Questions tagged [engine]

For general questions related to aircraft engines; use the [jet-engine] or [piston-engine] tag if possible.

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83
votes
4answers
17k 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 ...
52
votes
2answers
207k views

What is the difference between a turbofan and a turboprop engine?

I'm not an aircraft expert and I just realized that there are two different terms - turbofan and turboprop. I always had them combined in my head as a term for a large jet engine (like you would see ...
51
votes
3answers
16k views

Could a Dyson fan scale up to be used as a bladeless aircraft engine?

Dyson has been making bladeless fans for a few years now that accelerate a consistent stream of air without exposed blades. If this concept were applied to aircraft engines, it could potentially ...
47
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4answers
9k views

Why are many jet aircraft designed to cruise around FL350-370?

If the flight distance permits, the B737-800 will cruise at FL350, the A320 a little bit higher... Flying at FL370. Photo: Live from the Flight Deck by GolfCharlie232 (reframed) Elements such as: ...
40
votes
5answers
93k views

What are the differences between fuel types (comparing with vehicles)?

I find it funny that at gas stations, generally you can purchase "regular" gasoline (in various octane levels) or diesel. At airports, generally you can purchase 100LL avgas or Jet-A. Can you compare ...
34
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5answers
5k views

Are all the engines on a multi-engine plane the same?

In general, are there any differences between the engines on a multi-engine aircraft? Are engines designed to be specifically for the left or right wing, or inboard or outboard for a 4-engine aircraft?...
32
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6answers
8k views

Why do we never see high-bypass turbofan engines sharing the same nacelle on large airliners and similar aircraft?

I'm talking about this sort of thing (this is the fictional airplane from Casino Royale), rather than two (or more) engines per wing in individual nacelles: If we ignore the weird 'drop tanks' on the ...
32
votes
2answers
12k views

Why does afterburner exhaust have “pulses”?

Instead of being consistently-dense, the afterburner exhaust looks "pulsed" in these pictures below. Is this a trick of the camera, a natural result of interaction with the air, or is there some ...
31
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2answers
8k views

What is the significance of 104% for throttle power and rotor speed?

I noticed this initially when learning to fly Robinson Helicopters but fail to remember the reason my instructor gave me; this again came up when watching a video about the ISS. In helicopters (...
29
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5answers
12k views

Why don't airplane piston engines have mufflers?

It is understandable jet engines couldn't have mufflers, but even long before the jet age, airplane piston engines never had mufflers the way cars do. Is there any specific reason?
27
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3answers
15k views

Does the cannon of the A-10 deliver more thrust than the engines do?

The A-10 Warthog is built around a 30 mm cannon that fires depleted uranium rounds, 65 of them per second. I heard from someone who worked on the flight controls a long time ago, that when the cannon ...
27
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2answers
7k views

What is a rubber engine?

I hear it a lot in engine design , I think that belongs to some phase about we can change the engine parameters according to requirements but I am not sure about it.
27
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3answers
46k views

Why does the 747 have 4 engines instead of 2?

If the 747 can fly with two engines, why does it have four engines? What is gained by adding another 2 engines? Flights over the ocean? Fuel savings? Safety?
26
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3answers
5k views

Which manufacturer produced this fan blade?

I acquired a fan blade a few years back, but have not had any luck finding out who manufactured it or what engine/aircraft it may have come from. The only data I can find on the blade is as follows: ...
26
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4answers
8k views

How does a coaxial rotor helicopter achieve yaw?

Without a tail rotor, how does a coaxial rotor helicopter achieve yaw control? Does a coax have to bank in order to turn? The link goes to wikipedia's article, and down a ways it says: Rotational ...
26
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2answers
6k views

Is it possible to fly with counterbalanced single blade engines?

Refer the image for counterbalanced single blade (Source http://www.aviastar.org/helicopters_eng/bo-103.php). In ground school, they took us for aircraft inspection at end of our ground school ...
25
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5answers
9k views

What is the rationale for single engine military aircraft?

In aeronautics, redundancy is of primary concern. Having at least two engines is common for civilian aircraft. I expect the military to have at least the same level of redundancy. Moreover military ...
23
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6answers
9k views

Why then don't aircraft fly even higher, for even greater efficiency? [duplicate]

After reading various superb QA on here I now see that (basically) aircraft are more efficient per passenger-mile, at higher altitudes. Why don't we go even higher, than current typical airliner ...
22
votes
1answer
29k views

What are the differences between a helicopter engine (turboshaft) and an aircraft engine (turboprop)?

Given the fact that most helicopters nowadays use turbo shaft engines and many aeroplanes still use turboprop engines (which are essentially turbo shaft engines with a propeller), how do you ...
21
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10answers
9k views

Why are all engines identical in typical commercial airplanes?

I come from the IT world where redundancy is in place to cover several cases, among other: a statistical failure of a device (so we use more of them expecting that the event is independent) a rogue ...
21
votes
3answers
13k views

Why are piston engines for aircraft rarely diesel powered?

Why hasn't diesel caught on much for aircraft engines? The list of diesel aircraft engines on Wikipedia is very short. The reason I see mentioned is their poorer power-to-weight ratios. (e.g. What ...
21
votes
1answer
35k views

What is the difference between Hobbs Time and Tach Time?

Over in this answer there's a description of Hobbs Time versus Tach Time, and how the Hobbs counts hours while the tach time is equivalent to "hours at cruise RPM". How do these two "clocks" work, ...
20
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6answers
40k views

Why is water in the fuel tank bad?

I mean, on the one hand it seems kind of obvious, if you had a fuel tank that was mostly water then you would lack combustible materials for the engine, but I get the impression that having any water ...
20
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1answer
6k views

How could this weird shaped aircraft Airbus Beluga fly only with two engines and use short runways?

More than that! She could land and take off fully loaded on 2000 meters of runway at Hawarden Airport as seen here in this video. At my local airport the runway is 2500 meters long and an Airbus A300 ...
20
votes
1answer
2k views

What is the purpose of the three cylinders under the engines of the Junkers 52?

They're mounted underneath each engines on the JU-52. I saw them up close at the museum. Each one consists of bundled half-inch pipes running through the whole length, open at both ends.
19
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2answers
4k views

Why is the front part of the engine not painted?

The engines are always painted a certain colour but the front part is always grey. Source And here on the XWB: Source Why is it that?
19
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2answers
35k views

What are cowl flaps?

What are cowl flaps and what are they used for? It seems I have only heard of them in connection with old planes, are they peculiar to radial engines?
18
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3answers
3k views

Why do reciprocating aircraft engines have more than one spark plug?

Most reciprocating aircraft engines have two spark plugs per cylinder. What are the reasons for this?
18
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2answers
8k views

How is supercruise achieved?

Wikipedia article tells that supercruise is a condition when an aircraft can achieve velocities above Mach one without using the highly inefficient afterburners. But still, there are not a lot of ...
18
votes
1answer
791 views

How do pilots do a preflight inspection of tail-mounted engines?

The recently released first part of an Air Clips documentary of a Lufthansa Cargo MD-11 FRA-NBO flight shows in some detail the pilot carrying out the preflight visual inspection of the aircraft (from ...
17
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6answers
6k views

In helicopters, why not have electric motors controlling blade pitch?

From my related question comes this idea of electrically controlled blade pitch in helicopters. Control linkages in helicopter rotors seem to be pretty complex. This surely incurs a lot of friction, ...
17
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4answers
7k views

Why is the nacelle outlet of the tail engine of the L-1011 Tristar lower than the engine itself?

I've noticed that the nacelle outlet of the Lockheed Tristar is situated below the engine itself. It is at the end of the fuselage. The nacelle outlet of the tail engine of the DC-10 on the other hand,...
17
votes
1answer
3k views

Are rolling takeoffs now more common than powering up while holding on the brakes?

I remember back in the 90's that commercial planes would line up on the runway, stop, apply full power and then release the brake to take off. Now I've been on flight where they've literally rolled ...
16
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4answers
6k views

Is it allowed to let the engine of an aircraft idle without a pilot in the plane. (For both helicopters and aeroplanes)

Is it allowed to let the engine of an aircraft idle without a pilot in the plane. (For both helicopters and aircr). Would there be a difference between a C172 and a 737?
16
votes
10answers
6k views

Can hydrogen gas be an alternative fuel source for a gas turbine engine?

I want to do research for an alternative fuel source for a commercial aircraft that will reduce the cost for flights. Will the hydrogen gas be ignited in the combustion chamber and produce enough ...
16
votes
7answers
9k views

How do rocket engines produce more thrust than aircraft jet engines?

I can't find the reason why rockets are able to produce so much thrust when compared to turbojets. I do know that the rockets carry their own own supply of oxygen since there is no oxygen in space or ...
16
votes
3answers
8k views

How much electrical power does one generator produce on a large turbofan?

From my related question, now I want to know just how much power does the generator produce? In other words, what is the max rating of the generator? It looks so small and that surprised me, but since ...
16
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3answers
3k views

Is a single-engine ferry flight allowed with a twin-engine plane?

If a twin-engine aircraft has an engine problem and could fly somewhere for maintenance, is a single-engine ferry flight ever allowed? If so, do airlines or pilots ever decide to do this?
16
votes
1answer
2k views

How much power is drawn by a turbofan to power its own compressor?

In a modern commercial airliner how much percentage of its engine power is used to power its own compressor, the ducted fan and other ancillaries like the airconditioning etc? Maybe it can't be ...
15
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9answers
20k views

Can an ultralight aircraft fly with a 18hp engine?

I have some questions - I'm planning on building single seat UL aircraft with this plan sketch (I have more), I drew this based on real plain and some research. Empty weight is between 50-70kg with ...
15
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5answers
14k views

Are turboprops more efficient than piston engines (thrust per fuel consumption)?

I want to compare two types of engines: Turboprops and piston engines. I want to know which one is more efficient. There are many types of efficiencies, so I will specify: thrust (in newtons) per fuel ...
14
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6answers
9k views

What's the use of so much torque on propellers?

(This question is closely related to this question) A typical Cessna 172 has a 180 hp engine, with a max. rotational velocity of 2700 RPM. Even small 1 hp electrical motors can achieve that RPM, and ...
14
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3answers
18k views

How are engines mounted onto wings?

I've heard that the engines on a commercial air transports are typically mounted with 2 or 3 bolts. Is this true? If so, how big are these bolts and what are they made of? I'm optimizing a bolted ...
14
votes
3answers
2k views

Do nacelles around aircraft engines help in reducing the engine sound?

I know that the nacelles around the aircraft engines are actually a housing and are generally lightweight and have may components like inlet cowl, fan cowl, etc., but do they help in reducing the ...
14
votes
1answer
9k views

Which jet engines have the highest thermal efficiency?

Some automakers (Mercedes-Benz, Toyota) have recently been making news about the improved thermal efficiency of their engines, stating that they reached the 50% mark. I was wondering if it was the ...
14
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2answers
919 views

Components on engines, are they removed or blanked out?

As a follow up to why doesn't the A380 use outboard thrust reversers, if a component is not used in an engine, is it completely removed (hardware, wiring etc etc) or is it just made inoperative? In ...
14
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2answers
1k views

Is trimming for constant speed equal to trimming for constant angle of attack?

My understanding of trim: When you say you have trimmed an aircraft for a constant speed, say 100 mph, you are actually trimming the horizontal stabilizer so that there are no forces on stick (or tail ...
14
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1answer
2k views

How do engine manufacturers minimize damage from bird strikes?

What are the ways that engine manufacturers currently minimize the damage caused to engines in a bird strike?
13
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4answers
5k views

Can someone explain to me why these planes just don't turn about their center of gravity?

Look at this one: The thrust force from the engine should generate some clockwise moment, right? Why won't it turn and just crash then? I guess the wings generate some sort of anti-clockwise moment? ...
13
votes
1answer
3k views

How does a turbofan with afterburner continue to function in extreme humidity and rain?

From what I understand, the fan(s) collect(s) and compress(es) air into the compression chambers, where fuel is added to the air & combusted to create an even bigger pressure/thrust, right before ...