trex drifting

[nyundrcov@aol.com]

Hey Guys need help,my trex 450 started turning to the left with out any rudder input.the initial setup was fine and flew pretty well.I'm ne to this ,could it be my gyro going bad or tail servo? gy401/ futuba s 9650

[Wolfpackin]

Vibration or low tail authority/headspeed due to weakening batteries.

Also, it's possible something is starting to slip in the tail system.

Is this a slow or fast drift and it's CCW, correct?

[nyundrcov@aol.com]

yes slow turn and ccw

[Wolfpackin]

Does it happen at the beginning of the battery?

Have you tried raising the gain?

I still think it's a vibration or headspeed issue but hard to say without more info.

[nyundrcov@aol.com]

It's happened a various times during flight i could be headspeed...if headspeed ha ould be remedy.funny thing is is was fine all along then started happening on sunday,bur progressively got worse

[Wolfpackin]

I was thinking that headspeed might have dropped due to a weakening battery and that's still a possibility.

Also, vibration due to a failing bearing can also cause gyro problems.

The reason I asked about raising gain is because even temperature and humidity changes can effect gyro hold.

So, I would do the easy stuff first.
Do some test flights and try raising the gyro gain and see if that makes a difference.
If not, try a new battery to see if maybe yours is weak and causing low headspeed and low tail authority.

After that it's pretty much a shot in the dark unless you have more info, but something might have changed in the tail setup.

[Pigskin]

Are you flying in rate mode or heading hold?

When my throttle curve was set too low I would notice weird stuff happening with the tail turning without any input. I only just got this nailed so it is fresh in my memory.

What was happening was that I was making slight adjustments to the throttle to change the height and suddenly the tail would swing about. After a while I noticed that the throttle pitch was changing at the same time too so I came to the conclusion that I had my throttle set too low and it sometimes got to the point where the throttle was too low to keep the tail authority, possibly also increasing any little rudder inputs I might have been giving at the time.

So I increased my throttle curve to give higher head speed and my jumpy/ erratic tail problems seem to have disappeared. I also found I could raise the gyro gain once I increased the head speed, which also helped alot with rock solid tail.

If it has suddenly started to happen I would recommend stop flying and going over your heli with a fine tooth comb, look for anything loose or out of shape. Have any of your wires moved about and introduced vibration into your gyro for example?

I almost learned the real hard way that any sudden change in behaviour of the heli could mean something has got loose. The other night I was flying at head height and noticed my blades were well out of track. Odd, I thought, as I've had no crashes and they tracked perfectly before. Anyway, at the end of the flight I checked the heli over and found that the bolts holding the blades to the feathering shaft were almost undone. I came very close to having the blades fly off in mid flight. I have since upped my pre flight checking process and also now do post flight checks. Glad I didn't have to pay the price of my inattention this time round though.

[nyundrcov@aol.com]

thanks guys I have done some checks and found tha my tail assembly has a lot of slop (movement) by me just moving the tail blades with my fingers .is this normal my impression is no am i right and could this be the possiblle cause.I will change the assembly back to stock until I replace the bearings on the upgrade.

[boriqua935]

check all the bolts on the entire bird, make sure they are tight and loctite. Any loosed bolts can cause vibrations that throw off gyro

[outhouse]

Originally Posted by nyundrcov@aol.com

Hey Guys need help,my trex 450 started turning to the left with out any rudder input.the initial setup was fine and flew pretty well.I'm ne to this ,could it be my gyro going bad or tail servo? gy401/ futuba s 9650

take main blades off and spool it up holding the boom, feel for vibrations.

drift= vibrations %95 of the time

[nyundrcov@aol.com]

thanks guys for all he input,your urgings to check everything paid off.It was the hole on the servo horn that was elongated,test flight was success.I'm now a firm believer it periodic maintenance