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HelicopterBergen R/C Helicopters › EB Severe Pitching
05-08-2005 11:19 AM  13 years agoPost 1
dshepard

rrApprentice

Concord, NC - USA

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I am getting more and more flight time on my new EB Gasser. As I am getting faster and faster in FFF I am noticing a tendency for severe up pitching. For example I will take it upstairs and do a stall turn and start accelerating down. To level it out as it is building speed, I give it SLIGHT up elevator (cyclic) and WHAM!! it pitches up and almost stops!! Scared the bejesus out of me the first time. This is repeatable so I now avoid high speeds. Other than that, I am really enjoying the helicopter.

Would anyone have any idea where I should start looking for possible causes? This is my first large helicopter, I have been flying a Raptor 50 for over a year now and consider my self an accomplished flier. I don't do 3d, just an occasional loop every now and then (the Raptor, not the EB yet).

I am running NHP 800mm for the mains. My head speed is about 1470 as measured with an optical tach while in flight. It does speed up a little on the descent. I am shooting for 1450, but as the engine is breaking in there have been minor changes.

As an aside, what is the lower limit for a suggested head speed?

Thanks in advance for any help.

Derek

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05-08-2005 02:38 PM  13 years agoPost 2
wolfdad

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Southern Maryland

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Derek,
First thought that comes to mind is that you may have some binding somewhere in your flight controls that is causing a "hesitation" at some point, then being overridden by the servos, i.e., a bind, then a "pop" as the servo (s) overcome the bind and a large change in servo position. I would recommend you go back through your flight control set-up, paying attention to the extremes and see if you have some binding.

Good luck on this...

wolfdad sends....

"There are those who have...and, those who will" IRCHA #2117, AMA #70068, Turbine Waiver #105

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05-09-2005 09:31 AM  13 years agoPost 3
Malorie

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Paw squared, MI

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Check your paddle alignment and the CG of the machine.

Malorie

Life's a journey, NOT a destination.

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05-09-2005 10:02 AM  13 years agoPost 4
dshepard

rrApprentice

Concord, NC - USA

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Thanks all, I will be out of town most of this week, so I won't be able to check it out until maybe this weekend. I will let you know what I found out.

Derek

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05-09-2005 03:17 PM  13 years agoPost 5
Christopher J

rrElite Veteran

Kansas City, MO Californian lost in land of Oz

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Can you change the dampening in the head? Sometimes with big machines if you have a semi soft head and slightly less then optimal head speed you will get a pitch up tendency in fast forward flight. I had a ship that did this and I put an extra shim in the head along with going with hard dampeners. Fixed the problem.

Christopher J
same as I ever was
"Still all set & Flying the original"

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05-10-2005 08:28 AM  13 years agoPost 6
Ozzy Pilot

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Victoria, Australia

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I wouldn't mind betting that your EB is tail heavy as Malorie said above your CG will be to the rear of the main shaft.

Cheers

Member of Good Guy list (seller) Pg. 23. Turbines - Audile pleasuring

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05-14-2005 11:29 AM  13 years agoPost 7
dshepard

rrApprentice

Concord, NC - USA

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Thanks for all the replies. I have checked the CG and it is good (ever so slightly nose heavy). I am using a 3500mah NiCd battery and 1lb of tape on weight to balance. Double checked the control system and sitting on the bench I didn't notice any binding. When I assembled the head I put all the supplied shims and o-rings in.

All that is left are the paddles. They appeared to be in alignment using the Mavrikk paddle gauges. The kit was supplied with light white paddles which had two mounting locations. I mounted the fly-bar in the holes closer to the leading edge thinking that would make them less sensitive. These paddles also have "sharp" leading edges.

What I am doing today is trying some heavier less "aggressive" paddles from an old Kalt Cyclone II I have. These have a blunter and more rounded leading edge.

Does anyone have any comments on the correct mounting of the white paddles?

Thanks, Derek

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HelicopterBergen R/C Helicopters › EB Severe Pitching
05-15-2005 11:27 AM  13 years ago •• Post 8 ••
dshepard

rrApprentice

Concord, NC - USA

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The paddles were it, no pitching yesterday.

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05-15-2005 02:58 PM  13 years agoPost 9
Malorie

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Paw squared, MI

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Your thinking is correct. The front holes will make them a bit less sensative.

I'm with you on paddle selection. I like a fatter air-foil. I run the 85mm V paddles on my Gassers.

Glad you found your pitching issue.
Malorie

Life's a journey, NOT a destination.

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05-15-2005 03:07 PM  13 years agoPost 10
Gary Travis

rrVeteran

Utah

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Something to check
I have seen one do this before, It was caused by play in the elevator arm which connects to the elevator upgrade. Make sure you have the socket head screws in the pins that come out to the elevator arm. The one I fixed had the two scres that came in the elevator upgrade bag installed and will not hold the arm in place. (the srews in the bag are for the canopy mounts in order to clear the upgrade when installed). When I flew the heli the elevator would be sogf until it finaly caught up with the the play and then it was way to quick.
Gary

Bergen R/C Helicopters Duralite Batteries DJI Innovations Magnum Fuels Wren Turbinesl

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HelicopterBergen R/C Helicopters › EB Severe Pitching
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