Flying behind the power cure

thomasant

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Hi David, it appears to me that your speed between 105 (end of green arc or VNO) and 115 mph is the critical speed range (yellow portion of the ASI). Machine can still climb in this range.

I feel that each machine has a specific vne, even though the manufacturer specifies it due to the different total drag that is present due to the build characteristics of each machine.

The graph that I posted is not gyroplane specific and the speeds can vary depending on the particular machine.
 

Vance

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Anthony:
Do I understand this correctly?


Once again, I must have a Dumbinator!
With two fat boys last year at Bensen Days; at WOT my Domiator was showing an IAS of 115 mph; to slow it down, I initiated an enroute climb of a few hundred fpm. This slowed me back to VNE of 105 and an IAS of 105. BUT it was ASCENDING not Descending.
and for slow flight; watch my Gopro vid and explain this:
https://youtu.be/XVLfGkosyFk

I must explain: last year my carb jetting was not happy and at 1/2 to 3/4 throttle settings, my EGT's were going through the roof. The only way to cool them down was to open it up to WOT and they would instantly cool back to the 1075 to 1100 range.

In my opinion low altitude is not the best place to explore exceeding Vne.

In my opinion exploring speeds beyond Vne should not be done with a passenger.

Vne is never exceed speed and has to do with how fast the aircraft is controllable.

Vne is unrelated to how fast the aircraft will go.

Vh is maximum speed in level flight at maximum continuous power.

I feel a zoom climb is trading air speed for climb and does not require excess power to climb.
 

birdy

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The speed below 20 (Minimum speed for level flight at full throttle) is where the pilots crash on take off.

Zactly.
Nice clear water.
 

PW_Plack

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Vne is never exceed speed and has to do with how fast the aircraft is controllable...Vne is unrelated to how fast the aircraft will go.

Vne may also be specified based on the limits of the aircraft's structural integrity.
 

bryancobb

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Vne may also be specified based on the limits of the aircraft's structural integrity.

In a lot of circumstances, helicopters` limit on max speed is determined by the onset of retreatinq blade stall.

The rotor of a qyro is self-requlatinq and the blade twist alonq its span is either zero or in the opposite direction of a helicopter (wash-in).

At first qlance, a qyro looks like it would be much more susceptible to retreatinq blade stall as you fly faster and faster. For the experts on the forum, let me hear the ``sales-pitch``as to why retreatinq blade stall has nothinq to do with qyro VNE.
 

Vance

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In a lot of circumstances, helicopters` limit on max speed is determined by the onset of retreatinq blade stall.

The rotor of a qyro is self-requlatinq and the blade twist alonq its span is either zero or in the opposite direction of a helicopter (wash-in).

At first qlance, a qyro looks like it would be much more susceptible to retreatinq blade stall as you fly faster and faster. For the experts on the forum, let me hear the ``sales-pitch``as to why retreatinq blade stall has nothinq to do with qyro VNE.

There is no “sales pitch” Bryan.

It is a simple fact that most gyroplanes do not have enough power to have a problem with retreating blade stall even in a descent.

I have not encountered a problem with retreating blade stall in any of the gyroplanes I have flown.
 

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bryancobb

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Sales Pitch

Sales Pitch

There is no “sales pitch” Bryan.

It is a simple fact that most gyroplanes do not have enough power to encounter retreating blade stall even in a descent.

I have not encountered retreating blade stall in any of the gyroplanes I have flown.

When I asked for a sales pitch...I mean ...present the aerodynamic explanation of how and why the retreatinq blade of a qyro can never exceed its critical anqle of attack at the machine`s upper end of its speed ranqe.

Explain what`s qoinq on...anqle of attack-wise...alonq the retreatinq blade, includinq the rotational relative wind, airspeed relative wind, flappinq relative wind, and climb/descent relative wind and the sum of all these.

What keeps the aft-qoinq blade from exceedinq 18 deq. plus/minus at hiqh speed?
 

C. Beaty

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The rotor of a helicopter begins stalling at the tip of the retreating blade, an abrupt occurrence.

The rotor of a gyro begins stalling at the root end of the retreating blade and moves outward with increasing airspeed, a gradual occurrence.

As the stall of a gyro blade gradually moves outward, the cyclic “flapping” angle gradually increases, necessitating forward movement of the cyclic stick. The forward stop is reached long before total stall.

Back in the day when people were inquisitive about such things, numerous individuals adjusted the pitch of their rotor blades to very high incidence settings and found in such cases that the forward stop would be reached at 20 mph or so and the gyro would refuse to go any faster; it would simply climb with an increase in power.

There’s discussion on the forum of this behavior from a number of years ago if someone wants to hunt for it.
 

Gyro28866

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Vance:
On the flight I mentioned, I was NOT exploring VNE; but rather trying to keep the EGT's from melting my pistons. The only way to cool it down was at WOT. At WOT and maintaining straight and level, I knew the airspeed was pretty high. There was still forward movement available to the stick, and it was very stable feeling. When I noticed that the airspeed was beyond the "red" mark on my ASI, I initiated a very gradual enroute climb to slow it down, rather than reducing throttle which would over temp the engine.

Also; my post was aimed at John. In the video, my ASI was indicating a very low airspeed during slow flight while maintaining altitude. Watch the video and observe the ASI and ALT; to see what I mean. My Dominator will slow fly and seem to defy gravity.
 

WaspAir

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Vne on the A&S 18A (which varies with weight) corresponds with the speed at which some unpleasant vibration from retreating blade stall is felt. I don't have the certification documents to check, but I'll bet it's the reason for setting Vne on that aircraft. The stick is not at the forward stop in that condition. An STC for collective pitch trim was developed by Don Farrington to permit higher rpm at low weights and delay the onset; I find it handy when flying with a light load.

Vne on the McCulloch J-2 corresponds to the speed at which the windshield flexes inward far enough to touch the back of the compass housing. That's a "structural" issue, not a power limitation or rotor behavior issue.
 
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Vance

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A correction.

A correction.

There is no “sales pitch” Bryan.

It is a simple fact that most gyroplanes do not have enough power to encounter retreating blade stall even in a descent.

I have not encountered retreating blade stall in any of the gyroplanes I have flown.

I should have written that gyroplanes don’t have enough power to encounter a problem with retreating blade stall even in a descent.

There is a stalled region in of a gyroplane rotor in normal flight.

I have not encountered a problem with retreating blade stall in any gyroplane I have flown.
 

Kevin_Richey

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Slow flight in a gyroplane

Slow flight in a gyroplane

...Back in the day when people were inquisitive about such things, numerous individuals adjusted the pitch of their rotor blades to very high incidence settings and found in such cases that the forward stop would be reached at 20 mph or so and the gyro would refuse to go any faster; it would simply climb with an increase in power...

Chuck: When you & others were doing this experimenting w/ increasing the pitch of the rotorblades to the limit possible, what approximately was the airspeed @ liftoff for the single-seat Bensen?
Did it also take a bit of flight to build airspeed like a usual short-field takeoff does?
At what point did too much pitch make it impossible to pre-rotate the rotors?
 

C. Beaty

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Kevin, this tinkering with high rotor blade pitch settings was done in the late 1960s with very little instrumentation.

The Bensen metal blades were cranked up as high as the pitch adjustment would allow but I don’t know the angles and I didn’t have a rotor tach that meant anything.

A lot of other people did the same with their Rotordyne, Rotorhawk and Stanzee blades with similar results. I recall Pete Johnson mentioning here on the forum having done the same thing with his Rotordyne blades: similar result.

No one ever mentioned excess vibration; everyone said that with the stick jammed up against the forward stop, the top speed was 20-25 mph and if more power was squeezed on, the gyro would climb but airspeed wouldn’t increase. I recall someone saying it felt like the gyro screwed itself up and down as throttle position was changed.

I don’t recall anything unusual about takeoff roll or liftoff speed.

The behavior of the A&S 18A rotor doesn’t correlate with a Bensen rotor because of the 18A’s flap-pitch coupling (delta-3) which suppresses cyclic flapping. With the suppression of cyclic flapping, the stick doesn't move forward at the normal rate.
 
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