Linked Questions

45
votes
3answers
17k views

Why is the Tu-95 so efficient despite having propellers that spin faster than the speed of sound?

I've ready many, many times that propellers are not efficient near the speed of sound because it's so hard to get a tip-speed above Mach 1. Then I came across this: It's the Tu-95 "Bear", a ...
37
votes
11answers
46k views

Could an electric engine provide the same performance as jet engines on current aircraft?

I have looked at various questions on this SE site regarding this topic but I have not really found a satisfactory answer. Some comments here regarding torque and power in electric motors vs gasoline ...
30
votes
5answers
10k 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 ...
29
votes
2answers
5k views

Are the fastest moving pieces of a jet engine supersonic?

A jet engine is composed of fast moving pieces. Those pieces are moving into an airmass different form the ambient airmass the aircraft is flying into. The turbine pieces are spinning quite fast, ...
24
votes
7answers
7k 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 ...
24
votes
2answers
13k views

What's P-Factor and why does it occur?

Whenever I hear anyone talking about P-Factor, (whether it be single-engine left turning tendencies or multi-engine loss of directional control scenarios), someone always brings up the fact that the ...
14
votes
3answers
5k views

Did the XF-84H Thunderscreech really cause “900 sonic booms per minute”?

The Republic XF-84H, known as the "Thunderscreech" was an experimental version of the F-84F Thunderstreak. It was intended to be a supersonic turboprop fighter. Even at idle, the prop tips rotated at ...
14
votes
3answers
2k views

Do nacelles around aircraft engines help in reducing the engine sound?

I know that the nacelles around the aircraft engines are actually a housing and are generally lightweight and have may components like inlet cowl, fan cowl, etc., but do they help in reducing the ...
12
votes
2answers
2k views

Why is the bypass ratio of a turboprop higher than turbofan?

Whenever, I come across turboprop, the author always mentions that they have higher bypass ratio than turbofan but no one explains the reason for this. So, is the bypass ratio higher due to higher ...
10
votes
3answers
3k views

Can turboprop blades break the sound barrier?

This question doesn't relate to the actual speed of the aircraft, but of the blades themselves. I have heard helicopters had problems of this happening if the rotors spin too fast it can break the ...
9
votes
2answers
3k views

Why do engine cowl lips appear larger and more blunt on the sides than on the top and bottom?

I was looking into engine nacelles. I was not able to understand the design shape of it Why is it that in most aircraft, the engine cowl lips on the side are bigger (more blunt) than on the top and ...
9
votes
2answers
1k views

Does the ARCA hoverboard violate known limits on small-diameter electric fans?

The ARCA board is being hawked as achieving 430 pounds of lift from 36 electric fan motors for six minutes of 'flight.' c.f. : http://www.theverge.com/2015/12/24/...
8
votes
1answer
5k views

How does a supersonic jet engine differ from a subsonic jet engine? [duplicate]

All jet engines have the same method of air flowing into the engine, which is compressed and ignited. What can engine designers do to make an engine design create more thrust? For example, what is ...
8
votes
1answer
1k views

Why do some turbofan blade have forward swept tips?

I notice that in Trent700 engine fan blade there is no curve extension at the tip unlike in other engine's fan blades such as the GE90 ,T900 etc. What are the purpose of it? Trent 700 without ...
7
votes
1answer
1k views

Rings around propellers [duplicate]

As a followup to Why do turbofan blade tips exceed the speed of sounds while prop tips should not my question is: why have rings on propellers not been used to overcome this problem? It seems from ...