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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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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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1answer
136 views

Difference between constant speed and variable pitch propellers?

Here is how I currently understand constant speed and variable pitch propellers. In constant speed propellers, the pilot controls the governor via the prop control knob and the speeder spring, ...
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0answers
44 views

How accurate is blade element theory?

for a ducted fan/propeller, how accurate is BET? does it overpredict the thrust and underpredictes the torque? in other words, the power absorbed. if so, by what percentage approximately?10%?15%?
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1answer
106 views

Quadcopter: would putting 3 blades on the same level and the other blade below the first three work?

Most quadcopters have their propeller blades all on the same level, or in some cases, a pair of blades placed a little above the other pair. However, I was wondering if three propellers of a ...
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1answer
93 views

What is the meaning of “regular pitch” when applied to a propeller?

I am looking at parameters of a propeller that looks like this: 3 blade xx inch diameter (regular pitch) What does "regular pitch" mean?
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1answer
38 views

Advance ratio formula for drone propeller in vertical climb

According to this wikipedia article. There are two expressions for advance ratio: For propellers: $$J = {V_\infty \over nD} \tag{1}$$ For helicopters: $$\mu = {V_\infty \over \Omega r} \tag{2}$$ We ...
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How does the Angle of attack vary from the root to the tip of a propeller for a fixed pitch prop?

I came across a video while learning about propellers where it showed the angle of attack increased from the root of the propeller to the tip of propeller whose pitch was fixed. I somehow cannot get ...
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Compute Thrust from RPM and Induced Velocity

I'm attempting to calculate the difference in thrust in a secondary propeller operating in the wake behind a primary propeller, in the context of a trailing quad-copter following a leading quad-copter ...
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1answer
224 views

How fast do four Tire-Propellers have to rotate to lift 2000 lbs? [closed]

I just saw this come out, Goodyear's Tire-Propeller Concept – a combination tire that can also act as propeller (well, more like a ducted fan I guess). There's a neat video that goes with it, ...
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1answer
356 views

What is this four-engine propeller airplane?

I came across this print at a bargain store a couple weeks ago. At first I thought it might be a variant of a Lockheed L-188 Electra; then I noticed that it has at least 6 engines, as the print ...
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4answers
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What are some drawbacks to having a wingtip propeller on an aircraft?

I was reading about aircraft concepts that involved wingtip propeller design and was wondering what the drawbacks of such a technology would be. I could not access the full paper but came across this: ...
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2answers
223 views

How do I translate this propeller start procedure into English?

I'm translating a documentary from Hungarian to English. There is a scene where the pilot of an aeroplane with a propeller is preparing for take-off. He says (seemingly into a 2-way radio) two short ...
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1answer
91 views

Is an Aileron Roll Easier Done Opposite The Rotation Of The Plane's Propeller?

We all know helicopters have tail rotors because they would spin out of control thanks to Newton's third law. That got me thinking, would a single propeller plane have an easier time doing an Aileron ...
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1answer
81 views

How can I calculate the velocity of air drawn by a pusher configured propeller?

I am attempting to construct a model plane using Custer channel wings. In order to calculate (or at least approximate) the lift generated I need to find the speed of the air through the channel due to ...
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1answer
157 views

Which propeller configuration is the one that generates the least turbulent flow in a wind tunnel?

I looked at the post here but still have some questions Why are push-propellers so rare, yet they are still around? This is along the same idea but the answers are not too helpful either. Pros and ...
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2answers
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Do any propellers/propfans use stator vanes? Why is this not a commonplace feature?

I understand that axial-flow turbine engines generally include stator vanes behind every(?) compressor and turbine stage. This makes quite intuitively sense, because without them the rotating blades ...
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1answer
252 views

If a twin-engine airplane's propellers both rotate in the same direction, do they still produce a left-turning tendency?

If an airplane with two propellers has both propellers with the same rotation direction (say, both the propellers rotate counter-clockwise as seen from nose to the tail), will be the four left-...
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1answer
109 views

How does propellers' pitch change during the use of reverse thrust in turboprop/propfan propelled planes?

Which way do proplellers turn during the use of reverse thrust in turboprop/propfan propelled planes: A) Do the leading and trailing edges of propellers remain the same or... B) Do the propellers ...
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2answers
317 views

Why does a hovercraft lift blade look one way, but a propeller another?

The lift blade of a hovercraft looks like this: Note the ten rectangular blades. The blade of a propeller-craft looks this this: Note the three, traditional airfoil-shaped blades. Why are the two ...
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1answer
231 views

Identify an USAF transport aircraft in Greenland around 1960

Could anybody help me identify this aircraft? It was photographed in Greenland around 1960. Thanks in advance.
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4answers
187 views

Could an airplane takeoff with a very strong tailwind if its propeller blades are set to a negative pitch? [closed]

Would it be possible for an airplane to accelerate and takeoff with a very strong tailwind if its propeller blades are set to a negative pitch? For example, let's say that a hurricane was approaching ...
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2answers
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What's the difference between a “runaway prop” and a “feathered prop”?

My father was a P-51 fighter pilot in WWII. Another P-51 flown by a buddy of his suffered a "runaway prop", and as a result of that, the plane could not maintain its normal high speed, and in the end, ...
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1answer
231 views

Why should autofeather only be used for take off on the Dash-8 Q400?

The Bombardier Dash-8 Q400 FCOM says (emphasis mine): The autofeather system provides automatically initiated propeller feathering following an engine failure during take-off, and power uptrim of ...
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3answers
303 views

Is the purpose of variable pitch propellers to maintain an optimal angle of attack?

I recently had a discussion with an aviation expert, who works as a Flight Instructor, about constant speed propellers - variable pitch propellers - on light piston aircraft. I have always known that ...
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42 views

What's the difference between a propeller that is installed infront of the airplane (nose) and a propeller that is installed behind the nose? [duplicate]

What are the pros and cons of having a propeller in front of the airplane nose rather than behind it ?
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63 views

flow rate through a propeller disc

Let's take the case of a stock Cessna 150, chained to the ground, standard day conditions. The engine is running at full power (say 2500RPM) and the propeller is absorbing its full output. Is there a ...
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1answer
178 views

Could a quadcopter fly if its propellers were encased in cylindrical tubes?

Picture a standard quadcopter, with regular old propeller guards, which are generally just circles around the propellers. Now, take the propeller guards and stretch them so that they're cylinders ...
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3answers
253 views

Why hasn't anyone tried making two propellers facing upwards and the other two facing downwards? [closed]

Within a quadcopter, I know usually it's all the propellers facing upwards or all of them facing downwards. Why hasn't anyone tried making two propellers facing upwards and the other two facing ...
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3answers
175 views

Can quadcopters still fly with propellers at an angle?

Can quadcopters still fly with propellers at an angle? By this I mean like the whole motor mounts will be situated along a certain slope (so as to be neither horizontal nor vertical). UPDATE I meant ...
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1answer
73 views

quadcopters — should the propellers/motors all be at the same height

In quadcopters (or in any other drones), must the propellers/motors all be at the same height, or can there be symmetric height differences (like for eg, two of the motors at the "back" are elevated ...
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0answers
46 views

How to compute actuator torque requirement for Variable pitch mechanism??

Suggest me any reference to compute the torque requirement for actuator/motor to control the pitch angle of propeller (Variable Pitch Propeller). Thanks in advance Arun Ravindran
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1answer
295 views

What are these small propellers in the A330 MRTT's wings?

In actual flight there are small propellers rotating at the front of these "pillars". What are they? They are visible in this video.
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1answer
355 views

What is the Efficiency of Cessna-150's Propeller?

From that Cessna-150's data, it used Continental 0-200-A 100 HP (75 kW) at 2,750 RPM and with Fixed Pitch propeller with its diameter=69 inches. If power is delivered maximum to the propeller (through ...
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2answers
186 views

Must quadcopters have the same propeller sizes?

I was flying quads today and it just suddenly popped up into my mind — do the propellers all have to be the same size in quadcopters? Mine are, but What if two propellers were larger and the other two ...
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2answers
388 views

Does RPM refer to the speed of the engine or the speed of the propeller?

I followed discussion here: In a constant speed propeller, why does the RPM drop with a prop pitch increase?, I got confused about the RPM there. As the opening statement said in that discussion, "...
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3answers
267 views

Does shrouding a propeller minimize induced drag by equalizing the downwash velocity along its blades?

EDIT: It's not a duplicate of Are ducted fans more efficient? That question and the answers doesn't address the reason for the higher theoretical efficiency, it is more about efficiency in practice (...
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Does Froude Efficiency represent an upper bound for propellers in certain flight / aircraft conditions?

I used the Simple Propeller Theory to calculate the Froude Efficiency for my theoretical propeller-driven craft (at 65k feet). Here are the results: https://ibb.co/kPPqzU. My results were that, for ...
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2answers
198 views

How is a propeller diameter for given application determined?

let's say I need 1000 N of thrust for a given aircraft and flight velocity. I have available a fixed pitch propeller with a given shape, and thus given performance to advance ratio curves. Let's say ...
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2answers
261 views

Propeller Characteristics at Different Altitudes

Assuming I have a propeller with a given diameter (D), pitch, blade twist, and number of blades, I can theoretically analyze discrete airfoil sections in XFOIL and come up with lift and drag polars ...
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1answer
275 views

Propeller Efficiency calculation different by two methods

Please refer to this MIT page which I used for my calculations: https://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node86.html I calculated my aircraft propeller's prop, thrust, and torque ...
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4answers
549 views

Does the required torque to spin a propeller increase with RPM?

I‘ve currently been experimenting with different propellers: 12x12 prop, 16x12 prop (both two blades) and a 22x14 (6 blades) prop. They were propelled by a 2.4 kW electric motor with 260 kV on a 6S/...
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6answers
342 views

Is precession a problem for two-bladed propellers?

The vast majority of wind turbines are a three-bladed design. Although two blades would be more efficient, two-bladed designs are more likely to suffer from precession. Do two-bladed propellers suffer ...
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3answers
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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
176 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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92 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
368 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
124 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
232 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
242 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
229 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 ...