Post trim flight question

[Miracle Boy]

Hey guys,

I have a second hand Chase 360 which I've just finished re-building. I put a VX1e on it and the stock KDS N320T servo on the tail.

Today I did the first trim flight I've ever done, as I've never felt the need to carry out a trim flight until now, be that with v3 or v4 firmware, but the tail on my Chase 360 does not hold well at all during pitch pumps, so I decided to give a trim flight a go.

The flight trim results were:-

0.16 L
0.05 B
+45 uS on the tail.

The tail holds better after the trim flight, but on occasions the tail will still blow out as much as 50% on hard pumps.

I realize the 45 uS on the tail isn't brilliant, but surely I' shouldn't be seeing such extreme blow outs with those figures?

I'm tempted to just assume that the KDS N320T tail servo (which like the heli, is second hand) is just not up to the job, but I'd be interested in what you guys think?

I'm running about 11.5° of pitch, not sure at all about the HS though, but a flat 72% curve on HW 50A v3 in Gov store with a Scorpion 1880kV 2520 motor. tail gain is set to 35 IIRC.

Perhaps my HS is too low, but it's got plenty of pop at that HS, so I don't think that's the problem.

Oh, I should also state that I'm using Align 67mm plastic tail blades from the 450L, and the numbers I got when doing tail set up are 85 and 120.

MB

[myxiplx]

The trim flight will help stops, but doesn't have any significant effect on tail holding. And regardless, if it's blowing out that much you're exceeding what the tail is physically able to do.

That means you either need bigger tail blades (but 67mm is pretty good), or more tail pitch, or more headspeed, or the servo is knackered :-)

In theory your hardware should be fine, so my first question is what headspeed are you running? Headspeed affects the tail much more significantly than the head, so low headspeed can still handle fine on cyclic and collective, but the tail can struggle to hold.

Check your headspeed, and see if higher throttle helps.

Also, a flat curve isn't going to perform the best, you want a V if you're using curves, or a governor enabled to hold headspeed. If the headspeed is sagging in these moves that again has a significant effect on tail holding ability.

[Miracle Boy]

Hi Ross,

I'm using the "Gov Store" option on the HW 50A ESC, so I think it's designed to use flat curves.

I've never had a tail hold issue this bad before, though I have since adjusted the push rod guides a bit to see if that will help, but I've yet to try it out.

The N320T servo is a bit suspect to me, it's not the smoothest (gears are a bit noisy) and I have no idea about it's history before I got it.

I just downloaded the HS tacho app for my phone last night, so I'll do a hover over that so I can get a better idea of what HS I'm actually running, but like I said, it has plenty of pop with 11.5° of max collective pitch, so I don't think that's the problem. If I raise the tail gain any further I get a HF wag, so I can't go any higher.

MB

[PowerDyne]

Originally Posted by Miracle Boy

Hi Ross,

I'm using the "Gov Store" option on the HW 50A ESC, so I think it's designed to use flat curves.

I've never had a tail hold issue this bad before, though I have since adjusted the push rod guides a bit to see if that will help, but I've yet to try it out.

The N320T servo is a bit suspect to me, it's not the smoothest (gears are a bit noisy) and I have no idea about it's history before I got it.

I just downloaded the HS tacho app for my phone last night, so I'll do a hover over that so I can get a better idea of what HS I'm actually running, but like I said, it has plenty of pop with 11.5° of max collective pitch, so I don't think that's the problem. If I raise the tail gain any further I get a HF wag, so I can't go any higher.

MB

Are you using flight modes? Even with the Spartan governor off, and using flight modes on the Vortex with your ESC gov, it's recommended to still set your Rotor RPM per flight mode to match approximately the RPM you are aiming to run using your ESC governor. This way the Vortex has an easier time compensating on cyclic, collective, and tail.

[Miracle Boy]

Originally Posted by PowerDyne

Are you using flight modes? Even with the Spartan governor off, and using flight modes on the Vortex with your ESC gov, it's recommended to still set your Rotor RPM per flight mode to match approximately the RPM you are aiming to run using your ESC governor. This way the Vortex has an easier time compensating on cyclic, collective, and tail.

Yes, I am using flight modes. When I'm doing setup after a new build, I set up my 3 flight modes on an independent switch to my IU switch, with different tail gains to try each of them at different headspeeds. I messed around with numerous tails gains and a number of different headspeeds, but no matter what, I coudn't get the tail dialed in.

I've bought a MKS 95i (used) to try on the tail, but the lead wire is a little too short to reach the Vortex comfortably, so I need to replace the lead wire before I can try it out. I'm waiting on the new wire coming in the mail.

MB

[Miracle Boy]

Just an update on this.

I finally rewired the 95i I bought (used) with a longer lead on it and fitted it to the Chase 360.

The 95i has cured the tail hold issue I had previously with the KDS servo, still got a bit of dialing it to do on the tail, I did another trim flight and got

A:- 0.00°
E:- 0.00°
Tail:- +48uS

TBH I'm a bit confused by that, you'd think it would just sit there in hover for ever with a perfect score on cyclic, but it seems to me that it needed a bit of left aileron and back elevator to keep it from floating off.

MB

[sc00bied00]

How is the CoG, nose heavy? might account for the elevator input, right drift not so sure, could be torque from motor/blade rotation?

Have you tried another trim flight to see if you get any more stability....

[Miracle Boy]

CoG is good, but I have to say that the Chase 360 seems to lean more to the right in a tail in hover than any other 450 (325mm - 380mm) heli I've ever had.

I have no idea why that is. The swash is level on the bench, and the blade tracking is bang on. It doesn't seem to be an issue in flight, but it does make it difficult to complete a trim flight when it want's to float off all the time, particularly if trying to do a trim flight indoors (in a bigish gym hall) cause it's too windy to fly outside.

MB

[myxiplx]

Yeah, a trim flight does need some room. If it's floating off, check you don't have any trims on the TX, but if you're confident in the CG then personally I would adjust the links a fraction to correct that drift you're seeing.

That's all you would do anyway after a trim flight, and you clearly know which way it's drifting :-)

[Miracle Boy]

O.K. thanks Ross. TBH It's not enough of an issue to bother about. It seems to fly o.k., it might even be just me that's the issue, the heli tilts that much it makes a stable hover look wrong somehow

MB

[myxiplx]

Heh, yup, can't get away from the tilt, every heli does it :-)

[sc00bied00]

I did a trim flight after replacing battery try, heli was drifting forward and left, tray was replaced as one of the rear landing gear mountings screws had sheared, must have torqued it too much, I tried drilling out the screw but that was a waste of time. I did that on the bench hei upside down. When I got home I checked the feathering shaft and found one side had a very small amount of movement at the blade arm, so suspect my drilling out the bolt must have bent the shaft. I didnt think I was using much pressure as I was using 0.5mm drill bit. Really surprised that the shaft seems to have bent ... thought it was more robust than that, reminiscent of the blade 300x head....

[Miracle Boy]

Originally Posted by myxiplx

Heh, yup, can't get away from the tilt, every heli does it :-)

Had the Chase 360 out for it's first proper flight outside w/o too much wind making me nervous. You know what, the Chase 360 really does live up to it's reputation. If you want a really agile 360mm blade heli, buy a Chase 360.

That said, parts quality is extremely hit or miss, if it wasn't for the poor parts quality, the Chase 360 would be a very popular model. It's a shame KDS can't seem to sort out their QC issues.

MB

[Miracle Boy]

Originally Posted by sc00bied00

I did a trim flight after replacing battery try, heli was drifting forward and left, tray was replaced as one of the rear landing gear mountings screws had sheared, must have torqued it too much, I tried drilling out the screw but that was a waste of time. I did that on the bench hei upside down. When I got home I checked the feathering shaft and found one side had a very small amount of movement at the blade arm, so suspect my drilling out the bolt must have bent the shaft. I didnt think I was using much pressure as I was using 0.5mm drill bit. Really surprised that the shaft seems to have bent ... thought it was more robust than that, reminiscent of the blade 300x head....

What heli are we talking about here? Your G380?

MB

[sc00bied00]

Yes 380... sorry MB late reply

[Miracle Boy]

Originally Posted by sc00bied00

Yes 380... sorry MB late reply

I've not crashed my G380, but I have read that SAB metal parts are a bit on the soft side, particularly when they are quite expensive to replace.

MB

[sc00bied00]

Thanks for that, feathering shaft is on £6/7 so doesn't break the bank, just rather surprised. One could feel the difference from the previous flight, I'm still really novice but in comparison to the spektrum fbl I was really surprised at how much was fed back or 'feel' at the sticks. I was also pleased to find that the VX1 had survived the issue I had with the YGE ESC as I thought it may have sustained damage, thanks for your feedback.

Quick Q - I'm not running the latest firmware (m5_3v00) and I noted on the short flights I had, tail wag was present, this could be due to lack of 'run in' of the tail has had but I don't want to make things any worse if the latest firmware is more sensitive to mechanical issues, so what's your thoughts?
TIA

C.

[Miracle Boy]

Originally Posted by sc00bied00

Quick Q - I'm not running the latest firmware (m5_3v00) and I noted on the short flights I had, tail wag was present, this could be due to lack of 'run in' of the tail has had but I don't want to make things any worse if the latest firmware is more sensitive to mechanical issues, so what's your thoughts?
TIA

C.

Well, Myxiplx would be a better person to ask about this TBH. When I built my G380 I had a new Vx1n to go on it and updated the FW to M6 at that time, so I can't comment of any differences in tail performance.

I can say that I have 5 Vortex units in use at this time and 3 of them are still on M5 firmware as they work just fine as they are, so I felt no need to update them to M6. If it ain't broke, don't fix it!!

The other 2 units were installed in helis built after M6 FW was released, so I updated them to M6 before putting the units in the helis.

A tail wag can be caused by a lot of things.......

Firstly, let everything bed in with a few more flights, and if the tail wag persists, you need to check a few things out.

Look at how smoothly your tail pitch slider moves. It must be buttery smooth.

What tail gain settings are you using? Are you running a high enough head speed? If the HS is too low, that can cause a wag too.

What numbers did you get when you did your tail set up on the Vortex?

i.e. 110 and 90, 140 and 100? Basically, you want those to numbers to add up to as close to 200 as you can get for best tail performance.

See this Bert Kammerer vid bellow and particularly the tail section at 22:23 :-

https://www.youtube.com/watch?v=JcjM...MScyo774YQZ3OV

MB

[myxiplx]

What kind of wag are we talking? Is it a slow wag in a hover, a fast chatter heard under harder flight?

[sc00bied00]

Guy's thanks for your replies, caught up with house and family.

MB - did what bert advised before maiden, figures from memory were about 180/190. I'll leave the update until i see if I can sort out the current wag. I'yet to order a new feathering shaft, and will recheck the tail throws when setting the head back up, im also running the smaller tail gear, stock main gear, no gov but using fixed throttle percentages for idle up 1&2 in radio. Hobbywing v3 100 esc, have only used IU 1 which should be around 2600 - 2800rpm.

Myxiplx - slow wag is what I noted, i was not able to get a steady enough hover due to the feathering shaft so no trim flight info, heli was constantly drifting off, had a pretty wind free evening when I did this...

Once I replace the shaft and set back up I'll come back to this thread for your advice, have a fair bit of work in house to do and will be limited in time just now, thanks again
C.