Questions tagged [fuel-systems]

Any question regarding aircraft fuel systems, how they work etc.

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85
votes
5answers
20k views

Why do we need to starve the engine before turning it off?

This question is for Piper Tomahawk, but I guess applies to any small aircraft. Why do we need to use the fuel mixture to starve the engine before turning it off with the key? Why can't we just turn ...
71
votes
6answers
26k views

Why are fuel tanks in the wings filled first, and why are they used last?

When fueling airliners, why is fuel filled first in the tanks in the wings and then the center tanks? And why do they use fuel from the center tanks first and then from the tanks in the wings? From ...
53
votes
9answers
37k views

Why are fuel tanks located in wings?

Passenger aircraft have fuel tanks in the wings. Why? What are the advantages and disadvantages of this location ? examples of disadvantages I would suspect: added weight increases the structural ...
52
votes
4answers
9k views

Why do many GA aircraft not have a “Both” fuel selector?

I've been trying to rack my brain around this and asked a few CFI's who couldn't give me more than "because that is how it was done", but a good number of GA aircraft save for Cessna and maybe a few ...
40
votes
6answers
11k views

Is fuel moved around during flight on a passenger or cargo plane? If so why?

Is fuel moved around during flight on a passenger or cargo plane? If so why? Is balance an issue?
30
votes
5answers
19k views

Why didn’t the Captain of Cathay Pacific flight 780 shut down engine 1 and land with a more reasonable speed?

In the approach phase, engine 1 of Cathay Pacific flight 780 got stuck at about 70% N1 and it forced the crew to do an overspeed landing (230knots). Why didn't they shut it off by turning the fuel ...
25
votes
4answers
9k views

Why are the center tank pumps deactivated when slats are extended on the A320?

Why are the center tank pumps deactivated when slats are extended on the A320? I researched about this and all I can see is hints. They say it is because of regulations or certifications.
23
votes
6answers
5k views

Is there a tank priority sequence for using the fuel tanks?

Is there a tank priority sequence for using the fuel tanks, or does the pilot decide?
18
votes
2answers
1k views

How is fuel managed in the Zero-G A310?

There are several Zero-G airplanes to experiment briefly microgravity without going into orbit. One is the A310 from Novespace (F-WNOV): Novespace A310 F-WNOV (source: Jonas Wirz at Airplane-Pictures....
17
votes
5answers
6k views

Why aren't “fuel polishing” systems removing water & ice from fuel in aircraft, like in cruising yachts?

Should you sump fuel tanks when the fuel system is below freezing? the question should one sump fuel-tanks before flying, if in freezing-conditions? but this implies another question that boggles me:...
17
votes
1answer
2k views

How does the fuel pump work in a PA-28 and when should I use it?

Just started flying again after 14 years and I'm taking this to the finish line this time. All my time, up till 10 am today, is in a C172. I did fly a PA 28-151 today and liked it. I do have some ...
16
votes
4answers
7k views

Why do jet engine igniters require huge voltages?

Wikipedia's Components of Jet Engines has this to say on the igniters: A high voltage spark is used to ignite the gases. The voltage is stored up from a low voltage (usually 28 V DC) supply provided ...
16
votes
3answers
9k views

Is excess fuel leaking normal during take off of a B737?

When we look over this video it's noted that some fuel is coming off from the left wing during the rotate. This is the position of the fuel vent within the wing, ...
16
votes
1answer
4k views

Why is fuel used as a hydraulic fluid?

Why is fuel used in some servo-systems as a hydraulic fluid (fueldraulic systems) of modern civil and military aircraft such as the Boeing 777-200/-300 (Pratt & Whitney PW4084) or the Lockheed ...
15
votes
4answers
8k views

What is the purpose of the fuel shutoff valve?

Most GA planes have a fuel shutoff valve which I don't quite understand the purpose of. Does it cut the fuel flow with the mixture. My theory is to prevent fuel flow at earlier stage for safety ...
15
votes
5answers
6k views

What could the fuel pump failure have been that my flight experienced?

I was on an Easyjet flight (I think an A320), when mid-flight, I overheard a member of cabin crew tell another passenger there was a 'technical' issue with the aircraft, that might make us slightly ...
15
votes
3answers
2k views

What is the appropriate fuel tank selection to land a 172?

On a recent checkout on a C172 I was told to select "fullest tank" as opposed to "both" that I have been doing for years. Given the aircraft is high wing (gravity feed) with no auxiliary fuel pump ...
14
votes
2answers
2k views

Why nitrogen generation system is only present in centre tank only?

I was going through FCOM of A320 and it mentioned that nitrogen generation system is only there for centre tank and not for wing tanks what is the reason for the same?
12
votes
5answers
8k views

Why is mixture lean recommended on the ground?

Mixture lean is typically recommended during the ground operations at sea-level pressure in the POHs of most small aircraft equipped with a carburetor system. Why is it? I heard some people saying it'...
12
votes
2answers
3k views

Why fuel left/right when C172 is secured?

The C172 POH checklists say to set the fuel selector to "right" or "left" when securing the plane but "both" while operating the plane. What is the point of changing the fuel selector when the engine ...
12
votes
1answer
441 views

How do fuel trim and air bubbles prevention work in inverted flight?

I was reading Why do many GA aircraft not have a "Both" fuel selector? and voretaq7's excellent answer got me to thinking. He cites the regulations noting that the plane must only draw fuel from one ...
11
votes
4answers
2k views

Is there any work on improving fuel tanks so they could store hydrogen?

I think that hydrogen is among the best fuels for use in supersonic and hypersonic flight, is there any work on improving fuel tanks so they could store hydrogen? What would be the best state to ...
11
votes
2answers
675 views

What are possible explanations for fuel being expelled in this video?

In another question, I asked about whether or not a fuel spill would be reportable or not. The answer was "no", because the aircraft was not in flight. What are the possible causes of the spill ...
10
votes
1answer
2k views

Why would the outer tanks fuel on the A320 be colder than the inner tanks?

I have noticed in a number of instances during long flights typically over 5 hours the fuel in the outer tanks on the A320 are colder than the fuel in the inner tanks. This goes against the system ...
9
votes
4answers
3k views

How do you know which fuel an aircraft uses?

Other than the decals on the plane, how would you know what fuel to use in an aircraft? Where is this limitation documented? For some aircraft, does this limitation include some sort of substitute ...
9
votes
3answers
254 views

Why don't all cylinders have priming lines?

Questions about the primer for carburetor engines. Why does the primer only spray fuel to three (sometimes just one) of four cylinders. (Like Piper Cherokee or Seminole) And is it true that priming ...
9
votes
1answer
169 views

How is the fuel quality monitored/assured for jetliners?

With tens of thousands of flights daily, many out of smaller and perhaps 'sketchy' airports, it would seem that serious incidents caused by contaminated fuel should happen a lot more often (in a quick ...
8
votes
1answer
357 views

Why was the Graf Zeppelin's endurance when fully fuelled with both fuels less than the sum of its endurances with each fuel separately?

The LZ-127 Graf Zeppelin used a unique dual-fuel system, with both a gasoline tank and a set of gas cells filled with blau gas; the airship could be flown using either fuel or both. The purpose of ...
8
votes
2answers
454 views

How can the fuel decrease evenly from both wing tanks when an A320 is running on APU only?

I stumbled over this sentence in a training material about fuel leak: "If the fuel quantity symmetrically decrease in both wing tanks and the fuel quantity in the center tank decrease, the fuel leak ...
8
votes
1answer
328 views

Can IPA be used as a FSII with MoGas, particularly with a Peterson STC?

This question established a basis for the use of 100% Isopropyl Alcohol (IPA) as a Fuel System Icing Inhibitor (FSII) in aviation gasoline systems. However, this Cessna Service Letter documents that ...
7
votes
1answer
2k views

How does the FAA define fuel capacity for ultralights?

Ultralights under FAR 103 are regulated to a capacity of 5 gallons. I'm wondering how exactly fuel capacity is defined, does it include fuel in the lines, and in the carburetor bowl or elsewhere or ...
7
votes
5answers
1k views

Why is alcoholic gasoline such a showstopper for aviation?

One of the main reasons the common avgas grades are still full of 3-plumba-3,3-diethylpentane is the incompatibility of many aircraft fuel systems with the oxygenates (primarily ethanol, with some ...
7
votes
1answer
810 views

Does the mixture and throttle setting affect the quality of priming of fuel prior to start?

This question is a generality. For airplanes with small reciprocating engines, does the mixture and throttle setting at the time of priming affect the quality of the priming or the engine start, or ...
7
votes
1answer
2k views

What is the freezing point of 100LL Avgas?

Does anyone knows the exact freezing point of Avgas (100LL) ? I found that Jet A-1 freezes at −47 °C / −53 °F (wikipedia), but didn't manage to find any info on Avgas.
7
votes
1answer
548 views

Can you safely operate a 777 with diesel?

Is it possible to safely operate a Boeing 777 on diesel instead of Jet-A? Are there any regulations that prevent this? Would it cause any damage?
7
votes
1answer
2k views

Why not leave an electric fuel pump on all the time?

This question is related to single-engined piston airplanes equipped with an electric fuel pump like the Piper Dakota/Arrow etc. The POH states that the fuel pump should be switched on for takeoffs/...
6
votes
1answer
424 views

How is that there is no leak through the fuel vents during aerobatics maneuvers?

Can anyone tell me how aircraft such as jet fighters and stunt planes design the fuel tank vent system to prevent fuel leaking through the vents when performing aerobatics, 360 flips and complex ...
6
votes
1answer
452 views

Has fuel boiling ever been an issue for high altitude aircraft?

Are special measures being taken to prevent fuel from boiling inside the fuel systems at high altitudes? If so, when (with what aircraft) did this practice start? (question is pertaining to air-...
6
votes
1answer
442 views

Where is fuel metered in continuous flow fuel injection system?

How is fuel metered in continuous flow fuel injection system?
5
votes
2answers
2k views

Why does pulling the mixture to idle cutoff increase the RPM slightly?

When adjusting fuel control on a reciprocating engine, why is there a slight RPM rise (50-RPM rise) when pulling the mixture control to idle cutoff? Why if more than a 50-RPM rise, carburetor is set ...
5
votes
1answer
856 views

How does a hot tip-jet supply fuel to its engines?

Some tip-jets move their rotors by running jet engines on each end of the rotor. Obviously there must be some ways to supply fuel to those engines through a rotating body. How is this accomplished?
5
votes
3answers
875 views

What causes fuel gauges to be untrustworthy?

I went on my first flight yesterday (Cessna 152), and I was told not to trust the fuel gauges and to check fuel levels manually. The instructor said that the only fuel gauge reading that I can trust ...
5
votes
1answer
588 views

How much unusable fuel is in the A320?

I was wondering how much unusable fuel is in each tank or maybe in total for an A320. I searched through the FCOM and could not find answers. To add to this question is the fuel shown on the fuel SD ...
5
votes
1answer
2k views

Why does fuel vaporize in the carburetor?

So I get that a carb vaporizes fuel and mixes it with the air intake for the engine. But my question is what is the explanation for what causes the fuel to vaporize after it exits the fuel nozzle?
5
votes
2answers
4k views

Why does fuel vaporization in a carburetor cause a temperature decrease rather than a rise?

So I know the most "prominent" conditions of carburetor icing is anywhere from 20 to 70 °F with visible moisture. There is also a tendency to have icing in the carburetor in the venturi throat due to ...
5
votes
2answers
299 views

Could hydrazine be used as a scramjet propellant?

Hydrazine is used a monopropellant in Satellite OMS rockets. But interestingly enough, it's highly exothermic decomposition into ammonia, nitrogen, and hydrogen provides heat for an endothermic ...
5
votes
1answer
3k views

Where is the fuel vent on a Piper Archer TX?

I realized I haven't really noticed where the fuel vent is for the 2016 Piper Archer TX that I've flown, but I assume the fuel is vented from the fuel cap. Is that correct?
4
votes
2answers
824 views

Do Diesel engines have a mixture option?

Consider the DA-42, it has no mixture control. Is that because it is run on Jet-A/diesel? Or is the mixture control automated?
4
votes
2answers
2k views

Where is the APU fuel pump on the A320?

I'm looking for APU fuel pump location for A320 aircraft series. I'll be much appreciated if you provide a link to some images, schemes.
4
votes
1answer
1k views

In normal condition, is the Airbus A320 APU fuel supplied by the main engine boost pump only?

I have a question relating to APU fuel system. As said in material, there are 2 system supplying fuel for APU to operate. 1st one is primary and 2nd one is secondary. In the 1st system or low ...