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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Can someone explain how the FUEL MANIFOLD PRE FILL LOGIC system works on the CFM LEAP 1A engines for the A320NEO?

While reading through one of my companies operations notice regarding the LEAP 1A engine I came across this term. But my company hasn't been able to explain how this system works. Could someone help ...
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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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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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106 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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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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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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why are the Comet's engines pointing 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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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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130 views

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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Why this formula says jet engine is efficient at any speed?

Wikipedia gives the following equation for the efficiency of the jet engine, here: $$\eta_p = \frac{2}{1 + \frac{v_e}{v}}$$ Where V is the aircraft speed and Ve is the exhaust speed. It is backed by ...
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How much the Concorde secondary nozzle contribute to thrust?

Does anybody knows how much did secondary nozzles bucket type on the Concorde's engines contributed to the increase of thrust during take of and sub-sonic flight? This is picture of the nozzles and ...
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How do HPTACC and LPTACC work?

How do High Pressure Turbine Active Clearance Control (HPTACC) and Low Pressure Turbine Active Clearance Control (LPTACC) work? What are the consequences caused by the malfunction of these components?...
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What does “5B3/P” in CFM56-5B3/P mean?

For the CFM56 engine model CFM56-5B3/P, what does "5B3/P" mean?
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What are these small engine inlets on the Super Hornet?

Does anyone know what these two small variable inlets on top of the engines are used for on the Super Hornet? Source: navy.mil; cropped
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Why are engines angled toward the fuselage?

Source: twitter.com I saw a picture of a 777 from overhead and I was wondering why the engines point "in" to the fuselage, rather than being parallel to the fuselage.
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What advantage does Kawasaki C-2 have with a twin-engine configuration as compared to its competitors like An-70 or A-400?

While reading about various military transports, I came across the specs of Kawasaki C-2 and a few questions popped up. So please bear with me here if I list them all together as points, I hope ...
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What is a compressor cascade?

Is a compressor cascade just the representation of the blade ring of an actual turbomachine? What is the difference between linear cascade and annular cascade? A diagram or a reference would be great.
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How is fuel ignited in jet engines? [duplicate]

From what I understand, in jet engines, air is compressed and fuel is not only injected but also ignited : how is this done ?
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Is a fuel that reacts with another to form hydrogen for fueling aircraft possible? [closed]

Hydrogen is the most abundant element in the universe and has great properties when reacting with oxygen for use as a fuel. Yet here on Earth, its production is prohibitively expensive, its storage ...
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Why does the 737NG EGT drop during take-off?

I noticed that the EGT drops a bit when I hit TO/GA for take-off on a 737-800.
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Why does each fan blade have a different mass and frequency?

From a documentary (at 16:39) on building a Rolls-Royce jet engine: ... no two finished blades are exactly alike, and with twenty in each fan, it will only spin smoothly if the blades are perfectly ...
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How do turbofan internals handle the load from the thrust?

To my understanding, turbofan engines get the majority of their thrust from the fan in front of the engine, up to around 70-80% while the core flow generates around 20-30%. Forward movement is ...
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Can you fly 2000 miles on an engine that costs less than $500k? If so, what type of engine?

Ok so Im exploring ways to bring cargo and medical supplies to various rural cities in say Africa without relying on ground infrastructure. Just short and cheap runways spread around the continent. It ...
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Jet Engine Cooling, HTC and cooling calculations

Right now I am working on a project about cooling systems in jet engines. And I don't have a supervisor to ask anything. I would like to know what is the most useful resource (book, analsys programs ...
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Can Flex thrust be lower than climb thrust?

Let's restrict this question to airliners with 2 jet engines. For the remaining of the question, I'll use the term flex to designate reduced take off thrust as I'm more familiar with airbus's systems....
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GE90-115b turbine horsepower

The GE90-115b is rated at 513 kN maximum thrust and is often said to have 110,000 shaft horsepower, but I have yet to find any document or specification that backs the claim on horsepower figure. A ...
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Turbofan engine start - Why does ignition occur so early?

In another thread, two key steps of starting a turbofan (ignition and fuel introduction) are given as follows: With increased N2 rotation, ignition will be turned on. [...] With further ...

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