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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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4answers
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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-...
28
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4answers
7k views

Do propeller planes give contrails like jets do?

Last weekend, while watching the second world war film "Fury" with a friend, there was a scene near the end with a large set of bombers flying overhead, leaving large contrails. That seemed wrong to ...
7
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2answers
500 views

Would a coaxial propeller with the second prop slower and larger improve speed?

Looking at various propeller designs, I started wondering about these limitations: Large propellers at high speeds have tips going supersonic Scimitar props attempt to keep prop tip from going ...
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6answers
7k views

Why don't drones use ducted fans?

If efficiency of converting battery power to lift or thrust is paramount, why don't drones use shrouded or ducted fans, instead of unshrouded propellers? This is the only image I could find to ...
1
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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%?
1
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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 ...
1
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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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2answers
104 views

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 ...
1
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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 ...
3
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2answers
217 views

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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0answers
20 views

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 ...
1
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1answer
80 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 ...
2
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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, ...
9
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1answer
548 views

In a piston aircraft, how much noise is generated by the engine, and how much by the propeller?

I've been reading quite a few articles lately about how noise complaints from GA airports across the country. One of the common suggestions to fix the issue is to simply use an electric engine ...
4
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2answers
1k views

What are these circles around the propeller?

(Source: www.airliners.net) These circles I believe are the wing tip vortex formed by the propeller tips or is it just due to the rotation of the propeller. How does this occur?
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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 ...
4
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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-...
14
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8answers
9k views

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 ...
4
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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 ...
10
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4answers
2k views

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: ...
20
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4answers
3k views

Would an aircraft with contra-rotating propellers longer than the plane's wingspan be able to fly?

I enjoy taking the time to try and visualize how fictional aircraft might actually work in reality. Unfortunately there are some that seem highly impractical from an engineering student's point of ...
3
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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 ...
3
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3answers
266 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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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 ...
4
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0answers
260 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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1answer
155 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 ...
2
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1answer
108 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 ...
3
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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 ...
6
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2answers
1k views

At what point is a turbine powered ducted propeller considered a turbofan?

Turboprop Propellers can be ducted for extra thrust. What are the criteria for determining that the engine is no longer a ducted propeller design, but a turbofan? Does there have to be a type of ...
4
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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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2answers
18k views

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 ...
22
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2answers
20k views

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 ...
29
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5answers
8k views

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 ...
7
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1answer
212 views

How does the performance of an aircrafts propeller change with respect to distance from obstructions?

I am interested to know if there are any changes in propeller performance (thrust, efficiency) with respect to distance from obstructions such as the fuselage or wings? I am particularly looking for ...
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4answers
186 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 ...
22
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2answers
4k views

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, ...
1
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1answer
224 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 ...
14
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4answers
7k views

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 ...
0
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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 ...
1
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2answers
258 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 ...
2
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3answers
301 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 ...
18
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4answers
3k views

Are there design differences between propellers powered by air (wind-power) and propellers for aviation?

What is the difference of design between a propeller designed to be powered by the wind (i.e. those huge wind power turbine blades) and those designed to be used to propel a plane that are powered by ...
0
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0answers
62 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 ...
3
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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 ...
0
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1answer
353 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 ...
0
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3answers
252 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 ...
2
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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 ...