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47 votes
Accepted

Why is the UH-60 tail rotor canted?

John K and Koyovis's answers are both correct. However, as a former pilot of the UH-60 and a mechanical engineer here is a simpler version. A helicopter must be balanced. If the front is much ...
Philip's user avatar
  • 486
26 votes

Why is the UH-60 tail rotor canted?

A guy in my glider club used to fly them. It's something to do with achieving a vertical lift component of several hundred pounds from the tail rotor's thrust, and that and the large horizontal tail ...
John K's user avatar
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23 votes

Why is the UH-60 tail rotor canted?

I came across this in Ray Prouty's book, Helicopter Performance, Stability and Control. The best position for the centre of gravity on a single rotor helicopter is slightly ahead of the main rotor ...
Koyovis's user avatar
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12 votes
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What factors govern the placement of a helicopter's tail rotor (left or right)?

It's hard to say the design rational used for all helicopter manufacturers. Push vs pull doesn't seem to be very important. One example is the Bell UH-1 Huey (Left side Pull). When Bell modified the ...
Walker's user avatar
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10 votes

Why do helicopters need two pedals? Why is one not enough?

Two pedal control is arranged such, that, in helicopters and other aircraft as well, the pedal forces are balaced (by default or by trimming) during straight and level flight. The arrangement ...
Jpe61's user avatar
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8 votes

What are the benefits of a non-orthogonal (scissor) tail-rotor?

Image source The tail rotor of the Apache consists of two 2-bladed teetering rotors, referred to as scissor rotors. This unusual configuration was first implemented by Hughes Helicopters in the late ...
Koyovis's user avatar
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7 votes
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Helicopter mast bumping in low g condition

The answer is yes it could be used in that flight profile as the pilot of that AS300 was never in a low G condition with the rotor unloaded during those maneuvers. Once he dropped the concrete, ...
Romeo_4808N's user avatar
6 votes
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How does a Delta-3 hinge on a helicopter tail rotor work?

It's because the blade's span-wise axis is "swept" relative to its flapping hinge line, so when it flaps, the sweep angle results in the blade's effective AOA changing somewhat (for the advancing ...
John K's user avatar
  • 132k
5 votes

How much force does a helicopter's tail rotor counteract?

The lift-to-drag ratio of the main rotor blades is around 10, so the tail roter has to provide a force equal to one tenth of the aircraft's weight. Of course you have to take into consideration ...
Rainer P.'s user avatar
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5 votes

Why do helicopters need two pedals? Why is one not enough?

There are of course other ways you could control the tail rotor, for instance there is a control adaptation for disabled people where the tail rotor is controlled by hand rather than foot using a yoke ...
GdD's user avatar
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5 votes

Why do helicopters need two pedals? Why is one not enough?

We have two directions in yaw, and we have two feet, so we can afford to have two pedals - one for each direction. One pedal? Theoretically, yes. You can spring load that pedal to make it serve the ...
Aditya Sharma's user avatar
5 votes
Accepted

Why can the rear rotors of helicopters move freely in this direction?

Those are flapping hinges that give the blade some freedom of movement in the flapping axis, to accommodate the variations in lift of the blade as it moves around while the machine is moving forward. ...
John K's user avatar
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4 votes

Helicopter mast bumping in low g condition

Mast bumping is not an issue on articulated rotors (3 blades and up) because the system is not completely dependent on pendulum effect to keep the fuselage/rotor disc relationship within limits like ...
John K's user avatar
  • 132k
4 votes

Helicopter mast bumping in low g condition

Clearly you are speaking of what happens after the helicopter dumps the concrete. A transition to a dive, even a rather steep dive, need not involve a reduction in G-load too much below 1 G as long ...
quiet flyer's user avatar
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3 votes

What factors govern the placement of a helicopter's tail rotor (left or right)?

Location of the tail rotor is the result of mainly: Tractor or pusher type: blow against the vertical fin or away from it. If against the vertical fin, there is a beneficial pseudo ground effect on ...
Koyovis's user avatar
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3 votes

What is the main and tail rotor speed (RPM) for a Sikorsky S52?

Given the $5m$ main rotor radius and the typical blade's tip speed due to the rotation around the hub of some $200m/s$, this gives: $ \omega = v_{tip} / r = 200/5 = 40 [rad/s] = 380rpm $ For the tail ...
sophit's user avatar
  • 13k
3 votes

How does a Delta-3 hinge on a helicopter tail rotor work?

Delta-3 (also spelled $\delta_3$) is a simple yet difficult to visualise concept. I suppose that the best way to understand it is by comparing a rotor with a built-in delta-3 with one without it. The ...
sophit's user avatar
  • 13k
3 votes
Accepted

Why do No Tail Rotor (NOTAR) helicopters use an enclosed variable pitch fan?

They use a shrouded fan because these use less power than a jet for generating the same thrust. I could find a reference in Principles of Helicopter Aerodynamics by J. Gordon Leishman: he states that ...
Koyovis's user avatar
  • 61.8k
3 votes

What are the benefits of a non-orthogonal (scissor) tail-rotor?

I believe its to reduce the noise, here is a partial info http://theses.gla.ac.uk/619/ The complex flowfield which is associated with a rotor wake gives rise to the multitude of aerodynamic ...
Abhyuth's user avatar
  • 91
3 votes

What is the main rotor speed (RPM) of Sikorsky CH-53E Super Stallion?

It says here 185 RPM and 792 RPM for the A model. For the E model with blades are 1.33 meters longer, you need to drop the rotor RPM to about 170 to keep the same blade tip speed. Note that those are ...
John K's user avatar
  • 132k
2 votes

What is the main rotor speed (RPM) of Sikorsky CH-53E Super Stallion?

Sikorsky CH-53E Main rotor tip speed = 732 ft/sec Main rotor radius = 39.5’ Main rotor rpm = 177 Tail rotor tip speed = 733 ft/sec Tail rotor radius = 10’ Tail rotor rpm = 700 Vtip = (R x RPM) / 9....
EETech_Fix's user avatar
2 votes

Why do helicopters need two pedals? Why is one not enough?

It's true that yaw control is only one axis, so a single (1-axis) control lever, as in 1 pedal, would theoretically be enough. In standard helicopter design, the two pedals in a helicopter also only ...
Apfelsaft's user avatar
  • 702
2 votes

For a coaxial rotorcraft, Do horizontal and vertical stabilizers in the tail really make much of a difference?

The horizontal tail surface is there to generate downforce that holds the nose up in cruise. Without it, the faster you go, the more the nose points down as the machine's body wants to "trail&...
John K's user avatar
  • 132k
2 votes
Accepted

Does shutting down the engine affect the rate of rotation during autorotation?

with the engine disconnected from the main rotor, no torque is being applied to the rotor by the engine so there is no torque reaction trying to rotate the fuselage backwards. In this case, the only ...
niels nielsen's user avatar
2 votes

How much force does a helicopter's tail rotor counteract?

The tail rotor on helicopters indeed provides anti-torque thrust, plus thrust for manoeuvring in the yaw axis. A quote from Principles of Helicopter Aerodynamics by j. Gordon Leishman section 6.9: ...
Koyovis's user avatar
  • 61.8k
2 votes

Why is the UH-60 tail rotor canted?

The stabilator has a decided effect on effective lift with the tail rotor. It has a large range of travel, both up and down. This travel combined with the tail rotor thrust augmented by the 20 degree ...
Kevin Cogan's user avatar
1 vote

Why is the UH-60 tail rotor canted?

Gordon Galow the original designer of the helicopter for the US army now 98 years old said it was for the lift. Even at the small percentage angle of the blade it provided some lift. One of the most ...
Craig Galow's user avatar

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