Is Negative Pitch Necessary?

[Papa Tom]

I was showing my MCPX to a friend who was a helicopter pilot, in Nam, and explaining the controls. When, I got to the part about negative pitch he stated a “real helicopter” does not have negative pitch.

Well this got me thinking. I am not interested in flying inverted, at least not now, so what is the benefit in having negative pitch. If your pitch curve went from 0 to 100% wouldn’t that give you more precise control of your positive pitch?

[Drivinfast247]

That would be fine if there was zero wind and you never planned on landing.

[UKHeliBob]

Wait until you are flying in Normal mode with no negative pitch and a gust of wind takes you up, then you will understand the need for negative pitch even if you don't intend to fly inverted. The chopper that your friend flew was slightly heavier than an mCPX, to say the least, and could not fly inverted if it tried.

It is true that if you set the pitch curve range from 50% to 100% (0 to 100% positive pitch) then you will have finer control over pitch but in practice you will not notice it.

Incidentally, I suggest that you fly in IU rather than Normal mode or set the Normal throttle curve to the a high value across the board. The constant,high head speed makes flying so much easier.

[Papa Tom]

Thanks for the replys. What you say makes sense. I didn;t have an answer for him and it got me thinking.

Thanks again

[Coco66]

As far as I know, some "real helicopters" DO HAVE negative pitch, even if it's mostly used to keep the heli glued to a boat deck.

Maybe not yet in Nam.

[junkpilot]

I beleive I've heard that all U.S.A. military rotorcraft must be able to autorotate. If you can auto without negative pitch I want lessons.
Junkpilot

[everydayflyer]

I have never seen a CP heli that would not desend,even in a high wind at zero pitch. I do believe however that anyone flying CP should get use to having negative pitch but there is no have in having a greadly reduced amount of it in the early stages.

Normal pitch curve of 30% 50% 75 % 100% will seem smother .Limiting the max. to 80% would even be smother and 100% positive is not needed for hovering and moving around in FF at slow speeds.

[Diogenes]

I'm about to begin to attempt some things like getting into barrel rolls and inverted flying on a BD14/walkera and a governed HP05 (its on its way to me).

I have a C05 that I'm doing at 30 40 50 75 100 for sport flying,etc. What's the best pitch curve in your opinion for the first two above? Will be flying in IU at 90 on the BD, on the 05, I have do to some more research.

This prolly should be asked in the brushless forums, but it seemed applicable to either motor type

Thanks

[everydayflyer]

MOst want the same negative pitch available as upright when doing any flying which has inverted segments in it but honestly for many manuvers such as rolls and loops while in FFF very little negative pitch is required and with some heli that are fairly fast no negative is required during such manuvers.

[Diogenes]

Think I'll leave it as is till I have the loops/rolls down. Then change curve for inverted then.

Gonna do some more sim time before inverted though. Got hold of a decent cpu that I'm gonna hook to my plasma screen this weekend, so that should be fun to fly sim on.

[UKHeliBob]

Originally Posted by everydayflyer

I have never seen a CP heli that would not desend,even in a high wind at zero pitch.

Wind is not the problem, gusts are.

Even without gusts a heli at zero pitch will be blown along at the speed of the wind which may not be desirable.

[Hubec]

Originally Posted by junkpilot

I beleive I've heard that all U.S.A. military rotorcraft must be able to autorotate. If you can auto without negative pitch I want lessons.
Junkpilot

Manned helis auto with positive pitch, I've done it 100s of times. A seach turned up this great explanation http://www.copters.com/aero/autorotation.html I'm not aware of any manned helis that can attain negative pitch.

I suspect the only reason rc helis require negative pitch to auto is because their small mass means they can't drop fast enough to overcome their relatively high drag and high mechanical friction at any amount of positive pitch.

[Coco66]

Originally Posted by Hubec

Manned helis auto with positive pitch, I've done it 100s of times. A seach turned up this great explanation http://www.copters.com/aero/autorotation.html I'm not aware of any manned helis that can attain negative pitch.

I suspect the only reason rc helis require negative pitch to auto is because their small mass means they can't drop fast enough to overcome their relatively high drag and high mechanical friction at any amount of positive pitch.

Really? Read this. Looks like those guys ARE aware of manned helis tht can attain negative pitch:
https://www.helifreak.com/showthread.php?t=149271

Me, no idea, but who should I trust?

[Talesin]

In my opinion it's quite important to have both positive and negative pitch available at all times. Even aside from being quite useful for fighting wind, it actually gets you used to controlling the helicopter properly. With no negative pitch, it's a bit... training wheels.
You're really expected to be past that point by the time you get to a collective pitch heli.

Also, a number of full-size helis can apply negative pitch; there are one or two that CAN pull off loops and rolls, and theoretically fly inverted (the RedBull stunt heli is one that regularly will do flips and loops at sporting events, for example).

[everydayflyer]

Once again the OP has been almost totaly lost in this thread. Not everyone is into invereted flying, stationary flips,rolls and such.

For some having negative pitch just means they will crash harder. These is a logical reason why Normal Pitch Curve does not have nearly as much negative as positive pitch.

[Diogenes]

Originally Posted by Talesin

In my opinion it's quite important to have both positive and negative pitch available at all times. Even aside from being quite useful for fighting wind, it actually gets you used to controlling the helicopter properly. With no negative pitch, it's a bit... training wheels.
You're really expected to be past that point by the time you get to a collective pitch heli.

Also, a number of full-size helis can apply negative pitch; there are one or two that CAN pull off loops and rolls, and theoretically fly inverted (the RedBull stunt heli is one that regularly will do flips and loops at sporting events, for example).

Yep gonna put pitch curve back to linear once I get used to using throttle hold at all times. The 30 x x x x curve is to give me time to recover as I adjust my habits. I slammed my bd into the ground hard the other day when I forgot I wasn't flying my brushless msrx.

Sorry guys, for the threadjack

[Hubec]

Originally Posted by Coco66

Really? Read this. Looks like those guys ARE aware of manned helis tht can attain negative pitch:
https://www.helifreak.com/showthread.php?t=149271

Me, no idea, but who should I trust?

Why are you being so negative? All I said was I'm not aware of any manned helis that can set negative pitch, i.e. of the helicopters that I've personally flown, none of them were capable of negative pitch - and negative pitch is not required for autorotation. I feel I contributed some useful first hand information to this thread, and hopefully helped educate some viewers, so what's with your negativity?

[everydayflyer]

Were you able to land the ones you flew even in gusty winds?


Just kidding as I still do not understand why so many feel negative pitch is mandotary on a CP RC Heli.

I do admit that a FP heli is very difficult to fly in gusty winds but evne that can be done .

[Coco66]

Originally Posted by Hubec

Why are you being so negative? All I said was I'm not aware of any manned helis that can set negative pitch, i.e. of the helicopters that I've personally flown, none of them were capable of negative pitch - and negative pitch is not required for autorotation. I feel I contributed some useful first hand information to this thread, and hopefully helped educate some viewers, so what's with your negativity?

Yes you are right, I've been a bit rude.
Also due to my bad english.
But if you say "I've done it 100s of times" you should then probably know also what else is around... at least when you say the opposite of what some others are saying... it really looked like you said "I'm a REAL pilot and you are saying bullsh.t".
But again, it's probably my bad english, man!

[Talesin]

Originally Posted by everydayflyer

Were you able to land the ones you flew even in gusty winds?


Just kidding as I still do not understand why so many feel negative pitch is mandotary on a CP RC Heli.

I do admit that a FP heli is very difficult to fly in gusty winds but evne that can be done .

Yes. That's one reason to have negative pitch. With a FP, sometimes you get to choose between watching the wind carry it higher thanks to TLE, or cutting the throttle and losing cyclic control as a consequence. Or bouncing between the two, hoping to keep it low enough and close enough until (if) the wind dies down to the point where you're able to land it without just letting it hit the ground unpowered (one reason my 120SR is just a dust-catcher at this point).

With collective pitch, you can apply zero or negative pitch while still maintaining complete cyclic control, actively compensate for the wind, and continue to fly normally in situations that a FP simply cannot handle with any kind of grace. If you're in a REALLY bad situation where the 30-40-50-75-100 curve isn't sufficient to overcome the effects of the wind, you can go into IU to apply even MORE negative pitch. Which I've had to do on a number of occasions, when the wind was getting up past 20mph.

Again. If you're not going to take advantage of what a collective pitch heli has to offer... why are you buying one? You don't need to fly 3D to make use of negative pitch. You also don't need to fly with a 0-100 linear pitch curve at all times.

And really, it looks like the original poster's question was answered within the first four posts, so a bit of derailing doesn't seem to be too bad.