Linked Questions

25 votes
7 answers

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 ...
35 votes
5 answers

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 ...
  • 1,059
20 votes
4 answers

Why are three-bladed helicopters relatively rare?

I admit that this observation is entirely subjective, but it seems to me that there three-bladed rotors are significantly less popular than two or four. Factors that I'm guessing contribute - ...
  • 9,729
9 votes
3 answers

How does blade solidity ratio relate to thrust/power/torque of a propeller?

for quite some time I was using ABBOTT formula for static thrust estimation on a two-bladed propellers: $$ T=6.8\times10^{-5}\times D^{3}\times p\times RPM^{2} $$ $T$ is Static Thrust (N); $D$ is ...
28 votes
2 answers

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 ...
26 votes
2 answers

Is it possible to fly with counterbalanced single blade engines?

Refer the image for counterbalanced single blade (Source In ground school, they took us for aircraft inspection at end of our ground school ...
  • 1,922
20 votes
2 answers

Why are there so many different propeller shapes?

While doing an image search, I found these images of propellers: and Some appear to be straight-ish on the leading edge and curved on the trailing, some curved on the leading edge and straght-ish on ...
  • 10.8k
12 votes
2 answers

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 ...
  • 731
5 votes
2 answers

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 ...
4 votes
2 answers

How does one choose the number of blades and the diameter required for a turboprop propeller?

I am interested in the preliminary design of a regional aircraft that uses turboprops as the propulsion method. Following considerable research online about propeller design (disk theory, BEM...) I am ...
  • 45
3 votes
2 answers

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 ...
1 vote
2 answers

This concerns the GE90X fanjet engine which generates 130,000 LBS of thrust at takeoff [duplicate]

This concerns the GE90X fanjet engine which generates 130,000 LBS of thrust at takeoff. But for this example the engine is secured to a test mount, and under "full throttle", the thrust ...
  • 11
0 votes
2 answers

What is engine power vs propeller thrust relation?

Given: speed 30 knots engine power 70 hp at 5800 RPM propeller 3 blades, diameter 14 inch, pitch 17 inch, at 2300 RPM fluid density 1023 kg/m3 I know that each blade is basically one wing. ...
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0 votes
0 answers

Why does adding more blades to a propeller/fan not show a decrease in efficiency?

According to this answer increasing blade solidity increases the blade area by either enlarging chord or increasing blade count both of which reduce efficiency via reducing the lift coefficient and ...