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Questions tagged [propeller]

Aircraft propellers are airfoils which convert rotary motion from a piston or turbine engine into thrust suitable for propelling an aircraft.

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Is there any equation to bind velocity, thrust and power?

I am designing a remote controlled airship. I will tune it so that the lift given by Archimedes' Principle will exactly balance the weight of all the structure. It will be propelled by brushless ...
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What is the propeller efficiency, $μ_p$, of modern propellers for light sport aircraft?

Roskam's book on preliminary design gives a value of 0.7 for "homebuilt" aircraft and 0.8 for general aviation. What explains this difference in propeller efficiency? The content of Roskam's book is ...
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Why are push-propellers so rare, yet they are still around?

Jet engines are by their very nature push-engines, however, most propeller airplanes use pull-engines. Is there an inherent advantage to using pull-propellers except for the increased airflow over the ...
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What are the advantages of more than 4 propeller blades?

I have heard that propellers with more than four blades are not as efficient as 4 or less blades because of lower thrust which may result from interfering prop-streams. But I see the ATR-42/72 and ...
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Would connecting propeller blades with a continuous ring reduce induced drag?

Turbine engines are covered, which of course is to contain the process (just like a super/turbocharged engine is as soon as the air enters the intake). But it got me thinking, doesn't this also reduce ...
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Why don't aeroplanes use propellers with more blades like the intake on a fanjet?

The air intake on a fanjet typically has many small angled blades. A wind pump in an American film might have many broad slatted blades. My desk fan has 3 very large scooping blades and seems quite ...
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How does a Constant Speed Propeller work?

My explanation of how a constant speed propeller works has always been a little shaky. I know about the "speeder spring," "counter-weights," and how it utilizes the engine oil pressure, but I'd love ...
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5answers
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How does a fan differ from a propeller?

Why is the fan in a turbofan different than a propeller in a small airplane? Why do propellers typically have 2 or 3 blades, but the fan has a lot more? And why is the fan shrouded but the propeller ...
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1answer
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How high can propeller airplanes fly?

Is there a maximum height a propeller airplane could fly? Some lower bounds for maximum flying altitude: 12,000m (39,370ft): Antonow An-70, produced 1994 12,310m (40,387ft): Lockheed Martin C-130J ...
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Why do turbofan blade tips exceed the speed of sound while prop tips should not?

It seems that the tips of the fan of a turbofan engine can and do break the sound barrier: The GE-90 has a fan diameter of 3124 mm and a rotational speed of 3475 RPM. Their circumferential velocity ...
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2answers
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Are ducted fans more efficient?

As far as static thrust, does a shrouded/ducted propeller outperform an un-shrouded propeller? It seems that the guide blades on the bottom of the duct would allow little more thrust to be extracted ...
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How do propeller-driven, fixed-wing UAVs counter negative torque from engine rotation?

What cancels the rolling moment produced from the rotation of the engine?
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What is the purpose of having contra-rotating props on an aircraft?

Why do planes, like the famous XF-11 and the Tu-95, have contra-rotating props? What is their purpose? Image credit: Mike Freer / Touchdown-Aviation / Wikimedia
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Why does flight training usually start with (unsafe?) propeller planes and not with (safer?) jets?

I live in the UK and would like to learn flying jets, but most courses seem to start with propeller planes. Not sure if this might be a misconception about the safety of different aircraft types, but ...
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Can propeller driven aircraft sustain speeds at or above Mach 1?

Has any propeller driven aircraft ever achieved and sustained supersonic speed? If not, why can't propeller airplanes achieve that speed?
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Do ducted fans eliminate induced drag?

It has often been said on this site that induced drag on wings is the inevitable result of producing lift over a finite length. Converting this to the realm of propulsion, I assume that propellers ...
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2answers
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Why are there so many different propeller shapes?

While doing an image search, I found these images of propellers: and Some appear to be straight-ish on the leading edge and curved on the trailing, some curved on the leading edge and straght-ish on ...
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How do the blades on a propeller generate thrust?

I am having trouble understanding how this type of propeller generates thrust: It is so much different than a propeller on a Cessna and thrust would be provided differently. I am also confused of how ...
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Why don't planes have a reverse propeller as air brakes?

When I first heard the word air brakes it came to me that maybe the engine start rotating in the opposite direction for that, but since that's not possible, why can't we have an extra engine for air ...
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Why does the spiraling slipstream from a propeller hit the left side of the fin?

In the picture below, if the fuselage was shorter/longer, would the spiraling slipstream from a propeller hit the fin on the right side as opposed to the left? Is it a deliberate positioning if yes, ...
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1answer
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Is there an equation which allow us to perfectly match a helix propeller and an engine?

Is there an equation which allow us to perfectly match a helix propeller and an engine? I'm looking for an equation that allow me to correctly dimension an helix propeller for my engine. I mean that ...
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What are the factors considered while placing a propeller on a plane? [duplicate]

I have read the post where it describes about the push and pull configurations of the engine, advantages/dis-advantages in them but not the purpose. I have seen images of a figter where the ...
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Why are the top speeds for jet engines higher than for propellers?

I realize turbines are more efficient than piston engines, but if that were true, then why don't turbo-props reach jet speeds?
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How does blade solidity ratio relate to thrust/power/torque of a propeller?

for quite some time I was using ABBOTT formula for static thrust estimation on a two-bladed propellers: $$ T=6.8\times10^{-5}\times D^{3}\times p\times RPM^{2} $$ $T$ is Static Thrust (N); $D$ is ...
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How does the relative wind on a propeller, strike the blade from behind (the non camber side)?

This may be a stupid or simple question, although any help is appreciated! :) If possible, please answer without mathematical terminology. So I understand the concept of the blade increasing air ...
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Why don't helicopter blades look like other propellers?

While doing an image search, I found many different shaped propellers and asked about them in this question. In it, Peter Kampf answered my question with his usual thoroughness. However, as I looked ...
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Why is max endurance different for jet and props?

Max endurance speed is not the same for gliders, propeller planes (also for turbo prop, right?) and jet planes. While for for jet planes max endurance is at the minimum drag speed ($V_{md}$), for ...
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8answers
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Can a plane fly backward if its propeller is in reverse?

I would like to know if a prop plane, for example the P-51, could be able to fly backward. Is it possible through some trick like changing blade angle or reverse the prob rotation direction? It would ...
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What are the advantages of the NASA LEAPTech propeller on wing technology?

NASA has detailed experiments with a new type of parallel array of small electric propellers on the leading edge of the wing technology that they are calling LEAPTech. The press release notes that ...
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6answers
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Why are propeller airplanes still made?

Airplanes with propellers were invented a long time ago. After that, jet engines came into existence. My question is: why do we still have propeller engines? The reasons I can think of are: They are ...
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2answers
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How to design a propeller for UAV?

I need some advice on designing a propeller for a UAV and choosing the right motor for it. I am doing a project which requires the fix-wing UAV to travel at cruise speed of 20 m/s and weighs a total ...
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What are the pros and cons of scimitar propellers?

I know scimitar propellers are used to reduce noise, but what is their downside? There has to be one, considering most propellers don't use that shape.
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For an electric airplane are propellers the only option for propulsion?

This is for an electric airplane (so no fuels for combustion): Are propellers the only option? Is there a turbine-jet possible with only air intake, electrically compress, and a turbine and nozzle ...
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What are the differences in aircraft performance between tractor and pusher propeller designs?

Some aircraft have pusher type propellers. In what ways is it different from a tractor type propeller? What's are the advantages and disadvantages over a tractor type.
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Is it possible to get a list of Cl/Cd values for various NACA Airfoils?

There are a lot of links which give the shape of the airfoil for any given set of camber thickness, position and max. thickness values, but I would like to know if it is possible to get the Lift vs. ...
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How can an airplane fly with single propeller without rolling over? [duplicate]

I have no knowledge about aviation or mechanics or something. Recently I started a computer game 'besiege', a kind of sandbox-like game with bunch of parts to make all kinds of machinery. And I'm ...
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Why do ground crews rotate a radial engine's propeller before a motor/cartridge start?

In footage from WWII you often see the ground crew rotating the propeller of a radial engine a number of times before the pilots start the engine. I know it's not the same as hand-starting (hand-...
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1answer
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Can I model propellers used in electric aircraft the same way as I model RC quadcopter drones?

I am writing an article about mathematically modelling a flying car, using D'Alembert's principle. I need some information about the propellers ... When I worked with the mathematical model of a small ...
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How do Throttle control and Propeller control work together?

I haven't been able to understand. If propeller control controls the pitch of the blades in a constant speed engine, what do the throttle control do? I've seen (in some normal operation manuals for ...
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1answer
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How much thrust is gained from placing a propeller in a duct?

Assuming that the power and diameter are the same, how much extra thrust can be gained by placing a propeller in a duct? How does it influence the RPM? To clarify: take any prop, place it in a well-...
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3answers
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In a constant speed propeller, why does the RPM drop with a prop pitch increase?

When a constant speed propeller changes its pitch from low to high, RPM would decrease. Why is that the case? Wouldn't the RPM increase when we increase the blade angle since there's less drag and ...
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How is mass flow rate computed?

I have been wondering how the mass flow rate is determined by the area of the engine air intake surface and the incoming speed of the air. In still air, it is understandable that a stationary engine ...
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6answers
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Why do most single propellers have a clockwise rotation?

Why do most single propellers have a clockwise rotation (seen from the pilot's point of view)? There are though multi-engine planes that have each propeller rotating different directions, but in the ...
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2answers
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Why do propellers on aircraft have a slight offset angle?

Single-engine aircraft (one propeller on the 'nose') Why do propellers on aircraft have a slight offset angle? I have picked up this information that the rotational axis of the propeller is not ...
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3answers
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What were the disadvantages of early prop driven blended-wing aircraft?

I've been researching the history of pre-jet aircraft and I've come across several famous, and not so famous, blended-wing aircraft. The idea seemed to show promise but never really caught on, even ...
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2answers
478 views

Are there any ducted propeller or fans without a shaft in the centre?

Are there any propeller or fan designs that hold the propeller or fan in the duct and do not have a boss or propeller shaft? This could reduce the drag of the centre. Are there any other advantages?
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Can lift be equated to how much air is moved?

The explanation for lift that I find easiest to visualize is that air is deflected downward by the wing. This downward action causes an equal and opposite reaction of an upward force against the plane,...
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1answer
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Is there a mathematical formula to find the most efficient propeller? [duplicate]

Is there a mathematical formula to find the most efficient propeller? Is a five-blade better than a four-blade? Does software exist to aid in the calculations there?
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What is P-Factor in Propeller Aerodynamics? [duplicate]

What is the P-Factor when we're talking about a Propeller Aerodynamics ? Thanks
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Why are there different number of propeller blades on the inboard and outboard engines?

The Junkers G 38 has four propeller blades on the inboard but only two on the outboard engines. What's the reason for this special arrangement and is there any benefit?