450 Align Trex 450 Pro v2, rapid loss of altitude while in stationary hover

Crashnaz

New Member
I have the aformentioned heli, while hovering in idle up approx 10' off the ground, little to no wind, helicopter will experience a sudden loss of altitude requiring 1/8-1/4 positive pitch input in order to maintain altitude, I under stand ground effect when hovering low however at 10'+ this shouldn't be an issue. Radio gear: spectrum dx7, spectrum ar8000 with sat receiver. I had my setup doubled checked by local club member, no significant changes needed. No noticable motor noise change, or voltage drop when loss occurs

Thanks
 

D.O.G.

Goblin 380 Supporter
Hey there Crash and welcome. Silly question here but how old are your batteries you are using? Almost sound like a cell or cells are not holding it's charge. :2c:
 

Crashnaz

New Member
That's what I originally thought was a power issue, however, I experience this with new and old lipos. It's the oddest thing. It makes practice hovering in all orientations difficult obviously. I was wondering if anyone else has experienced this phenomenon.
 

D.O.G.

Goblin 380 Supporter
That's what I originally thought was a power issue, however, I experience this with new and old lipos. It's the oddest thing. It makes practice hovering in all orientations difficult obviously. I was wondering if anyone else has experienced this phenomenon.
OK then. I'm just guessing now. What's your +/- pitch on your blades? Good starting point is +10/-10
 

Crashnaz

New Member
OK then. I'm just guessing now. What's your +/- pitch on your blades? Good starting point is +10/-10
I will need to verify, I think it's 11°, I tried increasing the swash mix percentage from 60 to 75, hoping to get more response near mid stick, seemed to have the opposite effect. It's been a while since I have flown this heli it does have B stock cf align blades on it, gonna try a different set of cf blades and see if that changes anything
 

Tony

Staff member
First thing that came to mind when I read this is what is called Translational Lift. Basically it is how "clean" the air is going over the blades. If you have good clean air, you have good lift. If that clean air becomes dirty air, you have "not as much lift" resulting in a drop. This can happen with light and variable winds that move direction. Especially when in a stationary hover.
 

LoveRC

New Member
I have the same issue on my Blade 180 and 450 heli. Try different ESC. Solved the problem on mine. After I checked my throttle curve, pitch curve, replaced the motor, it came down to esc issue.
 

Crashnaz

New Member
That's an interesting thought about the esc, this past weekend I grounded the bird due to excessive play in mixing arm bearings, and also notice u/d movement in the main shaft bearings. Decided to rebuild the entire head. Will update after rebuild! Happy holidays
 

Smoggie

Well-Known Member
What's your experience level?.. If you are still learning then this could just be normal behavior that you have to get used to. Due to 'transitional lift' effects that Tony mentions, even quite light wind gusts will make the heli suddenly climb or descend. The effect is far more pronounced in small helis and you need to be constantly compensating to correct it.

If response to collective seems sluggish then it might be that your headspeed is too low.
 

LoveRC

New Member
That's an interesting thought about the esc, this past weekend I grounded the bird due to excessive play in mixing arm bearings, and also notice u/d movement in the main shaft bearings. Decided to rebuild the entire head. Will update after rebuild! Happy holidays
May I ask, which heli you having excessive play in the mixing arm and u/d on movement in the main shaft. Is it the same heli?
 

Crashnaz

New Member
What's your experience level?.. If you are still learning then this could just be normal behavior that you have to get used to. Due to 'transitional lift' effects that Tony mentions, even quite light wind gusts will make the heli suddenly climb or descend. The effect is far more pronounced in small helis and you need to be constantly compensating to correct it.

If response to collective seems sluggish then it might be that your headspeed is too low.
I figured out what was causing the altitude loss. It turned out to be worn out bearings in the washout base control arms, and the mixing arms. The slop translated to +/- 1° in pitch.
 

Crashnaz

New Member
Would be fantastic however I having trouble locating the replacement bearings

Trex 450 pro
FMR52ZZ(qty: 8)
681ZZ(qty: 4)
685ZZ(qty: 2)

Anybody know where I can obtain quality bearings?
 

Murray

Member
I had the same problem on my spectra-G ,during a pre flight check I had the rear elevator servo quit. I replaced the elevator servo and the problem quit something to look at if the other things don't work.
 
Top Bottom