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59 votes

Would it be viable to install a screen in front of jet intakes to prevent them from sucking in birds?

Modern high-bypass turbofan engines work by pulling in immense volumes of air and accelerating it. A screen as proposed would make that task far more difficult, which would ruin the efficiency of the ...
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38 votes

Do turbine engines on multi-engine aircraft rotate in opposite directions to offset torque?

Torque is less of a problem due to the effective roll damping of a wing, but gyro effects and prop wash are important. Gyro effects first became an issue with rotary engines in WW I. A rotary engine ...
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33 votes

Can you identify this jet turbine stage?

What is this turbine part? This assembly is part of the turbine used to rotate the compressor section of a Pratt & Whitney PT6, a free turbine turboprop. It's known as compressor turbine or just ...
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26 votes
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Why are turbine blades not made out of titanium, only compressor blades?

Titanium is unsuitable because it will react with oxygen and carbon at high temperature, well below its melting point, making it very hard and brittle. Welding titanium is very complicated because it ...
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26 votes

Has anyone burned hydrogen in a gas turbine?

Yes, indeed the plan to build a hydrogen-powered jet laid the groundwork for using hydrogen in the Centaur rockets and the upper stages of the Saturn 5. While hydrogen was used only experimentally in ...
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25 votes

Why are aircraft turbine blades made of nickel alloys?

Not all turbine blades are made of nickel alloy, some blades are made of such family of alloys but clearly not all. Some blades are actually made of ceramic materials. The turbine is always located ...
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24 votes
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Why do large turbofans generally have many more LP turbine stages than HP turbine stages?

Because the LP turbine extracts power for the fan, which requires the most power. The HP and IP turbine only extract power for their connected compressors - the LP turbine extracts power for the fan ...
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24 votes
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What does the small needle + scale on this turboprop's N1 gauges indicate?

It duplicates the percent graduations in the large dial but at a finer resolution, with one percent increments. It's just to make the individual percent graduations easier to discern at a glance ...
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23 votes
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Is starting a jet engine without ground support possible?

Modern jet transport category aircraft have APUs and they will be running if no engines are. Batteries on jets do not work very long with all electrical buses energized and the first thing you do ...
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22 votes
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Is it possible to drive a prop directly from a jet engine without a gearbox?

As a side comment, there is a type of engine researched in the 80's/90's, but never marketed, where an unducted fan is driven directly by the turbine shaft without a gearbox: The propfan. It's close ...
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22 votes
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What are these engine inlet devices used for?

The first photo shows the engine air intake screen. Its basically a screen to prevent FOD ingestion, as you noted. From CH-47 Theory of Operations: Engine Inlet Screens An engine inlet screen which ...
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22 votes
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Is the compressor required on jet engines? Can air be rammed into the turbine?

Your questions At what point (if any) does air stop getting sucked into the turbine and is just getting rammed in? On a CFM56-7B engine (Boeing 737 NG) pressure is provided by the fan, the low ...
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19 votes
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Compressor-Turbine: Why a shaft and not kind of a "rotating drum"?

There are a few very practical reasons why turbine engines use inner shafts/spools. First, jet engine spools are very high speed rotating parts, this means they are subjected to high amounts of ...
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18 votes

Would it be viable to install a screen in front of jet intakes to prevent them from sucking in birds?

A few Russian/Soviet fighters had retractable FOD screens on their engine intakes (MiG-29 and Su-27 IIRC). The assumption was that they would operate from damaged runways or roads and the engines ...
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18 votes

Would it be viable to install a screen in front of jet intakes to prevent them from sucking in birds?

Screens were actually used on the first prototypes of the Me-262, but soon abandoned when they were found to be more of a burden than a help. If you look carefully at the picture of the Me-262 V3 ...
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18 votes

Has anyone burned hydrogen in a gas turbine?

For fuels intended for use in aircraft, the key performance parameter is the energy density of the fuel: how much potential work is stored in how many liters of stuff. High energy density means the ...
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18 votes

Would it be possible to put wind turbines alongside runways that are driven by the exhaust of planes?

No, there's no practical benefit to putting wind turbines alongside runways and plenty of drawbacks. Airplane engines and propellers direct their thrust straight back, so the only logical place to put ...
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  • 49.6k
16 votes

Would it be viable to install a screen in front of jet intakes to prevent them from sucking in birds?

There are three problems with this idea: (1) To make a screen strong enough to withstand the body of a 15-to-20 pound bird hitting it at 500 miles per hour, would require thick wire which would ...
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16 votes

How hot do internal parts of jet engine get?

This parameter is called Turbine Inlet Temperature (TIT) Turbine Inlet Temperature (TIT) is the temperature of the combustion chamber exhaust gases as they enter the turbine unit. The gas ...
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16 votes

Are there Hybrid Electric-Combustion Turbine Engines where only the compressor is electric driven?

I don't know if such an engine exists, but I can assure you that it wouldn't be a good idea. The reason is that you would be introducing multiple additional failure modes, each of which would result ...
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16 votes
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How exactly is the free shaft part of a gas turbines controlled?

The free turbine is literally just a windmill that generates torque when the wind blows on it. You could actually just stick it outside the engine itself behind the tailpipe and it would do the job, ...
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  • 105k
15 votes

For an electric airplane are propellers the only option for propulsion?

Propellers in some form are really the only option. It is currently the only efficient way to generate thrust with air as a medium. Even jet engines are in some sense just a very elaborate system of ...
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15 votes
Accepted

is boundary-layer jet-turbine a scam?

In short, they are both scams that fall heavily into the category of Not Even Wrong or cargo cult science.Tesla's work is sadly a great favourite of conspiracy theorists who do not have the technical ...
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15 votes

What does the small needle + scale on this turboprop's N1 gauges indicate?

If the engine is at 95% RPM, the large needle will point halfway between the "90" and the "100" indication on the outer scale, and the needle on the small dial will point to the &...
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  • 41.9k
14 votes

Why are aircraft turbine blades made of nickel alloys?

Their main advantage is higher strength at elevated temperatures. With elevated I mean temperatures up to 1200°C, which is what you will find in modern, film-cooled high-performance turbines where the ...
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14 votes

What are the indications that your turbofan engine has "thrown a blade?"

engineer and pilot here - formerly of JPL. I've seen blade loss tests and any modern high performance engine will violently destroy itself if a blade is lost. You can see tests of this on youtube for ...
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14 votes

Why can't we extract more from exhaust gases in gas turbines?

It can be done, but the better specific fuel consumption does not compensate for the extra weight. We all know that aero engines have to be as light as possible. In land, stationary installations, ...
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  • 10.4k
14 votes

Are there Hybrid Electric-Combustion Turbine Engines where only the compressor is electric driven?

No, such engines do not exist, as is implied in the question already: I can't tell if this idea is good or simply bad, nor I could find any examples of such engine. Pic above is an own photo, used ...
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13 votes
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What are the indications that your turbofan engine has "thrown a blade?"

Turbofan engines are designed and tested to contain a fan blade failure. However, this is a violent event and will cause serious damage to the engine. The engine and surrounding components are ...
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  • 69.7k
13 votes
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What is a "high-bypass geared turbofan," and why is it so much more efficient?

The fan section of a turbofan engine is driven by the low pressure (LP) spool. This means that it is connected to two parts of the engine: The LP compressor, which must compress the air before it ...
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