Flapping warning device

EI-GYRO

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Two comments;

1) For a given gyro/rotor setup, we know the combinations of airspeed and rotor speed AND DISK ANGLE, that cause flapping on takeoff, so by monitoring Rrpm, and airspeed AND DISK ANGLE, this ............etc. You will need to measure all three.

There are two other methods possible.

One is to use centrifugal teeter stops/bumpers to prevent/give warning of excessive parameters.

Another is one I used myself, and that is rubber-padded teeter stops. This for two purposes, one to give a little advance warning of impending flap, and also to protect the bottom of the hub bar from metal contact and damage. As I dont use a prerotator, this is very useful when hand-starting in gusty conditions, but it might also be of use in discouraging excessive 'pushing' of the rotor acceleration, and allow a little tolerance of a small mistake before it gets to a big mistake.
 

gyrojake

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If you were to make a warning device for Blade Flap.
Knowing what the blade goes through from beginning to end would help a lot.
Before any physical manifestations of the flap are noticed by the pilot a wave is actually generated in the blades, they are no longer straight, sagging or coning at any given time, there is a wave in the blades themselves.
Now with that being said any body with a bit of electronic knowledge could make a simple analog circuit using a laser to measure the wave.
Once a wave in recognised an alarm, a light or even a mechanical hand to slap the pilot could be activated.
What is really funny about this is that there is not one helicopter with a mast bump warning alarm !!
Low G's in the air and out running the blades on the ground are most popular blade flaps.
Mike, if you would like, I could assist you with this but pilot training is a better option
 

Jazzenjohn

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You could have a mechanical warning device where, if the blades were flapping too much they would hit stops, sending a pulsing signal through the stick that would get stronger and stronger if the problem wasn't immediately corrected, eventually resulting in a hammering of the stops if nothing were done. It would require training to fly the blades rather than training to a set checklist like "Prerotate to X, then push throttles forward, pull stick back at 45 knots" or some such thing. If the blades weren't spun up enough or there was too long a pause before pushing the throttles forward and the blade speed was decaying or some other issue, the training should dictate the response rather than simply following a checklist to a sad end.

That said, there might be a use for a big red flashing warning light where, when lit, students could be trained to abort the takeoff.
 
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GyroCFI

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That's a good idea Mike and I hope your device works as you expect it to. I do have to say though that proper training on rotor management on takeoff is the key here. I spent a long time with each of my students going through rotor management which starts even before the engine is started and concludes when the rotor stops and the engine is turned off.

You can't replace good training with a device.
 
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EI-GYRO

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You can't replace good training with a device.
No, you can't, but you can design your machine better to reduce the likelihood of pilots making mistakes.

Bensen had a spring link between the nosewheel and the rudder, the lack of which is probably the main cause of landing upsets.
Having to hold the nose off until almost stopped is ridiculous and should be unnecessary with proper design.
Similarly, having a prerotator system which does not allow the rotor disk to be tilted back while prerotating is inefficient in operation, and
results in a 'bunched' sequence of actions while transitioning from prerotation to takeoff roll. This is poor design from a human factors point of view,
as sequential actions are less rushed and less error-prone than with bunched/clustered/grouped actions.
Fixing these issues would have the advantage of benefiting everyone, as they are not subject to the varying opinions of students, and yes, instructors.
All that said, it ain't gonna happen, cos it is easier and cheaper to stay with an approved crappy design than get a different design through the system.

Boeing knows all about that.
 

Brian P

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"Similarly, having a prerotator system which does not allow the rotor disk to be tilted back while prerotating is inefficient in operation, and
results in a 'bunched' sequence of actions while transitioning from prerotation to takeoff roll....."

Spot on. As far as I'm aware this is not happening on Magnis.
 

EI-GYRO

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That is my impression too. Magni also has a low tailboom, which probably prevents over-rotation and rotor groundstrike.
 

EI-GYRO

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Might be easier to just learn how the damn thing works!

How about proximity sensors on the teeter stops?

My guess is that recognition time+reaction time>> correction time available, whatever system you use.

See line 1.
 

gyrojake

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Either we read differently but boils down to what I said. Or maybe it doesn't make sense the way I worded it. It's Operation is not confusing to me.Rotor RPM to low for forward speed is the basic result.
 

EI-GYRO

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If I understand it correctly it reads rotor speed and ROTOR acceleration, not machine acceleration.
How do they calculate nominal, or do they let you set it yourself.?
How much acceleration is enough? You could have an accelerating rotor and still overrun it by accelerating the machine too quickly.
Has it been tested,?
Sounds like the IBM torque setting, up to shear and back a quarter.
 

DaveJaksha

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I agree that the manual says it is measuring the rotor rpm and rotor acceleration. The graph shown implies rotor acceleration also.

Dave
 

Alan_Cheatham

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Below a nominal rpm, which according to the manual appears to be set at 250, it is looking at a positive acceleration of the rotor to indicate a safe condition and a de-acceleration to indicate an unsafe or impending rotor flap.

So the question is, does the rotor begin to de-accelerate if airspeed is too high for the current rotor rpm?
Does rotor rpm drop before mast bumping?
(Assuming a take-off condition)
 

gyrojake

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How do you get rotor acceleration without forward motion? If you use a prerotator to 200 rpm you would not need this device
Forward motion is the affect to accelerate your rotor.

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Mike G

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Deleted due to lack of interest in the subject
 
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