Last 5% of setup - flight tests

[nyc863]

I only know a few things to try in flight to make sure my Vbar setup is optimal.

updated for 5.0

I'm assuming you can already hover your v-bar heli with precision, if you are fighting to hover with vertical precision you have bigger and more traditional setup issues to solve than v-bar software settings. I'm assuming also the heli isn't vibrating excessively, usually the whole tail fin will exhibit any excessive vibration.

Prelude: Vibration
The transition to 5.0 revealed to me just how much vibration can throw out 4.0 accuracy without the vibe being obvious to the pilot. 5.0 is much more vibration immune than 4.0 so upgrading a 4.0 vibrating heli to 5.0 can make it fly much better without any other change! But 5.0 also has better vibration reporting. So your first step with 5.0 is to check if excessive vibration is reaching the sensor. Unfortunately 5.0 Pro is required for two critical vibration tools: flight log and spectrum analysis. After your maiden flight review the flight log from the v-bar software (menu "Info.." "Event log" "Get last 100 entries"). If you have any of the yellow or red vibration alerts you need to chase vibration. This subject is so big look for existing topics in this forum on it. Suffice to say that the most common sources are unbalanced tail blades, unbalanced rotor blades or previous mechanical damage or wear to spindles, axles. Also gears that are meshing without any slop can add vibe. Finding where this vibe is can be done by elimination of much rotating parts (removal!) run up, and measure, then add back one by one re-measuring each time.

Field tests:

1: do increasingly aggressive vertical ascents and make sure that the heli doesn't rear back due to tail drag, or pitch forward (ie: make sure the boom is level to the eye). The fix is to increase/decrease the tail elevator pre-comp which counters tail drag. If the elevator tipping is worse at full pitch vs mid power ascents, then consider if you really have level swash at max pitch (and min pitch).

2: from flat, pull the heli over onto its back with just elevator then either punch away from you, or continue the rotation back to where you were originally, does everything stay in line with your eyes. Make sure not to give any accidental aileron. The fix is to check mechanical phase is correct or to adjust software phase. See the next step.

3. Hover above ground effect tail in and get it sitting at a spot (you can do this in a steady wind), then smoothly rotate 90 degrees to the right without any other input. Does the heli start un-commanded forward flight? If so you need some swash rotation. On a heli with rear elevator servo and front cyclic servos, using the control panel, go to "swash rotation" and rotate the swash 2 degrees by turning the control wheel in the direction the heli moved. Eg, if it moves right, turn it right so it indicates 2 degrees. No need for reboot, just remove the panel and take off again and do the same thing. Is it worse, or better or even reversed? Remembering where you are from 0 (now +2 degrees), either add or subtract more. Within ~5 degrees you should find you can piro on the spot from a stable hover to any compass position without any un-commanded flight. Getting this right is the difference between a great flying machine ("like a sim!") and a sloppy one. The auto-trim flight also does this adjustment but do you ever have a real windless day? I prefer to do it manually. If phasing isn't right a slow piro while hover will nod the heli (and if you stop at the nod it will start forward or reverse flight). Even if mechanically phasing looks perfect, can you spot a 3 degree error? I can't.

4: on a windless day take off and hover then stop giving cyclic corrections. Does the heli move off purposefully in any direction? is it the same direction each time? The fix is ensure level swash first, then auto-trim flight, and good CG. If the direction is random, the source of the problem is likely to be vibration.

5: Do some pitch pumps, is the tail locked entirely, or does it react a bit late and then recover. If it reacts a bit late then recovers, check and change collective pre-comp.

6. Do some CW and CCW piro sudden stops, do they feel identical (stop just as fast)? change stop gain A and B if not. added: also do FFF then piro at full speed, both CW and CCW, is there any tail authority loss vs doing it stationary.

7. Do FFF and then piro slowly into the prevailing wind on either side or... fly fast away from you and go into a high fast banking turn and during the turn, piro the tail faster than the turn -- so it should move smoothly into the wind. Does the tail struggle, or oscillate during the move or even just make a sound like buzz..buzz..buzz .? if reducing tail gain doesn't help or removes too much of the pinpoint tail stop behavior you want, then the fix is to focus on the entire tail system: servo, servo arm length, slop, pitch slider, maximum slider movement, tail blade length, head speed, tail rod clamp .. etc etc.

8. Do some full pitch moves, does the heli bog, especially near the end of the pack, if so consider reducing pitch.

9. Do some fast sudden turns at the end of a forward flight, does the heli bog or the blades stall? consider reducing CG (cyclic gain).

10. Do continuous full pitch aileron flips and elevator flips. You should do this with the agility optimizer on to let the v-bar try to find the adjustments to make flip speed the same in both directions. After you've had one flight with some full pitch flips, the optimizer will have selected some numbers, so turn it off.
If it is flipping too fast, reduce agility and/or cyclic gain, re-check optimizer, and start again.

So what other in-flight tests can one do that can highlight a setting that might need tuning?

[Penguin]

I can see this turning into a very educational thread. Great start! I'm subscribing.

I would add to Tip 3 to check piro compensation direction. I somehow missed that on my last vbar setup (my third vbar system). It's real easy to miss a small step somewhere but it was very easy to detect something was wrong when doing the slow to moderate stationary piro test. Heli was wandering all over the place compared to my other two vbar helis.

[Slyster]

wow.. I am subscribing too

NYC.. maybe you could edit your post to add things as people post their additions?

[ADHDJeff]

Another test I usually perform is to get the heli moving at moderately fast, level, forward-flight then (without changing cyclic or collective) apply full rudder for a few piros. The piro speed should be consistent from start to finish and consistent in both the left and right direction.

[Slyster]

anyone have more to add to this "trouble shooting" thread? Good stuff here. I am going to bookmark it and add it to the various heli bibles.

[trippergreenfeet]

Some ponits to add to Step 10: Using ATV to equilise flip/roll rate.

If flips or rolls are faster in one direction than the other, ATV's can be used to even up the flip/roll speed.

Pick the particular flip/roll direction rate that is best suited to you and use that as the benchmark for the other flip/roll rates.

Raising ATV will increase speed, lowering ATV will decrease speed.

[pgleesonuk]

Please can I clarify test 3.

In my case, if I piro to the right the heli starts to more forward but kinda drifting to the left.
If I piro to the left the heli starts to move backward and to the left.

Which way should I rotate the swash?

Thanks, Paul

[g-bru]

From what I have read, I would say rotate the swash left bud..............

Like NYC863 says, if its worse simply rotate back the opposite direction.

Good luck.

G.

[Zaaaguy72]

How much do you guys normally increase the Main Rotor gain over the initial settings? What is the best way to know if the Main Rotor gain is correct?

How many flights before you turn off cyclic and tail optimizers?

[DRM Black7]

Great sticky, I've found with my O550 in full speed flight the cyclic becomes very sensitive! Any pointers?

[KingofQueens]

Originally Posted by DRM Black7

Great sticky, I've found with my O550 in full speed flight the cyclic becomes very sensitive! Any pointers?

Usually it is the elevator, which gets very sensitive.
I just raised my expo on that.

[bostonkiter]

PLEASE PLEASE PLEASE STICKYDIFY THIS!!

[DRM Black7]

I kinda don't want to add elev expo as through normal flight it's perfect might have to fly around the problem

[Lipper]

This is a stcky candidate for sure.

[Patriek]

I thought that this thread used to be a sticky?

Originally Posted by nyc863

3. Hover above ground effect tail in and get it sitting at a spot (you can do this in a steady wind), then smoothly rotate 90 degrees to the right without any other input. Does the heli start un-commanded forward flight? If so you need some swash rotation. On a heli with rear elevator servo and front cyclic servos, using the control panel, go to "swash rotation" and rotate the swash 2 degrees by turning the control wheel in the direction the heli moved. Eg, if it moves right, turn it right so it indicates 2 degrees. No need for reboot, just remove the panel and take off again and do the same thing. Is it worse, or better or even reversed? Remembering where you are from 0 (now +2 degrees), either add or subtract more. Within ~5 degrees you should find you can piro on the spot from a stable hover to any compass position without any un-commanded flight. Getting this right is the difference between a great flying machine ("like a sim!") and a sloppy one. The auto-trim flight also does this adjustment but do you ever have a real windless day? I prefer to do it manually. If phasing isn't right a slow piro while hover will nod the heli (and if you stop at the nod it will start forward or reverse flight). Even if mechanically phasing looks perfect, can you spot a 3 degree error? I can't.

Anyway - a question regarding rotating swash direction.

T-rex 600ESP (front ELE, rear AIL), when turning the machine 90 degrees to the right, its wants to veer off to the back/ left a bit. So should I turn the swash 3 dgrees or so to the left? Is that correct? A bit confused since the ELE/ AIL is reversed from what the author explained.

(I cannot bring a laptop to the field so, please try to explain why and which way one should rotate the swash in a direction)


-Patriek

[fbdave]

Trying to tune my mini vbar on my trex 500. When I do continuous aileron roles right, by tail drops. When I do continuous aileron roles left, my tail rises.

What's the issue here?

[scoti333]

Originally Posted by DRM Black7

I kinda don't want to add elev expo as through normal flight it's perfect might have to fly around the problem

Program a dual rate for FFF. This is what I do on my Shape, at 120mph the elevator gets VERY sensitive so I just flip on the dual rate before a high speed pass... Or use bank switching. I actually use a combo of both dual rates and banks for different flying styles.

[scoti333]

Originally Posted by fbdave

Trying to tune my mini vbar on my trex 500. When I do continuous aileron roles right, by tail drops. When I do continuous aileron roles left, my tail rises.

What's the issue here?

Elevator precomp. Have you tried adjusting this?

[carlocivicsi]

I just finished setting up the mini vbar,,, and under cyclic I set it to be 8 degrees(like it says on the program) and when I'm DONE with the setup,, cyclic goes to between 17 and 20 degrees when i feed left and right aileron. why is that???????

How do I adjust cyclic pitch on the vbar after setup? With dr rates menu on my dx8?

IN ALING 3gx in dir mode you setup the cyclic and after setup you don't get the crazy 17-20 degrees like in vbar.

please help.

Thanks for the help. Very much appreciated.

ps I'm using the express software.

[Zaaaguy72]

Dont worry about what the cyclic rates are when you are not in program mode, just go fly it and see what you think. Make sure to run the cyclic optimizer on your first flight, then turn it off afterwards. To increase or decrease the cyclic rates after initial setup, increase or decrease the Agility Slider on the main menu of the vbar software.