also that software provided for embedding in those had to meet those and other requirements.

I am not an expert on the UAS platform we used (Global Hawk RQ-4) but it is safe to say that it is a complex bird with multiple capabilities. A typical mission flight crew consisted of a launch and recovery pilot, and mission pilots and sensor operators, in sufficient numbers to handle extended missions.

I am unaware of any consumer grade UAS utilizing those standards, and doubt there are many, if any at all, due to the increased development cost. I am unaware of any type certificated sUAS.

To give you an example, I had a certain nav sensor related function integrated for VFR use on a sensor platform (Twin Otter).  The development cost was about 4.5 million. If we were to apply the standards so that we could operate that platform in an IFR environment, the estimated cost was about 9.5 to 11 million.  Sure there were just a few additional capabilities, but a big part of it was systems engineering and test.


What is the method to calculate a finite wing's lift from its sectional airfoil shape? I am struggling to get my head around a concept that I believe should be fairly simple to understand.

Lift versus drag and AoA data of many airfoils are freely available, for instance the NACA 4-digit airfoils.

The data is that of sectional, or 2D, lift and drag, or $C_l$ and $C_d$.

Now, if I were to build a 3D finite wing using a certain airfoil, how would I go about calculating the 3D coefficient of lift $C_L$?

I know that the aspect ratio $AR$ and Oswald efficiency factor $e$ come into play and that $C_D<C_d$ because of 3D effects such as tip leakage.

As an example, let's look at the NACA2412 airfoil: At $\alpha=8$ and at $Re=5.7e6$, it experiences $C_l=1$.

If I now manufacture a wing of $AR=7$ which has a planform giving an efficiency $e=0.8$, how would I go about calculating $C_L$?

Are there any exact methods to calculate this or perhaps approximations?

There are indeed several approximations, depending on the shape of the wing. Generally, the lift curve slope is $2\pi$ only for a flat plate in inviscid 2D flow (with Kutta condition fulfilled). With thicker airfoils, the lift curve slope in 2D increases slightly. It also increases with Mach number proportional to the Prandtl-Glauert factor $\frac{1}{\sqrt{1-Ma^2}}$ and the Reynolds number.

Now to 3D flow: Once you move away from infinite aspect ratios, the lift curve slope drops. With very small aspect ratios $AR$ the lift curve slope becomes $c_{L\alpha} = \frac{\pi \cdot AR}{2}$. See the plot below for the ideal lift curve slope of an unswept wing:

Please note that the red line is only valid for AR = 0! Then the lift curve slope increases up to $c_{L\alpha} = 2\cdot\pi$  for $AR = \infty$ (and zero airfoil thickness and no friction effect), as shown by the blue line. If you know your airfoil lift curve slope, modify the result from the plot above by the ratio between the airfoil lift curve slope and $2\pi$. Now your lift coefficient will become:

$$c_L = c_{L\alpha_{3D}}\frac{c_{L\alpha_{2D}}}{2\pi}\cdot\alpha$$

with your angle of attack $\alpha$ in radians.

For an analytic approach you may use the formulas below, but stay away from the region close to Mach 1. If those (rather precise) approximations look too daunting, feel free to simplify them:

Nomenclature:
    $c_{L\alpha} \:\:$ lift coefficient gradient over angle of attack
    $c_{L\alpha\:ic} \:$ lift coefficient gradient over angle of attack in incompressible flow
    $\pi \:\:\:\:\:$  3.14159$\dots$
    $AR \:\:$  aspect ratio of the wing
    $\nu \:\:\:\:\:$  the wing's dihedral angle
    $\varphi_m \:\:$  sweep angle of wing at mid chord
    $\varphi_{LE} \:$  sweep angle of wing at leading edge
    $\lambda \:\:\:\:\:$  taper ratio (ratio of tip chord to root chord)
    $(\frac{x}{l})_{d\:max} \:$  chordwise position of maximum airfoil thickness
    $Ma \:\:$  Mach number

Note that you do not need the planform efficiency (Oswald factor) $\epsilon$ for calculating lift curve slope. That only comes into play when you compute the induced drag of the wing.


Can thrust vectoring be used to enable the use of flaps on tailless delta-winged aircraft? I'm considering flying wings as well as airplanes with only vertical stabilizer for their compact size, efficiency and high speed.

As I can't find a working example of such scheme, theoretical explanation is very welcome.
To compensate for rear end additional lift, thrust output will probably be placed at the nose.

Possible options by propulsion types:

Propeller

tilted prop rotor (fixed / variable pitch)
propwash forwarding - canard fins
collective pitch thrust vectoring (swashplate driven)

Jet

additional small engine at the front (electric ducted fan)
ducts from the main engine
fan driven by the front shaft of the engine (as in Harrier Jump Jet)
tractor placement (as in ekranoplan)

Problems

(summary from answers and comments, thanks for valuable input)

Stability.
Change of angle of attack either intentional or by air conditions changes wing lengthwise distribution of lift.
Is it manageable for human to safely maintain stability in such conditions and if not - for a computer?

Thrust availability.
Approaching landing the forward thrust is minimized, so there should be close to 90° downward thrust line deflection.

Thrust agility.
Combustion jets are sluggish. There should be a nozzle limiting the output.
Partial reverser?

Safety.
Engine out below unpowered stall-speed at landing sounds like a nose down crash.
Redundancy should help.

So, is it viable to add enough nose-up moment and stability by vectoring thrust to counter the nose-down moment produced by flap extension, thus allowing STOL capabilities with flaps at acceptable angle of attack?

No, for several reasons

What you want is to compensate for the additional lift from downward deflected flaps at the back of a flying wing with vectored thrust. As @Sean points out this will not bring a noticeable net benefit if the lengthwise location of both forces is similar.

But that is not all.

Besides the force equilibrium around the flying wing you also need to consider how it behaves when flight parameters change, say by gusts. Will it return to the old state? How will the dynamic behavior be?

More camber means that the zero lift angle of attack becomes more negative. A deflected flap adds camber near the trailing edge. If the wing now assumes a higher angle of attack due to a gust, the change in local lift over chord will make the wing pitch up more. The forward region of the airfoil will add more lift relative to the initial state than the rear region because the zero lift angle of attack has been shifted downwards, adding a pitch-up moment. The whole aircraft will become unstable from the added camber of the flap.

Flying wings don't need computer control. All the Hortens and Fauvels of this world flew just fine with a human pilot and mechanical controls. That is because they use reflex airfoils and wing twist so the rear part of the wing creates less lift relative to its area. This is the condition for static stability and it gets removed with a positive flap deflection.

Adding that flap will add so much instability that computer control would have a hard time to keep the aircraft stable. If the flap produces substantial additional lift, the thrust vector control would need to effect large changes in pitching moment. Now consider you fly into an airport along the glide slope, with the engine close to idle. Where would the required pitching moment come from? Thrust is insufficient and reducing your flap setting will stall the aircraft. The best solution is to not deflect the flap in the first place and to add more wing area relative to a conventional aircraft.


What is this yellow tube blowing air? What is this yellow tube (lower right quadrant of the picture) which is blowing air into the airplane while it's at the terminal? You can see the open hatch on the bottom of the jet through which it's connected.

Most likely it’s a compressed air line which connects into the jet’s bleed air system.  This can be used to crank the engines as opposed to using bleed APU air to do it.

Another use (if you’re talking about the line under the jetway) is to provide cool air for cabin air conditioning without needing to run the APU to do so.


What kind of flight counts toward the commercial 100 nautical mile cross-country flight requirement? A question regarding the dual 100nm day/night 2 hours.

Does a 130nm flight with 1 stop halfway (over 2 hrs) count?
1 leg of 80nm, 2 leg 50nm.
Total time 2.5hrs.

Your question didn't give enough information for a 100% correct answer, so I'm going to make a few assumptions:

You are asking about FAA certification in the USA
You are asking about part 61 training, not part 141, 142, or anything else
You're asking about a single-engine commercial rating (this one is less important than the other two)

With those assumptions in mind, the controlling regulation is 61.169(A)(3)(iii-iv), which says (emphasis added):

(iii) One 2-hour cross country flight in a single engine airplane in daytime conditions that consists of a total straight-line distance of more than 100 nautical miles from the original point of departure;

(iv) One 2-hour cross country flight in a single engine airplane in nighttime conditions that consists of a total straight-line distance of more than 100 nautical miles from the original point of departure;

So you need to ask yourself:

Did you fly at least 2 hours?
Did you land at an airport at least 100 miles away from the original point of departure?
Did you do the entire flight during the day/night?

If so then you're good.  If not then no.


Special Purpose Tablet for Commercial Navigation app I just posted a request for advice on how to find right android tablet to integrate commercial flight navigation app (e.g., iFLY) to avoid bloat, OS updates that may not be compatible, and add future WiFi integration with commercial ADS B-In data overlays (e.g., FlightBox, etc.) on the Geo-referenced moving map in the navigation app.

(Please help, I don't know how to send this request to Don Hulme.)

I wish this site would embrace this topic because it is simply an extension of aircraft avionics and navigation.

This question will probably be closed, but I think this is an important question that doesn't have any definitive answer on the internet. I recently went through the upgrade from paper charts to electronic flight bag. There is very little guidance (information overload) or standardization on this topic. However, it is helpful to look at what some of the large aviation operators use.

Several flight schools have specific recommendations for tablets. For example,

ATP Flight School recommends the iPad mini, 32 GB, and Wi-Fi + Cellular for it's flight instructors.

Directly from ATP:

  ATP recommends the iPad mini, 32 GB, and Wi-Fi + Cellular (Available
  from Apple).

I've seen similar recommendations from other flight schools and Universities with flight programs but at the moment can't find the references (will update once I locate).

Personally, I use an iPad pro because I was informed that it has better anti-glare properties on its glass than the non-pro version of the ipad, which is important for day operations in the cockpit.

(Note, Apple lists antireflective coating on both the Pro and the Mini version of iPad but not the regular iPad).

I have run several of the Navigation apps on android and iPads and noticed that they seem to be a little better on the iPads. Some even have more features  on the iPad versus the android (i.e. WingX Pro).

Also, 32GB is more than enough (as of 2018) to run the navigation apps with all charts loaded and everything turned on including synthetic vision, assuming that it is a dedicated flight tablet and you don't have it loaded down with a bunch of other content such as videos, songs, pictures, etc. Also, you'll want to install just one navigation app, if you install multiple, and download all the charts for each one, it duplicates all the data and will use up your 32GB quickly.

I have ADS-B external antenna and it works just fine with either. The ADS-B I used creates a local wifi signal that the tablet connects to the antenna and all of the traffic and weather data is incorporated into the app. In other words, ADB-B data should work with any tablet that has wifi capabilities.


Can any conclusions about aerodynamic efficiency be drawn on the basis of fly-by noise? Edit: I'm beginning to think this is more suited to the physics stack exchange, but I'll keep this here for a while...
Being bored mindless, surfing the interwebz, I came across this video, where a Sukhoi SU-57 is performing aerobatics:
Youtube: Су-57 с новым звуком пилотаж на форуме Армия 2020 Кубинка
At timestamp 1:45 the plane makes a pass, emitting a distinct screech with prominent components at about 1000, 2500 and 3600Hz.
This screech may very well be from external "add on" equipment such as radar reflectors (see this Q&A), as I kind of combine such noise to some kind of "fault" in the aerodynamics, and therefore I think during design phase sources of such disturbances in airflow would be eliminated from the airframe.
As first hand observations from real life, two examples: sailplanes and the B757, close encounter of which I have found to be memorable: the sailplanes for being very quiet, emitting a slight whisper with maybe a dash of a faint whistle at a high speed fly-by, and the B757s making a very distinct and sharp hizz on short finals (B757 is categorized as "heavy", not due to its size or mass, but for the nasty wake turbulence it makes).
So: can one draw conclusions about planes aerodynamic efficiency based on acoustic observations, and if so, to what extent?

Invariably, aerodynamic efficiency improves with newer designs and so it was from 747-200/300 (not glass cockpit) to 747-400 (winglets + increased span + glass cockpit) to B777 to B787, from A300 to A350. Industry wide pilots were never disappointed by this and proud to be flying the latest lowest drag 'slippery' airplane.
But using noise as an indication of aerodynamic efficiency, could have peculiar factors come into play. The ultra quiet and ultra efficient B787 is so 'clean' or 'slippery' that it requires great anticipation and confidence in technique to fly both the 'speed control' and the CDA Continuous Descent Approach as published at some very major airports.
Many a time, it cannot be flown without the use of speed brakes, the use of which, is (was?) anathema for many pilots.
The  normal expectation is that as long as the speed is above the selected or target speed with speed brakes deployed to aid in reducing the speed, and especially during descent/ the engines would be at flight-idle. Contrary to this, a design feature of the autoflight system pushes the thrust levers up so that they are not at idle but producing thrust when the pilot is doing her best to make the airplane decelerate! So, earlier generation airplanes would have thrust at idle at these points, but the 787 does not.
Even under these circumstances it probably has a smaller noise footprint but an inability to decelerate as per the ATC published speed control targets, could for eg result in gear being lowered earlier than the published preference and this all adds to the sound. The Gear extension point is actually being monitored for variations at such airports.
Despite the above information, theoretically, aerodynamic efficiency could certainly be gauged on the basis of noise provided you were to compare like to like - the comparison would have to be between aircraft similar category, all the airplanes would have to be doing the same maneuver in equivalent configuration eg.

passing 500ft on final approach, max landing weight, landing config with gear down, on speed, and stabilised on approach

OR

level fly by in clean config, height 400ft, 270kts speed.

And there's no accounting for what factors, apart from aerodynamics and engines maybe discovered to be contributing to the noise level.


What information does a pilot have about aircraft operating on an intersecting runway? This incident at O'Hare from July 2006 made me wonder what information is available to a pilot (specifically, in an airliner) regarding aircraft that are using an intersecting runway.

In this incident, the controller had a United 737 line up and wait on 27L because the United flight wasn't ready to go yet while an Atlas 747 was on final for 14R. Once the United pilots radioed that they were ready, tower cleared them for takeoff on 27L, despite the fact that the Atlas 747 was touching down on 14R and was about to cross 27L on the roll-out. The Atlas flight did call out that he was on final, but that's the only indication I can see from the video that the United pilot has regarding the position of the Atlas flight. Judging from the below airport diagram, it appears that the ORD terminal would have been between the two aircraft at the time the United pilot was cleared for takeoff, so the aircraft wouldn't have been able to see each other until they approached the intersection.

Obviously, the controller shouldn't have cleared the United flight for departure until Atlas was out of the way. However, given that he received the takeoff clearance from Tower, I'm wondering whether the United pilot would have had any other tools at his disposal to detect the position of the Atlas 747 and realize that the controller made a mistake (before he saw a giant 747 roll out in front of him on the runway and before the controller realized his mistake.) Specifically, do airline pilots have any additional means for determining the position of other aircraft on intersecting runways aside from relying on ATC, listening to the Tower frequency, and looking out the window?

I'm aware of TCAS for use in-flight, but I'm not familiar enough with it to know if it would help in an intersecting runway situation like this where both aircraft are on the ground.

As the question mentions, good situational awareness is an excellent safety tool. ATC is responsible for runway separation at towered airports, but pilots can play an important part of backup in the case of a human mistake.

The United pilots may or may not have been able to see the Atlas 747 on TCAS, as the terminal building that obstructed their view could also have blocked the transponder signal. TIS-B (Traffic Information Systems - Broadcast), a part of ADS-B, provides traffic both in the air and on the ground. ADS-B was not available in 1996, but if the same situation happened today and the United aircraft had an ADS-B signal on the surface and displayed TIS-B information, they would see the Atlas 747 on their displays. Whether or not that information would be useful to avoid an incursion in a cluttered runway environment is unclear.

The FAA is implementing a system to provide exactly the type of warning you're describing. Runway Status Lights (RWSL) use surface RADAR and lights embedded in the pavement to detect conflicts and alert pilots that a runway is unsafe to enter or take off from. In this situation, the United pilots would have seen red takeoff hold lights to inform them that the runway is unsafe for departure. The FAA plans to have RWSL operational in 17 airports, including Chicago O'Hare, by 2017.


Why do localizer/glideslopes use 90/150Hz specifically? Why is it that localizer and glideslope system are using 90 Hz and 150 Hz frequencies only, instead of some other LF such as 75 Hz?

Part two of my question:
How does the modulation depth differ for aircraft using localizer and GS receiver?

The frequencies are chosen to allow the system to produce a localizer and glideslope 'beam' that provides proportional guidance that can adequately guide an aircraft on the approach.

Read through this Question and Answer.

As you can see in the description of the beam-forming, the width of the antenna array and the choice of the modulation signals (90 and 150 Hz) drive the ddm proportionally to the angle of approach to the antenna array.

There are also considerations tied to the broadcast signal. Higher frequencies would require more bandwidth which would impact channel spacing.

Ultimately, the choice of the two frequencies is an optimization of a design for the approach guidance. For any given runway the current system can be set to provide consistent guidance (+/- 350 feet == full scale deflection) at the runway threshold.  This is done by adjusting the distance between elements of the antenna array.


What is the true meaning of the word “wilco” when used on the radio? What is its origin? Pilots often learn to use the word "wilco" on the radio through contextual interpretation. During my experience as a pilot communicating on the radio I have often observed pilots using the word "wilco" improperly. What is the true meaning of the word "wilco" and what is its origin?

"Wilco" is short for the phrase "will comply," meaning that the speaker will follow the instructions to which they are replying. Merriam-Webster places the origin at 1938, some time after the invention of radio, likely in military usage.

Although the phrase "roger wilco" is sometimes used, it is considered redundant since the "roger" (meaning "received and understood") is implied.


What is "required navigation performance" or "RNP"? I understand that this is some sort of on-board navigation monitoring and alerting...what is it used in? Do the Garmin G500s, G1000s, or the G430s use it? Where can you find it? I know nothing about this and I am trying to figure out what it is.

RNP (Required Navigation Performance) is a standard which avionics manufacturers may choose to design/certify their products for.  It guarantees a particular level of navigation performance that routes and procedures can be designed around, and not have to worry about how the navigation is being conducted, but only that it will meet requirements.

A particular product may be certified to various levels such as RNP10, RNP5, RNP2, RNP1, RNP0.3, etc. (accurate to within 10NM, 5NM, 2NM, 1NM, 0.3NM, etc.).

To see if a particular unit is certified for RNP, and to what level, you would need to look in the aircraft flight manual / supplement and see what it says (note that this is installation specific too, as it involves antennas and "full system" performance, not just the capability of one piece of the puzzle).

The FAA has an advisory circular caled AC 90-101A - Approval Guidance for Required Navigation Performance (RNP) Procedures with Authorization Required (AR) Including Change 1 if you want more technical information on it.


Do flying boats carry anchors? Inspired by the first comment here, and considering they are called "boats", do flying boats carry anchors?

According to a story in Flying Magazine Nov 1956, the Grumman SA-16 Albatross in that story (see page 58) carried an anchor.

For pre-flight, the FAA says:

  Check that necessary marine and safety
  equipment, such as life vests, lines (ropes), anchors,
  and paddles are present, in good condition, and
  stowed correctly.

(FAA)

(wikimedia.org) Nose access on the Albatross.

The answer seems yes.


What is the minimum glide ratio of a motorized glider? What is the minimum glide ratio of a motorized glider, enough to climb in typical summer afternoon thermals over a dark field or similar?

In other words, at what minimum glide ratio would a glider be considered more of an ultralight rather than a glider, at least conceptually, or based solely on glide ratio?

I don't think anyone would consider an aircraft a "motorized glider style", irrespective of the class the aircraft is registered in,if the glide ratio is 4:1.

A glide ratio of 20:1 seems like a more realistic cutoff. Is this correct, at least conceptually?

The minimum glide ratio of any aircraft is zero. Just put it into a vertical dive. Of course this is not sustainable; either you overspeed or collide with the ground.

in order to be certified as a powered sailplane (that is bureaucrat talk for motor glider), EASA CS-22.1 demands a ratio of weight to span squared of less than 3. The second limit is a maximum weight of less than 850 kg. That the code gives the maximum weight in Kilogramms and not in Newtons shows that the weight figure limit of 3 needs to be calculated with the mass of the aircraft, not its weight.

Initially, the criterium was a minimum sink rate of less than 1.0 m/s. That number was raised to 1.2 m/s when the first batch of glassfiber models could not meet that target. The mass per span squared rule came into force in 2003.

The defining criterium for an ultralight depends on the local rules and is a maximum take-off mass of 300 kg or less for single-seaters or 450 kg for two-seaters in Europe. Within the ultralight class there is no motorglider category.


What is the exact definition of Taxi Time? I found some definitions on the web, but they weren't same.

Some resources mentioned it is sum of the times the aircraft is moving on the ground with its own engines. Some defined it as the time between chocks-on and take-off.

As always, the definition depends on the context. That is why official documents always included the definitions of important terms used in the text.
For Collaborative Decision Making (CDM) as defined  by EUROCONTROL in the latest CMD manual (2017), taxi time is divided in taxi-out time and taxi-in time.

3.4.2 Definition of Taxi Time
For Airport CDM purposes, taxi time is considered to  be:

For arriving flights: the Actual taXi-In Time (AXIT)  is  the  period  between  the  Actual  Landing  Time   (ALDT) and the Actual
In-Block Time (AIBT)
For  departing  flights:  the  Actual  taXi-Out Time   (AXOT) is the period between the Actual Off-Block Time (AOBT) and the Actual
Take Off Time (ATOT).

For  calculation  purposes  within  the  CDM  Platform, taxi times
will be referred to as estimated taxi-in (EXIT) and estimated taxi-out
(EXOT) as there is no requirement for a scheduled, actual or target
taxi time.

Now that in itself doesn't help if you don't know how the ALDT, AIBT, AOBT and ATOT are defined.
The ALDT is the same as the ATC Actual Time of Arrival, which is the time the aircraft touches down.
The AIBT is the actual time when the parking brakes have been engaged at the parking position. (source)
The AOBT is the time the aircraft pushes back / vacates the parking position. (source)
The ATOT is the same as the ATC Actual Time of Departure, which is the time the aircraft lifts of from the runway.
Now Taxi time defined as above is used in Airport management, Air Traffic Management. It may be different in other areas.
Some observations that I want to make given the above definition:

De-icing on-stand is excluded from the taxi-time. De-icing on a remote de-icing pad is included in the taxi-time.
The take-off run is included in the taxi-time.
The landing run is included in the taxi-time.
Taxiing between stands or to/from maintenance is not defined.


Are taxiways always one-way towards a specific, fixed direction? I was studying the airport diagram of JFK and I began to wonder if aircrafts use taxiways as a one-way road. In case they do, is the direction of a taxiway fixed or does it change according to the daily needs of the airport?

At any given moment they are generally one direction as planes cant really turn around like cars but the taxi way its self can typically support traffic in either direction. Airports do have a "flow" to them but it depends on the runway they are using as well as the direction of departure of that runway. If the wind shifts and the approach is taken from the opposite direction the controllers will "turn the field around".

This time-lapse video shows the principal pretty well, the aircraft are pushed out onto the ramp form the jet bridge, nose towards the taxiways. They then head out to the departure end of the runway all following generally the same path. They queue up and depart when cleared. If the wind were to shift around they would do so from the other end of the runway which would reverse the flow (generally speaking) on the field.

You can find the FAA's advice on designing taxi ways here.

At uncontrolled airports the pilot can turn the field around.


What are the ICAO fuel reserve requirements? How much reserve fuel are private and commercial aircraft required to carry by ICAO rules?

I heard that it changed recently (about a year ago) and is a little complicated.  How is it calculated for a particular flight?

The following includes the changes you allude to (which were proposed in ICAO State Letter SP 59/4.1-11/8 on June 30, 2011).

Commercial Flights

Per ICAO Annex 6, Part I, section 4.3.6 "Fuel Requirements," airplanes should calculate their required fuel quantity as follows (summary; see below for actual ICAO text):

Taxi fuel
Trip fuel (to reach intended destination)
Contingency fuel (higher of 5% of "trip fuel" or 5 minutes of holding flight)
Destination alternate fuel (to fly a missed and reach an alternate)
Final reserve fuel (45 minutes of holding flight for reciprocating engines, 30 minutes for jets)
Additional fuel (if needed to guarantee ability to reach an alternate with an engine failure or at lower altitude due to a pressurization loss)
Discretionary fuel (if the pilot in command wants it)

General Aviation

For general aviation, ICAO Annex 6 Part II, section 2.2.3.6 "Fuel and oil supply" requires:

For IFR, enough fuel to reach destination, then alternate (if required), plus 45 minutes
For day VFR, enough fuel to reach destination plus 30 minutes
For night VFR, enough fuel to reach destination plus 45 minutes

ICAO Annex 6 Part I

From the ninth edition:

  4.3.6.3 The pre-flight calculation of usable fuel required shall include:

  a) taxi fuel, which shall be the amount of fuel expected to be consumed before take-off;

  b) trip fuel, which shall be the amount of fuel required to enable the aeroplane to fly from take-off, or the point of in-flight
  re-planning, until landing at the destination aerodrome taking into account the operating conditions of 4.3.6.2 b);

  c) contingency fuel, which shall be the amount of fuel required to compensate for unforeseen factors. It shall be five per
  cent of the planned trip fuel or of the fuel required from the point of in-flight re-planning based on the consumption
  rate used to plan the trip fuel but, in any case, shall not be lower than the amount required to fly for five minutes at
  holding speed at 450 m (1 500 ft) above the destination aerodrome in standard conditions;

    Note.— Unforeseen factors are those which could have an influence on the fuel consumption to the destination
    aerodrome, such as deviations of an individual aeroplane from the expected fuel consumption data, deviations from
    forecast meteorological conditions, extended taxi times before take-off, and deviations from planned routings and/or
    cruising levels.

  d) destination alternate fuel, which shall be:

  where a destination alternate aerodrome is required, the amount of fuel required to enable the aeroplane to:
  i) perform a missed approach at the destination aerodrome;
  ii) climb to the expected cruising altitude;
  iii) fly the expected routing;
  iv) descend to the point where the expected approach is initiated; and
  v) conduct the approach and landing at the destination alternate aerodrome; or
  where two destination alternate aerodromes are required, the amount of fuel, as calculated in 4.3.6.3 d) 1),
  required to enable the aeroplane to proceed to the destination alternate aerodrome which requires the greater
  amount of alternate fuel; or
  where a flight is operated without a destination alternate aerodrome, the amount of fuel required to enable the
  aeroplane to fly for 15 minutes at holding speed at 450 m (1 500 ft) above destination aerodrome elevation in
  standard conditions; or
  where the aerodrome of intended landing is an isolated aerodrome:
  i) for a reciprocating engine aeroplane, the amount of fuel required to fly for 45 minutes plus 15 per cent of the
  flight time planned to be spent at cruising level, including final reserve fuel, or two hours, whichever is less;
  or
  ii) for a turbine-engined aeroplane, the amount of fuel required to fly for two hours at normal cruise
  consumption above the destination aerodrome, including final reserve fuel;

  e) final reserve fuel, which shall be the amount of fuel calculated using the estimated mass on arrival at the destination
  alternate aerodrome, or the destination aerodrome when no destination alternate aerodrome is required:

  for a reciprocating engine aeroplane, the amount of fuel required to fly for 45 minutes, under speed and altitude
  conditions specified by the State of the Operator; or
  for a turbine-engined aeroplane, the amount of fuel required to fly for 30 minutes at holding speed at 450 m
  (1 500 ft) above aerodrome elevation in standard conditions;

  f) additional fuel, which shall be the supplementary amount of fuel required if the minimum fuel calculated in accordance with 4.3.6.3 b), c), d) and e) is not sufficient to:

  allow the aeroplane to descend as necessary and proceed to an alternate aerodrome in the event of engine failure
  or loss of pressurization, whichever requires the greater amount of fuel based on the assumption that such a failure
  occurs at the most critical point along the route;
  i) fly for 15 minutes at holding speed at 450 m (1 500 ft) above aerodrome elevation in standard conditions; and
  ii) make an approach and landing;
  allow an aeroplane engaged in EDTO to comply with the EDTO critical fuel scenario as established by the State
  of the Operator;
  meet additional requirements not covered above;

    Note 1.— Fuel planning for a failure that occurs at the most critical point along a route (4.3.6.3 f) 1)) may place
    the aeroplane in a fuel emergency situation based on 4.3.7.2.

    Note 2.— Guidance on EDTO critical fuel scenarios is contained in Attachment D;

  g) discretionary fuel, which shall be the extra amount of fuel to be carried at the discretion of the pilot-in-command.

ICAO Annex 6 Part II

  2.2.3.6 Fuel and oil supply

  A flight shall not be commenced unless, taking into account both the meteorological conditions and any delays that are
  expected in flight, the aeroplane carries sufficient fuel and oil to ensure that it can safely complete the flight. The amount of
  fuel to be carried must permit:

  a) when the flight is conducted in accordance with the instrument flight rules and a destination alternate aerodrome is
  not required in accordance with 2.2.3.5, flight to the aerodrome of intended landing, and after that, for at least 45
  minutes at normal cruising altitude; or

  b) when the flight is conducted in accordance with the instrument flight rules and a destination alternate aerodrome is
  required, flight from the aerodrome of intended landing to an alternate aerodrome, and after that, for at least 45
  minutes at normal cruising altitude; or

  c) when the flight is conducted in accordance with the visual flight rules by day, flight to the aerodrome of intended
  landing, and after that, for at least 30 minutes at normal cruising altitude; or

  d) when the flight is conducted in accordance with the visual flight rules by night, flight to the aerodrome of intended
  landing and thereafter for at least 45 minutes at normal cruising altitude.


What is the maximum speed for regulation of sonic boom noise? If fuel cost and fuel efficiency were not the issue, what is the maximum speed (air speed and ground speed) that business jets or airliners could travel at without exceeding the maximum noise and sonic boom allowed or as regulated in the USA, Europe and the rest of the world.  I need to know why there are no faster business jets and for business class airliners given that private and business fliers are prepared to pay a premium

Business jets are developed to different rules than airliners. The biggest difference is that, indeed, fuel price and fuel efficiency are not an issue when what counts are bragging rights for the fastest plane on the ramp. Their speed has steadily increased and is now at Mach 0.935 for the fastest models. Compare that to Mach 0.78 to 0.85 for regular airliners.
Supersonic business jets were proposed several times in the last decades, but so far nobody has risked to spend the money it needs to bring one design to a type certificate.
Since supersonic flight over land is heavily restricted, the fastest speed would be Mach 0.99. However, since the speed of sound decreases with increasing altitude in parallel with air temperature, what is Mach 1.15 in 40.000 ft becomes only Mach 0.998 on the ground, so the shock will disappear close to the ground. If the goal is to avoid the shock on the ground, flight speed high up can very well be mildly supersonic. However, this will place the airplane close to its drag maximum, giving it exquisitely poor efficiency for a small gain in speed.


What are the differences between a slot and a slat? If you look at image 5-18 in the PHAK Chapter 5 about leading edge lift devices you see this:

However the paragraph preceding it states

  High-lift devices also can be applied to the leading edge of
  the airfoil. The most common types are fixed slots, movable
  slats, leading edge flaps, and cuffs.

So is this a typo? Should the image say 'movable slat' instead of 'movable slot'?

This leads into my main question which is, what are the differences between a slat and a slot? If I were to get asked this by an examiner what would a good response be?

I guess it should be movable slat.

A leading edge slot is basically a spanwise opening in the wing. Slats are aerodynamic surfaces in the leading edge, which when deployed, allows the wing to operate at higher angle of attack. When deployed, the slat opens up a slot between itself and the wing.

Image from simhq.com

In some aircraft, the slats are fixed, which opens up a slot between the wing and the slat. In this case, the terms slot and slat are used interchangeably.

"Leading edge slot" by Sanchom - Own work. Licensed under CC BY 3.0 via Commons.

A number of airliners use movable slats, in which case, the system is called slat, rather than slot.

"Voilure A319" by Nicourse - Own work. Licensed under CC BY-SA 3.0 via Commons.

In short, the system is pretty much the same, but is (usually) called slat in case of movable one and slot in case of fixed one.


What is the difference between EPE and HUL on the Satellite Status Page of GNS systems? For exemple on the GNS430 satellite status page you can read, in addition to the GPS receiver status :

EPE (Estimated Position Error)
DOP (Dilution of Precision)
HUL (Horizontal Uncertainty level)

I found here explanations about DOP computation, and GNS430 manual states that:

  "EPE uses DOP and other factors to calculate a horizontal position error, in feet or meters".

About HUL, the same manual explains that

  "the Horizontal Uncertainty Level displays a 99% confidence level that the aircraft position is within a circle with a radius of the value displayed in the HUL field"

It seems to me that EPE and HUL are exactly the same thing and differ only by the confidence level. If it's the case, what is the confidence level of the EPE ? If not, what is the difference between EPE and HUL ?

EPE is the 1-sigma error level and thus represents the position error circle with a 68% confidence level. Reference: NPS


Can I use an expired IFR-certified GPS with an out of date database in lieu of DME? I know I should update the database in my GPS, but nevertheless I'm wondering if i can use an expired IFR-certified GPS with an out-of-date database in lieu of DME

The answer would appear to be "Maybe", per the AIM (table 1-1-6): You are permitted to use an IFR-approved GPS "In Lieu of ADF and/or DME", however the footnote (3) to that table tells us that this use

  Requires current database or verification that the procedure has not been amended since the expiration of the database.

So if you're using the GPS to calculate something like "5 Miles DME from JFK VOR" that would seem to be acceptable (the FAA is unlikely to pick up JFK VOR and move it without making a lot of noise about it), but if you're using by punching in a fix that's defined by DME and a radial you would need to somehow verify that the fix hadn't been redefined.

You can accomplish that verification in a number of ways (a current IFR chart on your iPad or a current paper chart seem like obvious ways). As long as you can satisfy yourself (and the FAA) that the data in the GPS is accurate the operation would appear to be permissible.

It would also appear that if you verify that the fix has been redefined (say FUBAR was 5 DME, now it's 6 DME) you could still use the GPS distance data in lieu of DME, just not the incorrectly-programmed fix. That is, you could determine when you're 6 miles DME from JFK VOR, and since you know the FAA didn't move the VOR and that the fix is now at 6 miles you now you're where you want to be.


Do pilots make a lot of money? How much money do commercial pilots make per year, and per hour? Is there significant non-monetary compensation, such as free hotels stays and food?

I can only answer from a US standpoint as that is the jurisdiction I know best, elsewhere in the world things may be different.

The first thing you can check is this data from the Bureau Of Labor And Statistics according to their data

  2015 Median Pay

  The wage at which half of the workers in the occupation earned more
  than that amount and half earned less. Median wage data are from the
  BLS Occupational Employment Statistics survey. In May 2015, the median
  annual wage for all workers was $36,200.

  For Pilots the 2015 median pay was 102,520 USD per year

You should read over this article as well as it covers a wide variety of how pilots are paid and the such.

Here is some more data on salary as well. You should how ever note that for many articles the data is submitted by choice and may not accurately reflect the true pay scale.

Here is some discussion on the per hour pay but I should caution you to be weary of per hour statistics for pilots. In many cases these numbers are computed using flight hours which does not accurately reflect how much a pilot may work as there is more time involved in a flight than just what the hobbs meter records. Here in the US it is my impression most commercial (121) pilots are salaried.

My two flight instructors recently went to the regionals after completing their ATP hours from talking to them it is evident that starting pay is very low (under 30K a year).

One interesting (and often debated issue) is that the FAA requires pilots to retire at 65 (was previously 60). This in theory puts a cap on their earning potential as an airline pilot (however they can fly non 121 operations like a 135 charter afterwords).

As for perks, that depends on the airline (and may to some extent depend on seniority). Its common to get some comped tickets for family members and the such but its not what it once was. I have heard that many pilots can fly standby on their own (or in company) airlines for free. They may also be able to ride in the jump seat if there is one. This can be attractive for a young single pilot but is not very efficient for family travel.

Free hotels and things will depend on the route you are flying. If overnight stay is required they may put the pilot up (i.e. long haul routes) but you should not expect 5 Star Penthouses and bottomless lobster dinners. However there are plenty of short routes for which a pilot may end up back at their base at the end of their shift.

If you are looking for a decent overview of the pilots life I would advise picking up a copy of Cockpit Confidential it has a lot of the answer you may be looking for and is very to the point.


Does the wing always have an adverse pressure gradient along the chord? I know that there is an adverse pressure gradient on the upper surface of the wing, which leads to boundary layer separation.

Is there any condition under which there is no such adverse pressure gradient on the wing?

At the trailing edge of the upper surface, you will always have a pressure recovery as low pressure from the upper surface converges toward the high pressure from the bottom surface at its trailing edge. This is the adverse pressure gradient since pressure is increasing along the chord length. The gentler the pressure recovery, the less likely is the airfoil to have an adverse boundary layer velocity profile, which is the source of flow separation and stall.

Source: https://www.researchgate.net/figure/Airfoil-Cp-vs-x-c-curve_fig9_306374523

Since most of the lift is through the suction from the upper surface, I don't think you will encounter a practical airfoil without pressure recovery.


Do I need to register my drone? Recently the FAA released some new regulations that require drone operators, including hobbyist, to register drones with the FAA.

As I am a novice in both aviation and legalese, can someone please break down the regulations and give me a guideline in layman's terms for whether or not I need to register a drone?

If:

Your unmanned aircraft weighs between 250g and 25kg (including fuel and cargo),
You are not flying under the Special Rule for Model Aircraft, also known as section 336
You intend to operate it outdoors, and
You are operating it in the United States,

you need to register your drone through the FAA's online registration system.  If your drone is heavier than 25kg, you need to go through the regular aircraft registration process.  If your drone is ligher than 250g, or you are only operating it indoors, you do not need to register it.

Additionally, if you are operating the drone for commercial purposes, you must have a remote pilot airman certificate.

(Note: if you are younger than 13 years old, someone who is 13 or older needs to register your drone for you.)


Why did my LGA-ORD flight make an S-shaped turn round the time it was passing a storm? On a recent United UA1709 flight into Chicago (hit by a heavy storm at the time), I felt a noticeable descent, combined with two wide banks around 1 hour before landing. Looking at the flight path, I see an S shape that deviates from the original flight path.

Looking at the altitude readings here, the plane registered a descent of around 3000 fpm around the time of the turns from a cruising height of 30000 ft to 21000 ft. This descent took the plane under cloud cover and into the storm, so I am certainly confused as what motivated this flight path. Given that the flight was an hour away from landing, I find it hard to believe that this was a holding pattern of some sort.

Some more things that I noticed during this flight (not sure if relevant) was that a few minutes after this, I noticed lights indicating a plane flying directly above (hard to estimate distance given bad visibility). Furthermore, in-flight WiFi briefly cut out for a few minutes.

Can anyone explain what happened here?

I find it hard to believe that this was a holding pattern of some sort.

Believe it. An hour before landing would be about the point at which the aircraft will start its descent to its destination. Almost certainly, air traffic control were delaying your flight for a few moments to ease insertion into the landing pattern at Chicago. Doing this at altitude burns less fuel than waiting until the aircraft is lower down.

The storms were incidental. Had the pilots been avoiding the weather they'd have diverted north or south and then resumed their route. A large S-bend wouldn't be necessary.


Why does the A320 right aileron float on dual engine failure? On this question for the A320 after dual engine failure it says:

  When the hydraulic power is lost, the right aileron is lost, and is in the upfloat position.

Why would this affect only the right aileron?

Assuming it's zero fuel dual engine failure with no chance of powering up the APU, the plane is left with the Ram Air Turbine (RAT).

1. The emergency electrical configuration only powers ELAC 1, one of the two units that control the ailerons, and ELAC 2 is lost (see below).

(A320 FCOM)

2. The RAT powers only the Blue hydraulic system.

Add those two conditions with the color coded schematic below:

(Airbus Training Manual)

And the right aileron will not be powered. The same schematic can be found in the FCOM under Flight Controls > General > Architecture (27-10-20), the one above is clearer though.


How is V_S0 calculated for anything less than maximum weight? Is there a way to (safely) calculate the stall speed of an aircraft ($V_{S0}$) for anything below maximum weight? All the tables in the POH are valid for maximum weight only, and stall speed can drop significantly with a light load. As a consequence, if you're flying the published (max weight) $V_{ref}$ on final, you'll actually be carrying a significant amount of extra speed and thus increase the required landing distance, possibly in quite a dramatic fashion.

All aerodynamic forces are proportional to the dynamic pressure, which is the product of air density $\rho$ and half of the square of flight speed $\frac{1}{2}v^2$. If your flight mass is reduced, reduce the dynamic pressure proportionally to keep all other parameters the same. To express this in terms of speed, you need to multiply the posted speed in the handbook with the square root of the mass ratio, like that: $$v_{reduced\,mass} = v_{full\,mass}\cdot\sqrt{\frac{reduced\,mass}{original\,mass}}$$


Does static longitudinal stability require download on the tail? After having encountered this meme too often for comfort, I ask myself today in order to have the possibility to explain the issue in detail.

No, static longitudinal stability does not necessarily imply a download on the tail.

Static longitudinal stability requires that the Centre of Gravity is in front of the Centre of Lift, indicated as n.p.$_{fixed}$ in the drawing. Only then will an increase in Angle of Attack d$\alpha$ result in an opposing pitching moment: if d$\alpha$ > 0 then $dC_N$ > 0, resulting in a higher lift force. The neutral point must be behind the CoG in order to transform the higher lift into a nose down moment. Note that the drawing shows a longitudinally stable situation with a positive lift on the horizontal tail.


Need help identifying civilian small aircraft from old turkish movie I need help identifying a plane from an older 1977 turkish comedy movie for a personal project, these are the best (and only) shots it can be seen.
Flyby
Front Angle
Close up cockpit outside

It is a Cessna 188 crop duster. The giveaway is the shape of the cooling air inlets on either side of the prop, which are "Cessna-shaped", as opposed to those on the similar Piper Pawnee which are rounded.


Is a class B endorsement required for a Private checkride? I was just wondering if a Class B endorsement was required for a Private Pilot Check-ride in the US?

You do not need a Class B endorsement for your PPL Check ride.

By the time you get to you check ride you should have the first 8 endorsements from this list, provided by the FAA.

I will add one caveat to this. During your check ride your examiner will ask you plan a cross country flight. If the route calls for it and you have the endorsement you can plan it through Class B. However if you plan it through Class B your examiner may ask for the endorsement or try and trip you up over it. if you plan a course through Class B without the endorsement the DPE may not stop you when you get in the air. Be careful as you can bust a checkride for this.


Are private jets allowed to land at London Heathrow? Heathrow is among the worlds busiest airports, with traffic mostly (entirely?) from airliners. Are private/business jets (e.g. Gulfstream G650 or Cessna Citation X) allowed to land at Heathrow?

If so, what are the landing fees and what criteria do they use in charging them?

The answer appears to be "yes", but unless you're transferring directly from the private jet to/from an international flight in/out of Heathrow, it's a poor choice. Fees are high and delays are common.

With no fewer than 13 other airports to choose from, chances are that one of the others will be a better choice. Luton and Farnborough are the most popular choices for private jets.

Reference:

PrivateFly: Inside London Airports - Private Jet & Helicopter charter


Would it take 7 to 10 times more energy to lift a turbofan-helicopter? I want to figure out how much energy it would take to lift a turbofan-helicopter.

For reference I started with a rotor helicopter and assumed $T=100\ \mathrm{kN}$ gross weight and $d = 16\ \mathrm m$ rotor diameter (compare S92 or AH64).

Using the propeller-formula
$$
T = ( 0.5*P^2*\eta_\text{tot}^2*\pi*d^2*\rho_\text{air})^{1/3}.
$$

with $\eta_\text{tot}^2=0.58$ (source) I get an engine-output of $P=1\,870\ \mathrm{kW}$

If I now take a typical turbofan and a take-off $tsfc$ of $10\ \mathrm{g/(kNs)}$ I get a fuel consumption of $1\ \mathrm{kg/s}$ for my $100\ \mathrm{kN}$ helicopter. If I furthermore assume 30% overall efficiency and $E_\text{Jetfuel}=43.5\ \mathrm{MJ/kg}$ I get an energy demand of $13\,050\ \mathrm{kW}$ to run the fan (neglected all the other stuff taking energy from the shaft).

Does this mean it would take 7 times the amount of energy to lift a turbofan-helicopter (with engines running at full throttle)? Or a magnitude if I assume cruise tsfc...

Does this suit with your experience? Or is there a big error/misconception in my short calculation?

Helicopter rotors are very large precisely for that reason. Lift from a rotor (or thrust from a propeller or fan) is obtained by accelerating a given mass of air m to a velocity v. The thrust obtained is proportional to the increase of momentum ∆mv. Obviously, you can get the same ∆mv by accelerating a given mass of gas to a high speed (propeller/fan) or by accelerating a larger mass to a lower speed (rotor). But the energy needed is proportional to v squared... Hence, and for the same thrust/lift, it's much more expensive, in energy or power terms, to use a propeller/fan than a big rotor ...


When does the FAA require OEM involvement for the approval of an STC? There appear to be many instances when companies modify aircraft (or introduce after-market systems) without the involvement of the original equipment manufacturer (OEM), up to conversions of passenger aircraft to freighter aircraft.

Is there guidance from the FAA on when an aircraft modification requires the involvement of the OEM?

It tends to go on a case by case basis.  OEMs tend to steer clear of STC developers because OEM involvement tends to drag the OEM into an implied commitment to support the STC itself, or support the STC's secondary effects on how the airplane is operated, that the OEM would rather not be stuck with.

What will happen is an STC developer will submit a certification application with documentation, test reports and all that, to the regulator, and most of the time the regulator will approve the STC independently of the OEM.  But there may be cases where the regulator's engineering group will demand OEM engineering input, or at minimum an "NTO Letter" (NTO = No Technicial Objection) before approving the STC.

In such a case the ball is in the OEM's court and if the OEM insists on not getting involved, well the STC developer is stuck and the project might die on the vine unless they find some other work-around.

In other cases however, the OEM may actively support an STC application where they would like to see the mod go into service because there is a benefit to the OEM.  You might see this for a mod that improves fleet reliability, or is just really popular with operators, but where the OEM lacks the internal resources to develop it in-house due to budget limitations.


What connector standard is used for aviation headsets? The typical aviation headset features two cords with connectors that at first glance are identical. One is a standard 1/4" (0.25 inch) stereo audio jack.

What kind of connector is the slightly smaller, slightly narrower one?

It's for the microphone (the standard sized one is for the head phones). They are different size so the pilot knows to try the other hole if it doesn't fit.

From wikipedia:

  Commercial and general aviation (GA) civil airplane headset plugs are
  similar, but not identical. A standard 1⁄4 in monaural plug, type
  PJ-055, is used for headphones, paired with special tip-ring-sleeve,
  0.206 inch diameter plug, type PJ-068, for the microphone. On the microphone plug the Ring is used for the microphone 'hot' and the
  sleeve is common or microphone 'Lo'.


What are the differences between Lycoming and Continental engine designs? Inspired by a discussion in chat.

Most GA piston singles are powered by either Lycoming or Continental engines.
The engine designs used by both manufacturers are broadly similar (4-cycle, horizontally-opposed, gasoline-powered, air-cooled), and they're both generally available with either carburetors or fuel injection, but I know they're not "identical products".

What are some of the differences between the designs used by the two manufacturers, and what practical implications do those choices have for pilots?

Lycoming engines have the camshaft above the crankshaft, and Continental engines have the cam below the crankshaft.  This seems to keep the Conti cams better oiled and therefore less susceptible to corrosion.


Was the Shuttle Orbiter in contact with air traffic control during its descent & landing? The Shuttle Orbiter crew were obviously in contact with ground control in Houston during their landing, but were they also in contact with any air traffic control, especially once they reached US airspace? Was US ATC involved in the landing in any way other than keeping other traffic out of their way?

Well, sort of. The Kennedy Space Center, where the shuttle operations were conducted, has an ATC. but then, the show was run by NASA, not FAA.

The shuttle operations were coordinated through the Aerospace Control Officer (ACO) at the Air Force 45 th Space Wing’s Eastern Range (it used a military TACAN). FAA was informed of the shuttle landing and nothing else. NASA simply cleared the airspace for a 30 mile radius around the intended landing site to prevent collisions.

In the trajectory of the shuttle landing, FAA issued a NOTAM called 'Space Shuttle Landing Operations Advisory' to warn the users that 25 miles to either side of the nominal reentry trajectory is potentially vulnerable to debris, but the airspace is not closed, like this example:

  FDC 9/1945 (A0856/09) - ...SPACE SHUTTLE LANDING OPERATIONS ADVISORY...
  EFFECTIVE 0911271848 UTC UNTIL 0911271923 UTC SPACE SHUTTLE
  LANDING OPERATIONS 25 NM EITHER SIDE OF THE LINE BETWEEN
  2743S/17214W 0411N/16214W 2925N/13455W 3440N/11828W 3457N/11745W
  FROM SURFACE TO UNLIMITED. WIE UNTIL UFN. CREATED: 25 NOV 21:11 2009

For these actions, Special Use Airspace was activated. The ACO coordinates these actions with the FAA’s ARTCC (Air Route Traffic Control Center) in Miami, Florida


Do regulations require electronic checklists to be displayed on a cockpit screen or EFB? As per regulation is it required to have the checklist (Normal and Emergency (drive by any alert))  as a part of the Cockpit Display System or EFB?

No, nothing in the CFRs requires an electronic checklist.  In fact, almost the reverse is true - from experience I know that part 135 operators need to justify the use of EFBs, and have it approved on their operating certificate.  (i.e. FAA doesn't force them, they must demonstrate that the devices meet applicable standards and basically ask for permission...)
And I don't know of any GA aircraft that have electronic checklists built into their displays, although I cannot say that the capability doesn't exist.
Although many airline and GA pilots fly with EFBs, a great many do not.  It would be a tremendous burden to owners and pilots, and a regulatory nightmare to attempt to enforce the use of electronic checklists.
And there is absolutely no compelling reason to do so... The battery will never run out on a laminated paper checklist, so why would you want to force someone to use a less reliable method?


What is the difference between fixes and waypoints on an arrival plate? This is a followup to my other question on this topic. Figured I'd just make it a whole separate question.

The plates below show STAR arrivals to KMEM. The points along the route are marked with two different symbols. When I look in the FAA guide it refers to the triangular symbols as non-reporting fixes and the star shaped symbols as non-reporting waypoints. What is the difference between the two? Why are they marked with different symbols?

As described in the answer to the previous question, all of the points on the chart are both waypoints and fixes. The difference between the printed icons is how they are identified from the air.

The waypoints marked by hexagons, some with darkened edges and some printed inside a square, note where the waypoint is on top of a VOR. This includes Razorback, Walnut Ridge, Gilmore, and Memphis. The icons with bolded sides are a VOR collocated with TACAN; inscribed inside a square notes a VOR collocated with a DME station.

Triangles are waypoints determined by a radial and distance from a VOR station. The star icons are determined by an RNAV (area navigation) system, which does not require the aircraft to fly a particular VOR radial to determine its course. Note that the procedure you provided is not available for RNAV-capable aircraft, likely because there is an RNAV arrival procedure that is preferred by ATC.

To fly the procedure, starting from the left, a pilot would identify the Razorback (RZC) point by their CDI showing that they had flown over the beacon itself. The next waypoint is MARBI; that is determined by flying along the 098 degree radial to a distance of 34 NM from RZC. Similarly, IGLOO can be identified by flying the 098 degree radial another 85 NM for a total distance of 119 NM. The distinct icons tell pilots how to identify the waypoints using their onboard equipment, but they otherwise have the same meaning.


91 year old father allowed to fly a plane again? My 91 year old father got his private pilots license over 60 years ago. He has not flown an airplane for 35 years and is saying that he can go buy his own airplane, again, and fly it tomorrow legally. He says that there is no one that checks for credentials such as up to date medical. He is 91 years old and thinks he can hop into a plane and pick up where he left off 35 years ago legally. Is this true? If so, very scary to think a 91 year old, who thinks he is just as good of a pilot as he was 40 years ago, could get away with flying a plane without anyone checking.

What Carlo Felicione has posted is true. Your father must have a Flight Review given by an instructor, examiner, or administrator designee within the previous 24 months of any flight of an aircraft where he is acting in the role of Pilot-in-Command. If there is not another qualified pilot at the controls of the aircraft, your father is acting in the role of PIC.

The other issue is his medical status. Given the fact that you have said he has not flown in 35 years, I take it that he had either a private (as you stated) or a commercial pilot certificate and not one of the more recently created licenses. There are varying levels of requirements he has to meet and fulfill based on the type of aircraft operations he is conducting.

In order for him to fly as PIC in a powered aircraft without at least a valid unexpired third class medical certificate, he has to have:

Valid unexpired drivers license
Have been in possession of at least a valid third class medical certificate after July 14, 2006.
Document receiving a comprehensive medical exam to the FAA’s standards from any state-licensed physician of his choice within the last 48 months.
He can not have had his most recent medical certificate or application for a medical certificate denied, revoked, or suspended.
Complete an FAA mandated medical education course on Basic Medical requirements.

In addition...

Title 14 of the Code of Federal Regulations, (Federal Aviation Regulations) Part 61.113 states the following:

  (i) A private pilot may act as pilot in command of an aircraft without holding a medical certificate issued under part 67 of this chapter provided the pilot holds a valid U.S. driver’s license, meets the requirements of §61.23(c)(3), and complies with this section and all of the following conditions and limitations:

  (1) The aircraft is authorized to carry not more than 6 occupants, has a maximum takeoff weight of not more than 6,000 pounds, and is operated with no more than five passengers on board; and

  (2) The flight, including each portion of the flight, is not carried out—

  (i) At an altitude that is more than 18,000 feet above mean sea level;

  (ii) Outside the United States unless authorized by the country in which the flight is conducted; or

  (iii) At an indicated airspeed exceeding 250 knots; and

  (3) The pilot has available in his or her logbook—

  (i) The completed medical examination checklist required under §68.7 of this chapter; and

  (ii) The certificate of course completion required under §61.23(c)(3).

He may, however, fly an aircraft officially designated and certificated by the FAA as a Light Sport Aircraft as long as his most recent FAA Medical Certificate or application for a Medical Certificate was not denied, suspended, or revoked. And, he must not know or have reason to know of any medical condition that would make him unable to operate a Light Sport Aircraft in a safe manner. Also, he can not fly at night, in Instrument weather conditions, or above certain altitudes (the higher of 10,000 feet Mean Sea Level or 2000 Above Ground Level).

  Light-sport aircraft means an aircraft, other than a helicopter or powered-lift that, since its original certification, has continued to meet the following:

  (1) A maximum takeoff weight of not more than—

  (i) 1,320 pounds (600 kilograms) for aircraft not intended for operation on water; or

  (ii) 1,430 pounds (650 kilograms) for an aircraft intended for operation on water.

  (2) A maximum airspeed in level flight with maximum continuous power (VH) of not more than 120 knots CAS under standard atmospheric conditions at sea level.

  (3) A maximum never-exceed speed (VNE) of not more than 120 knots CAS for a glider.

  (4) A maximum stalling speed or minimum steady flight speed without the use of lift-enhancing devices (VS1) of not more than 45 knots CAS at the aircraft’s maximum certificated takeoff weight and most critical center of gravity.

  (5) A maximum seating capacity of no more than two persons, including the pilot.

  (6) A single, reciprocating engine, if powered.

  (7) A fixed or ground-adjustable propeller if a powered aircraft other than a powered glider.

  (8) A fixed or feathering propeller system if a powered glider.

  (9) A fixed-pitch, semi-rigid, teetering, two-blade rotor system, if a gyroplane.

  (10) A nonpressurized cabin, if equipped with a cabin.

  (11) Fixed landing gear, except for an aircraft intended for operation on water or a glider.

  (12) Fixed or retractable landing gear, or a hull, for an aircraft intended for operation on water.

  (13) Fixed or retractable landing gear for a glider.

He may also seek out getting his glider or balloon rating to fly either of those aircraft without a Medical Certificate. This option is a good one for him. But, it will require home to legally get the ratings through an instructor and Designated Pilot Examiner.

the FAA states in 61.107...

  (2) If the applicant has logged at least 40 hours of flight time in a heavier-than-air aircraft, the applicant must log at least 3 hours of flight time in a glider in the areas of operation listed in §61.107(b)(6) of this part, and that flight time must include at least—

  (i) 10 solo flights in a glider in the areas of operation listed in §61.107(b)(6) of this part; and

  (ii) 3 training flights with an authorized instructor in a glider in preparation for the practical test that must have been performed within the preceding 2 calendar months from the month of the test.

His last option, as posted by Crossroads, would be to fly an Ultralight aircraft.

The FAA states in Part 103...

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

  an ultralight vehicle is a vehicle that:

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

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

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

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

  (e) If powered:

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

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

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

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

Here are some overly-simplified examples in a nutshell of what you can do if you have a pilot certificate, appropriate ratings and currency of flight.

King Air 100 - you need to have a valid FAA medical.
Cessna 172 - you need to have passed an FAA medical in the last 14 years and have a note from your doctor.
SportCruiser - you need to be legally able to drive a car.
Glider or balloon - no medical needed, just a pilot certificate.
Ultralight - not even a pilot certificate needed.


What is the function of the leading edge strip? I understand the function of every wing part labelled above except the leading edge strip,what is its use in a fabric wing and will the wing function normally without it,if removed?

A wing's leading edge is a place where you really want to have a particular shape and a nice, smooth surface.  Stretched coverings (I've done this a fair amount with monokote and other heat-shrink coatings on model airplanes) suffer in this regard since, between ribs, the covering will bend inward and alter the shape of the leading edge (and, locally, the chord of the wing).  Also, since the covering is all one piece, the shape of the leading edge will also influence the shape of the rest airfoil as you go aft along the chord line.  Maintaining the shape that you actually want is really important (unless you want to make tubercule wings: https://secretofflight.wordpress.com/leading-edge-tubercles-2/) as that is the basis of your aircraft's performance and its ability to fly.  Having a solid leading edge strip does just this, ensuring that the leading edge of the wing has the desired shape and forms a smooth surface for the covering.

For a physical description of this, what we did (on model aircraft) to facilitate this was to take a very thin piece of balsa wood, maybe 1/32" thick, and gently bend it around the leading edge of our ribs.  As such, this sheet, which ran the length of the wing, would conform to the shape of the leading edge.  A picture of this from a wing I built is below (the leading edge is on the left hand side -- and just ignore the fact that the wing is twisted...).  We added some sheeting to the trailing edge of the wing for similar reasons (and to make it easier to cover).

The year prior to this, someone took a dowel and ran it the length of the wing at the leading edge instead of covering it with a sheet of balsa -- a little less effective at shaping the airfoil behind the leading edge, but much easier to implement.  However, a similar idea appears to have been implemented in the DH-60 Gipsy Moth.

In addition to aerodynamic shaping, the further you can extend a contiguous structure in the chordwise direction, the stronger your wing will be in torsion (generally speaking) -- this is a significant function of a "stressed skin" coating like you are talking about.  However, the addition of a structural element, such as a leading edge cap, that goes the length of the wing adds a non-negligible amount of torsional stiffness to the wing.

This part is more conjecture, but the leading edge of the wing will also receive a lot of wear, be it from FOD, bugs, or cleaning off bugs.  When I flew sailplanes, the leading edge of our wings would constantly be filled with bug carcasses and we'd be cleaning them off frequently.  To this end, I'd think that having a solid leading edge would be an easy way to preventing damage during the cleaning process.  However, sailplane pilots care about that more than powered aircraft, I think, so, unless you're looking at an old Schweizer 2-22 wing, this probably isn't too much of a concern.


What are the pros and cons of buying a kit aircraft vs. a factory-built one? I am a student pilot, and I am trying to decide on what I should do for a plane. I am leaning towards buying a kit, but what are the advantages or disadvantages for that?

The objective is very important.  You don't build an airplane because you want one faster or cheaper.  Neither is the case.  The kit won't be cheaper, and it'll take 1 to 2 thousand manhours, minimum, of your time (take the building time claim of any kit and double or triple it to get reality).
You build one for the experience of building one.  A lot of people who build aircraft go on to build another for that reason (the guy that built the homebuilt I own built two more after mine).
If money's an issue, the most cost effective and efficient way to keep flying after your training is to find one or two partners and buy the nicest creampuff Cessna 150 or similar aircraft you can find (really nice 150s go for around 30k).  With the fixed costs split 2 or 3 ways the expenses don't become painful (if you have to start making financial sacrifices, it takes away the fun - been there done that) and it'll be easy to sell when you want to get something bigger.
If you're mechanically handy and want to maintain an a/c yourself, buy a used homebuilt or LSA.   Only look at a kit because you want to experience the building of the kit.


What are the advantages and disadvantages of have the wing positioned further aft on an airplane? I've noticed that there is some variation in the location of the wing on airliners: The Boeing 737 has its wing mounted near the midpoint of the fuselage:

while other aircraft like the CRJ or the Airbus concept plane shown below have the wing mounted further aft.

What are the advantages or disadvantages to these wing locations, and why might a designer pick one over the other.

The overall centre of lift must be coincident (in the horizontal plane) with the centre of gravity, otherwise the plane would tip over forward or backward.

Since most planes have a large wing that contributes most of the lift and a small horizontal stabilizer that only contributes a little bit, the main wing needs to be close to the centre of gravity. So the wing is mounted further aft if the centre of gravity is further aft.

Now the cargo will always have its centre of gravity near the centre of the fuselage. So if the empty aircraft has aft centre of gravity, loading it will cause larger change of the CG position and for this it needs larger horizontal stabilizer so it can provide enough balancing force.


How might one obtain aircraft registration numbers for past flights (months ago)? I am trying to obtain tail numbers for some flights to retrospectively complete my 5 month old's new passenger flight log book. Antonakis, FlightRadar24 and FlightAware sites are not giving me the answers since the flights took place too long ago.

This is the flight information that I have:

Flight No.    Date          Route

AC 8036       29/10/2015    YYZ-PIT
AC 8037       02/11/2015    PIT-YYZ
AC 7508       05/12/2015    YTZ-YUL
AC 7521       12/12/2015    YUL-YTZ

Any help or instructions on where to obtain info would be greatly appreciated.

Note that this question is not a duplicate. This question is not answered by the question, How to determine the aircraft tail number on a particular flight?, since these flights occured too long ago to be found through the methods discussed in the answers to that question.

If you come up blank on the various open sources that have been suggested, which wouldn't surprise me, your best bet may be a personal letter to Air Canada and another as well to whatever headquarters address you can find for Jazz, explaining what you are attempting to do, and asking if they'd be willing to look up the aircraft ID for those flights for you.

For the right person, it's probably about 2 minutes of work total to look them up, although getting the request TO that person may take considerably longer.  Many airlines have customer relations departments whose job it is to address whatever issues people write in about, and a pleasant "we flew with you, flight was great, love you guys, silly us, forgot to get the tail #, baby's logbook, dedicated customers, please help, really love you guys, thanks millions..." letter may well get pointed to the right department and get you an answer.

You could also try calling and/or e-mailing; you're actually NOT looking for the standard front-line Reservations agent or "let me help you with your flight" type of person, but rather somebody in the Dispatch or Maintenance records section, as those are the people who have the big database of everything that the airline has ever done.  That said, it may be difficult to get past the usual barriers that airlines have in place to keep worried passengers in an airport from trying to talk to dispatchers about "why isn't my flight here yet???"  So I'd expect that the pleasant letter to a Customer Relations department may be your best bet.


Why did Boeing keep using yokes while Airbus moved on to sidestick? The first Airbus had yokes but they changed to the sidesticks after a while But Boeing is still stuck with yokes even with 777-300ER decades later.

The sole purpose of the yokes are seemingly for the Cessna students to stick their charts and for some instructions on the airliners which I think isnt worth blocking the screenes.

One more thing. Is it true that its impossible to manual reversion an sidestick aircraft?

Why though? Boeing simply wants to keep R&D low or there are some other reasons? They are known for using the same design to keep costs down but didn't they ever tried to innovate the mechanics?

Perhaps just another example of design philosophy between the west and the east?

There are very good reasons to implement coupled column/yokes for aeroplane control: they are right in front of you, you can apply force with both hands, and you can feel immediately what input the other crew member is giving. The force sensors in our hands are very precise feedback instruments that should and can be fully utilised.

The upside of the side stick for passenger aircraft is...actually, what was the problem that needed to be solved? More room for the lunch table?

The F16 used side sticks because of the 9g accelerations that accelerate arms all over the place and can be the source of Pilot Induced Oscillations - best to support the arm with the armrest and control the aircraft by wrist movement. Not a lot of movement because the sticks are almost fixed, and use the force sensors in the hands for pilot feedback.

Column/yoke combinations provide the clearest feedback on what the condition of the aeroplane is: hydraulics ON, autopilot ON, trim position. The 737 is about the largest plane that can handle manual reversion, and one requires a column/yoke or a centre stick for that.


Are modern aircraft (fully loaded and fueled) able to operate from hot and high airports? Some decades ago, aircraft had really difficulties to take off and land at high altitude airports in hot weather.

I'm not sure whether advanced FADEC and better mastering of aerodynamics might today allow a heavily loaded and fully fueled FedEx MD11 to take off from 5000+ feet elevation airport in hot weather.

I'm curious to know about how much progress there was over the last 20 years or so.

1. Thrust / FADEC
FADEC does not increase the thrust of jet engines. If anything it limits the thrust; the MD-11 has an emergency power overboost bar that disables the FADEC protections.
(YouTube) Instructor holding the aforementioned bar.

Whereas in crisis (for example, imminent terrain contact), a non-FADEC engine can produce significantly more than its rated thrust, a FADEC engine will always operate within its limits.
— Wikipedia

2. Lift
Aerodynamic advances sure help. But they can't make the air denser. Hot and high conditions still limit aircraft performance.
3. Tires
Tires are better now, but even with an extremely long runway, they can't withstand the speed needed to lift off fully fueled and loaded from a hot and high airport. (Higher speed is needed because of the thinner air and high takeoff weight.)
4. Number of engines
The more engines you have, the better performance you get, namely if an engine fails on takeoff, you'll have more power left on a quad-jet versus a twin-jet (3/4 vs. 1/2).

MD-11
In this answer, you see the MD-11F needs to stop for fuel mid-journey because it takes off from a hot and high airport.

The answer to the main question is no—the tires would burst at the required high takeoff roll speed given an adequate runway length and zero (hypothetical) climb limitations.

Boeing 787 (21 years later)
In this other answer, you see a not particularly high airport, but hot, limits the amount of passengers on the 787 headed from Vegas to Europe.

The first linked answer examines the physics behind hot and high, and the 787 answer examines a real life scenario with real numbers.