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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3
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1answer
60 views

From which stages is the bleed air from a GE90?

I'm doing a university project on the GE90-115b engine and I'm having a hard time understanding this EASA type-certificate data sheet. In particular I can't figure out the air bleed extraction section ...
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Are any jet engines used in combat aircraft water cooled?

Are any jet engines used in combat aircraft water cooled? If they are not, and instead are air cooled, how can the engine ensure consistent cooling? Wouldn't the airflow passing through whatever ...
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How much thrust could a 400 mm EDF produce?

There's a 195mm EDF from Schübeler that produces 25 kg of thrust at a peak power consumption of 15 kW: https://www.schuebeler-jets.de/de/produkte/hst Now, my question is: How much thrust could you ...
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1answer
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Why was there a rattling noise coming from the left engine of A319?

I recently flew on an Airbus A319. When boarding the aircraft from the front entrance we passed in front of the left engine. The fan blades were spinning and there was a rattling noise (like when a ...
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Why don't modern jet engines use forced exhaust mixing?

Jet engines are noisy[citation needed] - even a modern high-bypass turbofan is still deafeningly loud compared to pretty much anything except the even-louder low-bypass turbofans or a turbojet (much ...
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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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Why at increasing BPR the efflux area should be enlarged (at high BPR)?

I am working on a university project. I have to comment on this chart (that represents efflux area variation with the variation of the BPR). Every other engine data are kept unchanged (turbine entry ...
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2answers
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If the intake of a running jet engine is blocked for some short duration what would be the sequence of events following it?

If the intake of a running jet engine is blocked for some short duration what would be the sequence of events following it? Will it cause any damage to the engine parts?
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4answers
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On a bypass engine does the bypass air travel faster or slower than core air?

Using the convergent /divergent duct theory the low pressure cold stream bypass air would travel faster but I read on a web page that the bypass air travels much slower than core air. But again using ...
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What is meant by a “cold soak" of an APU?

What is the exact meaning of "cold soak" of an Auxiliary Power Unit (APU)? Is it to do with long flights at high altitude and the fuel getting cold? Will it affect the ignition of the APU? Can anyone ...
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1answer
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How are compressor blades connected to the shaft in turbojet engines?

The below figure is about rotor and stator blades of compressor . How these are connected to the compressor shaft in jet engines ?
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Non-dimensional variables choked nozzle

I understand that a choked nozzle removes the dependance on the static pressure $p_a$ because if M>1 in a choked nozzle then waves cannot travel upstream in the nozzle (as explained in the paragraph ...
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4answers
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Why does an Avro RJ85 have four engines?

The British-designed Avro RJ85 is a short-haul airplane with four jet engines. What is the purpose of four engines for such a small aircraft?
7
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1answer
283 views

Why weren't the rotor tips of the Djinn directly fed from the turbine's exhaust?

The Sud-Ouest Djinn seems to be pretty much the only tip-jet helicopter to have any sort of commercial success. It used a turbine to drive a compressor, which itself fed slightly warm air to pipes in ...
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2answers
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What is an accessory gearbox?

Many 737 engines have an accessory gearbox on the 9'o clock position, which is part of why the engine has a flat-bottomed shape. What exactly is an accessory gearbox?
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Advantages of square over circular engine nozzle?

The F-22 has square nozzles, while the Russian Sukhoi PAK FA has circular nozzles. There are both 5th generation planes, but with different nozzles, why?
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Is it possible to determine the mass flow rate through the engine of MiG-21 during its various cruise Mach no. operations?

Is it possible to obtain the mass flow through the Tumansky R-25 turbojet engine mounted on a MiG-21 during its various standard operating (cruise) Mach numbers? Note: standard as in older planes ...
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5answers
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Can jet engines be used for VTOL civilian aircraft?

Why do almost all civilian VTOL aircraft existing today use propellers (or rotors) for take off and landing and not jet engines (as the Harrier does)? Is there a technical reason for this?
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Could turbine or compressor stages of a jet engine be switched off to improve fuel efficiency?

Active fuel management is a technology developed by General Motors, which is used to improve engine efficiency in the times when the engine is operating under loads which are considerably less than ...
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3answers
137 views

Efficiency of Flyboard engine

From what I understand (not much), you need good specific impulse to travel long distances with, say, flyboard. I know that RP1 has good specific impulse. I wonder if he used it, and what type of ...
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5answers
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Is starting a jet engine without ground support possible?

We have had more... than... one question about jet aircraft taxiing about the airport without their jet engines running. Those address several issues such as cost vs savings and regulatory approval. ...
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2answers
285 views

How does an engine works when an airplane has $v=0$ on the ground?

I mean, for a turbofan: $$ T= \dot m_{air,h} (1+f) v_{e,h}+ \dot m_{air,c} v_{e,c}- (\dot m_{air,h}+ \dot m_{air,c} ) v_0+ (P_{e,h}-P_{amb} ) A_{e,h}+ (P_{e,c}-P_{amb} ) A_{e,c} $$ but $$ \dot m_{air}...
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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
45 views

How does Mach number of Jet engine vary with respect to Compression Ratio?

How does the performance of jet engine vary with Compression ratio. What are the variables that affect the Mach number of Jet engine.
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2answers
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Can we trade some efficiency to curb high-altitude emissions?

Considering our problematic issues, Emissions at high altitude Contrails ~10,000 premature deaths per year from airline emissions This is an area of concern where it's worth asking some stupid ...
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1answer
277 views

Is this plane safe to fly on? The turbine blades look damaged [closed]

While waiting for a recent flight, I observed this aircraft with what appear to be rather worn turbine blades. Is this close to being a safety issue or is it purely cosmetic?
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1answer
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What is the lifespan of an airline engine?

As per subject, what is the lifespan of a jet engine? Do they have a fixed hours which they can be used and regardless of the state have to be exchanged or are they serviced and maintained until they ...
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4answers
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How do jet engines work?

I was doing research about jet engines, and they seem really difficult to fully understand. So, can anyone explain it in a simple way? An afterburner glows on an F-15 Eagle engine, source: Wikimedia. ...
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1answer
126 views

What are the differences between the proportional flow control FCU and pressure control FCU?

what are the basic differences between the proportional flow control FCU and pressure control FCU? ( FCU : fuel control unit )
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4answers
267 views

What would be the impact of replacing the engines on the 737 MAX, not just reworking MCAS?

There has obviously been a lot of focus on the MCAS failure following from the 737 MAX crashes. However, the MCAS appears to be a compensating control for design decisions, specifically the ...
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Do rotating deflagration engines exist?

Pulsejets (which could have been called pulse deflagration engines) rely on pulsed deflagration to generate energy and thrust. Their pulsed mode makes them hideously loud and rather inefficient, but ...
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2answers
198k views

What is the difference between a turbofan and a turboprop engine?

I'm not an aircraft expert and I just realized that there are two different terms - turbofan and turboprop. I always had them combined in my head as a term for a large jet engine (like you would see ...
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3answers
253 views

Can a gas turbine be able to switch from torque to thrust?

Can a turbine engine be switched from providing torque (like a helicopter) to the rotor to transfer power to provide exhaust thrust (like a jet plane)? Related: BV-347 upgrade this way?
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How does jet engine water injection work?

How did the "wet takeoff" of old days work? Was the water used ordinary distilled water, or did it have additives? Where is it carried in the aircraft?
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Engine Oil Consumption limits part of certification?

Does anyone knows if Engine Oil Consumption limits are part of the engine certification requirements?
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2answers
216 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? ...
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1answer
268 views

Are turbine and compressor blades and vanes cast or forged?

I was wondering how blades and vanes are typically made in commercial jet engines. Would you typically use investment casting to make compressor blades or just in the turbine section to accommodate ...
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3answers
216 views

Is it better to have the engines center or apart on a plane?

Are there any advantages or disadvantages to having the engines closer or farther to the center of the plane? How is the ideal engine spacing determined length or span wise for performance? Related: ...
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2answers
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When are more engines better than not on a plane?

A model of this airplane was used to carry a space shuttle. In this picture below the airplane had a few extra engines added since then. How is the number of engines decided on an airplane? Why not ...
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2answers
9k views

Can a Boeing 767-200 fly at 510 knots at a height of 400 metres?

Can a Boeing 767-200 physically fly at 510 knots at around 400 metres altitude? If it did manage that speed, how likely would a structure failure be? Also, if those measurements were achieved, how ...
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0answers
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Why can’t the CF34 use wide-cut fuels?

The General Electric CF34 high-bypass turbofan (used primarily on the Bombardier CRJ and Embraer E-Jet regional jets), unlike the vast majority of jet engines (both civil and military), is not ...
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2answers
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What is so special about new Russian jet engine called PD-14?

I think PD-14 engine is being promoted by Russians as something extraordinary. What is so special about PD-14 that the West doesn't have? Can you explain this in layman's terms?
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Is this one of the engines from the 9/11 aircraft?

I ran across an interesting set of post-9/11 photos and I noticed this picture in particular: The closest item on the truck looks a bit like an airplane engine, but I can't tell for sure. Is it one ...
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Can old passenger airplanes be refitted with latest engines to extend their life and efficiency?

I was wondering if this might make sense as commercial aircraft design has not changed significantly (from the outside) in the last 50 years?
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1answer
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Difference between engine rev up and run-up

Explain please the difference between these jet engine terms: rev up run up Obviously they are completely different procedures. The reason I ask this question is because I'm not a native speaker ...
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1answer
260 views

Does the auto thrust at takeoff compensate for asymmetric engine characteristics?

When a percentage thrust has been determined for take off the auto thrust system (Airbus) or the auto throttle (Boeing) will send the data to the engines FADECs to provide the required thrust. When ...
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4answers
3k views

Why do airplanes use an axial flow jet engine instead of a more compact centrifugal jet engine?

Axial flow jet engines take up a lot of space. Centrifugal jet engines create high pressure. Can you create a centrifugal air pump that pushes as much air as a axial jet engine. Centrifugal air ...
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What is a jet engine tolerance for a bird strike? [duplicate]

Similar questions have been asked ; a partial answer is in 14 CFR part 33-76, stating 16 small birds ( 85 g) must be tolerated . But what other qualification tests are there ; for medium and large ...
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What is a “flare-out” and why does auto-thrust reduce thrust during flare-out?

The functions of auto-thrust include thrust reduction during a flare-out. What is flare out and why during flare out will the auto-thrust reduce thrust?
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Would a long pole help stablize a jet pack?

Jet packs are classically worn like a book-bag on the back. Would it be more stable if the exhaust ports were separated? Would the jet pack be easier to control if the turbines were at the ends of a ...