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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27
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1answer
14k views

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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4answers
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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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12answers
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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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2answers
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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 ...
19
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1answer
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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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10answers
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Can an ultralight aircraft fly with a 18hp engine?

I have some questions - I'm planning on building single seat UL aircraft with this plan sketch (I have more), I drew this based on real plain and some research. Empty weight is between 50-70kg with ...
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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 ...
19
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3answers
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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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5answers
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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 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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4answers
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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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3answers
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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 ...
21
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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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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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2answers
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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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3answers
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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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8answers
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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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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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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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12answers
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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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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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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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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 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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7answers
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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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1answer
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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
558 views

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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788 views

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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3answers
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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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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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4answers
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Why did WWII prop aircraft have colored prop tips?

Why do propeller aircraft from World War II and similar planes sometimes have the tips of the props colored? I see it on single engine planes like the P-51 as well as bigger, multi-engine planes such ...
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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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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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2answers
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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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3answers
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What is a biplane propeller and how efficient is it?

Lazair ultralight series II used biplane props to absorb more power from the engine....so my question is what really is a biplane propeller and are they efficient in comparison to a four bladed prop?
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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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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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2answers
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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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6answers
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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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2answers
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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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1answer
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How to calculate variable pitch propeller parameters?

I'm carrying out a project on Variable Pitch Propellers for UAVs and especially self-adjusting or Passive Variable Pitch Propellers that change pitch due to aerodynamic forces and Pitching Moments. ...
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2answers
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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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2answers
149 views

How does one choose the number of blades and the diameter required for a turboprop propeller?

I am interested in the preliminary design of a regional aircraft that uses turboprops as the propulsion method. Following considerable research online about propeller design (disk theory, BEM...) I am ...
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2answers
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What do I need to know to design contra rotating propellers for a powered paraglider?

I wonder if anyone has any technical information that would assist in using the correct Size & Pitch Contra rotating Propellers (CRP) on this Foot launched Powered Paraglider engine ? We are ...
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3answers
927 views

What is the relation between manifold pressure, RPM, and power, in a constant speed prop?

I know that there are similar topics here, one is mine even, but still I have few questions about constant speed propeller. My questions: Why if we decrease RPM and maintain throttle lever setting ...
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2answers
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What helicopter has the most rotor blades?

I have seen 2 rotor blades up to many and wonder when does having more rotor blades become less efficient? What helicopter has the most rotor blades? Related: Why don't helicopters prefer shorter ...
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4answers
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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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8answers
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Why are prop blades not shaped like household fan blades?

My two projects right now are learning to fly and 3D modeling a replacement blade for antique fan, and a question occurred to me: Why are airplane propeller blades not shaped like household fan ...
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6answers
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What's the use of so much torque on propellers?

(This question is closely related to this question) A typical Cessna 172 has a 180 hp engine, with a max. rotational velocity of 2700 RPM. Even small 1 hp electrical motors can achieve that RPM, and ...
35
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6answers
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Why do propeller blades not have winglets?

On the first look this question might sound ridiculous and maybe it is. But as propeller blades act by the same physical laws as wings, and winglets reduce the induced drag by quite a bit, then why ...