72 votes

Why is the Tu-95 so efficient despite having propellers that spin faster than the speed of sound?

Yes, propellers have problems at high speed, but if done right, they still have an advantage over turbofans at speeds up to Mach 0.8. Look at the inner engine gondolas of the Tu-95: They are elongated ...
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47 votes

Can these vortices be dangerous?

While @Peter Kämpf 's answer is great and sufficient to answer the question, I would like to add a clarification (which should be a posted as a comment, but is too long for this format). In the image ...
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  • 67.9k
46 votes
Accepted

Would jet fuel for an F-16 or F-35 be producible during WW2?

Jet fuel is mostly kerosene, with some aromatic hydrocarbons mixed in for stability, temperature range and the like. You could probably run military jets on pure kerosene if they were magically ...
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  • 50.3k
41 votes

How does gas turbine efficiency compare with supercharged piston engines?

The most efficient IC engines are large Diesels. At the extreme end are ship engines with better than 50% thermal efficiency resulting in a specific fuel consumption of only 0.260 lbs/hp/hour or 158 g/...
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40 votes
Accepted

Why do aircraft with turboprop engine have black painted anti-icing system?

These are rubber boot deicing systems. When ice forms on the leading edge of a wing, pressurized air is used to inflate the boot so the ice will pop off. Normally, this inflation is not permanent but ...
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38 votes

Is a turbocharged piston aircraft the same thing as turboprop?

They are both internal combustion engines that have a turbine in their exhaust that is used to power a compressor to pressurize the air before it is used for combustion. In the turboprop, the turbine ...
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  • 763
37 votes
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Why would a turboprop rev down just before going full throttle during takeoff?

Because the pilot is taxiing the airplane with the props in the beta range (turboprops turn into landsharks if you don’t do this and you end up really riding the brakes to keep the speed down), then ...
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35 votes
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Why do we refer to "power" for turboprop engines and "thrust" for turbojet/fan engines?

Ultimately what you want from all three types of engines is quantification of thrust available to push an airplane through the sky. The turbofan/jet engines are self contained and produce thrust ...
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  • 16.8k
34 votes

Why are turboprop intakes placed below the propeller?

Inertial separators are augmented by gravity when located under the engine. It is easier to discharge ingested ice and debris downward, rather than some other direction, so that is where they go if ...
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  • 16.8k
33 votes

Why are propeller engines uncommon on airliners?

Reading the answers here tells me to put a few facts into the discussion: Piston engines are the most fuel efficient aviation engines. Their drawback is a constant power output over speed, so that ...
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32 votes

Why would a turboprop rev down just before going full throttle during takeoff?

It's because he was taxiing in DISC (discing, or flat pitch making the prop like a big disc), which is in the ground beta range, then coming out of it. Beta range is a mode where propeller blade ...
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  • 108k
30 votes
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Why are propellers de-iced before the engines are started, and does ice on the fuselage affect the flight characteristics of the plane?

The props are done before starting because you need to make sure the blades and spinners are fully cleaned off while they are stationary. Otherwise, they'd vibrate like hell when starting and shed ...
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  • 108k
28 votes
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Given the same engine, why install a gearbox on a turboprop but not on a turbofan?

The bigger the diameter, the lower the optimum speed. Generally, fan and propeller blades should run at a high dynamic pressure, but still at subsonic speeds to avoid the higher losses involved with ...
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26 votes

What does feathering mean and how does it work technically?

Feathering is only possible with variable pitch propellers and means that the blades are turned such that their mid-to-outer section is aligned with airflow and they create minimal air resistance. ...
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26 votes
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Why does an aircraft as big as the Airbus A400M use turboprops?

This answer needs some background information. What became the A400M started as the Future Large Aircraft or FLA in 1983. Airbus was worried what to do with their engineers after work on the A320 was ...
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26 votes
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Why do propellors have white markings on their tips?

It is so you will see a circle when they are turning. Without contrasting bright tips turning propellers are invisible, and pose a grave risk for someone who is deaf, wearing heavy hearing protection,...
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  • 16.5k
25 votes
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What does feathering mean and how does it work technically?

Feathering is not engine starting, and also is not used in turbine (excluding turboprop) aircraft. In a piston or turbo prop aircraft, in the event of an engine failure, to decrease drag so you can ...
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  • 2,096
25 votes

Why does an aircraft as big as the Airbus A400M use turboprops?

Both aircraft seem to have the same purpose Not entirely. The RAF see the C17 as a strategic airlifter, the A400 is seen as a tactical airlifter replacing the turboprop C130. Strategic airlifters ...
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24 votes
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What are the differences between a helicopter engine (turboshaft) and an aircraft engine (turboprop)?

There are no major differences between a turboprop used on an airplane and a turboshaft used on an helicopter. All power is collected by the turbine shaft which rotates the blades through a gearbox. ...
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  • 67.9k
24 votes

Why do we refer to "power" for turboprop engines and "thrust" for turbojet/fan engines?

Jet engines directly produce thrust by exhausting gas (and in a modern turbo fan also moving a lot of air around them), so fuel flow rate is directly related to the thrust that is generated. In a ...
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  • 96.3k
24 votes
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Why have propeller engines never been mounted on the tail in production transport aircraft?

There are two really big issues with tail mounted powerplants with propellers; weight distribution and Foreign Object Damage. Tail mounted engines move the empty C of G aft. This forces you to put ...
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  • 108k
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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  • 108k
22 votes
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Did the XF-84H Thunderscreech really cause "900 sonic booms per minute"?

I think it is a matter of where you stand (literally). From the front or the rear the shock waves from the propeller tips would hit your ears continuously, and the result would be constant noise. ...
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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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  • 67.9k
22 votes

Is a turbocharged piston aircraft the same thing as turboprop?

No, a turboprop is more like a jet engine with a propeller in the front instead of a fan: Source: Wikimedia In its simplest form a turboprop consists of an intake, compressor, combustor, turbine, ...
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  • 35.2k
22 votes

How are turboprops and other propeller planes pressurized?

Turboprops are actually turbine engines. They can produce bleed air just like turbine engines (e.g. turbofan). The bleed air can be used directly to pressurize the cabin, or it can drive another turbo ...
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  • 10.7k
21 votes
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What is the purpose of having contra-rotating props on an aircraft?

According to my experience, you have two problems with props: Torque Exhaust Speed If you use contra-rotating propellers, you eliminate the torque reaction problem because you now have two contra-...
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