Linked Questions

1
vote
1answer
7k views

How to calculate the thrust of a piston or turboprop engine? [duplicate]

This spawns from a related question. Propeller-drive engines (piston/turboprops) seem to always list their output in horsepower or kilowatts, which are units of power. I want to know the engine's ...
0
votes
3answers
156 views

How much can 3 fans 7 inches in diameter and each a generating 160 cubic feet per minute airflow rate lift? [duplicate]

I'm working on a hoverboard project and am having trouble finding out the maximum weight these fans could lift.
66
votes
10answers
80k views

Why do jet engines get better fuel efficiency at high altitudes?

I'm told that this is true, but I can't imagine why. It seems like the fact that there is less air would make the engines less efficient... But that probably just shows how little I know about jet ...
24
votes
7answers
8k views

Given the same engine, why install a gearbox on a turboprop but not on a turbofan?

I am reading the book Mechanics and Thermodynamics of Propulsion, by Hill and Peterson. I found out this image while reading the chapter 5, "Thermodynamics of Aircraft Engines": Why would there be a ...
32
votes
6answers
9k views

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 ...
32
votes
5answers
12k 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 ...
6
votes
5answers
3k views

How much horsepower to weight is required for a 1:1 thrust ratio?

I did a math experiment today, but wanted to verify the results. I wanted to figure out how much horsepower is needed for an aircraft to hover in midair with no wings/lifting body (1:1 thrust/weight)....
16
votes
2answers
20k views

What are the advantages and disadvantages of ducted fans in designs such as the Airbus E-Fan?

I have read that it increases thrust and reduces noise. Is there a downside to this? (Image source: Wikipedia)
15
votes
4answers
10k 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 ...
7
votes
3answers
9k views

Why don't helicopters prefer shorter rotors with more blades? [duplicate]

My understanding of helicopters is that, despite theoretically increasing efficiency, longer blades are worse in practice than short ones in every respect (except, perhaps, cost): Longer blades are ...
8
votes
5answers
539 views

What factors influence the maximum speed of an airship?

I'm interested in learning about the physics of airships; in particular, how you determine an airships maximum speed. For example, the Hindenburg topped out at about 80 mph. The ship itself weighed ...
6
votes
1answer
20k views

Which are typical rpm values for aeronautical turbines?

I wonder which of these has higher or lower rotational speed: turboshaft turbofan turbojet turboprop Does anybody know the typical speeds for these kind of engines?
5
votes
4answers
2k views

Can this design provide more lift force than thrust from engine?

The problem is depicted in the picture: Generally, why we don't use engine blow wings to fly? Can we use wind-tunnel-like wing to generate lift force? Can it generate more lift than thrust? If it ...
6
votes
3answers
1k views

Would it take 7 to 10 times more energy to lift a turbofan-helicopter?

I want to figure out how much energy it would take to lift a turbofan-helicopter. For reference I started with a rotor helicopter and assumed $T=100\ \mathrm{kN}$ gross weight and $d = 16\ \mathrm m$ ...
10
votes
2answers
2k views

What is the maximum theoretical lift of a plane as a function of engine power and surface of the wings?

Maximum theoretical lift of a plane as a function of engine power and surface of the wings? I know that the maximum static thrust of a propeller turned by an engine of power $P$ can not be greater ...

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