CYCLIC PITCH

[newbheliusr]

What I did on mine to "reset" it was go to step L and back off the throw until the light went red. The just creep it fwd until the light went blue, I then stopped as opposed to going to max throws. This got me 11.4 degrees cyclic both directions. But even at 9 degrees I was still red. And I've heard of folks flying on red with no issues, so Capi seems to be correct (never doubted it) since people are doing it and not having problems. I think if the indicator light was purple or off you would have issues.

If you are getting inconsistent throws and your swash is level. I'd check my swash to servo links to insure each one is the proper length.

On my 450 pro and x5 this is easy due to all the servos sit at the same height so all the cyclic servos are basically level. So all my links are exactly the same length. Not sure what heli this is. You may have mentioned it earlier. Sorry if I missed it.

I think what I learned today is that once the light turns blue you should stop and go no further. But even on red it seems ok. Second thing I learned today is don't rely on the bx to know everything. Measure your cyclic pitch and see what it really is.

Rex

Just a thought.


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[sutty]

Dominic is but one person, and so far the only person I have seen with this opinion, and whilst I understand what he is saying, it is clearly contrary to the manufacturers instructions, and possibly to my own experience.

By definition setting J to a good resolution, blue at 6, or near to it, will cause the overall throw, available at L, to be restricted somewhat. Normally I would suspect sufficiently to prevent such incidents that Dominic showed with his picture.

All my helis have MBs fitted, and all have been maxed out at step L, and all have performed perfectly well. The cyclic value when maxed out like this tends to be around 15 degrees, and they are all set to 12 degrees collective, meaning that if the MB and I choose, it could at worst be applying 27 degrees of combined pitch to the blades.

This method is perfectly clear from the instructions, and is definitely what the manufacturers recommend you should do, and as a result there will be literally tens if not hundereds of thousands of other people out there following this exact same methodolgy.

I have literally thousands of flights logged across my 4 MB machines and have never had a mid air boom strike, and we have seen few reported cases in this forum. Perhaps but one, Dominic's. I certainly don't remember many others, if any, so this must be a perfectly acceptable method by which to set-up a MB. I do however have experience and recollections of people having mid air boom strikes on aggressively set-up FBd machines.

Dominic's point with regard to what maxed out might really mean in terms of the design of a new helicopter makes sense, but if the machine was capable of dangerously large angles, the resolution at J would be compromised, and you would have to fix this. As soon as you adjust J to give blue @6, you must by definition have restricted yourself to a maximum limit of about 15 degrees at L anyway, which must be acceptable, or helicopters would be falling out of the sky left, right and centre. The only way this can not be true is if you have servos that automatically rotate differently to normal, even when ATVs are set to 100%, as it is all linked to the resolution at J.

The MB flies my helis, I just point it with the sticks, and apart from in extreme rescue circumstances, even though I fly quite agressively, my helis rarely bog, and never boom strike. By extreme rescue, what I mean is where I am literally about to pile in, and at the last possible second I realise which way to steer, and apply both full collective and full cyclic, and hold it until it is rescued. Under such circumstances I hear the motor bog, sometimes significantly, but in all honesty this is a pleasant sound, as the alternate sound would probably be that of a loud thud, lol.

It should additionally be pointed out that these values are not quite as extreme as what they might at first seem. When you take a measurement of the cyclic pitch on a tradtional flybar set-up, and get say 9 degrees on a machine that is set-up for very aggressive performance, and think, wow, this is crazy, how can an FBL machine need or have 15, but what we have no easy method of measuring is how far, on the FBd machine, the paddles deflect over in flight and steer the blades to a much more extreme angle than the one we measured with the flybar level during set-up. 15, 16 degrees or even more would not be unheard of here. Try tipping your blades on an FBd machine and see.

Personally I shall not be changing my approach on the evidence of one boom strike, despite how much I value Dominic's opinion and knowledge.

Cheers

Sutty

[wanderer56]

Originally Posted by crf69

no no no guys....

cyclic pitch not collective pitch.

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Duh!!! My bad. It's not the first time I misread an earlier post.

Sorry.

Cyclic..........not collective.

[sutty]

Originally Posted by crf69

im leaving it alone then.....blue at 6 with no binding at all extremes flies good im leaving it.

what gets me is how i have unequal alireon pitch..

done confusing myself now.

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I have a possible explanation and it is likely to be of little to no consequence to the MB, and of even less significance to you.

During step G you have to centre the servo horns physically on the splines as near as possible. This often leaves one aileron horn off centre one way, and the other one the other way. This is now fixed up using the built in sub-trim of the MB, leaving the servo horns square, but the servos off centre in terms of travel in opposite diections.

When you go to L, and max out the travel step for cyclic, in line with the instructions, it is common to have no binding here, and the limit is caused by the travel limit of the servos, which is restricted in one direction, and increased in the other, due to the actual off centre starting position.

The MB doesn't really care, as even when you try to get the MB to deliver very fast rates, by increasing your travel adjusts, the MB doesn't often get to those servo limits in order to deliver the rate that you have requested. Say you get 12 in one direction, and 14 in the other, the MB probably only ever needs 11 to roll the helicopter at the requested rate, so it has a small overhead available in one direction, and a little more in the other direction, and as a consequence it would be unlikely to be observable from the flight behaviour. The same could easily apply to elevator too, depending on where the horns end up being positioned.

If you limit it down to say 11, for arguments sake, perhaps it would make it match, but you would now have no overhead for the MB to use to increase throws as necessary when conditions dictate, to maintain the requested roll rate.

Personally I have never even checked if they are equal, and I have only ever measured the cyclic as a matter of curiosity. I just follow the instructions to max it out, have never had any binding, and never had any odd tendencies using this method, as recommended by the manufacturers.

Cheers

Sutty

[DominicD]

Sutty nice posts. There is no right or wrong way, and I only posted what mine finding have been. Basically I found that if I didn't limit my cyclic I was able to cause seriously fluttering problems. I doubt many pilots are able to fly a BX hard enough to encounter this, but I stand by what I posted.