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Questions tagged [jet-engine]

Engines which propel aircraft via "jet propulsion", i.e. by expelling high-velocity gasses (usually primarily air) through propelling nozzles.

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Why are contra-rotating jet engines so rare?

Why are contra-rotating jet engines so rare? Such a jet engine would have contra-rotating turbines, or contra-rotating compressors, or both. In fact I cannot think of even one aircraft that has this. ...
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1answer
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Is there any recorded instance of a passenger's hat or scarf being blown into an aircraft's engine?

Passengers climbing the stairs into an airliner are often subject to gusts of wind; I've had to hold onto my own scarf in the past. It doesn't seem beyond the bounds of probability that a passenger'...
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6answers
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Why is water-contaminated fuel bad, but water-injection is not?

A "wet" takeoff of a KC-135 with J57 engines—By USAF Photographer (USAF photo) [Public domain], via Wikimedia Commons Why is water-contaminated fuel bad, but water-injection is not? The way I ...
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Leasing costs engines and aircraft dry lease [on hold]

What would be the cost of a 3 year operational lease for two Boeing 737-800ng aircraft? Will this include the engines? question 2. What would be the cost of leasing two cfm56-3c1 engines to have the ...
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2answers
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How big can a pulsejet be?

Pulsejets are mostly known for propelling the V-1 flying bomb, and have some use as small remote-controlled plane engines. In either case, the pulsejets aren't particularly big, as far as jet engines ...
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6answers
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How are turbine engines started?

What happens to a turbine engine from the time that a start is initiated until stable idle is achieved? What can go wrong?
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1answer
823 views

Do jet engine exhausts usually glow orange?

In these two lovely images: Source: Wikimedia Commons Source: wvi.com The exhaust end of the engines are glowing bright orange from being so hot. Do they get that hot during normal flight ...
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0answers
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Experimental 4 seats diesel airplane with or without parachute(BRS) [closed]

Anyone knows any experimental 4 or 2 seats diesel airplane with or without parachute(BRS), experimental/kit or homologated?
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Why are adjustable area jet engine nozzles mostly limited to military use?

It seems that only jet engines with afterburners use adjustable area nozzles (this means adjusting the area of the nozzle but not necessarily the direction). This includes most fighter jets, as well ...
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2answers
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Is it possible to develop a quadcopter with F35 VTOL-capable jet engines? [closed]

I have little knowledge about engineering so it might be a stupid question but... Is it possible to make a flying vehicle that looks like a quadcopter but uses maybe two jet engines that suck the air ...
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2answers
127 views

Does the stator blade angle changes? Why?

I have read that when jets are on the ground their compression ratio changes. With this change the stator compressor's blade angle changes. Is this true?
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4answers
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Do propeller planes give contrails like jets do?

Last weekend, while watching the second world war film "Fury" with a friend, there was a scene near the end with a large set of bombers flying overhead, leaving large contrails. That seemed wrong to ...
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2answers
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Do F-22's use cartridge start to start engines?

What method does the F-22 use to start its engines? In the video below, you can see a flap open and flame and steam shoot out as the engine starts to spin up. Is this an example of cartridge start? ...
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2answers
365 views

Does the person directing the plane to parking not risk getting ingested by a jet engine?

According to answers in this post, a jet engine can suck a human into its engines, even on idle power. Aircraft use their engines post landing taxi and into their parking space, and I notice people ...
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Oultlet vane guides

I have looked around the web and I could not fine this information. How many vanes are there for the CF6-80 and the CFM-56? Is the count dependant on anything particular, such as fan diameter?
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1answer
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How difficult is it to design a high bypass turbofan given a military derived core?

Suppose one of the big-threes is given a military low-bypass turbofan core, how difficult would it be to produce a design centered around this core that matches the competitive performance of a ...
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2answers
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What is this tube in a jet engine's air intake?

I have long been wondering what is the official name of this little air intake tube located in front of the fan blades and its intended functions. I did search it on google but it was in vain. I guess ...
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2answers
967 views

How are fan and compressor discs balanced?

@curious-cat brought up an interesting question on another thread. How are the fan discs, compressor spools and turbines balanced on a jet engine. As they wear they surely get out of balance. Do they ...
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4answers
279 views

What are the advantages/disadvantages of in-fuselage engines (eg most fighter jets) vs wing/fuselage mounted engines?

Most modern jet fighter designs incorporate their engine(s) within the fuselage, while most other medium/large aircraft mount them either under the wings or on the rear fuselage. What are the ...
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1answer
107 views

Which is better a push fan, a pull fan or both

intricate examination of modern by pass jet engines is despite where it is mounted, they use a pull fan configuration to generate thrust, which set up the most efficient, a pull fan or a combination ...
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2answers
127 views

Jet engine throttle-down time

Apparently airline jet engines lose ~80% of their thrust within 1 second after fuel is cut. However this seems to conflict with long throttle-down times noted in another question. This lead to a ...
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3answers
92 views

How to apply the TO/GA time and EGT limits?

If there is a published 1) EGT limit and a 2) TO/GA time limit, which one should be applied when the EGT is well below the EGT limit and possibly even below the 'max continuous' EGT. Particularly with ...
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5answers
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What is an afterburner and how long can a jet fly on afterburner?

I heard this word so many time in military documentary about jets, especially fighter jets, but I don't fully understand what it is or how it works. In a documentary from the Discovery Channel, all ...
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1answer
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How (and why) does engine thrust changes with airspeed?

I'm interested in how the thrust of a turbofan engine is affected at higher airspeeds (TAS). I know (I believed) that engine thrust(at constant N1) was relatively constant like in the following graph (...
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3answers
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How does the power distribution change for a turbofan engine from being stationary to going at full speed?

I have found out that a turbofan engine of say an F-16 is producing zero power when stationary since $Power = Thrust × Velocity$. But assuming that the engine is producing the same thrust, it appears ...
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2answers
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Are centrifugal turbojets easier to make than axial ones?

Looking at the history of jet engines, I noticed that the British first made centrifugal-types, but the Germans went straight into axial-types. Which type is easier, if any? By that I mean, which ...
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7answers
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Can aircraft other than rockets go to space?

I always wondered if it was possible for planes and other aircraft to leave the Earth's atmosphere. Normal commercial transport airplanes can fly pretty high, but then they need air to get the speed ...
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5answers
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Are taller landing gear bad for aircraft, particulary large airliners?

Buiding larger engines for larger aircraft as opposed to smaller but many engines has proved to result in more fuel efficiency. Having established one of the main drawbacks or impediments to building ...
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1answer
278 views

Does the P&W F100 turbofan engine of the F-16 really produce this much power?

I've been trying to calculate the power a P&W F100 engine on a F-16 is producing using some of the available data on thrust and velocity and I ended up with a number that I want to confirm. Here's ...
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1answer
192 views

Is it safe to mix different types of fuels in a jet engine?

Hypothetically, if: one got stuck somewhere at a remote airport the jet aircraft or airliner they are flying had a 1/3 tank full of the proper jet A1 fuel there was a tanker at the airport with 1/3 ...
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1answer
97 views

What type of engine is mounted on the Cessna Citation Hemisphere?

What type of engine is mounted on the Cessna Citation Hemisphere? Image Source That does not look like a high bypass turbo jet engine. If its not a high by pass turbo jet engine, and given a high ...
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2answers
4k views

What features enable the Su-25 Frogfoot to operate with such a wide variety of fuels?

It is widely attested* that the Su-25 Frogfoot's engines (the Turmansky R-95Sh and later the R-195) were designed to function using a wide variety of fuels, including diesel, gasoline, petrol, ...
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2answers
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How long are the nacelle strakes on a GE-90?

For my school project, I'm doing something where I create a nacelle strake on a model plane and I want to make it to scale. Could you please let me know the dimensions of a nacelle strake? I would ...
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1answer
78 views

What are the major causes of flameout, excluding ingestion of foreign objects?

What are the most frequent causes of flameout, excluding ingestion of foreign objects and other sudden forms of damage to the engine? I'm limiting this to modern turbojet and turbofan engines with a ...
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1answer
101 views

Any unique characteristics to identify aircraft engine? [closed]

I love to find out the engine manufacturer and make, used in all of the aircraft I fly. Can anyone provide hints on how to identify an engine uniquely? The CFM56 on a Boeing 737NG is easy. It has a ...
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3answers
1k views

What is Engine Pressure Ratio?

I kind of know what it is but I don't fully understand it. Wikipedia says, the engine pressure ratio (EPR) is the total pressure ratio across a jet engine, measured as the ratio of the total ...
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2answers
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Which engine is more efficient between turboprop vs jet?

Are turboprops really more efficient than jets? If yes, does that mean that airlines who use jets sacrifice fuel for faster flights?
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6answers
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On which point(s) in a jet engine does the reaction force act?

A turbojet/turbofan engine is aimed to accelerate air or combustion gases. Sometimes these engines are named "reaction engines" to emphasize the fact the aircraft is moved forward mostly by Newton's ...
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3answers
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Why would a jet engine that runs at temps excess of 2000°C burn when it crashes?

Airline engines are designed to work at very high temperatures. Yet, when a plane crashes they're burnt (see below). Is it something in their design? (bostonherald.com)
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4answers
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Why do gases in the combustion chamber only flow one direction to the gas turbine in a jet engine?

As far as I know from the working principle of jets engines, compressed air in the combustion chamber (or combustion canister) is mixed with fuel. The ignited mixture expands backwards to turn the ...
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1answer
1k views

What is the highest operational ceiling for an air-breathing jet engine?

An air-breathing jet engine can only operate at relatively low altitude, where the atmosphere is dense enough. However, some jet-powered aircraft can operate at an altitude higher than 20 Km (e.g., ...
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3answers
1k views

What are these holes in the engine inlet?

In the next picture can be seen within the housing, near the inlet:
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0answers
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Does any modern jet engine have blow-in doors, if not, why?

Are the blow-in doors concept on some engines like the JT3D used on modern jet engines, or not? If they are unusual, please explain why?
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2answers
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Why is max endurance different for jet and props?

Max endurance speed is not the same for gliders, propeller planes (also for turbo prop, right?) and jet planes. While for for jet planes max endurance is at the minimum drag speed ($V_{md}$), for ...
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2answers
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What is that extended nacelle feature on the Honda HA-420 HondaJet?

Here is a picture of the Honda HA-420 HondaJet with strange extended engine housings. Why are they required? What are they for? I am not asking about the red covers, but the white engine housing ...
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4answers
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Can an experienced airplane spotter identify planes only by sound?

I come from a background in railroad watching, and often times one can identify the maker of a railroad locomotive purely by sound. Maybe not the exact model of locomotive, but at least what type of ...
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2answers
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Why Engine Exhaust Nozzle can not be totally buried in aircraft fuselage? [closed]

Why The CD nozzles of the fighter aircraft are always outside the fuselage, Why the whole engine is not buried in the fuselage?? If engine shroud also can be made variable area and varies with CD ...
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3answers
3k views

How much water is produced in jet exhaust?

If a jet has typical combustion efficiency, what equivilent amount of liquid water will be created per gallon of jet or kerosene fuel. An acceptable answer can be a ratio in weight or volume to the ...
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2answers
66 views