Trex doesn't maintain steady altitude at hover - RC Groups
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Aug 05, 2005, 11:11 AM
Heli Headcase
Orion_V's Avatar

Trex doesn't maintain steady altitude at hover

Hey guys...been having this weird problem with my Trex. All linkages seem to be setup right, main blade pitch and paddles are all setup, etc..but for some reason while I hover the heli wants to either quickly drift up or drift down at any moments notice.... I can never maintain a steady altitude for a good amount of time. At first I thought maybe my governor was not operating correctly, was using a CC35 and just recently swapped it out for a jazz but still experiencing the same issue. At hover my blades are tracking perfectly. My last flight i noticed that two of my ccpm servos were not tightly mounted on my CCPM frame (heliworkz). They had a lot of I'm going to make sure these are all tightened up for the next flight. But what about anything else? The only other thing i can think of is that maybe my pitch servos are glitching a bit...causing this sudden change in altitude with no input. Any other thoughts or suggestions on things I should look at?

I'm running an Align 400LF with Jazz 40/16/8 ESC, TP2100 , HS-55's, 13T pinion,

Thanks for any help or input on this...
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Aug 05, 2005, 11:25 AM
Seemed like a good idea!
beemer's Avatar
I have a similar issue with my Blade. On of my servos is bad and glitches alot causing an unsteady hover and climb/decend issues as you describe.
Power everything up (disconnect the motor) and slowly run the controls through full motion while looking for any binding or glitching. If nothing is found repeat the process but put a little "resistance" on the servo's to see how they handle it. My bad servo behaves pretty good until I put a load on it (like flying or by hand) then it goes crazy.
Aug 05, 2005, 11:41 AM
Heli Headcase
Orion_V's Avatar
thanks Beemer...funny you mention the bad servo possibilty..on the last flight I had one of the servos go bad on just seized (stripped gear). Maybe it was on its way out while I was experiencing these issues. I'm replacing it this weekend but will perform the test you described. This problem is very annoying...
Aug 05, 2005, 12:13 PM
A-4 nut!!
skyhawk's Avatar
I've got the same problem and can't figure out what it is.

I've heard of this happening on more than a few occations.
Aug 05, 2005, 12:20 PM
Heli Headcase
Orion_V's Avatar
bummer...i will definitley post back if I find a solution....
Aug 05, 2005, 12:26 PM
Seemed like a good idea!
beemer's Avatar
Well, off to the LHS for a new servo . I'll keep you posted on my results.
Aug 05, 2005, 12:45 PM
Heli Headcase
Orion_V's Avatar
please do Beemer...i wont make it to the LHS till Saturday...
Aug 05, 2005, 02:39 PM
Some things to check if you are "drifting" while hovering besides your servos. Make sure the servos are mounted securely, make sure your links all move very freely and check for loose ball links. I chased my tail for a long time once with a tracking issue that turned out to be a slightly loose ball link. Sneaky little bugger.
Aug 05, 2005, 03:40 PM
Heli Headcase
Orion_V's Avatar
Yes 2 of my servos were not mounted securely....i am really hoping this is the issue...I will check on the lose ball links as well...thanks..
Aug 05, 2005, 04:13 PM
Seemed like a good idea!
beemer's Avatar
Well, I wasn't able to make it to my LHS today after all. The "tile" guy was here doing work in the kitchen which kept me from getting to the LHS. Stupid tiles! What fun are they anyways?!
Aug 06, 2005, 08:20 PM
Heli Headcase
Orion_V's Avatar
well...i bolted on all my servos real tight and i'm still having this issue...i did notice something quite interesting though during the servo testing...with my motor unplugged i was giving positive and negative collective input...i noticed that one or more of the collective servos were "lagging" behind....meaning after i gave an input and stopped....the servo arms kept moving into position and then stopped..this took a few seconds...really weird. I think this may be the issue....but why its doing this i really have no idea. I did not find any binding by the way...
Aug 06, 2005, 08:28 PM
Goodpasture's FTW
Keith R.'s Avatar
Is it the wind? I know when i fly mine that if there is wind it will go up and down instead of being blown back.

Aug 06, 2005, 08:47 PM
Seemed like a good idea!
beemer's Avatar
Originally Posted by Orion_V
i noticed that one or more of the collective servos were "lagging" behind...
Disconnect the links from your servo arms, disconnect the motor leads (for safety) and run through the same tests. See if all the servos react together or if one lags behind still. If it does, swap it's location in the RX with one of the other servos and repeat the test. If the lag stays with the original servo then the servo may be weak. If the lag remains with the same port on the RX than I have no idea what else it could be. Sorry. Good luck though.
Aug 06, 2005, 09:42 PM
Heli Headcase
Orion_V's Avatar
Will do beemer...i'll report back...thanks

It is definitley not the was calm. Plus I normally fly in wind with my corona so i would know how that would feel like. I wish that was the issue though...
Aug 06, 2005, 09:49 PM
Registered User
Ping's Avatar
I think it's an issue with the Trex head. I'm working on trying to fix the same instability. I find around 20-30 ft my Trex will hover altitude is pretty stable. But anything closer to the ground and it's a fight to keep a steady altitude.

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