rotor flap

captgyro

Newbie
I have 9 hours of dual time in an MTO sport, had to take a break to go back to work, in the Atlantic, off the coast of Africa. However, I do not feel that I have my head totally wrapped around the issue of rotor flap, exactly what it is, what it causes, how to avoid it and how to recover from it. Any input would be greatly appreciated. Stephen
 

captgyro

Newbie
sadly I do not have access to u-tube here, not able to down load videos until I return to the states in April. BTW, already ordered a sport, hoping to have it by May.
 

birdy

Newbie
This request for infomation is very disturbing.
Wot the hell are you payn your instructer for?
Id be askn for my money back. :(
 

gd5362

Newbie
He's stuck on a platform in the middle of the wet and just looking for some additional education. Somebody help out the new guy out!
Oh, and welcome captgyro!
 

scottessex

Sling-Wing Pilot
I would get with an old school instructor and get some basics and then go back to the euro gyro instructor.
If I am not mistaken, I may be, but the euro gyros prerotate to 200 rrpm before they move, so the rotor management skills are not taught, might be why there are so many roll overs in these models...
Linked nose wheels and no tail wheels....
 

MadMuz

Newbie
but the euro gyros prerotate to 200 rrpm before they move, so the rotor management skills are not taught, might be why there are so many roll overs in these models...
Linked nose wheels and no tail wheels....
But other than that Scott, they are pretty good machines? (other than very expensive and a bit heavy)
 

turbo

Newbie
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. [Figure 20-2]

To avoid the onset of blade flap, always taxi the gyroplane at slow speeds when the rotor system is at low r.p.m. Consideration must also be given to wind speed and direction. If taxiing into a 10-knot headwind, for example, the airflow through the rotor will be 10 knots faster than the forward speed of the gyroplane, so the taxi speed should be adjusted accordingly. When prerotating the rotor by taxiing with the rotor disc tilted aft, allow the rotor to accelerate slowly and smoothly. In the event blade flap is encountered, apply forward cyclic to reduce the rotor disc angle and slow the gyroplane by reducing throttle and applying the brakes, if needed. [Figure 20-3]

this may help till you get back to the states. there is no bad question but there are some bad responses. come on guys.
 

Texasautogyro

Gyro Master Instructor
Scott I was taught that at first. An autogyro brand gyro can be spun to about 140-150 then have the stick full back while you gradually build to 200 with airflow and add throttle to take off. Most autogyro CFIs do not teach this and only a few really discuss rotor flap and it's problems in detail. This was taught to me by Ron Menzie and I have always taught it with ground rotor management and made the video to help visualize the dynamics of it. Pre rotating to 200 or more I only use for short field it's very hard on equipment and towered airports do not like that procedure. The operations manual does not show my method. But that does not mean it is not a very well thought out technique and procedure.
In this case this gentleman is being trained by someone else and I hope they help cover what he needs when he comes back from off the rig.
 

Mike484

AR-1 🇺🇸
Most autogyro CFIs do not teach this and only a few really discuss rotor flap and it's problems in detail.
This is a great example of why some of the newer CFIs that don't understand home built machines are a danger the home built community.
 

eddie

RAF, turbo subaru 230hp
Gary Neal was my instructor,he probably spent nearly as much time on good rotor

management as flying,he was obsessive with rotor management.I can't thank him

enough for that.I came back from S.C. and never gave the possibility of mismanagement

another thought,it is second nature to me.

best regards,eddie.....
 

Texasautogyro

Gyro Master Instructor
Eddie you are lucky. I spend close to two or more hours on it per student. Some get it and say it's more important then flying. Others say it's a waste of time. When I hear it's a waste if time we stop and start the lesson over so the get it drilled in there head that it's a big deal to get right. Knowing how to handle that spinning blade on or off ground can help you understand that the blade flys in both places. If you stop flying the blade before it stops producing lift you will have a problem.

This is another link to ground rotor management in the MTO. It basic but helps get the point across.
http://youtu.be/JD_PuihilIQ
 

captgyro

Newbie
rotor flap

1st off I want to thank Turbo for his response to my question. I am being trained by one who I consider an excellent instructor. He previously taught both myself and my wife on PPC's. I have read, while on my boat, a lot and realized that this subject was one of the most important regarding safety and wanted to get as much info as I could. His response reaffirmed the training I have had. As a former Sky Diving instructor, and a pretty good one I believe, I never stopped asking opinions from other jumpers. One can not have too much information. Hope to meet some of you at Benson Days.

Stephen

"One does not achieve true wisdom until he realizes just how ignorant he really is" Socrates
 

loftus

Active Member
There are two excellent books on 'eurogyro' flying by Phil Harwood. The Gyrocopter Pilot's Handbook, and Flying a New Generation Gyrocopter. The Handbook is a full sequenced training syllabus that I can recommend to everyone. The other book is more suited for someone transitioning from fixed wing. I read both over and over during my training and refer to them over and over from time to time. Certainly there may be differences of opinion about some of the details in the books, but I think every gyro CFI who trains new eurogyro pilots should make these required reading for all their students, particularly as there is no CFI that I have met in the US who trains eurogyro students who provides a complete training syllabus to their students. I believe Ron Menzie does, but even his syllabus does not appear to be specific for Eurogyros. The books are more comprehensive than any gyro flying manuals or books that I have seen. Autogyro USA I believe does sell the books, but I think they should promote them more. No need to recreate the wheel - these are two excellent well written books.
 

Vance

Gyroplane CFI
I have 9 hours of dual time in an MTO sport, had to take a break to go back to work, in the Atlantic, off the coast of Africa. However, I do not feel that I have my head totally wrapped around the issue of rotor flap, exactly what it is, what it causes, how to avoid it and how to recover from it. Any input would be greatly appreciated. Stephen
I have some experience flying a Cavalon (Puff) which has a very similar pre-rotator and rotor system to an MTO Stephen.

In my opinion you are not likely to flap the blades if you carefully follow the procedures in the Pilot’s Operating Handbook.

It is not fool proof because people keep finding different ways to be foolish.

In my opinion a blade flaps the same way a wing stalls; too high an angle of attack.

In my opinion as long as you have rotor rpm above about 220 you are not likely to flap the blades unless you try to force a takeoff.

I have tried pre-rotating to less than 140 rotor rpm just to see how it would work out. Take off just took a little longer and I did not come full back with the cyclic until I had reached 180 rotor rpm.

I also fly a gyroplane (The Predator) with a prerotator that won’t get the blades much over 100 rpm without the help of the wind. I have only flapped a blade once and it was pretty much of a nonevent.

I was trying to rush a takeoff from 65 rotor rpm and a blade hit the rudder. The fix at the moment was to get the stick full forward and that was it. New starter motor for the pre-rotator and straighten out the bend in the rudder (tube and fabric.

The CFI I used to learn to fly the Cavalon was Michael Burton and he taught me to take off like it says in the POH. As far as I know he has never flapped the blades in any of the aircraft from AutoGyro.

I have seen people do the prescribed takeoff in an MTO, Cavalon and Calidus badly without incident.

At the risk of insulting Ed (Turbo) in my opinion as long as your disk is flat (cyclic forward) you are not likely to encounter blade flap from taxiing to fast. There are plenty of other reasons not to taxi too fast.

Good luck with your gyroplane adventure Stephen.

Regards, Vance
 

birdy

Newbie
All true Vance, cept the caues bit.
Rotor flap is caused by excessive lift differential between advancing and retreating blades, and this can happen at any rrpm, without an airodynamic stall.
You can be stationary on the ground with the stick forward and 100 rrpm and still flap the blads, if the wind is strong enuf. ( unless your full forward puts the disc to -3*.)
Naturaly, the higher the disc aoa, the stronger inflow wind and lower the rrpm, the more likely it is to flap.
 

Vance

Gyroplane CFI
All true Vance, cept the caues bit.
Rotor flap is caused by excessive lift differential between advancing and retreating blades, and this can happen at any rrpm, without an airodynamic stall.
You can be stationary on the ground with the stick forward and 100 rrpm and still flap the blads, if the wind is strong enuf. ( unless your full forward puts the disc to -3*.)
Naturaly, the higher the disc aoa, the stronger inflow wind and lower the rrpm, the more likely it is to flap.
I suspect Stephen is asking about a blade that diverges from the intended flight path rather than the flapping caused by dissymmetry of lift from forward flight in a rotorcraft.

You could be right David and I misunderstood the question or I am misunderstanding your answer.

My impression is; when a blade hits something it is because one blade is flying producing lift and the other is stalled because the critical angle of attack of the airfoil has been exceeded.

It is my opinion that a higher disk angle of attack allows the blade to stall at a higher rotor rpm and a lower disk angle of attack allows the rotor to turn slower without stalling a blade.

Regards, Vance
 

Jean Claude

Junior Member
Birdy,
Yes, the cause of the stops hits is the excessive forward speed difference and yes also, as said Vance, the cause is the stall of the retreating blade.
The lift differences produce a beat angle. The flapping angle produces a difference in angle of attack until the lift difference disappears. When the speed difference is too large, the flapping angle brings too much angle on the retreating blade and he stalls. The lift difference can then no longer disappear and the stops are hit.

It is often said that it is the lack of centrifugal force allows stops hits. This is wrong. The centrifugal force has no role in this. Heavy blades will not remove the problem.
 

MadMuz

Newbie
That is true JC, I have only had 2 slow rpm flaps, both when hand starting rotors on windy days, when the wind speed is the same as if you are taxying too fast for the rotors, but I was actually stationary at the time, the wind was just too fast. The flap, or what I was told later (I didn't know at the time what was going on) was often called 'hinging'. The flapping/hinging showed up as all of a sudden the rotor passing at the front is very high and the joystick started to go to the right and then proceed to go around in circles like stirring a pot of stew.... the flap stopped when I pushed the stick forward and held it there (I was still not moving)

I stopped the rotors and checked them, there was no problem, I had plenty of rotor-tail clearance, I just started them by pushing them as fast as I possibly could with the stick forward, then introduced them to the wind slowly until they got going. The other time was also no damage, I did just taxy too fast, but pushing the stick forward and holding it forward stopped that.

Hand turning rotors, on a machine I fitted a rotor tach (cycle computer) showed I could hand spin rotors to about 35rpm, that is why I like to use a simple electric prerotator to get the rotors up to 70-80 rpm or a bit more, that reduces the possibility of these low speed flapping situations.

I have never had a high speed flap, either by unknown skill or good luck, so I don't really know anything about high speed (rpm) flapping, but it can't be good :yo:
 
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