Question on heading hold in fast backward flight, 3GX on Trex 450

[dave21740]

I wasn't sure if this should go in this forum or the 450 forum, but I'll give it a shot here.

I entered into a vertical climb as I'd do in a stall turn, but instead of doing a 180 degree turn at the top, I let the heli descend tail first and leveled out flying backwards. As soon as I had it level and flying fast backward, the tail suddenly whipped around 180 degrees, and the heli was then flying forward.

The heli is a Trex 450, DFC head, stock motor and pinion, stock tail blades, Revolution main blades. I've got my gyro set at 35% (DX8 transmitter). At 45%, I get fast tail wag during fast fwd flight. The rudder locking gain adjustment on the 3GX is set to 75.

I'm not sure if I was expecting too much for the tail to hold at that speed, backwards, or if something is lacking in my setup. So, if anyone has any ideas, I'd appreciate them!

[dwdw910]

That sounds like a glitch in the matrix.. lol.

The 3GX has improved so much over the last few updates.. but it is known to be quirky and glitchy at times..

Aside from a glitch in electronics, I would check the center of gravity. If it is off- it can mess up the computations and cause flight correction errors.

[dave21740]

When I went to DFC, I did a double check on center of gravity and got it dead on, so I should be ok in that regard. That said, I'm going to do the triple check tonight in case I made a dumb mistake, for the first time ever

[HeliSmith]

You might try moving the tail servo ball in one hole if possible. Which servo?

[dave21740]

Checked the COG and it's good. FWIW, the tail servo ball is per Align's instructions, in the innermost hole. I checked the travel on the tail pitch slider in response to rotating the heli about the main shaft, and the slider goes the full range in both directions. It's a 450 Pro V2 tail pitch assy, forgot to mention that.

Backward flight is a problem area for me, which I'm working on. That's why it flipped me out when the heli seemed to instantaneously swap front and back ends...the orientation change wasn't from my command and it threw me off. Luckily I was 2 mistakes high at that point and only used up one of them getting straightened out

Edit: The servo is DS520, and the ball is in the innermost hole...I corrected the post. That's what I get for doing it from memory!

[bad007]

Need more info, backwards flight esp. when dropping backwards and leveling out and adding pitch the increased blade torque requires that the head speed be high enough to hold the tail. Holding the tail during backwards flight requires higher head speed than normal FF because of the weather vane effect. Also having the ball to far in on the servo horn will cause the mechanical gain of the tail to be to low and cause slow tail correction.

Originally Posted by dave21740

I wasn't sure if this should go in this forum or the 450 forum, but I'll give it a shot here.

I entered into a vertical climb as I'd do in a stall turn, but instead of doing a 180 degree turn at the top, I let the heli descend tail first and leveled out flying backwards. As soon as I had it level and flying fast backward, the tail suddenly whipped around 180 degrees, and the heli was then flying forward.

The heli is a Trex 450, DFC head, stock motor and pinion, stock tail blades, Revolution main blades. I've got my gyro set at 35% (DX8 transmitter). At 45%, I get fast tail wag during fast fwd flight. The rudder locking gain adjustment on the 3GX is set to 75.

I'm not sure if I was expecting too much for the tail to hold at that speed, backwards, or if something is lacking in my setup. So, if anyone has any ideas, I'd appreciate them!

[dave21740]

Originally Posted by bad007

Need more info, backwards flight esp. when dropping backwards and leveling out and adding pitch the increased blade torque requires that the head speed be high enough to hold the tail. Holding the tail during backwards flight requires higher head speed than normal FF because of the weather vane effect. Also having the ball to far in on the servo horn will cause the mechanical gain of the tail to be to low and cause slow tail correction.

I'll be getting back to the 450 soon. Have to replace a cyclic servo and a receiver stopped working, so that one's been on the bench for a few weeks and I've been flying the 500 and 600. You mentioned head speed, and I don't remember now if I was idle 1 or 2, so first thing I'll do when I get it ready for flight again is check tail setup, check rpm at idle 2, and then try it again to see what happens.

Sent from my SGH-T999 using Tapatalk 2

[bad007]

GM works best and must be >3300 for fast backwards flight. Don't forget the servo ball, to far in and the tail looses response, to far out and it will have to much mechanical gain resulting in a low gyro gain to stop the tail from wagging.
Something else I didn't mention was internal resistance and age of your batteries, leveling out like that loads it pretty good and if the pack isn't up to the task, head speed will drop and that's over 1000 rpm's loss on the tail for 250 in head speed.

Originally Posted by dave21740

I'll be getting back to the 450 soon. Have to replace a cyclic servo and a receiver stopped working, so that one's been on the bench for a few weeks and I've been flying the 500 and 600. You mentioned head speed, and I don't remember now if I was idle 1 or 2, so first thing I'll do when I get it ready for flight again is check tail setup, check rpm at idle 2, and then try it again to see what happens.

Sent from my SGH-T999 using Tapatalk 2

[Bonkievan]

@bad007,

Hey man, welcome back. The 3gx forum has missed you!

Hope all's well

[HeliSmith]

This thread was from March I'm surprised the op responded Fast backwards flight problems can also be just too much collective for the "fast" part and as stated loss in headspeed dramatically effects the tail. Although the smaller the heli the harder the gyro(s) have to work, faster and it tasks any unit to its extreme. A lot of adjustment time goes into my mini helis to get them to rock hard 3D, and yeah sometimes the gyro does something odd, rarely, but I am 6 years used to that stuff I simply correct.. Course I am pushing my helis as hard as they go

[dave21740]

Originally Posted by HeliSmith

This thread was from March I'm surprised the op responded

I still had notifications turned on for the thread. Plus, I had asked bad007 for his input in a PM, not being sure if he was still active here, and he very kindly let me know that he had responded in this thread...thanks, bad.

My 450 has been on the shelf for a while, with a few minor problems. The repairs have taken a backseat to flying my other helis, but I want to get back to it, reproduce the tail hold issue, and then see if it's head speed or ball position, which seem to be the two most likely causes. Or a combination of things, just as likely. My batteries are mid-life, at best, so I guess they might sag a bit when I've got a lot of collective in during that vertical to horizontal transition. I'll take a look at that too.

Field rep for AMain? Give them a thumbs up for me. I buy what I can locally, but the nearest shop with heli inventory is about 60 miles away so I've bought a lot from AMain as well

[HeliSmith]

Good to hear you're dusting off your mini heli the 450 served me well for many years. Once you get through the tweaking stage it will give you thousands of happy flights. Of course I mean with bearings lube/change as needed along with swapping out such wear parts as dampers, links and good a good cleaning regimen

True could be the packs.. The 3GX is ok, the newer ones are really nice with an updated chip but the older ones are also just fine. Sometimes if all else fails a nice DS95i or clone servo like KST fixes the problem.. But first you should exhaust all avenues.

Assuming you are the closest hole in on the tail servo horn and it is all 90° with gain off at center rudder stick then the servo is a bit under tasked we need to adjust. Playing with tail precomp first then finally tuning down the pitch response, or turning down maximum pitch are the common solutions. Definitely if it's a mini and you are not using the closest hole in the only reason for this should be because you can't get enough travel otherwise OR if you can't get it to wag or let go using very high gain with the ball in the closest hole in the tail servo horn. Then you move it out a hole and start over with low gain working up until it wags or lets go. Usually the closest hole in is correct, even my JR3500g liked the closest hole in on both my 450 Pro and the Warp 360. But I should say I am at very high headspeed using high output packs, smacking my helis silly


Off topic TLDR this, sorry guys
Thanks for the thumbs up to Amain I will definitely pass it along when I see my lead, Greggor, but as you know there's the exit survey's also. I like those exit survey's if I have an idea I pop it in, but I always rate them high. Also the live webchat I've had a survey after those, I have to admit the info I get through webchat surprises me at it's accuracy. A girl name Tegan can answer a question about a piston retaining clip for my OS91HZ motor in a snap, I order for pickup and have the parts in 15 minutes. But the reason I chose to be a rep is because if their reputation for covering the customer. I've seen lots of cases but there's in a incident with a power supply where they refunded duty tax, ate exchange rate loss, the whole nine.. They just ate the losses like it was tasty lunch. I heard local stories too and I am so happy to have been offered a chance to rep for them. I spend money there so I have great insight, I love them, makes sense for me to rep for them.. Hard to find problems but I've answered some questions or three..

I like other stores and that's ok that's another thing I love about Amain. I am a rep for Compass I love ProStar. HeliDirect has always been good to me, continue to be good to me.. But when it comes to a big purchase I buy from Amain tax and all, if so much as a screw looks funny they replace it no problemo.. I love that, I get an unscratched brand spanking new, defect free item, ever single time.. So I pay the tax, I get a slight discount now that almost covers tax. Heck I could save money buying elsewhere but let's face it I buy from Amain because I've had problems before but when I showed up there they only had solutions. You know I seen them take a kit apart for a piece for a customer the other day!! Guess they mark the kit open box and it sells fast enough, but who else does it?

Anyway yes I love Amain from their awesome down to earth flight team to their wonderful selection of products to their ultimately knowledgeable reps. Such as Jason Bell, Greggor McGrath and the entire flight team if a problem really got past those two.

Lastly I want to say I got my Warp 360 kit before I was a rep for Compass, Amain/ProTek, just on a deal they had. I bought it motor/blades/kit for 351 out the door with tax. Then they replaced my canopy for a small defect for free, I was going to keep it but they insisted. Always check with them at least by Webchat before pulling the trigger because at that time even paying tax it was the best price, free shipping, but I had local pickup. When the updated parts came in Amain called me that day and had them ready for me at the front desk..

So it seems I really talked up Amain, yes I love them best. I also like HeliDirect, ProStar is new but I like them a lot. I like RCHeliCanada though I don't order from them as I haven't economically been able to justify that, but I like the owner. I love HeliHobby.com they are small but the owner, David Shalem, is such an awesome human being. Honest been belief, loyal, funny, great to hang out with and was terrible hard to give a 6 month notice too. I do also like Readyheli, they are on the other coast from me and I never felt a close connection with them like the others. But they have never messed up an order for me and it's pretty quick under the circumstances.

[Coolice]

Hey.

On all the 450's I setup, I fit a small round servo disk with the control ball on the inner hole, what you lack in mechaical gain is very little compared to the gains achieved by being able to run a higher tail gyro gain, which then gives you more hold in fast backwards manouvers.

With the ESC, the Align govenor mode isn't all that good and from past experiences can actually cause tail problems, as the rpm control isn't smooth and tight, so rotor rpm drops as well as tail power. You're much better running in linear mode and setting a straight line throttle curve of 90 ~ 100% in your idle ups.

Have you set the 3GX mounting parameter, the "Anti Torque Compensation Direction" correctly? If not then this will not help as the torque reaction on the airframe is accounted for properly as collective pitch inputs are made.
.

[fluffhead]

you said you had a pro V2 tail assembly. if your tail grips are not weighted, then the servo has to work much harder especially in fast tail in manoeuvres (tennis racquet effect). if you want to do fast tail in, make sure you have weighted tail grips, and it makes sense to move the ball in on servo arm and turn gain up. that way servo works faster under less strain.

[dave21740]

Thanks to all for the recent replies. I'm certain I'll get it worked out now that I'm aware of all the factors which could be involved. I need to replace 2 servos and a satellite receiver to get it back into flying shape. I'll post the results when I get it solved, in case anyone is curious, but it may be a few weeks. I've got a close friend who needs a bit of help more than I need the 450 in the sky right now, so I'll be flying on a budget and hoping I don't do a nose plant over the next month or so with either of the bigger helis. Thanks again

[HeliSmith]

That's awesome you're putting down your heli to help your friend

[Jeff_Barrett]

Originally Posted by HeliSmith

I like RCHeliCanada though I don't order from them as I haven't economically been able to justify that, but I like the owner.

Thanks for the praise!

FWIW, we offer free shipping to anywhere in Canada & USA (Lower 48) on all orders over $100

[HeliSmith]

Originally Posted by Jeff_Barrett

Thanks for the praise!

FWIW, we offer free shipping to anywhere in Canada & USA (Lower 48) on all orders over $100

np Jeff and thanks for letting me know on the shipping I was eyeing the 6s 1500 reactor packs for my Warp. I need packs waiting on budget, family guy same ol story. Ah nicely on my mind now lol

[Jeff_Barrett]

Originally Posted by HeliSmith

np Jeff and thanks for letting me know on the shipping I was eyeing the 6s 1500 reactor packs for my Warp. I need packs waiting on budget, family guy same ol story. Ah nicely on my mind now lol

Email me first regarding lipos and shipping to the USA ... it's a bit tricky due to laws / restrictions on lipos these days.

[HeliSmith]

Originally Posted by Jeff_Barrett

Email me first regarding lipos and shipping to the USA ... it's a bit tricky due to laws / restrictions on lipos these days.

Ok will do thx Jeff