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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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2answers
115 views

Why Engine Exhaust Nozzle can not be totally buried in aircraft fuselage? [on hold]

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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2answers
58 views

In turbojet engines, does the fan play a key role in the air intake to the inlet? [on hold]

In turbojet engines, does the fan play a key role in the air intake to the inlet?
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1answer
122 views

Are turbofans compensated for gyro effect?

In a multi-spool design is the gyro effect canceled or mitigated by having the two or more spools spinning in different directions?
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1answer
174 views

Why B-52 was not re-engined as a more efficient 4-engine? [duplicate]

Why B-52 was not re-engined as a more efficient (also for maintenance) 4-engine but is still an 8-engine aircraft? In history, almost all others models were re-engined with new engines also quite ...
4
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1answer
162 views

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 ...
3
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1answer
151 views

Can a turbofan engine have less noise so that it doesn't disturb our ears?

A few years back I have seen that Pratt and Whitney 's Geared Turbofan Engine(GTF) has reduced it's noise levels to about 50%. But recently I was having a discussion with a friend and he told me that ...
1
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3answers
216 views

Is there a practical carbon-free jet fuel?

For example, when I want to use a small turbojet or low bypass turbofan as both the APU and bleed air supplier for blown flaps, ailerons, elevators, (like the ShinMaywa US-2 amphibious plane) and ...
16
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2answers
1k views

What is that CFM56 with a toothed exhaust on an A321?

I stumbled upon a wikimedia picture and I saw something that I have not seen before: a CFM56 with a toothed engine exhaust. Can someone explain to me what engine variant that is? Source Author: ...
2
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1answer
98 views

What is the aircraft in the 'Be Altitude' album cover?

In 1972, the Staple Singers released the "Be Altitude" album, which has them posing in a jet engine's intake. My question is what aircraft does that engine belong to? And why would someone let them ...
11
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2answers
755 views

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 ...
3
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2answers
138 views

What are the issues involved in converting a quadjet into a twinjet?

As you are probably all aware already, the fewer engines you have, the better your fuel efficiency; that’s why the airlines are selling off their (quadjet) 747s and buying (twinjet) 777s, why they’ve ...
3
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2answers
153 views

Why aren’t any JP-1-type (extreme-narrow-cut) fuels in use today?

JP-1 was the first U.S. military standard jet fuel (hence the 1 in the designation), with its specifications issued in 1944; it was an extremely narrow-cut, high-alkane kerosene, not far from what ...
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0answers
57 views

What is the minimum size of a ramjet?

Having recently learned that 155 mm ramjet artillery shells are now a thing, I wonder how much ramjet engines can be miniaturized. Could we see ramjet tank shells? Man-portable recoilless guns? ...
2
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2answers
195 views

How do bearings in a jet engine keep water out when it's been cleaned?

When a jet engine is running, it's generally immune to any liquid in the incoming air as the liquid would have been evaporated in the compressor. However, when the engine is being cleaned for carbon ...
1
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1answer
143 views

Who should design the nozzle of jet engines on aircraft?

There is a question in my mind that which company should design the nozzle of jet engine - the aircraft designer or the engine designer? If you watch this documentary: BBC Documentary Rolls Royce ...
1
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1answer
135 views

Why does the Convair 990 produce this howling sound during landing?

Watching this video of a landing Convair 990, one can hear a whooshing howl at about 0:11-0:12, as it flares just prior to touchdown (not to be confused with the run-of-the-mill howling that you can ...
26
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4answers
13k views

Why didn’t the Captain of Cathay Pacific flight 780 shut down engine 1 and land with a more reasonable speed?

In the approach phase, engine 1 of Cathay Pacific flight 780 got stuck at about 70% N1 and it forced the crew to do an overspeed landing (230knots). Why didn't they shut it off by turning the fuel ...
5
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1answer
350 views

Why Western fighters' afterburner glow is reddish orange while Eastern Bloc fighters' is blue?

Recalling what little physics I know, this could be explained by two factors: The blue color is given by the characteristic EM radiation of C-H bond breaking, C- and H- radicals forming and ...
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1answer
143 views

What percentage or airplanes have engines [closed]

I heard that some airplanes don't have engines. how many airplanes in the world have engines?
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1answer
136 views

Increase to Flight idle during start-up?

Ground idle takes about 5% of the total rpm, flight idle takes about 85% of the total rpm. Why is so much of the engine power wasted before it gets to flight idle?
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4answers
191 views

How is vertical speed managed in Airliners? [duplicate]

When an Airplane starts to take off, the Horizontal velocity would generate it the necessary lift, and then Airplane pitches up to further increase the lift. As the Airplane is climbing up, the net ...
3
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3answers
108 views

Would there be a purpose for a set of compressors in an electric turbo fan?

This is actually a two part question. Would there be a purpose to a compressor in an electric turbofan where there is no need for a combustion chamber, and if not, is there then a purpose for a bypass ...
0
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2answers
107 views

How do engines cope with various intake airflow speeds?

On a recent trip out of Washington Dulles to San Francisco, our B777 met with 200+ mph headwinds (as per the passenger entertainment system) at 35,000 ft for the first half of the route, before ...
10
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5answers
3k views

Why didn't Boeing or Douglas make a jet airliner before the British DH Comet?

I was looking at the history of commercial aircraft and was wondering why UK-based De Havilland was the first to produce a jet powered airliner (the DH 106 Comet) when the US had a much bigger civil ...
3
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1answer
137 views

What is the purpose of the pressure relief door fitted on the PW1127G-JM engines of the A320NEO?

Hey guys many times during my exterior walkaround I noticed on the A320NEOs that they have this pressure relief door and our SOP for the exterior walkaround states to check that this door is closed. ...
2
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1answer
134 views

Why is there a minimum altitude for at least some high-speed jet engine restarts?

While reading this other question about envelope constraints for jet-engine restarts, I noticed something odd in the graph provided (of the relight envelope for the Honeywell HTF7000 medium-bypass ...
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3answers
146 views

What are the advantages of using a ramjet in an air-to-surface missile?

Which are the advantages of using a ramjet compared to a rocket engine in an air-to-surface missile? I suppose the cost rises a lot, so why do some countries use ramjets as a way of propelling ASM ...
2
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0answers
46 views

Acoustic analysis from an aircraft engine?

I have found it surprisingly easy to find information on jet engines; however, I've been unable to find acoustic information so I can make a noise spectrum model. I'm looking for oscillations from ...
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1answer
84 views

How does the debris rejection system in the CFM LEAP engines work?

How does the debris rejection system in the CFM LEAP engines work? LEAP - The debris rejection system
20
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1answer
6k views

What are these “pimples” on the jet engine for?

When looking into the General Electric CJ 805-23B jet engine, I have discovered that all forward section of the compressor is covered by a number of near identically looking "pimples". What are these ...
2
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0answers
45 views

How are compressor maps drawn?

I've always thought they are empirically derived: once you have your axial compressor phisically in a bench, you set both a rotational speed and a mass flow throught the turbomachine then you measure ...
0
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2answers
69 views

How to calculate power required to drive an isolated fan of a TurboFan engine?

If I isolate the fan from a TurboFan jet engine (specifically GE90) and power it electrically with a motor, how much power is required for the electrical source to drive the fan to give the same ...
0
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5answers
260 views

I wonder if it's possible to make a “compressed air” turbine engine [closed]

I wonder if it's possible to make an efficient turbine engine that uses only hot compressed air to move but only that, meaning there is no ignition involved. To put it simple can we use compressors ...
2
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1answer
566 views

What exactly is an “engine surge” in a jet engine, and what causes it?

Surge suggests that something speeds up, yet I read elsewhere that in fact in jet engines, an engine surge is actually a compressor stall. Whether that is correct or not, what exactly is doing the ...
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3answers
109 views

Is it possible to calculate possible fuel savings of known turbofan engines if operational heat could be increased [closed]

Starlite is liquid paint like substance invented in 70s and perfected in the 80s by the late British inventor Maurice Ward (1933-2011). It is said to be able to withstand heat from 78 nuclear ...
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0answers
35 views

Adjusting nozzle shape for reduced flow rate

Suppose i have a ramjet engine, but in the combustion area i make an opening along the whole cirumference (a slit) feeding a channel, in which the pressure is the same as in the combustion chamber. ...
1
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1answer
165 views

Does preheating fuel before it reaches the turbine result in a performance improvement?

Preheating fuel before it reaches the combustion stage was first proposed several decades ago as a way to improve mixture, fuel economy, and to reduce emissions in car engines. One example of this ...
0
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1answer
94 views

Is jet fuel typically injected before or after the flame holder in an afterburner?

I don't have the best grasp on the intricacies of afterburners but I'd assume that if the engine has a flame holder then fuel would be injected before it in order to allow it to heat up to ...
5
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2answers
309 views

How do I optimize a turbofan engine to fly lower and slower instead of higher and faster?

I was reading something about someone who was doing this and I'm intrigued, but I have no idea what you actually do to optimize the engine to be better at lower altitudes and lower speeds?
17
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4answers
3k views

Why do uncontained engine failures still occur?

One of the absolute requirements of an aircraft turbine engine (usually some sort of turbofan or turboprop) installation is that, in the event of a destructive failure of the engine, the engine ...
0
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1answer
486 views

What is significance of N1 and N2 in Jet engine? [duplicate]

Why N1 Low pressure compressor RPM and N2 High Pressure compressor RPM are monitored in jet engines ? Why specifically compressor RPM rather than turbine RPM ? What do N1 and N2 signify in terms of ...
3
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2answers
341 views

What position was this photo of a jet engine taken from?

From that aviation photographer, I saw that beauty: Having in mind the jet engine I would see, let's say as a normal passenger, I am not really able to understand from where I am looking at that ...
3
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1answer
93 views

What is the difference between active tip clearance control system and passive tip clearance control system in turbine?

What are the main differences between turbine active tip clearance control system and passive tip clearance control system?
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1answer
140 views

Turbofan design parameters [closed]

I am writing a model for LM Prepar3D to simulate the flight model of a commercial airliner. The specification I am following requires some parameters from the engine (CFM56). ...
0
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1answer
104 views

Where could I find the FOD examples of C17? [closed]

I want to find some FOD examples of huge planes in reason of ground vortex,where should I go to search?
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1answer
114 views

Bright exhaust in afterburner vs no visible (bright) exhaust when not in afterburner?

When a jet engine has its afterburner engaged, a bunch of fuel is dumped into the back of the engine for additional thrust. This burning fuel causes the exhaust and inside the engine to glow brightly,...
3
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1answer
307 views

Why aren't there any jets with horizontal-stabilizer-mounted engines?

Looking at the spectrum of where jet aircraft put their engines, there are examples of almost every place that could conceivably used to carry a jet engine: slung under the wings buried inside the ...
0
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0answers
63 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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0answers
118 views

What happened with the Boeing PETA Pulse Jet Engines

The boeing engines created a buzz when they were announced back in 2011, and were said to be proprietary technology. It created a buzz about easing VTOL concepts and more, but where does the project ...
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2answers
168 views

How does fuel flow and altitude affect the compression ratio of jets?

Does the compression ratio of jet engines change with altitude and/or with the rate of fuel flow?