Buffalo FX-79 Build - maiden/re-maiden crash, 3rd time lucky

[bignose13]

Control surfaces on the elevator reversed, you went to pull up when in fact you pug the wing in a dive

[FPVSteve]

See, I'm assuming that the control surfaces were all working properly ........ Wayne? :D

[mark1975]

looks like reversed servo to me its to co- ordinated not to be ???

[Jake Bullit]

CoG to far forward? Not enough throttle? To heavy for power unit?
Elevon throw reversed?
Motor reversed?
Prop on backwards?
That throw was to steep.
Should have walked up that hill, or used a bungee.
Did you have any wind in the nose, that would have helped to.
Might have been better to try it line of sight with just the battery ,motor and esc before weighing it down with FPV gear.
Could have been any of the above really, at least it's fixable.
Just my thoughts.

[sykick]

It does not look like a stall to me, to controlled. The FX79 also has a huge wing area and can fly very slowly, my FX61 still surprises me by how slow it can go. My vote is for some sort of control surface input, intentional or otherwise.

Sorry for your crash, its real setback when this sort of thing happens.....

rgds,
Marcus

[CurryKitten]

I am guilty of having reversed my ailerons twice before, so I checked them on this one, and then got Neil to check them again for me... twice.  Then we checked that stabalise would also react in the right way - it did, although it wasn't engaged during the short flight.  In terms of my inputs, I hadn't pulled up, I'd just given a little bit of right (iirc) input to straighten out before it plunged downwards.

Wing area is very large, and was only taking a single 5000 3s, so I thought it would have a pretty good glide on it.

Prop was on correct way and motor was spinning correct way.  Neil did note that it didn't seem to push against him that strongly when I put the throttle on.  Unfamiliar with how this should feel with motor/prop combo.  It's a 900kv on 3s running a 12x3.8 prop.  Obviously we're not expecting it to fly out of the hand - how strong should it feel ?

When I get a chance I'll check the amp draw on the motor to see if I can figure it it's operating at it's full potential (yes I did calibrate the ESC)

[Dizzy]

CurryKitten are you sure you where in manual and it was not a AP input but to much that caused a stall :+

Very sorry to see this happen I had a similar thing happen with my Scout bee on her first throw but that turned out to be interference from my ESC.

I hope she can be repaired ok

dizzy

[Billy_boy_2010]

Oh no. I really enjoyed watching this build :(

i have never witnessed a proper wing stall before- but IMO it's too extreme to be a simple stall.

The motor doesn't sound very fast to me. I don't know the details of the motor- but that prop size isn't huge either for 900kv. could it be people normally run it on 4s at that kind of prop size?

Even if it's not generating enough thrust that was still a real nose dive. If you only set the c of g a little nose heavy it looks pretty extreme to me?

Pity we can't see the amp draw on take off on the mfd. My first thought was the plane was only drawing 15A by the sounds of it.

If the video was fuzzy there's no chance the MFD was playing up and inverted elevon control was there and slipped itself into stable mode?! It just looks too positive nose dive to be anything other than elevon induced.

As I said earlier I always maiden with full throw on servos but I have 50% option for dual rates if it's too twitchy. But that wouldn't have saved you anyway.

Having said all that it's very repairable and you will probably fly it more and enjoy it more now it's less pretty :)

[FPVSteve]

Could it be the motor thrust angle?

[Coyote]

To me that never levelled, it was in an arc the entire time only when Krikey initially threw it did it overcome the arc. That would suggest to me thrust angle and elevator set too low. Lack or airspeed over elevons and the motor thrust angle made it impossible to recover from.

[Jake Bullit]

Did you calibrate the esc throttle end points?

[CurryKitten]

Thrust angle -



Documentation for Thrust angle



Does that look about right.  Angle would appear to thrust upwards ?  As mentioned it didn't seem to have much push, did it perhaps so little effect, that Neils throw just continued in a parabolic curve ?

Did you calibrate the esc throttle end points?

Yes

The motor doesn't sound very fast to me. I don't know the details of the motor- but that prop size isn't huge either for 900kv. could it be people normally run it on 4s at that kind of prop size?

It looks quite beefy, but is only rated for a 3s

Pity we can't see the amp draw on take off on the mfd. My first thought was the plane was only drawing 15A by the sounds of it.

I'll measure this on a seperate amp meter

If the video was fuzzy there's no chance the MFD was playing up and inverted elevon control was there and slipped itself into stable mode?! It just looks too positive nose dive to be anything other than elevon induced.

The DVR shows that the MFD stayed in MAN mode (top left), so doesn't seem to be that.  In this mode it shouldn't do anything at all

It's kind of back together now, the nose looks very ugly now though, need to fill in all those gaps

[FPVSteve]

Maybe give it a little up-trim before launching this time, see if it helps? And buy krikey some spinach - I really can't think what else it could have been other than a stall.

[Jake Bullit]

Thinking ahead to your rebuild here`s a useful video to help with spar removal.

Zeta Science FX-79 Buffalo - Wing Spar Replacement

[Brucey]

Ah mate, gutted for you. It doesn't look like a stall to me, if you hadn't of already said you'd checked and double checked the direction of your servos I would of said it was reversed.

How much does it weight? Its got so much wing area it must just float.
Worth trying a test glide before another full power launch?

At least its not a write off.