Comp arf Superextra crash

[Mithrandir]

If it didn't flutter... the inadequate servos are not the reason for the failure. Even weak servos will dampen a flutter as long as the gear train is intact..... were the servo gears stripped???... I can see stripped servo gears causing the problem.
The failure you show is not one I have previously seen on a Compy... also... (perhaps not relavent).. that is an old SX.. Blade Spar....

Even if you had irrefutable evidence that a manufacturing flaw caused the crash... signed affidavits by 13 tibetan monks... I don't think you will get anywhere with Comp-Arf... the owner is a bit...ummmm... arrogant. I am aware of other instances where he clearly made an error not consistant with what the customer paid EXTRA for.. (A lot extra!!!) and he basically blew the guy off and did not fix the problem. It hurts me to say this because I have good friends who are compy distributers.. and I hate to hurt their business... but maybe a little pain for Comp-Arf will change how he (Andreas) does business???

[cyco]

of course the 5945 is the fault !!! -everybody knows that hitecs dont have the holding strenght, they are weak at the zero points.

2 till 3 5955tg would be enough for that plane or Ds 8511/8711....

but that stands all in the manuals.

Regards,Chris

[Doc. insane]

Thanks for the feedback,

I have to agree about the weakness of 2 HS5645MG's in this setup, but taking his style of flying in account this shouldn't have been the main reason for this crash. He flew his first superextra with the same setup for more than a year and never had any trouble, concerning the ailerons. His first one crashed due to a 3W smokepump which kinda freaked out suddenly pulling 15 amps, burning his gear. It's really sad to see his second superextra crash after only ten flights. I'll ask him what servo's were adviced in the manual when he built the plane, but I still have to agree you can never put strong enough servo's in a plane this size. I still don't like the construction method of the aileron hinge though. The bonding between the rhoecell foam and the skin is just to weak, making it very sensitive to crack initiation. This fact in combination with a weaker servo setup makes planes like this crash.

[Stu_D]

Have to agree with everyone 5645 should never see the light of day when it comes to very large planes . I also want to know what made him crash , one dead aileron is not going to pull that plane into the ground .

You may of answered your own question "taking his flying style into account this shouldnt have been the main reason for his crash" . So If he burned his old gear with a short in the system then that means he had NO POWER DISTRIBURION what so ever in his old plane .

His old plane went in because . 1 the system had a short
2 the system didnt have power distribution

He was happy with his old set up so he repeated the whole system AGAIN .
At this point he KNOWS that his old systen DID NOT WORK and still goes ahead.
Your mate puts the plane into the air and It smacks the ground in ten flights ,do we see a pattern yet . These are the things you do know.

Ask him where the 5645 servos came from and if he tells you out of the old shorted out pile of broken fiber glass you found at your local flying club then all you can do is shake your head and walk away .

Accidents no , mistakes yes , and we all make them .

Stu

[reyn3545]

Man... how 'bout a dose of tough love!!

[Tired Old Man]

Can't do tough love when someone wants a manufacturer to replace a plane when the cause appears to be user indiced. Sorry, just can't do that. In the pics I only saw one servo on a wing half. The plane was designed for two so the owner was trying to save effort and money in the set up. I know the manual suggests a ahigher torque, higher quality servo thatn the one that was used so once again the owner was trying to shave finishing costs from the project. Without knowing more about the electricals I won't add anything to that fire.

Flying the Superextra with only a single servo per side will leave the aileron with a little bit of what I'll call "slop" at neutral. Using the second servo eliminates that "slop" How do I know? Because I've flown one both ways and the single servo arrangement is a bad idea. Moving fast enough and that "slop" acts the same as flutter. Using an under rated servo adds insult to injury.

There's nothing at all wrong with the Comp Arf living hinges. The same type of hinge is used on unmanned aircraft costing hundreds of thousands dollars more. You don't think someone would use a bad hinge design on a $200,000.00 plane do you?

I'm afraid this one is on the owner, if for no other reason than for using only a single servo per side. The manufacturer provided the space for the second, and noted a second in the manual.

[Rolling Thunder]

Pat, It uses to 2 servos ganged together on a tray that is bolted into the wing.

[reyn3545]

I agree... I was saying that maybe a hard dose of the facts would put this issue to bed quickly. I installed 5645's on a 74" Yak with a 46cc motor.. they were so sluggish even on that small of a plane that I upgraded all of them to 5985's before the maiden. I could only imagine what the resistance from an aileron that big would do to a single-servo setup using them. Even flying "gentle" circles has got to strain them beyond their capabilities.

[OnTheEdge]

	Quote: Originally Posted by Doc. insane
	The servo’s running the ailerons were HS5645MG’s @ 6V.

Sorry for your friend's plane but don't need to know too many details beyond above.

While the results were not positive for your friend, hopefully others getting into GS will learn from his misfortune.

Hope he gets another plane is the air real soon.

......Mark

[dubd]

I flew a SX with a blade spar for an entire season without any wing issues. I had 2 5955 servos per aileron and I do not know why you would go with anything less in a plane that size. I have had issues with the gears in 5645 servos in the past, so I do not put them in anything over a 50cc plane.

[JVDO]

Hi Doc,

Maybe you can contact M. Feyaerts for more info. He once got 2 new white extra's from Composite -Arf after 1 wing opened up in flight (starting from the leading edge).

[Doc. insane]

Let's get back to the facts shall we
The guy used top of the notch brand new gear, double synth receivers, lipo's, all you want, EXCEPT some heavy duty servo's for the ailerons. So you may blame him for using a bit too sloppy servo's.
Anyway, My friend just got back a very friendly email from Andreas from comp arf. He explained what could have hapened, having watched the pictures and read the facts. He doesn't agree it is a production error, because it only happened on the 10th flight and the planes get a very good inspection before their are shipped. He told us the aileron failure was caused by a short but serious flutter and he adviced us to use at least JR8611's or hitec equivalents. Anyway, they are prepared to make a new superextra with a discount, which is fair enough imo! And this time I'll make sure my friend put's at least 2, maybe 3 if possible, JR8611's or HS5995Tg's in those wings.

Conclusion:
- Always use the heaviest servo's available in giant scale airplanes.
- Comp arf were very helpful!

[statbeast]

It is nice to hear that they were helpful and that your friend will get one back in the air soon. I do agree with the others that 5645s are too weak here and 5955s should be used, even in planes much smaller than this. The price differential is not worth the reduction in servo quality.

[JohnVH]

I use JR8611's in my 3.3m Yak.

[jonkoppisch]

What was everyone using before the 5955? The 5945's?