AH-6Z Littlebird Night-Ops build project

[Zeeflyboy]

Lol...

It's a good radio! I have no qualms about using it. The audio quality is a bit shit, I compared it to another guy's and mine seems to be especially bad for some reason -  I have ordered an upgraded speaker and have been reading up on speaker mods for it, hopefully that will solve the issue.

So good news is that my friend should be able to come help me with the heli - hopefully that means some video.

Also, Juan has been in for some shoulder surgery... I wasn't happy with how the arms were sitting so shortened the shoulder width a little. He looks better now methinks.






And I just designed and printed up this little M4 spanner doo-hickey - perfect for nipping up those blade bolts quickly!

[Zeeflyboy]

Things did not go well. Not well at all - Took off and it was like trying to ride a rodeo bull. I have not yet figured out what was wrong... All control directions were correct, all automatic corrections were in the correct sense, it was just almost impossible to fly.


Ace One test does not go well


Basically initially it just felt incredibly unstable which suggests to me gyro gains that were way too low so as to render themselves insignificant. I could just about keep it in the air until the tail turned under the torque of a heavy elevator input turning it uncommanded and then it was game over and I decided it was time to give up rather than decapitate myself or my friend... smack, thud, whine of stripped teeth.

Pre-flight I check all control surfaces move in the correct sense, and that was borne out by the fact my corrections did go in the right sense. I also check that the gyros compensated in the correct sense and that too is borne out by the fact that it didn't just flip as it would have were they incorrect. So everything checks out in that regard. Mechs I know were fine, that's plain to see... for aileron the blades over the tail and nose moved, for elevator the blades at 90 degrees to the boom moved. Exactly how it should be. That only leaves the IMU and its associated settings to dive into.

Here's some pics of the damage that is plain to see, inspecting the rest will take time and at the moment obviously I can't be arsed:

Main gear stripped because I was a too slow on throttle hold (idiot)...




Landing skid snapped... not bothered by that, was going to get some taller skids anyway.




Tail is a complete mess... You can see the main unit has separated from the 6-5mm step down... That was sleeve locked AND fastened with a grub screw with loctite so I can't imagine it came loose in flight. Tail shaft is bent, I haven't examined the blades yet - I'm just assuming they are toast from all the mud lol. Thankfully the fibreglass tail seems unscathed.




The only main blade showing damage:




and the m2 screws that acted as fuses and hopefully saved my head and servos:




I think the only way forward is to increase the gains and construct some training gear to do some low level hovering over tarmac. If it starts wallowing it can just be dumped knowing that it won't (shouldn't) tip due to the training gear.


So far the repair bill is looking:

- 4 x Tail blades........................... £50
- 5 x main blades......................... £180
- Main shaft (precautionary).......... £12
- Tail shaft.................................. £9
- Boom...................................... £15
- Torque tube.............................. £10
- Skids....................................... £15
- KDE Main gear.......................... £25

Total cost about £316 ($510) = ouchies....and that's just what I know about. I hope the head is not damaged.... looks like christmas is cancelled this year :(

[iwan_canobi]

Ouch! Can't imagine how gutted you must feel right now, that repair bill is certainly hard to stomach!

Hopefully you can get to the route of the problem quickly, I suppose a little mercy is that you didn't have the fuselage and cockpit installed at the time!

:(

[Zeeflyboy]

Yeah it sucks, but what is really annoying is not knowing the cause.

If you crash and then you realise you did something wrong, that's fine. You swear, you call yourself an idiot and then you rebuild it and put it back in the air.

If you crash and don't know why, you rebuild it and then? If you try to fly again you will get the same result, so you try changing something... Eg the gains. But what happens if that wasn't the reason?

THAT is what has me vexed, more so than the crash itself.

[Coyote]

Oh dear, I feel for you, like you say, a known problem can be addressed, an unknown one leaves you with no options to fix it

[Mudders]

Nasty, that sucks matey. I know that 'unknown issue' feeling and it's not nice.

I hope you get it sorted.

Muds

[DaveyLC]

OUCH!  :o that's not good buddy :(


...I blame the Turdanis! :D  :P

[CurryKitten]

Damn, that was a shame - heli blades are a lot  :o

Last time you flew, electronically things were much the same weren't they (at least in terms of the flight control systems) - and back then there was just a little tail wag to sort out.  I can see why it would be tough to just rebuild and hope it's a gain twiddle.  I hope you can get some concrete theories on what the issue was.

[skyscraper]

Ow.. sorry to hear that. Know some of the pain since I just stuffed in my plane that I put a lot into (but not as much as you have into this one).

A few days off building to philosophize sounds fair enough.

Ideally a sim , but I only know of the ardupilot ones http://code.google.com/p/arducopter/wiki/ArduCopter2SIM Might be  a starting point though

regards
Andy

[Ratty]

Nooooo, sorry to see it didn't go to well. Although pricey, the damage isn't as bad as it could of been for a heli. As im sure you know, they generally don't crash lightly.

Was that last test flight done on the same Tx? So only the firmware had changed?

Maybe check the rates? I cant really tell from the vid but it looked pretty twitchy as well as unstable.

Like you say, some kind of training gear and an big smooth open space should save that happening again tho.

Good luck and keep the faith. We all want to see this beast fly, but I bet you want to see it more than all of us.  ;D

[Zeeflyboy]

Yeah... Assuming the head is okay then the damage could have been much worse - biggest cost is just the blades.


So I've sat down the bank manager and had a chat... Almost all my replacement parts are now enroute, just need to find the KDE 164t main gear in stock and buy/build some training gear for Ace One testing.

I haven't yet verified if there is any crash damage with the head, need to take a look at that next... I will also play around with the gains and cyclic rates to see how much the swash reaction to movement changes. After much thinking and watching of that depressing video it's all I can come up with for a reason.

I also bought some thunder tiger PV6008 MD500 landing gear rather than replace the align bollocks. The PV6008 has a couple of advantages - much stronger (obvious benefit with 7kg of heli), much taller (about the same height as the mechs will be once installed in the fuselage - much improved tail clearance), and should my plastic landing gear in the AH ever give up the ghost, these could be a potential replacement.

FPVflyer (who sold me the Ace One) couldn't believe it when he heard. He wants to come over with his 600 SAR rig that is soon to be retired and use it as a sacrificial guinea pig to check the Ace One out.

[FPVSteve]

Ah man that was sickening to watch.

I hope the damage is minimal with the head and you can get her back in the air without too much agro.

Sorry to see mate, chin up.

[Zeeflyboy]

Ow.. sorry to hear that. Know some of the pain since I just stuffed in my plane that I put a lot into (but not as much as you have into this one).

A few days off building to philosophize sounds fair enough.

Ideally a sim , but I only know of the ardupilot ones http://code.google.com/p/arducopter/wiki/ArduCopter2SIM Might be  a starting point though

regards
Andy

Wow, never knew that sort of thing existed... Cool!

Unfortunately I don't think there is one for 7kg 5 blade Helis with Ace One fitted lol... Training gear is about my only testing option I think.


Steve - all replacement parts now ordered and the head is looking okay from my first look. My wallet is lighter but the bitch will get back in the air.

[Zeeflyboy]

So I've been studying the Ace One manual again...

While the suggested default gains for a T-rex 600 are 100/100, if you look at a logo 700 in the table the recommended gains are 150/160 or a maxi Joker 3DD is all the way up at 200/250... Other parameters such as direct input and flybar weight are also double or more the values of a 600 when you look at the Joker recommendations.

Since my heli is far heavier than a "normal" 600 and running a much lower headspeed, I guess it likely has more in common with a Logo 700, in fact more like the Maxi Joker 3DD as regards the gain requirement.

That gives me hope that this was a simple gain issue. I was running the default 100/100 and if it does indeed need something closer to the maxi joker then that is, one assumes, a potentially huge difference in gain. This does fit with the observations, which were that it was like flying without a gyro... If the gains needed to be over 200 and were at 100 then  that could certainly explain some stuff.

However I'm not really up for smashing another €260 worth of blades and whatever else along with it, so will proceed with caution... I've now ordered all replacement parts and some large 550-700 size training gear. Hopefully all these bits will start arriving next week and I can start putting Littlebird back together.

[Zeeflyboy]

I'm a bit stuck now of course waiting for parts, I could work on the fuselage and cockpit but at the moment I'm still licking my wounds so to speak. Will pick up again next week with some new motivation hopefully.

In the mean time I decided to do something else... About time I started doing a bit of work on the ground station I started a way back!

First job, wire up the locking connector that will attach the Rx/AAT and fit the IMRC powerbox that will form the backbone of the GS... So 3S goes to the PowerBox which outputs 4 filtered feeds. One goes to the screen, one goes to pins 1/2 on the 6 pin locking connector for rx, one goes to pins 3/4 for AAT power (servos etc) and one will go to the DVR.






On top of that I have video and one audio channel from pins 5/6 of the locking connector going to the powerbox. One will go to the DVR which will then pass through to the screen, and two will go to goggle connectors 1&2, with the 4th going to a 25mw 5.8ghz vTX for wireless relay.

And here you can see the underside of the bottom plate. Power goes via a main power switch to a voltmeter/ammeter and from there it will go to the powerbox and goggles. You can also see the speaker I pulled from the monitor while disassembling it, this will play audio from the aircraft.