Questions tagged [fuel-systems]

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

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What is the purpose of the fuel pumps in the A320?

It might seem like a really stupid question, But i'm getting into flying the FBW A320 in MSFS2020 and I have no idea what the fuel pumps are for in the A320, please may someone explain and help a ...
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1 vote
2 answers
106 views

C172N Skyhawk II fuel drain handle operation for people < 180cm

I'm asking for a friend - literally. One of our club's planes is an old workhorse used a lot for training. She's got a fuel drain handle in the inspection hatch where one checks the oil. I've never ...
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17 votes
1 answer
2k views

When drop tanks (those with external lines) are released, how are the two connections (air and fuel) released?

ww2aircraft.net Say in a P-51 (shown above), when drop tanks (those with external lines) are released, how are the two connections (air and fuel) released? Do they shear off and fall with the tank? ...
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3 votes
1 answer
96 views

Where is the ram air inlet duct on the A220 for the fuel inerting system? Is it the same duct as the air conditioing?

Title says it all... just trying to find out if there is a second NACA duct for the fuel inerting system on the A220, or if it's the same duct that is used for the air conditioning inlet.
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7 votes
2 answers
279 views

Why does a fuel-injected engine have a mixture control?

For example, in a C172S fuel injected type, what does the mixture control lever control exactly in the fuel system? They have a fuel air control unit which regulates fuel flow based on air passing ...
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12 votes
6 answers
5k views

Does this fuel leak from the carburetor of a Cessna 172E need immediate maintenance?

Consider: I'm concerned with a fuel leak I've developed on my Cessna 172E in the past three weeks and appears to be coming from the carburetor. There is even some fuel in the air breather near the ...
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9 votes
2 answers
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 ...
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6 votes
2 answers
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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 ...
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16 votes
2 answers
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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 ...
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4 votes
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722 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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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 ...
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1 vote
1 answer
155 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 ...
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2 votes
2 answers
169 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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1 vote
0 answers
148 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 ...
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6 votes
3 answers
489 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 ...
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0 votes
1 answer
176 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. ...
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9 votes
3 answers
3k 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 ...
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0 votes
1 answer
119 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 ...
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0 votes
1 answer
145 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 ...
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4 votes
2 answers
628 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 ...
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1 vote
2 answers
761 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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0 votes
0 answers
38 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?
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2 votes
2 answers
490 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 ...
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2 votes
0 answers
133 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 ...
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1 vote
0 answers
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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 ? ...
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5 votes
1 answer
888 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?
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9 votes
3 answers
640 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 ...
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3 votes
4 answers
632 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?
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3 votes
2 answers
1k 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 ...
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14 votes
2 answers
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?
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2 votes
2 answers
336 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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1 vote
0 answers
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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 ...
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1 vote
1 answer
100 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 ...
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0 votes
1 answer
122 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 ...
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16 votes
4 answers
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 ...
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17 votes
5 answers
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:...
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1 vote
1 answer
399 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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2 votes
1 answer
250 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.
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18 votes
1 answer
4k 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 ...
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3 votes
3 answers
263 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 ...
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8 votes
2 answers
658 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 ...
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0 votes
0 answers
169 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 ...
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5 votes
1 answer
828 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 ...
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9 votes
1 answer
198 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 ...
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6 votes
2 answers
3k 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 ...
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1 vote
1 answer
427 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?
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0 votes
1 answer
237 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.
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3 votes
1 answer
475 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 ...
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1 vote
1 answer
595 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?
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6 votes
3 answers
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 ...
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