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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50 views

How do power and thrust curves compare?

I would like to really understand why when talking about jets we care about thrust but when talking about prop aircraft we care about power. (THRUST)="Just a force" (POWER)= work/time = ...
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What is this turbine engine panel that opens on landing?

Tonight I flew from Munich to Dortmund on an A319 and I happened to sit just above the wings and turbine on the right side. Upon landing, the turbine opened a window or panel which exposed some grid ...
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Is Flight Idle a constant?

Is "Flight Idle" for a jet engine a constant N1% value or does it vary with Altitude, and OAT?
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106 views

Can ramjets reach higher thermal efficiencies than gas turbines?

Since a ramjet isn't constrained by turbine inlet temperature like a gas turbine is, it seems to me that it should be able to achieve a higher thermal efficiency, given that it's operating at a speed ...
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Is this the relationship between rpm and thrust of a Turbofan? [duplicate]

In this graph from the FAA Airplane Handbook Chapter 15, page 5: It looks like it is talking about "jet engines" but is it engine type specific or it is for both turbojet/fan/prop/shaft? It ...
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Why would sea level static thrust have a takeoff and a maximum continuous value?

In the type certificate data sheet for a jet engine, there is this table static thrust is the thrust generated by the engine when the plane is at rest with respect to the Earth and the surrounding ...
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122 views

Why is thrust said to be constant over speed for a jet engine?

I'm just interested in some basic facts regarding flight. On reading the rather "low level" book "Understanding Flight, David F. Anderson, Scott Eberhardt), I recently came up to the ...
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Is the well known textbook-formula for net-thrust oversimplified or do I have a misinterpretation?

In order to understand how Jet-Engines works I came across the "famous" formula for net-thrust: https://en.wikipedia.org/wiki/Turbojet#Net_thrust $F_{thrust} = Q_{out} \cdot v_{out} - Q_{in}\...
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313 views

Why do some Turbofan engines have multi-stage fans?

I was wondering why some turbofan engine have multi-stage fans. e.g. F-119 engine: F100 Saturn AL-31
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Are large jet turbofans so easy to spin?

In this question, in the accepted answer, there is a comment by alephzero that says one can actually rotate a large turbofan's blades with one finger! Is that true, ...
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Factors to be considered when re-engining aircraft

What parts of the aircraft need to be adjusted / refitted / added when fitting new (different type) of engines? Also what what kind of re-certification regarding airworthiness etc. will be necessary?
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Can you identify this engine?

I am studying Aircraft mechanics currently, and in our academy we have some aircraft engines and different types of them, and I need please your help to know the reference of one of them, and if it is ...
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What is the diameter of each stage of the PW800 engine compressor and turbine?

I am an Aerospace Engineering student working to analyze P&WC's PW800 engine family--specifically, the PW814GA, for a project and we need to know some hard-to-find data. Does anyone knows where I ...
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What is the meaning of “Maximum Radial Projection (at Drain Mast)”?

I am an Aerospace Engineering student working to analyze P&WC's PW800 engine family--specifically, the PW814GA, for a project and I am stuck by a term: "Maximum Radial Projection (at drain ...
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37 views

Why is tangential velocity a loss of kinetic energy in a turbine section?

While researching turbine engines I came across a statement The mass of airflow naturally does not change in the transfer of energy to the rotor system, but the velocity of mass flow being slowed ...
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Why don't turbofan engines have shrouds affixed to the fan blades?

For a turbofan to be efficient the gap between the blades and the shroud has to be extremely small. Why don't we just attach the shroud directly to the blades and let it spin as one? Would that ...
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What valve would be the best for a model rocket with a hybrid engine? [closed]

I am planning on building a model rocket with a hybrid engine. I am trying to find the best valve that could be used for the MOV, main oxygen valve. I plan to use gaseous oxygen and would like the ...
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What causes air to move to combustor?

I know the pressure is highest at end of compressor. But what forces air to move low to higher pressure? Am i missing out something? I have heard seals are used to prevent leakage of air from ...
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What is the purpose of a movable inlet on a jet engine?

I was reading that aircraft like the F15 and SR-71 have movable inelts. Whats the purpose of this? I was also reading aircraft like the F-22 doesn't have a movable inlet. Why?
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Which dust size causes most damage to turbine engines?

I'm conducting some research on my bachelor's thesis on predictive maintenance and I have so far not been able to find a solution to the following question: Which size of dust is more damaging to the ...
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What is the engine shell temperature?

What are the highest temperature locations in the outer shell on an aircraft engine? Particularly, modern turbofans like the Trent 900 for example. I'm interested in the temperature constraints of ...
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249 views

If Sweden wants to export JAS39 to a 3rd country, will they have to get permission from the US govt.?

Does Sweden manufacture its own jet engine for JAS Gripen, or does it purchase engines from the USA? JAS39 C/D uses Volvo RM12 JAS39 E/F uses Volvo RM16 I read on the internet that Gripen's engine ...
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What are the differences between turbojet and turbofan (low and high by-pass ratio) in the graph of thrust relative to speed?

What are the curves of thrust relative to velocity of the turbojet, low-bypass turbofan and high-bypass turbofan engines from static thrust to Mach 4 generally. Approximation is okay as long it has ...
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What are different components of an engine pylon?

What are the different structural components that are inside the fairing of engine pylon and what are the functions of each part? The pylons for each aircraft are made of Ti-64 alloys, can they be ...
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1answer
134 views

What is the temperature range of engine mounts connected to the pylon?

I want to know what is the temperature of the engine mounts in modern turbofan engines for example, Rolls Royce Trent 900. Also, what are the temperature considerations you need to make while ...
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What is the ground idle fuel flow of an A320 (CFM or IAE or neo)?

Standing on ground, what is the idle fuel flow of an A320? ISA conditions, both engines running?
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How hot is the outer casing of a turbofan engine?

I am able to find temperatures inside different components of turbofan engines, but I can't seem to find what would be the temperature of the external casing/shell of the engine. For example, ...
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Is it feasible to replace a C152's engine with multiple small turbine engines?

If I wanted to remove the piston engine from a cheap plane like a Cessna 152 and add small turbine engines with an equivalent thrust but weighing less, where would be the best place structurally to ...
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1answer
275 views

Why does turbofan exhaust appear to reverse direction?

Yesterday I was at the airport planespotting. I observed the exhaust of a couple of turbofan engines, and found it curious how the fluid seemed to behave as it was leaving the engine and gaining ...
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JFS vs APU (for fighter jets) [duplicate]

I know that many fighter jets such as the F16 and F22 use a JFS to get compressed air into the engine. However, I was also reading that an APU does this. Im very confused on what does what. Thank you.
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Why can such a small difference in thrust make such a big difference in maximum speed?

I was recently comparing two aircraft, and, although I feel stupid asking this question, I wondered why one had a maximum speed of M2.2 compared to M0.94, when both have similar weight, both are ...
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Is Chinese WS-13 jet engine in serial production?

The Guizhou WS-13 was being developed to power Chinese JF-17 and J-31 fighter jets. Is its development complete? Is it certified/finalized for serial production?
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What happens in an F-16 once the aircraft exeeds its service ceiling?

What exactly is the sequence of events that would unfold as an F-16 attempts to exceed its service ceiling? The scenario is simply full afterburner and attempting to simply climb higher and higher (at ...
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How to determine the number of copression stages given a compression ratio?

I have a personal project to design a gas turbine engine, the main problem that nags me is how do I determine the pressure rise in each stage of an axial compressor? Say, I'm planning on a 38:1 engine ...
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195 views

How can jet engines be more efficient than propellers? [duplicate]

If jet engines are smaller in diameter than propellers, is it fair to say that propellers accelerate a lot of air a little while a jet engine accelerates a little air a lot? Basically, a jet engine ...
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227 views

Why do the Comet's engines point outwards?

As it's visible from the images below, when looking at the plane from the top, the engines point outwards and they are banana-shaped, why is that? (unfortunately I couldn't find a real photo ...
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Why does the N1 on a FJ 44-2A turbofan go to 104.4%? [duplicate]

Whilst watching a video of a Beechcraft Premier A1 Jet whilst in the cruise at FL330 I noticed the N1 on both engines were at 104.4%. Can anyone explain why they can go over 100%?
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What is this class of bolts called?

They can be seen in many —mainly military— jet engines. Do these bolts recibe an special name? J79: the fasteners are everywhere EJ200: they can be discerned in the rear flange
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What is oil thermal expansion in the CFM LEAP 1A engine for the A320NEO?

While I was going through the FCOM's SOP, normal procedures chapter, preliminary cockpit preparation section I came across the term oil thermal expansion. In the image below it is mentioned in the ...
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Can tailwind produce reverse-thrust?

I know that the answer will probably be no, and this question might sound silly, but I wanted to think outside of the box. If engine air intake comes from the front, and is pushed out through the ...
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What are those tiny circles on fan blades of Trent 1000?

From Sam Chui's video, there are tiny circles on the surface of three fan blades of next generation Trent 1000 engine. Why aren't they present on remaining fan blades? Below comments suggest they are ...
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Why are inlet vanes used instead of variable geometry inlets to prevent compressor surge/stall?

Jet engine core axial compressors (that of subsonic turbofans anyway) are designed to keep air flowing the right way at max RPM(or close to it). Below that, the airflow slows more and more, and ...
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What was the average duration of a Me-262 combat mission during WWII?

Me 262 in 1945 Maximum speed: 900 km/h Range: 1,050 km Service ceiling: 11,450 m Rate of climb: 20 m/s at max weight of 7,130 kg Thrust/weight: 0.28 Could a Me-262 fight for (1050 km) / (900 km/...
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207 views

Does the jet blast from a large aircraft pose any risk for other aircraft nearby?

We know that the jet blast of jetliners - A320, B737 and bigger - are dangerous for people passing by, airport vehicles and even small planes, and we must always maintain a huge distance to avoid ...
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Is this plasma-thruster experiment actually measuring thrust? [closed]

This experiment, which is being presented as an initial exploration of the feasibility of using microwave-generated plasmas in a sort of electic jet engine, has been attracting some attention in the ...
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How does fuel economy quantitatively depend on altitude for a jet?

We already have a few questions and answers about the qualitative effects of altitude on fuel economy: How do I determine the best altitude to fly for fuel economy? Why does fuel consumption decrease ...
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What is the fuel/air ratio of the CFM56-5A1 engine (in the A320 model)?

I could find the fan-bypass ratio, which was 6:1 (on some models 5:1) but I was unable to find the fuel to air ratio used in this engine. For reference, it is a high-bypass turbofan engine.
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Why CFM International has changed the profile of the fan struts used at their CFM 56 turbofan?

See images below Image of a early version of a CFM56 turbofan showing the fan struts [![Image of a CFM56 7B26 showing the fan struts][3]][3] image description here]5]5ttps://i.stack.imgur.com/...
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Why is a centrifugal compressor in aircraft engine less susceptible to stall and surge?

I have came across a similar question here. Although the answer doesn't explain much about why and is somewhat vague. I have read that centrifugal compressor can achieve a higher pressure rise per ...
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Why does the P-3 Orion use an engine driven compressor instead of bleed air for pressurization?

In another question, an answer mentions that the P-3 Orion uses a gearbox driven compressor for cabin pressurization, even though the aircraft uses T-56 turbine engines that supply bleed air in other ...

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