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26 votes
Accepted

Why do helicopters experience a brief dip in altitude during IGE marginal power takeoffs?

There is a discussion of this phenomenon in Raymond Prouty's book Helicopter Performance, Stability and Control. Chapter 3 describes momentum methods for the physics in forward flight, including the ...
Koyovis's user avatar
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11 votes
Accepted

Is there a minimum start altitude for autorotation landings?

What you're looking for is the height/velocity curve, some times called the 'dead man's curve'. This shows the altitude and speed requirements for a safe autorotation, plus the height and altitude ...
tj1000's user avatar
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7 votes

How much could human power add to the endurance of an electric gyrocopter?

According to the wikipedia page on "Human Power", a trained cyclist can produce about 400 watts of mechanical power for an hour or more, adults of good average fitness can produce between 50-150 watts ...
Devil07's user avatar
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4 votes

When starting a turbine helicopter, why should one slowly increase RPM (throttle)?

he probably wanted to make sure the oil pump keeps up with the engine and bearings won't run hot, or that the oil circuit gets primed. turboshaft engines dont like it when running at idle, they tend ...
WindSoul's user avatar
  • 372
4 votes

Why are rotary wing aircraft less efficient than fixed wing aircraft?

Very good question. Lower efficiency is exactly the same thing as lower lift-to-drag ratio. Helicopters have a lot of extra drag that fixed wing planes don't have: Complex interference drag from the ...
Koyovis's user avatar
  • 61.8k
4 votes

Do coaxial rotors provide twice the amount of lift?

Yes they can give twice the amount of lift if blade angle of attack is a variable, but require more power to do so. Momentum theory predicts: a 28% power penalty on this configuration, when compared ...
Koyovis's user avatar
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3 votes

Could floppy rotor blades be usable?

For thrust to pull on the hub, a propeller blade must be able to transfer shear loads from the circumference to the center. Add a bending moment when the distance between the circumference and the hub ...
Peter Kämpf's user avatar
3 votes

Is a fixed wing more efficient in reaching a certain altitude than rotary wing?

A helicopter in forward flight is more efficient than a helicopter in vertical hover, due to less induced drag (and more form drag which becomes a problem at high fwd speed). Fixed wing aircraft are ...
Koyovis's user avatar
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2 votes

How much could human power add to the endurance of an electric gyrocopter?

One has to look at the total energy requirement of the gyrocopter. In this instance it is a 80 kW powerplant. A human power plant would be incapable of a sustained output of more than 1kW, therefore ...
mongo's user avatar
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2 votes

Clarification on autogyro thrust formula

Weight is a force by definition. Its SI unit is newton. In most circumstances, weight is equal to $F=mg$. The quantity in kilograms is called mass. In colloquial speech it is often called weight ...
Sanchises's user avatar
  • 13.4k
2 votes

Clarification on autogyro thrust formula

In vertical autorotation, with a constant sink velocity, the lifting force produced by the rotor is exactly equal to the weight of the gyro, since any difference between weight and lift would cause an ...
xxavier's user avatar
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2 votes

When starting a turbine helicopter, why should one slowly increase RPM (throttle)?

Well I hope he gave more of an answer than what you quoted above. But it is indeed to do with oil - if you advance the throttle too fast, there is the potential for the engine's demand for oil to ...
James D's user avatar
  • 228
2 votes

Normal tendency of helicopter with counter clockwise rotating main rotors (top view) with force trim off and leaving controls?

With a American made helicopter equipped with a CCW rotating rotor, the helicopter will, as it accelerates past 10-15 KIAS, begin to pitch nose up as well as roll to the right. This is a direct ...
Romeo_4808N's user avatar
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1 vote

Normal tendency of helicopter with counter clockwise rotating main rotors (top view) with force trim off and leaving controls?

Both of the previous answers are really good, but if you're after a practical answer to your question I thought I'd see what happens in an EC135 (CCW rotor). With the Autostabilisation and back-up SAS ...
Rob Wilkinson's user avatar
1 vote

Normal tendency of helicopter with counter clockwise rotating main rotors (top view) with force trim off and leaving controls?

The answer depends on what disturbs the helicopter (with no disturbance it has no tendency). For example, let's say there's a gust of headwind, blowing into the nose of the aircraft, increasing the ...
Mat's user avatar
  • 440
1 vote

Is there a minimum start altitude for autorotation landings?

There are different techniques for low altitude autorotations and high altitude autorotations. If your altitude is low, you most probably have to land directly ahead and you will only have time to ...
tekin beyaz's user avatar
1 vote

Is a fixed wing more efficient in reaching a certain altitude than rotary wing?

The first human powered airplane flew in 1977, and a later version https://en.wikipedia.org/wiki/MacCready_Gossamer_Albatross in 1979. The first human powered helicopter flew in 1989. The Wikipedia ...
Dan Pichelman's user avatar
1 vote

Is a propeller a wing?

When one thinks with respect to plane, things are a lot less "muddy". Forget about definitions and rote and focus on what the function is. First, while airborne, the only thing with respect to ground ...
Robert DiGiovanni's user avatar

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