Trex 450 Sport Not flying straingt

[James A]

Hi, I've recently finished building my first Trex 450 Sport Combo and everything looked fine. When I did a first test flight I found the cyclic controls were somewhat off ie giving forward elevator would cause the heli to go forward and left. This error was about 30 degrees and is visible on all cyclic controls. I decided to relevel the swash and I believe it made a little difference but hasn't fixed things. If I push forward and start to get some pace it does seem to correct itself but I'm wondering if this is normal. I also have a blade sr and can confirm it doesn't have this issue although the head design is different.

The other thing I'm finding is it appears far more twitchy than my sr hence I'm wondering if I have errors in my build or whether I simply need more practice.

To give you an idea of my level, I have been flying for about 6 months and have just got nose in hovering (with training gear back on for this).

I guess one option is to try to a club and have it checked over but I'm not sure of any in the Guildford area.

Any help would be appreciated.

[Guest]

make sure you have your tx set up in 120 swash and not 90, i had same when i set my 450 up

paul

[heliboy]

Go to a club and have it checked over matey.

[bolders]

Have you levelled your swash at the top and bottom of travel as well as at centre stick.

Also I would expect the sport to be more responsive than the SR but you can soften the response with a bit of dual rate and expo and also flybar weights

[tourerjim]

Best way to be sure is to use swash leveling tool that way you can check to see if your getting any interaction between full neg zero & full pitch.

[Andy from Sandy]

My 450 sport needed alot of aileron and elevator trim to get it to hover hands off. Way more than I have ever used on any model. When I then went into forward flight it pitched up pretty bad.

On the bench everything was level and square.

Having converted it to FBL it now hovers hands off and flies forward as it should.

[Dudifiedad]

sounds like interactions.

Get a swashplate leveler that my help

[Andy from Sandy]

In the true sense of the word interaction is when you give elevator control you see the swash moving up and down. i.e there is some pitch component. Most people don't check for this.

On my own model the swash was level at mid stick and level at full positive and full negative when it had a flybar.

[James A]

Thanks for all the replies, I guess the main message is keep trying to level it better.

Thank fully I did get my swash plate leveling tool delivered yesterday evening and have rechecked the level at mid, low and high throttle. I have no subtrim on the pitch, a little on the aileron and a lot on the elevator (the servo arms supplied are one way and however i arranged them I could only really get the pitch and ailerons close to level without subtrim). I have set the level at low and high using the servo travel option.

Hopefully I will get a test flight this morning to try it out although I don't think it changed much. When I span it up on the floor with the training gear you could see the heli leaning back as I put full left aileron and leaning forward when I put full right.

One interesting thing I found when leveling was that the elevator servo doesn't always come back to the same position when moving either forward or backward. Maybe I'm being picky but it may be 0.5mm out until you then move in the opposite direction when it does then resettle at the level position.

Looking at the head, the servos arms are level at mid throttle, the swash is level and the arms above the swash are level as is the flybar cage. The push rods aren't entirely vertical at mid position so I guess I could move from the outer hole on the servo arm to the inner hole which would get these vertical and reduce the effective gearing on the servo, although the setup is as per the manual.

I guess I could iron it all out with swash plate mix on my DX8 although I'd prefer to get it as right mechanically as possible first.

By the way, does anyone have any settings for the DX8 with a Trex 450 Sport, I think I have it fairly right but when things don't appear to be going quite right you start questioning everything

Guess I just need to keep trying.

By the way

[James A]

Thanks for all the responses, I guess the main message is keep trying with the swash levelling.

Thankfully my swash leveling tool was delivered yesterday so I have been able to check the swash fully at mid, low and high throttle. All appears good although I no doubt changed things slightly. At mid throttle the servo arms are horizontal as are the swash, the bars above the swash and the flybar cage. The only thing I might change here are the servo push rods which aren't vertical but are setup as per the manual on the outer servo arm hole. This should reduce the gearing on the servo's which may reduce any twitches/errors coming in from the servos. I have found that the return position on the elevator servo isn't always bang on (pull back and let the stick return to the centre may leave the arm 0.5mm out, but this disappears after pushing in the opposite direction and allowing to return) although I'm not sure how worried I should be about this.

As far as subtrim goes both the Aileron and pitch servos levelled without needing much adjustment. The elevator needed about 30 as all servo arms supplied are one way only and I couldn't get it any better on that servo.

One thing I guess I could do is sort it out with swashplate mixing on my DX8 although I would preffer to get it mechanically right (or as near as possible) before going down this route. Any thoughts on this would be appreciated.

Once again thanks for all the replies.

[Gate88]

I have found that the return position on the elevator servo isn't always bang on (pull back and let the stick return to the centre may leave the arm 0.5mm out, but this disappears after pushing in the opposite direction and allowing to return) although I'm not sure how worried I should be about this.

It might be worth looking into thiss issue a little further, how does that servo behave if you put it under pressure, (ie rest a finger on it) it should be centering exactly as there's not a lot of travel on those cyclic servos and mm's do make a difference.
Its probably worth winding the servo horns up and down by hand a few times, (battery disconnected) just to make sure none of the servo gears have stripped. (They can be easily damaged during the build proccess)
Also check the speed of the servos, are they all moving together? You can get a level swash at top mid bottom but if one servo is slower than the others it causes problems when youre flying.

[James A]

When I drive the servo using the throttle it looks fine ie keeps track with the others. the issue comes in after using elevator and allowing it to centre, as I say go one way and it might not centre quite right, if you the go the other way it'll pull it back. I din't think it matters which way I go first. Perhaps it's due to having an elevator expo of 30 set in the radio.

Having just taken it for a quick test spin I think things on the directional flight may be somewhat better although it was fairly gusty so not really a scientific test.

One other problem I also noted is that on a couple of occasions (last flight being one) the tail would be holding well and then suddenly the heli turns by about 10 degrees anticlockwise. This happens very quickly ie like a twitch and it doesn't then come back to where it was it simply sticks on the new heading hold. watching the heli, I don't see the tail pitch changing although it happens in an instance. Having flown the heli through about 8 packs I have only seen this occur on 2 packs recently. I did rebind this time to see if that removed the issue but it didn't. I was wondering if it was due to slipping on the tail belt (maybe it has stretched since initial build and needs tightening) but I presume if that was the case it would pull itself back due to the gyro's heading hold so my fundamental thought is it's either the gyro or the radio throwing out a glitch. Any thoughts are again clearly appreciated.

[James A]

As an update on the tail kicking out and not returning to the original heading hold position. Having tightened the tail belt I ran another pack and the tail suddenly going 10 degrees anticlockwise appears to have stopped, so that's positive.

I'm also getting more used to the twitchy nature of the 450 and am hopefully improving pack by pack so fingers crossed I've managed to iron out most of the bugs.

Thanks for all the advise.

[James A]

Final update. Replaced the woodies I had been using (recommended by supplier) with the stock carbon blades which track perfectly without the need for different length push rods. Now everything is far more stable....or was at least before my first servo failure crash.