What exactly does "Commander" mean? Synonym of First Officer? I know that in the navies of the Commonwealth and US, three full stripes (like those worn by FOs) denote Commander, 4 Captain. "Because Pan Am operated flying boats, the company decided to step away from the WWI military pilot look and dress its line pilots in an outfit closely resembling naval officer uniforms."
Why exactly does Cathay Pacific call their Relief Pilots Commanders? Do any other airlines do this? Does Commander merely synonymize Senior First Officer?

From there you will move on to become a Junior First Officer, First Officer, Senior First Officer (Relief commander) and then onto becoming a Captain.

A Day in the Life of a 747 Pilot - Cargo Clan

Two crew – one of whom must be a relief commander or another Captain – occupy the flying seats while other crew rest, usually splitting the rest period equally.

I screenshot some CX pilots' Linkedin profiles. Nick Papas.

Richard Stroud

Justin Wills.

Frankie Wong.

You can hear "Relief Commander" blazoned at 5:35, but Capt. Anthony Peterso?e?n's voice is too muffled. The first Relief Commander is Thomas TaTower? Second Relief CDR is Steve ZaHower?

I know nothing about Cathay Pacific ranks/titles, but the plain words seem pretty logical.
The Captain, as Pilot In Command, is legally responsible for the entire flight. But who is actually in command while the Captain is required to be resting on long flights?
You don’t want the two most senior pilots resting at the same time; it would be unsafe to put a junior pilot in command for half the flight. So, you designate the second most senior pilot, who is still technically a First Officer, to be in command while the Captain is resting.


What does dashed blue lines overlay with thick faded blue lines mean in an aeronautical-chart? By looking at the dashed blue lines overlay with thick faded blue lines, can we say these are Class D airspace and Class E airspace above 1200' AGL?

Overall: Turkey system may be specific

Turkey is not integrated in the Single European Sky. The harmonization and simplification of airspace classification going on in many European countries is not applicable to Turkey, so we are in a kind of specific case which requires more research effort to understand it. See this Eurocontrol report.

From the documentation I happen to read, the Turkish airspace system is seemingly as efficient as another and, for instance, is more efficient in releasing military areas (SUA) to civil use when possible.

I wasn't able to find any description. If you can register to the Turkey AIP, you should have access to the relevant data.

Additional information from ICAO GIS Viewer

The same area than the one in the question in the ICAO viewer. I have selected different layers (a bit of learning would be needed to understand all of them), and highlighted data for three areas:

I selected only the lower space, else the viewer display is really cluttered because the developers haven't done a great job in managing label locations. The areas are:

Yellow: ANKARA ACC SCTR 8 LOWER. GND to FL325.
Blue:  ESENBOGA CTLZ. SFC to 4,500 AMSL
Green: AKINCI CTLZ. SFC to 12,000 AMSL

You can click on an area and a list of descriptions is displayed. You can browse this list with the arrows on the popup title bar (multiple areas may be relevant for the point you clicked). For AKINCI CTLZ:

Which class of airspace are they? Which rules are associated with them? I've really no idea and the legend in the viewer doesn't help:

Special use airspace (SUA)

I think it's still reasonable to interpret for non-professional purposes the area names this way (LT being the ICAO prefix for Turkey):

LTD: Danger (e.g. LDT-20)
LTR: Restricted or Regulated (e.g. LTR-30)
LTP: Prohibited (e.g. LTP-0097)
LTM: Military (e.g. LTM-LTANKZ1).

So these are SUA.

Documents that may be interesting

ATC Prosedür ve Operasyonları Kılavuzu from IVAO Turkey.

Get additional help

You may also want to look at PPRuNE which is a discussion board for pilots. You'll find pilots flying in/to Turkey, and they may provide you more information.


Where can I listen to the actual cockpit voice recorder audio from US Airways Flight 1549? I have searched for the audio recorded on the CVR from the US Airways Flight 1549, but all clips and audios I found seems to be audio recorded from the flight control and not from microphones inside the cockpit.

For example:

In this clip, we only hear the pilot sparsely, but the air traffic control and the airport tower controls quite often. Although, we can also see a transcript of what is said in the cockpit, so there obviously exists some recordings from the cockpit.

Where can I listen to the audio recorded from the cockpit and not from the air traffic control?

You can't, because it is in fact forbidden to release CVR audio under US law. From the NTSB:

  The CVR recordings are treated differently than the other factual information obtained in an accident investigation. Due to the highly sensitive nature of the verbal communications inside the cockpit, Congress has required that the Safety Board not release any part of a CVR audio recording.

Other countries may have different rules.

This rule came about after the crash of Delta Air Lines flight 1141, (commented by @MichaelK)

  [...] where the crew — in extremely cruel irony — were bantering on the flight deck about what to say that would get captured on the CVR in case of a crash. That irony was then squared in that the bantering was a directly contributing cause of the crash, in that they forgot to deploy flaps and slats


Does the FlightRadar24 pose a risk to aviation security? As you may know, on the internet there is the FlightRadar24 website where you can see the flight information of planes worldwide in real time. Although this is wonderful for those who like aviation, does this type of system not pose any risk to aircraft safety? For example, terrorists may well plan an attack on a specific plane by knowing its information.

The data FlightRadar uses is provided by volunteers using commercially available ADS-B receivers. All it does is save the terrorist a couple of bucks buying an ADS-B receiver.


When to disconnect the A/P on approach in an airliner? I've looked at the other question asking about when to disconnect the AP on an airliner and I get that it's very situational depending on the pilot and conditions.

I've found I'm too reliant on the autopilot for an auto land in my PC flight simulator. I've been trying to practise manual landings but I'm suffering badly from when I do manage to stay on course with the runway of doing 600-900 fpm landings or floating way too long and I know this isn't down to getting my flare right.

Are there any tricks to improve my landings? I've been trying to start disconnecting the autopilot once I'm on the glide at around 2000ft but I'm finding I'm ending up not lined up with the runway. The only way I usually land well is if I disconnect at around 200ft and even then I usually land hard.

Is it common for pilots to fly in manually the full glide or is it a lot more common the only fly the last few hundred feet manually?

You are experiencing what real world pilots also experiences as they level up: unable to keep up with the plane.

You are unable to keep up with the plane because your mind is behind the plane. You are doing what you'd do if you're flying a Cessna: you react after you see. In a jet, things happen very fast. A large aircraft, like a B737, is also heavy and the controls are not as responsive. That is why it became impossible to you.

To fly high-performance aircraft, your mind has to stay ahead of the plane. Anticipate what will happen. Do not react to what is happening. If you only react to something that has happened while flying a jet, you're already too late.

Technique-wise, you should focus more on the attitude indicator (AI). The AI is the only instrument which tells you the future. Altitude tells you the present, and the vertical speed indicator tells you the past. These instruments let you verify if 2 seconds ago you did correctly. To predict what the plane is going to do in the next second, you need the attitude indicator. Say the plane is now pitched zero degrees, and it is descending too fast. First, make up your mind about the new pitch angle, say 2 degrees up. Then, look at the attitude indicator and adjust pitch to 2 degrees up. Only after that, you give the VSI a quick scan to verify your descend rate is indeed reduced. Do not adjust pitch by looking at the VSI. It will never work.

You may also be too ambitious by attempting to fly airliners in the sim before you have a solid piloting skill. Move up progressively. Fly on small planes first. Practice maneuvers, like steep turns. As your skill improves, slowly move up to faster and larger aircraft.


What is the purpose of a retracting cowl? I flew yesterday in a SWA Boeing 737-300(?) in the seat next to the engine. Right after touchdown, I noticed that part of the cowl retracted back significantly (a few feet or so it seemed), exposing the engine body. The cowl closed back when the speed dropped to taxi levels.

What is this cowl retraction for? Is it part of the aerobraking?

You have seen one type of the possible thrust reversal systems in action. In the following image is the bottom one.

Image source

They deploy surfaces that deflect the bypass air and aid the brakes in slowing down the aircraft after touchdown.


How long does AFSP processing take the second time? If you've already completed the fingerprinting for the TSA's Alien Flight Student Program and been approved to train at one flight school, how long does it take to gain approval to fly at another flight school?

Assuming that you're a category 3 applicant, you can start training as soon as they confirm receipt of your completed application but there's no specific processing time. This is from the AFSP FAQ (direct links to FAQ items don't work):

  Category 3 Candidates may commence training after receiving the "Permission to Initiate Training/Fingerprint Receipt" e-mail, which AFSP issues upon receiving all required information (including fingerprints and the fee).

There is a guaranteed processing time for categories 1 and 2 (aircraft greater than 12,500lbs MTOW), however:

  In accordance with Section 612 of Vision 100 and the IFR, the AFSP conducts a threat assessment on Category 1 Candidates within 30 calendar days of receiving all of the required information, including fingerprints and the fee. The AFSP conducts a threat assessment on Category 2 Candidates within 5 business days of receiving all of the required information, including fingerprints and the fee.


Why Airbus A220 if A320 already exists? Airbus just presented its new A220 aircraft, formerly the "old" Bombardier CSeries, that is re-branded after a 50.01% acquistion of Bombardier by Airbus.

It's an aircraft very similar in target and characteristics to its own A320neo Family, so my question is simple... why? If they would cover different market segments this could be a logical choice but in this case, is there not the risk of creating internal competition?

The A320-318/319 or the improved A320neo-319 share the market area around 107 - 160 passengers with the CSeries (now A220), two main differences are:

The CSeries is designed generally for carrying less passengers than the basic A320-family. The fuselage of the A320-family is stretchted or compressed, exemption is the A320-318, which has also smaller wings, but at some point strechting/compressing the fuselage becomes inefficient.
The CSeries is an entirley new plane, while the A320neo seems to be more some kind of improvment with new engines and some(?) modifications to the airframe.

Basically, the airframe, fuselage and engines should fit together, to make an efficient plane. The CSeries should be therefore more efficient with small numbers of passengers. The A320-318 will be not available as neo and the A320neo-319 seems to be market for special long-distance and hot-and-high (engines produce more thrust and consume more fuel) situations.


Turbofan engine start - Why does ignition occur so early? In another thread, two key steps of starting a turbofan (ignition and fuel introduction) are given as follows:

  With increased N2 rotation, ignition will be turned on. [...]
  With further increase in N2 rotation, fuel flow will be introduced.

For some engines I saw that ignition is typically turned on at about 15% rotation, and fuel is introduced at about 30%.

I understand that the value for fuel introduction (therefore light off) is given by the need to further power the engine as early as possible, but not too early or the system will be disrupted. However I don't understand why there is a precise moment for ignition. My questions are:

Between 15% and 30% rotation, ignition will be on without any fuel. Why doesn't ignition instead occur just before fuel introduction?
Conversely, why wouldn't ignition occur earlier? Is there a physical requirement of the compressor turning at a certain speed before ignition can be on?

Thank you for your answers.

Traditionally the fuel is introduced by the pilot at a specified minimum RPM, but this is a function controlled by the pilot-eye-hand brain interface (only on the newer pushbutton start FADEC engines is this function fully automated) and we all know how imperfect this interface is.

With a traditional system, you need to allow some fudge factor in case the pilot adds fuel early, and also if there are system faults it gives a bit of time for the fault to be detected and displayed. So most start systems start the igniters running as soon as the starter is on (in the pre-FADEC days it wasn't too hard to ruin an engine, which is why captains traditionally handle starting).

The RPM at which fuel is to be turned on is actually bit sooner than really necessary, to let the engine help the starter bring it up to self-sustaining RPM.  The minimum RPM is there because you need a minimum mass flow going to the burner can to control the flame and therefore the temperatures (these engines are "air cooled" after all and the majority of the mass flow is not actually being burned, but being used to contain the flame boundaries - some flame does make it back toward the turbine during start, as you see when the ITT spikes, but it has to be minimized, and the more mass flow the better).

You can delay introducing fuel well past the minimum RPM, and you will actually see a lower ITT peak on a non-FADEC engine by doing so (because, as I said above, more mass flow provides more flame control), but this really adds to wear and tear on the starter.

When I was in the Regional Airline business supporting CRJs we observed that a lot of captains made it a practice to delay fuel introduction quite late (like waiting to 25-30% instead of 20% for the GE CF-34) because they noticed that the ITT peak was lower when fuel was delayed.  However this had to be balanced against shorter starter life and we advised against getting carried away with this because the marginally lower starting ITT peak didn't appear to actually improve engine life, while shortening starter life significantly.

On the other hand, it's important to know that it isn't essential to get the fuel on right now when the RPM is at the fuel introduction value and you can do it at a relaxed pace. If the nominal value is 20%, putting fuel on at 23 or 25% does no harm, so take it easy (pilots in training (including me) would fumble with the thrust lever lockout thinking they had to get the fuel on exactly at the right time).


What were four objects seen in Flightradar24 over Germany with the callsign TWR? In Flightradar24 from 290030Z and then for two more hours, there were 4 identical objects over Germany between EDFM and EDDS at altitudes from 600 to 1900 feet, a few knots speed and each changing course more than two times per minute but no trace like if stationary. The distance between the objects was about 20km. They all have the same callsign: "TWR". What are they?

Many towers in Germany are equipped with FLARM so that they are electronically visible to FLARM equipped aircraft in the area. This is especially useful for helicopter emergency medical services and law enforcement that operate in urban areas during marginal weather conditions.
The fact that the towers are not always visible on FR24 may have to do with the fact that not all their receivers are equipped with FLARM. If nobody nearby is providing FLARM data to FR24, the towers are not visible on FR24.
The speed shown has to do with the GPS receiver in the FLARM unit; they sometimes detect small speeds, even though the receiver is stationary.


Are these pressure and velocity distributions calculated by CFD simulation correct? I am simulating wind tunnel tests for a NACA64210 airfoil with the following conditions:

$P_\infty=101300$ $Pa$ ; $\rho = 1.23$ $kg/m^3$ ; $U_\infty = 29.99$ $m/s$

I performed the simulation with Solidworks Flow Simulation, and I obtained the following plots.

My question is about if these plots make sense and can be correct.

For instance, I am wondering why in the velocity plot, the velocity is not zero at the leading edge (provided it should be a stagnation point), maybe it's because the wind tunnel speed is low.

On the other hand, as far as I know, the pressure distribution in a wing should be smaller in the upper side of the wing than in the lower to successfully create lift, in this case it seems to be equal at both surfaces. Also, there's usually a suction closer to the leading edge that I cannot detect here.

I just need a review of my plots to know if they are correct or not, and if they are not correct what might be the cause of it.

P.S: The only setting that I was not sure about what to input, was that I enabled that the air was laminar and turbulent. I'm not sure if I should have stated only laminar, instead.

Qualitatively they seem to be correct:

Highest pressure at stagnation point and maximal pressure in diagram close to total pressure:
$$101843.84\ Pa \approx P_{tot}= P_{\infty}+\frac{\rho}{2}\cdot U_\infty^2 =101853\ Pa$$
Speed drop at stagnation point.
The slight flow deflection downwards behind the airfoil shows that your airfoil is generating lift (I am assuming your free stream flow is in x-direction).
Low pressure (dark blue) region above airfoil is bigger than below.

As @ROIMaison wrote the correct way to validate the results is looking at the aerodynamic coefficients and pressure ditribution $c_p$. In a quick search I found some polars calculated with xfoil you should be able to replicate. With xfoil you can calculate the pressure distribution too.

If you are only interested in lift at small angles of attack laminar flow simulation should be enough. If you also want to calculate drag I would set turbulent air. To validate your setup (model, boundary conditions,...) for turbulent flow there is a great NASA webpage.


Do the polar curves have large differences in takeoff than in landing? I was wondering if the polar curve has differences in the takeoff due to the smaller extension of the flaps (this is half that in the landing) that changes the AOA for $ C_ {la} = 0 $. In addition, should I calculate the landing polar on approach?

The $C_L(\alpha)$ curve changes with flap/slat extension, so it should logically follow that the polar will also change, since the induced drag depends on the lift.

Furthermore the parasite drag will most likely change as well due to a changing airfoil surface.

So yes, the polar needs to be recalculated for all flight configurations.


What's the difference between flight level and pressure altitude? When should we say flight level and when should we say pressure altitude?

I know they both set QNE 1013.25, but there is a difference between them.

Anyone know?

Flight Level specifically refers to Pressure Altitude in 100 foot increments within the Standard Pressure Region, which in North America starts at 18000 ft and above, and at various lower altitudes elsewhere.

If you are in the Altimeter Setting Region where you set local barometric pressure to get indicated altitude, you normally use indicated altitude and could state the pressure altitude if asked, but you wouldn't use the term Flight Level.


What is the autorotative rate of descent for a Bell 47-H? I would like to estimate the amount of time a pilot would have before a forced landing after suffering engine failure in a Bell 47-H at 1,000ft. This is for purposes of understanding a historical accident. The pilot in question ran out of fuel so the tanks were empty. Many thanks.

According to this fairly recent flight test...

  As we climbed for an autorotation Sean explained that the yellow line around the bubble effectively demarcates your autorotation options − you can land on anything under the line, you’d be pushing it beyond that. With the inertia of the -23 model blades and their nine-pound tip weights, the entry is smooth and unhurried, the descent at sixty knots bringing up about 1,700 fpm, and the flare stress-free − very different from the crash-bang-wallop engine-offs of the low-inertia world.

Around 1700 feet per minute in auto. The Bell 47 is known to be one of the most forgiving helicopters to autorotate, thanks to the large blades with weights on the tips... what is known as a 'high inertia' rotor system. The opposite is a 'low inertia' rotor system such as the Robinson series, which requires less power in flight, but the lighter blades don't retain nearly as much inertia in an auto, giving one less latent energy to use during the final flare, and a more slender margin of error.

On my daily commute, I used to admire a Bell 47 I'd see out doing traffic reporting duties. An article popped up in the local paper on how that particular 47 lost engine power at 2000 feet... it was fresh out of an overhaul. The 47 was landed with only a ding on one skid... no report on the damage done by the pilot to the mechanic who overhauled the engine, but I suspect it may have been more than a bent skid.


What is the most simple plane lift equation that gives realistic solutions? I need the most simple lift equation that once solved with Mathcad gives a realistic vertical speed of a plane and implicitly the altitude h(t).

Also the drag eq. (1) leads to a good solution, a Vh(t) that increases and finally reaches a limit (the maximum horizontal speed) and stays there during the duration of the flight, the lift eq. (2) stabilizes at a Lift(t) - m * g = ct. > 0 and in consequence Vh(t) keeps growing indefinitely because an eq. of the type m * dVv(t)/dt = ct. leads to a solution Vv(t) that rises linearly with time.

Question:
It is quite clear that the vertical speed of a plane, Vh(t), can not grow indefinitely. How can I stabilize it to o constant value. What do I have to add in the lift eq.?

Drag eq.: m * dVh(t)/dt = T - Drag(t) (1),

Drag(t) = 0.5 * Cd * r * S * ( Vh(t) + Vw(t) )^2,

Lift eq.: m * dVv(t)/dt = Lift(t) - m * g (2),

Lift(t) = 0.5 * Cl * r * S * ( Vh(t) + Vw(t) )^2,

where:

Vh(t) = horizontal speed, Vv(t) = vertical speed, both of them have to be determined being unknown functions.
known parameters: m = the mass of the plane, r =  air density, S = the wing surface, T = thrust = ct., Cd, Cl are the drag and lift coefficients, g = 9.81 m/s^2, Vw(t) = the wind speed, that is usually a known constant but can have other forms given as functions of time, t.

First, you need to add the effect of density $\rho$: Air density changes with altitude, and this affects both lift and drag (at least if you model airbreathing engines).

For lift $L$, use $$L = c_L\cdot\rho\cdot\frac{v_h^2+v_v^2}{2}\cdot S$$

For drag $D$, you should only simplify the equation as much as possible. Your equation is simpler still and doesn't model the increase in drag with more lift. The simplest practical equation will look like this: $$D = \left(c_{D0} + \frac{c_L^2}{\pi\cdot AR\cdot\epsilon}\right)\cdot\rho\cdot\frac{v_h^2+v_v^2}{2}\cdot S$$

More lift will need more thrust and will limit the upward acceleration. Climbing higher will reduce thrust in proportion with density and limit the possible speed range.

Nomenclature:
    $c_L \:\:\:$ lift coefficient (normally between 0 and 1.5)
    $\pi \:\:\:\:\:$  3.14159$\dots$
    $AR \:\:$  aspect ratio of the wing (ratio of span to mean chord)
    $\epsilon \:\:\:\:\:$  the wing's Oswald factor (use 0.8 when in doubt)
    $c_{D0} \:$  zero-lift drag coefficient (use 0.02 when in doubt)


Is ATIS information - including identifier - available on the internet? According to Section 2-9-1-a of the FAA's Air Traffic Organization Policy, a phonetic letter is assigned to each tower-issued ATIS update.

This information is available on the ATIS VHF frequency for an airport, or via a phone call to a designated ATIS number for the airport.

There is a passing reference on the Wikipedia page to ATIS being available electronically via a service named "D-ATIS", although I've never heard of this.

I'd love to be able to view this information electronically, rather than having to get my VHF handheld, or the plane's radio going and tune it in before flight. The voice system is frequently engaged. If it was available via the internet, it'd be super-easy to access.

Is there a means accessing the ATIS - including the identifier - for a given airport in electronic form via the internet? If so, how?

NOTE: I know it's possible to get METAR reports, but they are typically automatically generated, not manually adjusted by the tower (as ATIS sometimes is), and don't include the phonetic letter designation issued by the tower and required for initial tower contact.

The short and general answer is: No.

The ATIS is only a VHF recording, but even when recorded digitally, it is not available in a text-base form in many cases which would allow being made public on the internet. In the case of D-ATIS, the information can only be obtained using ACARS, other systems such as CPDLC require special equipment.

With modern technology and communication, some airports have started to use Twitter to broadcast ATIS, however they should not be used for flight purposes, but are only for entertainment.

(Image Source: Twitter - Account: @yssyatis)


Are the A320's A and B electrical buses both energized all of the time during flight? I'm a novice reading a quick study guide.

For electric power, I notice that the A320 has two buses: A and B.

Are they both energized all of the time during flight? If not, is there a way to switch between buses?

The power diagram with the two buses looks similar to the Apollo Command Module and maybe the Service Module.  I wonder if it was a borrowed idea.

They are both energised all of the time except emergency situations. The essential devices can be switched between them, the non-essential ones will be turned off in such cases.

There is actually a couple more buses than two. The main ones, AC BUS 1 and 2¹, are powered by one engine-driven generator each, and are normally not connected. This has some advantages that

the generators don't have to be synchronized, and
if there is a short-circuit on one, the other remains functional.

The APU generator and external power are connected to a bar that can be connected to either and automatically connects to whichever is not powered. This bar can also be used for connecting the buses in case only one generator is running, and this can be controlled by a switch.

The essential devices, which means most cockpit instruments, are connected to a separate Essential AC BUS, which is normally connected to the AC BUS 1, but can be, manually, switched to AC BUS 2, in case AC BUS 1 does not work. It can also be powered by emergency generator (on RAT) or even an inverter from the batteries when RAT does not work (before it deploys and after landing during roll-out).

The even more important devices, including the flight control computers, are connected to the DC HOT BUSes directly powered by batteries.

So the essential devices can be switched when either bus is not energized. The non-essential devices like galleys, in-flight entertainment and cabin lights, will be powered off in that case. They will also be disconnected if the bus is energised, but does not have enough power (automatic load shedding).

¹ In the document I have they are not called A and B. The document document is (I got it off the internet², so it's not official copy for legal purposes) titled A318/A319/A320/A321 Flight deck and systems briefing for pilots and apparently created by Airbus (in 2007, but it's unlikely they changed this since)

² This or this is a slightly different version (even older, dated 1998), but the chapter 3. Electrical System has the same content. The included image is from the later link.


Is there less vertical space for an engine under the wing of a 737 Max than for an A320neo? The source of this question is the understanding that the LEAP-1B couldn't fit under the wing of a 737 without changing its longitudinal position. But this wasn't the case with the design of the LEAP-1A/A320neo. For lack of ground clearance?

What is the height under the wing of a B737 Max at the point where the engine is attached? Under the wing of an A320neo?

Regarding question duplicity: This is about wing ground clearance, not engine ground clearance.

The short answer is:

Yes, there is less vertical space under the wing of a 737 Max compared to an A320neo.

In the image below I have put the two airplanes side to side and the height difference is very apparent. Please note that the images are from the respective predecessors of the aircraft. The only thing that has changed regarding the height is that the 737 MAX has slightly larger tires than the 737 Classics, which should raise the MAX by 2 inches.

The reason for the lower height of the 737 is that it was developed a lot earlier when engines were a lot smaller in diameter. Therefore, they designed shorter landing gear. Choosing longer landing gear would have seemed unreasonable because this comes with a significant weight penalty. Redesigning the landing gear now would basically mean designing a completely new aircraft, because it would interfere with so many other systems.

Image Source A320, Image Source 737

It is difficult to accurately compare distances in photographs, because they come with all kinds of distortions. I have resized the images so that the main gear track is according to scale. Therefore the height comparison of the wings is fairly accurate.


How frequently are airplane windows cleaned? When you’re driving on the highway, after sometime unwanted insects and dirt accumulate on your windshield. When you stop over at a gas station, you might clean it off. It’s likely the case for aircraft as well, especially during takeoff and landing. But how frequently are airplane windshields cleaned? And how are they cleaned? Does this include cleaning of passenger windows?

I clean them whenever they are dirty to the point of affecting ability to see traffic or cause distractions.

Bugs, dust, and dirt can make it very difficult to spot traffic, birds, and obstructions, especially in hazy weather.

It is the pilot’s responsibility to “see and avoid” and clean windows play a large role in this critical safety area.

Depending on how bad contaminants are (i.e., if it’s bug season) the interval for cleaning could be as often as every flight or as little as once every few days while continuous flight operations are in effect.

Windows are cleaned with either water or special chemicals for cleaning plexiglass with microfiber or non-abrasive cloths. Also of note, human fingerprints are ideal for cleaning aircraft windows with water as they are soft and do not scratch, but the ridges pick up the dirt and easily rub off even sticky contaminants [bugs]. Aircraft windows are relatively soft and scratch very easily. All cleaning motions are done in the direction of the airflow to prevent hazing of the window from scratches... no circular scrubbing - only in the direction of air flow. Passenger windows rarely get dirty. It’s the ones for the cockpit that are directly exposed to the frontal airflow that get the worst of it.

I usually use water, my fingerprints for scrubbing, and clean microfiber cloths for drying to prevent water spots - which can obscure vision as bad as dirt.

Here is a video of the process.


Is there any non-experimental way to obtain CL, CD, and CM as a function of the angle of attack and the control surface deflection angle? I am working on a flight simulator for control algorithm testing. The issue I am facing is to come up with a relationship between CL/CD/CM and the angle of attack ($\alpha$) and the control surface deflection angle ($\delta$).

Since I'm developing a control algorithm for a flying wing, it is crucial to know how not only $\alpha$ but also $\delta$ affect the forces and moments on my flight vehicle. And I cannot afford to measure the forces and moments experimentally.

In the Gazebo simulator, the LiftDragPlugin's approach is to assume that the lift curve shifts up and down by $\delta$ times some constant. However, that is not the case, as can be seen from the numerical results from XFLR5 below.

Where “Plane Name $\pm\delta$” describes the curve for any $\delta$.

We can see that the curve shifts in both direction from zero-$\delta$ position. For instance, the stall angle decreases as $\delta$ increases.

My current approach is to construct a three-dimensional lookup table by using the curves at $-\delta$ and $+\delta$ as endpoints and linearly interpolate the two curves along the z-axis. When I need the aerodynamic parameter (CL, CD, or CM) at some $\alpha_0$ and $\delta_0$, I can just locate the point in this three-dimensional space from $\alpha_0$ and $\delta_0$.

Is this a valid way to determine CL/CD/CM as a function of $\alpha$ and $\delta$ numerically? If not, how should I approach this problem?

The graphs in the OP show fairly typical results that one would expect from linear analyses (e.g. VLM).

1. Lift

In the linear range, the lifting surface's lift coefficient ($C_L$) can be expressed as:

$$C_L = a_0 \alpha + a_1 \delta$$

where $a_0=\frac{\partial{C_L}}{\partial{\alpha}}$ is the lift curve slope and $a_1=\frac{\partial{C_L}}{\partial{\delta}}$ is the lift slope per plain-flap deflection, which are constants in the linear range and can be readily seen in your lift plot.

Conclusion: You can simplify your lookup tables to the above equations (all constants) if you are only interested in capturing the linear effect (which is all that VLM can capture anyway).

2. Pitching moment

In the linear range, you can express the pitching moment coefficient ($C_m$), which I assume is computed at quarter chord, as:

$$C_{m} = C_{m_{ac}}(\delta) + C_L\frac{l_{ac}(\delta)}{\overline{c}}$$

where $C_{m_{ac}}$ is the pitching moment at the surface's aerodynamic centre (AC) and is a function of $\delta$; $l_{ac}$ is the distance between the 1/4c and AC and is also a function of $\delta$; $\overline{c}$ is the reference chord length.

The $C_m$ plots you've shown seems to line up very close to the aerodynamic centre of the lifting surface (by the fact that there is very little change in  $C_m$ with respect to AOA). Flap deflection only significantly changes the offset ($C_{m_{ac}}$). The variations in the slopes are because you do not have a full span plain-flap (you have elevons which are partial span), which changes the spanwise lift distribution and the resulting aerodynamic centre.

Conclusion: You can replace your multi-dimensional lookup table to two 1-dim tables for $C_{m_{ac}}$ and $l_{ac}$, and supplant with the above equation. You may even replace these lookup tables with constant linear relationships if your plots hold water.

3. Drag

The drag coefficient ($C_D$) is the most interesting. It seems like there is some boundary layer analysis combined with the VLM, since $C_{D_0}$ changes per flap. If the Reynolds number do not change significantly, you can attempt the following simplication:

$$C_D = C_{D_0}(\delta) + K(\delta)C_L^2$$

where C_{D_0} is the form drag and $K$ is the induced drag factor, both of which are a function of $\delta$.

Conclusion: You may again simplify your multi-dim lookup tables to two 1-dim tables.

4. Lastly...

You definitely will start to see nonlinear effects at 30 deg control deflection in real life, maybe even at 20 deg. This is obviously not captured by VLM.


Is there a difference between MEA and MOCA within 22 nm of a VOR? As we all know from our instrument training, the MOCA is:

  MINIMUM OBSTRUCTION CLEARANCE ALTITUDE (MOCA)- The lowest published altitude in effect between radio fixes on VOR airways, off-airway routes, or route segments which meets obstacle clearance requirements for the entire route segment and which assures acceptable navigational signal coverage only within 25 statute (22 nautical) miles of a VOR.

Whereas the MEA is:

  MINIMUM EN ROUTE IFR ALTITUDE (MEA)- The lowest published altitude between radio fixes which assures acceptable navigational signal coverage and meets obstacle clearance requirements between those fixes. The MEA prescribed for a Federal airway or segment thereof, area navigation low or high route, or other direct route applies to the entire width of the airway, segment, or route between the radio fixes defining the airway, segment, or route.

(Both quotes taken straight from the Pilot/Controller Glossary)

The only difference in language is the bit about 22 miles from a VOR.

Therefore, when you're within those 22 miles, there's no practical difference between a MEA and a MOCA, right?

If that's true, why is there an 1800 foot difference between the MEA and the MOCA within 22 miles of the PMM VOR on V84?

You are right. Within 22 nautical miles of the VOR, there is no practical difference between an MEA and a MOCA.

However, it should be noted that the 22 nmi is only a limitation if navigating via VOR's.

14 CFR - CHAPTER I § 91.177  Minimum altitudes for IFR operations

  (a) Operation of aircraft at minimum altitudes.
  Except when necessary for
  takeoff or landing, or unless otherwise
  authorized by the FAA, no person may
  operate an aircraft under IFR below—

  (1) The applicable minimum altitudes
  prescribed in parts 95 and 97 of this
  chapter. However, if both a MEA and a
  MOCA are prescribed for a particular
  route or route segment, a person may
  operate an aircraft below the MEA
  down to, but not below, the MOCA, provided
  the applicable navigation signals
  are available. For aircraft using VOR
  for navigation, this applies only when
  the aircraft is within 22 nautical miles
  of that VOR (based on the reasonable
  estimate by the pilot operating the aircraft
  of that distance)

The MOCA provides "obstacle clearance requirements for the entire route segment," so if the applicable navigation signal is GPS, and you're receiving it, then you've met the requirements. This is why sometimes you see a MOCA on segments which aren't within 22 nmi of any VOR.

One other practical difference to keep in mind is that, especially in mountainous areas, you're much more likely to get radar coverage, and have better communcations clarity, at the MEA than the MOCA (I saw this a lot in Idaho). In those cases, ATC is probably going to prefer the MEA.


What is this smoke coming from an F/A-18 shortly before takeoff? Watching a video of F/A-18 fighter-jets taking off, I noticed some sort of gas blowing out behind the canopy shortly before the start of the takeoff roll.

Here's a screenshot:

In some videos the smoke is more dense than in others. Has this something to do with cockpit pressurization?

It is not smoke.  It is bleed air being blown behind the heat exchanger which forces cool air across the front of the heat exchanger, this is only happens on the ground. The left side of the aircraft has a secondary heat exchanger that is also cooled by a water spray nozzle.  The water is created by the ECS taking bleed air and cooling it.  The water is blown out by the bleed air so you can see it more on one side than the other. In the picture, it seems to be raining so the air being blown out is more visible because of the rainwater.
-6287 (Fixed-Wing Aircraft Safety Equipment Mechanic, F/A-18)


What are the differences between the two main brace positions? Why are there two different brace positions (pictured below) ?
(If there is a difference between the official and true reason, please state both. In many planes the reduced seating spacing does not allow the pike position (on the right), but I doubt this is the official statement of airlines.)
Are they equally protective ? If not, why are both recommended ?
What arguments are there in favor or against each ?
If available, statistical data and relevant links to studies and crash tests would be very welcome if they distinguish between the two positions.

One is for when the seat in front of you is in the way of using the other.

The other is for when you can't reach a seat in front of you.

They won't both be relevant for the same person in a given seat. If you can assume the second position, the first one probably won't provide meaningful support for your head anyway.


When calculating takeoff performance why include airport elevation in pressure altitude? When calculating the pressure altitude for aircraft performance I learned to calculate it the following way:

Pressure Altitude = (29.92" - altimeter setting) * 1000' + elevation

So at an airport at 3000' elevation and an altimeter setting of 29.92" I can expect the aircraft performance to be that for 3000'.
I never questioned that but now I wonder why don't we just care about the altimeter setting? If the altimeter says the station pressure is 29.92" sea level, but I am at 3000', then the airplane still thinks it's at sea level when it comes to performance. Is that wrong?

Same for an airport at 3000' elevation and an altimeter setting of 28.42" I can expect the aircraft performance to be that for 4500'. Again, why not 1500'? The airplane should think that it is, regarding pressure, 1500' above sea level.

I think that would make sense for en-route performance. If the station pressure along the way is 29.92" and I fly above at 4000', my pressure altitude will be 4000' (0*1000 + 4000). If my station pressure however is lower, say 28.92" for instance, then the pressure altitude above at 4000' would be 5000' ([29.92"-28.92"]*1000 + 4000).

If the altimeter says the station pressure is 29.92" sea level, but I am at 3000', then the airplane still thinks it's at sea level when it comes to performance. Is that wrong?

Although the station pressure may be reported as 29.92", that does not mean that a barometer there will show that as the current pressure.  The reported value is the actual pressure, plus an extra amount that is calculated would occur if the recording station were lowered down to sea level.  Instead of actual pressure, you are setting the QNH pressure.

So sitting at a 3000' airport with the altimeter reading 29.92 does not mean the airplane thinks it's at sea level.  Certainly the altimeter doesn't think this, because it's reading 3000'.

You could use the actual pressure outside as an altitude-independent performance gauge, but you don't normally have that value (and ATC isn't going to radio it to you).


Triple engine failure; which would you choose to keep left? It is well known that planes with two engines must be able to land with one engine inoperable for their certification, and that four engine planes with two inoperable.

Now, suppose you had a four engine plane with 3 engines inoperable, and only one remaining. In terms of the greatest likelihood of survivability of this incident, is it at all favourable to have the engine closest to the body of the plane active, or the one further out?

As far as I can see it, there are two main ways to tackle this; one is by looking at incidents where triple engine failure occurred (which is very rare) and seeing whether it makes a difference.

The other approach is how does it affect the controllability and maneuverability of the aircraft theoretically or based on testing depending on if one has the jet engine closest to the body active, or the one further out on the wing. It may be that the difference is negligible, but I'd be curious if there can be some argument made to favour one option.

There would be other variables to take into account, so to narrow it down a little more, I am considering only jet engines, on aircrafts used for commercial flight.

Using the inner engines allows you to maneuver easier as the yaw moment is smaller in comparison to the outboard engine which also means you need less rudder inputs to keep the course. The big advantage of needing less rudder to keep a straight path of flight is that you can react better because the rudder can move a bit more.

Which sides engine to use is depending on the wind situation (I would use the engine on the side the wind is coming from as you can turn into the wind better to keep your course) and other influences like if you need to turn left or right more often; avoid turning into a dead engine as Terry already mentioned).


What simulation software do airlines use? What simulation software do airlines use for training purposes? Do they use software like P3D, FSX, X-Plane, or FlightGear? Or is it a custom? What about aircraft? Do they source them from groups like PMDG or is this also custom?

X-Plane offers a "Professional Level" which is mostly about licensing. However X-Plane also has an FAA certified version that if paired with proper controls is legal for certain training/instructional hours. You can find more info on the FAA's approved simulators here and here. The flight school I trained at had a certified sim from the 80's that was pretty miserable by todays standards. It was certified and had no screen, I would say it was "custom built" FWIW.

Many airlines may turn back to the manufacturer for recurrent training. Both Boeing and Airbus run facilities with full motion simulators. I would think they built the software in-house but I don't have any hard evidence on that. As the OEM builder they have access to genuine interior parts to build the sims.

For smaller aircraft places like SIMCOM offer training in full motion sims but do not list their software of choice. SIMCOM uses actual aircraft interiors (most likely from defunct airframes) for their sims.

If your really adventurous you can build a full cockpit sim yourself.


Why do we feel gravity on a plane? How come a plane flying at constant velocity experiences gravity?  If you were in a space capsule flying (not accelerating) you would feel weightless until you hit the ground.  Why not a plane?

This is the difference between flying and in orbit. In orbit, you are indeed falling toward the earth, but the spacecraft is too, and you're going fast enough that you keep missing the earth.

In an aircraft, because it's staying aloft due to lift, it is not falling. This is why you experience the pull of gravity on a plane.

Some aircraft are designed to feel weightlessness, see Vomit comet.


What are the circles/holes ahead of the wing of an MD-82? In the picture below I noticed there are three circles or holes of some kind ahead of the wing, what are those?

(airliners.net)

The three large circles indicated in the question are static port plates. These measure the static pressure of the surrounding air, which is used to measure airspeed and altitude.

Original Source

Thanks to a link from Jonathan Walters, here is a closeup of one:

The four smaller areas in a row along the centerline are the radar altimeter transmitters/receivers. The radar altimeter uses radio waves to determine the aircraft's altitude above the ground. This diagram for the A345 has them further aft, they're in similar configurations on other aircraft.

Original Source


What are capabilities of small Airplane in general? In general what can i expect of small, 4-seat, light airplane? I am specifically interested in the Pipistrel Panthera, though general responses would be appreciated.

What is usual range of that kind of plane?
What is the worst weather under which it can fly?
How expensive is to fly internationally with that kind of plane?
What is the procedure and usual cost for example if I fly from Rome to Prague, what border control checks can I expect? How and what kind of taxes related to that particular flight would I pay?
If a plane is declared to have range of 1900 km, what is practical range in practice?
If regular service for an airplane is declared to be after 7000 km of flight or X hours of flight, what has to be done usually in those services? Changing of oil, changing of filters?? How expensive usually is that?
Anything else you think is important to know about possessing and airplane of that type?

You have a few questions and the answers to them vary greatly based on the plane in question. It's often said you should chose the plane for your "mission" which means you should think about what you would like to do with the plane and then chose the plane that best fits that "mission". But anyway let's address some of the questions at hand.

  What is usual range of that kind of planes

This depends on the plane. Small planes can get anywhere from 500 nautical miles to upwards of 1500 nautical miles depending on fuel load and optional tank configuration. But the middle of that range seems to be the average. I have found that range is more dependent on how long you can sit in the plane not now much gas you can carry. Remember there is no bathroom on these little planes and some are not the most comfortable things in the world.

  What is the worst weather under which it's ok to fly that kind of
  airplane?

Although this is changing most small aircraft are not certified to fly in ice. Some can be modified to do so and some come with the option when you buy it. That being said I don't know if I would fly a small plane in ice but IMC is possible and done all the time. Remember also that fancy equipment does not always mean you are safer, you are still flying a tiny plane in bad weather.

Rain is possible but keep in mind rain on the ground could mean ice in the air depending on the temperature. Some small airplanes will be able to climb above this but that depends on plane.

Wind is limited by the airports you are flying to and from. If the wind is blowing down the runway you are good to go but every small plane has a maximum demonstrated crosswind component that will limit your ability to fly in high winds at some single runway airports where a crosswind landing is the only option.

  How expensive is to fly internationally with that kind of plane.

Again this changes from plane to plane and country to country. Small pipers can be flown for (from what I have read) under 10K(USD) a year and less if you don't fly very often. With older planes you will pay more in maintenance and less in up front cost while with a new plane you will pay more to buy it and less to maintain it as its fresh. You will also have to factor in gas and insurance. Insurance depends on YOU and your flying time so its hard to say what that will fall in. Gas here in the US (100LL) is around 4.56-6.00 where I am so figure in that based on fuel burn etc.

  What is the procedure and usual cost for example if I fly from Rome to Prague, how the border control checks me, how and what kind of taxes related to that particular flight do I pay. Please, don't miss anything.

I don't fly in the EU so I will refrain from commenting here.

  If a plane is declared to have range of 1900 km, what is practical
  range in practice?

Here in the US you are required to flight plan with enough fuel for your flight plus 30 minutes of reserve. I don't like when companies put range because this is very much based on the winds and your course. If you get a 40 knot tail wind you will very quickly increase your range, while a 40 knot headwind will bring the number back equally as much. I would calculate range based on usable fuel and fuel burn of the engine. but if they are saying 1900KM I would plan for the 1750KM range to be safe.

  If regular service for an airplane is declared to be after 7000 km of flight or X hours of flight, what has to be done usually in those services? Changing of oil, changing of filters?? How expensive usually is that?

Aircraft service is (as far as I know) done on hours not miles flown (although they are related in a way. Here in the US you need a yearly inspection which includes lots of things like testing gear and other components and ever XXXX hours when your engine hits TBO (to be overhauled) you need to overhaul it. This overhall can be costly but is very dependent on the engine. It can range anywhere from 15K to (insert large number here). You are also responsible to have anything fixed should it break obviously.

  Cost to park

There are 2 things here your storage cost and the cost when you actually go somewhere. I fly out of KPNE and have spoken to a few people about the cost of a tie down/hangar. It seems I can keep an airplane in a tie down for less than $100 a month but it would be outside all the time. Hangars get pricy and can be rented or bought. There are lots of small airfields where I am and I'm sure its possible to store a plane for cheaper than at KPNE.

As for going somewhere that depends on ramp fees. Here in the US these fees are sometimes waived if you buy gas or very nominal in the first place. Some airports also have a small landing fee (KPNE is $5). I don't know about EU (although I'm sure they have it) but here in the US you can get the AFD (airport facilities directory) which has lots of info on these kinds of things. Most airports/FOB's now have websites that list their prices as well.

  Anything else you think is important to know about possessing and airplane of that type.

It seems you are looking for a fixed number to a question that does not have an answer like that. You must first identify your mission then you can find a plane to fit the mission profile. You can then look at the prices of other people who have owned that plane and you may find what you seek but you will also find that there is a HUGE deviation in the prices as no two planes are alike.


Are VOR airways being replaced by RNAV routes as VORs are decommissioned? I understand that VORs in the US and elsewhere are being removed from service gradually. The FAA plans to maintain a Minimum Operational Network, but still I imagine many VOR airways will also have to be removed when their respective VORs are shut down.
Is there any indication that the old VOR routes will be replaced by RNAV routes (Q and T routes)? Or will the VOR airways be removed without replacement, leaving pilots to file direct routes instead of using published routes?

Short answer: there seems to be no general plan to replace airways with Q and T routes. The FAA originally proposed replacing them, but the final rule doesn't include it.

You can review the source rulemaking documents in the Federal Register and it looks like the idea of replacing (or retaining) airways seems to have been discarded, possibly in response to comments.
The initial notice suggests that the idea was indeed to replace the airways:

Existing airways, routes, and procedures eventually would be replaced
by RNAV Q (high) and T (low) Routes, and RNAV STARs and DPs.

The proposed rule got some negative feedback on the T and Q route idea from two major industry lobbies:

Comment #20: AOPA and the National Business Aviation Association (NBAA) both expressed support for direct routing and avoiding
excessive implementation of additional T and Q routes.
FAA Response: In the NextGen environment, T and Q routes increase capacity and efficiency while maintaining safety by minimizing impact
to air traffic control. T and Q routes allow controllers to safely
manage air traffic during peak periods and to ensure predictable
transitions between busy traffic areas. T and Q routes overlaid on
existing airways defined by VORs could mitigate potential impacts to
the discontinuance of VOR navigation services.

The final rule has only one mention of airways, and doesn't mention T and Q routes at all:

Retain most VORs in the Western U.S. Mountainous Area (WUSMA),
specifically those anchoring Victor airways through high elevation
terrain.

My reading of all that is that the FAA originally intended to move airways to Q and T routes, but dropped the idea after receiving feedback. Or perhaps they just floated the idea to see what the reaction would be.


What's going on with sudden acceleration/deceleration in mid-air? I was recently on a flight between LGB and PHX. I've been flying since I was 5, am now 31. After takeoff, as the plane approached cruising altitude, the plane slowed down. A lot. Then accelerated again, followed by another slowing down. This happened at least 4-5 times during the short flight, and before landing we made a complete circle around the airport, I'm assuming to comply with which runway to land on. My question is: why, or what cause, does a plane slow down in mid flight where you move forward in your seat, like hitting the brakes in your car too hard multiple times. I understand training and all that, I want to know the cause. To put it in perspective, I assumed the engines stopped. And to increase the nausea, we were delayed by a mechanical issue for an hour.

Without knowing the specifics of the flight, there could be a lot of reasons for this.

One guess for the sensation of accelerating and decelerating We’re intermittent steps at fixes on the departure procedure the pilot flew out of KLGB at certain altitudes and airspeed either as part of the DP or as assigned by ATC in order to facilitate departure from SoCal airspace to enroute.  That and a little sloppy airmanship on the part of the flight crew.

As for the “circling” at KPHX,  most likely that was the pilot flying a STAR with ATC final vectoring to a visual approach or SIAP for runways 25L/25R/26 at Sky Harbor Intl.


What is needed to operate a LSA aircraft at night? As a PPL holder in the USA, what do I need to have on the aircraft (or otherwise?) in order to be able to legally fly at night?  LSAs are much cheaper to operate, so it looks very tempting in order to be able to fly more hours, I'm just concerned about getting stuck out at dusk, especially in winter.

Since you have your private, the LSA just has to be approved.

According to the FAA Order 8130.2G CHG 1 which covers LSA certification:

  (5) This aircraft is to be operated under VFR, day only, unless
  appropriately equipped for night and/or instrument flight in
  accordance with 14 CFR § 91.205, and when allowed by the
  manufacturer’s operating instructions.

So it must be properly equipped (see below) AND allowed by the manufacturer’s operating instructions.   You will need to check this with each manufacturer to see if they certified it for night flight.

91.205 says day VFR instruments (paragraph b) plus:

  (c) Visual flight rules (night). For VFR flight at night, the
  following instruments and equipment are required:

  (1) Instruments and equipment specified in paragraph (b) of this
  section.

  (2) Approved position lights.

  (3) An approved aviation red or aviation white anticollision light
  system on all U.S.-registered civil aircraft. Anticollision light
  systems initially installed after August 11, 1971, on aircraft for
  which a type certificate was issued or applied for before August 11,
  1971, must at least meet the anticollision light standards of part 23,
  25, 27, or 29 of this chapter, as applicable, that were in effect on
  August 10, 1971, except that the color may be either aviation red or
  aviation white. In the event of failure of any light of the
  anticollision light system, operations with the aircraft may be
  continued to a stop where repairs or replacement can be made.

  (4) If the aircraft is operated for hire, one electric landing light.

  (5) An adequate source of electrical energy for all installed
  electrical and radio equipment.

  (6) One spare set of fuses, or three spare fuses of each kind
  required, that are accessible to the pilot in flight.


Are there ILS approaches where a non-precision procedure isn't allowed? Are there ILS approaches where the LOC/non-precision procedure isn't authorized?

Yes, there are.

Note: This is as opposed to those ILS approaches listed as ILS or LOC in the title—such as KGEG ILS or LOC RWY 3—which do have an authorized LOC approach.

Special Authorization Cat I ILS, and Cat II & III ILS approaches do not have authorized LOC procedures. These are precision only approaches.

See KGEG approaches, for example. Specifically, the ILS RWY 3 (SA CAT I), and the ILS RWY 3 (CAT II & III) approaches do not have authorized LOC procedures.

See also this screen cap of the KGEG ILS RWY 21 (SA CAT I) approach:

[][6]


Do dispatchers ever update and re-send a flight plan to an aircraft in flight? In what scenarios would the dispatcher recalculate the flight plan and send it to the pilot via ACARS after take-off?

Anytime the original routing or altitude is significantly changed, a new flight plan is calculated by dispatch and sent to the aircraft.  Significant changes could mean the aircraft may not have enough fuel to reach the destination. Even minor changes are routinely re-calculated and sent to the aircraft.

The pilots send dispatch the new routing and altitude along with an updated ETA and FOB(fuel onboard) for the next waypoint. The flight plan is then recalculated from that point and sent to the aircraft.

Routing changes can be due to traffic conflicts, airspace closures, military activity, volcanic activity, etc.

If for any reason the aircraft is unable to contact dispatch, the pilots must do their own calculations to insure they have enough fuel.

If the fuel remaining is marginal, the flight can be re-filed with a new alternate closer to the final destination. If conditions can be met, the flight might be re-filed with "no alternate".


Voltage induced in high-tension magneto ignition system Why is there no voltage induced into the secondary winding (in high-voltage step-up transformer) when the ignition switch is closed (OFF).
When the current flows in the primary winding of the coil a magnetic field is generated. This interacts with the flux from the magnet. Assuming that the ignition switch is closed, the flow of alternating current created by the interaction of the two magnetic fields will flow to the ground. Will the flow of alternating current in the primary (while the ignition switch is closed, OFF position) induce a current in the secondary? If it does not, why not?

I assume you're talking about an aircraft mag.  Mags are never really OFF off.  Instead of ON/OFF, it's more like ON, and "on but not on enough to work".

With the ignition switch OFF, grounding out the primary, the alternating current generated in the primary as the mag spins flows to ground, and it does induce a voltage in the secondary as the current alternates, but this voltage is much too low to be able to jump a plug gap.  So the mag is effectively off if not totally off.

To get a spark, the flow of alternating current in the primary needs to be fully cut off by the opening of the points within the primary to create a field collapse strong enough to generate sufficient high voltage to be induced in the secondary.


How much can a plane deviate from its route to Paris (CDG and ORY) before an alert is raised? I was reading about the 9/11 hijacks and the Wikipedia information about flight AA 11 mentions that

  Of the four hijacked aircraft on 9/11, the nine minutes of advance
  notification about the hijacking of Flight 11 was the most time that
  NORAD had to respond before the aircraft crashed into its target.

I am sure that these tragic attacks have lowered the bar in terms of time to react to a off-route deviation by planes and was wondering what this means for flights to the Paris airports CDG and ORY.

I have just taken a snapshot of the flights (courtesy of flightradar24)

and it seems like (quite understandably) that planes avoid Paris intra muros. This said, they are quite close and the ~20 km distance from Paris is a ~2 min flight.

Since the closest airports which may host Rafales are I believe Le Bourget and Vélizy-Villacoublay, the interception planes would need much more than that to be on their tracks before they entre Paris.

With all this said, how much can a plane deviate from its path before Paris before it is intercepted (and brought down a way or another)?

Note: while I am particularly interested by Paris (living there) I can understand that the information is classified (though probably easily guessable for someone who knows about aviation). In that case another public information is welcome to understand how things changed after 9/11.

I think "it seems like (quite understandably) that planes avoid Paris intra muros" is jumping a bit to conclusions. I went to Flightradar24 and found this, without even waiting for anything interesting to happen:

It didn't go exactly over the Notre-Dame, but even on this scale you should be able to see that it did cross inside Boulevard Périphérique.

On the other side of the Channel, such overflights are extremely routine when Heathrow operates east-to-west (as it usually does). Here's one (again found live, without waiting for it) that could have dropped bombs on the Crown Jewels if it had any to drop:

Perhaps more relevant than the Crown Jewels, this flight path is just a few hundred meters from the City of London skyscrapers. If the pilots had wanted to reenact 9/11, they could have crashed into something tall and famous about 10 to 20 seconds after deviating from their expected horizontal flight path. (But they'd need a bit more time than that to descend -- call it a minute or so from the first non-routine control input).


What is the reapplication process for a suspended dispatcher certificate? I had my dispatcher certificate suspended for a year for leaving the testing site before I could provide an adequate urine sample.

I did not realize this was a reportable event. I accept the suspension but am looking for the process to follow to get reinstated after the 1 year period.

I know very little about this, but JO 2150.3C says that if a certificate is suspended for a fixed period of time, it's reinstated at the end of that time if you meet whatever conditions the FAA requires (p. 7-4):

  Indefinite suspensions are used when the Administrator has reason to
  question, but is unable to determine, a certificate holder’s
  qualifications, or when the certificate holder does not comply with
  statutory or regulatory requirements to cooperate with the FAA. For
  indefinite suspensions, the Administrator suspends the certificate
  until certain conditions are met, e.g., until a reexamination or
  reinspection under 49 U.S.C. § 44709(a) is successfully completed. The
  period of time the certificate is not effective is specified in the
  order of suspension, and once the required period has passed, the
  certificate is reinstated.

Your question doesn't have many details - and I understand that you might not want to share them! - but I take that to mean that if your certificate was suspended for one year, it will be reinstated after one year has passed, as long as you've done whatever the FAA wants you to do in order to qualify for reinstatement.

The phrase "until certain conditions are met" implies that there's no standard way to qualify to reinstatement; it probably depends on the reason that the certificate was suspended in the first place. Page 9-15 of the order lists reasons for suspension and they're quite varied, so presumably the "certain conditions" are too.

On the other hand, if a certificate is revoked then it cannot be reinstated (p. 7-4):

  Unlike a suspension, a certificate that has been revoked cannot be
  reinstated. A person whose certificate has been revoked may be issued
  a new certificate provided that the person meets the qualification
  requirements for the new certificate. To be issued an airman
  certificate following revocation, an individual must retake all tests,
  whether written, oral, or practical.

Your local FSDO could probably confirm that, although if your situation is more complicated then an aviation lawyer might be more helpful.


Is it legal to listen to aviation frequencies in the UK? Am i allowed to purchase an ATC scanner and listen tho what is being said in the control tower? Thank you

Yes, you can purchase a scanner - these are freely available in the UK.

No, legally, you can't listen to air traffic control. However, in real life, this is generally not enforced. Go to any airshow or airport observation area and you'll find people using scanners openly.


Is it possible to "take a bullet [missile]" for another plane as shown in the movie Air Force One? In Air Force One a fighter jet maneuvers between a missile and the president's plane, as shown in this clip.

Is such a maneuver possible?
If not, what could be done in that situation?

Possible and Plausible are two different things.

Is it possible to fly a fighter jet between a missile and another aircraft, and either (a) confuse that missile so it follows the fighter instead) or (b) have the fighter be hit by the missile instead of the original target aircraft? Yes.
Modern fighters are capable of maneuvering in the manner shown: they can even sustain knife-edge flight or vertical climb for a while. It's even possible that in a moment of desperation a pilot would attempt such a maneuver, sacrificing themselves and their aircraft to save their commander-in-chief.

(The G-forces involved in these maneuvers may be unpleasant or even unbearable for the pilot, but if you're committing yourself to a course of action that ends with your plane blowing up to save another plane the G-forces are probably the least of your concerns.)

It isn't plausible that such a maneuver would work - at least not as depicted in the movie.

Missiles are REALLY FAST - this footage includes several slow motion shots of an air-to-air missile as it's fired (at it's slowest relative velocity), and it's still pretty darn quick: It's gone in a few frames of high-speed footage.

For this maneuver to work the intercepting pilot would need to be in exactly the right position and exactly the right time, and perform the maneuver perfectly in order to intercept the missile: A little error in any direction - too fast, too slow, too far left, or too far right - and the  missile would fly right past them and continue on toward its target.
The intercept is further complicated by the fact that, assuming the missile is guided, both the missile and the target are maneuvering as well.
(If it's a non-guided "dumb" missile all the target aircraft needs to do is change course to avoid being hit - a maneuver that might stress the airframe a bit, but certainly less than being hit by a missile would.)

To give a little more context, the "anti-missile missile" programs have often been described as having your friend throw a baseball over the roof of your house while you stand on the other side and try to hit it with a golfball as it comes over the top.
This intercept is of similar difficulty, except the balls involved are all steering themselves toward different objectives.


How much does a refueling stop for an Avro RJ85 cost in Bolivia/Colombia? One possible motive for the LaMia disaster is that they were attempting to save money by not refueling. That may or may not be true and this is not the place to debate that.

Reports say they were supposed to refuel in Cobija, Bolivia and after the delay they would have had to refuel in Bogotá. How much would a refueling stop for that airplane have cost in Cobija and/or Bogotá?

It's hard to give an exact figure as their are a number of considerations. If we assume that the re-fueling stop is at El Dorado, and the airplane was a BA146 (RJ85 is a variant) then approximate costs might be (in USD):

Landing fee: at about \$6 per thousand kg, and 42,000 kg would be about \$250. Add 5% for a night landing and another 5% for a night departure for about \$280
Handling charges: this is hard to say, estimate $100
Jet Fuel: the BA146 can carry up to 3000 US gallons, assume 1500 as it's a short hop, at \$3.16/gallon that's \$4740

So it would seem that about \$5000 is a good working figure. Keep in mind they wouldn't have used all that fuel to get to their destination, there would have been plenty left and they wouldn't have had to fill up completely on the way back, but the most expensive part of a flight is the climb to cruising altitude, so 2 climbs are more expensive than one. There might also be ATC fees for filing another flight plan, and taxes not listed, I would imagine that wouldn't change the costs that much - the fuel is still the big chunk of the cost.


What is the Fuel-Oxygen ratio for a large turbofan at cruise conditions? What is the Fuel-Oxygen ratio (by mass) for a large turbofan at cruise conditions?

In order to be concrete, I'll just pick an engine at random. I pick the GE90-115B. Okay it's not really random, it's just the largest turbofan I know of.

The GE90-115B has a bypass ratio of 9:1. So if 1000 units [of air] enter the fan, only 100 will make it to the combustion chamber.

Kerosene burns efficiently at 15:1 (air to fuel). But not all the air in the combustion chamber is burned. Only around 22 (average) of the 100 will be burned, the rest will provide cooling, flame stabilization, and dilution.*

So of the 1000, 22 are burned at the 15:1 ratio. Total ratio will be 1000:1.5 (air to fuel). Since oxygen is ~20% of air, then the ratio is 130:1 (oxygen to fuel). (Note: bypass is included.)

To validate that figure:

If the fuel flow (per engine) is 2500 kg/hour (modest value in cruise†), then that means the engine takes in ~1,667,000 kg of air per hour, or 460 kg per second. That agrees (give or take) with the numbers in this post (PDF does not confirm the GE90 version and the fuel flow†).

  According to The GE90 - An Introduction, the GE90 has a mass flow rate‡ of 1,350 kg/s at take-off and 576 kg/s at cruise.

* The Jet Engine - Combustion Process.
† It varies with the airplane weight, cruise altitude, speed, etc. See here (in lb/hr) for the GE90-90B from a 777-200 flight manual, it varies from 2140 to 4440 kg/hr.
‡ Mass flow rate is for the air, as NASA puts it: "The total mass flow rate through the inlet is the sum of the core and fan flows."

FWIW, the -115B1 is the exclusive engine for the 777-300ER. Based on this official data from Boeing (last slide), at a 365-passenger load on a 6,000 NM journey, each engine burns an average of 3790 kg/hr (heavy load; takeoff and climb included), which is within the above -90B range, i.e., 2500 is a correct value to use as the -115B will also have a similar wide range. (Arriving at that figure requires the 777 cruise speed of 892 km/h.)


What is required for a pilot to fly in another country? What is required for someone who holds a pilot certificate in one country to fly in another country? First, I'm wondering if there are any general rules that would apply to any such situation. Second, for the sake of a specific example, what would be required for someone who holds a private pilot certificate in the U.S. to fly an aircraft registered in the Philippines within the Philippines (assuming that the aircraft type is one for which the pilot is rated in the U.S.?)

For your specific example, Philippines Civil Aviation Regulations Part 2 (Personnel Licensing), section 2.2.4 covers "Validation and Conversion of Foreign Licenses and Ratings." It states that a holder of a license from a "Contracting State in accordance with ICAO Annex 1" (this includes the United States) is eligible for "validation" of their foreign license. The validation process involves presenting the appropriate documentation of your license, ratings and logbook. For more than just PPL privileges, you must also pass a "skill test" and demonstrate the required knowledge and ability. The conversion ("validation certificate") gives you the same ratings you had on your US license and is valid for 1 year.

The FAA has a very similar policy for foreign-to-US license conversion, covered in 14 CFR §61.75. As in the Philippines, the FAA does not require a skills test for private pilot privileges, but a written knowledge test is required for conversion of an instrument rating.

Another question here on ASE discusses conversion from EASA (Europe) to FAA (US).

Most other ICAO states recognize each other's licenses in a similar manner. In all cases you have to present your license and proof of experience, and in some cases pass a written test and/or checkride. I haven't look up the exact regulations for, say, EASA (Europe) or CAAC (China) but I'm sure they aren't far off from the examples above. In reality diplomatic considerations probably also come into play: a holder of an Iranian license would probably run into problems attempting to convert/validate their license in Israel, even though both are ICAO-contracting states, since they aren't on very good political terms to say the least. But this will likely be the exception rather than the rule.

(There are only 3 non-ICAO states: Dominica, Liechtenstein and Tuvalu.)


Is the sweep angle of an inverted wing zero degrees? Is the sweep angle of an inverted wing zero degrees, when the angle between the fuselage and the inverted delta wing is 90 degrees? Or is it different because the span of the wing isn't constant over the chord.

Sweep is normally given as the quarter-chord sweep. If not, it must be made clear by some qualifier, like leading-edge sweep.

Your previous questions let me suspect that you are into a special version of ground-effect vehicles, the Lippisch aerofoil. The picture below shows the X-114.

The wing is a delta with negative sweep, so it has a straight leading edge and a forward-swept trailing edge. The idea is to have a positive angle of attack and very little space between the trailing edge and the ground for maximum ground effect.

Such a wing has a negative sweep angle. If you take the weighed average of leading ($\varphi_{le}$) and trailing edge sweep angle ($\varphi_{te}$), you get the quarter chord sweep angle ($\varphi_{25}$): $$\varphi_{25} = \frac{\varphi_{te} + 3\cdot\varphi_{le}}{4}$$


Is there an ARINC label/data that can be associated with a gyroscope's precession? I am looking to read the precession of a gyroscope off of an ARINC bus, is there an ARINC label that can be associated with the gyroscope's precession value?

My thoughts are, that it might have something to do with the drift angle, flight path angle, and/or the magnetic heading. Am I in the ball-park? Or is there no way to measure the precession values?

Short answer: No easy way. It may be possible for a crew to detect some drift by comparing the IRS mag heading to the magnetic compass.  This does have problems though as the IRS doesn't really 'measure' mag heading.  It works in true heading and calculates mag heading by applying a magvar correction from a table.
Modern aircraft do not have free gyros that output data. They have inertial reference systems (IRS). The IRS has multiple gyros and accelerometers and outputs a complete navigation solution.  They also have an internal GPS (or an input from an external GPS) to improve their accuracy.  So there's not a lot of 'drift' in the output solution.
These units have internal integrity monitors and will report a fault to the crew if the nav solution exceeds limits.  In some failure modes the IRS will revert to an attitude only mode (ATT) that just outputs raw rates and accelerations (free-gyro mode).  In this case, the crew can provide a heading update to set a heading.  This will drift just like a stand-alone directional gyro.  The crew will have to check it regularly against the mag compass and update as necessary (~ every 10 minutes).


Are turbofans compensated for gyro effect? In a multi-spool design is the gyro effect canceled or mitigated by having the two or more spools spinning in different directions?

There are a few counter rotating turbo fans, such as the GEnx. But the majority are co rotating.


Have crash investigators ever used pilot cameras to help find the cause of a GA crash? With video cameras being completely ubiquitous and GoPro cameras able to be mounted pretty much anywhere, lots of GA pilots now like to make videos of their own flights. A passenger's cell phone video was used as supporting evidence in the Germanwings crash. Have there been any situations so far where a GA crash has been puzzling to investigators until they watch the video from the pilot's camera which shows the cause clearly? Are they even allowed to do this (anywhere, but NTSB in particular) or are there privacy regulations which prevent them from doing so?

Absolutely: Here's one of many examples, and you can search the NTSB database for "GoPro" and find plenty more.

The NTSB will use anything and everything available to them in their investigation, though release of certain materials is prohibited by law (e.g. CVR contents are not released, only transcripts).
I believe the NTSB is observing a similar protocol for onboard video: A synopsis is released (including a transcript of conversations) when requested, but the actual video is kept confidential by the agency -- I am not certain in that though, and the NTSB press office could provide a more detailed answer on their rules surrounding cockpit video / audio in GA crashes.


Does "nose dive" have a technical aviation meaning? I've usually heard the term 'nose dive' used in a metaphorical sense -- "Wow, your stock portfolio is really in a nose dive!"

Does it have any legitimate aviation meaning?

More specifically, is it redundant?  Are there types of dives which do not involve a nose-down attitude?

Are there types of dives which do not involve a nose-down attitude?

Yes (although these are not always intentional): a graveyard spiral can occur without a nose down attitude. You can also stall a plane nose high and begin diving to the ground maintaining a stalled nose high attitude, this is similar to what happened to AirFrance 447. A flat spin will also result in "falling" vertically with a relatively flat nose attitude.

In my experience "nose dive" and "dive" are generally interchangeable.


Why do some airports have more than 2 runways, when LHR can get by with 2? I was looking at aerial imagery of various airports and noticed how some have a large number of runways (4-6), while others have a small number.
Specifically, I noticed that Heathrow (LHR) only has 2 runways, but it is the busiest airport in Europe by passengers. In comparison, the following busiest airport have many more runways (Paris Charles-de-Gaulle (CDG) has 4, Amsterdam Schiphol (AMS) has 6), but fewer passengers.

Why do some airports have more than 2 runways, when LHR can get by with 2?

Heathrow is somewhat of a standout when it comes to volume. Your wording, that LHR "gets by" with 2 runways is apt. By movements, it is the busiest 2-runway airport in the world. By passenger volume it is second only to Dubai Intl. (Note, though, that DXB is home to Emirates, who has the world's largest fleet of A380's. They are the only airport that averages over 200 passengers per movement!)

Aircraft movement is the best way to look at it from a runway usage standpoint. The following chart is sorted by aircraft movement.*

As you can see, the top 3 all have 5 or more runways. There are 7 large airports with 5 or more rwys and they all fall in the top 16. The top 16 is rounded out by 5 airports with 4 runways, three with 3 runways and... LHR. The next 2-rwy airport on the list is Benito Juarez Intl. in Mexico City clear down at 21st on the list.

Any busy airport with 2 runways has to make those runways work as tightly as possible with little room for error. Otherwise they end up with delays. If I sort the list by movements per rwy, all of those with 2 rwys rise to the top. 10 of the top 15 have 2 rwys.

So, how does LHR pull it off? How do they manage to pack all those flights in to just two runways?There's a downside to handling that kind of volume with so few runways. The following collage gives a clue as to what that is.

Those are just a random pick of arrivals at a couple of random times yesterday morning at LHR. There was no significant weather at the times. As you can see, you just don't arrive at LHR without being put in a holding stack. Every single flight I could find had to do at least one racetrack. At any point during the day, in places like Chesham, Effingham and Brentwood, if you look up there will be as many as 6 or 7 aircraft doing racetracks waiting to be cleared into Heathrow. That makes for very efficient runway usage when there are 20 planes waiting in line, but it's terribly inefficient for the airlines and passengers to have to spend so much time burning fuel circling around London.

On the flip side, building more runways has a down side too. It will get the planes out of the air quicker, but, as happens at Schipol - which has 6 runways - you can end up with a long taxi back to the terminal.

All data was taken from Wikipedia.


What are "referred" speeds and "referred TET"? i'm currently reading the Rolls Royce publication The Jet Engine. It makes reference to "referred speed", "referred TET" and "referred mass flow". Referred speed seems to be defined as N/sqrt(T). I guess that N is engine speed but I'm not clear on why it is divided by the root of temperature. Also can someone advise how referred mass flow and referred TET are defined please?

Referred speed is a way of compensating for the fact that air density changes with temperature.  For example, let's say you are designing a new turbojet engine. You fire up your engine one warm sunny day in July, and note that when the shaft speed is 5,000 rpm, it's making 10,000 pounds of thrust.  But then later, on a cold winter evening in December, you run the engine to 5,000 rpm, and now it's making 11,000 pounds of thrust!  What happened?  Did your engine suddenly get more efficient?  No.  It's just that colder air is more dense.  So for that same 5,000 rpm, you are pumping a lot more mass of air. Now, where referred speed comes in.  You are going to have to tell the pilot of the plane how to set thrust.  i.e. he wants to get 10,000 pounds of thrust, no more and no less.  You can't just tell him to set 5,000 rpm, because that will be a different amount of thrust depending on the ambient temperature.  So you tell him to set a specific "referred speed".  If you go to the same referred speed, you'll always get the same amount of thrust, no matter what the temperature.

You should also look up corrected speeds.  That is a very similar concept.


How does cost per seat-mile differ between commercial and private jets? I was reading an article the other day that mentioned many smaller private jets are more efficient, faster, can climb quicker and land with less space than larger commercial aircraft. Some of the obvious metrics make sense such as shorter landing distances, but the efficiency peaked my curiosity.

I am basically asking what is the cost difference or cost per seat mile difference in say a a Boeing 737 vs a smaller often private jet, say an Embraer Legacy 600 or similar with its maximum seat capacity setup.

I did some basic math to figure it out in terms of current gas prices.  I got that a private jet is about 6x more expensive.  Keep in mind it is probably more in reality because these jets aren't being used as much as an airliner so the rental price will be higher as well as the fuel.  But like I said, this was just an estimate based on current fuel prices and performance of an airliner vs a private jet, to give you an idea of the cost difference.


Shouldn't there be ATIS/sign information on sloped up runways? I landed on Catalina island runway 22 last Saturday after the installation of a new concrete runway.

To make it easier for heavyweight planes to land and after a short roll stop, they have made the runway curving up. It was very tricky to land. Because of optical illusion.

I realized at the numbers I was barely a few feet up and considering the fact that the runway starts at the edge of a deep cliff, it was potentially catastrophic.

I make sure I watch out for this and adjust my glide slope next time.

My question is shouldn't they provide some sign or on the ASOS add a heads up.

To clarify, the US Marines did the renovation of Catalina project recently which apparently has finished about a week ago. They have changed the topography of runway in a certain way, made it like bowl apparently, to make it easy for heavy airplanes to land in this short runway.

The changes have not been reflected in VFR charts or Supplement, or other aviation documents, at least to the best of my knowledge.

EDIT

I just add my comment for pilots who plan to land at Catalina.

Because of the fact that the vanishing point (the point the sides of the runway merge in horizon in pilot's perspective) has changed, appearing higher than before, at the short final one perceives they are flying at a higher altitude, look out for this.

FAR 91.103 says (emphasis mine):

  § 91.103 Preflight action. Each pilot in command shall, before
  beginning a flight, become familiar with all available information
  concerning that flight. This information must include -

  (b) For any flight, runway lengths at airports of intended use, and
  the following takeoff and landing distance information:

  (2) For civil aircraft other than those specified in paragraph (b)(1)
  of this section, other reliable information appropriate to the
  aircraft, relating to aircraft performance under expected values of
  airport elevation and runway slope, aircraft gross weight, and wind
  and temperature.

The most "reliable" place to find this information is the FAA Chart Supplement, which says this for KAVX (emphasis mine):

  Rwy 04 final 2,300´ steep 2.1% downslope, Rwy 22 upslope preferred
  ldg. Pilots cannot see acft on opposite ends of rwy due to gradient,
  must announce taking acft rwy on unicom prior to dep.

Any time you see mention of runway slope, you should be aware that something strange (and likely dangerous) is going on there.  Ditto for the cliffs on the diagram, which you are expected to know would create a downdraft on short final.

Since you were legally required to become familiar with this information when you planned a flight there, no additional notice (such as signs or NOTAMs) was required.

If there had been changes to the airport not yet in the CS, there would be NOTAMs for the airport until the next update cycle--and you would be responsible for knowing those as well.  However, with the airport being closed five months for construction in this case, they had plenty of time to get the CS updated before it reopened.


Too soon to pass the IATRA exam? (Canada) I just finished the IFR group 1 rating this week. Currently at 220h Total flight time with CPL, no job in sight (of course), and wondering if I should start studying for the IATRA now or wait until I'm closer to 250h and/or a job?
Thanks in advance, have a delicious day!

If you have the time on your hands might as well get started with the study part.  IATRA is the ATPLs condensed into a single smaller 50 question exam.  You will expand your knowledge base and it never hurts to acquire knowledge sooner rather than later.
Don't take the exam right away though, as it is only good for 2 years and it might be a lot longer than that before you'll land a job that needs a multi-crew qualification.  There's a lot of pilots on furlough and it's going to be several years for the industry to reabsorb them all.  Most of the opportunities are going to be in the North.


How do you load test a wing rib? When builders say they load tested a wing, most of the time what they are saying is that they load tested the wing spar(s) by turning the plane upside down and putting weights on the wing. This procedure doesn't load test the ribs, so how do you load test a single rib?

Rib is load tested upside down with weights on its flat bottom side to simulate air deflection during flight,and two ropes holding the rib up at positions where the spars will sit.


Is Saudia's 777-368ER The Longest Passenger Aircraft? I watched a video about passenger aircraft length (video was removed from YouTube)
It says the longest passenger aircraft is Saudia's 777-368ER.

Saudia web site says their 777-368ER is 78.86m.
But according to the Boeing web site, 777-300ER is 73.9 m.

Is the 777 be able to made longer as customer option?
I couldn't find any news souce about Saudia purchasing a modified 777.

As far as length is concerned, there are two versions of the 777 classic series, the -200 and -300. The -300 is the longer one, at 242 ft 4 in (73.86 m). Other than choosing one of these two models, there is no customer option to change the length of the plane. I'm not sure where the Saudia data comes from.

But the 777-300 is not the longest plane in the world. The A340-600 previously held that title, at 247 ft 4 in (75.36 m). The 747-8 surpassed this at 250 ft 2 in (76.3 m). The 777-9 may enter service in 2021, setting a new record of 251 ft 9 in (76.7 m).


Is there a legal minimum stop time between 2 legs? This question is restricted to airliners transporting many passengers (let's say more than 20).

Between two legs, airliners stay at the boarding gate for a limited time, sometimes less than an hour. The stopover duration at the gate is typically dictated by the time to refuel and disembark/embark both freight and passengers. I understand the cost-saving logic behind the decision to make this operation as fast as possible.

However, in a competitive market, safety may not be compatible with shorter turnaround times. No pilot would irresponsibly compromise safety by leaving the gate without fulfilling their safety and security obligations, but I wonder if there is a minimum turnaround time imposed by regulation to avoid downward pressure on turnaround times?

EDIT:

let's focus on the fastest and simplest scenario: no crew change and no refueling (the crew took enough fuel to make several legs)
I don't want to be restricted to one legislation or one part of the world. The question is: does any regulation exist to require such a stop time?
I just thought that technically, brakes should be cooled down before the next take off roll.

Well, in some cases, zero.

In Australia, for a long time only two airlines (Ansett and TAA) were allowed to fly between capital cities. To work around this, East-West Airlines practiced a touch-and-go at Albury, half way between Melbourne and Sydney. Legally, these we considered separate legs (at least for some time).


What is the purpose of the extra horizontal and vertical surfaces on the tail of the Beechcraft 1900? I am building a very large(11ft span) twin engine RC airplane that is loosely based on the Beechcraft 1900D design.

I can't help but notice the extra horizontal surfaces sticking out of the aft fuselage and the vertical surfaces hanging down from the ends of the horizontal stabilizer.

Could it be that after test flying they decided that the center of pressure needed to be moved further aft, but maybe it cost less to add new small surfaces instead of altering the design of the current surfaces?

Yes that is what is the most cost effective solution after flight testing has demonstrated that the vertical tail surface has to be increased for instance. The little winglets at the end of the horizontal tail do increase aerodynamic efficiency of the stab - plus they just look cool.

The BAe 125 stuck a bit of fin on top of the original fin design, the Beech 1900 added the extra vertical tail surface underneath the aft fuselage cone, in the form of 2 v-shape surfaces which also help the total horizontal tail area.


Do Airbus aircraft fitted with ACT have additional fuel system controls? Do Airbus aircraft fitted with ACT (Additional Center Tank) have a push button that controls the fuel transfer to the main center tank? If yes, where is it located?

(Source: Airbus)

Yes they do on the same overhead fuel panel. The additional pb is shown above. If it is not pushed and no fault is shown, then it is in automatic operation, and pushing it allows manual fuel transfer.