Questions tagged [fuel-systems]

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

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8
votes
7answers
3k views

Does this fuel leak from the carburetor of a C172E need immediate maintenance?

I'm concerned with a fuel leak I've developed on my C172E in the past 3 weeks and appears to be coming from the carb. There is even some fuel in the air breather near the bottom. A&P said its ...
9
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2answers
1k views

How common were (are?) hydraulically driven fuel pumps?

The XB-70 had a large number of fuel transfer pumps (something like 25) to transfer fuel from the 10 other tanks into the sump tank, and then three fuel "boost" pumps to pump it from that to ...
6
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2answers
1k views

How does a fuel density sensor work? (densitometer, cadensicon)

While some fuel volume sensors use ultrasonic measurements this answer to How is fuel mass measured in airliners? says: The FCOM lists the sensors involved in this measurement: The FQI system ...
16
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2answers
3k views

How is fuel mass measured in airliners?

Large airliners display the amount of fuel in each tank as a mass (usually in kg or lbs) and not as a volume. This makes sense since mass is important for weight&balance considerations and the ...
4
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2answers
711 views

On what basis is the weight unit of the FQIS selected by airlines of various countries?

On what basis is the weight unit of the FQIS (Fuel Quantity Indicating System) selected by airlines of various countries? Does it depend on the local country for using imperial or metric units?
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1answer
125 views

Why are there motive flows for the turbine pumps of Williams International FJ44-3A engine?

For my university project, I am designing the fuel supply of an aircraft using a Williams International FJ44-3A engine. Studying the related FAA TCDS, I read "Fuel from the motive flow port on ...
1
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1answer
132 views

What are the fuel system pressure and temperature requirements of a Williams FJ44 engine?

For my university project, I am designing the fuel supply and control system of an aircraft that use Williams International FJ44-3A engine. However, after scouring through its type certificate ...
2
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2answers
119 views

What is vapor lock?

Vapor lock occurs in piston engines especially during summers.. before starting engine we prime it and the engine starts but as soon as we reduce it to near idle or just above idle, engine tends to ...
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0answers
126 views

Where are the small fuel reservoir tanks on a Cessna P210N?

I have looked through the POH and the maintenance manual of the Cessna P210N, both said that the fuel goes from the main tanks into two small reservoir tanks somewhere on the lower side of the ...
6
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3answers
315 views

Why do we turn on fuel pump before descent in Diamond DA40?

The checklist procedure is: Electric fuel pump ............. on Mixture ............. rich MAP ............. 15 in of Hg RPM ............. 2300 Why the AFM says to turn on fuel pump during descent ...
0
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1answer
162 views

How should fuel go through pumps?

I understand that in the fuel system of an aircraft, the fuel first go through wobble pumps--manually driven, and then fuel strainers--for filtering out debris, and finally the engine driven pumps. ...
9
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3answers
2k views

Do pilots need a fuel pressure/temperature gauge?

Fuel pressure gauge allows you to monitor the fuel pressure while the engine is under a load. However, since the fuel pressure requirement is listed by the engine manufacturer, do pilots even need a ...
0
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1answer
109 views

What extra components does a fuel tank have?

For small-to-mid-size aircraft like V-280, and gulfstream aircraft, what component does their fuel tank has when it arrives for assembly? Is it just a metal box with valves? Or it contains heating ...
0
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1answer
142 views

Who make the fuel system, cabin pressurization system, and firefighting system?

Who makes the fuel, cabin pressurization, and engine firefighting system for an aircraft with engines on, or in, the wings? Fuel tanks and fuel pipes, pressurized air pipes and heat exchanger, and ...
4
votes
2answers
613 views

Why should the fuel shutoff valve in a Zlin Z-142 not be set to both for takeoff?

The fuel shutoff valve in the Zlin Z-142 has four different positions: Off, Left, Right and Both (L+R). In the POH, the procedures related to normal flight operations, suggest that during taxiing and ...
1
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2answers
372 views

Is it generally acceptable to use 100LL and 100 grades of AVgas mixed into the same tank?

Is it acceptable to use 100LL and 100 grades of AVgas mixed into the same tank, or should one type of fuel be drained prior to addition of a mismatched type? This is assuming the aircraft is approved ...
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0answers
34 views

How to calculate head loss from flap valves?

Is there a common lookup table or a correlation-like formula to calculate head loss caused by flap valves? Is the head loss small enough to neglect?
2
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2answers
476 views

Use of a solenoid valve over a selector valve

When designing a low-wing light aircraft with two integral tanks at the wings and a collector tank in between, what type of valve should be used to allow the pilot to select the integral tank which ...
2
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0answers
131 views

Overheating (fire thrown out of the nozzle) [closed]

At first I copied https://www.jetcat.de/en/productdetails/produkte/jetcat/produkte/hobby/Engines/P160_rxi_b Where I manufactured and installed all the parts and they are very similar to the original ...
1
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0answers
63 views

When should the fuel pump be on in a Cessna 152? [duplicate]

I am a new student and just need help understanding the fuel pump system. For a Cessna 152, in which scenario would I have the fuel pump on ? Start ? After Start ? Before Take-Off ? After Take-Off ? ...
5
votes
1answer
874 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?
9
votes
3answers
408 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 ...
3
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4answers
500 views

What are some symptoms of a clogged fuel filter?

I can certainly imagine one of the symptoms could potentially be engine fuel starvation. If the fuel flow to the engine isn't totally blocked, how can one recognize a clogged fuel filter?
3
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2answers
739 views

What is the difference between LP fuel valve and LP fuel shut off valve?

In the Airbus A320 FCOM in some places "LP fuel valve" is mentioned (in Fire and Fuel System chapters) whereas in the engine chapter "LP fuel Shut off valve" is mentioned. Is there ...
14
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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?
2
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2answers
260 views

Is gascolator and fuel strainer the same thing?

I am wondering is gascolator the same as fuel strainer, or this two things are bit different. Because sometimes I see one term, sometimes another, and I don't know if I am reading about the same thing....
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0answers
61 views

What is a typical fuel temperature entering the burner for different mission flight points of a civil aircraft?

Is there a target regarding the fuel temperature that enters the turbine engine's combustion chamber and if so does it change with different operation flight points in civil aircraft applications? Is ...
1
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1answer
88 views

How long would the engine of a Tecnam P92 Eaglet run for with the fuel selectors turned off?

I'm wondering about a scenario where a P92 has been flying for at least 30 minutes or so, at say 4,000 RPM and 2,000' AGL at standard temperature (I'm not sure if these details matter). With both ...
0
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1answer
106 views

How do fuel tanks prevent free surface effect? [duplicate]

Free Surface Effect is a fancy term that refers to liquids changing their relative orientation within a container, whenever the container is rotated. So imagine a large plane banking very steeply, at ...
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 ...
17
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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:...
1
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1answer
324 views

Why is “L Fuel Low” illuminating on my Cessna that is full of gas?

I fly a fuel injected Cessna 172SP 200 hp. Tanks were just about full today and every 5 seconds or so in flight, I would get “L fuel low” and the left fuel indicator would drop to 0. I’ve consulted ...
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1answer
212 views

How much pressure do boost and jettison fuel pumps produce?

What is the pressure output of a (boost) fuel pump on a Boeing 767 and/or 777, compared to a heavy-duty jettison fuel pump.
18
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1answer
3k 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 ...
3
votes
3answers
245 views

Where does fuel from the boost pumps go before engine start?

For example let’s take the PT6A-27. In every video related to engine start I see, the fuel boost pump is turned on, and then the fuel pressure goes up. Example: My ...
8
votes
2answers
554 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 ...
0
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0answers
139 views

May an A330 depart with with empty outer fuel tanks?

Airbus does not recommend flying with empty outer tanks, to reduce stress on the wings. Also, when the outer tank transfer valve is inoperative, the MEL says to fill the outer tanks with fuel and it ...
5
votes
1answer
701 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 ...
9
votes
1answer
186 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 ...
6
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 ...
1
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1answer
369 views

How to find the remaining fuel without electrical power on the MD-80?

After a flight, how to find the remaining fuel without electrical power (even the APU) on the MD-80?
0
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1answer
203 views

What is the difference between staged and unstaged fuel manifolds? [closed]

Also, I would like to know the difference between pilot, primary and secondary fuel flow.
3
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1answer
387 views

Is fuel in trim tank usable?

Some aircraft (A380, Concorde,...) are equipped with a trim tank in the tail. Transferring fuel from or to this tank help controlling the CG. This feature can only be achieved if there is fuel to ...
1
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1answer
538 views

What is the difference between fuel control unit and fuel flow meter (transmitter)?

Hello can someone explain the difference between the fcu and fuel flow transmitter and how they work together alongside the fuel pump?
6
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3answers
1k 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 ...
16
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4answers
9k 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 ...
2
votes
0answers
196 views

Are there design guidelines for sizing vent/surge tanks?

Could someone explain the sizing process of Vent/ Surge tank of Aircraft fuel system? I understand the Vent tank is to collect fuel overflow from the main fuel tanks. The reason could be due to Fuel ...
0
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0answers
149 views

Airbus a380 fuel system [duplicate]

Does the aibus a380 has center tank compare with a320,in this picture above,it shows that it has 11 tanks including the wings and the elevator while many aircraftshas together with the center tank (i ...
7
votes
1answer
855 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 ...
2
votes
1answer
2k views

How do you lean mixture using only the instruments on a C172 Skyhawk?

POH manuals always tells to use the voice of the engine as a reference. (Which complicates things a little bit since carbs and fuel injected planes have different "reaction times" for each cylinder) ...