80

Both engines use a turbine for power. This is where the "turbo" part of the name comes from. In a turbine engine, air is compressed and then fuel is ignited in this compressed air. The energy produced by the ignition turns the turbine. The turbine is then able to drive both the compressor at the front of the engine and also some useful load. In airplanes, it ...


66

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 and thicker aft of the trailing edge. This was done to stow the landing gear in them, but also to area-rule the aircraft. The Tu-95 applies knowledge that was ...


46

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 in the question, there are visible streams of condensed water vapor from the atmosphere. These streams are only present at the blade tips. The question seems ...


45

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 transported back to WWII, but you wouldn't have to as it would have been possible to make reasonable jet fuel. The Jet-A standard was made in the 50s, and there were ...


39

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/kW-h. But even supercharged truck diesels achieve above 40% thermal efficiency at high load (this NHTSA study gives 42%). Aerodiesels have achieved 220 g/kW-h ...


38

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 also powers the prop. In between the compressor and turbine, the fuel/air mixture is burnt without significant moving parts. Without the turbine and ...


37

The short answer to both your questions are Yes. The long answer is, it's not so simple. The ATR 72 you have pictured has a top speed of 276 knots and a range of 1,300 miles. It can carry around 70 passengers. This document provides detailed comparisons of burn rates. So we can see the ATR 72 burns about 810 Liters per hour (about 214 gallons/hr). A Boeing ...


36

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 on takeoff, the propellers move into a maximum power setting, the engine snarls and slows a bit under the increased workload.


34

Well, first let's clear up a few terms: When you say "rotary" engine I'm assuming you're referring to radial engines, a type of piston engine that used to be pretty common on aircraft. (These days opposed piston engines are what you typically find on piston-powered aircraft, rotary engines are yet another design, but their usage died out around the end of ...


32

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 possible. Inertia keeps solid matter low at the indicated point while air makes the turn into the engine. C130 Nacelle


32

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 angle is directly controlled by the power levers, and the propeller RPM is controlled by an Np governor in the fuel controller modifying gas generator (the engine ...


31

Hotel mode is a feature on ATR 42/72 turboprops replacing an APU by locking the right-hand #2 engine (PW100) with a 'propeller brake' while allowing the turbine, and therefore also the generator, to run, providing electrical power and bleed air. ATR describes this as the following: The propeller brake is fitted on a countershaft on the RH engine ...


31

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 thrust is inverse to speed. This helps for acceleration at take-off, but limits maximum speed. A modern piston engine uses 240 g of fuel for providing 1 kW of ...


29

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 directly but a turboprop engine requires the addition of a propeller, which may have differing characteristics based on the installation. Since thrust is not known ...


28

For short distances, turboprops are more fuel efficient than jets. On the longer flights, the jet (turbofan) engines win the race. Turbofan engines perform best at high altitudes. At medium and low altitudes, the turboprops are more efficient engines. Since all flights start and end at low altitudes, the high altitude cruise segment needs to be long enough ...


27

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 supersonic flow. Since the tip will be the part with the highest speed, and propellers have bigger diameters than fans, propellers run at lower speeds. The high ...


25

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 are more likely to make longer, higher-altitude journeys. Where jets are more fuel efficient. They are more likely to operate between airports with concrete ...


24

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 completed, and the next projects, soon to be called TA9 and TA11 (TA for Twin Aisle; they would eventually mature into the A330 and A340), were still far, far ...


23

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. This is done when the engine is shut down and the propeller should create minimal drag. This means also that all accessories on this engine will not be powered ...


23

Not enough thrust (i.e., too many engines) Taking the lightest wide-body, the Airbus A310-200, its MTOW (max takeoff weight) of 144-164 tonnes is >2 times that of a Boeing 737NG at 65-85 tonnes. A 737 equivalent in MTOW in the prop world is the C-130 at 70 tonnes, and it needs 4 propellers. So we are looking at 8 propellers for an A310-sized wide-body, or ...


23

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 turbo prop the engine produces power which, via a gear box spins a propeller that generates the thrust. Since most turbo props have the ability to adjust the ...


22

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 either glide farther or have better performance on the remaining engine(s), you can set the prop pitch lever so instead of facing at a right angle to drive air ...


22

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. An example of a gas turbine used in helicopter, airplane, train, and even snowplow is the well-known Pratt & Whitney PT6. It has different versions. The two ...


22

(wikimedia.org) British Aerospace Jetstream You're right, it's the wing placement. For low-wing aircraft you find inlets above the prop, and sometimes circular inlets around the prop. The same engine shown above has different inlets depending on the plane, where you'd find an under-prop inlet in high-wing aircraft. (norebbo.com) But having the inlet above ...


22

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, and a propelling nozzle. Air is drawn into the intake and compressed by the compressor. Many turbo props have a gear box (as shown in the image above, the ...


21

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 to your idea, albeit the unducted fan is not exactly a propeller. Safran has restarted researching on this design, end of 2017, for an operational use after 2030....


20

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-rotating propellers each cancelling out the opposite's torque. Also you increase the speed of air accelerated by the propellers, thus the aircraft’s efficiency ...


20

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. When standing laterally, the propeller tips would move towards and away from you and produce a variation of noise intensity of the frequency produced by the ...


20

No. The wing does a great job in straightening the propeller swirl, but adds its own vortex. Wake turbulence is dominated by the flow field around the wing.


19

First, piston engines are more efficient than turboprops, so their operational cost are lower. This also means that the system mass (engine plus fuel) for a trip is lower once you go beyond small ranges. In a helicopter, the engine mass is more important, because average flight times are much shorter, so you find many helicopters with turbo engines and only ...


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