AR-1 N57AR - Texas - 20.8.23

and APPLY BRAKES to come to a stop
Hmmm. I guess. In my experience - and I just had a rotor flap on takeoff last month when I swapped out my Warp Drive for a NR/Luga prop and had the pitch too aggressive - pushing the stick forward and pulling throttle at the same time back to idle does the trick, then as soon as the flap ceases carefully bring the rotor back to catch the wind while carefully adding back throttle to get the rotor to "grab" again, then continue to smoothly add power and bring the rotor full back until TO then let 'er rip with WOT and normal stick push. I have never used brakes nor come to a full stop, never been trained to do so, and never would. Once the flap is eliminated, there's no point in coming to a full stop and letting the rotor decay. But perhaps this isn't such a good idea for others?? I don't really know. I just know what works for me with a tandem, 28' disk and 140 HP.

Funny story: I trashed a set of 23' RFD blades on my Honey Bee in front of a big crowd, and replaced them with 12-footers on a 2' bar = 26 ft Dragon Wings on a stick gyro that weighed just 340 lbs! The first time I broke ground the thing flapped, vibrated and shook badly, and faced with the choice in the mooment I decided to push through it and continue rather than try to abort and risk making it worse. It worked. From then on, I was prepared for the flap to come and virtually every time I took off that over-sized 26' disk flapped at the moment I broke ground, then smoothed right out and flew like a champ. Landing was a real joy, it floated forever.

My point is that although blade flap is very bad juju it isn't necessarily the end of the world.
 
Hmmm. I guess. In my experience - and I just had a rotor flap on takeoff last month when I swapped out my Warp Drive for a NR/Luga prop and had the pitch too aggressive - pushing the stick forward and pulling throttle at the same time back to idle does the trick, then as soon as the flap ceases carefully bring the rotor back to catch the wind while carefully adding back throttle to get the rotor to "grab" again, then continue to smoothly add power and bring the rotor full back until TO then let 'er rip with WOT and normal stick push. I have never used brakes nor come to a full stop, never been trained to do so, and never would. Once the flap is eliminated, there's no point in coming to a full stop and letting the rotor decay. But perhaps this isn't such a good idea for others?? I don't really know. I just know what works for me with a tandem, 28' disk and 140 HP.
My point is that although blade flap is very bad juju it isn't necessarily the end of the world.
When a learner flaps the blades enough to shake the cyclic; I recommend immediately getting the cyclic full forward, reducing the throttle to idle and applying the brakes.

I feel a taxi back, a careful inspection of the aircraft, a review of the pre-rotation and takeoff procedures are in order before the next takeoff attempt.
 
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Vance - makes perfect sense for students and new pilots, a complete "RESET".
 
Do some rotors flap easier than others? I had an air command with 24 ft Dragon Wings. They were notorious for flapping. I hate to admit this but one time they flapped enough to hit the ground and also the prop which cut one rotor blade almost in half just beyond the aluminum bar inside. I didn't know it and lifted off. I flew it around the pattern and landed. I almost fainted when I saw what had happened. Yes, totally my fault. But it held together somehow. I learned to get the rotors up to speed slowly to avoid flapping. That said, I never had this happen in either of my two Sport Copters.
 
Do some rotors flap easier than others? I had an air command with 24 ft Dragon Wings. They were notorious for flapping.
Some rotors flap more easily than others. This depends on the pitch setting, the rotational inertia, and the stall angle of the airfoil used.
I guess, DW rotors can flap more easily due to more pitched setting, and don't forget that a greater rotor has more rotational inertia which limits its rrpm growth during the take-off run.
 
Salut Jean Claude

Dans ta phrase --- and don't forget that a greater rotor has more rotational inertia

l'emploi du mot --- greater--- pour toi est tu pour vouloir dire meilleur ou plus grand ?

Merci
 
Plus grand, je pense.
The Brits often use "great" simply to mean large, e.g. "Will you look at that great queue!" (long line). We North Americans rarely use it in that sense.
 
Do some rotors flap easier than others? I had an air command with 24 ft Dragon Wings. They were notorious for flapping. I hate to admit this but one time they flapped enough to hit the ground and also the prop which cut one rotor blade almost in half just beyond the aluminum bar inside. I didn't know it and lifted off. I flew it around the pattern and landed. I almost fainted when I saw what had happened. Yes, totally my fault. But it held together somehow. I learned to get the rotors up to speed slowly to avoid flapping. That said, I never had this happen in either of my two Sport Copters.
ABSOLUTELY! I always described Dragon Wings as spaghetti noddles, which pissed some folks off and sent howls through RF, so I devised the following test to prove my case about 15 years ago and posted the results here.

Tie the front blade down. Grab a fish scale, pull down on the end of the rear blade and measure the deflection for a given pull on the fish scale. It's been years but I think I measured 2x - 3x as much deflection of the stiffest 28' blades, composite Sky Wheels, compared with the floopyist blades, Dragon Wings.

Extruded blades are going to be somewhere in the middle with their cross-sectional bracing that stiffens them up considerably, though I have not tested them personally.

Once they get to spinning up to TO speed they stiffen up obviously, but regardless there is still a significant difference in stiffness and resistance to flap due to basic construction and materials as well as rotating mass/ weight on the outer half of the blades.

Your account of damage speaks volumes to Vance's post the other day about the necessity for novice pilots to come to a full stop following a blade flap, and return to the hangar for proper damage inspection.
 
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ABSOLUTELY! I always described Dragon Wings as spaghetti noddles, which pissed some folks off and sent howls through RF, so I devised the following test to prove my case about 15 years ago and posted the results here.

Tie the front blade down. Grab a fish scale, pull down on the end of the rear blade and measure the deflection for a given pull on the fish scale. It's been years but I think I measured 2x - 3x as much deflection of the stiffest 28' blades, composite Sky Wheels, compared with the floopyist blades, Dragon Wings.

Extruded blades are going to be somewhere in the middle with their cross-sectional bracing that stiffens them up considerably, though I have not tested them personally.

Once they get to spinning up to TO speed they stiffen up obviously, but regardless there is still a significant difference in stiffness and resistance to flap due to basic construction and materials as well as rotating mass/ weight on the outer half of the blades.

Your account of damage speaks volumes to Vance's post the other day about the necessity for novice pilots to come to a full stop following a blade flap, and return to the hangar for proper damage inspection.
In my opinion the stiffness of the rotor blade has little to do with what people are referring to as flapping the blades.

I feel the retreating blade stalling is what causes the divergence that exceeds the range of the flap stops.

Dragon Wings were twisted for better efficiency on a gyroplane and some feel that made the retreating blade stall more suddenly.

In my opinion proper pre-rotation and takeoff technique is to have enough rotor rpm for the indicated air speed.
 
In my opinion the stiffness of the rotor blade has little to do with what people are referring to as flapping the blades.

I feel the retreating blade stalling is what causes the divergence that exceeds the range of the flap stops.

Dragon Wings were twisted for better efficiency on a gyroplane and some feel that made the retreating blade stall more suddenly.

In my opinion proper pre-rotation and takeoff technique is to have enough rotor rpm for the indicated air speed.
OH I totally agree Vance. It was my stupid takeoff technique every time. I did learn the hard way and had to purchase a new set. But am very impessed with the Sport Copter rotors. Never came close to flapping. Not saying they won't, just never did on mine.
 
In my opinion the stiffness of the rotor blade has little to do with what people are referring to as flapping the blades.

I feel the retreating blade stalling is what causes the divergence that exceeds the range of the flap stops.

The more flexible the blade the lower its resonant frequency, and the greater that wave's amplitude. Resonance disrupts laminar airflow over the airfoil surface, interrupting lift.

Proof of this is in the disparity between gyrocopter take off distance from a paved RW compared to that of a grass strip, which is often doubled, whereas FW do not exhibit nearly the same difference.

The more flexible rotor blades will always flap first. This isn't about gross "bird wing" motions, its about the amplitude of airfoil surface wave harmonics disrupting laminar air flow and hence lift.


Dragon Wings were twisted for better efficiency on a gyroplane and some feel that made the retreating blade stall more suddenly.

Efficiency implies the system worked to begin with. DW twisting was a necessity.

The first set of Dragon Wings (DW) were not twisted, they were built like any other conventional rotors with 3° AOA and 3° coning at the hub bar. During testing Bill Parsons executed a banked turn, G-loading them a bit. This made the flexible blades untwist to the point that the rotors accelerated in a feedback loop increasing the untwisting, speeding RRPM, etc until the gyro fell to the ground.

From then on they were negatively twisted 3° at the tips as a pre-load compensation and flew with success.

The blade stall you refer to occurs at normal flight RRPM during landing, not at take off prior to full lifting capability. As the disk unloads at slow speed in descent and prepares to touch down the stored, sprung twist in the blades releases, doubling the drag at the tip causing a sudden loss of lift. If you're aware of and prepared for this it is no big deal, you just need to keep some throttle in it as you land, especially in variable/tricky winds.
In my opinion proper pre-rotation and takeoff technique is to have enough rotor rpm for the indicated air speed.

The correct phrase would be "proper disk loading". One must match apparent wind speed seen by the rotor blades to RRPM with throttle input in order to maintain proper disk loading. As soon as you "over-speed" the RRPM with throttle, turbulent air induces blade resonance in a feedback loop that increases the disparity in lift between advancing and retreating blades, due to insufficient RRPM to overcome apparent wind disparity.
 
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From the Gyroplane Flying Handbook:

BLADE FLAP On a gyroplane with a semi-rigid, teeter-head rotor system, blade flap may develop if too much airflow passes through the rotor system while it is operating at low r.p.m.

This is most often the result of taxiing too fast for a given rotor speed.

Unequal lift acting on the advancing and retreating blades can cause the blades to teeter to the maximum allowed by the rotor head design.

The blades then hit the teeter stops, creating a vibration that may be felt in the cyclic control. The frequency of the vibration corresponds to the speed of the rotor, with the blades hitting the stops twice during each revolution.

If the flapping is not controlled, the situation can grow worse as the blades begin to flex and bend. Because the system is operating at low r.p.m., there is not enough centrifugal force acting on the blades to keep them rigid.

The shock of hitting the teeter stops combined with uneven lift along the length of the blade causes an undulation to begin, which can increase in severity if allowed to progress. In extreme cases, a rotor blade may strike the ground or propeller.
 
For the proper pre-rotation technique follow the pilot’s operating handbook for your particular gyroplane.

In the absence of a POH for your gyroplane; most rotor systems will be relatively stable at 100 rotor rpm and capable of aerodynamic control allowing the pilot to use the wind to accelerate the rotor with a indicated air speed below 15kts.

Most gyroplane rotor systems above 180 rotor rpm will allow full throttle and with the disk tilted full aft allowing the rotor to accelerate and the nose to lift.

Once the nose tire lifts the cyclic is brought progressively forward to keep the tire near the ground until the gyroplane lifts off on her own.

If you feel a tapping in your cyclic reduce power, bring the cyclic full forward, stop, taxi back and reassess your takeoff technique.
 
This discussion has gone completely incorrect. Rotor blade flap is an aerodynamic phenomenon. Your retreating blade reaches its critical angle of attack and stalls in a failed attempt to equalize lift. Flexible blade has very little to do with this. At around 100 to 120 rotor RPM, the flexibility is gone and the whole thing is ruled by centrifugal force. No gyroplane pilot should be on takeoff roll moving when your rotor RPM are that low. Modern gyroplanes will reach easily in excess of 180 rotor RPM via pre-rotator standing still.
 
This discussion has gone completely incorrect. Rotor blade flap is an aerodynamic phenomenon. Your retreating blade reaches its critical angle of attack and stalls in a failed attempt to equalize lift. Flexible blade has very little to do with this. At around 100 to 120 rotor RPM, the flexibility is gone and the whole thing is ruled by centrifugal force. No gyroplane pilot should be on takeoff roll moving when your rotor RPM are that low. Modern gyroplanes will reach easily in excess of 180 rotor RPM via pre-rotator standing still.
Clearly you are from the modern gyro pilot camp that has possibly not been taught to bring the rotors up from hand spinning.
Your statement I think should read, " No gyroplane pilot should be on a takeoff roll moving, unless they can get rotors up from RRPM lower than 100".
Not here to argue about it though, never ending argument.

wolfy
 
Clearly you are from the modern gyro pilot camp that has possibly not been taught to bring the rotors up from hand spinning.
Your statement I think should read, " No gyroplane pilot should be on a takeoff roll moving, unless they can get rotors up from RRPM lower than 100".
Not here to argue about it though, never ending argument.

wolfy

Yes I am. I am not going to try and bring up 87 pound rotor set by standing in the back seat and trying to spin them up by hand and then jump off into the front seat, sit and try and taxi.
The average age of customers is over 65. They aren’t hand spinning nothing. We have to be practical. These guys can barely squeeze the orerotation actuation handle for a minute. Hand spinning is out of the question for them.
 
Yes I am. I am not going to try and bring up 87 pound rotor set by standing in the back seat and trying to spin them up by hand and then jump off into the front seat, sit and try and taxi.
The average age of customers is over 65. They aren’t hand spinning nothing. We have to be practical. These guys can barely squeeze the orerotation actuation handle for a minute. Hand spinning is out of the question for them.

It wasn't about hand spinning. You have missed the point.
 
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