84
votes
Accepted
Why is jet fuel cheaper than piston fuel?
Jet-A (and all turbine fuels) are far cheaper than 100LL (at least in bulk; retail prices vary due to local supply and demand as well as different regional tax regimes on aviation fuel) for several ...
78
votes
Accepted
How can an altimetry system error during cruise (500 ft at 35000 ft high) cause an insufficient fuel situation?
If the aircraft is cruising at FL350 it is operating in Reduced Vertical Separation Minima (RVSM) airspace (between FL290 and FL410).
With an altimetry discrepancy between the two altimeters of more ...
- 83.8k
55
votes
Accepted
Why is water-contaminated fuel bad, but water-injection is not?
Because of the quantity of water in the fuel, as opposed to a careful introduction of water into the combustion process. Typical water contamination is bad in fuel tanks as water is denser than ...
- 74.6k
48
votes
Accepted
Is it cheaper to drop cargo than to land it?
That scenario only makes sense if your airplane stays at cruising altitude: although taxi and takeoff does use up fuel it's really the ascent to cruise that takes the most. You aren't really going to ...
- 54.2k
47
votes
Is fuel moved around during flight on a passenger or cargo plane? If so why?
Maybe
This is dependent on the air frame and varies from plane to plane and not all planes have capability of moving fuel although most large planes do. The Concorde moved fuel all over the place ...
- 102k
47
votes
Accepted
Why don't we see business jets with wingtip fuel tanks anymore?
One of the main reasons wing tip tanks were used was to counteract some of the forces of wing bending by adding mass to the end of the wings. As time has progressed and our understanding of materials ...
- 102k
35
votes
Accepted
What happens if you do emergency landing on a US base in middle of the ocean?
Wake Island has had aircraft divert there before, as it serves as an ETOPS diversion airport.
Per the remarks on AirNav and the NOTAMs:
RSTD: VERY LIMITED OPERATIONS STATUS, AVBL FOR EMERG LDG AND ...
- 73.5k
34
votes
Does a 120cc engine burn 120cc of fuel a minute?
This is possible, but still quite extreme fuel consumption.
120ml == 120cc gasoline are ~90g by mass
90g gasoline need about 1320g air in order to fully combust
1320g air are about 1.08 cubic meters ...
- 1,543
33
votes
Is it cheaper to drop cargo than to land it?
Looking purely at operational cost of the aircraft, yes. You save time, burn less fuel, don't have to pay for the landing etc.
But dropping the cargo makes the cargo more expensive. You have to ...
- 10.3k
31
votes
Why is jet fuel cheaper than piston fuel?
There are a number of factors that go into it:
Economies of Scale
Jet-A is used in a much higher volume than 100LL. All the jet engine commercial aircraft each day burn through orders of magnitude ...
- 36.2k
30
votes
Accepted
Why do piston engines in aircraft burn fuel at a higher rate than a comparable car engine?
As others have noted, airplane engines and car engines have very different duty cycles. An airplane engine will typically run at full power for a few minutes during takeoff & climb, then at a ...
- 2,587
29
votes
Accepted
What features enable the Su-25 Frogfoot to operate with such a wide variety of fuels?
Being a ground attack aircraft, the Su-25 has an operational ceiling of 23,000 ft and will not encounter the low temperatures to which a Boeing 777 is regularly exposed. Therefore, the risk of diesel ...
- 236k
28
votes
Why is water-contaminated fuel bad, but water-injection is not?
Water-injection in jet engines and piston engines is mixed with fuel
before it enters the combustion
This is actually somewhat wrong (or at least imprecise) and I think it is adding to the ...
- 381
27
votes
Accepted
Why would a fighter drop fuel into a drone?
I read about four possibilities which the SU-27 pilots wanted to enforce:
a) Covering the drone in fuel and then igniting it with the afterburners which should have lead to a fire and subsequent ...
- 4,890
26
votes
Where does Air Force One refuel?
I can't confirm whether either VC-25 has refueled in flight while acting as AF1 but the aircraft is so equipped for the job.
I do know refueling on the ground depends on where the jet is and the ...
- 74.6k
26
votes
Has anyone burned hydrogen in a gas turbine?
Yes, indeed the plan to build a hydrogen-powered jet laid the groundwork for using hydrogen in the Centaur rockets and the upper stages of the Saturn 5. While hydrogen was used only experimentally in ...
- 236k
26
votes
Accepted
How does a jet engine burn fuel when it is not on an afterburner?
The regular way to burn fuel is not to use an afterburner. The afterburner is an option added downstream of a regular engine to increase its thrust temporarily. It is an interesting alternative to ...
- 77.1k
26
votes
Does a 120cc engine burn 120cc of fuel a minute?
No, a 120cc engine does not burn 120cc of fuel per minute. It means that the sum of the volumes of space swept by the pistons in each of the cylinders equals 120cc. This is called engine displacement....
- 7,117
25
votes
Is fuel moved around during flight on a passenger or cargo plane? If so why?
Yes fuel is moved around, and balance is indeed an issue. The A330 has trim tanks in the horizontal stabiliser, and so does the A380. Fuel can be stored there to balance the aircraft - without trim ...
- 62.3k
25
votes
Is fuel moved around during flight on a passenger or cargo plane? If so why?
In 747-100/200 aircraft, takeoff was accomplished tank-to-engine (meaning each engine was fed from it's corresponding main tank). After takeoff the fuel burn schedule called for center tank fuel to be ...
- 39.2k
25
votes
Accepted
How do pilots detect fuel contamination in flight?
If fuel contamination is suspected (because of engine control system fault indications, slow engine responses or rapid engine pressure ratio (EPR) fluctuations), there is an associated checklist ...
- 83.8k
25
votes
Accepted
How can flying high minimize drag and increase fuel efficiency?
Flying higher means less drag because the air is thinner; therefore, you can fly faster at altitude and hence travel farther on less fuel.
However, flying higher also means less oxygen available to ...
- 22.1k
25
votes
Accepted
How to safely handle AVGAS (100LL)?
If you don't crawl underneath and breathe in the exhaust fumes from the engine, you'll be fine. If you do crawl underneath and breathe in the exhaust fumes, you'll be dead from carbon monoxide ...
- 134k
24
votes
Why don't we see business jets with wingtip fuel tanks anymore?
More modern engines need less fuel for the same thrust, so the fuel volume needed for an acceptable range has shrunk over the last five decades. Wing volume alone is now more than sufficient.
While a ...
- 236k
24
votes
Is there any work on improving fuel tanks so they could store hydrogen?
First, to debunk a myth regarding the Hindenberg, which always gets brought up whenever hydrogen is mentioned. Hydrogen is less safe than liquid fuel, but it is not less safe than natural gas or ...
- 1,271
24
votes
Is it cheaper to drop cargo than to land it?
The main advantage of landing is that the plane can then carry another cargo on the return journey. Flying an empty plane back home is extremely inefficient and halves the range of the plane.
Air ...
- 3,353
23
votes
Accepted
How much water is produced in jet exhaust?
Typical fuels consist mainly of carbon (C) and hydrogen (H). The amount of water that will be produced from combustion is dependent on the ratio of carbon to hydrogen. Taking a general fuel with a ...
- 13.7k
22
votes
Accepted
Is there any work on improving fuel tanks so they could store hydrogen?
In gaseous form, the amount of -- the mass of -- hydrogen you could store in the volume of aircraft fuel tanks would be negligible. In order to store enough mass of hydrogen, you'd have to store it ...
- 52.6k
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