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CarbonXtreme . Midland Helicopters . HeliProz

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Main Discussion > Is different gyro gain needed for different flight modes?
 
 
TMoore
rrProfessor
Location: Cookeville, TN

I used to do 180 autos with a Magic II and a non driven tail and I can tell you that with the tail stopped whether you have gain or not on the gyro it makes no difference.

One dude says to use rate mode and too much gain will kill headspeed. Another dude says that moving the tail rotor will kill off headspeed and that isn't good. Who's right? How the hell do you do a 180 auto without moving the tail rotor if the tail is driven?

Quote 
On the throttle hold I drop the gain a bit to reduce the energy that the tail consumes.
I doubt you can prove that this works or doesn't. Doug says that the gyro is 100% efficient so who's right? Do you dudes do 180 autos or 180 autos with two 90 degree legs? If you follow these theories we would crash every time we tried. I guess I've been lucky so far, I've been able to do them no problem.

Quote 
Dont know about no Gain in Throttle hold,the TR still has to hold the tail from turning even if you give it input.


Would you mind explaining what you just said because my english is limited.

TM
02-20-2006 Over year old.
HOMEPAGE  
 
 
ChristianM
Veteran
Location: Oslo, Norway

PH7 and Douglas

Quote 
What he meant is that if the gyro is set up correctly it will only give tail rotor input if it is necessary to maintain the heading you have requested. It will not over compensate and then need to correct, like you might have to do yourself. The gyro will do the minimal amount of work (tail input) to keep the heading you want.


Well this is not correct, the higher the gain is the faster the gyro will drive the tail in to the commanded position (or yaw rate). This will require a larger force from the tail rotor both to accelerate and decelerate it and thus consume more energy from the head. Using a lower gain (within in reason) will still get you to the same position but it will take a little longer and consume less energy.

Christian

Burn fuel, be happy
02-20-2006 Over year old.
 
 
ChristianM
Veteran
Location: Oslo, Norway

TMoore

If you are using a non-driven tail then the gyro gain makes absolutely no difference since the tail is not producing any force.

When doing an auto there is no torque produced by the engine and as such the demand on the gyro is much reduced (for a driven tail).
Edit: So the gyro gain is not a big issue until you start doing backwards autos or pirouetting autos.

Christian

Burn fuel, be happy
02-20-2006 Over year old.
 
 
TMoore
rrProfessor
Location: Cookeville, TN

Y'all need to go to Japan and show the 3 time WC how it's done because Hashimoto has been doing it wrong all this time.

The reason I said this; "You can turn the gain off in an auto and you won't be able to tell the difference" was to illustrate a point and that point is that gyro gain doesn't have a helluva lot to do with whether you have inertia at the bottom of an auto or not. I didn't say you should turn the gain off, I said you 'can' turn the gain off and in terms of inertia you won't see a difference. The problem with RR is that y'all don't read the complete thread and then some of you parse what someone says to your own view. I do this too and it is a failing of mine so I'm not a saint here either so don't take this as criticism, just an observation.

Back to Hashimoto's setup for FAI autos, he is running the 611 gyro at an EPA of 100 points in the Stylus which equates to 60-65% gains at the 611 gyro brain box. If you apply all of the popular theories so far, his models should be in Yokohama harbor right now because they would run out of inertia due to high gyro gains.

TM
02-20-2006 Over year old.
HOMEPAGE  
 
 
DS 8717
rrProfessor
Location: Here wishing i was somewhere else

Quote 
DOUGLAS

I am not sure what you mean by the Gyro is 100% efficient but the higher the gain is on the gyro the larger the commanded servo response will be to a given tail disturbance hence it will consume more energy from the main rotor.

Edit: That why when the gain is to high the tail starts to wag because it is over compensating.

Christian

I am speaking about a properly set up gyro gain. Of course if the gain is too high it will overcompensate and use up energy. But with the correct gain overcompensation is not likely and the gyro is only giving enough TR input to keep the tail where you want it. If you dont have enough gain and the tail starts to move quickly,you are MORE likely to overcompensate with too moch TR input. And if you are doing piro and backward auto,s it is even more critical. Because there is no torque to fight from the engine,Gain in TH is not as critical as far as tail wag. where the problem comes in with no gain or not enough is when you apply positve pitch to stop the heli the heli will turn, and sometimes very quickly. I'm like Tom, gain in TH wont make any difference in efficency,l feel like you more likely to use to much imput trying to control the tail without any gain. DOUG
02-20-2006 Over year old.
 
 
ChristianM
Veteran
Location: Oslo, Norway

TMoore

Nobody has said anything about running out of inertia and falling out of the sky if you have high gyro gain except for you. But it is a fact that if you apply a lot of rudder input during an auto then this will consume some energy. Now this can be regained if you have the altitude to get the head speed up again. It is the same thing with a high gyro gain it will consume a bit more energy but as I have said before is is not a big deal, technique is the biggest factor. Many of the discussion here on RunRyder is about optimizing and this discussion falls in to this category, it is not black and white. There is nothing that I have said that is contradictory to your statement about Hashimoto's setup.

Christian

Burn fuel, be happy
02-20-2006 Over year old.
 
 
TMoore
rrProfessor
Location: Cookeville, TN

Christian,

Backwards autos are a whole different flight regime and I will agree that you will need the gyro to get proficient at those. I do 6 or 7 backwards autos every flight and my gyro is on babee.

For me personally, this whole discussion is predicated on the issue that there is just so much utter BS out there on these forums that is rooted in repetition of OPP (other people's posts). It seems that very few folks want to actually try what they are posting about. This hobby has always been about cutting and trying. The best thing that I have found is to try things and see what happens.

TM
02-20-2006 Over year old.
HOMEPAGE  
 
 
ChristianM
Veteran
Location: Oslo, Norway

Douglas

See my next post :
Quote 
the higher the gain is the faster the gyro will drive the tail in to the commanded position (or yaw rate). This will require a larger force from the tail rotor both to accelerate and decelerate it and thus consume more energy from the head. Using a lower gain (within in reason) will still get you to the same position but it will take a little longer and consume less energy.


Now I do agree with you that if you drop the gain to much then it will result in poor holding power and may end up consuming more energy when doing backwards auto's if the gyro can not hold the tail in the commanded position. It depends on how hard you feel you need the gyro to hold you tail during these maneuvers.

Christian

Burn fuel, be happy
02-20-2006 Over year old.
 
 
DS 8717
rrProfessor
Location: Here wishing i was somewhere else

I just think the gyro will use quicker and smaller inputs to keep the the tail pointed where you want it,especilly on auto's. I feel like you tend to use more input than needed sometimes if you you do it with low gain,so i feel like the Gyro is more effecient than someone moving the sticks. And so i think if the gyro is set up correctly it is close to 100% effecient.Why else would HH gyro be more used instead of rate gyro's. It is keeping the tail under more constant control vurses a rate gyro.True it does cause quicker servo wear but if you could input the TR as fast as a HH gyro the same wear would still be there. DOUG
02-20-2006 Over year old.
 
 
TMoore
rrProfessor
Location: Cookeville, TN

This thread is undergoing some serious thread drift. Now we're discussing the relative merits of gyro gain in backwards autos.

The original premise was: Is different gyro gain needed for different flight modes?

Some folks say no and others say yes. Who is right? My stance is that it doesn't matter for sport flying but it does matter if you are a contest pilot. Run the gain settings that you want and burn fuel. Changing the gain that you are running from one flight mode to the next is a matter of personal preference but IMHO, lowering the gain won't make a bit of difference for autos.

TM
02-20-2006 Over year old.
HOMEPAGE  
 
 
ChristianM
Veteran
Location: Oslo, Norway

Douglas

We are probably splitting hairs here, but from a theoretical point of view a lower gyro gain while still holding the tail good will use less energy, but we are probably at a point of diminishing returns here. I have dropped the gain a little in throttle hold and the tail holds fine for all the auto maneuvers that I do (backwards and pirouetting). I doubt that I would notice any real difference in the remaining inertia if I raised the gain a bit but I have not experimented a lot with this.

Quote 
Why else would HH gyro be more used instead of rate gyro's. It is keeping the tail under more constant control verses a rate gyro

A HH and a rate gyro is the same thing but I assume that you are comparing with a conventional gyro or HH in normal mode. These work very differently and is comparing apples to oranges. A conventional gyro can not maintain backwards flight (without pilot input) regardless of how high the gain is set.

Christian

Burn fuel, be happy
02-20-2006 Over year old.
 
 
DS 8717
rrProfessor
Location: Here wishing i was somewhere else

That is how i set up the gain in TH on mine. I set the gain up untill it held in backward and piro auto's. It turned out to be a little higher than normal and idle up. DOUG
02-20-2006 Over year old.
 
 
oldboldpilot
Key Veteran
Location: Southern California

Could we agree the optimum gyro gain setting in any flight condition/mode is the minimum that will do the job?

Helis are Man's Defiance of the Laws of Nature - OCHC
02-21-2006 Over year old.
 
 
TMoore
rrProfessor
Location: Cookeville, TN

Quote 
Could we agree the optimum gyro gain setting in any flight condition/mode is the minimum that will do the job?



Yeah, we could but the only way that you arrive at the minimum gain is by flight testing and it's not the same on everyones machine and it varies by pilot.

TM
02-21-2006 Over year old.
HOMEPAGE  
 
 
DS 8717
rrProfessor
Location: Here wishing i was somewhere else

Quote 
Could we agree the optimum gyro gain setting in any flight condition/mode is the minimum that will do the job?

That is how i set up the gain in TH on mine. I set the gain up untill it held in backward and piro auto's. It turned out to be a little higher than normal and idle up. Since i run 1950 headspeed in idle up,it doesnt need a high gain setting. Normal is 1650 so i can run more gain than idle up.I use a governor so the headspeed is very constant with no overspeeding.DOUG
02-21-2006 Over year old.
 
 
sir777
Senior Heliman
Location: Moscow, Russia + Lloret de Mar (Girona), Spain

Guys, thank you for explaining all these subtleties, but actually, while I was asking this question, I didn't think about TH mode, I thought only about normal and idle-up mode. As zoom boy said, when "you increase the RPM then the tail RPM increases aswell, if that happens then you need to reduce the gain on the tail slightly as the tail is now capable of producing more yaw power at maximum throws, and at all points in between compared to the lower RPM." I noticed that thing also, while I was setting my gyro last time, but I wasn't completely sure because I had many problems with my heli (crazy overspeeding up to 2300 rpm, because I didn't have governor and I have os 50 hyper, which is very prone to this, and vibrations, which caused by many things, as well as probably by that overspeeding) and I thought that it might be some problems with additional vibrations in idle-up mode, which caused gyro to work not very well and to wag. It looked like I need about 5-10% gain less in idle-up mode, then in normal mode. It looks quite logical to me, because of additional tail rpm. At that moment I am not able to test it again myself, because of cold weather here and because I haven't finished balancing and dial indicating me heli to stop the vibrations. The real-real reason for this question actually was, because at that moment I have a 8-channel radio Sanwa RD8000 with a futaba gy502 and a tj pro, and I have to choose either to have the ability to change flight modes together with gyro gain or to change flight modes together with governor headspeed settings, because of only 8 channels setup. Of course, I will choose changing flight modes together with headspeed, but than, I will have to either have the same gyro gain in all flight modes or to switch the switch to change gyro gain after changing the flight mode.

Hope, I didn't confuse too much, guys, and thanks for you information about usage of gyro in TH mode, I might consider it in future, when I'll start to do real autorotations.
02-21-2006 Over year old.
 
 
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