What is the procedure to fill/send/approve a flight plan to the ATS network from outside? We are planning to develop an app that allows general pilots to fill/send a flight plan to the ATS. We're wondering to know if it is needed to have a regular access (register access or account) to the ATS network (thru AMHS or other way).

The idea is to automate the process through an app for general pilots.

For example, Garmin Pilot's app works and offers same solution., among many other related solutions for pilots.

Using EUROCONTROLs „business-to-business web services“ you can file and manage flight Plans (including IFPS validation) as well as check details about the filed flights e.g. departure and arrival messages or where the aircraft is currently.

After a registration (you have to proof you are eligible to use the service) you do not need any ATFM connection at all - you implement the API features of B2B services into your app and that‘s it.

For more details and the conditions check: https://www.eurocontrol.int/service/network-manager-business-business-b2b-web-services


Did I identify these aircraft correctly? I photographed a couple of aircraft and tried to identify them, but I'm not sure if it's correct. For me, all of them look like an Airbus A320, but I'm really unsure. So which of these aircraft is an Airbus A320 and if not, what's the correct type?

Airbus A320?

Airbus A320?

Airbus A320?

Airbus A320?

Looks like it :)

Double window exits over the wings, so no A321 or A319 (with a few exceptions such as Easyjet's A319)


What is the correct procedure for operating the engine fire extinguishers on an ATR72? I am developing an application for airport fire crew and ground staff. Part of the application is to familiarize users with emergency procedures of various aircraft. I have a few questions about the procedure for discharging the engine fire extinguishers on an ATR72 that I hope someone can help me with:

As I understand it, pilot must pull the red handle and twist 90 degrees. This will stop the engine. Pilot must then press the discharge squib button in order to deploy the extinguishers. is this correct?
What would happen if the pilot pressed the discharge squib button before pulling the red handle?
Am I correct in assuming that if the system has detected an engine fire, then the "fault off" buttons would be lit and there would be an audible alarm? If this is the case, would the alarm stop when the discharge squib button is pressed, or only when the fault off button is pressed?
Above the buttons it is written: "Agent 1 Loop A" and "Loop B Agent 2". what does this mean and what is the difference between the two systems? In what circumstances would the pilot have to press both discharge squib buttons or both fault off buttons? In what circumstances would they only have to press one?

As I understand it, pilot must pull the red handle and twist 90 degrees. This will stop the engine. Pilot must then press the discharge squib button in order to deploy the extinguishers. is this correct?

Yes, this is correct, except that the handle does not need to be twisted as far as I know. When the handle is pulled, the following things will happen:

The propeller on this side is feathered.
The fuel LP (low pressure) valve is closed.
The bleed air and HP valves are closed.
The deice and shutoff valve is closed.
The DC and ACW generators are disconnected.
The hydraulic to prop brake is closed on the other engine.

Pressing the squib button will then discharge the extinguishing bottle into the engine.

What would happen if the pilot pressed the discharge squib button before pulling the red handle?

Nothing, the button is not armed at this stage:

AGENT/SQUIB
armed when T handle pulled.
Discharges bottle.
(DC EMER/HOT MAIN BAT)

Am I correct in assuming that if the system has detected an engine fire, then the "fault off" buttons would be lit and there would be an audible alarm? If this is the case, would the alarm stop when the discharge squib button is pressed, or only when the fault off button is pressed?

Yes, both FAULT lights would be on and the alarm is triggered, if both loops A and B detect the fire:

The pilots would be alerted of the fire by:

master WARNING light flashes
ENG 1/2 FIRE light illuminates on the CAP (Crew Alerting Panel)
FUEL SO illuminates on the respective condition lever
respective fire handle illuminates
aural alarm sounds

A single FAULT would indicate a fault in the detection system, not a fire itself:

LOOP/FAULT
change in resistance, inhibits fire signal until turned off.
Loop on CAP (DC emer)

You would press the button to turn off the respective loop such that the other loop can detect a fire alone:

OFF
takes respective loop out of parallel circuit. Allows other loop to activate fire signal alone.

Above the buttons it is written: "Agent 1 Loop A" and "Loop B Agent 2". what does this mean and what is the difference between the two systems? In what circumstances would the pilot have to press both discharge squib buttons or both fault off buttons? In what circumstances would they only have to press one?

There are two fire extinguishing bottles and each can be discharged into either engine (Agent 1 refers to the bottle on the same side and Agent 2 to the one on the other side):

The correct procedure for an IN FLIGHT ENG FIRE is:

PL [Power Lever] affected side ... FI [Flight Idle]
CL [Condition Lever] affected side ... FTR [Feather] THEN FUEL SO
FIRE HANDLE affected side ... PULL
if condition persists after 10 seconds:
AGENT 1 affected side ... DISCH
if condition persists after 30 seconds:
AGENT 2 affected side ... DISCH
LAND ASAP

(ATR 72 QRH)

Source: ATR Systems Training Document
Also have a look at this YouTube video found by Jpe61.


What kind of tools are available to an ATC handling traffic in the terminal airspace to predict aircraft trajectories? I know that the ATC has feedback on the current position of the aircraft via Radar and ADS-B data. However, are there any tools to forecast future trajectories. For example, say an aircraft is scheduled to arrive at an airport and will reach within the coverage of the terminal airspace ATC in the next 5-10 minutes. Does any tool help forecast that aircraft's trajectories based on filed flight plans? Does the ATC pay attention to the aircraft only after the pilot has established contact via voice?
Similarly, let's say the ATC assigned some vectors and maybe allocated a runway to an aircraft. Does any tool predict the trajectory the aircraft would follow so that any future vectoring or allocations can be planned?
If such tools are not available, what is the ATC process for handling terminal airspace traffic?

Yes, there are several ways for the controller to predict the trajectory of a flight. The closer the flight gets, the more precise the predictions also get.
It all begins with a flightplan. Prior to departure, a flightplan will have been sent to all ATC units expected to be involved with handling the flight. This includes an estimated time of departure (EOBT) and an estimated elapsed time (EET). Based on these, you can roughly predict when a flight will enter your airspace. The estimated time of departure in a flightplan, however, is not very accurate, since the flight is allowed to deviate from it with +/- 15 minutes.
In some cases, when the flight takes off, a departure message (DEP) will be sent to everyone who has received the flightplan. The DEP message contains an actual time of departure, which allows you (again based on flightplan data including EET) to calculate a more precise estimated time of entry into your airspace. This is still not very precise, since many different things can happen enroute that means the flight arrives some minutes earlier or later than expected.
Next step is coordination. For IFR flights, every transition from the area of responsibility of one ATC unit to the next requires prior coordination. Controllers often do this manually (via phone), but more and more systems support automatic coordination and exchange of estimates, for example via "On-Line Data Interchange" (OLDI) or other electronic message formats. You will typically receive a coordination for a flight somewhere around 5-10 minutes before it enters your airspace. The coordination will contain a precise estimate of when exactly the flight enters your airspace. The required precision for such an estimate is typically in the range of 3-5 minutes (if a delay occurs after the coordination has happened, exceeding the 3-5 minute tolerance, a new coordination has to be done). This is really the point at which the controller will start "paying attention to the flight" as you say.
Up until now, the flight has still not checked in to your frequency, but that is the next step.
When the flight calls you - assuming a radar based environment - you should be able to identify the flight on the radar. This gives you a precise location for the flight, along with current level, track and ground speed. Knowing these values lets you extrapolate the trajectory of a flight quite accurately. System complexity varies, but common for all radar systems I know is the option to show a "prediction vector". This is a vector (straight line) drawn from the radar track symbol of a flight in the direction of travel for a certain length, commonly based on the ground speed. For example, in a terminal environment, you might have 2-minutes prediction vectors enabled for all tracks, which means that, for all radar tracks, the system will draw a line indicating where the aircraft will travel in the next two minutes (assuming, and this is important, constant heading and ground speed). This is a very intuitive way to visualise for the controller both the current heading of a flight, and its speed, which is useful in many different situations. The controller usually has the option to change the look-ahead time of the prediction vector, either for all tracks or for a single flight, typically in 1-minute intervals.

The green lines shown here are prediction vectors
Note that a prediction vector only works based on current heading and ground speed. A change of either of these will change the prediction vector. There are systems that take into account the planned route of a flight when predicting the trajectory, such as Medium Term Conflict Detection (MTCD), but these are mainly used in the enroute (ACC) environment. In the terminal environment, aircraft are climbing and descending, which means they are constantly changing (ground) speed. Also, many aircraft in the terminal environment are under radar vectors, which means they are not following predefined routes, so the system has no way of knowing if and when an aircraft is going to make a turn (since this is decided by the air traffic controller on short notice). These factors make tools such as MTCD pretty much useless in the terminal environment.
There are also trajectory based safety nets, although that's not exactly what you are asking.
Short Term Conflict Alert (STCA) is used to warn the controller of possible impending losses of separation between two radar tracks. You can think of STCA as working similar to a prediction vector, the main difference being that the STCA uses a 3-dimensional vector, since vertical movement is considered as well as horisontal movement. However, just like a prediction vector, STCA only considers what the aircraft is doing right now and extrapolates that into the future. The system does not know if a flight is going to make a turn or level off in 10 seconds. Because of this, the threshold values for triggering an STCA are usually set lower that actual separation minima, to reduce the number of nuisance alerts (e.g. if the required separation is 1000 ft, an STCA might be set to trigger if the predicted separation is less than 800 ft).
There are also tools such as Minimum Safe Altitude Warning (MSAW) and Area Proximity Warning (APW/AIW) which present a warning to the controller if a flight is descending lower than a defined safe altitude or about to enter some sort of restricted airspace. For the most part though, these are based on current position and altitude of a flight, not predicted trajectory.
As for the last part of your question, no, there are no tools that tell the controller how to vector a flight. After all, that is what we are trained for and do very well. With commonly available computing power, there are simply too many variables to consider for a computer to vector and sequence aircraft as efficiently as a human controller. Although, in my opinion, it is probably just a matter of time before supercomputers can more or less take over such tasks.


What common forms of deice and anti-ice exist and what future alternatives are being researched? For the leading edges of aircraft's flight surfaces, there are a few more common deice and anti-ice methods available. What are the most common systems? What are the alternatives? Is there any research going into alternatives where new technology might provide better or more cost effective solutions?

In general, deicing (removal of ice after it had formed) and anti icing (prevention of ice formation) methods used are:

Image from GKN Technology: Leading the way toward more efficient aircraft

Mechanical which simply pushes the ice off the leading edges. An example is the pneumatic deicing boots, which is the oldest method used where an inflatable rubber boot is used for removing accumulated ice from the leading edges.

Source: quora.com

"Deicer (PSF)" by Pearson Scott Foresman - Archives of Pearson Scott Foresman, donated to the Wikimedia Foundation→This file has been extracted from another file: PSF D-240001.png.. Licensed under Public Domain via Commons.

Heating In large aircraft, the wing (and tail) leading edges are heated by engine bleed air (electro-thermal heaters in case of Boeing 787) for anti-icing and de-icing.

Image from Aircraft Anti-Icing Systems by Leslie Mehl and Annie Parsons

Chemical de-icing systems use dry or liquid chemicals designed to lower the freezing point of water (various salts or brines, alcohols, glycols); or by a combination of these different techniques.
Fluid de-icing systems which use de-icing fluid from a storage tank and fed through micro-filters to a number of porous metal distributor panels. As the fluid escapes, it breaks the adhesion between the ice and the wing and the airflow carries it away, creating the so called 'weeping wing'

There are a number of other de- and anti- icing methods are also available/under development, such as:

Electro-impulse method used high-voltage capacitors, which are rapidly
discharged through the coils installed just inside the skin of the aircraft leading edge, resulting in a electromagnetic repulsive force (on the aircraft skin), throwing ice in all directions. However, the electromagnetic interference and structural fatigue associated with this method limits its application.
Electro- Expulsive Separation System An electric current runs through parallel layers of flat, copper ribbon. When a large pulse of current is passed, a repelling magnetic field is created, causing the upper conductor to jump less than a twenty-thousandth of an inch. The resulting high acceleration causes the the ice to break into tiny particles that fall from the airplane's surface.

Electro-Expulsive Separation System shatters and ejects ice from a wing model in a wind tunnel test from ipp.nasa.gov

Electro-Mechanical Expulsion Deicing System, whose principle of operation is given by the developer as,

  A microsecond duration high current electrical pulse delivered to the actuators in timed sequences generates opposing electro-magnetic fields that cause the actuators to change shape rapidly. This change of the actuator shape is transmitted to the erosion shield of the LEA causing it to flex and vibrate at a very high frequency. This rapid motion results in acceleration-based debonding of accumulated ice on the erosion shield.

Image from An Overview of the Deicing and Antiicing Technologies with prospects for the Future by Zdobyslaw Goraj

Ultrasound Some research is also going on into vibrating the wings using ultrasound to remove ice formed.
Shape memory Alloys have also been proposed to be utilized for deicing and anti icing, with their shape changing properties being used for ice removal when required.

Image from An Overview of the Deicing and Antiicing Technologies with prospects for the Future by Zdobyslaw Goraj

There has also been some research into usage of carbon nanotubes for this purpose.


Identify a change in Altitude based on direction and WCA applied? Question below is from study material for the EASA PPL license MET course.

It's an unlikely question but it's interesting to review.

You are flying from west to east with WCA +6°. How is your true altitude changing with all else remaining un changed.

A) It will degrees
B) It will increase
C) Will remain stable(unchanged)
D) None of the above are correct.

My Question, how is this easily explained, does it have to do with Buys Ballot's law ?

The question is confusing because the graphic doesn't match the question being asked.  Does the question actually use this graphic?  Because if it does then your WCA would be negative if you are heading East because you would be crabbing to the left to account for wind coming from the North.

In any case, if you are flying from an area of high pressure to an area of low pressure (as the graphic depicts) without changing your altimeter setting your true altitude will be lower.  Remember this simple mnemonic:  "High to low, look out below."

However, if the question is as stated WITHOUT the graphic, then heading East with a positive WCA means that the wind is from the South.  If this is the case it would be fair to assume from Buy Ballot's law that you are transiting from an area of low pressure to an area of high pressure.  In this case then the answer would be your true altitude would be higher.


What are the risks involved when doing a classic zero-g maneuver? I suspect most pilots have done it at least once: briefly experience zero g when flying a parabolic path. It's quite an experience (if your stomach can handle it).

Question is: are there any risks involved in doing something like that? (I know, getting in an airplane by itself is a risk, but that's not the point)

I could think of a few potential risks, but I'm not sure if they are real or not:

Engine lubrication in single engine piston airplanes

And if not properly executed:

Risk of a stall, both in the pull up phase and in the "arc" phase
Overstressing the airplane when pulling out of the dive to get up to speed

Follow-up questions: Is it considered to be an acrobatic maneuver? Are there any regulations that would prohibit it?

The biggest risk is improper execution.  If you build up too much airspeed and pull out of the dive at 4-G and break something, that will be your primary issue.

Your secondary risks will be associated with the fuel and oil system starvation if they depend on gravity for operation.  This risk is balanced by how long you can sustain 0-g flight.  Oil issues are bigger risk than fuel, as even if you did sustain 0-g long enough to starve the engine, you should get it back as soon as you are in positive G.  This particular risk will vary by airplane and I probably can't say something as general as "not typically a problem for short duration 0-g excursions".

An additional secondary risk is unsecured objects in the cockpit.  This presents a number of possible complications:

floating objects may distract you from aviating
floating objects may break something (the example of a window in the cockpit would cause a major distraction for the remainder of flight)
Most importantly, this can change your CG which can have dire consequences if something heavy enough gets moved far enough.

I wouldn't put risk of stall too high on the list, because you should be doing this with enough altitude and in coordinated flight so a stall would just be a simple recovery.

As for whether this is an aerobatic maneuver, it is a lot like a departure stall but a botched recovery (pushing over to 0-g before the stall breaks) and only a passenger could say for sure what you were actually doing.

That leads into the last risk I can think of, and that is when your passenger deposits his/her lunch all over the airplane.  In 0-g that could get on the windscreen and obscure your vision.  Be careful!


What is weight-climb speed? I have a question about a document published by the Association of European Airliners. The name of the document is “Long Range Aircraft - AEA Requirements.” In the Appendix titled "Definitions and Inputs for Range and DOC Calculation," paragraph 1.1 (“Flight Profile for DOC and Range Calculation”) at Note c) we can read the following recommendation:

  Cruise, and completion of step, shall be at that altitude at which the potential rate of climb, at initial cruise weight-climb speed, is 500 ft./min or more

I don't understand the meaning of that sentence. What’s the definition of “weight-climb speed?”

A cruise weight-climb is a climb segment during the cruise phase of the flight to achieve a higher flight level that was previously not reachable due the weight of the aircraft.

Long range aircraft cannot climb as high initially because of the weight of the fuel they carry. Their operating ceiling is power limited. As the aircraft burns off weight during the flight, the drag decreases and gradually excess power becomes available for climbing.

This recommendation is not to start climbing to the next level until a vertical climb speed of 500ft can be maintained at the new level, at the initial cruise speed after that weight-climb.

For example, if the the cruise starts at FL270, and one wants to climb to FL290 for a cruise at Mach 0.80, the weight-climb should not start before the aircraft can maintain a 500 ft/min climb at Mach 0.80 at FL290.


Has a commercial airliner ever crash-landed in an ocean? They have rafts and life jackets on board and before takeoff, passengers are explained how to use that equipment, but have any evacuations ever happened successfully?

Yes, commercial airplanes have landed or crash landed in water many times.

If I am not mistaken, you are asking about scenarios when the on-board life jackets and life raft are used.

Here is a list of water landings. Examples when a life raft was used are (in addition to ratchet freak's mentions):

  On 22 October 1962, a Northwest Airlines DC-7C with 7 crew and 95
  passengers made a successful water landing in Sitka Sound. ... The
  plane stayed afloat for 24 minutes after coming to rest in the water,
  giving the occupants ample time to evacuate into life-rafts.

  In 1993, China Airlines Flight 605, a Boeing 747–409, ended up in
  water after it overran runway 13 ... All of the 396 occupants donned
  life-vests, boarded the eight slide/rafts and no fatalities resulted.


How are wing tanks sealed around the internal wing structure? I can easily grasp the idea of tanks of fuel inside the fuselage of an aircraft, and the ease of sealing such tanks in a relatively standard shape.  However, I'm having a hard time understanding how wing tanks could be fit around the internal structure of a wing, as I envision the inside of a wing (especially nearer to the fuselage) to be a honeycomb of structural pieces that would be very difficult to seal around or find any large volumes of contiguous space for fitting tanks.  Is the wing structure itself the fuel tank, or are there separate fuel tank bladders that are somehow fit into the wing voids?

For my question, I am not concerned about military fuel tanks which might have special materials in the walls which could seal off a leak due to combat damage, but rather just non-military aircraft.

The tanks are generally sealed with some kind of putty/resin/epoxy like material. Keep in mind that only the joints between exterior panels need to be sealed. On many aircraft this is done through inspection panels. The material is, in a manner of speaking painted/applied.

Here is an example from a Mooney, which are pretty infamous for having in wing tanks

(source)

Tanks on larger aircraft are not all that different, much like this one off a 747

(source)

its worth noting that tanks don't need to be continuously open, they can have structures with in them as long as the fuel is free to flow around. Large and small tanks alike may very well have structural elements inside with flow holes drilled to allow fuel to move around. These elements also help reduce the effects of large quantities of fuel sloshing around as the aircraft changes attitude.


Why should jet engine throttles be moved smoothly? On the only jet engined aircraft I'm trained on, the Bell 206B (Allison 250 engine), I was taught to move the throttle slowly and smoothly, especially when opening.  I've also see this done with Rolls Royce testing RB211s and early Trents.

I've realised I don't actually know why this is.  Is it to prevent possible flame out with a sudden increase in fuel with no corresponding increase in air mass since the engine will spool up much more slowly?

Do modern engines need this handling?  In this video at about 0:17, the pilot commences the roll by more or less slamming the throttle open. My guess is that like all other computer controlled controls, the FADEC interprets this as "as much fuel as possible without flaming out".

The issue is the possibility of a compressor stall.  The combustion will directly respond to changes in the thrust lever but it takes time for this to spool up the turbine that is connected to the compressor.  If the incoming air from the compressor is not of adequate pressure because it hasn't spooled up enough you risk a compressor surge.  In these engines you need to slowly increase thrust so that the turbine can spool up (and hence the compressor) so the airflow through the engine remains adequate for the engine power.

Modern engines with FADEC systems should not have these issues as the FADEC can enforce rate limits for fuel flow increases or directly calculate the maximum safe fuel flow from observed engine parameters.  Modern engines might also have more sophisticated compressors with variable stators that can help mitigate compressor stalls/surges.


What are the advantages and disadvantages of a monoplane, biplane and triplane? What are the pros and cons of a monoplane, biplane and triplane design; aerodynamics, efficiency, etc.?

One way to look at the differences between them is by looking at the effects of having multiple wings.

Having multiple wings means that the same aircraft can produce more lift for the same wingspan, as they have a greater wing area.

As a result, the biplanes and triplanes have lesser wing loading, which results in shoter to/landing and lower stall speeds.

The shorter wingspan results in reduced roll inertia and roll damping, which results in better roll rates in the bi- and tri- planes. This improved maneuverability was the reason for the surge in triplane designes during WWI.
Due to interference effects, the bi- and tri- planes actually require higher wing area to produce the required lift. Also, the drag is also higher than the monoplane, which gets more pronounced as the speed increases.
The main reason for the use of bi- and tri- planes was that they provided the required strength for the type of airfoils used. As high strength materials became available, this mattered less and the aerodynamic disadvantage of the biplane (and triplane) designs came into fore.

The aerodynamic advantage of the monoplane along with improvements in materials used has made the monoplane the de-facto standard except for certain specialised applications (like low speed aerobatics)


Why do some turbofan blade have forward swept tips? I notice that in Trent700  engine fan blade there is no curve extension at the tip unlike in other engine's fan blades such as the GE90 ,T900 etc.

What are the purpose of it?

Trent 700 without forward swept blade tips

Engine with forward swept blade tips

Increasing performance of the fan means making it rotate faster. Tips of the fast-rotating fan travel at supersonic speeds. This design of fan blades is to overcome blade stall and to increase effectiveness of the fan. The design is probably patented and that's why it doesn't show up on engines of other manufacturers.


What are the flaps on the exhaust of military airplanes for? I have been looking over some pictures of military airplanes, and I noticed that some of the more modern air planes have flaps on the exhaust

I was wondering if anyone knew what the purpose of the flaps were, and why they are only on modern airplanes

Those flaps on exhaust are for thrust vectoring. A simple definition would be:

  the ability of an aircraft [...] to manipulate the direction of the
  thrust [...] to control the attitude [...] of the vehicle

F-22 uses it like this:

  [Its] nozzle [...] is the first vectoring nozzle. That means
  the pilot can move, or vector, the nozzle up and down by 20 degrees.

  The gases coming out of the vector nozzle help push the airplane's
  nose up or down. This vectoring increases the roll rate of the plane
  by 50 percent, making it much more maneuverable than other fighters.

  Thrust vectoring [...] works automatically in response to commands
  from the pilot.


Any ANSPs uses stack controllers? The stack controller only controls one or two stack and release aircraft accordingly. Does any ANSP (air navigation service provider) provide this service?

Airborne holdings are usually handled by ACC or approach sectors, typically manned by ACS or APS rated controllers respectively. There is no separate rating for "stack controllers" as you call them.


What is the "8900" that the FAA uses for guidance? The 8900 is sometimes quoted as a reference when trying to determine FAA policies.

What exactly is it and where can it be found?  Is it regulatory in nature?

The Flight Standards Information Management System, created by FAA Order 8900.1, is the source of all information relating to aviation safety inspector job tasks.  It's about 8,000 pages worth of (non-regulatory) guidance and policy helping FAA Inspectors to do their job properly.

It's an electronic-only document, which can be found at fsims.faa.gov, or by visiting the FAA homepage and entering "8900" in the search box at the top right.

There's all kinds of good stuff in there, such as:

How do I give a practical test for a CFI applicant with a sport pilot rating?
How do I perform field approval of a major repair or alteration?
How do I do a ramp inspection?

And lots more!

FSIMS is open to the general public - if you want to know what an inspector does day in and day out (or what to expect when you meet one), FSIMS is the one-stop-shopping location for the answers to all your questions.


What's the refueling process like for a light aircraft? This is for a writing project. I've only been able to find descriptions of refueling large jet aircraft. The plane, a de Hallivand DHC-6 Twin Otter, carries 4 passengers, all minors. None have any significant medical issues. I have no knowledge of flight procedure in any form. How would the timeline look for the whole refueling process? How long would it take? Would the passengers have to leave the plane? If so, where would they be required to go?

Thank you very much, anyone who answers; this stuff is gold to an aerial neophyte like me :)

The DHC-6 Twin Otter has two fuel tanks located in the belly of the fuselage, one forward (1235 lbs or 185 gal) and one aft (1341 lbs or 201 gal). There is a fuel fill port on the port side of the fuselage above each tank.

Refueling a plane is similar to refueling a car, except (a) planes can hold a lot more fuel than cars, (b) you rarely completely fill the tanks due to weight limitations, and (c) full service is fairly common.

However, with a very light load and a very long trip, you would completely fill the tanks to maximize range. That can mean 30+ minutes at the pump for a plane this size.

For self service, you taxi over to the self-serve pump, stop the engine(s), insert your credit card, attach the ground wire, insert nozzle, pump however much fuel you need, take the receipt, restart the engine(s), and taxi away.

For full service, typically you park on the ramp or at a terminal, call (on the radio) for a fuel truck, the driver does the fueling while you're parked, and you settle the bill before leaving.

Note: in less developed countries, you will likely have to pay cash (USD is accepted everywhere) before they will give you fuel, especially in large quantities. And a smuggler may not want bank records of their transaction anyway.

Normally, passengers will want to get out at fuel stops to stretch their legs, use the restrooms, get snacks, etc. But it wouldn't be unreasonable for passengers to remain aboard if the story has a reason for them to want to stay out of sight.


Do modern flights and pilots have reservations about flying over the Bermuda Triangle? I know that the Triangle was pretty much legend back in the days but now, given that there is so much technology involved with respect to tracking and communications, do pilots, flights and airlines still have reservations about flying over this area? If so, why, and if not, are there regular flights/airlines that go over this route every day?

A quick check of a site like Flightradar24 will show that the area is not overly avoided. The triangle between the southern tip of Florida, Bermuda, and Puerto Rico has quite a bit of traffic.

The southern part is a busy route from Florida to Puerto Rico and other areas in the Caribbean. The rest is also part of routes from the east coast to the Caribbean and South America.

While the idea of an area causing mysterious disappearances is understandably popular, evidence suggests that the area has not been significantly more dangerous than other areas in the world. As noted, it's an important route between Florida and the Caribbean, and one would expect lots of traffic in this area, and therefore lots of incidents.

While navigation issues were once a not-infrequent cause of air incidents, modern technology has made this sort of thing much more rare. Airline flights are monitored by ATC. Anomalies in either magnetic bearings or radio aids such as VOR or GPS are routinely surveyed and listed on navigation charts. I took a quick look and nothing seemed to stand out here. Weather forecasting has also become much more helpful with the usage of long range weather radar and weather satellites.

A look at incidents in this area shows most incidents were in the 1960s or earlier. The few recent air incidents seem to be nothing out of the ordinary. General aviation accidents are fairly common (flying into a level 6 thunderstorm also not advised), and airliners divert due to technical issues fairly frequently.

While some people may have apprehensions about the area, this concern doesn't seem to be supported by a higher than normal rate of incidents and the area is routinely traveled by both ships and aircraft.

From Flightradar24.com

Don't worry about that question mark, I'm sure it's totally routine, nothing to see here


Can trimmer and throttle be used for controlling large aircraft During my PPL training, We practiced some emergency procedure on Piper cherokee and simulated flight controls failure.

My instructor asked me to sit on one hand and place the other on the trimmer.

I had to fly the aircraft using only rudder and trimmer, using trimmer and power for pitching and rudder for direction until short final.

My question is... Can the same procedure be exercised on big aircraft like Boeing?

To some extent, yes. There was United Airlines Flight 232 in which catastrophic failure in the tail engine destroyed all the hydraulic lines. The plane was crash-landed in Sioux City, Iowa after the pilots controlled the aircraft using only the two intact wing engines. The trimmer might not produce as large as an effect on larger aircraft as on smaller ones; control of the engines would be enough because they affect the aircraft more than the trimmer due to their thrust.

However, if the damage is so severe that a control surface is destroyed or locked into a certain position, the engines might not be able to counteract that.


How do you request a 3D block of airspace to to freely maneuver your privately owned military jet? Referring to this How can you fly your own military jet in terms of altitude and acrobatics? how can you request a block of airspace to freely maneuver your private military jet (barrel rolls, vertical climb, pulling Gs, etc..).
If that kind of block of airspace is indeed possible to be permitted, what are your limits flying your jet in it?

As @jamessqf points out, once the aircraft is no longer owned by the government1 there wouldn't be any regulatory difference between you requesting air work and, say, a Gulfstream acceptance or post-maintenance flight that needs to fly around at odd altitudes and attitudes to check out various systems. That said...
Below FL180 you can fly VFR as you like. Of course you still have see-and-avoid responsibility, which might be helped by any onboard targeting radar on your military jet but then again might not be.
If you want to go higher (and have a smaller chance of turning someone's Cessna into a hood ornament) you need an IFR flight plan. Ideally you'd ask someone for permission to enter a Military Operations Area (example) and/or Air Traffic Control Assigned Airspace (which is the same concept as a MOA but exists in Class A airspace). FAA Order 7400.10 will tell you who the controlling agency and using agency are for each MOA; if you wanted you could try cold-calling Albuquerque ARTCC and asking if they'd take the Mt. Dora MOA hot for you, but the Air Force's 27th Special Operations Wing is the using agency and the line controller probably won't help you unless you run it by the military beforehand.
Assuming you can't get clearance into special-use airspace your only other option is to request a quadrant clearance in conjunction with a block altitude assignment.
A quadrant clearance (7110.65 4–1–1i) allows you to fly between two specified radials of a navaid and within two defined radii (DME arcs). Depending on the performance characteristics of your jet you might need a significant amount of distance, e.g. between the 10-mile radius and 40-mile radius, in order to get a large enough slice of airspace to work in.
A block altitude assignment (7110.65 4–5–7g) is more commonplace and allows you to operate anywhere between the two indicated altitudes. Again you'd probably want a good eight-to-ten thousand feet or more.
For both the vertical and lateral considerations you'd probably have the most luck over the Western states (ZLC, western ZMP, ZAB, etc). You could also try going offshore as long as you checked to make sure the warning areas weren't hot.

1Or operated on behalf of the government; I've seen a couple N-numbered British/European fighters operate using tactical callsigns as aggressor aircraft for military training exercises.


Could propeller wash provide sufficient lift to take off - even in theory? I know this seems a crazy thing to ask but it is not the same as lifting oneself by the bootstraps. If you try to lift yourself that way, there are two equal and opposite forces, yet there are experiments with muscle powered planes that work.
So, provided the plane was stabilised somehow, and the wings were designed for the purpose, could propellor wash theoretically lift the plane? If not why not?

Note
I understand that a normal plane would start to move forward. Please assume that the plane is restrained from the rear by a cable and that the experiment takes place in the absence of wind.

Yes.  The wing doesn't care what is causing air to flow past it.  Headwind, propwash, 747 wake, gopher sneezes.
If the airplane is restrained from forward motion, and the propwash over most of the wing is fast enough, let's say more than the airplane's stall speed, then the wing must generate enough lift to support the airplane, causing it to take off.
It's not so much a matter of designing the wing specially, as making the airplane tolerate the many large props needed, and the weight of the engines.  That much power is too much for efficient cruise.  But it's easy to implement with a one pound model airplane.


What types of data can be extracted from a non-motion flight simulator? What are the types of data that can be extracted from a non-motion flight simulator?

Based on the type of data I want to do:

A comparison study between flight simulator data and ground-based systems data
To know if it's possible to calculate the fuel consumed by an aircraft while following certain ATC procedures, so that further improvements in fuel consumption can be explored by altering those procedures

It will depend on the representativeness of the modeling.

If your fuel system model, your engine model, and your aero model are representative of the aircraft, whatever is the qualification of the simulator, you will have good results. However, it will never be as accurate as the aircraft because of the unprecision of the modelisation and the fact that we are not able to modelise the thermodynamic part of the engine. We are using tables to get that and it creates a lot of inconsistency.

For example, if you try to look at the engine consumption in cruise it will be pretty accurate, but during acceleration phases, it will not be accurate at all due to the inconsistencies.

A simulator qualified as FNPT II + MCC under EASA or Level 5 under FAA should have the same representativeness as a Full Flight Simulator Level D for all the models talked above. So it will give you a good idea, but will never be accurate. However, it is still the best you can have from a simulation.


Why don't airliners carry radar jamming technology or missile counter measures? Why is it that commercial passenger aircraft that fly through dangerous areas don't carry some sort of electronic counter measure to defend themselves from missiles?  Between terrorism and the various war zones dotting the globe, it seems like it would be prudent for airliners to have them.  At least for aircraft that are flying in places that are possibly dangerous.

I've been thinking that it's probably a lot of expense and weight for something that isn't terribly likely to happen, but I wondered if there might be more to the answer or if, at very least, someone could add some details to my assumption.  A good cost/benefit analysis would be appreciated if anyone is familiar with the cost of operating such a system.

Surface-to-air missile attacks on airliners at cruising altitude are vanishingly rare: there have only been three known attacks in the past half-century (MH-17, IR-655, and probably S7-1812).  Any protection system needs to take that into account -- any safety system needs to be justified in terms of cost, weight, and safety -- it needs to save more lives than it costs.

Direct jamming.  Suppose you stick an AN/ALQ-99 jamming pod on the airplane.  That's 6000 extra pounds, a good deal of drag, and a bunch of parts that can break off, catch fire, or otherwise be a hazard.
Active countermeasures.  Stick an AGM-88 HARM missile on the plane.  Now, your anti-radar missile isn't much faster than the radar-guided missile trying to shoot you down, so for reasonable safety, you need to launch as soon as you get painted by the tracking radar.  What do you suppose the odds are that a twitchy co-pilot acting as ECM/weapons officer is going to launch against an innocent control tower?  How many weather radars are you willing to destroy to save that one airplane every 20 years?  Are you sure that missile will never malfunction on the launching rack and destroy the airplane?
Stealth.  Hiding from radar-guided missiles means you're also hiding from traffic-control radar.  How often are crashes prevented by that radar?  I bet it's more than one every twenty years.

The benefit is roughly one less airplane crash every 20 years.  That means the cost, both in terms of money and in terms of risk, needs to be very, very low.


How does air traffic control communicate with an aircraft? I have a question on voice/data communication between air traffic control and an aircraft.

I read somewhere that control communicates with an aircraft directly, through a direct radio link, while it's within the line-of-sight. After that control communicates through satellite.

My questions are:

Why doesn't control use satellite throughout the flight?
Are direct radio links used only for voice services? or are they used for data as well?

1) Why doesn't the tower use satellite throughout the flight?

The narrow answer is that the control tower is responsible for a small geographic area.  The "tower" doesn't want to talk to the craft at other points in the flight, so the need is not there.  It only wants to talk to the plane when it is close to the tower's airspace.

Other components of air traffic control that do need to talk with airplanes in flight also divide up regions of the airspace and have radio equipment situated to talk to the necessary craft.

A larger answer is that ground control and aircraft communications were under major development for decades before satellite communications were available.  The system we use today is heavily based on line-of-sight VHF communication radio over most populated areas.  Since these systems are already installed in many thousands of aircraft, changing to something different like satellite communication requires a significant benefit, someone to pay for it, and a lot of time to allow for the change.

  2) Does a control tower only send voice services through the direct
  link? or does it send data as well?

Data is beginning to be sent via CPDLC.  You can search for CPDLC on this site and find several questions and answers about it, but it is considered only a supplement to the voice communication of ATC today.

  Aren't there security issues or power safety issues involved in ground
  to air transmissions?

Unauthorized transmissions are possible, but they are managed and haven't traditionally been a big problem.  There's another question about What prevents someone from hijacking a radio frequency mid-air?.  But much of the answer is that since ATC is monitoring the frequency, unauthorized transmissions would be heard and responded to.  I'm sure that future digital delivery will change some of these issues, but that's likely to be true whether the message is transmitted via local radio transmitters or satellite.

Not sure if that's what you meant by security issues.  I'm not familiar with power safety issues.


Do aircraft carry commercial VHF radios? Years ago, I was working in the bush and we used portable radios on something like 154MHz. When it came time for pickup, we were able to talk to the helicopter pilot on that frequency. Since it's outside the air band, I'm wondering if it's normal for aircraft to have VHF radios installed to cover commercial (and maybe amateur) VHF bands.

No, is the short answer. Aircraft generally only carry radios covering the bands they require as standard - i.e., those covering aviation communications and navigation. I have an airband transceiver here and it can't physically be tuned that high. As far as I know, the ones in the planes I fly are identical.
I can't see any advantage in doing otherwise, as standard, as the vast majority of pilots are not licenced to talk on such bands.
In terms of citation, here's a popular general aviation radio, the BendixKing KX 165A
https://www.bendixking.com/en/products/nc/navigation-and-communication/kx-165a

Communication Transceiver: 118.000 MHz to 13.975 MHz in 25 kHz
increments, 118.0000 MHz to 136.9916 MHz in 8.33kHz increments
(118.000 - 136.990 displayed per DO 186a and ED-23B) (8.33 kHz capable
KX 165A only) Navigation Receiver: 118.00 MHz to 117~ .95 M

And, here's another:
https://icomuk.co.uk/IC-A220T/Panel_Mount_Aviation_Radio
(From the manual: https://icomuk.co.uk/files/icom/PDF/productManual/A220-TSO-Instruction-Manual.pdf)

Frequency Range: 118.000 to 136.992 MHz (8.33khz)


How is auto-rotation different in coaxial rotor helicopters? Coaxial Helicopters have two main rotor sets, one on top of the other, spinning in different directions to eliminate the need for a tail rotor. I've heard it said they're also more maneuverable, all else being equal.

So how is auto-rotation different (if anything) for these kinds of helicopters? Is it any easier? Do you get longer range and/or slower (safer) descent speed?

There's one major difference between a coaxial helicopter and a conventional single main rotor -- single tail rotor helicopter during autorotation: yaw control.

A conventional helicopter has a main rotor which produces a torque. The tail rotor thrust, applied at the end of the tail boom, provides a counter-acting "anti-torque" to keep the helicopter pointing when the pilot wants it.  As the pilot, when I change the collective pitch of the main rotor, to go into a climb or a descent, the torque required to drive the main rotor goes up or down, and the pilot counters by raising or lowering the tail rotor collective to change the tail rotor thrust to match.  Additionally, if I want to yaw the nose to the left or right, I can use the pedals to raise or lower the tail rotor thrust in order to temporarily upset the balance between the main and tail rotor torques and steer the aircraft.

Now, consider how yaw control works for a coaxial helicopter.  The torque of the upper rotor is now counter-balanced by the torque of the lower rotor.  To yaw the helicopter, the pedal inputs are set up to upset the balance of torques by raising the torque on one rotor (by increasing the collective) and lowering it on the other (decreasing collective), while maintaining the same thrust.

Now, when I increase my rate of descent to autorotation, the engines are no longer providing torque to drive the main rotor--the rotor is being driven by the relative wind.  In a conventional helicopter, the tail rotor is still being driven by torque transmitted from the main rotor through the drive shafts--so while there's no main rotor torque to balance, I can still use the pedals to change the tail rotor thrust and control my yaw.  However, in a coaxial helicopter, when the  torque on the rotors is low, differential collective does not have very much control authority: depending on the collective setting, pedal inputs can have a weak effect, no effect, or most surprisingly, a negative effect!  To counter-act this, most coaxial helicopters have very large vertical fins to provide good low-speed directional stability and many have rudders to augment control.

For instance, here's a picture showing the empennage of the Kamov Ka-25 (from aviastar.org).

More modern machines also have control systems that reverse the effect of pedal inputs on differential collective at the very low collective stick settings where control reversal can occur.  Flight manuals for coaxial helicopters advise against reducing forward speed too quickly during autorotation, since the directional stability is provided primarily by the body and tail.


What is the angle between A330 body and the ground? Since the standard A330's nose-down body angle on the ground, the A330F uses a revised nose undercarriage layout to provide a level deck during cargo loading to overcome the issue.

What is the angle between A330 body and the ground?

TL;DR The angle is about 1 degree.

The best reference I can think of is the aircraft characteristics document provided by Airbus. This provides key dimensions for the A330 family.

I looked at the dimensions for the forward and aft lower deck cargo doors. The document provides both the distance from the ground to the floor of the hold (§2-3-0), and to the door center from the nose (§2-7-0). With this information, an inverse tangent will give the angle of the deck between the doors.

There are two factors that affect these numbers. First, the three models of aircraft have different measurements. The other factor is weight and balance of the aircraft, which affects how much the suspension on each gear is compressed. A heavier aircraft will sit lower to the ground, and the location of the center of gravity will affect how much weight is resting on each landing gear position.

Calculating the angles gives the following angles. Note the larger angle on the shorter -200, and the difference of about a degree between the values on the -200 and the freighter -200F.

Although 1 degree may not seem like much, note the difference of about 33 cm (13 in.) height between the -200 and the -200F at the forward cargo door. This is near the nose gear, which is the reason that modifications were necessary to fit the extra nose gear length in the gear bay.

-300

176,000 kg, CG 26.8%: 1.2 deg
MRW, CG 15%: 1.1 deg
MRW, CG 36.5%: 0.8 deg

-200

119,000 kg, mid CG: 1.4 deg
MRW, CG 21%: 1.3 deg
MRW, CG 37.5%: 0.8 deg

-200F

115,000 kg, CG 20%: 0.4 deg
MRW, CG 20.6%: 0.2 deg
MRW, CG 37.4%: 0 deg


How does wake turbulence affect parachutists? If one were to parachute out of a jumbo jetliner, would wake turbulence from the plane be an issue?

A 747 for instance produces much more wake turbulence than the smaller planes usually used to drop parachutists. Would that make a difference, or does the trajectory of a parachutist stay clear of wake turbulence in any case?

Qualification: I am a master parachute rigger and I taught sport parachuting for 10 years.

The back door of a 747 is actually in a pretty good position - the tail is above the door and the fuselage is narrowing at that point so it's not a complete side exit.

A freefall jumper will drop out of the aircraft's wake in under a second so that's not really an issue. If we pick a theoretical worst-case where a jumper goes straight through a huge vortex they might get flipped over. Remember that a human does not have large surfaces like wings to interact with. Any jumper that can't recover from that won't be doing freefall jumps anyway. Seriously, this is in the Jump #1 stability lesson, and if you haven't got it sorted by jump #6 any reputable school will send you home.

Exit speed is a consideration - sport gear is meant for < 200km/h. If we are going out at 747 cruise speeds I would tighten everything right up1, wrap some tape around the riser covers2 and tuck the pilot chute handle completely into the pouch. Maybe also tack the closing flap cover down. Yes guys, it will still open if you sew it to the proper flap. If the plane is at approach speeds with flaps and gear down then you're fine - not much different than a King Air.

So in conclusion, yes, you can jump out of a 747. Rent one and you will have every jumper in the state lining up for tickets.

To reply to the comment of the pilot chute going over the tail, that happened at our place too (and to me once, but mine went under the tail). It's got nothing to do with turbulence - the pilot chute got pulled mostly out of the pouch, most likely snagging something, and the air picked it up from there. Our guy actually hit the tail. He had nasty bruises and needed a few lines changed, the pilot needed new underwear, and the Cessna needed a bunch of rivets and sheet metal work. When it happened to me I had a surprise deployment at 9,500 feet and a longer than usual ride down.

1 to the point where you will need my tools to close it.
2 it will break away after opening, and won't be more than an annoyance if it doesn't


What is the methodology for assigning airport codes? Pearson airport in Toronto has the airport code YYZ, which does not reflect the name Pearson or the city of Toronto. This seems contradictory to other IATA codes like LGA (Laguardia), JFK (John F Kennedy), LHR (London Heathrow), and DFW (Dallas Fort Worth).

Is there a specific methodology in place for assigning these values?

There are different kinds of codes assigned to airports. IATA codes, which are the three letter codes you mention; are for travel industry identification purposes (by the way, these aren't restricted to airports - train stations also have these codes). These are used by airlines and travel agents.

The other four letter codes are ICAO codes. These are used for navigation, air traffic and flight planning.

ICAO codes have a defined standard, each region is assigned a letter and all codes begin with that letter. Canada is assigned a practical C, US is K:

IATA codes however, are arbitrary. For some reason, Canada was given 'Y' and so all IATA codes in Canada begin with Y.

There is YYC (Calgary), YVR (Vancouver), but then you have YQX (Gander) and YXS (Prince George) and YUL (Montreal-Trudeu).


What is the approximate accuracy of ASDE-X? Can anyone suggest some ballpark figures for estimating the tracking accuracy of ASDE-X systems at airports? Specifically, I'm trying to get a sense of the error (± x meters) that can be expected from ASDE-X when fixing the position of an aircraft.

The FAA has a bunch of information on ASDE-X, most of which I personally have no idea how to interpret correctly. The ASDE-X procurement specification in particular has a lot of technical details on radar performance and although I didn't understand much of it I did notice this requirement:

  3.6.3   Map Registration

  The display of target data shall [R306] be registered to the display map with an accuracy of at least 20 feet.

So whatever the technical capabilities of the system are, operationally it seems that you can assume it's accurate to within 20ft, which seems to be reasonable in the context of large aircraft. You may be able to get more out of the documentation than I could, of course.


Does a Mach 1 plane hear a sonic boom from a Mach 3 plane overtaking him? Let's say Bob is flying at Mach 1 and then John, in another aircraft, overtakes him at Mach 3. They are flying parallel to each other, say 500 meters apart. And there is no wind. Their relative speed is Mach 2 of course. Does Bob hear a sonic boom from John, and why or why not?

Please explain it sufficiently enough so that I can apply it to other situations. For example, would it still work if their speeds were more like Mach 1 and Mach 1.25?

To answer the question:

Yes, and even more, both would be able to notice the sonic boom of the other aircraft.

Why

To understand why, you have to understand how sonic booms are created.

Sound is nothing more than waves of different air pressure travelling through the air. Once released by an aircraft or other object, they start to propagate in all directions with the speed of sound in the resting air. (This means the waves do not travel faster than sound, even when the aircraft does!) If we mark e.g. the regions of high pressure, we get growing circles, the center of each being the point where it was created by the aircraft.

If the aircraft is moving, the circles will not be concentric, like in this animation for an object traveling at half the speed of sound:

If the aircraft is moving with the speed of sound, the circles start to touch each other on a line perpendicular to the track of the aircraft, just where the aircraft is. This is not so clear on the next animation, as there are simply not (big) enough circles.
However, on this line, all the regions of high pressure sum up to a region of 'very high' pressure. This is the shock wave, which is often referred to as sound barrier. (The term also describes just the insurmountable speed limit encountered by non-supersonic aircraft.) If this shock wave passes an observer on the ground, he will hear a sonic boom.

As the aircraft accelerates more, the shock wave isn't perpendicular any more, instead, you get two lines. In reality (3D), you get a cone with the aircraft at the tip, and the opening angle is defined by the speed of the aircraft.

Now, to answer your question: As the tip of the cone is where the aircraft is, this cone travels with the aircraft, and with its speed.

So, if an aircraft is overtaken by a supersonic aircraft, it will be overtaken by the cone-shaped shock wave of that aircraft a little bit later, too. Also, the faster aircraft will pass the shock wave of the slower aircraft.

Remarks

An aircraft itself is very loud, but also dampens every noise from outside, and headsets and helmets may contribute to the dampening, too. So, I don't know if a pilot would hear something from the boom. Maybe he does not, but the aircraft definitely crosses the shock wave.
My explanation does not describe where the sound comes from. While the sound of a subsonic aircraft mostly comes from the engines, it comes from the compression of air at the surfaces of supersonic aircraft.
This cone sometimes is visible, as on the following picture of an F18, stolen from air-attack.com. This is because the high pressure region is followed by a low pressure region, where air expands and moisture may condensate. The picture also shows that there are usually two shock waves, each where the cross section of the aircraft changes significantly.  One is generated near the canopy and one near the wings. EDIT: As commented by @PeterKämpf, this picture does NOT show an F18 at supersonic speed. It is at transsonic speed, which is close to, but still below mach 1. The fog forms due to other effects.

However, here is an other picture of a Northrop T-38 at mach 1.1, showing the shock waves, from wiki commons:


Instrument landing: why do all electronic devices need to be shut off? A few days ago, I took a flight home. Towards the end of the journey, the captain asked us to shut down any electronic device that we had on board, including iPods, CD players, phones and so on, because there was very low visibility, and we were starting an instrument approach.

From what I could understand, an Instrument Landing  System (ILS) allows an aircraft to be centred on the approach path, assisted by radio signals delivered by an ILS (a localiser and a glide slope), without any visual reference. These signals are in the 110 MHz (LOC) and 330 MHz (GS) frequency range.

Given that for the take off, visual landing, and the journey itself, shutting off the devices is no longer required (even though there are radio signals being used for communications and navigation), why this extra precaution on a low-visibility ILS approach? What interference could a CD Player possibly produce with the instrumentation to an extent that it's more dangerous than with the normal take off,en route, and landing phases?

On a side note: as you probably understood, my level of expertise is very low, so forgive any dumb mistake or oversight.

Short answer: ILS is rather sensitive to interference and not all electronic devices take much precaution in avoiding the generation of interference. The pilot wants to be sure that the readings he's getting on the localizer and glideslope are accurate, since he can't actually see the runway to verify the final approach path visually.

Longer answer: ILS is actually relatively simplistic as RF signals go. Both the localizer and the glideslope just consist of a pair of AM signals that are broadcast directionally. For both systems, the modulated frequencies are 90 Hz and 150 Hz. For the localizer, 90 Hz is broadcast to the left of the runway centerline and 150 Hz is broadcast to the right of the centerline. When the aircraft is aligned with the runway, it will receive equal strength signals of both frequencies. When it's to the right, it will receive more power from the 150 Hz signal and when it's to the left, it will receive more power from the 90 Hz signal. The glideslope works pretty much the same way, just with the 150 Hz signal transmitted below the glide path and the 90 Hz signal transmitted above it. [1] [2]

Now, suppose some passenger's electronic device is emitting a frequency that it shouldn't be. This is not exactly unheard of among consumer electronic devices. This is more common among devices manufactured in countries with less-strict emissions testing requirements/enforcement, but it's possible due to slight defects in almost any device. [Source: I design RF receivers for a living.] Now suppose that this noise happens to be on the localizer or glideslope frequency for the runway to which the aircraft is flying an approach. Hopefully you're starting to see a problem here... Whatever amplitude changes are happening on this unintended emission are now being received by the AM demodulator of the localizer or glideslope, potentially confusing it and, in low visibility conditions, causing the aircraft to be directed somewhere other than the runway threshold. Needless to say, that's bad.

Boeing recommends the following actions for flight crews flying ILS approaches in order to detect erroneous ILS readings:

Crosschecking altitude and DME distance periodically.
Crosschecking altitude and flight management system (FMS) threshold distance.
Crosschecking altitude and the crossing altitude of the outer marker (or locator, very-high-frequency omnirange [VOR] navigation equipment, or FMS).
Crosschecking radio altitude and barometric altitude.
Crosschecking ground speed and rate of descent.
Questioning air traffic controllers when indications do not appear to be correct.

However, even when following those instructions, slightly erroneous ILS signals may be hard to detect until too late. If a DME is showing that you're half a mile off, you can probably notice that, but a couple hundred feet off might not be noticeable (but is still plenty to be a big problem.)


Is the heading used near the pole? If I understand correctly, heading is usually measure relative to the pole (either magnetic or true). Traveling at a constant heading can't be approximated as travelling straight ahead when near the pole. The extreme case being heading to 180° and crossing the south pole.

Althought there are not many aircraft in this situation as explained in this question, using the heading may not be relevant.
How is the navigation handled is such area? Is the heading used?

Near the poles 'polar grid navigation' is used. By placing a rectangular grid over the pole, aligned with the prime meridian, a local coordinate system is created. Aircraft fly constant grid courses near the poles.

For your example crossing the south pole approaching over the prime meridian the true course will change from 180° (T) to 000° (T), but the grid course will remain 180° (G) all the time.

Grid courses and true courses can be converted easily, this youtube video explains it nicely (although he gets the grid track in the wrong direction in the end, it should be 110°(G) instead of 290°(G))


Sub-ideal Autorotation in Rotorcraft I have another AuRo question for you.
When a Helicopter autorotates (ideally) it is in the turbulent wake state and there is virtually no flow through the rotor disk (figure of Leishman attached). Now, when Vc (descent speed) is roughly -1.8 times vh (induced velocity at hover) the vehicle is considered to autorotate ideally.
What if we do not autorotate ideally? Does the vehicle still have to be in turbulent wake state?
The real question: Is autorotation (and thereby maintaining of an ideal rotor rotation speed) possible in the windmill break state?
For instance, in the work of Dalamagkidis the OHA58 (Chapter 5.1.1) and the Raptor30v2 (Chapter 5.3.1) do not seem to be in turbulent wake state.
As for my calculations, vc/vh was always slightly lower than -2.
However, the vehicles seem to perform well and land softly.
So is the windmill break state a legitimate state for "autorotation"?
Thanks for helping me out! :)

Autorotation in helicopters is rarely ideal, with net rotor torque = 0, because some energy is drained from the turning blades to feed the tail rotor.
There's, however, a continuum between the ideal 'autorotation' and the 'windmill brake state/moulinet frein'. The 'point of ideal autorotation' should be taken as the 'point of minimum'. For any increase of the load (the weight of the gyro, for instance), from that point on, there's a multitude of possible equilibrium points in autorotation along that curve of 'windmill brake state'. Real-word autorotation is always in one of those points, and never at the 'point of ideal autorotation'...  You may find useful this illustration and text. Source included.


How close is an obstruction allowed to be in an instrument approach? Inspired by this answer, and the comments that followed.

City politics aside, i.e. hypothetically, can KBOS rwy 14 be used for landing aircraft that don't comfortably need more than 5,000 feet of runway?

The issue arises from the building at the approach end of rwy 14.

The building is 174 ft. tall, lighted, 1364 ft. from runway, and 70 ft. left of center line.

The RPZ (protected zone for excursions) by FAA standards is 1000 ft., which the runway meets.

FAA also says the OFZ (Obstacle Free Zone, the 3D area covering the approach end) would only be 200 ft. since there is no Approach Lighting System installed.

In summary, imagine the building is a rocky outcrop somewhere in a desert, and someone built a 5000-foot runway the same distance from it as KBOS 14, can it be legally used?

Visually I don't see why not, but I'm not an FAA administrator. And for an instrument approach I also don't see a problem stepping down to a specified MDA, and even at an angle (LDA).

To raise the stakes a bit, I believe a DC-9 can comfortably land on a 5000-foot runway. Let's use a DC-9 or similar type in the example above.

To make the answer less stressful, if you know of a similar airport/obstacle scenario, or can find one, with a published approach, let us know.

FAR Part 77 provides standards for what objects constitute an obstruction to navigation:

200 ft. above ground level or 200 ft. above the airport elevation (whichever is greater) up to 3 miles (for runway lengths > 3200 ft.) from the airport.

Increase 100 ft. every mile up to 500 ft. at 6 miles from the ARP (airport reference point)

500 ft. or more above ground level at the object site
Penetrates an imaginary surface (a function of the precision of the runway)
Penetrates the terminal obstacle clearance area (includes initial approach segment)
Penetrates the enroute obstacle clearance area (includes turn and termination areas of federal airways)

There are 5 imaginary surfaces:

Primary - aligned (longitudinally) with each runway
and extends 200 ft. from each runway end
Approach - longitudinally centered with the runway and extends beyond the primary surface
Horizontal - horizontal plane 150 ft. above the established airport elevation. Constructed by swinging arcs around the end of the primary surface
Conical - 20:1 slope surface extending beyond the horizontal surface
Transitional - constructed to join approach and horizontal or approach and transitional surfaces

Additional dimensions are also dependent on the types of approaches used at the runway. A precision instrument runway has a primary surface 1,000 feet wide, and a horizontal surface radius of 10,000 feet. Approach surface width at end is 16,000 feet, total approach surface length is 50,000 feet, and slope is 50:1 for inner 10,000 feet and 40:1 for the additional 40,000 feet.

The idea is that the FAA is notified of any new obstacle that meets the criteria above, and it is up to the FAA to provide a determination of how it will affect procedures. If an obstacle cannot avoided, special procedures may be required.

For the specific example of Boston's runway 14, using the most conservative visual approach clearance requirements, the obstacle is well within the imaginary surfaces:

The primary surface is 250 feet wide for a visual runway and gets wider through the approach section, so at 70 feet from center line, this building will be within that zone.
The approach surface for a visual runway is 5,000 feet long, so at 1364 feet the building will be within that zone.
The approach slope for a visual runway is 20:1, which is a height of 58 feet at a distance of 1364 feet from the runway, so the building at a height of 174 feet is well into that zone.

The runway would need a displaced threshold of at least 2320 feet to clear the building for a visual approach. This would mean you could only use runway 14 for visual approaches, and there would only be 2680 feet remaining. You could use it for non-precision instrument approaches but only with propeller driven aircraft of 12,500 pounds maximum gross weight and less. Anything more than that, and the approach slope gets even more shallow.

Note that other runways at BOS list obstructions as well, but all others list the slope to clear the obstacle. Runway 14 would have about a 6:1 slope to clear that building. Runway 4R/22L has slopes of 8:1 and 7:1 respectively to obstacles, but is also twice as long, allowing for a displaced threshold.


Which engine is more efficient between turboprop vs jet? Are turboprops really more efficient than jets?

If yes, does that mean that airlines who use jets sacrifice fuel for faster flights?

The short answer to both your questions are Yes. The long answer is, it's not so simple.

The ATR 72 you have pictured has a top speed of 276 knots and a range of 1,300 miles. It can carry around 70 passengers.

This document provides detailed comparisons of burn rates. So we can see the ATR 72 burns about 810 Liters per hour (about 214 gallons/hr). A Boeing 737-400 seats about 150, has a maximum range of about 2,400 miles, and a cruising speed of about 473 knots (almost double the range, and over 1.5 times the speed). But its burn rate is about 3,000 liters per hour (793 gallons).

So is it a strict trade-off? Speed for Efficiency? Well, not entirely.

TAS is true airspeed. That is, the speed of the aircraft relative to the airmass in which it is flying. However, an decrease in density (e.g. high altitudes; air is less dense) will yield an increase in TAS. Thus, it is easier to fly at the same true airspeed at higher altitudes. Since jets are generally used on longer flights (where much of the time in the air is spent at high cruise altitude), they have to work less to fly the same speed as they would 10,000 feet below. There are other reasons why jets are more efficient at high altitudes - they have to combine less fuel with the thinner air, and there is less drag at high altitudes.

So why don't propeller planes fly at high altitudes then? Well, part of it is that turboprops are less efficient at higher speeds and higher altitudes, and jets (turbofans) are more efficient at both (obviously to a point, but airliners don't fly fast or high enough to decrease their efficiency again).

Since jet engines can also produce more thrust, they are better suited to large airplanes, which are the ones used for long distances (e.g. if you wanted a propeller plane the size of an Airbus A380, you would need a lot more than 4 engines). So jets are used in situations where they are more economical, and props where they are more economical.

In summary:

Turboprop characteristics

Efficient at low speed, low altitude
Low thrust

This leads to smaller aircraft on shorter, slower routes, like you've observed, since they don't have to climb or fly fast to get there in a reasonable amount of time. Also these short hops generally require fewer passengers, or flying a second flight is better than needing a much bigger plane.

Turbofan characteristics

Efficient at high speed, high altitude
High thrust

This leads to larger aircraft on longer, faster routes, like you've observed, since they need to fly higher and faster to get there in a reasonable amount of time. Also since these routes are more "popular", and it costs so much to fly that far, it makes more sense to put more passengers on one plane, than two.

In general, an airline would not sacrifice fuel for faster flights if that was the only advantage, unless they knew there could be a price premium for the faster flight (e.g. Concorde).


Could the non-smoking sign still be turned off in modern airplanes? Yesterday, I flew on Germanwings 4U2379 with an Airbus A319. The plane's interior looked pretty modern, and while I can't find a construction year online, I'm pretty sure it was built way after the total smoking ban.

This plane still had illuminated non-smoking signs though and I was wondering if the crew would actually be able to turn these off during flight if they wanted to. Is there any information about that?

This question shows that some planes do not even have a non-smoking sign anymore, but it does not elaborate on the mechanics of existing signs.

It would appear that the aircraft you flew was D-AGWR, a A319 with MSN (Manufacturer Serial Number) 4285 delivered in April 2010 (hence fairly new).

There is a switch at the bottom of the overhead panel, next to the seat belt sign, slightly right of the middle. Flip it and they will extinguish. The functionality is a bit more complicated than it would appear, since it feeds into the central aircraft electronics.

Olivier Cleynen at Wikicommons

Out of interest, this button no longer exists on the Boeing B787, suggesting that it is on the way out. Only the seat belt option remains.

The slots for no smoking are being increasingly 'redeveloped' into a sign for electronic devices instead on some types. They just put a no smoking sticker on the seat in front of you to fulfil the same function. I do not know if they cockpit text has been modified on the aircraft that undergo this modification.

Source


Are planes assigned different climb angles from the airport by the tower? Clearly the angle at which planes take off and climb depends on lots of things (mountains, residential area, aircraft type, wind) but when watching planes take off after another from the same runway, I have the impression that similar aircraft climb at different angles right after another.

So I'm wondering it this is a measure to increase the distance between two planes quickly after they leave the airport? Such that every other aircraft is asked to leave flat'ish (within what the plane and regulations allow) and others more steeply?

The question occurred to me at GVA (single commercial runway).

This is about the initial climb angle, not their course heading.

There can be many reasons. Flights taking off one after another:

have different destinations
have different weight and balance
have difference in wings and wingtips
have pilots with difference in skills
got different takeoff directions by ATC
are trying to avoid wake turbulence

Off all the reasons I mentioned above, perhaps wake turbulence might be playing more role about difference in takeoff angle. There are a ton of questions about wake turbulence, which is worth a read.


Are test pilots who work for the FAA paid on the GSE pay tables? Many employees of the US federal government are paid according to the GSE salary tables. Are the FAA test pilots paid on the same table? For example someone could be in the grade 14 step 6 rate. Or, are they paid according to some other pay table?

Yes, FAA test pilots are paid based on the General Schedule for the levels of GS-1 through GS-18.

If you are interested in reading the job description, one can be found on AvJobs.

The relevant section for pay is this one:

  Wages and Benefits

  Most Federal Civil Service employees in the aviation field are covered by the General Schedule and their salaries vary according to their grade level (GS-1 through GS-18). Within each of the grades provided in the General Schedule, provision is made for periodic pay increases based on an acceptable level of performance. With an acceptable level of competence, the waiting period of advancement to steps two, three and four is one year, steps five, six and seven is two years, steps eight, nine and ten is three years. The starting grade is normally GS-7. Trainees are paid while learning their jobs.

  The entry level is GS-9. Entrance salary will vary with the degree of the applicant's experience and training.


What does the term "tanker" mean when used in regards to a passenger airliner? In a comment on this answer:

  Airlines will tanker fuel if it's substantially cheaper at another airport

I've wondered what that term meant before, and now this comment leads me to think that airliners will carry more fuel than what's required for a trip, because carrying the fuel might be cheaper than buying it at the next airport.

Can someone provide more detail on why and when an airline might do this, the calculations that are involved, and any other interesting information on this topic?

Since the 1960's and 1970's when political hijackings were a problem, airplanes started to only carry the fuel required for the flight.  This means a typical fuel load will be something on the order of:

taxi fuel at the departure airport
fuel to fly and land at the destination at a given altitude and forecast winds
if an alternate is needed:

fuel to fly to the alternate airport

45 minutes of reserve fuel
perhaps a bit extra for contingency and to keep captains happy (e.g. 5-15 minutes worth of fuel).

For a normal flight this means you'll land with around 45-60 minutes of fuel on board, sometimes less.  You'll fill up for the next leg at this airport while you deplane and enplane passengers.

Fuel at the hub airports is sometimes a bit cheaper due to the fuel contracts the airline can secure when they order massive amounts of fuel every day.  Fuel at outstations that don't see a huge volume of fuel may be quite a bit more expensive.  In this case, and if your weights allow, the airline may elect to load extra fuel that isn't needed.  The purpose of this is so you do not need to buy as much fuel at higher prices at the outstation.

I only saw this happen operationally when we were going to be very light and the outstation fuel was very expensive.  Usually our loads were high enough that we were struggling to get all 50 passengers, bags, and especially jumpseaters on board with the required fuel load.  In that case it would not be economical to take more fuel because we'd have to take fewer passengers.


Will Tower repeat an initial heading if it's part of my IFR clearance? If I get an initial heading to fly in my clearance from Clearance Delivery, but the Tower controller does not repeat the heading to fly in my takeoff clearance and I stay on runway heading, can the FAA take enforcement action against me (aka did I do something wrong)?

Is the Tower controller obligated to repeat the heading to fly in my takeoff clearance, or is it expected that I do what was in the clearance issued to me?

Yes, the FAA can and will take action in that scenario. I know because it happened to me :-)

A couple of years ago I was departing IFR from KPDK and my clearance included a right turn after departure. It was a busy and very hot day and I had to sit and hold for release (in a C182 in 100F heat...), so when Tower offered to get me out if I could depart immediately, I jumped at it. Tower cleared me for immediate takeoff without repeating the right turn instruction and I forgot about it in the rush.

I climbed out on runway heading and I started thinking that Tower was waiting a long time to turn me over to Departure. When they did, Departure told me to turn right immediately but I had to say "unable" because I now had obstacles to my right. I was vectored back on course and Departure asked me twice what the Tower had cleared me for, so it was obvious that something had gone wrong although they didn't give me a "possible pilot deviation" warning. Fortunately I was never close to busting the ATL Bravo.

I got home, listened to LiveATC, realized that I'd forgotten the right turn instruction, filed an ASRS report and forgot about it. 89 days later the FAA called to investigate (they have 90 days to act) because ATL Approach had reported it as a "course clearance deviation". Long story short, after a couple of calls and emails they dropped the whole thing without any record because they said it was a trivial incident and I'd shown a positive and "compliant" attitude with them. Although I have to imagine that if I'd busted the ATL Bravo or caused a loss of separation, the outcome might well have been different.

I don't know whether Tower is required to repeat the initial heading instruction (it may be in the ATC Orders), but my experience certainly shows that you can't rely on it. I commented in my ASRS report that if Tower had repeated the instruction it could have helped to prevent the whole issue.


What software is used for aerodynamic wing shape optimization? I can see lots of research articles around aerodynamic shape optimization of airfoils and wings like this MDOlab program. But all stuff like that don't seem to be available for a simple customer. Personally I've not seen where I can buy or download it. The only programs for that purpose that I've managed to find are:

Tosca Fluid (not adapted specifically for the airspace industry)
ANSYS Adjoint Solver (probably OK, don't know yet)
This Python code coupled with XFoil, but it's primitive and only for airfoils, not for wings.

Somebody know some accessible software for shape optimization of airfoils and wings for an ordinary engineer, but not for scientists or programmers?

If you follow the AIAA publication number (AIAA-2014-0567) given in the first frame of the linked video, you will find this article which explains in detail that the optimisation shown in the video was done on MACH:

  These tools are components of the framework for multidisciplinary
  design optimization (MDO) of Aircraft Configurations with High
  fidelity (MACH). MACH can perform the simultaneous
  optimization of aerodynamic shape and structural sizing variables
  considering aeroelastic deflections.

If you now google for MACH, you will find this article by Gaetan Kenway which explains in detail how the software works. But this is not what you want, my impression is you need a simple to use software which can be downloaded and run within minutes.

My recommendation would be XFLR5 which incorporates the XFOIL airfoil solver and adds modules for designing and calculating the whole aircraft. YouTube has a variety of tutorials available. Is that what you want?

However, a basic understanding of aerodynamics and the possibilities and limitations of the algorithms used will be very helpful - a good engineer should be able to think both like a scientist and a programmer.


How to adjoin wing skin to wing ribs? I saw a youtube video (from a channel called Real life guys) where gum was used to join the ribs of their homemade plane to the skin and I saw another video where the wing skin(tedlar) was literally sown to the ribs of the wings,my question is what is the appropraite way to join the  wing skin(tedlar/mylar)to the ribs?

The FAA offers a nice handbook on wing skin covering for fabric aircraft you can find here. They list, clips, screws, rivets and lace as the joining methods

(source)

  Rib Lacing Cord

  Rib lacing cord is used to lace the fabric to the wing
  ribs. It must be strong and applied as directed to safely transfer
  in-flight loads from the fabric to the ribs. Rib lacing cord is
  available in a round or flat cross-section. The round cord is easier
  to use than the flat lacing, but if installed properly, the flat
  lacing results in a smoother finish over the ribs.

In some cases, or even in adition to other methods fabric cement may be used.

  Fabric Cement

  Modern fabric covering systems utilize special fabric
  cement to attach the fabric to the airframe. There are various types
  of cement. Figure 3-9In addition to good adhesion qualities,
  flexibility, and long life, fabric cements must be compatible


FAR 91.215-- may an aircraft with no electrical system and no transponder overfly Wheeler AAF at 9500' MSL? Here are some of the airspaces where FAR 91.215 requires aircraft to have transponders--

  (b) ...

  (2) All aircraft. In all airspace within 30 nautical miles of an
  airport listed in appendix D, section 1 of this part from the surface
  upward to 10,000 feet MSL;

  (3) Notwithstanding paragraph (b)(2) of this section, any aircraft
  which was not originally certificated with an engine-driven electrical
  system or which has not subsequently been certified with such a system
  installed, balloon or glider may conduct operations in the airspace
  within 30 nautical miles of an airport listed in appendix D, section 1
  of this part provided such operations are conducted -

  (i) Outside any Class A, Class B, or Class C airspace area; and

  (ii) Below the altitude of the ceiling of a Class B or Class C
  airspace area designated for an airport or 10,000 feet MSL, whichever
  is lower; and

Consider the airspace near Honolulu International Airport (now Daniel K Inouye International Airport), HNL/ PHNL.  (Link to sectional chart.)

May an aircraft with no engine-driven electrical system operate at 9500' MSL directly over Wheeler AAF (HHI/PHHI)?

This airspace is within one of the 30-nm Mode C veils described in FAR 91.215 (2).

The intent of the question is to ask whether the "Below the altitude of the ceiling of a Class B or Class C airspace area" clause of 91.215(3)(ii) applies only within the actual lateral boundaries of (i.e. within, above, or below) Class B or C airspace, or throughout the 30-nm circle.  Wheeler AAF is within the mode C veil for HNL, but beyond the actual lateral boundaries of any of the Class B airspace.  The ceiling of the Class B airspace at HNL is 9000' MSL.

See also related question FAR 91.215 (b)(3)(ii) -- transponders-- does the "or below 10,000' MSL" clause have any practical significance?

Yes, the following statement indicates that aircraft without electrical systems may penetrate the mode C veil at any altitude (presumably excluding cases where the penetration would immediately bring them into Class B or C airspace, or would immediately place them above underlying Class B or C airspace):

  "The practical effect of paragraph (b)(3) with respect to your
  question is that it allows non-equipped aircraft to enter the
  30-nautical mile circles surrounding Appendix D, Section 1 airports
  between the surface and 10,000' MSL and to operate beneath the floors
  of the associated Class B airspace..."

From this page 2 of this 2006 interpretation from the FAA Office of the Chief Counsel.


Why don't aircraft owners put vortex generators on the top of their flaps to extend single flap lift creation past 40 degrees? Why don't ultralight/LSA aircraft owners put vortex generators (VGs) on the top of their flaps?
I understand that the maximum flap angle for a single lift creating flap is 40°, but 80° with a double flap, if each flap is rotated at 40°.
Why not put VGs on the top of a single flap to increase its maximum lift creation angle, and thus lift, to 45°, 50° or maybe even 60°, which would allow for a slower landing speed, hopefully in the 15-20mph range?
While Vg's might have been designed for wings, they are now used for elevators as well, which is very similar to an upside down wing and flap.  See picture below. Source: Zenith

Because the separation bubble, that vortex generators attenuate, occurs in front of the flaps.  There's no advantage to putting VGs that far back, on an ultralight or any other fixed wing aircraft.


Who decides whether an airline docks at a jetbridge or parks at a remote stand? A trip I took led me to wonder how airports/airlines decide when to allocate a gate and when to board out on the apron.

Yesterday, I flew TLV-IST-BOS on Turkish Airlines. At the start of the trip, I briefly wondered if we were travelling to Istanbul (IST) by bus. The airplane was parked far from the gate.

We got to IST, and, once more to ride the bus. In this case, we parked at jetway, but we were sent down the stairs and onto a bus. Turkish sure is a big, legacy airline at IST.

And, to complete the process, our A340 for Boston was parked half-way to Europe, and reached by a bus.

What determines all this? Bad luck? Plane size?

This can depend on all kinds of things, so it's hard to give a definitive answer:

Many low-cost airlines park at remote stands as this is cheaper than parking at a jet-bridge.
Some airports have jet bridges that can't handle particular aircraft types (often large aircraft at small airports) and therefore these aircraft must park at remote stands.
Related to the above, some airports have no customs facilities for jet bridge arrivals (or vice-versa) and therefore international flights must be parked at a remote stand and passengers bussed to customs/immigration.
Sometimes a flight will be allocated a jet bridge in advance but then suffers from a delayed arrival. By the time it gets to the destination the jet bridge that was assigned to it is taken by another aircraft. In this case, the aircraft may have to be parked at a remote stand.
As you say, bad luck can play a role. Airports have a limited number of jet bridges and sometimes there's just no space for your aircraft.
Lastly, in my experience it is particularly common to get a remote stand if you arrive late in the evening: Some airlines like parking remotely in this circumstance as it's cheaper than parking overnight at a jet bridge.

As I said, it's hard to give a definitive answer but the above are some common causes for being placed at a remote stand.


How do you know what equipment code to put on a flight plan? Every time I have flown and filed flight plans the CFI or the person I have rented the plane from has told me what equipment code to put on the flight plan. I am curious how you would figure out on your own. Is it in the POH?

Basically you know what equipment is installed on the aircraft (and in working order), and that's what you enter on the form.

For FAA flight plans, there's a list in the AIM (It's table 5-1-3).
Generally for domestic flight plans you file the "best" equipment you have onboard in working order.

FAA "Domestic" flight plans are eventually going away though, and we'll be expected to use the ICAO flight plan format (including its equipment codes).
ICAO equipment codes are a little more complicated because the "Equipment" box lets you list a whole lot more stuff (and the more you enter the more ATC knows in the event of an emergency): Basically you list all the equipment you have in working order under the equipment box on the ICAO flight plan form.
Lists of ICAO equipment codes is available (the one on Wikipedia is pretty complete), and there are handy wizards floating around that let you check boxes and get the string you need to enter on the flight plan.

Look at two hypothetical aircraft, both identical Cessna 172s with different equipment to see how it works:

Aircraft #1 has a VHF Nav/Com (VOR only, no ILS), DME, GPS, and Mode C transponder.
This aircraft would file /G on a domestic flight plan, and DGOV/C on an ICAO flight plan (the ICAO flight plan may also include R and an appropriate PBN code for the GPS capability).
Aircraft #2 has a VHF Nav/Com with ILS capability, and a Mode C transponder.
This aircraft would file /U on a domestic flight plan, and SV/C on an ICAO flight plan.

Note that the ICAO flight plan gives ATC more information to work with:
If Aircraft #1 calls up and says their GPS died ATC knows they can assign them clearances that use VORs and DME for navigation, but that the aircraft cannot accept an ILS approach at their destination.
Conversely if working off a domestic flight plan ATC will have to ask the pilot what their navigation capabilities are (or they may assume "standard" equipment including an glideslope receiver and ILS capability and offer the pilot an ILS approach only to be told "Unable ILS" by the pilot).


Why can't I build an entire jet engine out of carbon fiber? I noticed that most jet engines are made out of aluminum or metal components. However, carbon fiber has a melting point of 3500 degrees celcius, way above metal or aluminum. So, can I build an entire jet engine out of carbon fiber?

No, you can not. Carbon fibre composites always contain a matrix component which serves different functionalities, but (in a micro nutshell) bonds and keeps the fibres in place. What you get is a very complex material with lots of lightweight potential, but also very different property profiles compared to metals.

Most matrix materials (thermoset, thermoplastics) will not work up to engine (combustion chamber) temperatures and either degrade/burn or melt/vaporize/burn long before reaching even a meagre few hundred Kelvin (say, 500K). In fact, carbon fibres will not work as well in an oxygenated high-temperature environment, and degrade/burn up as well.

One composite material that works and is used already in engines are ceramic matrix composites, like (amongst others) e.g. C/C-SiC structures, but those are very special animals (and even there the carbon fibre parts are susceptible to burn). Especially in terms of mechanical properties, these cannot compete with superalloys.

But also for many other, ambient temperature parts, metals are much better suited. Think of example of a ball bearing - doing that completely in composite will not work really well (if at all).


What types of non-permanent GoPro mounts exist for the ceiling of a Cessna 172? What alternatives are available to using a permanent mount to place a GoPro on the inside ceiling center of a Cessna 172?

I do tests on truck aerodynamics, and occasionally we put tufts on the vehicles. We then film these tufts to see how the flow behaves. We also use these RAM mounts, but sometimes one of them would come undone due to unproper mounting, dirt or flexing of the surface.

We solved this issue by adding redundancy in the form of the Rollei 3x Suction Cup Kit:

Disclaimer: Not affiliated to Rollei, this is just the first one we found.