Questions tagged [engine]

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

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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
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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 ...
11
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4answers
3k views

What is a ramjet?

What is a ramjet? Was it used on the SR-71 Blackbird?
14
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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 ...
9
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2answers
3k views

Why do engine cowl lips appear larger and more blunt on the sides than on the top and bottom?

I was looking into engine nacelles. I was not able to understand the design shape of it Why is it that in most aircraft, the engine cowl lips on the side are bigger (more blunt) than on the top and ...
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?
21
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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, ...
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 ...
7
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4answers
4k views

Do gyroscopic forces (from rotating engines) significantly affect yaw or pitch?

It occurs to me that jet engines are very heavy objects operating at high RPMs. This must have a very high angular moment and thus a high gyroscopic force. This would restrict rotation when trying to ...
52
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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 ...
16
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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 ...
3
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1answer
953 views

Are there any programs to build a hydrogen powered airplane?

So called "renewable energy" is a buzzword these days. Auto manufacturers are starting to roll out hydrogen powered cars. Hydrogen may not currently be the most efficient or economic fuel for jet ...
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 ...
21
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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 ...
9
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2answers
7k views

How far can a 777 fly with just one engine at altitude?

If a 777 pilot wanted to fly further than with both engines running, how many more miles could the plane go with just one engine running, at high altitude?
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 ...
5
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3answers
7k views

What is 2D and 3D thrust vectoring?

How do we define 2D and 3D thrust vectoring? What are the differences between the two? Is there anything called 1 D thrust vectoring?
5
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3answers
11k views

What is a flat rated engine?

I've heard that a "Flat Rated Engine" is an engine where the power is reduced to keep the internal temperature within certain limits when the ambient temperature is above a certain point. Is that ...
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 ...
9
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2answers
6k views

What are the limitations in adoptions of GTF (Geared Turbofan) technology?

The only recent engine using GTF technology is the PW1000G, however some old designs like ALF502 or TFE731 use this technology. I understand the basic concept of the benefit obtained by the engine ...
6
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1answer
4k views

How does the F-35's roll posts work, and how does its engine turn down 90 degrees?

I've heard about the F-35's roll posts but I don't get how they work and how its engine turns downwards 90 degrees, any ideas?
4
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1answer
2k views

Why does the LP compressor rotate in the opposite direction of the HP compressor?

Why does the LP compressor rotate in the opposite direction of the HP compressor in some multi-spool turbine engines?
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?...
16
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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 ...
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 ...
17
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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 ...
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 ...
1
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1answer
6k views

How to calculate the thrust of a piston or turboprop engine? [duplicate]

This spawns from a related question. Propeller-drive engines (piston/turboprops) seem to always list their output in horsepower or kilowatts, which are units of power. I want to know the engine's ...
12
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5answers
2k views

Has there ever been a diesel-electric helicopter?

Occasionally I come across the diesel-electric (DE) design for submarines and freight trains. They say something like "a diesel engine powering an electric drive lets the two operate at their most ...
3
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1answer
255 views

Where can I find sample data required for Engine Condition Monitoring? [closed]

I'm trying to find some sample data required for Engine Condition Trend Monitoring to analyse and predict when an engine might fail. I went through a lot of research papers and (kind of) understood ...
11
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1answer
1k views

How does the energy and weight efficiency compare between a battery/electrical propulsion and combustion engine?

For the same total energy and power output would a battery powered vehicle be lighter than one which uses a fuel burning engine (Currently)? This question is intended for helicopters.
32
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2answers
13k 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 ...
3
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2answers
10k views

Can a Boeing 767-200 fly at 510 knots at a height of 400 metres?

Can a Boeing 767-200 physically fly at 510 knots at around 400 metres altitude? If it did manage that speed, how likely would a structure failure be? Also, if those measurements were achieved, how ...
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 ...
4
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2answers
2k views

About how much drag does a non-operating engine create?

I think the drag of the engine is high, for most type of engine, e.g turbo fan, jet, ramjet... I guess the engine's drag is worse than a flat plate of the same area perpendicular to air stream because ...
22
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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 ...
16
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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 ...
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 ...
14
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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 ...
9
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3answers
3k views

Is the bleed air passengers breathe tapped from the engines before or after it comes in contact with fuel? And why? Isn't this unhealthy?

Passengers are often surprised to hear that the air they breathe comes from inside the engines. This sounds unhealthy. Can you explain, why it is not ? Is bleed air tapped (for cabin pressurization) ...
5
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2answers
2k views

How is mass flow rate computed?

I have been wondering how the mass flow rate is determined by the area of the engine air intake surface and the incoming speed of the air. In still air, it is understandable that a stationary engine ...
4
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1answer
1k views

Is it possible to re-engine aircraft with different engine options?

Most airliners have multiple engine options and so I was wondering if it would be possible for operators to fit a different engine type to their existing aircraft; let's take for instance the Boeing ...
3
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4answers
9k views

Do all B777 family aircraft have the same engines?

I think there are multiple variants of engines for the different variants in B777 family but I am not sure but is it GE90-115B in one while Trent and PW in others?
0
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1answer
349 views

Is it possible to create a direct supersonic airflow to a turbofan's afterburner in order to enhance the performance or reduce the fuel consumption?

so I found out that SR-71 Blackbird is using what's called "turboramjet" and I find the idea a bit appealing since they say with such engine, the Blackbird is more fuel efficient at it's top speed. I ...
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,...
11
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1answer
881 views

Are engines fed differently in reduced gravity aircraft?

Reduced gravity aircraft are basically airliners without passengers seats. As airliners, those aircraft were not designed to fly for a long time in zero-G. Specifically engines were not designed to be ...
9
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1answer
6k views

What are the reliability statistics for modern jet engines?

What is the actual numerical reliability statistics of the modern, large-aircraft, commercial turbofan engines available today? e.g. How many running hours can we expect a failure after? Are there ...
2
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3answers
898 views

125 cc engine, 64" propeller 3 blade, 180 kg gross weight, will it climb?

I'm a government teacher in school, currently I made an RC aircraft and flew it, now I'm working on a single engine light weight aircraft, I want to use a Honda CG 125 (single piston) engine, with 64" ...
83
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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 ...
51
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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 ...