#### Abid

##### AR-1 gyro manufacturer
People seem to lack details of why Blade Sailing happens and what is the math and measurement behind it. Its not mythology or magic.

I am taking the liberty of copying and posting a post by Mike Goodrich from an unrelated thread which is all about measurements of just this phenomenon. The context was a discussion with Jean Claude who uses Discrete Math he has programmed in Excel sheet but also Kolibiri has done some calculations programmed in some software with logic coming from papers from NASA research. These things are complex in details and not in the span of flight instructors or pilots but we should definitely understand as to where these POH recommendations, numbers, logic come from and also mainly why. Here is the quote or post from Mike while he was developing GWS (Gyroplane Warning System) which simplifies the algorithm with approximations and uses the main factors to predict different flapping and bad behavior. I hope Mike will answer people's questions here.

My intention is not to dig down and explain what goes into everything that happens and then what factors are so minute that they can be ignored to simplify and come up with a simple formula for a given type of rotor based simply on rotational speed, forward airspeed and radius or diameter of the rotor and static pressure and outside air temp. I think that is beyond the scope of operations persons. Intention is simply to give you an idea that its not magic and in fact a firmed up mathematical relationship between the listed factors and that drives the recommendations in a POH.

Note the RV curve in the bottom graph starting at 150 RRPM pre-rotation and then full throttle movement forward with a 912 powered 2 seater gyroplane (ELA). (R = Rotor RPM, V = Velocity in KPH). Even at 150 Rotor RPM it shows the amber alarm was set off which means you are 4 seconds away from blade sailing or flapping and it got close to red alarm which means in GWS that you are 2 seconds away from actual blade sailing/flapping and the solid black line is you flapping or sailing the blade. So starting at 150 RRPM with a 2 seat modern gyroplane with 912ULS power, you are basically 3 seconds away from disaster. This was for a 8.7 meter rotor.
AR-1 uses as standard 8.6 meter rotor. AR-1 POH recommendation that you don't do takeoff roll till you go at least 160 RRPM. Its pretty right on. Actually the recommended RRPM is 180-200 but you'd be safe at 160 RRPM with little care. Below that you better have experience nursing the blades up slowly watching RRPM trend.

If any gyroplane rated pilot or CFI cannot make sense of these graphs, its best to discuss and understand. This is where these recommended POH pre-rotation RPM come from. They don't come from someone pulling them out of their ears. Since many gyroplanes use same airfoil and similar engines, this will be very similar for Magni, AutoGyro, ELA, SilverLight and so on.

"
If (as I suspect) JC's calculations are somewhat based on the results of my testing, don't forget that I go to WOT as soon as I release the pre-rotator and bring the stick back.

If John's TO procedure is "I often advance the throttle to WOT within 25m of the start of the takeoff roll" that's half of his TO roll before he's at full throttle. This will help avoid blade flap or sailing but will extend his TO run to beyond the calculation.

Also JC's calculations are based on 2200N (500 lbf) thrust, you'd better make sure that you really have that. One of the discrepancies we found with my measurements was that I obviously wasn’t getting the thrust out of my old 1,000 hour 912S that JC assumed I was.

Plus check the stick position (into/outof wind) discussions for cross wind take offs. This will have an impact on your take off run and flapping risk.

As I said before JC's calculations are remarkably accurate but, I've learned the hard way, that if you want to fly to his limits you'd better fly to the same degree of accuracy.

Here is a graph I'm preparing for the presentation of my GWS to explain the flapping alarm to the uninitiated. I’ve modified it for your 8.5 m rotor.

For the stick back (@20°) acceleration, It translates to

Rrpm<2.5 x TAS (kph) = danger,

Rrpm>2.5 x TAS (kph) = safe

Here is the same graph with the basic alarm limits for the GWS. The actual alarms lines are not simply straight lines and are more complicated but it gives you an idea.

Here is an actual recording of a 150 Rrpm pre rotator take off with an 8.7 M rotor overlayed on the graph for that rotor. You can see that it flirted with the red alarm. You can also see that I needed to be at about 40 kph before I recovered my initial pre rotation Rrpm and about 60 kph before the rotor really started to accelerate. If this had been a downhill or a stick into Xwind TO the flat part of the curve would have been much longer and the risk of flapping much greater.

Mike G

Last edited:
I am surprised no one has asked any questions or made any comments on this. We are talking about POH and blade sailing like crazy on another thread which has drifted from its original subject and people are ready to argue about how to educate new pilots about that but when probably the best data about that subject is put out showing where it happens Nothing? Wow.

I am surprised no one has asked any questions or made any comments on this. We are talking about POH and blade sailing like crazy on another thread which has drifted from its original subject and people are ready to argue about how to educate new pilots about that but when probably the best data about that subject is put out showing where it happens Nothing? Wow.

I'm following the thread with great interest. And I feel sure that other pilots here also do...

I am surprised no one has asked any questions or made any comments on this. We are talking about POH and blade sailing like crazy on another thread which has drifted from its original subject and people are ready to argue about how to educate new pilots about that but when probably the best data about that subject is put out showing where it happens Nothing? Wow.
I love the work Mike Goodrich and Jean Claude are doing.

What you have posted is not what I would use to teach people about rotor management.

I try to keep it simple, two much air speed for the rotor rpm and control of the rotor may be lost.

The air speed can come from moving forward, wind or turbulence.

The takeoff surface can have a significant impact on rotor management.

I love the work Mike Goodrich and Jean Claude are doing.

What you have posted is not what I would use to teach people about rotor management.

I try to keep it simple, two much air speed for the rotor rpm and control of the rotor may be lost.

The air speed can come from moving forward, wind or turbulence.

The takeoff surface can have a significant impact on rotor management.

This is not to teach "rotor management" hands on. For sure that is very important as well and crucial. This is to show students why going to recommended rotor RPM is important and where does that come from. Its not just a flick of luck. To get beyond rote learning and get to the understanding, application and ideally correlation deeper level so things are committed to memory better.
This is also to show instructors what exactly is going on and what is the simplified relationship mathematically given above for TAS versus rotor RPM to get beyond myth and into knowing what it is and really how much or actually how little time there is between first signs of danger to disaster.
So this is the subject matter of ground briefing and ground school for emergency procedures and pre-rotation lesson in support of hands on training. This is fairly simple. Basically you need to know what True Airspeed (TAS) is and what is Rotor RPM, rotor disc angle (20 degrees is fairly standard in modern gyroplanes, Magni only allowing 18) and what is Retreating Blade Stall. All stuff a gyroplane pilot should know anyway.

Last edited:
I'm always interested in gyro theory, and do very much appreciate (and learn a lot from) the contributions of the experts here.
Having said that, I think that –for a safe and fast takeoff– you have to do just two things: 1) pre-rotate to the right RRPMs and 2) open the throttle and accelerate while keeping the front wheel skimming the ground. The gyro will get unstuck by itself...

I'm always interested in gyro theory, and do very much appreciate (and learn a lot from) the contributions of the experts here.
Having said that, I think that –for a safe and fast takeoff– you have to do just two things: 1) pre-rotate to the right RRPMs and 2) open the throttle and accelerate while keeping the front wheel skimming the ground. The gyro will get unstuck by itself...

Yes and now you know why it is important to get to minimum rotor RPM before moving forward with good power to get shortest takeoff distance and if your instructor starts to tell you some other RPM, you know how to process that information with knowledge and make a good decision what to use and what not to.

The problem at least in the US is there are instructors who really don't know but are good pilots themselves and when they teach they "transfer" a lot of what I term "myths" to students. So student really doesn't know. They are at the "rote" and at most the "application" level and that eventually gets them in trouble. As instructors we want the fundamentals to be understood from rote, understanding, application to correlation level of learning. An example would be takeoff on a grass field that's a bit rough. Usually you go to 180 rotor RPM but now if you have gotten to correlation level you'd know (without me your instructor telling you) to try and increase the buffer more and go to 220 RRPM and may be not start to move as fast from the get go and increase rotor RPM more before going full bore so you have a larger buffer to flap developed in case you hit some bumps that effect your rotor RPM. This process and new technique given a situation you face shows you don't just understand rotor RPM versus speed and takeoff seuqnece and procedure, you have the knowledge at correlation level which is where every instructor would like you to be for all the basics including rotor management

This also means that you will have an innate idea of why its important to have a rotor RPM gauge mainly for takeoff. You really don't need it in flight much of the time. This is to keep an eye for a trend development during takeoff roll. If you see the trend going the wrong way, you'd immediately abort takeoff. This may happen if you decided to takeoff on a runway with some quartering crosswind and had a headwind component and it switched by the time you were rolling down the runway to a steady quartering crosswind with a steady tailwind component.

Last edited:
We are taught in the UK to pre-rotate to 200, and higher, if necessary.

On my 350m private (undulating) grass strip, I try to pre-rotate to 220, and watch for RRPM > 250 and rising during the roll before committing to takeoff and full power.

Someone asked my privately how or why then Magni instructors in the US teach going to 130 RRPM and get going for takeoff.
Well first they have a procedure that keeps them safe. They don't just get going at 130 rotor RPM.
Second, their procedure is more involved and needs to be mastered but it can be. You still need to understand that moving at 130 rotor RPM with stick back slightly requires care and they have a flex shaft that they keep engaged to the engine while at this low RPM with stick slightly back so engine is driving and still accelerating rotor rpm . In gusty conditions, surely you are in more danger with this technique than other technique and need to take care.

But reality is Magni instructors in the US also do not truly get moving for takeoff till they reach 200 RRPM. Watch for example what Dayton does with a commercial gyro rated student. Pay attention to him reminding the pilot to look for 200 RRPM before he tells him we are good to go for a real takeoff run

Last edited:
With my Magni M24, I pre-rotate to 220 before releasing the brake and starting the run... That's what I was told to do by the instructor; besides it's in the POH. During the first seconds of the takeoff run, the rotor revs drop substantially, so it's safer to start with 220...

With my Magni M24, I pre-rotate to 220 before releasing the brake and starting the run... That's what I was told to do by the instructor; besides it's in the POH. During the first seconds of the takeoff run, the rotor revs drop substantially, so it's safer to start with 220...

Magni and standard AutoGyro rotors are 8.4 meters. Our standard rotor is 8.6 meters. I think ELA might be 8.5 meters now. You saw that with 8.5 meters the mathematical relationship constant is 2.5 and with 8.7 m rotor 150 is bare minimum pre-rotation needed. The larger the rotor the slower you can be. The smaller the rotor the higher you ought to be.
Rotor size makes a difference. With Magni and AutoGyro getting to 220 or at least 200 is warranted. With us 180 is warranted.

Last edited:
With my Magni M24, I pre-rotate to 220 before releasing the brake and starting the run... That's what I was told to do by the instructor; besides it's in the POH. During the first seconds of the takeoff run, the rotor revs drop substantially, so it's safer to start with 220...
Australian Magni M24C FLIGHT MANUAL.

I could not find the one for Spain

1 - ALIGNMENT - runway alignment

2 - ENGINE SPEED - set at 1.800 r.p.m.

3 - PREROTATION ENGAGING - gently operate the prerotation lever (1). Keep engine speed at 1.800 r.p.m.

At 130 r.p.m. ROTOR

4 - CONTROL STICK - Place the control stick (2) in takeoff position (rear limit stop).

5 - PREROTATION LEVER - Gently reach the limit stop while keeping a constant engine speed.

WARNING DANGER: In windy conditions, or if the payload is light, it is possible that the gyroplane will lift up onto the tail wheel. If this occurs, the prerotation should be released and the stick moved forward to balance the gyroplane on the main wheels, some engine power should be applied to prevent the gyroplane from moving backward. The rotor rpm will continue to increase. When the rotor speed is equal or greater to 200 rpm, proceed as for take off. This should be practiced with an instructor before proceeding in these conditions

6 - ENGINE r.p.m. - Gently increase the engine speed until reaching 200 r.p.m. of the rotor. (standard prerotation).

WARNING DANGER: The minimum rotor prerotation speed is 150 r.p.m. It is strictly forbidden to proceed with takeoff operations if the rotor r.p.m. is lower than the minimum value.

7 - BRAKES - release (3).

8 - RELEASE PREROTATION LEVER - once the rotor turns at 200 r.p.m., quickly release the prerotation lever

1 - THROTTLE LEVER (1) - Increase the throttle in a progressive and uniform manner. NOTE: Increasing the engine power progressively guarantees the same level of progressive attitude of the gyroplane, thus simplifying the management of this procedure.

WARNING DANGER: In order to guarantee a safe takeoff, the engine’s power must increase progressively until reaching the maximum allowed value.

WARNING: If a rotor speed of less than 200 r.p.m. is achieved during prerotation, acceleration must be gradual. Engine rpm must be increased very carefully.

2 - ALIGNMENT - use the rudder pedals (2) (right pedal) to keep the alignment on the runway.

3 - CONTROL STICK (3) - in takeoff position (rear limit stop). Once the nose wheel has lifted, move the control stick forward and balance the gyroplane on the main wheels.

WARNING: During the balancing phase, the attitude must be so that neither the nose wheel (pitch down) nor the rear wheel (pitch up) touches the ground.

Practicing of “balancing” or taxiing on tarmac runways for more than 30 minutes continuous, without flight, may cause the brakes and the wheels to overheat. This is normal; restrict these exercises to periods of less than 30 minutes continuous.

4 - TAKEOFF: A) correct the roll induced by the engine torque (stick (3) to the left); B) reach and maintain attitude so as to obtain 65 mph [55 Kn] (Best rate of climb speed).

Australian Magni M24C FLIGHT MANUAL.

I could not find the one for Spain

1 - ALIGNMENT - runway alignment

2 - ENGINE SPEED - set at 1.800 r.p.m.

3 - PREROTATION ENGAGING - gently operate the prerotation lever (1). Keep engine speed at 1.800 r.p.m.

At 130 r.p.m. ROTOR

4 - CONTROL STICK - Place the control stick (2) in takeoff position (rear limit stop).

5 - PREROTATION LEVER - Gently reach the limit stop while keeping a constant engine speed.

WARNING DANGER: In windy conditions, or if the payload is light, it is possible that the gyroplane will lift up onto the tail wheel. If this occurs, the prerotation should be released and the stick moved forward to balance the gyroplane on the main wheels, some engine power should be applied to prevent the gyroplane from moving backward. The rotor rpm will continue to increase. When the rotor speed is equal or greater to 200 rpm, proceed as for take off. This should be practiced with an instructor before proceeding in these conditions

6 - ENGINE r.p.m. - Gently increase the engine speed until reaching 200 r.p.m. of the rotor. (standard prerotation).

WARNING DANGER: The minimum rotor prerotation speed is 150 r.p.m. It is strictly forbidden to proceed with takeoff operations if the rotor r.p.m. is lower than the minimum value.

7 - BRAKES - release (3).

8 - RELEASE PREROTATION LEVER - once the rotor turns at 200 r.p.m., quickly release the prerotation lever

1 - THROTTLE LEVER (1) - Increase the throttle in a progressive and uniform manner. NOTE: Increasing the engine power progressively guarantees the same level of progressive attitude of the gyroplane, thus simplifying the management of this procedure.

WARNING DANGER: In order to guarantee a safe takeoff, the engine’s power must increase progressively until reaching the maximum allowed value.

WARNING: If a rotor speed of less than 200 r.p.m. is achieved during prerotation, acceleration must be gradual. Engine rpm must be increased very carefully.

2 - ALIGNMENT - use the rudder pedals (2) (right pedal) to keep the alignment on the runway.

3 - CONTROL STICK (3) - in takeoff position (rear limit stop). Once the nose wheel has lifted, move the control stick forward and balance the gyroplane on the main wheels.

WARNING: During the balancing phase, the attitude must be so that neither the nose wheel (pitch down) nor the rear wheel (pitch up) touches the ground.

Practicing of “balancing” or taxiing on tarmac runways for more than 30 minutes continuous, without flight, may cause the brakes and the wheels to overheat. This is normal; restrict these exercises to periods of less than 30 minutes continuous.

4 - TAKEOFF: A) correct the roll induced by the engine torque (stick (3) to the left); B) reach and maintain attitude so as to obtain 65 mph [55 Kn] (Best rate of climb speed).

Yes, you're right and I stand corrected. The manual says 200 rpm... Both in the Australian as in the UK versions.

But, when I transitioned to the M24, I remember that the instructor insisted in 220 rpm. And he mentioned a peculiar vibration ('the Magni shake') that appears at 200 rpm and vanishes at 210 rpm, more or less...

At sea level, 200 rpm may be OK, but my field elevation is 3100 ft; that means –roughly– 10% less air density than at sea level, so 10% more revs seem justified...

Someone asked my privately how or why then Magni instructors in the US teach going to 130 RRPM and get going for takeoff.
My instructor taught 220 as optimal. Anything below 200 and I had to build it back up gradually (e.g. during a stop and go).
I really can't imagine anyone saying just get it to 130 and "get going"...

Please understand all I am saying is because of my limited experience and knowledge; if I am teaching in the clients aircraft I teach by their Pilots Operating Handbook.

Most of the gyroplane instructors I know teach by the POH.

If I am teaching in my aircraft (The Predator) I begin to roll and pre-rotate as soon as I have clearance and usually reach 100 rotor rpm by the time I reach the centerline of the 150 foot wide runway. I let go of the button (electric pre-rotator) when I see 120 rotor rpm and bring the cyclic full back staying below 15kts indicated air speed. I advance the throttle at 180 rotor rpm unless it is very gusty and then I wait till 200 rotor rpm. On a calm day I might see 110 rotor rpm from my pre-rotator when I am stopped.

As a commercial gyroplane pilot I am responsible to know the information in the POH before I fly it.

If I am giving a check ride I expect the pilot to inspect and operate the gyroplane by the pilots operating handbook.

If I am getting a client ready to take a check ride in a different gyroplane than they learned in I go over the POH with them before their proficiency check ride.

I don’t share Abid’s opinion that many gyroplane flight instructors invent their own procedures. Their learner would not pass a check ride with me.

It is my observation that often people know what they should do and for any number of reasons their body does something different.

I saw a client on the ASIAS report who had hit his empennage with the rotor and called him and he said: “Vance; before you even start I did three things you told me not to do. I let the tower hurry me; I took off in stronger wind than I was used to and flew out of__________Airport.”

He was a 20,000 hour pilot and old habits are hard to break.

I was please he remembered what I had said and sorry for his mishap.

I have made mistakes too so I did not say or even hint; “I told you so.”

One of my aviation mentors hit his prop with his rotor while he was spooling down so it can happen to anyone.

My instructor taught 220 as optimal. Anything below 200 and I had to build it back up gradually (e.g. during a stop and go).
I really can't imagine anyone saying just get it to 130 and "get going"...

There is a danger in building it back up gradually when you have a total of 3 months on you as a gyroplane add on pilot.
There is no definition of what gradually exactly is. Its easy to get ahead or behind and with any distraction get in a daze and gradually starts to become get going quickly.
That is the reason why I don't even bother with it. On initial takeoff, they need to reach 180 on position and hold before they release the brake. Have had very little trouble with it anywhere. Zephyrhills can get very busy and its not even a controlled airport and even then one can communicate and get out safely. I never teach pre-rotation and takeoff in one lesson. There is a 40 minute lesson of them in front seat on a side taxiway, just doing pre-rotation with me and an initial 30 to 70 foot roll like they will takeoff and then an aborting takeoff to a stop and repeat from the start. We repeat that for 40 minutes to an hour before they are ever in front seat doing pre-rotation for real takeoff on the runway. I also teach to pay attention to rotor RPM as gyroplane moves forward to see and catch the trend rotor RPM is going in. Fly safe and blue skies.

Every now and then I realize how lucky I've been to have fully articulated rotor systems on my gyros, where none of this stuff is ever an issue.

My instructor taught 220 as optimal. Anything below 200 and I had to build it back up gradually (e.g. during a stop and go).
I really can't imagine anyone saying just get it to 130 and "get going"...
In step 3 it does say “At 130 r.p.m. ROTOR” which could cause confusion.

I am surprised no one has asked any questions or made any comments on this. We are talking about POH and blade sailing like crazy on another thread which has drifted from its original subject and people are ready to argue about how to educate new pilots about that but when probably the best data about that subject is put out showing where it happens Nothing? Wow.
To be fair some have talked about similar for a long time except that discussion is a good entry to lengthy argument and as has already happened here the POH and rotor management as proxy to close the debate/validity etc...

To be fair some have talked about similar for a long time except that discussion is a good entry to lengthy argument and as has already happened here the POH and rotor management as proxy to close the debate/validity etc...
Hi Phil
I must be missing something in translation. Do you mean people talk about rotor management before but it just becomes an argument?
Or do you mean something else?
The fact that a big part of insurance increase in the US for gyroplanes is a result of insurance underwriters giving money out for Cavalon flip overs (mainly) that were avoidable right from takeoff or landing, its important to know what causes that.

To me its obvious that both Magni M24 as well as Cavalon are very short coupled and yes that is part of the issue but that does not seem to happen with such frequency in other countries so I have say its that US instructors do not train their students correctly or long enough or both. There really isn't another option in my view. One thing different might be that the US customer is probably older and probably has airplane experience prior than customers from other countries. I have nothing solid to support that though. Its just an educated hunch.

Replies
30
Views
1K
Replies
14
Views
2K
Replies
12
Views
2K
Replies
65
Views
3K
Replies
3
Views
385