Magni M14 down in Germany

Without being confrontational, I'm truly interested in understanding what is meant by "a rotor generating zero lift can't flap". If you spin a set of blades parallel to the air flow (would be the case pointed straight down in a fall), they would generate no lift. With a low rrpm at the start of the fall, it seems to me the air speed would quickly increase to the point of flap. Flap to me being, retreating blade stall. I can see where there wold be no flap if the advancing blade had no lift, but I was under the impession rotor lift was a function of blade lift. One blade lifting and one blade stalled would leave no rotor lift, but it sure does want to corkscrew.

Phil.
 
A rotor generating zero lift can’t flap whether airspeed is outrunning rpm or not. You know that, Birdy.
I do know that CB, but youv missed my point.
If a machine is in a nose dive, with deminished RRPM, the advancing blade will have alot more lift than the retreating one, causing destructive flap.
They wont be generating any noticable lift on the machine coz of the low AOA and RPM, but the lift differential between the two will make them flap wildly.
A machine with a big HS, 0 AS and low RRPM, will nose down sharply coz of the virtical tragectory, and the blades wont catch up before the AC reaches VNE, coz they will flap first. And without sufficiant RRPM, theres no way of changing the ACs pitch. splat.
All of this will only happen of course, if the blades havnt chopped the ass off the machine first as the HS violently changes the fall from ass first to nose first.

Rule #1 for gyros is to get off the power if approaching a critical out of control situation.
And,
Wen in dout, cut it out [power] and level out.
mean the same thing.

The 912, witch is carburetted by a Bing CV 54 float carburettor, will stop quite rapidly if the engine (carburettors) unload to zero or negative G's. Even just a to high attitude or bank without much positive G's is enough.
Im not go'n to argue this point MOL, coz i 'assume' any carbed engine on an AC would do the same thing.
But for safty sake, dont realie on it, coz of all the low G, neg G and sustained greater than 90* banks iv don, never has the 912 faltered, or even hesitate.

Without being confrontational, I'm truly interested in understanding what is meant by "a rotor generating zero lift can't flap".
Its not often an assymetrical gyro blade will produce NO lift.
Itd have to be at roughly -4* AOA to produce NO lift.
For an instant it will, as it transitions from normal lift at S/L to neg G in a strong downdraft, but not long enuf for a pilot to notice.
If, for sum freak of missfortune, you had your blades both spining with an AOA of bout -4*, youd only have to move the stick back, feeding sum cyclic into them, and the disc would fly into a new plain of rotation/ AOA.

But no dout CB will find plenty of holes in my blab to sink me. :)
 
Birdy, I agree about blade lift. My misunderstanding is rotor lift. The rotor in question has two blades. Lift on one blade and negative on the other, the rotor won't have lift, but it will want to rotate (flap). Same thing your saying. Now, we wait for the buckshot.

Phil.
 
A fixed wing instructor with less than 50 hours experience in gyroplanes flying in an aerobatic airshow a high performant gyroplane is an explosif mixture.

JOS
 
Explain "roll into a bank"

Explain "roll into a bank"

Doug Riley said:
If you must do a pullup in front of a crowd, do as Ken Brock always did: roll into a bank as your airspeed drops to normal. This will prevent the rotor from experiencing zero angle of attack and unloading.
Click to expand...

Doug, explain the physics and aerodynamics involved with the banking maneuver. I am not sure of what you mean by "as your airspeed drops to normal"
 
I'm assuming that you start your "zoom" climb with more than cruise airspeed. You therefore start the maneuver by using the aircraft's kinetic energy as extra thrust (or impulse). This produces a rate of climb greater than the rate that you could obtain using only engine power.

As you climb, you are consuming your kinetic energy (by converting it into other forms). Therefore, the gyro's airspeed will be dropping during the zoom.

Start a bank as the airspeed reaches normal cruise. IOW, perform a climbing turn rather than a straight-ahead zoom to very low airspeed.

If you fail to do this, there is a chance that rotor AOA will reach a very low value as the zoom progresses. If the gyro still has some upward momentum, full power but little airspeed, you'll shed RRPM very quickly. You simply won't be shoving much air through your rotor to keep it spinning.

Turning, OTOH, requires you to increase rotor AOA and thereby prevents RRPM loss.
 
Banking, at any pitch att, loads the blades.


I probably shouldnt post this, but it mite just help sumwhere.
If you find youv 'zoomed' too far, and you now have 0 or neg AS, chop the power instantly and shove the stick forward, BUT, only till the machine is level. Hold it level till the rotors catch up, then, and only then, drop the nose and ease the power on to regain AS.

I mite regret postn this, but these bloody [ unspectacular] zoom climbs seem to be the flavour amongest the USA gyro nuts. :(
 
I hope everyone understands that Birdy's advice above is good ONLY when you have NO airspeed. Shoving the stick fwd does not unload the rotor when you have no airspeed, but it does when you do have airspeed. Therefore, DO NOT shove the stick fwd at the top of a zoom if you are still climbing with positive airspeed, or you WILL unload the rotors and may end up like the subject pilot of this thread.:sad:

Birdy - I had to add this disclaimer to your post.:wave:

Udi
 
Douglas Riley said:
I'm assuming that you start your "zoom" climb with more than cruise airspeed. You therefore start the maneuver by using the aircraft's kinetic energy as extra thrust (or impulse). This produces a rate of climb greater than the rate that you could obtain using only engine power.

As you climb, you are consuming your kinetic energy (by converting it into other forms). Therefore, the gyro's airspeed will be dropping during the zoom.

Start a bank as the airspeed reaches normal cruise. IOW, perform a climbing turn rather than a straight-ahead zoom to very low airspeed.

If you fail to do this, there is a chance that rotor AOA will reach a very low value as the zoom progresses. If the gyro still has some upward momentum, full power but little airspeed, you'll shed RRPM very quickly. You simply won't be shoving much air through your rotor to keep it spinning.

Turning, OTOH, requires you to increase rotor AOA and thereby prevents RRPM loss.
Click to expand...

I have to agree once more with you and you are absolutely right.


I remember once Dr. Bensen said.
Another potentially lethal combination of zero negative “g” conditions may occur to even more experienced pilots with sharp pull-ups.
What actually happens, the pilot usually opens the throttle wide-open to obtain maximum airspeed and then ….. when he is abreast with the spectators, he pulls back on the stick and initiates a sharp pullup. The gyro does not nose up in a climb like an airplane, but climbs in nearly level attitude. If the pilot pushes (moves)= I use this word to my students= the stick forward when the airspeed slows down to cruising speed and as Doug Rilley mentioned here start a bank no problem is encountered.
But if the pilot continues to climb and allows the airspeed to decay further you feel like an upgust and is produced by the accelerated to a higher RPM rotors from the increased “g” load.This extra lift balloons the machine up at decreased speed WITHOUT ANY COMMAND from the pilots and that’s a worning.. This second upgust should be a signal to the pilot because the rotors are still tilted to the rear, and the increase in lift is accomplanied by the increased in drag. When the airflow is interrupted during this maneuver, the rotors will slow down and…………..
Giorgos
 
Giorgios, I'm sure you recognize that there are some things in Dr. B's description that should NOT happen in a stable gyro:

The gyro should not climb in a level position, and there should not be a bump "up" late in the climb (the "bump," if any, will happen at the start of the maneuver). These are symptoms of some degree of G-instability or angle-of-attack instability.

A stable gyro will point in the direction it is travelling; the nose will point up if the gyro is climbing and will level out gently as the climb decays. A gyro with poor airframe stability will tend to experience exaggerated frame rotations when RRPM is high and (the rotor is loaded), so that overcontrol is more likely than usual. Tthis is caused by the extra rotor thrust and the consequent extra control authority.

Even in a G-stable gyro, however, loss of RRPM at the top of this maneuver is still a hazard.
 
Good point Doug. In a zoom climb where one hauls back on the stick to trade excess airspeed for quick altitude, the RTV moves forward considerably and as the airframe pitches nose up, one can easily "stand on the prop". This condition, if not managed properly, can deteriorate into a nasty situation. A timely power reduction will get you back in good shape.:yo:
 
Yes, a timely power reduction will do it, IF managed very carefully. However, in a machine that's marginally stable or plain unstable, cutting power (while the RTV is forward of CG) will cause the nose to RISE. If power was high and is cut a lot, while RRPM is also still high, the nose-up rotation is apt to be MORE than the pilot wants or expects. IOW, the aircraft develops a mind of its own, and the pilot may disagree with what the aircraft wants to do.

Terminating the zoom by banking instead of either nosing over or cutting power is the least "tricky" escape from a zoom.

Pete, I imagine you know the REALLY tricky version, the one that can bite hard, from your prior association with that disreputable crew in Florida.
 
Terminating the zoom by banking instead of either nosing over or cutting power is the least "tricky" escape from a zoom.
Click to expand...

I agree.

Pete, I imagine you know the REALLY tricky version, the one that can bite hard, from your prior association with that disreputable crew in Florida.
Click to expand...

Doug, believe me, I was very careful to avoid even mentioning that.
I often have problems on this forum when a subject arises that brings to mind certain "interesting" manouvers that were almost second nature to "the wild bunch", and I have to say "whoa, too many innocent eyes are reading". ;) I hope to never influence anyone to try anything outside their known envelope, or too close to the "ragged edge". Just to actually fly something you built yourself in a shed should be exciting enough!:D
 
How in the hell does Jim Vanek accomplish rolls and loops in a gyro?:flame:
 
Pete,

If you and several others (you know) have done loops and rolls then it sounds to me like there should not be this incredible taboo that no one should ever try acrobatics in a gyroplane. It is more properly a matter of understanding the issues involved, having equipment capable of the maneuver and having the proper knowledge and training so you don't kill yourself.

If that is right, then it seems a lot smarter to me to have someone that understands the issues, teaching those that want to know. Instead, today we have a video that shows Jim doing it over and over and makes it look so neat, with a caveat that no one else should ever try this themself. So those adventurous souls with more testosterone than brains are left to try to figure it out for themselves (which has got to have a pretty high likelihood of failure). And Gyroplanes end up with a worse safety record than they deserve.

Why not just take the mystery out of it and say if you want to try acrobatic maneuvers (like loops, rolls or zoom climbs) in a Gyro you need to understand it is very dangerous, you need a minimum of a machine that has the following qualities.... and you need to take a minimum of X hours of training from someone qualified to teach you what you need to know.

That makes a lot more sense to me.

Gyro Doug
 
I presume Pete is referring to hammerhead turns.

Do a zoom climb until the gyro is standing on its tail at near zero airspeed, kick it around with prop blast on the rudder until it’s pointing straight down and descends by the same path that it came. That’s a trick that was taught to us Floridians by a Georgian, Jerry (or Gerry) Pless.

I quit after I had installed a rotor tach that halfway worked and saw how slow the rotor was.

Gary Yanson related the story of viewing the ground through his rotor.

Quite a few years later Lloyd Poston was entertaining the crowd at Okeechobee by performing a sequence of hammerheads with a flight path that looked like a giant “U” when a noise that sounded like a shotgun going off was made by his rotor –Lycoming 0235, pod made from drop tank and 28 ft. Hughes OH-6 blades- The stick was snatched out of his hands but he managed to get the throttle shut and recovered via a vertical sink. That incident pretty much cured Lloyd of hammerheads.

A slow rotor does not flail around if it’s unloaded and not precessing. That was the secret of the Cartercopter with unloaded rotor running at mu greater than 1, meaning the wind over the retreating blade is tail first. Such a rotor will idle without inflow for the same reason a cup type anemometer turns; the drag of a tail first rotor blade is much higher than a nose first blade. But its plane of rotation must be tilted very, very slowly.

It is dumb to deliberately unload the rotor but the double jeopardy comes from an airframe that has that has major offset moments; HTL, low cabin, uncompensated propeller torque etc.
 
Airplanes are better suited for aerobatics. When you can do a barrel roll in an airplane, and your passenger doesn't spill his glass of water., then you've got it right. If you want do do that in a gyro, I just wonder why?

Phil
 
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