35 votes
Accepted

Can a helicopter stand on the ground upside down on its rotor head?

Stand on its rotor head? yes, maybe. Spin? not for long. The rotor hub and blades are quite strong and can take the helicopter weight at-least temporarily (leaving aside the balancing issue). The ...
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  • 98.7k
30 votes

Can a helicopter stand on the ground upside down on its rotor head?

This looks like a model that was carefully set up to spin. First the facts: FAR part 27 regulates the design criteria for rotorcraft. Specifically, FAR 27.337 states: The rotorcraft must be designed ...
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24 votes

Is it possible to design a helicopter with fixed rotor blades only (no blade angle/flap/pitch)?

Scaling laws are your enemy here. Model helicopters can be controlled with changes in rotational speed, but for full-sized helicopters the energy needed to quickly change the speed of their rotors ...
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23 votes

Can a helicopter stand on the ground upside down on its rotor head?

Nope, they cannot. There is a hinge in the rotor head that will make the helicopter want to topple over, it won't be spinning like in the video: it is not supported by the blades laying on the ground. ...
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  • 58.8k
17 votes

Is it possible to design a helicopter with fixed rotor blades only (no blade angle/flap/pitch)?

that can not flap or pitch or adjust otherwise? Yes, you can design one like that, but you won't get many people to fly it. In the early days of helicopter flying, any number of crashes occurred ...
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17 votes
Accepted

What are the spikes on Ingenuity's blades?

In the Mars Helicopter Technology Demonstrator paper these are refered as "Chinese weights" and the purpose stated is Chinese weights provide a restoring force on the blade moments when ...
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  • 2,379
11 votes
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Would an aircraft with no ailerons, no elevators and no rudders be safely flyable?

An interesting thought. Control the aeroplane through its propeller(s), like a helicopter does. Propeller torque differential would control roll Propeller cyclic would control both pitch and yaw ...
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9 votes
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How does a hot tip-jet supply fuel to its engines?

There are pipes inside the blades which connect the engines to a rotary seal inside the main rotor head assembly. That seal allows fuel to be pumped into the blades from a port outside the main rotor ...
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8 votes
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What are the mechanisms fitted in the SA321G Super Frelon rotor head?

All rotor heads need to deal with multiple forces but two in particular have a big influence on the design and complexity of the rotor head. As a blade moves forward (the advancing blade), it ...
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  • 30.9k
7 votes

Is it possible to design a helicopter with fixed rotor blades only (no blade angle/flap/pitch)?

Yes, controllability can even be accomplished with only one (rigid) rotor. Degrees of freedom In a three-dimensional space there's generally six degrees of freedom (DoF): forward/backward left/right ...
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  • 2,406
7 votes

Would an aircraft with no ailerons, no elevators and no rudders be safely flyable?

This will work as long as the propellers produce enough thrust and blade pitch can be adjusted fast enough to outrun all eigenmodes. As soon as you need to throttle back (and eventually you must, to ...
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7 votes
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How does the load transfer from a prop to the airframe?

The engine mount is an important component that transfers the prop thrust to the airframe. It's clearly visible in this photograph of a fast and powerful plane, a Bf109. Of course, bearings transfer ...
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  • 10.4k
6 votes
Accepted

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 ...
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  • 107k
4 votes
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What rotors would be best for atmospheric reentry?

You couldn't do it to control reentry, but you certainly could do it for a vertical landing system that might be a bit less technically demanding than a rocket that can descend under control with its ...
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  • 107k
4 votes

Can a helicopter stand on the ground upside down on its rotor head?

According to the Web site, http://www.rotaryaction.com/e.html, the helicopter was a real Hughes 500 with extended landing skids. I would assume that even if the frame was real, they would use a touch ...
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  • 2,324
3 votes
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Why is this type of rotor hub so rare...?

It's basically the teetering Bell/Robinson 2 blade rotor concept applied to a 4 blade rotor. Like a teetering system, the gimballed rotor head accounts for most of the lead/lag/flapping, with ...
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  • 107k
2 votes

Is it possible to design a helicopter with fixed rotor blades only (no blade angle/flap/pitch)?

Theoretically yes, you could build a full-size quadcopter with four fixed pitch rotors, and control it through independent variation of the rpm of each rotor. The power density now achievable in ...
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2 votes

Is it possible to design a helicopter with fixed rotor blades only (no blade angle/flap/pitch)?

It is indeed possible. One of the first helicopters was the Petróczy-Kármán-Žurovec PKZ 2 Helicopter, fitted with two contrarotating, coaxial rotors that had fixed blades, with no provisions for ...
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  • 10.4k
2 votes

what is the statistical risk of head rotor failure?

I worked medium and heavy transport helos in the Marines, and I never heard of an incident caused by a rotor head failure. Blades, transmissions, all kinds of other things, sure, but not main rotor ...
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  • 11.4k
2 votes

Can a helicopter stand on the ground upside down on its rotor head?

No. You have neglected to account for how drive systems work. When the engines engage with the transmission, the blades begin to turn. The sprag clutch/freewheeling unit is only oriented in one ...
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2 votes

How does the Sikorsky X2 technology rotor control blade pitch?

Just as short addendum here: in this particular type of helicopters the rotor is rigid in that the blades are built as stiff as possible and rigidly connected to the hub, apart for the pitch movement. ...
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  • 428
2 votes

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

Delta3 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 delta3 with one without it. The following 2 rotor heads ...
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  • 428
2 votes

What is the function of the Apache's Strap Pack?

Picture above is from Helicopter Performance, Stability, and Control by Ray Prouty, and shows the fully articulated rotor such as installed in the Apache. The Fully Articulated term means that the ...
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  • 58.8k
1 vote

What is the function of the Apache's Strap Pack?

The strap pack is the structural member which transmits loads between the blades and the pitch housing assembly. Not shown in the drawing above is the shear pin that goes down through the hole in the ...
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1 vote

Could a rotor head wing be plausible?

There is no need to attach the wing to the rotor head - simply attach it to the top of the fuselage. You could run the rotor through a hollow tube and attach the wings to that - the inner uncovered ...
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1 vote

Why is this type of rotor hub so rare...?

This type of rotor is not common because flapping blades make the helicopter fly better. Flapping vertically allows the blades to reduce angle of attack as they advance/rise and increase angle of ...
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  • 16.7k
1 vote

Can a helicopter stand on the ground upside down on its rotor head?

Can it...? Yes. But... practically No. The points below explain why the answer is, strictly speaking, yes. But then, they explain why it,s not actually helpful in practice. Note how each case fails so ...
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1 vote

Is it possible to design a helicopter with fixed rotor blades only (no blade angle/flap/pitch)?

Yes and no. I've never seen such a design for a large helicopter but there are plenty of micro sized RC helicopters which utilize such a scheme using a pair of contra rotating main rotors and a ...
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