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108 votes
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Why does the F-111 sometimes squirt a giant fire plume behind it? (NOT afterburners!)

The F-111 has, like many aircraft, a fuel dump port so it can get rid of a lot of heavy fuel rather quickly. Most aircraft have the dump ports on the wings, the F-111 designers put it in the tail ...
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103 votes
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Why do jet engines use kerosene rather than gasoline?

You can persuade a turbine engine to run on just about anything that can burn. So the decision of which fuel to actually use depends on the side factors including, but not limited to: availability ...
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83 votes
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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 ...
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77 votes
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What are the differences between fuel types (comparing with vehicles)?

Broadly speaking, there are three families of motor fuel that you're probably interested in: Diesels, Kerosenes, and Gasolines. The difference between the families mainly has to do with the molecular ...
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77 votes
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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 ...
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69 votes

Why does the F-111 sometimes squirt a giant fire plume behind it? (NOT afterburners!)

There was at least one occasion when the dump-and-burn was used in combat. During the 1986 attack on Libya the U.S. pilots, desperate for fuel, jostling with one another in the air to get access to ...
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54 votes
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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 ...
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49 votes
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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 ...
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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 ...
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45 votes
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Why is fuel usage discussed per time, not per distance?

Unlike with driving, in aviation the major variable when planning fuel consumption isn't how far you're traveling but how long you're traveling: Distance traveled in aircraft is a derived value (...
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45 votes
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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 ...
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38 votes

Could most commercial jet engines today run on ethanol without any problems?

Although turbines could be designed to run on ethanol it's actually a lousy aviation fuel (actually it's a lousy fuel in general). Petroleum-based jet fuel is high grade kerosene which has lubricant ...
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35 votes
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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 ...
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34 votes
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Why are we still putting lead in our fuel?

There is nothing "special" about an aircraft engine that requires lead in the fuel -- Engines don't much care about the lead in tetraethyl lead, nor do they much care for it (it gets everywhere, ...
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34 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 ...
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  • 10.1k
33 votes

Why is AVGAS so much more expensive than car gas?

The LL of 100LL stands for Low Lead as it has tetra-ethyl lead added as a detonation inhibitor for high-performance engines. Despite the "low" moniker there actually is a lot of it in there, and it's ...
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33 votes
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Where does Air Force One refuel?

According to the Washington Post, Air Force One never refueled in mid-air with the president on board. If it needs to refuel, it usually does so at one of the U.S. military bases across the world. ...
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32 votes
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What happens to incoming flights when the airport shuts down?

If a "terrorist takeover" like this were to happen in the real world... ...and the tower still had communication capability: The tower controllers would advise pilots of the situation, and likely ...
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32 votes
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How do aircraft keep fuel from freezing while in flight?

Much like water, exposing fuel to below freezing temperatures does not instantly make it freeze. It takes some amount of time, and as long as the fuel is not exposed to below freezing temperatures ...
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32 votes

Do airplanes dump fuel before landing?

Is it true that they must dump excess fuel before they land? Nope. You don't siphon your car just before your destination. Fuel is money. Except in emergency in big planes, fuel then is a ...
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31 votes
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Does electrical usage contribute to fuel consumption?

Short answer In flight, unless you use external energy sources like the Sun, each change in the use of electricity leads to a proportional change in the quantity of fuel burnt in the engines (or in ...
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  • 67.6k
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 ...
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29 votes
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What are the ICAO fuel reserve requirements?

The following includes the changes you allude to (which were proposed in ICAO State Letter SP 59/4.1-11/8 on June 30, 2011). Commercial Flights Per ICAO Annex 6, Part I, section 4.3.6 "Fuel ...
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  • 10.5k
28 votes

How is engine fuel kept from freezing?

In regions and weather conditions where this is likely to be a problem, other fuels are used instead of Jet-A. For example, Jet-B has a freezing point of -60C and is used during the winter in some ...
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  • 57.5k
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 ...
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27 votes
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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 ...
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26 votes

Why do jet engines use kerosene rather than gasoline?

In a modern turbofan engine, fuel is not only burned in the engine and used to lubricate parts such as fuel pumps and controls, it is used as a hydraulic fluid as well -- this is used to power things ...
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26 votes

What makes a smokeless jet engine?

Generally, smoke comes from incomplete burned fuel. Normally, a jet engine burns a very lean mixture (due to turbine temperature constraints). Nevertheless, getting all the fuel to burn is a ...
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26 votes
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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 ...
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  • 2,507
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 ...
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