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

The only turbprop I've travelled is the ATR 72. I've noticed that the props' rev go down (for like a second, the sound also goes down) just before engaging full throttle in order to takeoff. I've ...
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1answer
136 views

How does the load transfer from a prop to the airframe?

I was just watching this video... Restoration and startup of a Wright 1820 Cyclone ...and it got me thinking: a propeller shoves back air, and this creates a forward force on the prop. The prop ...
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65 views

Propeller air displacement

I was thinking about propeller design just now and it came to mind that, theoretically, the air displaced by the propeller after every rotation might not be able to "flow back" into the area "served" ...
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3answers
243 views

Why are helicopters less efficient than planes?

At higher speeds, advancing helicopter blades will operate at velocities approaching mach 1, reducing efficiency. But what about lower speeds? A helicopter is basically a wingless plane with a giant ...
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1answer
114 views

What would happen if blades are not pitched correctly on a propeller blades? [closed]

What would happen on a 6 blade propeller if each blade opposite another was pitched in completely the opposite direction.
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1answer
146 views

How much thrust could a 400 mm EDF produce?

there's a 195mm EDF from Schübeler that produces 25 kg of thrust at a peak power consumption of 15 kW: https://www.schuebeler-jets.de/de/produkte/hst Now, my question is: How much thrust could you ...
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1answer
171 views

Why divide the blades of a 9 blade propeller into 3 groups?

In a youtube video an airboat is featured with two contra-rotating propellers, each holding nine blades. Interestingly those nine blades are not spaced evenly, but grouped into three groups. I've ...
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1answer
130 views

How do you maximize an electric engines thrust?

I‘ve been recently looking for answers to this question on the internet but the jungle of propellers, fans and electric motors didn‘t quite get me an anwer. How would I have to design an electric ...
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1answer
114 views

What are dimensions of the B-17 propellers?

I'm curious about the aerodynamics of the Boeing B-17 propeller, as the proportions looks perfect for a project I'm working up. Does anyone out there know where to find the specs/dimensions/models for ...
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177 views

How are the Tupolev Tu-95's blades shaped?

The Tupolev Tu-95 "Bear" seems like an awfully cool piece of innovation with its unusual contra-rotating supersonic-tipped props. From what I've been reading it sounds like it's been the only mass ...
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0answers
141 views

Will leaving the ducting on the propellers attached to a DIY aircraft give it more thrust? [duplicate]

I'm not sure if its the right place, I have a problem with a flying thingy, and you like flying thingies, don't you? I will be trying to add some means of propulsion to my friend's styrofoam plane (...
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0answers
79 views

How does a partially covered air intake affect the thrust of a propeller ?

does a partially covered air intake of a ducted propeller significantly affect its thrust? If so, will it be like 10 or rather 90 percent less thrust ? Thanks for your answers! Simon
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2answers
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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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2answers
72 views

How does radius of a propeller affect its performance?

Let's say we have a conventional two-bladed fixed-pitch propeller. All things being equal, would the same propeller but with half the size -- 50% radius, have 50% of the performance of the first ...
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0answers
37 views

How does the number of blades affect the static thrust of a propeller? [duplicate]

Since I couldn‘t find an answer to this question I thought I‘d ask you guys! By which factor does the thrust of a propeller increase if I double the number of blades, the motor being powerful enough ...
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1answer
323 views

Is 1 propeller always more efficient than 2?

Based on other answers I've read here (1) (2) (3), a single large blade propeller is the most efficient type of thrust you can get. There are 2 reasons for this (as I understand it). Firstly, ...
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2answers
763 views

Is it harmful to operate an engine “over square”? [duplicate]

Never Fly Your Engine "Oversquare!" is an old recommendation. This wisdom cautions pilots that selecting a power setting with a manifold pressure in inches higher than the RPM in hundreds is damaging ...
3
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1answer
215 views

What‘s the thrust of two stacked propellers?

Let‘s say that you have two identical propellers and each is powered by their own motor and together they produce a thrust of 1 kN. How does the thrust change if instead of operating them side on side ...
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1answer
115 views

On a ducted propeller, how does duct length affect thrust?

So if we are looking at an aircraft with a ducted propeller (or a high bypass turbofan engine), does it matter how long the duct is? As an extreme example, would having a duct that extends 100 feet ...
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3answers
353 views

Did WW2-era aircraft have constant-speed or variable-pitch props?

This is slightly related to my other question on variable-pitch controls. I want to know if WW2-era aircraft typically had variable-pitch or constant-speed propellers. Variable-pitch lets the pilot ...
2
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1answer
111 views

How did the controls work for variable-pitch props?

Variable-pitch propellers date way back to the 1930's and even earlier. I would like to know, what kind of controls they used? Some kind of lever or crank? How heavy were these controls? I'm thinking ...
6
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3answers
332 views

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 are there extra restrictions on constant-speed propellers?

Constant-speed propellers are far more efficient than non-constant-speed propellers, allow the engine to be made considerably simpler (due to removing the need to continuously adjust the ignition ...
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1answer
66 views

Propeller Curve Modification on Test Rig

this is my first stack exchange question so please bear with me if I have missed a rule: I tried searching for this question to no avail. I have an off-the-shelf propeller for the purpose of eventual ...
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1answer
155 views

Why don't the ATR 42's propellers start/stop rotating simultaneously?

Why is it that for the ATR 42 one of the propellers begins to rotate before of the other? I've noticed that they also stop rotating at different times. Is there a reason for that or is it just for ...
3
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1answer
134 views

Why autogyros use pusher-, whereas, piston-engined planes use puller-configuration?

I found that most modern gyrocopters use a pusher-configuration, whereas, most piston-engined planes use puller-configuration. Since the pusher-configuration has major disadvantages, are there ...
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0answers
131 views

Why don't helicopter rotors use curved blades? Curved from the top view. [duplicate]

I'm studying blade element analysis and I tried applying it to curved rectangular blades instead of straight ones. It doesn't really show any significant changes in the inflow ratio computation. Why ...
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2answers
297 views

Pros and cons of a pull-push propeller configuration [closed]

What are the pros and cons of a pull push propeller in comparison to a counter rotating propeller?
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2answers
389 views

How to realistically model propeller static thrust?

I am graphing static thrust vs prop diameter for a 600 kW motor and a prop diameter up to 5 m. I have seen the post 'What is the equation for calculating static thrust?' and using its formula and ...
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2answers
160 views

How long does it take for a propeller engine to spool-up?

To build further upon the question Why does a turboprop lag?, the following: Assuming a propeller engine is running in idle and the throttle lever is switched to full thrust instantaneously at t = 0 ...
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1answer
130 views

Is a cambered or symmetrical propeller airfoil more efficient?

Is an cambered propeller more efficient than a symmetrical propeller for a low speed airplane?
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3answers
274 views

Will the steep beta descent mode become illegal for new aircraft?

The PC6 is a popular skydiver carrier due to its ability to use steep nose down beta descent to get back to the ground quickly, even beating free falling skydivers. (YouTube) FAA AC25.1155x (I only ...
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1answer
79 views

Consumer Drones with multi-blade (more than 2) propellers

Maybe unusual question but it's related to Aviation world, even if is more directly related to Drones one. Why almost all consumer drones like DJI's and Yuneec's ones (but it's true also for other ...
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How to properly estimate induced flow

Good day. I am currently in a group that is projecting a rotor that when launched must enter in autorotation. The estimated velocity of descent is $V_z=1.29$ $m/s$ which is approximately the same ...
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3answers
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At what rpm does the tip of a 54" propeller start to incur mach losses?

At what rpm does the tip of a 54 inches propeller start to incur mach losses? The max rpm of my engine is 3600.
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2answers
178 views

Is a propeller with two long blades more efficient than one with three shorter blades? [duplicate]

Is a longer, two-bladed propeller more efficient than a three-bladed propeller with a smaller diameter?
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2answers
201 views

Which engine manual must a pilot legally use?

Many aircraft have engine/prop performance information provided by the manufacture such as Bonanza, Cessna, Mooney, etc AND the engine manufacture. The performance or recommended settings may vary ...
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0answers
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Would a coaxial propeller with the 2nd prop slower and larger improve speed?

Looking at various propeller designs, started wondering these limitations --Large propellers at high speeds have tips going supersonic --Scimitar props attempt to keep prop tip from going supersonic....
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1answer
157 views

Does the direction of rotation of the propeller affect the direction of the thrust generated?

Does changing the direction of rotation of the propeller from clockwise to anti-clockwise change the direction of thrust it generates?
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1answer
127 views

In what way are the airfoils used for a propeller different from the ones used in turbofan engine?

Airfoils are used in the blades of a propeller as well as the blades of the fan, axial compressor and turbine in a turbofan engine. Thus, the airfoils used in above two applications have different ...
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159 views

Is this equation for propeller thrust correct?

From dimensional considerations, and assuming that the power $P$ applied to a propeller of diameter $D$ moving at an axial speed $V$ is 100% converted to the acceleration of a mass of air with density ...
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0answers
131 views

What is the relationship between speed, torque and pitch in a helicopter?

Can someone clarify the relationship between aircraft speed, torque, prop length and pitch and how this applies to a helicopter. In addition I want to know if the amount of lift a helicopter ...
11
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1answer
349 views

Why do helicopter rotors have constant section and angle of attack?

As I understand it helicopter rotor blades keep a constant aerofoil section along their length, and are not twisted. Other rotating aerodynamic devices such as propellors, turbofan fans and wind ...
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2answers
487 views

How do propeller planes suddenly make noise?

I was wondering: how can a propeller plane, single engine or otherwise, be flying along relatively silently and then start making noise, often very loud--and then turn it off just as quickly? Are they ...
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1answer
280 views

Is there a fixed-wing aircraft that uses a scissor propeller configuration?

(Source: primeportal.net) Has there ever been a fixed-wing aircraft whose propeller is in a scissor configuration? Like the Apache's tail-rotor seen here: What are the benefits of a non-orthogonal (...
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0answers
63 views

Would propellers be more efficient if they were mounted at the rear of the aircraft? [duplicate]

The propellers of a front-mounted propeller plane push air back directly on a collision course with the aircraft's body. That results in zero thrust or negative thrust from at least some sections of ...
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2answers
342 views

How much safer does painting prop tips make a plane?

While re-reading one of my earlier questions, the answers left me wondering how much good painted tips on props actually does. I did some searching for statistics but didn't come up with much. Are ...
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0answers
142 views

What typical improvements in lift/drag are gained using dimple & zig-zag strips? [duplicate]

A golf ball goes twice as far using a dimpled surface. Many European aircraft (especially gliders) use dimple strips or zig-zag tape on propellers, wings, struts etc. Very few US aircraft use these ...
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What are the design trade-offs between a pusher and a puller propeller? [duplicate]

Wich is the difference in having the propeller forward or back in an airplane. I would like to know the technical differences like in a Piaggio 180 or in a normal Cessna.