Why are jet fuel prices very similar in North America and Europe, yet automotive fuel prices are very different? Why is the pricing difference of jet fuel between North America and Europe extremely small, unlike automotive gasoline?

As of June 22, 2018, the prices in USD per barrel of it between the two continents are 88.0 and 87.8 and slightly older data confirm the existence of a small difference (I have not encountered a comprehensive dataset). Yet automotive gasoline in Europe usually costs 2-3 times the price it does in the US, comparing each US region to the very roughly analogous European one (based on income, geography, etc.). Why is this?

Jet fuel for international commercial aviation is effectively not taxed due to an agreement between ICAO member states. (See here ICAO PDF  ). Therefore the prices closely track to cost of production and distribution. These are similar worldwide. Differences exists due to local taxes on companies, difference in costs of transport, effects of competition on price etc, but these effects are limited.

Automotive fuel is taxed. I am originally from the Netherlands, where we have one of the highest taxes in the world when it comes to fuel taxes. Petrol costs at the moment approximately 1.66 Euro/litre, of which 68.84% is taxes.

In the US, the average total tax (federal plus local) is \$0.4818 on a gallon of gas (equivalent to \$0.1289 per litre).

So the difference in tax makes most of the difference in automotive fuel prices.

Sources: wikipedia


Can a plane bank without turning? Can planes bank without turning, and if so, how is it possible?
A plane's wing is designed to naturally create lift; the explanation for that is that the greater speed of the air moving over the wing reduces the air pressure above the wing and air pressure from underneath pushes the wing up.
But when the plane is tilted to the left or right relative to Earth's surface and gravity, shouldn't it be "pushed" to the left or right?

Yes it can. The steady-heading sideslip (SHSS) maneuver is used in flight testing to demonstrate static lateral/directional stability (similar maneuvers exist as sideslip approach in crosswind, or stabilized control with one-engine-inoperative at low speed). In this maneuver, rudder is applied to hold a sideslip, which generates an opposing side force and rolling moment. The rolling moment is neutralized via ailerons, and the side force is canceled out by banking to the opposite side. Once at steady-state, the aircraft is maintaining a rectilinear course, while banked.

Adapted from NASA IS-97/08-DFRC-01


What is the difference between side-by-side vs under-cockpit engine intakes? What is the main difference between these two engine configurations?

What are the differences between planes that have the intakes below the cockpit as compared to those who have them on the sides?

What are the aerodynamic differences?

How does this affect the speed/radar signature/maneuverability of the aircraft?

These two configurations are used for almost every existing type of small military aircraft, be it a fighter, an interceptor, ground attack or a bomber - why so? It would be interesting to know why some aircraft have the configurations that they do.

I wouldn't call the Su-27 small, but that is another issue.

The main difference is the wing planform. The Su-27 wing is optimised to work over all angles of attack up to 120° with very little pitch moment change. This requires the addition of strakes which create vortex lift at higher angles of attack. With this planform the straight side intakes would be impossible. But there is more to it.

At high angles of attack and high transsonic or supersonic speed, when thrust is needed most, the precompression below the strakes increases the efficiency of the intake.

While the F-15 was optimized for speed and transsonic agility within the usual angle of attack range, the Su-27 (and MiG-29, which uses the same basic design) are optimized to be flyable over all possible angles of attack which might be encountered in air-to-air combat. The F-15 designers stopped when the planform and intakes were good enough. TsAGI only stopped until they could not improve the design anymore.

Now to your many detail questions:

  What is the main difference between these two engine configurations?

There isn't one, it comes down to details. Both designs support long, afterburning engines, show little yaw when one engine fails and the intakes allow Mach 2+ speeds. The details are less sideslip susceptibility in case of the F-15, because the fuselage helps to adjust airflow, and better high angle of attack performance in case of the Su-27.

  What are the differences between planes that have the intakes below
  the cockpit as compared to those who have them on the sides?

Again, the main difference is in off-design performance.

  What are the aerodynamic differences?

Now I run the risk of repeating myself. One is better in yaw, the other in pitch. You may decide for yourself wich is more helpful in air combat.

  How does this affect the speed/radar signature/maneuverability od the
  aircraft?

This are actually three questions, wrapped into one. In speed the F-15 intake has a small advantage if the greater freedom in adjusting intake geometry to Mach number is taken advantage of. This means that the upper lip can be adjusted, not only the lower lip and the ramps inside, as is the case for the Su-27 intake.

For radar signature, both designs are a poor choice. They are basically corner reflectors, just like the vertical tails. You can see that stealth was no consideration in both designs.

For manoeuvrability, it is the wing planform that counts most. Here the Su-27 wins hands down.


Most time-consuming tasks while a plane is on the ground How long should commercial planes stay on the ground after landing before they can take off again? What is the most time-consuming thing/task/operation that happens during this time? Is downloading maintenance data from a plane time-consuming?

Commercial aircraft only make money while in the air, so they should be on the ground as little as possible. How long they are actually on the ground varies with size of aircraft, schedule demands and type of operator.

Transoceanic flights are typically scheduled twice per day for a given aircraft. Schedules are at fixed times and there is usually only enough time for two crossings. This leaves a lot of time to "turn" the aircraft, so the pace is very relaxed.

LCCs on short flight legs try to turn the aircraft as quickly as possible. You have probably heard that when Southwest was just starting out, they were short a plane and had no financing to get another. They reworked their schedule and squeezed a couple more flights out of their existing aircraft to fill the need.

Aircraft manufacturers publish an expected turn time by station. Here is one for a 737-900:

In this example, servicing galleys and boarding passengers tie for longest elapsed time. Refueling is much shorter. Maintenance does not even appear.

More important than elapsed time for any given task is time on the critical path, since many tasks can be done in parallel. In this case, boarding passengers waits for servicing cabin, which waits for deplaning passengers. LCCs typically do not serve meals, so servicing galleys could be significantly shortened. Similarly, they might use a simplified process to shorten boarding time. You might notice that the tasks that have been shortened by LCCs are on the critical path, as you would expect.


What is the need for TCAS? Isn't it the job of the air traffic controller to assign altitudes and make sure airplanes do not collide in mid-air? Is having TCAS mandated or optional? If it is a mandate, then is there a mechanism to notify other airplanes that TCAS is off?

TCAS is part of a defense in depth strategy to reduce air accidents. ATC does not cover all areas, so TCAS adds protection where ATC coverage is missing. ATC is not infallible: humans can make errors and computers can go down. With TCAS pilots can get life-saving warnings even in zero visibility, without reliance on any ground based system.


Can someone identify this unusual plane at SeaTac airport? I saw this plane at the SeaTac Airport and thought it was very unusual. The wings look too small to even be functional to me. What kind of plane is this and what is it used for?

There is a big clue right underneath the "Sea-Tac Airport" decal - it says

  FIRE RESCUE

It can be seen a little better on this image

source: wikimedia commons

It is a rig used for fire and evacuation training.

  A unique tool the department uses is an aircraft mock-up designed for aircraft approach, entry and tactics training on the airfield. The smoke generated is not harmful to the environment and provides a realistic challenge.
  source: https://www.portseattle.org/page/training

The image below appears to show it in use:


How dangerous was this approach of a Dash8 Q400 really? There is a video going viral here of a Dash8 landing during a recent media hyped storm:

According to the description and imagery it is a Dash8 Q400 (registration D-ABQD), Eurowings flight EW9203. It did land during a storm with alleged 110km/h (60 kts) crosswind on Düsseldorf airport.
According to https://www.flightradar24.com/data/flights/ew9203 it landed at 12:13 local time on 18.01.2018, runway 23L or 23R. Within the video it is claimed that there is wind up to 110km/h whereas other sources from other places claim more like 80-90kmh (43-40kts), it probably varied by the minute.
Wind direction seems to have been mostly from west, with storm typical quick variations.
The crosswind limit for the Dash8 Q400 seems to be 32knt, quite below any of the cited wind speeds, however given the angle difference (230 to 270) a cited wind speed of ~50knt would have been just within the limit.
TL;DR
If there was the possibility of going to another airport (I have no idea if there was), should the pilot have diverted to a less windy area for safety reasons?

The relevant TAF that the pilot would have seen before going there is below (only showing the bits for the time of landing):

  TAF AMD EDDL 180929Z 1809/1912 22025G40KT 9999 SCT035
  TEMPO 1809/1813 26035G50KT
  PROB30 TEMPO 1809/1813 26045G65KT SHRAGS BKN015CB

So the pilot was aware of a strong cross wind possiblity, but even 26065KT is 27 kt crosswind (runway is 233) which is within the limits of the plane. So there was no reason to divert before getting there.

The metars just before and after the landing are below:

  METAR EDDL 181050Z 27045KT 9999 SCT037 BKN043 08/00 Q0993 TEMPO 27045G55KT=
  METAR EDDL 181120Z 27034G48KT 9999 -RA SCT028 BKN038 07/01 Q0995 TEMPO 27045G55KT=

So the "baseline" was 27045KT, i.e. 27KT crosswind, and the maximum gust wind was 27055KT, or 33kts crosswind, just 1 kt above the plane limit.

Note that the metar wind indications are rounded to the closest 10 degrees, so the worst case could have been a wind from 274 degrees gusting at 55 kts, or 36 kts crosswind.

We can assume that the pilot decided to continue the approach based on the wind information provided by the tower.

Whether the pilot should have aborted at the last second because the landing was not going as planned is hard to gauge on a video, but based on the information we have, the wind parameters were ok.


Why are the Phugoid and Short period approximated instead of calculated exactly? We can calculate the period and half-amplitude time for phugoid and short period using equations of motion. We will get an exact answer.

Then why is there a need for doing approximations to equations of motion for calculating period and half-amplitude time for both motions?

By approximations, I believe you mean the following (found in any major stability & control textbook and this MIT course note), where the $_0$ notation stands for undisturbed trim condition:

Short-Period damping:

$$\zeta_{sp}\approx-\frac{M_q}{2}\sqrt{-\frac{1}{V_0M_wI_{yy}}}$$

Short-Period frequency:

$$\omega_{sp}\approx\sqrt{-\frac{V_0M_w}{I_{yy}}}$$

Phugoid damping:

$$\zeta_{p}\approx\frac{1}{\sqrt{2}}\frac{C_{D_0}}{C_{L_0}}$$

Phugoid frequency:

$$\omega_{p}\approx\sqrt{2}\frac{g}{V_0}$$

They are useful because:

They are computationally easy, and offer first approximation during early conceptual design and rapid iterations. However, in the 21st century, that's not saying too much.
They offer important design insight to engineers. It's not enough to calculate the modes; more important is to understand how to change the aircraft design such that the modes are adequate. With the full linearized matrix, it's hard to appreciate how derivatives influence these results (certainly for me). Now when you look at these simpler equations, the effects are almost intuitive! For this reason, these approximations (especially the lateral/directional approximations) will never go out of fashion.

On another note, since aerodynamics, especially transonic aerodynamics, propulsion and the equations of motions are inherently nonlinear, the linearized matrix (and the concept of eigenmodes) is itself an approximation.


What are the main sensor value that cause High pressure compressor fault in turbofan engine? I have read the paper "Damage Propagation Modeling for Aircraft Engine Run-to-Failure Simulation" (Reference).
 I am doing analysis to find which sensors to monitor for the faults injected in the simulated datasets.

One such fault is high pressure compressor which caused the engines to be marked as failure.

My analysis gave me the following sensors:

Corrected fan speed (NRf in rpm),
Physical fan speed (Nf rpm), and
Engine pressure ratio (P50/P2).

I could not find the proper answers online. Could anyone be kind enough to ascertain how related are these sensors for the occurrence of HPC fault in a turbofan engine.

I'm not from the aviation background. I greatly appreciate any valid suggestions/references or answers.

It sounds like you are looking for an understanding of how the HPC efficiency affects the overall engine performance.  My suggestion here would be use NASA's excellent engine simulator: https://www.grc.nasa.gov/www/k-12/airplane/ngnsim.html  One of the many variables that you can play around with is HPC efficiency.  Note that as you decrease HPC efficiency, overall EPR is going to drop.  In a real engine, the controller will notice this and dump in more fuel to compensate and get back to the original EPR.  In this simulator, you will have to do that by adjusting the throttle controller.

Here's a screenshot of the engine simulator running.  The one on the left has a high compressor efficiency and the one on the right has a low compressor efficiency (note how i've changed the throttles and the different fuel flow).  Note how the temperatures on the right are all higher.  This a symptom of a less efficient component.  The engine has to work harder to generate the same thrust.  There are a number of other outputs.  You can also play around with other components, e.g. see how a degraded turbine efficiency looks versus a degraded compressor efficiency.

The only thing that this simulator does not have is rotor speed. For that, although I've not run out the calculations, I think that fan speed won't change too much with HPC efficiency, at least for a high bypass configuration.  Like I said, the control is going to change fuel flow to get back to the same thrust (via EPR), and since the majority of the thrust comes from the fan, the fan speed will be about the same.  The core speed, on the other hand, should go up.  Because the core has to work harder to produce the same amount of energy output.


Is an aborted landing considered an incident for the FAA? I was a passenger on a commercial aircraft on final approach into Salt Lake City. As we desended to approximately 1000' the pilot suddenly gunned the engine, climbed and aborted the landing. He then explained that the landing was aborted as there was another aircraft on our runway.

Is this a reportable incident to the FAA?

It depends.

There are two general situations.  One where the other aircraft was supposed to be on the runway and one where it was not.

In order to increase traffic density and keep the system working, aircraft do not wait for the aircraft landing in front of them to clear the runway or, in single runway fields, for the aircraft taking off in front of them to get airborne.  The separation distances and times are such that normally, the other aircraft will clear the runway but sometimes it doesn't work out.  A departing aircraft might have been given a clearance to take-off but doesn't respond quickly enough, or a landing aircraft might have a problem causing the pilot to stop on the runway to check it out or perhaps simply missing the turn-off they were supposed to take.

ATC might see this happening before the landing aircraft does and issue an instruction to "go around" or, the pilot might have seen that the runway was not clear and made the decision to do so.

This happens around the world dozens of times a day and is not reportable.  The system worked as designed and safety was not compromised.  It is most likely to be what happened in your case.

The other situation is where the other aircraft should not have been on the runway, called a "runway incursion". It might have been instructed to "hold short" of the runway but then entered it or might have mistaken the runway for a taxiway.

This is reportable. The captain has the authority and the duty to ensure that the runway is, or will be clear when they land and to abort the landing if not.  If the captain cannot be sure, they are required to go around rather than press on in the hope that it will be clear. Again, the system worked but safety margins were compromised and thus, the incident is reportable, both by ATC and the landing captain.  If it was a runway incursion, the crew causing it, assuming that they realise that they made a mistake, are also required to report it.

Although I've mentioned aircraft, there are many things that might not be authorised to be on the runway such as people, ground vehicles, animals, construction equipment etc.  Occasionally, pilots are attempting to land on the wrong runway, perhaps one closed for maintenance, and will go around when they see stuff on it.  These are all reportable.


When were the first jet engines used? I read a book about WW2 1 and saw a couple of planes with a giant jet engine on top of them, e.g. the Heinkel He 162 Salamander.

I realize jet engines had to have been invented before WW2 for that kind of technology to be used, so when were the first aircraft jet engines around?

1 Aircraft of World War II: 300 of the World's Greatest Aircraft. Chris Chant.

The first aircraft jet engine was ground tested by Frank Whittle in April 1937. In September of the same year, Hans von Ohain (ground) tested his jet engine.

The first jet aircraft, He 178 flew in August 1939.


Where can I find official definition of VFR and IFR? I know that ICAO Annex 2 'Rules of the air' states rules such as general rules, visual flight rules, instrument flight rules, etc. And aircraft should fly in accordance with either visual flight rules or instrument flight rules, and that is VFR and IFR. If aircraft fly in accordance with visual flight rules, that must be VFR.

But apart from these rigid rules, I image VFR as a flight that should fly with outside visual reference and have responsibility to avoid and separate with other obstacles or aircraft and IFR as a flight referring to instrument to avoid and be separated with other obstacles.

I tried to find more kind explanations(rather than ICAO ANNEX 2) about it like I stated above, but failed. Of course, I could find many documents or information like wikipedia, but there was no official source such as ICAO or FAA documents.

Could you give me some source that define VFR or IFR like as I stated above?

tl;dr The basic differences between IFR and VFR involve weather, required equipment, filing flight plans and getting a clearance, and the altitudes flown.

Your question indicates that you may not know that there is a difference between Visual Meteorological Conditions (VMC) and Visual Flight Rules (VFR). Likewise between Instrument Meteorological Conditions (IMC) and Instrument Flight Rules (IFR). You can be flying under Instrument Flight Rules in VMC—the airlines do this on most flights. It is not wise to fly VFR into IMC—a huge percentage of general aviation accidents happen because of that.

One source of the definitions is the FAA publication Pilot Controller Glossary, although they sort of presume you already know the concept.

INSTRUMENT FLIGHT RULES− Rules governing the procedures for conducting instrument flight. Also a term used by pilots and controllers to indicate type of flight plan.

INSTRUMENT FLIGHT RULES[ICAO]−A set of rules governing the conduct of flight under instrument meteorological conditions.

INSTRUMENT METEOROLOGICAL CONDITIONS− Meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling less than the minima specified for visual meteorological conditions.

VISUAL FLIGHT RULES− Rules that govern the procedures for conducting flight under visual conditions. The term “VFR” is also used in the United States to indicate weather conditions that are equal to or greater than minimum VFR requirements. In addition, it is used by pilots and controllers to indicate type of flight plan.

VISUAL METEOROLOGICAL CONDITIONS− Meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling equal to or better than specified minima.

The FARs only indirectly define IFR but you can get the rest of the definitions from the FARs.

  §1.1   General definitions.
  IFR conditions means weather conditions below the minimum for flight under visual flight rules.

  §91.155   Basic VFR weather minimums. (a) Except as provided in paragraph (b) of this section and §91.157, no person may operate an
  aircraft under VFR when the flight visibility is less, or at a
  distance from clouds that is less, than that prescribed for the
  corresponding altitude and class of airspace in the following table:

The table lists the visibility and clearance from clouds in different kinds of airspace that you need in order to fly under visual flight rules. If the weather is less than the minimums, then you need to fly under Instrument Flight Rules.

You can get an idea of the differences by reading CFR PART 91—GENERAL OPERATING AND FLIGHT RULES Subpart B—Flight Rules


What is this cylinder covered in threaded studs and what is it for? I can't figure out what this is.  It looks like each post is threaded, but why is a mystery to me.  My guesses include a grounding post, a bolt/nut testing stand that's not actually in an aircraft, or a super metal black box .
What is it and what does it do?

It's the inner liner of a heat muff, either for cabin or carb heat (you can see the engine mount tubes right next to it and that's exactly where I'd expect to see it, and the black pucks behind are part of a nose gear shock absorber).  It could be home-made, using threaded rod welded to the inner liner, or maybe it's a manufactured component with the rods swaged in place like rivets.
An outer shroud will go around it with inlet and outlet bosses for SCAT hose running to the air inlet and outlet to the cabin or carb.  Sometimes springs are wound around, or some other metal that can act like cooling fins; some builders just stuff the space with stainless steel wool.
The threaded rods are to improve heat transfer from the inner shroud to the air flowing past them (the threads maximize surface area).  There will be a flange out of view at each end that creates an enclosed annular chamber.  The inner shroud itself typically has internal baffling to function as a muffler for the exhaust.  Crude sketch of what I mean below.  My own plane has this kind of thing, but without the studs, just an open space.


What are these elements on the back of a Boeing 737? I forgot the model of that plane but I believe it's a 737.

I labeled each element for clarity.

What are they?

Click here for high-res.

① Main outflow valve door

(Source)

A valve used for controlling the pressure in the cabin. Air is pushed into the cabin by the air conditioning packs, and exits by this hole. The flow can be adjusted using a valve which is located behind this door.

(Source)

The valve opening is controlled by the pressure controller when the automatic mode is selected, and by the crew when the manual mode is selected.

The design of the door includes teeth to decrease the aerodynamic noise, by better mixing air from the cabin and air ram air.

For more details about the air system, see this answer.

② Safety pressure relief valve

(Source)

This is one of the two safety valve used in case the main valve mechanism is jammed or ineffective. It's like a safety pressure relief in a pressure-cooker.

It limits the pressure within the cabin below a maximum value, to prevent pressure to damage the cabin vessel and/or create discomfort for the passengers.

③ Drains

(Source: Question)

Unknown function drains. I believe they are used to evacuate flammable fluids leaking from the APU.

④ Tail-strike assembly:

(Source)

This tail-skid is used to limit the contact between the aft section of the fuselage and the runway. It absorbs some of the tail strike force. While I'm not sure for the B737, on other models (B757, B777) the tail-strike assembly contains a sensor to alert the crew of the strike occurrence, by displaying a message on the EICAS (thanks to @RalphJ for questioning).

(Source)

The intensity of tail strike force is registered by the color indicator. A force higher than the maximum permissible hides the green strip and requires a maintenance check before the next take-off.

This strip is checked during the pre-flight inspection (walk-around) to prevent flying with a possibly damaged aircraft.

⑤ APU drain mast.

(Source: Question)

Drains oil from the forward accessory and the compressor bearing of the APU.

⑥ Aft drain mast.

(Source: Question)

Heated drain mast, part of the water system, and used to evacuate water and waste from the aft galley and the lavatory wash basins ("gray water"). Schematics of the B737 NG water system:

(Source: B737 NG General Familiarization)


Does the AOA and G-Force increase if a fighter uses the afterburner during a max G level turn? My understanding is that if you apply power (increase the thrust) for a jet in level flight, it will momentarily pitch up, and then gain some speed.

So, if a fighter pilot lights their afterburner at a certain time when in a max-G level turn, does this further increase the achievable angle of attack and Gs, due to the increased thrust from afterburners helping to pitch the aircraft up, or does it just allow the max G-force to be sustained for longer?

TL;DR: Maybe.  Maybe not.  It depends on the particular fighter jet, and how it's loaded, and the effect will, in any case, be very small.

An increase in thrust causes an airplane to pitch up via two mechanisms (more details in this PDF):1

An increase in thrust causes an increase in speed; for airplanes with positive speed stability (which is true for all civil aircraft, but is often not true for newer fighter jets), this causes the airplane to pitch up and slow down.2  This changes the slope of the airplane's flightpath (making it point more up), but (at least at first approximation3) does not change its angle of attack.
If the thrust from the airplane's engines is not exactly aligned vertically with the airplane's center of mass, an increase in thrust will create a change in the airplane's pitching moment, which does change the airplane's attack angle; if the engines apply their thrust below the airplane's CoM (examples: 737, B-58), increasing thrust will pitch the airplane up to a higher AoA, whereas, if the engine thrust is applied above the CoM (examples: DC-9, Learjet 23) increasing thrust will pitch the airplane down, decreasing the AoA.  Most fighter jets have engines that are very close to the vertical location of the CoM, so the change in pitching moment from a thrust increase is very small, and its exact direction and magnitude will depend strongly on the specific aircraft and loading used (for instance, burning off fuel could change the vertical location of the airplane's center of mass - and, thus, the magnitude, and, possibly, even the direction, of the change in pitching moment caused by a thrust increase).

Thus, going from maximum dry thrust (no afterburners) to maximum thrust (with afterburners) could, depending on the aircraft, produce a slight increase in angle of attack and vertical4 load factor, but:

the effect would, at best, be quite small, and would depend strongly on the specifics of the aircraft and its loading;
with certain aircraft and/or under certain loading conditions, this effect could well be negative (in which case engaging afterburner would decrease the maximum achievable AoA and vertical load factor); and
the main effect would be (as you, in the latter part of your question, surmised could possibly be the case) to allow a high-G manoeuvre to be sustained for longer (due to the increased thrust helping to counter the high drag of a high-attack-angle manoeuvre).

1: For the purposes of this discussion, I am ignoring aircraft with thrust-vectoring capability.

2: Most airplanes will initially enter cyclic phugoid oscillations with anything other than a very slow, gradual thrust change, but the phugoid eventually damps out, and, even during the phugoid cycles, the "constant-attack-angle" part of the situation remains approximately true.

3: In practice, an airplane undergoing phugoid oscillations with a non-infinite period will undergo continual small changes in its attack angle, due to various damping effects, but the AoA does remain approximately constant.

4: Vertical from the aircraft's perspective, that is.


What is the freezing point of 100LL Avgas? Does anyone knows the exact freezing point of Avgas (100LL) ?

I found that Jet A-1 freezes at −47 °C / −53 °F (wikipedia), but didn't manage to find any info on Avgas.

ExxonMobil China says their Avgas 100LL will not freeze above -58°C.

The 'typical' freezing temperature is not given, but I would expect we'd be more interested in the maximum freezing temperature.


What is the appropriate fuel tank selection to land a 172? On a recent checkout on a C172 I was told to select "fullest tank" as opposed to "both" that I have been doing for years. Given the aircraft is high wing (gravity feed) with no auxiliary fuel pump there should be no chance of sucking air.

Anyone know the correct selection?

You should check your POH but it may just be that the instructor in question was recently flying a lot of Pipers and it was force of [bad] habit.

This POH for the 172S is in agreement with you.

  BEFORE LANDING

  ....

  Fuel Selector Valve -- BOTH.

You should consult the checklist in the POH that is with the airplane in question to be sure.


Which is longest Oceanic crossing for any commercial flight route? During oceanic crossings, there are limited to no terrestrial radio communications available, so I would think that most flight routes are designed to minimize ocean crossing time.

Which commercial flight route have the longest oceanic crossing?

For the longest  Oceanic Crossing, the following are the top three contenders:

Sydney to Vancouver
Melbourne to Los Angeles
Auckland to Vancouver

Out of this, 1 and 2 pass over a few islands on their way, 3 does not pass over any landmass.

Have a look at this : www.gcmap.com

Image :

(Image Source: www.gcmap.com)


Why can't horizontal stabilizers be longer than they are today? I've wondered this question because if the horizontal stabilizer is longer than that means more lift. My guess to this question would be the result of wing tip vortex strength on a longer wing

The horizontal stabilizers can be longer, they just don't need to be any longer than they are.

Each additional square inch will add induced drag and parasitic (form / profile) drag which costs fuel so they're not made any bigger than necessary to provide adequate control of the plane.


Is pilot alerted of any physical or structural failures? Current crew alerting system messages, I believe, are displayed basing on the software detection of the failures basing on the sensor information.

What kind of structural failures can occur to an aircraft in flight? (I know one case an engine got separated and communicated to pilot as just 'engine fail' instead of 'engine broken or something that might indicate a physical disconnect'). The had me wondering what other structural failures are possible when in flight. When I say structural failure, I am talking about a physical disconnect, bent, etc. Is there a (remote) chance that a structural failure can be caused in an airplane.
If at all a structural failure occurs in the middle of flight, is there any mechanism to let pilot know about it.

At the risk of sounding like a smartass, the alert is generally in the form of a loud BANG! or CRACK! followed, at best by different handling characteristics and increased wind noise/vibration, at worse, departure from controlled flight.


How to determine the RPM of the rotating shaft of an A320 PTU? The A320 PTU has an in-line variable displacement pump on one side and a bent-axis fixed displacement pump on the other connected directly by a shaft.
what would be needed to know how fast the shaft turns during PTU operation?

If you are not allowed to attach the measuring device to it, the two unobtrusive methods are by sound or by video.
Measuring by video would require the device to be visible, have some surface features to determine some particular rotation and the possibility to make probably video recording while in operation. The recorded video can be split into individual frames in the simplest case just estimating the rotation visually, as the time interval between the frames would be known. Otherwise, tools like OpenCV or fast.ai may help to analyse the images automatically. But these methods are limited by the number of frames per second you can capture. Most of the cameras would only do 30 frames per second or about but much faster cameras are available if you look on purpose. But the method can also capture slow or irregular movements.
Another approach is by sound - record the sound and plot the windowed spectrogram of recording. This can be done with less access possible, and work with higher frequencies, as long as the rotation sound is loud enough. Of course it will be a strong band from the engines on the spectrogram but it may fall far outside the reasonable frequency range of this "barking dog".


How to know that ADS-B position messages are not spaced more then the 1/2 zone limit? I am doing some ADS-B compact position reporting (CPR) decoding at the moment and one of the things that is described is;

"1/2 zone limit" from the last successfully decoded message.

I understand the reason behind it but how can we be sure that new message location is in 1/2 zone limit from the last decoded message?

Note : I am talking about local CPR decoding.

Usually you use a time limit between ADS-B position messages depending on the type of encoding used (surface or airborne)  and related assumed maximum speed to ensure that the aircraft cannot have travelled more than half a zone. If you don't receive a new position message within the time limit you will have to use global encoding (for which you need an odd/even pair of position messages within 10 seconds).

If I remember correctly, for airborne decoding an assumed maximum ground speed of 1000 knots is normally used. For surface decoding it is probably 200 knots. The latter gives problems when airborne aircraft send messages in surface format (e.g. due to a system fault).

In addition you can perform a number of tests that show that the newly decoded position is reasonably close to where it was to be expected.

For details see RTCA DO260B or EUROCAE ED102A (they are equivalent). They describe the encoding and decoding of (1090ES) ADS-B messages for airborne applications. In addition you can use EUROCAE ED129B. It is dedicated to ADS-B receiver systems for ATC (for gound based and space based receivers) and it includes a description of the decoding logic and related tests.


What causes air to move to combustor? I know the pressure is highest at end of compressor. But what forces air to move low to higher pressure? Am i missing out something? I have heard seals are used to prevent leakage of air from compressor to forward section of engine.

What forces air to move from lower to higher pressure?

In the compressor, the pressure continuously increases from first stage to last stage, that's the purpose of the whole thing. But your question is valid: Why would air move from the first stage to the second stage where the pressure is higher?
The reason is indeed the rotating blades of a stage push air to the next stage. Energy extracted by the turbines is used to rotate the compressor blades and create a relative wind. Air is accelerated over the blade and like for a wing, a downwash force is created. This accelerated air is then slowed down by the next stator vanes to convert the additional velocity into additional pressure, and maintain velocity nearly constant in the compressor (else efficiency would decrease), as visible in tsg's answer.
Stop the blades and air goes back until pressure equalizes in all stages.

I have heard seals are used to prevent leakage of air from compressor
to forward section of engine

Correct, there are seals. But while the air moves towards the combustor within the compressor annular duct, under the effect of blades rotation, seals are here to prevent it from getting back to previous stages by escaping the annular duct, and leaking below the stator vanes (between the rotor drums and the inner shrouds of the vanes).
The fixed vanes plane is actually the plane where pressure increase occurs. So air will try to return on the front side of the vanes, towards the rotor blades using the interstices (orange flow), but it will be blocked by seals.
The seals are highlighted in yellow on the picture below, they rub on the inner shroud of the stator vanes (actually for the engine shown, a honeycomb ring fixed inside the vanes shroud provides an abradable track to the labyrinth seal:

HP compressor interstage labyrinth seals (CFM56-7B), source
These seals are required because a small gap exists between the rotor and the stator platforms forming the inner wall of the duct.


Why was the WWII RAF fighter joy stick loop design not used widely? WWII RAF fighters had a loop on top of the joy stick in case of hand loss or injury - Anyone know why the Allies didn't copy this very helpful idea?

A control stick with a loop at the top was called a "Spade Stick".  Generally only Hurricanes and Spitfires had them.

The cockpits on these aircraft were small and it was a problem for the control column to get full travel for roll control. This was solved by making the control column rotate at about mid-stick instead of from the the floor.

Other aircraft didn't use them because the cockpits were large enough to accommodate a normal stick and still provide good leverage and side to side travel.

The loop was there so a pilot could use both hands on the stick to get more lateral force since the effective length of the stick was now much less than a conventional floor mounted control stick.

Pilots found them to be much more comfortable to hold and loop style sticks did also get used some on larger aircraft with conventional floor mounted control sticks.

Full right aileron


Why do countries not bound by US law comply with the FAA's originate airworthiness directives? I'm not an aviation or private international lawyer, but

is it true that countries unbound by US law, i.e. most if not all countries outside the US, still comply with the FAA's directives?

If so, is the cause merely political and/or public outcry and pressure? Doubtless non-Americans would be worried if their nation state's airline still flew airliners, Boeing or not, against the FAA's directives.

International air travel requires compatible laws at both ends, otherwise a plane might be grounded when it arrived. A web of international agreements therefore exists to implement globally the directives of the major national certificating authorities such as the American FAA and European EASA.
Some planes made in Russia and China are not able to fly internationally to any significant extent because they do not meet FAA or EASA standards. Others have been certified by these authorities and do frequent Western airports.
The agreements are voluntary. For example the Boeing 737 MAX scandal led many national authorities to reject the FAA's judgement to let it keep flying immediately after the second crash, and to make their own judgements when the FAA re-certifies it, while the EASA has been negotiating hard to ensure that the fixes are also compliant with EU standards.


How can I calculate the minimum thrust to weight ratio required for a given takeoff distance? I am building a plane and I have a take-off distance of 50ft, is there a way for me to estimate the thrust-to-weight ratio required for this constraint (even if it was in terms of say wing loading)?

Assuming you know the mass $m$ of the aircraft,  the speed $v_0$ required to take off and the lift and drag associated.
Using basic dynamic and newton's second law you can calculate the average acceleration $a$ required to reach take off speed before the end of your runway:
$$a=\frac{v_0^2}{100\text{ft}}$$
Then using your drag generated at takeoff to be on the safe side
$$\text{Thrust} = m * a + \text{Drag}$$
Implying,
$$\frac{\text{Thrust}}{m}=a+\frac{\text{Drag}}{m}$$


What is the correct procedure to deal with a TCAS RA during intercept? What is the correct procedure to follow if someone is intercepting you (or you are the F-16 driver intercepting someone else, for that matter) and you (or they, if you're the interceptor) get a TCAS RA in the middle of it all?  I'm thinking to cases like this situation where an interceptor may interpret the interceptee's TCAS-triggered maneuvers as signs of noncompliance with the intercept...yet the interceptor may not know just what prompted TCAS to issue the interceptee the RA, and the interceptee must comply lest it is an interloping third party on a collision course!

The correct procedure for the interceptee would to follow the TCAS Resolution Advisory as they have generally no idea that they are being intercepted.

The interceptor must ensure that no TCAS RA is generated by switching his transponder to the appropriate mode. This has been standard procedure since the introduction of TCAS.

TCAS works by interrogating other aircraft's transponders. These interrogations are done in both Mode 3/A and Mode C as well as in Mode S (UF-0). To ensure that no TCAS RA is generated the interceptor's transponder must not reply to Mode C and Mode S interrogations from the interceptee. Since the source of Mode C interrogations is not encoded in the interrogation, the transponder must not reply to any of these interrogations including those from radar.

Technically a transponder could be designed to selectively not reply to Mode S interrogations from the interceptee only, however I think it is common to switch off TCAS Mode-S replies, or even switch  off Mode S entirely.


What is the difference between MIL-H-5606 and MIL-PRF-5606 hydraulic fluid? what is the meaning of PRF here and can you differentiate them visually ?

About 25 years ago, there was a major effort to revise MIL standards and specifications.  The biggest change in MIL specs was to move away from a design or manufacture spec to a performance spec. The downside of the old specs were that they didn't allow for an improved product without getting the spec revised.  By switching to performance spec (what it must do as opposed to how to make it), improvements can be made without spec revisions and contract revisions (that call out the specs) ultimately saving everyone time and money while delivering products that use up to date technology.

In your case, MIL-H-5606 is the 'old' spec.  The H is taken from the primary application, in this case "Hydraulics".  The current spec is MIL-PRF-5606.  PRF is used to indicate a 'performance' specification.

'MIL-PRF' and other abbreviations are defined within DoD 4120.24-M, [2], Defense Standardization Program (DSP) Policies and Procedures, March 2000, OUSD (Acquisition, Technology and Logistics).


Why is horizontal stabilizer set to 4° up in airbus aircraft for take off? Why is horizontal stabilizer set to 4° up ( or any other setting other than neutral) in airbus aircraft for take off? Why can't we keep the trim neutral?

Both landing and take-off are critical phases of flight, and it is standard procedure to configure the aircraft for those phases to reduce the workload on the crew.

On landing, aircraft are configured for a stabilized approach, which means that the aircraft can be flown to the runway with a minimum of configuration changes to flaps/slats, trim, power, and drag devices.

On take-off, the aircraft is configured for take-off, and trim is set so as to provide a slight nose-up. If the trim is set nose low, it requires a lot of pull to "unstick" the aircraft from the runway. If the trim is set too nose high, then the aircraft will want to nose up before the aircraft may be ready to fly, and then to continue a nose-up attitude after rotation, requiring more than a minimal effort to keep the a proper departure attitude.

Nose-up trim can induce what is called a trim stall, which is when the trim is set so far back that the aircraft will exceed the critical angle on take-off:

  ELEVATOR TRIM STALL
  The elevator trim stall maneuver shows what can happen
  when full power is applied for a go-around and
  positive control of the airplane is not maintained.
  [Figure 4-8] Such a situation may occur during a
  go-around procedure from a normal landing approach
  or a simulated forced landing approach, or
  immediately after a takeoff. The objective of the
  demonstration is to show the importance of making
  smooth power applications, overcoming strong trim
  forces and maintaining positive control of the airplane
  to hold safe flight attitudes, and using proper and
  timely trim techniques.

  Source: Airplane Flying Handbook p. 4-10


What causes the horn-like noise during the start-up of some jet engines? Here's the specific sound I'm talking about (it starts specifically 56 seconds into the video, as well as at 2:02 for the second engine):

I've only really heard that sound on low-bypass engines (F/A-18s, BAE Hawks, etc); they don't occur right at engine-start (so as far as I'm aware it's not just bleed air being blown into a turbine for spin-up); I was thinking that it's perhaps either fuel flow causing an increase in exhaust flow through a slowly-moving turbine, or that it might be the hydraulic pump (or something similar) connected to the engine accessory drive.

Almost all jet engines will have one or more "resonance" conditions where the combination of turbine RPM, mechanical elasticity and aeroelasticity constructively reinforces to cause mechanical or aerodynamic vibration.
Think of it this way:  If you have a slinky spring (mechanically elastic) toy you can hold it by one end and let the rest drop freely below that.  Now if you move your hand up and down at different frequencies (up and down and back up again in 5 seconds, 4 seconds, 3 seconds, 2 seconds, 1 second, 1/2 second) you will find that there is one rate that will cause the most deflection/movement of the spring toy even though you are moving your hand through exactly the same distance. This is the one closest to its resonance.
Now the ductwork and spools of a gas turbine engine are just a little more complicated than our Slinky toy, but still a mechanical (in this case, aero-mechanical) system susceptible to resonance conditions.  The trick is to design the system so that these resonance conditions, which can be mechanically destructive, don't happen often or for very long.  As the turbine RPM increases through the resonance range things start to vibrate (in this case at ~250-275 Hz) wildly enough to create that extra sound.
In fact, the designers of that GE F414 engine could tell you exactly the RPM range where that happens.  The aviators and groundcrew are attune to the sounds of this machine and would likely shut things down and have a closer look if this particular phenomenon didn't happen as expected.
So, the horn-like noise is vibration of the mechanical parts of the engine ductwork and the air flowing through it for the short period of time that the engine RPM and airflow align to make this condition happen.


How are insects and arachnids kept out of commercial passenger airliners? If a commercial passenger airliner were to land in a place infested with insects or arachnids, wouldn't it be dangerous to have those animals enter the aircraft?

For example, suppose if mosquitoes, bees, or spiders were to enter the cockpit, wouldn't that be a huge distraction for the pilots? Wouldn't that potentially compromise the safety of the passengers?

The main questions are:

Are there established methods/protocols/regulations for ridding aircraft of potentially dangerous insects?
If so, what are they?

(Note: I am new to all of this. A thought occurred to me that mosquitoes onboard aircraft could potentially endanger the passengers onboard).

Like anywhere else, they only become a problem if they affect safety. That is why things like pitot probes and static ports are covered to prevent insects like  mud-daubers' from building their homes inside. Depending on the area it could only apply if the aircraft is not flying for x amount of time but in areas where these insects are very active it could be required for shorter transits. The recent Malaysia Airlines case (Brisbane, Aust) where the pitot-cover was not removed before flight was a case where the covers were place for a short transit because of these insect activity.

If the destination country has laws in place where the entry of non local insects is not tolerated they may require the airline to spray the holds before departure. I remember doing this for flights to Australia. We had cans with a 'lock' trigger (continues to spray without finger pressure) which we would activate and leave in the holds before closing the doors. It was important to notify the crews beforehand as the mist could activate the smoke detectors.


Which en-route services are available to UK GA pilots? I have recently taken up flying again in the UK, and although very little has changed in the 10 years I have been inactive, the one area which seems to have changed is in the en-route services available to pilots.

It used to be the case that you could request a Flight Information Service (FIS) and a Radar advisory (RA) service - I seem to recall there being one other which I never used, which I cannot quite remember the name of.

I believe the FIS is now referred to as a "Basic" service, is this assumption correct? Does it vary in any material way from the defunct FIS?

What other services are available to GA pilots in uncontrolled airspace? Where do I find the details of stations and what service(s) they provide?

According to UK AIP ENR 1.1 "General Rules", chapter 2 "UK Flight Information Services" the UK FIRs meet the ICAO requirements with the following Flight Information Services (FIS): Basic Service, Traffic Service, Deconfliction Service and Procedural Service.

This is an extract of the contents of the chapter:

  Basic Service
  Provides advice and information useful for the safe and efficient conduct of flights. This may include weather
  information, changes of serviceability of facilities, conditions at aerodromes, general airspace activity information, and any other
  information likely to affect safety. The avoidance of other traffic is solely the pilot's responsibility.

  Basic Service is available under IFR outside controlled airspace in any meteorological conditions, or under VFR. A pilot may change
  heading, route, or level without advising the controller. A controller will not issue specific heading instructions; however, generic
  navigational assistance may be provided on request.

  Traffic Service
  Traffic Service is a surveillance based ATS, where in addition to the provisions of a Basic Service, the controller provides specific
  surveillance derived traffic information to assist the pilot in avoiding other traffic. The avoidance of other traffic is solely the pilot's
  responsibility.
  Traffic Service is available under IFR outside controlled airspace in any meteorological conditions, or under VFR.

  Deconfliction Service
  A Deconfliction Service is a surveillance based ATS where, in addition to the provisions of a Basic Service, the controller provides
  specific surveillance derived traffic information and deconfliction advice.
  A Deconfliction Service shall only be provided to flights under IFR in Class G Airspace, irrespective of meteorological conditions.[...] A controller will provide traffic information, accompanied with a heading and/or level aimed at achieving a planned deconfliction minima.

  Procedural Service
  A Procedural Service is a non surveillance ATS where, in addition to the provisions of a Basic Service, the controller provides
  instructions, which if complied with, shall achieve deconfliction minima against other aircraft participating in the Procedural
  Service. Neither traffic information nor deconfliction advice can be passed with respect to unknown traffic. A Procedural Service shall only be provided to flights under IFR, irrespective of meteorological conditions. [...] the pilot remains wholly responsible for terrain clearance at all times. [...] A controller will provide deconfliction instructions by allocating levels, radials, tracks, routes, time restrictions, approach clearances and holding instructions, or use pilot position reports, aimed at achieving a planned deconfliction minima.


What does it mean when a runway's safety area is not standard? If an airport has a NOTAM that states that a runway safety area is not standard, what does that mean? Here's an example.

!CRW 12/043 CRW RWY 05/23 SAFETY AREA NOT STD 1512221324-1708151600

Is it something to do with the area on the ground that must be clear for takeoff and landing or some other criteria?

Here is a view of 05/23 at CRW:

Source: Google Maps

At either end of the runway there is a large drop off, here is another view:

Source: WVGazetteMail.com

(In March of 2015, the EMAS at the approach end of 05 was destroyed in a land slide as shown in the picture above, I cannot find a picture if it has been repaired, the NOTAM date indicates that it has not been.)

The FAA defines a Runway Safety Area (RSA):

  What is a runway safety area (RSA)?
  An RSA is a defined surface surrounding the runway prepared or suitable for reducing the risk of damage to airplanes in the event of an undershoot, overshoot, or excursion from the runway.

And has standard dimensions:

  The RSA is a rectangular box surrounding the runway and is based on the runway
  design code. The dimensions range from 120 feet to 500 feet in width and 240 feet to 1000 feet in length beyond the departure end of the runway. (see FAA Advisory Circular 150/5300-13, Airport Design)
  Generally, on airports that serve air carrier aircraft, the RSA extends 250 feet either side of the runway centerline and 1000 feet beyond each end of the runway.

So it doesn't look like there is a suitable area for an RSA given the size and expected traffic that the runway handles.


What is the required accuracy of an airspeed indicator? What FAA document specifies the accuracy to which an airspeed indicator must be calibrated to?

There are two standards, one for traditional pitot/static devices and one for air data computers.
Traditional A/S indicators are covered by TSO-C2d which references Society of Automotive Engineers, Inc., (SAE) Aerospace Standard (AS) 8019, "Airspeed Instruments", dated March 30, 1981.
Air data computers are covered by TSO-C106 which references SAE AS 8002, “Air Data Computer - Minimum Performance Standard,” dated October 30, 1981.
The SAE documents must be purchased.
Accuracy in the AS docs is not stated as a simple value. And as the system depends on installation, the aircraft level standards are applicable.
For traditional A/S indicators, repeatability is more important as installation can add errors. The aircraft manufacturer typically provides an IAS to CAS table in the POH. Since Part 23 aircraft rules have moved to a functional standard (e.g., it has to do its job well enough to be safe), there's no specified accuracy.
For Part 25 aircraft where air data computers are the norm, they must meet 14 CFR §25.1323 Airspeed indicating system.


What is this part between the Su-35's jet exhaust nozzles? What is the long thing that sticks out between the Su-35's jet exhaust nozzles and what does it do?

Source: 4ever.eu

The long thing has RWR (Radar warning Reciever) on its sides and has a drogue parachute in the middle. This image shows the rear part open after deployment.

Image from airplane-pictures.net

Incidentally, the aircraft serial number is 901, while the one in your image has a number 902.


Why is the missed-approach course for the "RNAV (GNSS) - A" approach to runway 28 at ENSB shaped all funny? Svalbard-Longyear (ENSB) has one particular approach (the RNAV (GNSS) - A approach to runway 28) whose missed-approach course is... oddly-shaped, to say the least:

(PDF by Avinor; screenshot and cropped by me.)

If the pilots can't see the runway by the time they reach SB709, they have to make a right-angle turn to the left just before reaching SB705, followed by a series of three right turns that end up with the aircraft aimed at NAXEN and its holding pattern (and flying directly over the substantial mountains immediately to the north of Adventfjorden en route).

The hockey-stick-shaped missed-approach course can't be for obstacle clearance, given that all this manoeuvring is carried out over the water - indeed, the other two approaches to runway 28 (the unadorned RNAV (GNSS) approach and the localiser approach) have missed-approach courses which each include but a single, wide, conventional turn en route to the holding patterns at the NAXEN waypoint and the Longyear NDB, respectively - so why does this particular approach have such a weird missed-approach course?

If you look at satellite imagery it looks like you have very high terrain to the west of the runway. The water would be the primary area available for a climb back to obstacle clearance altitude. Looks like the MAP just routes you with sufficient time to climb to the MA altitude.

(Google Maps)


Is there any way to reduce the noise and vibration in a C-130 Hercules? We are using C-130 B and E Models with T-56 A-15 engines and Hamilton Sundstrand 54H60-91/117 propellers. A lot of vibration and resonance are felt on these military version aircraft even after using solid state synchrophasing and conducting prop balancing.

I wanted to know if there is some system to make the aircraft quieter. Except for shutting down the engines of course :)

Are there any resonance controlling items to make the passengers more at ease?

Active vibration control systems exist for some aircraft, though I doubt an ex-military type would have anything off the shelf. There is a system from Lord (the engine mount people) that is intended to counter the vibration from a helicopter main rotor to improve passenger comfort, among other things. This is their claimed reduction:

AVCS Product Brochure

They focus on helicopters but sell components as well, and may be able to customize something that could work for you.


What would happen if the flight engineer is unavailable on a 747? Consider a 747-100/200 with a 3 person crew: two pilots and one flight engineer. During the flight, the flight engineer suffers a medical problem and is unable to serve duty for the rest of the flight.

What difficulties would the pilots face for the remainder of the flight, including navigation and landing, with no one attending the flight engineer station in the cockpit?

For example, would one of the pilots get up and sit at the FE station, leaving the other pilot the only person at the controls? Or would the person get up, go to the FE station to read or adjust something, then sit back at the pilot's seat? Or do they not have to move at all?

This question has been asked and answered in a slightly different form at How able were pilots of three-person cockpits at running the normal FE work?, and I refer you to that for basic info. Concerning the detail in your question:

  What difficulties would the pilots face for the remainder of the flight, including navigation and landing, with no one attending the flight engineer station in the cockpit?

It would be a nuisance for sure, but as long as there were no abnormal or emergency situations (other than the FE's personal situation), a nuisance would be all that it was. However, one could dream up scenarios that could get really sticky without the specialized knowledge that the FE would be expected to have that the pilots might not have (or had forgotten).

  For example, would one of the pilots get up and sit at the FE station, leaving the other pilot the only person at the controls? Or would the person get up, go to the FE station to read or adjust something, then sit back at the pilot's seat? Or do they not have to move at all?

The Captain can see the FE panel. Some of the gauges along the aft portion would be a little hard to read. For example, if he wanted to see what the exact pressure of the Potable water was rather than just that there was pressure, he might have to get up to get close enough. Or if a generator fault light came on, he'd probably have to get up to see what the fault was.

There wouldn't be any need to stay in the FE seat. If the flight were long, there would be some trips to the FE seat for fuel management. You can have as many as 9 fuel tanks (7 is the usual), and there are rules for the fuel burn schedule. The most important and most time consuming FE task during cruise was keeping track of what the fuel burn was, especially on the 747-100 because it didn't have the fuel capacity of the -200. For example, a -100 going from JFK to Tel Aviv would sometimes not have the fuel to make it. Abeam Athens the FE would inform the Captain either than they had the fuel to continue or that they would need to divert to Athens for fuel.

If the Captain wanted to talk to company for some reason, it was usually the FE that established contact via HF, and it was usually the FE that answered SELCALs. But the pilots sometimes did it.

Flight attendants might show up and ask for a general cabin temperature change.

Of course, it the FE had a severe medical problem, you would probably land at the nearest suitable airport just as you would for a passenger medical emergency.


Is there a list of CASA prohibited medications which would disqualify a pilot from flying or obtaining a Class 1 medical? Is there a list of medications which would disqualify a pilot from flying or obtaining a Class 1 medical?

Prior to having my medical I want to know if any medication I am likely to take will disqualify me, so that I can make enquiries about switching to an approved alternative.

A link to a list of prohibited or otherwise troublesome medications or similar online resource would be ideal.

There is no all-encompassing list of 'banned' medications publically available for Australia. In the regulations there is a 'catch all' to the effect of "pilots must not take any medications which may inhibit their ability to fly safely".

If you want specific advice on a specific medication, why not give CASA a call? That or you can see a DAME (which is a GP qualified to do aviation medical assessments).

What you can find out there is general advice though. Although questions such as this on ADHD and this more generally refer to the US system, the Australian restrictions are not too dissimilar.

Broardly speaking, Ritalin and other 'depressants' are incompatible with flying. Bi-polar disorder faces many restrictions but stable depression is manageable. I did hear somewhere that you need to be off antidepressants for 12 months though. Diabetes and blood thinning medications are OK but subject to regular testing and scrutiny.

As an aside, sometimes CASA, instead of outright refusing the medical, will place restrictions on it instead. This can be things like you must fly by day VFR only, or you can only fly with a qualified pilot next to you.

EDIT: I found this page from the CASA website which has a list of medications to stay away from. It's not exhaustive but it's a start


Do any aircraft systems give spoken warnings in a language other than English? Since pilots are permitted to communicate in their own language to eachother in the cockpit, and to ATC in their own country, it stands to reason that some warning systems like TCAS or TAWS/EGPWS might say "te laag, terrein!"

I've seen some Russian planes with everything written in Russian in the cockpit:

Do any aircraft have systems that give spoken warnings or callouts in languages other than English?

Are any planes built with the option to change the spoken language? E.g. an Airbus talking French?

I am quite sure that the systems that provide audio warnings for commercial aircraft, such as enhanced ground proximity warning computers, provide English Only. I am pretty sure because on the wiring diagrams there are no kind of dip-switches for language selection and for loadable software it is tightly regulated without any 'language selection' options.  One could imagine that separate part numbers are created for different languages but I know this is also not case case as international carriers share/pool spare black boxes. Basically aviation language is English.

I also see no future provision for other languages as it was only recently in 2008 that ICAO mandated English for all international flights (Amendment 164 to Annex 1 ). Under this ruling Air Traffic Controllers and Flight Crew Members engaged in or in contact with international flights must be proficient in the English language as a general spoken medium.

Regarding Airbus (and the love that the French have of their language) we might do well to know that actual official language of the Airbus company is surprisingly to some 'English.'

Of course I can't comment on military applications much. Actually, I was previously slightly involved in supporting a military aircraft and from what I can tell they use many modified versions of the same components commercial aircraft do. At least for US, British or French allies, who are allowed to import the technology. However, they are modified directly by the customer to be more security tolerant. For example, a military aircraft might not be transmitting its location around the globe unless the receiver has a decoding ability to a secure military key. So even in the small exposure I have encountered with military applications, I have not encountered or heard of 'language options.'  This is not to say that some Chinese or Russian might be heard in some remote aviation system somewhere but that if it does outside their aerospace industries it must be rare and still a 'one language' only feature. Possibly there are missile guidance systems in Russian, Chinese, or Korean but certainly not in international commercial aviation.


Do aircraft weigh less on an eastward flight than a westward flight, due to the Eötvös effect? Aircraft speed is added to earth rotational speed when flying to the east, centrifugal force is increased compared to a westward flight. That means the aircraft weight is reduced = smaller lift, means flight with lower AoA = lower induced drag.
Can this in reality be used for less drag and greater speed or better fuel consumption?
If a plane flies east with speed of 1666km/h, centrifugal acceleration is 0.134m/s2, that means it has 1.37% less weight. If the plane weighs 78700 kg then the reduction in weight is 1078kg, when flying east!
If a plane flies westward at 1666km/h (same as earth's rotational speed) then looking from space (inertial frame) plane looks stationary, so centripetal force = zero.
This is the Eötvös effect:

Technically yes. But as Jeffrey said, it's quite negligible. We can do the math knowing that the earth rotational speed is $360°$ per $24h$, you get $0.004°$ per second or $\omega =  7.27 \cdot 10^{-5} rad/s$. We can then calculate the centrifugal acceleration related to this speed assuming the earth radius is $r=6371km$ and neglecting flight altitude.
$$a_c = \omega^2 r= 0.0337m/s^2$$
So if you're flying at a relative ground speed equal to the earth rotation, your centrifugal acceleration is either $0$ or $0.134m/s^2$ depending on which direction you are flying. Compare that to the gravitational acceleration $g=9.81m/s^2$ and you get $1.37\%$ of weight difference flying at Mach 1.5 with the earth rotation or against it.
Now remember that to have your weight reduced you need to fly with the earth rotation which means eastwards. And there you get a somewhat bigger problem reducing your performances in flight. Jet stream. Jet stream magnitude can be up to several hundreds of kilometer per hour meaning reduced ground speed around 10% are quite usual, resulting in 10% increase of flight time and fuel consumption thus destroying any opportunity to notice the 1.37% reduction of lift you're getting by flying east.
And even less useful when you know that the concorde used 2 tons of fuel to taxi from gate to Runway and 50 more tons to reach cruise speed and altitude in less than 45min....


Can you tell ATC you are a "student pilot" when you are not? Many pilots who are not native English speakers have a hard time when they start flying in the U.S. because of the pace and sometimes elaborate instructions given to pilots by controllers.

The advice given by instructors is to tell the controller that you're a student pilot, even though you may be a fully licensed (private) pilot. The effect should be that the controller will be more lenient towards the pilot and speak slower.

I would first of all like to know if it is legal to tell a controller that you're a student pilot even if you're not (I know, all pilots should see themselves as students for the rest of their life, but that's another topic).

Also, isn't there a chance that you'd get refused entry in class B airspace because you're announcing that you're a student pilot?

It's a bad idea to give false information to a controller as a matter of practice. Instead of calling yourself a student when you're not, it would be better to say you're unfamiliar with the area or that your English is not perfect.

Controllers are almost always accommodating to less-than-proficient pilots and will usually make allowances whenever time and traffic permits.

If your English is not good, be sure and use simple, direct phraseology. Read the AIM to become familiar with the common phrases used with ATC. Even something as simple as hearing "radar identified" in Canada instead of the usual U.S. phrase "radar contact" has caused many a native English speaker to reply "say again?"


What triggers the trim horn and the "stabilizer motion" aural callout on the MD80? I got conflicting or incomplete responses from various sources:

  There is an internal rate monitor looking to see the stabilizer is
  actually moving .08°/sec or -08°/sec.

https://forums.tfdidesign.com/index.php?/topic/2509-bbetty-stabilizer-motion-warning/

  The trim horn will sound each 1/2 degree of constant pilot use, but
  the stabilizer motion call will sound when the auto pilot moves the
  trim 2 degrees within 30 seconds.

https://forums.x-plane.org/index.php?/forums/topic/123539-cockpit-sounds/

  The CAWS will provide an aural warning (tone and voice) when the
  horizontal stabilizer deviates one degree or more for a given length
  of time. The warning will be on until the horizontal stabilizer sensor
  goes off.

https://www.airliners.net/forum/viewtopic.php?t=751253

Which one is correct?

There are two aural sounds, the horn, and the voice callout "stabilizer motion".

The horn sounds every 0.5° of trim change after the initial 0.5–1°.
"Stabilizer motion" sounds when the autopilot or runaway trim motor make a >2° in 30 seconds.

So your second source is the correct one. See text below from an MD-80 flight manual:

  Momentary horn sound starts after 0.5º to 1.0º of stabilizer movement and repeats every 0.5º of stabilizer movement . "STABILIZER MOTION" voice warnings will sound when either the autopilot or a runaway trim motor moves the stabilizer more than 2º in 30 seconds and will continue to sound as long as stabilizer moves. Cycle continues until stabilizer movement ceases. (Manual page)

Note that it also says:

  Vocal warning on some aircraft, other aircraft no vocal warning.

So not all MD-80s have the voice saying "stabilizer motion".


Is there any website which is offering free real time tracking data of flights? Our customer always demand, and I think there is huge market of, live tracking data. We need to ease either our customers or their relatives that they have reached their destination safely. So as I was moving around, I found out that there are too many live data APIs, but I want to integrate the free live API in order to check first. Can any one give me options that provide live APIs? Also if I need to get ADS-B what can I do and how does it work?

There are numerous web sites that provide flight tracking data, including radar and ADS-B. Most are free for personal use, but AFAIK all of them charge for commercial use. This makes sense since collecting and aggregating that data takes a lot of time, effort and equipment, and they have to recover those costs somehow. Still, using an existing service should be a lot less expensive than trying to set up your own redundant operation just for your own needs.

The sole exception is if you're trying to track ADS-B flights in the vicinity of your own facility, in which case you can easily set up a single ADS-B receiver there. But most folks want a (much) bigger picture, including non-ADS-B traffic, so please clarify the scope of your needs.


What is this "No Hand Hold" thing in the P-51 Mustang cockpit? Does Anybody remember Combat Flight Simulator WW2 Europe Series ?
In the P-51, there is a "something" with "No hand hold" text on top of it
What is that ?
Image source

It is part of the gyroscopic gun sight:

Source: WarRelics Forum

It is not a "hand hold" because you don't want to damage the sight by grabbing the scope to situate yourself in the cockpit (getting in/out) or otherwise pulling on it. Since it is aligned to your guns, you would want to avoid misaligning it.


Is AMS (Schiphol) Polderbaan the runway furthest away? I'm very interested to learn if there are (m)any (major) (commercial) airports that have runways further away from the terminal(s) than Schiphol's Polderbaan. Which airport is "in the lead" in this respect?

The northern end of the Polderbaan, the last runway to be constructed, is 7 km (4.3 mi) north of the control tower, causing taxi times of up to 20 minutes to the terminal.
[...]
Newest runway, opened 2003.
Located to reduce the noise impact on the surrounding population; aircraft have a lengthy 15-minute taxi to and from the Terminal.

Wikipedia

One possible contender is Pyongyang airport. The far end of the new runway (01/19) is around 7 km away from the terminal (as the crow flies). With taxi distance, it is almost 8 km:

Source

While the taxi times at Amsterdam can be very long, it is a bit misleading to blame it on the runway being 7 km away. Runway 18R is not used for takeoff. Unlike Pyongyang, there is no parallel taxiway on that 'end' of the runway, and Schiphol ATC would never want to wait for an aircraft to backtrack. Hence, it would be more sensible to use the distance from the first taxiway for landing aircraft on 18R, located 5.5 km from the tower.


Where is the fuel vent on a Piper Archer TX? I realized I haven't really noticed where the fuel vent is for the 2016 Piper Archer TX that I've flown, but I assume the fuel is vented from the fuel cap. Is that correct?

There are four main tank vents on all PA28 (Cherokee/Warrior/Archer/Dakota/Arrow) aircraft, two in each tank.

The most visible vent is under the wing at the outboard aft side of the fuel tank (near the jack points):

This vent is a small tube that protrudes from the bottom of the wing and is cut at an angle facing forward to provide ram air pressure into the tank. It is the vent you typically check during preflight to ensure mud wasps or similar haven't built a nest in the conveniently bug-sized tube.

The second vent is located in the fuel cap: It is an orange rubber "umbrella" in the center of the fuel cap which covers breather holes.

If pressure in the tank becomes negative (because the under-wing vent is obstructed) the umbrella will be forced open by air pressure and allow air into the tank through the fuel cap.
This vent is not normally "checked" during preflight except to ensure that the rubber umbrella is in fact there. A failure of the rubber "umbrella" is one common way that water finds its way into the fuel tank (the other being a failure of the O-ring around the perimeter of the cap).


Do I get two different certificate cards if I earn both a pilot and an instructor certificate in the US? I would like to know if one will be receiving two separate licenses in case he/she earns a pilot certificate as well as a ground instructor certificate in the US.

Do the certificates come separately on two different plastic cards? If yes, does the certificate number change between them, or do they have the same number?

Yes.. The certificate number will not change.  The flight instructor certificate includes CFI at the end of your number.

  §61.5   Certificates and ratings issued under this part.
  (a) The following certificates are issued under this part to an applicant who satisfactorily accomplishes the training and certification requirements for the certificate sought:

  (1) Pilot certificates

  (2) Flight instructor certificates.

  (3) Ground instructor certificates.

Part 63 provides guidances on flight engineer and flight navigator certificates.

Part 65 provides guidance for ATC tower personnel, mechanics, repairman, parachute riggers, and dispatcher certificates.


Are there any widely applicable models for plausible aircraft auto-routing? Aircraft travel in well defined airways, at different flight levels depending on direction and also have specific rates of ascend, descend and turn (e.g 2-min turn).

Are there any known models that take these spatial constraints into account and produce a plausible route between two points in space for a given aircraft?

My specific use case is straightforward: I have the current position of an aircraft and a number of alternative endpoints on that route. Instead of drawing straight lines between these alternatives, I would like to draw plausible routes taking into account as many real constraints as it is possible.

I haven't look into how this is implemented in computer games yet (e.g. flightgear) and I could write a simple enough auto-router taking into account the rate constraints. I would however like to know if there are any widely accepted or recommended existing auto-routing models.

Additional Information

In view of comments to this question I would like to clarify the following:

I am not looking for flight-planning algorithms or constrained
routing in the sense of optimal paths that are sometimes sought by
algorithms such as those used in this paper.
I am looking for routing algorithms whose output is the actual path
that if set on an autopilot will bring the aircraft through an
endpoint at a specific bearing, level and speed. Ideally, I am
looking for "names" in the same sense that the paper linked above
states "...some auto-routers for military aircraft do exist including
CLOAR, OPUS and JRAPS...".
As a secondary question, do ATC systems have some sort of
auto-routing as an aid to operators at busy areas? If yes, then
perhaps it would be worth checking if the algorithms are published
because I expect they would have to be standardised and validated.
As an example, consider an aircraft that is approaching an airport to
land. The aircraft is on a specific course, flight level and speed
and it is to be directed to enter the landing pattern at a specific
point. An approach would be to extend the entry point's bearing and
aircraft's bearing and fit a cycle that corresponds to the 2-min turn
to bring the course of the aircraft on the entry point bearing (i.e.
smooth the corner of the intersection). If such an intersection is
undefined (e.g. the bearings are parallel, or they intersect at a
really long distance) then a new leg needs to be added which a)
intersects with the current course of the aircraft b) intersects the
entry point bearing and c) satisfies other constraint (e.g. shortest
distance, no sharp angles, etc). If that is undefined on the side of
the entry point a new leg must be added, this leg should a) intersect the given leg at...and so on.
This approach will result to a path (not THE path) that respects specific
constraints...But obviously the question here is how realistic it
will be both for an aircraft to fly but also would a human operator
produce a path with similar qualities or reject it altogether? Hence,
the question...are there any auto-router algorithms out there
already?

Edit

If the general consensus veers more towards a situation where it is very hard to get acurate information on routing models for civilian aircraft, is there a set of minimal parameters that would have to be taken into account when designing a simplistic auto-router that would be more likely to generate plausible paths given two points in space? "Plausible" is defined as "similar to what a human ATC would have directed the airplane to do" or "a path that appears sensible to an average pilot". At the moment I would be considering the rates of ascend, descend and turn.

I am looking for routing algorithms whose output is the actual path that if set on an autopilot will bring the aircraft through an endpoint at a specific bearing, level and speed

There are indeed models for moving between waypoints: I remember siting on the flightdeck of an A320 and noticing the airspeed increase as we descended towards the airport. I asked the pilot and he responded that this was in preparation for a turn coming up as to not loose airspeed. Not a huge differences perhaps but will make a difference over a year with a lot of aircraft.

Most airlines have company routes detailing which waypoints to use to a destination. To the best of my knowledge, these are fairly standard (you might have  few) and not too weather dependant, unless there is a big storm for instance. One exception to this are transatlantic tracks that are changed daily depending on weather. At least for most flights, possible variations are few and will be in busy airways. Changing airways is normally a larger deviation so it is just good to bare with it, and the weather is unlikely to be considerably better for just a slight detour.

  As a secondary question, do ATC systems have some sort of auto-routing as an aid to operators at busy areas?

ATC have normally no real incentive to cut down routes, at least in cruise. They might help you skip some waypoints and get the aircraft down a little quicker if the airspace is calm during arrival. To also put things into perspective, I was on the flightdeck into a moderately large european airport where we were put first into a hold due to bad planning and then told to speed up after we left it to catch up again. Arlanda airport had something going on however with green approaches.

  I am looking for routing algorithms whose output is the actual path that if set on an autopilot will bring the aircraft through an endpoint at a specific bearing, level and speed.

The issue here is that there is no incentive for aircraft manufacturers to release such algorithms to the public. If Airbus uses algorithm A, and Boeing algorithm B, each with a different inputs, you neither would want the other to make algorithm C that works with both inputs and being more efficient. The bottom line however is that everybody remains constrained by the infrastructure already in place that is pretty rigid.


Why some planes are scrapped way sooner than others? I am browsing the planespotters.net database, and I see plenty of planes in their twenties. Delta, for example, has 117 MD-88 with an average age of 25 years.

While other planes are scrapped with no apparent reason when they are not even 10 years old: when Malev went bust, all its B736s were scrapped, 6 planes that were around 8 years old. https://www.planespotters.net/production-list/search?fleet=Malev-Hungarian-Airlines&manufacturer=Boeing&subtype=737-600&fleetStatus=historic

This is not the only example, there are plenty of aircrafts not older than 15 years that are scrapped, while other planes are still flying in the late twenties.

What are the reasons?

In general, the retirement age of aircraft is around 25 years and most of the aircraft fleet in operation is well over 15 years old.

Source: airfinancejournal.com

There are various reasons for scrapping the aircrafts rather than selling them to other airlines (or other buyers, in general).

Availability of Buyers- People should be ready to buy the aircraft on offer. In this case, the aircrafts were probably offered for sale at a time when tn the economy was in a bad shape and the airlines would've found it difficult to sell them.
Condition of the aircraft- Though the aircraft may be new, it has to be seen if it is properly maintained. In case the aircraft are not maintained properly or had the parts been cannibalized for spares, it would be difficult to find buyers as it takes a lot of money to put the aircraft back into operation.
Sum of Parts- In some cases, the sum of parts of the aircraft may be more valuable than the aircraft itself. Cost of operating an aircraft is quite high and the aircraft parts like engines etc are quite valuable. It would've made more economic sense to scrap the aircraft and sell the parts rather than (trying to) sell the aircraft itself.


Can you please identify this aircraft from a BBC show? The image is from:  BBC Skies Above Britain Series 1 "Flying into Danger" - Episode 1

Although a little hard to read, the reg is F-BXCP which you can find with a search
https://www.airport-data.com/aircraft/F-BXCP.html
The aircraft is a Max Holste MH.1521 Broussard which is a 1950's era aircraft originally built for the French airforce.
Somewhat interestingly that aircraft is now registered G-HOUR and is owned by the luxury watchmaker "Bremont" (hence the reg). It seems to have first got a reg-change with the same paint scheme and then latterly been repainted.


Why do these tail-sitters not have bigger propellers in their main engine? My attention was called to tail-sitter aircraft, like these two:

Convair XFV Pogo By No information - US Navy, Public Domain, Link

Lockheed XFV 1 Public Domain, Link

These aircraft land on their tails but transition to normal flight during cruise.

But what I want to know is, why are the propellers so small? Disk loading is a big part of efficiency. That's one reason why helicopter blades are so big. It is more efficient to accelerate a large mass of air to a slower velocity than a small mass of air to a faster velocity.

As far as I know, the disk loading factor is valid for propellers in horizontal cruising too.

So why aren't the propellers any bigger? They have plenty of room at the nose. No worries about ground clearance. I would think for a helicopter-like takeoff, this puts a lot more strain on the engine and thus efficiency would be even more important than usual.

You're correct that it is more efficient to accelerate a large mass of air to a slower velocity. But then there are other things to consider here:

The attitude control i.e. transition is based on the downwash generated by the propellers (unlike helicopters). Either you should have high speed downwash or reach higher speeds for the flight controls to become operative. Reaching higher speeds in vertical flight would tax the engines further and the higher speed propellers, however less efficient would have been the better choice.
Huge rotors, like in helicopters would've been efficient, but also bring the related problems of blade flapping, lead and lag and droop, especially leading to problems during transition. There are also issues with tip speed, especially for the high speed interceptor role these aircraft were intended for.
One of the design considerations was shipboard (even submarines were talked about) use, conditions in which higher diameter rotors would've been a headache- you have to find ways to fold them, for one.

In the end, use of smaller rotors would've been influenced by a much more mundane reason- availability of powerful engine. Note that both of these aircraft were powered by variants of the same engine- modified Allison T40 turboprops, the only engine rated for vertical takeoffs and landings available- which consisted of two Allison T38s lashed together to run the same gearbox with contra-rotating propellers.

In fact, the heavier Lockheed XFV never made the transition flight, waiting for a higher powered T-40 and did only horizontal flights with long landing gears (which would've precluded using higher diameter rotors- though I'm not sure if that was a consideration).


Why are the spoilers used as the backup controls instead of ailerons on the Boeing 777? While reading this question, I ran across an interesting unanswered comment.  Why did Boeing choose to use some of the spoilers as mechanical backup controls rather than the ailerons?

The B777 is a high subsonic aeroplane, and at high airspeeds the ailerons remain stationary because wing twist may cause aileron reversal.

By using inboard spoilers as mechanical backup roll control surfaces, there is roll control available at high airspeeds as well. Roll authority would be limited at approach speeds due to the smaller moment arm than the aileron provide and due to negative lift on one side only.


Why does a missile have small wings but better agility than a plane? An anti air missile has often very small wings but out performs a fighter aircraft, e.g. much higher g-load, since g-load comes from lift which is the area of wing.

Why not designing an aircraft like a missile? E.g. low drag, high agility.

First of all, a missile is operating at a much higher dynamic pressure than the airplane. After all, it has to catch up with it to do its job. Since dynamic pressure scales with the square of airspeed, the wings of a missile twice as fast as the target would need only a quarter of the wing area to produce the same forces.

Secondly, the missile uses its thrust just as much as the lift from its vanes to change direction in the initial flight phase when the rocket motor runs and the biggest course changes are needed. With an airplane, this is normally not possible, since most planes need to fly in a small range of angles of attack and sideslips to operate properly. Exceeding those will produce substantially more drag and might lead to loss of control.

Lastly, the missile has to carry only the mass for a few seconds of flight. The burning time of a rocket motor is just a few seconds for short-range missiles, and their typical flight time is about 30 seconds. Since they do not need to carry the fuel to return to base, their mass can be held down, which improves agility.


Procedure for simulating nonlinear flight dynamics I am trying to simulate F/A-18 Hornet on Simulink. So, here is how I have made the model:

Firstly, the initial flight parameters(Alpha, beta, V(magnitude), rho) are being calculated based on the initial values of the states.
Then, these parameters, along with initial values of the states, are used for calculating the aerodynamic forces and moments.
As the Aerodynamic forces and moments are in the Wind Axes, I transformed them from Wind to Body using alpha and beta.
Then, the gravity force, which is transformed from the NED Frame to Body frame, is added to the transformed aerodynamic force.
Similarly, the thrust force is added, assuming that thrust is only in the X-direction( Body Frame), and no moment is generated because of it.
Then, total force and moment are sent into the Body Axes 6-DOF Quaternion Block present in Simulink, which gives me the states for the next iteration and process continues.

Please point any mistakes you find out in the above-mentioned iteration process. Now, for checking if the model is correct or not, I planned to give initial conditions as a trim condition, and if the model is correct, the plane should fly in the stable level flight. The trim point is:

 V = 300.92 ft/s
 [phi, theta, psi] (in rads) = [0, 0.1745, 0] (pitch is 10 degrees)
 [p, q, r] = [0, 0, 0]
 alpha = 0.1745;
 beta = 0;

On giving these initial conditions, the plane flys at a stable level flight. So, is this process of verifying the model enough? If not, then please outline the process which I can use to check my model. Thanks for the help!

PS: Reference for the Aerodynamic Model of FA-18 Hornet:- A. Chakraborty, P. Seiler, and G. J. Balas, “Susceptibility of f/a-18 flight controllers to the falling-leaf mode: Linear analysis,” Journal of guidance, control, and dynamics, vol. 34, no. 1, pp. 57–72, 2011.

I am not a flight dynamics expert, but let me give an extremely general answer on verification of a non-linear dynamic system.  consider that you have the non-linear system $\dot x =f(x)$.

This system may have multiple equilibrium points, which are the $x$ values such that $f(x)=0$.  You have checked that one of the desired equilibrium points is actually an equilibrium point in your simulation. So that's good.  But does your system have more than one equilbrium point?  if so, you probably want to check all of them.

Next, you want to check the stability of the equilibrium points.  You've checked that $f(x)=0$ for one equilibrium point.  You need to check what happens for a small perturbation say $x_0= x+\epsilon$.  If the equilbrium point is supposed to be stable, then you need to check that after some time, the system has returned to equilibrium.  If the equilbrium point is supposed to be unstable, you need to check that the system has diverged from the equilbrium point.

But even that is not good enough.  You also need to check the rates of convergence or divergence.  i.e. near the equilbrium point, you can linearize the system and find the eigenvalues.  i.e. if you are at a small perturbation away from a stable equililbrium, you expect the system to approach equilibrium at a certain rate, say $x=x_0 e^{-\lambda t}$.  You need to verify that the simulation matches the expected rate.

So to summarize, you need to verify that your simulation has the correct number of equilibrium points, that the stability of each equilbrium point is correct, and that the eigenvalues near each equilbrium point are correct.


What regulations in the US exist for jetpacks? In 2010 Fox News posted an article in which they quoted a representative of the FAA saying that the FAA might not regulate jetpacks (the representative did say that they could fall under Part 103). Do any regulations exist in the US for jetpacks?

This depends on what you mean by a "jetpack". If you mean the classic James Bond-style rocket pack, then according to an FAA spokesman quoted in the Wall Street Journal they just don't fly long enough for the FAA to be interested:

  Once aloft, a jetpack pilot is preoccupied with getting down quickly:
  A typical pack holds about 10 gallons of fuel, only enough to fly for
  about half a minute. The Federal Aviation Administration doesn't
  regulate jetpacks. "Thirty seconds is not sufficient to be considered
  a flight," says FAA spokesman Les Dorr. He adds that it's up to the
  individual to assess the risks.

On the other hand if you're referring to the Martin Jetpack, which uses fans instead of rockets, then several sources (e.g. Wikipedia) say that it's considered an ultralight by the FAA, in which case all the usual ultralight regulations would apply. But I couldn't find any direct confirmation of that on Martin's site.


What general aviation operators might hire a low time pilot? I recently obtained my CPL at FTA.
In one of the answers:

The normal progression is this - you can technically get a flying job after 150-200 hours of private training and flying, having achieved your commercial pilot licence (CPL). I say 'technically' because if you only have minimum hours and minimum qualifications you have to look very hard for a job. Most people straight away get an instructor rating, so they can get a job teaching people to fly. Other early jobs include sightseeing flights, parachute flights, and mail flights to remote towns.
Your training will have been in light aircraft, but fortunately Australia has possibly the largest light aircraft industry in the world, so there's lots of jobs in these planes. It's highly unlikely that your first job will be in anything bigger than a 6 seater plane.

Could somebody suggest based on your experience, light aircraft operators willing to hire a 250 hours pilot?
I already sent my resume to a list of GA operators and did not receive any reply. I need some advice on the best approach when trying to get my first job.
Look forward to hearing from you.

Getting your instructor certificate is your best bet.

Beyond that, there are jobs out there for traffic watch, banner towing, and flying jump planes for skydivers.  Also glider towing and sightseeing.  Ferry flying is possible, although I'd be careful of any place that would hire you with very few hours -- they may be cutting corners & guys with more time look at the operation & say "no thanks."  Not necessarily, but be cautious with anything that looks "too good to be true."

All of these are typically positions that only have a few, or one, or no openings at a time, and those spots are in pretty high demand.  So persistence and personal contact (not just sending a resume) are probably vital to landing one of these jobs.  The place where you're most likely to have more options is flight instructing; obviously that requires the CFI certificate (or equivalent for outside the US).

Good luck!