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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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1answer
191 views

Why was there no thrust from the engines in the TACA Flight 110 incident?

I have just watched Mayday episode 11, season 11, "Nowhere to Land" about TACA Flight 110 incident. Most key issues of the incident are clearly explained in the episode: Why both engines turned ...
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4answers
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Are jet engines designed in a way to make an explosion result in the least damage possible?

I know most engines are super reliable today, but do manufacturers do anything to at least make an explosion result in the least damage possible?
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97 views

How would exhaust heat recovery into the combustion chamber affect the efficiency of a jet engine?

So, a jet engine basically sucks in air, heats it up and spits it out, right? The hotter the air gets, the faster the exhaust velocity and thus the more efficient (Higher specific impulse). Now my ...
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Rocket Thrust vs Air breathing jet engine why is a rocket better [duplicate]

What are design dynamics that give the rocket engine higher thrust than an air breathing jet engine of similar size in comparison to a turbo jet engine, turbo fan engine, high by pass turbo fan engine,...
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1answer
68 views

Are high bypass turbo jet engines suitable for tail and body mounted engines

Are high bypass turbo jet engines suitable for tail and body mounted engines. If not what are the drawbacks, danger if so, are there any anycraft with any such setup?
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7answers
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What prevents a commercial jet from electronically “resetting” the way a computer sometimes does?

I've had a fear of flying for the past several years and one of the ways this irrational phobia manifests is concern over the airplane power-cycling in mid-air: engines cutting out, control equipment ...
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1answer
155 views

What drives the compressor before the turbine provides power?

I understand that the power extracted from the turbine is used to drive the compressor which sucks and squeezes air sent to the combustion chamber, and the cycle continues. But initially the ...
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1answer
171 views

What does it mean when an aircraft engine is de-paired?

What does it mean when an aircraft engine is de-paired? e.g. the PW1000g engines being de-paired because of issues in the LPT or the Rolls Royce Trent 1000 engines due to excessive corrosion on some ...
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0answers
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How do the contrarotating turbines work in the F-119-PW-100?

I was reading about the F22 Raptor and found out that its powerplants use contrarotating turbines. How does this work Also, if the spools and their connected compressors are rotating in opposite ...
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7answers
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How does increasing the size of a jet engine make it more fuel efficient?

The design trend is there: 8, 4, 3, 2 jet engines on powering the large cargo or passenger aircraft. Is it mostly to accommodate the larger, more efficient fans, or are there also benefits in the ...
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2answers
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Why do jet nozzles close at different rates?

After recently seeing the trailer for Top Gun 2, I was reminded of something that I always wondered about: why do the nozzles of some jet aircraft seem to close at different rates? Sure, it's likely ...
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1answer
61 views

Can a CFM56-3C engine be converted into a CFM56-3B1?

Is it possible to take a CFM56-3C engine and modify it to a CFM56-3B1 engine? I own a CFM56-3C engine but my customer would like to install a CFM56-3B1 engine on his plane. Can this be done?
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What’s that weird sound during spool up on some aircraft?

Some engines seem to make this characteristic “wailing” noise when spooling up. A good example of such is from 0:50 to 0:54 in the following video: . I’ve also heard ...
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2answers
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How is a stator like a diverging passage?

I've read in a lot of places that stators in an axial compressor are responsible for diffusing air and removing the radial velocity to make the flow parallel to the shaft. What I don't understand is ...
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3answers
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How does the engine wash improve engine performance?

According to maintenance manual, we usually carry out engine wash (CFM56) with pure water as scheduled task. Pure water is injected into the engine from the LP compressor inlet while the engine is ...
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3answers
294 views

Do afterburners use excessive amounts of fuel?

The purpose of an afterburner is to provide additional thrust, and it is obvious that more fuel is needed for that. But that is to be expected independent of an afterburner. That more thrust needs ...
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6answers
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Is an afterburner louder than the same jet engine without it?

I would speculate that an afterburner increases the noise because it is nearer to the exhaust. But it certainly causes so many changes in the exhaust flow that it could be less loud as well. It may ...
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Is engine sync to avoid beat frequencies also a concern for jet engines?

Is synchronization of rpm to avoid beat frequencies also a concern on jet engine aircraft like it is on propeller driven airplanes? Context: This question on SE-Aviation discusses prop sync for ...
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1answer
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Are the “centerbody”, “fan hub frame”, and “intermediate case” all the same thing or separate parts?

I'm curious about the frames & cases at the front of an engine. I've seen OEMs call them the centerbody, fan hub frame, and intermediate case. Are these all the same thing or are these each a ...
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1answer
914 views

Can a tail pipe fire occur in cruise? If not, why not?

I was reading the news for an incident where an A321 had to divert due to: the aircraft returned suspecting a tail pipe fire on the #1 engine, the crew did not receive any engine fire indication or ...
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1answer
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How can I calculate turbofan efficiency as a function of turbine inlet temperature?

I know that increasing the turbine inlet temperature (TIT) increases the overall efficiency of the jet engine. So I wanted to find the overall efficiency as a function of TIT. I used the equations ...
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1answer
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How will the Rolls Royce UltraFan provide reverse thrust?

When perusing the Wikipedia article on the upcoming Rolls Royce UltraFan engine, I noticed that it cited an interesting bit of information from an Aviation Week article: As the fan system is ...
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0answers
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Specific Thrust and its effect on max speed?

I was reading this. How (and why) does engine thrust changes with airspeed? I understand how thrust is calculated from inlet and exit velocity. I understand the energy it takes to increase velocity ...
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10answers
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Why do new jet engines cost billions to design?

This question might come off as crude because it involves people's salaries, but I do not understand why new designs of large turbofans cost many billions of dollars to design. For example, the Pratt &...
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4answers
326 views

How to start up a Lockwood-Hiller Valveless Pulse Jet?

So me and my group mates in university got a lockwood hiller valveless pulsejet manufactured, and there was one error in manufacture. We are having trouble with trying to start the engine as ...
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1answer
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Is there an equation for jet engine efficiency as a function of turbine inlet temperature?

I know that there is a relation between the turbine inlet temperature and the engine's efficiency. But, can anyone provide an equation or efficiency as a function of just the turbine inlet temperature?...
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1answer
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Turbine blade manufacturing/assembly process

I want to know the process for manufacturing turbine blades and the companies that are involved. Who makes the turbine blades? Who applies the thermal barrier coating? Who repairs the blades? Let's ...
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4answers
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Do modern jet engines need igniters?

I've read that modern aircraft don't need spark plugs like conventional aircraft do, as the jet fuel autoignites once it's mixed with the hot air exiting from the compressors. Then why do aircraft ...
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1answer
118 views

How does a propfan work?

Could someone give me a simple working of a propfan? Also I've heard the 2 sets of blades in a propfan rotate in opposite directions. Is this true? And if so why?
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2answers
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Do the compressors and turbine rotate at the same speed?

Since the turbine and the compressors are connected to each other via a common shaft, do they both rotate at the same speed. Because I've read that in some jet engines (single spool engines) they don'...
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2answers
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Why does idling RPM increase with altitude in a jet engine? [duplicate]

The Snecma-Larzac 04-C6 idling RPM ranges from approximately 53% on the ground to 85% at high altitude. Why is that?
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1answer
146 views

Turbines in jet engines

I was reading this thread and in the answer, the person wrote "For example, the turbine blades are replaced after a set number of turbine cycles and/or after a set number of hours, which are lesser ...
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1answer
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How often are turbine blades in jet engines replaced?

How often are the turbines in the hot section of the jet engines replaced due to deteriorated TBC? or just how often are they replaced? lets say for CFM56-7
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2answers
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What would be the minimum number of engines required to climb in a 747?

There was a really good Air Crash Investigation by Nat Geo which showed the British Airways Speedbird 9 issue where volcanic ash swept over all four engines and through the air vents inside the cabin. ...
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Effect on pressure and/or volume of a real vs. ideal compressor

I'm looking at the Brayton cycle and trying to understand what happens when we move from the ideal cycle (isentropic compression/expansion) to the real world where we have adiabatic compression/...
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1answer
132 views

What is the air/fuel mixture ratio in a turbojet engine?

How does it relates to stoichiometry ? What are the possible extinction accidents related to air/fuel mixture ratio ?
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Does the angular momentum of a jet engine affect aircraft performance?

I am interested, do jet engines have angular momentum? And how does such momentum affect airplane stability?
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Could hydrazine be the jet fuel of the future?

It is true that hydrazine is highly toxic and explosive, but it has tremendous energy density. The decomposition of hyrazine into hydrogen and nitrogen gases AFAIK produces enough heat to ignite the ...
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Why do the 737-100's JT8Ds, and no others, have suck-in doors?

Of the various use cases of the Pratt & Whitney JT8D (the most-produced low-bypass turbofan in history, and the second-most-produced turbofan of any description1), those installed on the 737-100 ...
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1answer
314 views

Why does taxiing produce large lateral loads on the 747's engine pylons?

While reading through a bunch of old AARs recently, I found (in the context of a 1993 747 in-flight engine separation) this interesting tidbit: [...] Boeing engineers report that the modifications ...
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Can the assumed temperature be lower than the flat rated temperature?

I was playing with reduced takeoff thrust in a Boeing 737-800 simulator yesterday and was surprised that I could enter assumed temperatures below the flat rated temperature of the engines. The ...
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Was the speed trim system on the B737 Classic modified to counter increased thrust?

How much additional thrust did the 737 classic generate compared to the original 737? Was the speed trim system added to counter the additional thrust?
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Why does not jet engines have a metal grid in the front? [duplicate]

An aircraft engine can get destroyed if a large object - like birds - enters it while running. I'm probably naive, but this seems pretty easy to solve. Why not just have some kind of metal grid in ...
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1answer
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Why are liquid ring compressors not used in a jet engine?

A question has been asked here before whether sliding vane compressors could be used in place of axial compressors on jet engines since they have a high compression ratio per stage (Why were rotary ...
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1answer
149 views

Are four-engined airplanes calibrated to put out the same thrust for both their inner and outer engines?

Is there a slight difference baked into the aircraft's throttle control systems or are they always pumping out the exact same thrust as each other?
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1answer
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What “jet engine” is featured in this ad that Simone Giertz made for a phone?

Simone Giertz's video "Having Dinner With a Jet Engine/Leaf Blower" has a number of views of the turbine, on a cart, with a ducted fan attached. This side view is the best view, in my opinion. I put ...
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2answers
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Are compressor maps for multistage compressors drawn for one blade row or the whole compressor?

Apologies if this is a stupid question. I am a little confused about compressor maps. Are compressor maps such as this one, drawn for one blade row only or the whole compressor? (source: Wikimedia) ...
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1answer
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How does the Harrier avoid engine damage when operating from dirt fields?

The Harrier V/STOVL jet was designed in order for its users to be able to retain a functional air force even with all conventional airports destroyed; to this end, it can take off from, and land in, ...
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2answers
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What is a jet engine's fuel flow at constant IAS?

Here is my assumption: In straight and level flight of a jet turbine engine: One IAS = One drag = One thrust = One fuel flow Therefore, the fuel flow will be approximately the same for a ...
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0answers
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Is there a way to determine maximum rpm for axial compressor due to material limitations?

I'm looking for RPM to Stress relation to determine maximum rotational speed that compressor/turbine blades can have without undergoing deformation due to centrifugal tensile stress. I've come come ...