Gyrobee takeoff and landing

[birdy]

Brian, the reason I call it crap is coz it is simple sales crap. ( mines bigger n faster than the oppositions)
And it's been stated many time by many, more intelligent people than me, besides be,n logical, that wen you near flight rrpm on the prespin, the rotor has most of the machines weight, so you have very little ground contact to stop the forward roll or counter torque.
At flight rrpm, the rotor has all the weight.

I didn't explain why it's rong coz it's been dun many times before.

 

[GyroDoug]

Birdy,

I sure don't mean to argue with you as you have much more experience than I do, but we both know even if the rotors are up near flying speed, you still have to get some air moving by the rotors. That's why I said even with the metro Launch System you still need about 100 ft or about 3 seconds to accelerate some wind past the rotors. (unless you are facing into a head wind and then it is possible to lift of with little or no ground roll, depending on the wind speed) I don't believe I have misrepresented anything in my statement, but if I did please explain it to me and I will be happy to modify information I share with others so I don't continue to misinform anyone. I am very impressed with the capabilities that Larry has designed into the Butterfly Line of Gyros, but I would never exaggerate or misrepresent their capabilities on purpose.

 

[Stan V]

Doug, I believe Birdy is talking about the torc effect the pre-rotor would have on a gyro if it had the ability to rotate to flight RRPM at a stand still. This has nothing to do with landing RRPM un-driven.

 

[WaspAir]

...even if the rotors are up near flying speed, you still have to get some air moving by the rotors. That's why I said even with the metro Launch System you still need about 100 ft or about 3 seconds to accelerate some wind past the rotors. (unless you are facing into a head wind and then it is possible to lift of with little or no ground roll, depending on the wind speed)

A gyro is not (yet) in autorotation when sitting still in calm conditions during pre-spin, but that doesn't mean there's no flow through the rotor.

With fixed collective and 100% flight rpm reached and maintained mechanically (not by forward airspeed), you have lots of induced flow down through your rotor even sitting still with no wind; that's how helicopters take off. But as you get light on the skids for a helicopter, you have a tail rotor to handle the torque. A gyro depends upon the friction of the wheels on the ground, which diminishes as you get lighter, and offers less and less torque compensation. This suggests that there's a big practical difference between what might be called "near" flight rpm and actually being at "100%" flight rpm.

The A&S 18A and the J-2 cope with this to reach and pass 100% rpm by using adjustable collective to go to flat pitch for spin-up, but the typical teetering design doesn't have this available.

 

[birdy]

Doug, Wasp and Stanv has it pretty well covered.
The biggest hurdle if you want to spin to flight rrpm is torque.
Prespining with the stick on the backstop dose a pretty good job of arresting forward roll, if your prespiner/ ERPM ratio is rite, but, without full throttle prop blast over the rudder, it won't stop alota torque. Defiantly not enuf to counter full flight rrpm torque.
Change the ratio so there's more prop blast to better counter the torque, and you'll have too much thrust and you'll skid forward even with the stick full back.

As Wap said, there's not alota rrpm difference between near flying, and flying.
I'v never tried the numbers, but wot your ground breaks, rudder and back stick can counter before loosen control is probably less than 10% under flight rpm.

To compare to powered rotors, the MAP ina GE hover is Usualy near the same as economical cruise.
But To fly out of GE takes considerably more power.
A gyro prespining with full back stick, even if it did break ground, has virtually no GE, coz of the angle of the RTV, so it'd have to be able to prespin well past flight rrpm, with no torque compensation, to actually leave the ground.
The first 20-30' of the ground roll of a high rate prespin is just to get clean air into the disc, coz of the down wash of the fixed pitched rotor.
This is the main reason why I'v always said it's pointless getn close to flight rrpm if you can't keep the spinner engaged till ground break.

 

[RotoPlane]

And Birdy, your post covered all the rest of it.

That is why I've been working on pre-rotating with the blades at zero pitch.....zero lift.
There are times though, when I wish I had went the way taken by this Russian.....that also uses collective.

https://www.youtube.com/watch?feature=endscreen&v=pbOupFXq2qU&NR=1
.

 

[birdy]

Interesting.
Wunder wot that hub bar is made of.
It'd have to be very flexable, and fatigue resistant to handle the stress of widely vaireing rrpm.

 

[jcarleto]

"How do you land then?"
I put the rotor break on to slow um down, how do you do it?

Quick-release on the teeter bolt seems to work.

 

[RotoPlane]

Birdy: I read somewhere that the hub-bar is fiberglass....it looks like plywood .
Other than the collective parts, I believe the rotorhead operates the same as other standard gyros.

Here is a bit more information I've found on this gyro:

Russia Today: Handmade helicopter - YouTube

The in construction gyro has a different rotorhead.
.

 

[GyroDoug]

Corrected!

Corrected!

Stan, JR & Birdy,

Thank you for the explanations. I understood that I was talking about "Near" RRPM Flying Speed rather than absolute 100% RRPM, but I was not thinking about the torque issues you brought up so I was not careful enough with the way I worded my comments. I have gone back to my original post and added the word "Near" and I will be more careful in the future so that I am not misleading anyone with my statements. That 3 to 5 seconds of gaining forward momentum and creating 25 to 30 mph worth of airspeed (both through the rotors and over the rudder) that Larry talks about, are an important part of the process to deal with the torque created by the Pre-Rotator.

 

[jcarleto]

There is a question on the Sport Pilot Instructor knowledge test that asks:

What will happen if a student releases the brakes during pre-rotation prior to releasing the pre-rotator clutch?

The answer they are looking for is:

The gyroplane will turn to the right due to rotor blade torque.


Which goes to show that nobody ever flew a gyroplane that used retired military helicopter blades, I suppose (and the video I took of a Bensen using recycled chopper blades is clearly an illusion). :noidea:

 

[birdy]

???
Wots blade type got to do with torque reaction?

Wouldn't matter if they were gyro blades, heli blades or a plank of wood, the torque still effects the same.

 

[RotoPlane]

If the gyro was sporting Hughes blades, the torque would be to the left, 'cause they must be turned over for mounting and turn CW (looking down).

 

[jcarleto]

Birdy,

A lot of guys used to buy timed-out Hughes rotors from military surplus. They were inexpensive, still had a lot of useful life for gyro use, and would fly a Bensen reasonably well. They just spun up the opposite direction. It drove a lot of them crazy trying to determine exactly which car starter to use to get the right spin direction for pre-rotation.

I would say the FAA is not aware of this or the question would have been modified. However, since all the questions on the Sport Pilot Gyroplane Instructor knowledge test relate specifically to the J2 (probably since it was the only thing for which they had specific and accurate specifications), I doubt any information about other configurations will ever appear in the test question bank.

This is particularly interesting, in that there is also a question about rotor blade angle and specifically its change into flight mode from pre-rotation mode that is unique to the J2. Interesting, because it conflicts with the definition of Light Sport Gyroplanes to which Sport Pilots are limited I'm sure this is an oversight.

§1.1 General definitions.
Light-sport aircraft means an aircraft, other than a helicopter or powered-lift that, since its original certification, has continued to meet the following:

(1) A maximum takeoff weight of not more than—

(i) 1,320 pounds (600 kilograms) for aircraft not intended for operation on water; or

(ii) 1,430 pounds (650 kilograms) for an aircraft intended for operation on water.

(2) A maximum airspeed in level flight with maximum continuous power (VH) of not more than 120 knots CAS under standard atmospheric conditions at sea level.

(3) A maximum never-exceed speed (VNE) of not more than 120 knots CAS for a glider.

(4) A maximum stalling speed or minimum steady flight speed without the use of lift-enhancing devices (VS1) of not more than 45 knots CAS at the aircraft's maximum certificated takeoff weight and most critical center of gravity.

(5) A maximum seating capacity of no more than two persons, including the pilot.

(6) A single, reciprocating engine, if powered.

(7) A fixed or ground-adjustable propeller if a powered aircraft other than a powered glider.

(8) A fixed or feathering propeller system if a powered glider.

(9) A fixed-pitch, semi-rigid, teetering, two-blade rotor system, if a gyroplane.

(10) A nonpressurized cabin, if equipped with a cabin.

(11) Fixed landing gear, except for an aircraft intended for operation on water or a glider.

(12) Fixed or retractable landing gear, or a hull, for an aircraft intended for operation on water.

(13) Fixed or retractable landing gear for a glider.

 

[birdy]

Yeh, riteo, I thought the quiz was bout the torque, not the direction specificaly.

But, speaking of 'official' aviation books, I'v read sum doozys over the years too.

Distinctly remember ones explanation of how auto rotation works went sumthn like, " imagine the blade is like a cake of wet soap, and the pressure of the air surrounding it as your fingers.......".
I'm as sharp as the back of the axe, but I knew that wasn't go,n to work.

 

[Doug Riley]

Birdy:

Do you blokes grow watermelons in Oz? Another explanation along the same lines of the soap is that the blade is like a watermelon seed squeezed between your fingers.

Everybody knows that you don't squeeze 'em, you spit 'em.

 

[DangerBird]

Gyrobee takeoff

Gyrobee takeoff

Sorry I'm late on this one, but if anyone can remember, I prerotated my bee (I can't remember the exact speed) fast enough that I could be in the air in 100 feet or less. ask Dana Linn, he saw me do it many times

 

[phantom]

Bensen built a gyro that could do a vertical takeoff with a 25 hp prerotator and a 90 Mac , it hovered in a very nose high attitude and was not for a low time pilot,I think this is the only thing that a small prop is better at on a gyro,you can get more torque compensation from a reasonable amount of rudder.

Norm