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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Where does turbine vane and blade cooling air come from?
Some large jet engines have a high combustion temperature to increase maximum thrust. First vanes and blades of the turbine must be cooled to prevent them from melting. One method is to circulate cold ...
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How can engine positioning affect flutter tendency?
I understand that moving the engines towards the wingtips would increase flutter tendency, but are there any other positioning options which could affect flutter?
How about moving the engine ...
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Is it currently possible to build a jet engine with 1,050 kN of thrust? (236,049 lbf)
Do we currently have the engineering know-how to build a 1,050 kN jet engine?
This question originated from the idea of changing a 4-engine aircraft into 2-engines. I chose the A380 since it seems to ...
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How much air, by mass, enters an average CFM56 turbofan engine cruising per minute?
How many kg of air enters an average CFM56 turbofan engine cruising per minute?
I have looked everywhere and cannot find it or figure out how to find it, if you could either tell me or give advice on ...
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What is the future of manufacturer independent jet engine maintenance repair and overhaul (MRO) services?
I have noticed that Air France KLM offer a Maintenence (MRO) service for aircraft and jet engines. This sounds like a potentially big threat to engine manufacturers like Rolls Royce who makes around ...
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Can the thrust of a turbofan be increased by increasing bypass ratio?
I read that the CFM56 is based upon the F101. Id on't know how true that is, but it generated the following question: If a larger fan is fitted to a low bypass turbofan, would dry thrust be ...
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What is the fan tip speed at maximum thrust?
What is the fan tip speed at maximum thrust? Is it any different for a Rolls-Royce Trent 900 (powers the Airbus A380) and Pratt & Whitney PW6000 (powers the Airbus A318)?
Are they efficient at ...
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What fraction of air intake becomes bleed air in airliner engines?
Gas turbines typically bleed air from the late compressor stages. Some of this air bypasses the combustion chamber and is expanded through the turbine to prevent the blades from becoming too hot. I ...
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How are compressor disks connected to the shaft?
I am trying to learn how compressor disks and shaft are connected each other. I don't have any idea about the terminology so I couldn't find anything useful.
Here is a section view of a sample and I ...
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Is it possible to create a direct supersonic airflow to a turbofan's afterburner in order to enhance the performance or reduce the fuel consumption?
so I found out that SR-71 Blackbird is using what's called "turboramjet" and I find the idea a bit appealing since they say with such engine, the Blackbird is more fuel efficient at it's top speed. I ...
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How can the landing gear fit in the small room in the engine bay on the Tupolev Tu-144?
I recently went to the museum in Sinsheim, Germany, where a Tupolev Tu-144 is on display. I noticed that the landing gear of this plane is actually way wider than the space it has available when ...
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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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Can supersonic conditions be replicated on the ground?
In a previous question the P&W J 58 engine for the SR-71 was discussed. The engine was a new and innovative design combining the characteristics of a turbojet and a ramjet.
Before flying with ...
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Why don't 747s use unreliable, but cheap, jet engines instead?
I'm a neophyte who was reading a little bit about jet engines, and the economics behind them. In particular, I was curious about what makes jet engines so expensive compared to piston engines.
A ...
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Are German, Japanese, and Chinese companies not able to build aircraft jet engines on their own?
As far as I know, only 4 countries can build aircraft jet engines on their own:
USA {GE, P&W}
Russia {Klimov, NPO Saturn}
France {Safran}
UK {Rolls-Royce}
All other countries use jet engines ...
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What is an afterburner and how long can a jet fly on afterburner?
I heard this word so many time in military documentary about jets, especially fighter jets, but I don't fully understand what it is or how it works. In a documentary from the Discovery Channel, all ...
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Are engines automatically stopped in an emergency landing?
This answer made me wonder if engines are stopped automatically after an emergency landing as soon as one of the exit doors are opened.
(...) if the engine is still running, you're about to run ...
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What is a "core lock" on an jet-engine?
This question came up while reading the Wikipedia article on core lock and Pinnacle Flight 3701.
If my understanding is right then if for example inner parts of the jet engine heats up that so much ...
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How is supercruise achieved?
Wikipedia article tells that supercruise is a condition when an aircraft can achieve velocities above Mach one without using the highly inefficient afterburners. But still, there are not a lot of ...
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Why is the nacelle outlet of the tail engine of the L-1011 Tristar lower than the engine itself?
I've noticed that the nacelle outlet of the Lockheed Tristar is situated below the engine itself. It is at the end of the fuselage. The nacelle outlet of the tail engine of the DC-10 on the other hand,...
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Which jet engines have the highest thermal efficiency?
Some automakers (Mercedes-Benz, Toyota) have recently been making news about the improved thermal efficiency of their engines, stating that they reached the 50% mark. I was wondering if it was the ...
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Do F-22's use cartridge start to start engines?
What method does the F-22 use to start its engines?
In the video below, you can see a flap open and flame and steam shoot out as the engine starts to spin up. Is this an example of cartridge start? ...
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Why does a jet engine acquire a metallic whine when in full power? [duplicate]
I had a flight yesterday on an AA Embraer ERJ-190. As the plane idled at the end of the runway there was the familiar high-pitched jet whistle, which increased in pitch as the engine started spinning ...
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Would a tumbleweed sucked into a jet engine on takeoff cause a serious problem?
I saw tumbleweeds going across flight path in El Paso, TX and it made me wonder, especially after seeing what birds can do.
Would a tumbleweed ingested by a jet engine on takeoff cause serious ...
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What is the difference between a high bypass turbofan and a low bypass turbofan?
I see some questions on the site that talk about the relative positives and negatives of a high bypass turbofan (HB) vs a low bypass turbofan (LB). But I don't see anything explaining what actually ...
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How much thrust is lost due to the bleed air system?
I've read that bleeding air for the pneumatic system from the engine core can produce important losses in thrust, and also rising the fuel consumption too. Today this problem is worse, with the more ...
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Why do jet engines take a long time to throttle down?
Apparently jet engines can take several seconds, up to ten or fifteen seconds, to go from full power to idle.
Why is this? Can't a simple fuel valve shut off fuel flow? Or reduce it to whatever flow ...
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How much thrust can the thrust reversers create?
Let's say for the sake of the question, the plane is an 787 Dreamliner and the engine is the General Electric GEnx-1B64 (that according to Wikipedia can produce a maximum thrust of 284 kN)
In ...
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How long does it take to restart a turbofan engine inflight?
I'm especially interested how long it would take to restart a turbofan engine after a hypothetically erroneous shutdown of an engine immediately after takeoff i.e., at an altitude at which the air is ...
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What is the difference between side-by-side vs under-cockpit engine intakes?
What is the main difference between these two engine configurations?
What are the differences between planes that have the intakes below the cockpit as compared to those who have them on the sides?
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What drives and/or allows the move to higher-bypass turbofans on jetliners?
Note: I'm by no means an expert on any of this, I'm just curious.
There seems to be a general trend toward higher and higher bypass ratios in commercial jetliner engines. (I'm thinking here of 737/...
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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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What is a normal EGT range of a jet engine?
Out of curiosity at what temperatures are the exhaust gasses are expelled from jet engines? A normal reciprocating engine from what I recall should be in the 700 - 1100 degrees Celsius range. Does ...
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What are the reliability statistics for modern jet engines?
What is the actual numerical reliability statistics of the modern, large-aircraft, commercial turbofan engines available today?
e.g. How many running hours can we expect a failure after? Are there ...
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How was the high-bypass concept invented?
(Source)
Wikipedia says:
After [the Ryan XV-5 Vertifan demonstrated] that large amounts of air could be moved through a lift fan, an 80 in (2.0 m) tip drive fan turned through 90 degrees, driven ...
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How do contemporary Russian jet engines compare to Western ones?
How do contemporary Russian aircraft engines like the PS-90A1 and PD-14 compare
to similar engines from GE, PW, Rolls Royce and CFM International? How many years/generations they are behind their ...
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Are there any pressurized piston-engine aircraft?
Are there any pressurized piston engine-powered aircraft? Or does pressurization require a turboprop or jet?
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Why is a higher bypass ratio more efficient at lower speeds?
Why is it that a larger volume of air moving slower is a more efficient means of propulsion than a smaller volume of air moving faster? (This is true up to a given speed, obviously, as supersonic ...
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Why do turbofan engines not have a contrarotating second fan?
Why aren't planetary gears used to have a fan in front of the fan in a turbo fan engine. Would this not lower energy consumption etc?
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How much would it cost for a large airline to switch engine manufacturer for their planes?
I am trying to understand how much of a hassle and cost it would be for a large civil airline, who already had lots of installed Rolls Royce engines on its fleet, to switch over to GE engines on new ...
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What is the average speed used by modern jet fighters when in dogfight?
I am asking this question pertaining to a game I'm designing.
It is well known that many modern jet fighter aircraft can fly at supersonic velocities however I read that this top speed is hardly ever ...
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How often does fan blade out happen?
Jet engines are designed to contain a fan blade failure, and the engines and airplanes are designed with this type of failure in mind. This is more critical in the modern high-bypass designs with ...
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What exactly is a compressor stall?
I hear the term "compressor stall" when talking about turbine engine difficulties.
What exactly does this mean? And how does a pilot diagnose and fix it - specifically, would there be any changes in ...
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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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Is it possible to have an afterburner in a turbofan with bypass ratio greater than 1:1?
Is it possible to have an afterburner in a turbofan with a bypass ratio greater than 1:1? At 1.05:1, say, can it have an afterburner?
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What is the theoretical maximum velocity of electric aircraft?
I'm wondering about theoretical maximum velocities of supersonic electric aircraft. I think the fastest demonstration of any type of aircraft has been close to mach 10. This was done using a rocket ...
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Why is there a pressure drop in the combustion section of a jet engine?
This image, referenced in this question, shows in green the pressure value in a jet engine:
The combustion section between compressor and turbine is where fuel is injected, mixed with air, and ...
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How is flame stabilisation carried out?
How is flame stabilization done in a jet engine combustion chamber?
What are the various ways of doing this?
What are the challenges/ problems faced?
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What are these holes in the engine inlet?
In the next picture can be seen within the housing, near the inlet:
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What throttle setting does an airliner use while cruising?
As a passenger, I have always felt like the engine are not kept at take-off thrust/full throttle a few (tens of) seconds after take-off, and so for obvious reasons as fuel efficiency, engine wear ...
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