700N Down

[SRH990]

Enjoying flying the 700 today, despite the cold and damp. Second flight out I was inverted about 50ft up pirouetting, let the rudder stick go back to centre - piouette doesn't stop If I'd have been right way up I might of stood a chance but it all got very hairy, very quickly so I hit throttle hold and waited for the hit. When we got there the boom was hanging at a jaunty angle, one side of the skids was snapped off, Funoso canopy mutch the worst for wear plus the obligatory flybar & blades. The tail blades were also hanging off and looking closer the turned down end of the tail shaft had sheared off, looks like this was the cause of the loss of tail as the heli hit on the other side, nose down plus the tail was completely clear of mud.

The good side is I'd already had a new Funoso canopy delivered at the new low price from Blink and the total cost of spares, excluding blades, is under £50 and I'll have a spare mainshaft & flybar when its sorted.

My mate was a little less lucky, stuffed his Logo 500 in at a fair speed, wrote off both sideframes, canopy, mainshaft, boom etc. which will probably make it cheaper to buy a new kit

[Smoothound]

So it's not just Align screws that are made of cheese then


I feel your loss though

Lucky it was not an expensive crash, unlike the L$g$

[BobJ]

Hi Steve

Sorry to hear about that but I suspect it wasn't the tail shaft failing because if it had then almost certainly it would have f#?cked off a long way with all the energy a spinning tail rotor has in it.
Once the shaft has snapped there is nothing holding it on to the model as the slider would just drop off the end of the shaft.
of course this means you have to stress about what else caused the pirrotte to contiue now:-)

Cheers
Bob J

[trebor27]

That's bad news mate! Sorry to hear it!

Rob

[moonmanflyer]

Sorry to hear about the ding, could of been alot worst.

[StuSmith]

Gyro didn,t fall off did it? That's wat happened to me once.

[3dx]

So sorry this happened mate- like you I had virtually the same type of crash-was upright though- on my 600E,, crash turned out to be 601 sensor coming adrift from sticky pad/metal/pad base,,,, now velcro'd down as well as new pad,, You'll soon have her back in the air buddy!

[David Drew]

Tough one Steve.

Catch you soon

David

[SRH990]

Hi Steve

Sorry to hear about that but I suspect it wasn't the tail shaft failing because if it had then almost certainly it would have f#?cked off a long way with all the energy a spinning tail rotor has in it.
Once the shaft has snapped there is nothing holding it on to the model as the slider would just drop off the end of the shaft.
of course this means you have to stress about what else caused the pirrotte to contiue now:-)

Cheers
Bob J

In that case I'm still at a loss to explain how the end of the shaft was sheared off in the actual crash, there wasn't any mud on the tail end at all, unlike the front! The slider was still retained on the shaft by the lever arm and as I was pirouetting with torque there was actually little strain on the tail blade & hub assembly, I'm guessing the gyro would actually been pulling the slider farther in to the shaft towards the gearbox, keeping it from flying off. At a guess the tail blades would go to zero pitch and stop spinning pretty quickly. The remains of the tailshaft are dead straight and there are no signs of impact damage to any part of the tail.

It's still early days to sort it out but the Spartan gyro and BLS251 tail servo are still working perfectly. Although bent, both ends of the torque tube are still intact with the pins & retainers in place and the bevel gears are perfect each end of the boom

I have got a Quick UK tail assembly fitted and have noticed recently that although the grub screws are tight there is some teetering play between the tail hub and shaft. I've got about 5 gallons through the 700 since it was built and the Quick UK tail has been fitted for most of that time. When the new tailshaft arrives I'll see if there is any play at this point with both the stock tail and the Quick UK version. I've seen it noted on other forums that the Kasama tail, intended for the 600, has the same teetering problem which gets worse with wear.

I'm not out to bash Align, if you fly helis something will fail at sometime and I'm much happier with the repair costs of the 700N compared to the Fury Extreme it replaced, without the blades the parts costs are lower than the comparable items for a Raptor 50

[BobJ]

Hi Steve

Did the blades whack the boom in the crash as this could put enough shock loading on the output shaft to shear it off.
Not sure how hard the tail output shafts are as haven't tried bending one yet but I suspect it's fairly hard so a sudden shock might well break it.

I would have to have a close look at my 700 tomorrow to work out if the tail rotor it going to want to thrust away from the tail box if it can or get pushed towards it.
Too busy on duty looking after baby son at the moment to check into it further right now.

Cheers
Bob

[ChrisB]

What firmware verison are you running on the Spartan,there was an issue with the older firmware i have heard of at our field and witnessed a heli start piroing uncontrollably and then crash where the gyro just powers down.When the power is cycled it works normally.

If you do a search i am sure you will find more info on this.

[Tim Procter]

Bad news on the 700 going in Steve. Feel kinda gutted for you as I treat mine with kid gloves and would hate this to happen although we all know its not "if but when"..

Like you say its a mystery why the tail shaft broke and seems bizarre to me too but will watch this thread with interest.

[SRH990]

The Spartan gyro is on v1.8 firmware, the latest, and has performed faultlessly since I bought it at 3DM, it did have very slight drift in the warmer weather but seems rock solid since things cooled down.

I'm actually not gutted at crashing the 700, I've felt very comfortable with it since I first flew it and I'd much rather have a crash I think I can explain than a total mystery plus the repair costs are pretty minimal compared to every other 90 on the market.

[Lad]

“I'd much rather have a crash I think I can explain than a total mystery”


Steve,

Having witnessed the crash and taking part in the post-mortem, I am absolutely convinced the problem was the tail shaft shearing in-flight rather than anything else.

As you describe in your earlier posts the model went in on the left front-hand side (opposite the tail rotor) and clearly the entire tail assembly (including tail blades) was completely damage free, bar a few splats of mud..!. If the tail shaft had sheared as a result of the crash, I would at the very least have expected the tail shaft to be bent.

Having thought about this now for a couple of days, the bit that concerns me is fit of the Quick UK tail assembly on the tail shaft. I remember discussing a couple of weeks ago just how poor the fit was ~ the hole in the Quick UK tail hub was too large resulting in the entire hub teetering on the tail shaft (pivoting on the grub screws).

I wonder if you encountered some form of ‘fatigue’ in the tail shaft caused by a resonance / vibration due to this teetering action…?

I’d be concerned if you still have the play in the tail rotor / shaft when you reassemble…!

Lee.

Ps. I assume you managed to find a replacement tail shaft rather than buying a complete tail box?

[robgt]

If the piro speed continued at the same pace as you were instructing just before you tried to stop, that would point to the tail shaft not having sheared at that point.

If the shaft had sheared at that point, the piro speed would quickly pick up pace as there is no longer anything stopping the heli from pirouetting at the speed of the main rotor blades.

It also sounds like it didn't happen on impact - if the tail was pretty much clean on inspecting the crash damage, which makes for one hell of a puzzle!

Cheers,
Rob