Linked Questions

6 votes
5 answers
3k views

What determines maximum speed of a propeller aircraft - Thrust or Power?

I'm reviewing training materials1 for straight and level flight. The content focuses on drag types and explains that the required thrust curve is equivalent to the total drag curve. It then introduces ...
32 votes
2 answers
44k 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 ...
11 votes
7 answers
3k views

Explained intuitively, why does aspect ratio affect induced drag?

Over the last few hours, I've been trying to intuitively understand induced drag, and how aspect ratio affects it. I already know the equations, but while they explain the relationship, they do not ...
7 votes
2 answers
4k views

Why don't contra-rotating propeller configurations with more than two propellers exist?

I wasn't able to find a single example of more than two propellers stacked axially in a contra-rotating configuration. There is a huge number of contra-rotating propeller setups, but it is always a ...
18 votes
4 answers
9k views

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 ...
28 votes
1 answer
18k 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 ...
4 votes
1 answer
605 views

Matching the Drag Equation to Real Airplane Data

I am trying to compute airplane performance for a piston-driven airplane with constant speed prop using the standard equations for Lift, Thrust and Drag. I have found that there are a couple of useful ...
7 votes
3 answers
5k views

What is compressibility drag?

I don't mean wave drag here. What is compressibility drag, which is understood to be a form of miscellaneous drag?
2 votes
1 answer
128 views

What is the range of ratios between optimal propeller efficiency and true propeller efficiency?

In https://aviation.stackexchange.com/a/15383/20394, the optimal prop efficiency is given as: $$\eta^{opt}_{Prop} = \frac{1 - \frac{\Delta v\cdot \left({v_{\infty} + \frac{\Delta v}{2}}\right)}{d_P^2\...
0 votes
1 answer
2k views

static thrust vs. prop RPM data?

edit: question was too long, and is actually simple, so I removed unneccesary description Background: There are many questions here about: propeller efficiency changes to thrust when it is dynamic ...
0 votes
2 answers
908 views

Would large, low aspect ratio fan/propeller blades be more efficient? Why not?

With reference to this answer We read in the above that accelerating a larger mass of air by a smaller amount is (theoretically) more efficient. This is an advantage of a larger propeller than is ...
16 votes
5 answers
4k views

Why is thrust inverse to speed in piston engines?

It is said that piston engines have constant power output, and thus their thrust is inverse to speed (e.g. here), while turbines have relatively constant thrust. I'm looking for an intuitive ...
2 votes
2 answers
503 views

How much is a swashplate system more energy efficient than a fixed blade system for the same load

When reading about the lifting capacity of swashplates (as found in helicopters) vs fixed blade systems (as found in e.g. DJI drones), I read a lot of comments about the fact that the bigger rotors of ...
4 votes
4 answers
2k views

Is there any theoretical problem powering the fan with an electric motor [duplicate]

A question that I have been wondering about lately is whether it would be possible to power the fan in a modern hi-bypass turbofan with an electric motor and achieve performance comparable to the ...
1 vote
1 answer
182 views

Is flow attached at fixed propeller blade at every RPM / speed conditions?

Propeller blade AoA depends on tangential veloctiy caused by rotation and forward speed "head wind". If propeller has fixed pitch is flow attached on blade at every RPM / speed conditions? ...

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