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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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1 answer
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Name of this part of jet engine inlet

I can't find any name of it. I see it on some gas turbines but not all of them. Edit: Found them, they are called struts.
Adam Dutkiewicz's user avatar
4 votes
2 answers
2k views

I'm having a hard time conceptualizing this statement from "The Jet Engine" by Rolls-Royce

This is taken from section 21 of Chapter 3, Compressors that discusses axial flow compressors in turbine jet engines. The more the pressure ratio of a compressor is increased the more difficult it ...
shrimp's user avatar
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2 votes
2 answers
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Lightoff to speak about an engine start

Why is the term lightoff (or light-off) used to describe the moment an engine ignite/is started ? I'm wondering why the suffix 'off' is used in an 'ON' sense (start, ignition) ? Is there a ...
Vincent's user avatar
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4 answers
298 views

Why cant all planes use the best engines like the GeNX or the Trent XWB?

Why do airline manufacturers not prefer using the best engines(max thrust: weight ratio and best efficiency) for their airplanes? Doesn't this just not lead to lower sales and losses for the company? ...
Sambhav Khandelwal's user avatar
0 votes
2 answers
72 views

How do tubojets compare to afterburning turbofans in terms of efficiency?

Turbojets used to be more common in the 40's and 50's but once jet engine design matured they pretty much went extinct in favor of the more efficient turbofan. I know one advantage of the turbojets is ...
shrimp's user avatar
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2 votes
0 answers
165 views

NASA's and Boeing truss-braced wing fuel savings breakdown

According to its Administrator Bill Nelson, NASA is working on a project with Boeing that will reduce single-isle aircraft fuel consumption by 30%. He described it as a higher and thinner wing and ...
phil1008's user avatar
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2 votes
1 answer
163 views

Is it a good idea to increase exhaust duct length?

I am a big newbie in aviation but still, I have a question: Let's assume a civil aircraft (Boeing 737 or Airbus 320), flying with those impossible real life hypothesis: the exact SAME turbofan are ...
user12642493's user avatar
0 votes
1 answer
119 views

How did the engines on the ME-262 work? [duplicate]

I have been looking into the ME-262 jet engines recently but cannot quite understand how they worked and was wondering if anyone could explain it to me in a simplified way.
Jordan Stephan's user avatar
13 votes
2 answers
6k views

Can jet engines stay running without electrical power?

A piston-engine aircraft will continue to run as long as its magnetos still work, even if there is zero electricity in the battery and the alternator is broken, because magnetos are independent of the ...
marxman28's user avatar
  • 131
7 votes
1 answer
2k views

Is the clamshell on the AN-72 what causes the Coanda effect?

The AN-72 uses the Coandă effect to improve lift and give it better STOL features. In this image of an AN-72 (presumably on a takeoff roll) one can see a clam-shell bucket open at the top of the ...
FreeMan's user avatar
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11 votes
3 answers
7k views

Why aren't all fighter jets' engine intakes on top instead of forward?

Reading the question and answer to How does the Yak-130 fly with blocked engine inlets, I am now wondering why it - or any fighter jet - has forward engine intakes at all? The top and accepted answer ...
mmathis's user avatar
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15 votes
1 answer
4k views

How does the Yak-130 fly with blocked engine inlets?

In this Yakovlev Yak-130 youtube video you can see at 2:45 where it closes the inlets(something I've never seen before, I've only seen the typical engine inlet covers) and then it does a perfect take ...
Gabe's user avatar
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8 votes
6 answers
9k views

Scared of flying in an Airbus A220

The A220 is exclusively powered by PW1500G geared turbofan engines, which have a history of reliability issues. Multiple airlines grounded their entire A220 fleet amid engine concerns (A220 Engine ...
Jim's user avatar
  • 107
0 votes
1 answer
126 views

How do after-burners work on jet planes?

I've always wondered this after getting introduced to fighter jets, the sheer concept of being able to create a larger "exhaust" out of a fighter jet and cause it to speed up has always just ...
Somebody Weird's user avatar
1 vote
1 answer
155 views

Exhaust temperature of CFM56 engines range (Nozzle downstream temp)?

EGT is available but not the temp of the exhaust nozzle in the CFM56 series.
Setare's user avatar
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10 votes
6 answers
3k views

Function of the compressor in a gas turbine engine

I am trying to understand the importance of having compressed air in the combustion chamber of a gas turbine engine. As far as I understand it, the reasons are twofold. Firstly, the compressor is ...
bchen's user avatar
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3 votes
0 answers
120 views

What legacy turbojet would have detailed documentation and drawings available for free or cheap?

I am fascinated by the technology of jet engines. As a hobby, I might like to create a detailed animated 3D model of one (and publish it with a Creative Commons license). Obviously I am not going to ...
tml's user avatar
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1 answer
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Why are these characteristics of the FT-180 highlighted?

I have been checking the FT-180 engine used to establish speed record for remotely controlled aircraft (i.e. model airplanes). There are some specific features highlighted on the manufacturer site. I'...
totalMongot's user avatar
9 votes
4 answers
6k views

Why are there (almost) no civilian single engine jet aircraft?

I have been looking at various engine configuration in jet powered aircraft. Most have 2 jet engines mounted either side of the fuselage, there are trijet models (e.g. B-727, MD-11) there are also 4-...
Aleks G's user avatar
  • 455
3 votes
1 answer
398 views

How would you know the difference between a compressor stall and a surge based on indications in the cockpit?

I understand the difference between a compressor stall and surge. Stall: One or two blade stages exceed the critical AoA, the airflow is turbulent, and the smooth airflow through the compressor is ...
Breaach's user avatar
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1 vote
1 answer
134 views

why you have to open 6 bypass valves in the J 58 engine?

I've noticed that the bypass valves in J-58 are opened after M=1.6. I don't understand why and what are the differences between the J-58 and a normal turbojet that reeaches more than M=1.6.
marco iob's user avatar
1 vote
1 answer
289 views

What are the air source settings for on the F-16?

As part of the start up sequence for the F-16, the "air source knob is set to NORM", according to this source: https://theaviationgeekclub.com/heres-why-starting-the-engine-on-an-f-16-viper-...
AlphaCentauri's user avatar
12 votes
3 answers
2k views

Does the other engine have to go through extra checks when one engine fails

Many times I read articles on sites like aviaton herald about engine shutdown in fight because of some problem. It's given the problematic engine will be repaired. Question is about other working ...
user871199's user avatar
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2 votes
3 answers
319 views

Why no CFM-56 for the E3?

Why did the USAF not upgrade the E3 from TF33 engines to the CFM-56 like they did the KC135? From the Wikipedia page on the E3, the latter variants sold overseas had the CFM-56 from the factory and ...
RetiredATC's user avatar
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0 votes
2 answers
248 views

Why aren't ducted rotors used in gas turbines?

I am wondering why (for what I know) no gas turbine employs ducted enclosures for blade arrays on rotor stages. I tried to search the internet for resources but I couldn't find anything related (so I'...
temporary_pigeon's user avatar
9 votes
1 answer
2k views

Why do only turboprops have ground/flight idle selections?

Why is it that only turboprops have a pilot controlled flight/ground idle and not jets?
Boeing787's user avatar
  • 6,454
2 votes
1 answer
205 views

How do engine doors work?

"Doors" here refers to something in or around the engine that can close or open, stopping or allowing the flow of air (or some other gas). I've heard of such things in a few engines. GE9X ...
DrZ214's user avatar
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2 votes
1 answer
269 views

Why do the engine of MiG-31 spit out flame when going for afterburner?

I was seeing this image. Always we can see an abnormal flame spit out of the engine when the pilot goes for afterburner. Why?
Roh's user avatar
  • 3,329
0 votes
1 answer
195 views

Decreasing Area of Axial Compressor

in axial compressor, why the area is decreasing until it reaches the combustor? and if the answer because of the pressure is inversely proportional to the volume. that's happened when the temperature ...
Nagy Ashraf's user avatar
9 votes
2 answers
5k views

Could a jet engine theoretically ingest not only oxidizer but fuel (on planets like jupiter)

Jet engines work by ingesting oxygen from the air and combusting it with an onboard fuel source like kerosene. But, on planets like Jupiter, with an abundance of hydrogen, would it be possible to ...
Daniel Shepherd's user avatar
5 votes
3 answers
920 views

How does momentum thrust mechanically act on combustion chambers and nozzles in a jet propulsion?

I'm asking this question since I can't intuitively understand how the acceleration of mass flow and therefore the increase of its momentum can actually mechanically act on the combustion chamber ...
MK.s's user avatar
  • 65
2 votes
1 answer
158 views

The phase having the hightest TIT for a flight mission

I have a query concerning the turbine inlet temperature (TIT) in the context of various flight mission phases. Specifically, I'm trying to ascertain at which phase the gas turbine reaches the highest ...
mumu's user avatar
  • 21
1 vote
2 answers
137 views

Does the obstruction in a propeller duct increase exhaust pressure or decrease pressure/increase speed?

I came up with this question when looking through the answer for this question, which states that a convergent duct(obstruction) compresses the exhaust so that its pressure matches the ambient ...
Frank's user avatar
  • 415
-1 votes
2 answers
154 views

Why does thrust differ in different reference frames?

If a jet engine flies with 4 m/s in the air and we want to calculate thrust for two different reference frames, can we prove that the calculated thrust for both reference frames are equal to each ...
Jawel7's user avatar
  • 244
3 votes
1 answer
206 views

What causes subtle cyclical changes in engine volume at cruise?

A few years back, while trying to snooze on a Jet2 flight up at cruising altitude, my semi-attention wandered to the droning of the engine. I realised there was a very subtle effect of its intensity ...
Cantoris's user avatar
0 votes
1 answer
118 views

Why do we take into consideration holes for pressure thrust in jet engine calculations?

In many sources related to jet engine thrust calculations such as https://www.jet-x.org/a8.html , pressure thrust of a module such as combustion chamber, nozzle or compressor, is calculated by front ...
Jawel7's user avatar
  • 244
3 votes
3 answers
834 views

How can flow in the compressor of a jet engine go back to the inlet?

In aerodynamic lessons and books about jet engines, it is always said that there is a risk that air flow in the combustion chamber or compressor can go back to reverse direction, towards the inlet if ...
Jawel7's user avatar
  • 244
-4 votes
2 answers
165 views

Is diying a strong jet engine possible wih basic tools

Is it possible to manufacture a jet engine that provides 500 newtons of thrust with relatively primitive tools like a lathe or so , if someone did something similar can you provide me with the ...
Ahmed Radwan's user avatar
-1 votes
4 answers
3k views

Why do we consider that air comes into jet engine?

While calculating air pressure and temperature during cruise of jet engines, we consider that air comes into the jet engine inlet with our flight velocity. But why? In fact, air stops stagnant in ...
Jawel7's user avatar
  • 244
2 votes
0 answers
192 views

What's the reason behind the 787 and 777's "thicker" engine nacelle?

If you look at images of the 777 and 787 engines (both RR & GE), such as these pics https://upload.wikimedia.org/wikipedia/commons/thumb/e/e4/B787-2139.jpg/220px-B787-2139.jpg https://www....
Piranha Lama's user avatar
1 vote
0 answers
87 views

How can over-expanded flow go out of nozzle when it has less pressure than ambient pressure?

We know that over expansion in flow means that nozzle exit pressure of flow is lower than ambient pressure at specific altitude. It gets narrower while exiting nozzle causing loss in efficiency. My ...
Jawel7's user avatar
  • 244
0 votes
1 answer
116 views

What increases the rotational velocity of air in an axial flow compressor?

In an axial flow compressor as used in modern jet engines, the goal of a compressor rotor is to increase the angular momentum of the air by imparting an increase in swirl velocity. (Note: the goal of ...
interested22's user avatar
1 vote
1 answer
286 views

Do compressors and turbines in jet engines end with rotor or stator?

I am trying to understand compressor and turbine design principle based on stators and rotors. I know that turbines and compressors both have a rotating and fixed section that constitute a stage. For ...
Jawel7's user avatar
  • 244
2 votes
1 answer
239 views

Is there any existing engine which can be converted to turbofan from turboshaft in mid flight?

I read about convertible engines. I want to know if there is any engine existing to meet up hover and cruise together.
Eaza's user avatar
  • 121
6 votes
3 answers
442 views

What size jet engines would it take to make a Cessna 140 hover?

I'm building a STOL bush plane using 4 jet engines located at 4 different points on the aircraft. I would like to know what size jet engines it would take to hover something like a Cessna 140.
bryan lawless's user avatar
1 vote
2 answers
301 views

Why are inlet and outlet (exhaust) pressure considered to be the same in a turbojet engine?

Why do we take outlet/exhaust pressure (station 6) as the same as in inlet (station 1) ? In T-S diagram, we see that outlet temperature is much higher than inlet temperature since flow in outlet has ...
Jawel7's user avatar
  • 244
3 votes
1 answer
567 views

Why does Engine Pressure Ratio (EPR) rise as thrust levers are pushed forward?

I'm looking for an answer that at least addresses the fundamental thermodynamics of a jet engine. Jet engines use a Brayton cycle to get useful work out of a heat source. An ideal Brayton cycle engine ...
youguysfail's user avatar
1 vote
1 answer
140 views

Why does ITT drop drastically after startup?

Is this because of the increase of air that goes through the turbine that cools the parts?
Boeing787's user avatar
  • 6,454
1 vote
1 answer
960 views

What is the purpose of variable stator vanes in the power turbine part of a free shaft gas turbine?

both M1 Abrams tank and T-80 tanks have free shaft gas turbine engines and both of their engines have variable stator vanes in their power turbine part. It says in the picture below that these ...
Timothy Scherer's user avatar
9 votes
1 answer
700 views

Why the green inside newer turbofan engine nacelles?

What is the purpose of the recent phenomenon of green being seen inside newer turbofan engine nacelles, just to the front of the fan blades?
minijet88's user avatar
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