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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13
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1answer
2k views

What are these small engine inlets on the Super Hornet?

Does anyone know what these two small variable inlets on top of the engines are used for on the Super Hornet? Source: navy.mil; cropped
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1answer
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Why are engines angled toward the fuselage?

Source: twitter.com I saw a picture of a 777 from overhead and I was wondering why the engines point "in" to the fuselage, rather than being parallel to the fuselage.
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What advantage does Kawasaki C-2 have with a twin-engine configuration as compared to its competitors like An-70 or A-400?

While reading about various military transports, I came across the specs of Kawasaki C-2 and a few questions popped up. So please bear with me here if I list them all together as points, I hope ...
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What is a compressor cascade?

Is a compressor cascade just the representation of the blade ring of an actual turbomachine? What is the difference between linear cascade and annular cascade? A diagram or a reference would be great.
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How is fuel ignited in jet engines? [duplicate]

From what I understand, in jet engines, air is compressed and fuel is not only injected but also ignited : how is this done ?
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1answer
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Is a fuel that reacts with another to form hydrogen for fueling aircraft possible? [closed]

Hydrogen is the most abundant element in the universe and has great properties when reacting with oxygen for use as a fuel. Yet here on Earth, its production is prohibitively expensive, its storage ...
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1answer
358 views

Why does the 737NG EGT drop during take-off?

I noticed that the EGT drops a bit when I hit TO/GA for take-off on a 737-800.
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2answers
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Why does each fan blade have a different mass and frequency?

From a documentary (at 16:39) on building a Rolls-Royce jet engine: ... no two finished blades are exactly alike, and with twenty in each fan, it will only spin smoothly if the blades are perfectly ...
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2answers
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How do turbofan internals handle the load from the thrust?

To my understanding, turbofan engines get the majority of their thrust from the fan in front of the engine, up to around 70-80% while the core flow generates around 20-30%. Forward movement is ...
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Can you fly 2000 miles on an engine that costs less than $500k? If so, what type of engine?

Ok so Im exploring ways to bring cargo and medical supplies to various rural cities in say Africa without relying on ground infrastructure. Just short and cheap runways spread around the continent. It ...
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Jet Engine Cooling, HTC and cooling calculations

Right now I am working on a project about cooling systems in jet engines. And I don't have a supervisor to ask anything. I would like to know what is the most useful resource (book, analsys programs ...
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3answers
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Can Flex thrust be lower than climb thrust?

Let's restrict this question to airliners with 2 jet engines. For the remaining of the question, I'll use the term flex to designate reduced take off thrust as I'm more familiar with airbus's systems....
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GE90-115b turbine horsepower

The GE90-115b is rated at 513 kN maximum thrust and is often said to have 110,000 shaft horsepower, but I have yet to find any document or specification that backs the claim on horsepower figure. A ...
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3answers
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Turbofan engine start - Why does ignition occur so early?

In another thread, two key steps of starting a turbofan (ignition and fuel introduction) are given as follows: With increased N2 rotation, ignition will be turned on. [...] With further ...
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0answers
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How is the A320neo engine different from the A320ceo engine?

I've looked up at internet about the differences. And the only difference they mention is that the new engine has a higher bypass ratio (making it more fuel efficient), quieter and has an improved ...
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3answers
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If pilots in a A320 or 737 had a dual engine failure, would they add flaps for the landing?

Would this not be smart to do because you may come in a little fast, therefore the flaps would send you back up? Or would you absolutely want flaps in this situation
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1answer
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Why is the inlet cone shaped conical?

Why are inlet cones of a lot of aircrafts conical. I read that it has something to do with slowing down supersonic airflow entering inside the engine. Is this true? If so, can somebody please ...
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2answers
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What is this large engine doing on a B52?

In this YouTube video, discussing plans to use the 747 as an aircraft carrier, there is a brief sequence starting at 4 min 14 s, showing images of a B52: What is the explanation for the very ...
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1answer
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If the modern airliner was redesigned from scratch, would it look functionally different? [duplicate]

If the modern airliner (Boeing/Airbus) was redesigned from scratch today without any need for "backward compatibility", would it look functionally different from the current design? And if so, what ...
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1answer
162 views

What exactly is engine design speed?

Any further information is welcome, this is what I have learned so far: Engines are designed to operate at a certain RPM (N1). The compressor consists of small 'wings' which are fixed in position, so ...
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1answer
97 views

The principle in 'Trompe' is applied to airplanes?

'Trompe' (see Wikipedia) is a water-powered air compressor, commonly used before the advent of the electric-powered compressor. A trompe is somewhat like an airlift pump working in reverse, used to ...
2
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1answer
210 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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3answers
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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
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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
167 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
196 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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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
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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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1answer
271 views

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
322 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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2answers
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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
112 views

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
950 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
133 views

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
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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
81 views

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
190 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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