Large Model Association Forum

Some of you at the Cosford show may have seen my unfortunate CriCri 'landing'. It may have looked like an accidental crash but it was far from that, in full size flying terms it was a controlled flight into terrain or 'CFIT'. The take off was fine but after a couple of circuits I realised that the engines were not responding as they should and the elivator and aileron control functions were very much reduced. A close flypast at what was supposed to be slow we noticed one engine was at high revs and the other ticking over. I decided to end the flight so on the next approach I operated the 'kill switch' to cut both engines....no result...and the steerable nose leg was at a peculiar angle. This meant that one receiver was not operating, the one with the kill switch and the throttle for the high revving engine and the steering. I couldn't risk trying to land at flying speed because with no steering I had no idea where it would go and if I lifted the front end to try to steer with rudder it was at a speed where it would just take off again....I tried it...twice! We have all had throttles stick open and had to fly around until the fuel ran out but this model has a 2 litre tank which it shares with both engines, with the one engine at about 3/4 throttle this would mean cruising around for about an hour, not at a show I think. The alternative was to bring it down on the grass heavily to bring it to a stop. It worked safely and this is what matters. Not too much damage and on inspection the fault was a battery connection that came adrift, the model dismantles to several parts for transport and these are the parts that came apart. Lessons to learn? yes.. make sure that you can stop both engines whichever receiver fails and that steering is controlled by both receivers.

Bit of a drastic thought here, but...what if you had lined it up on a wide area of the grass, away form the public, gone low and switched off the Tx......The throttle would have cut and with surfaces at neutral a passable landing may have been possible....too radical?

deleted

Hello Bob, would have liked to put it down on the far side of the runway on the long grass but the pyrotechnics set-up with several people walking about were there. Never mind, putting it back together will keep me out of mischief for the next few weeks. Thanks for your 'radical' thoughts though.

There is an arguement for saying that the throttles should be on one Rx and the kill switches or chokes the other. That way, whichever Rx failed for whatever reason, you'd always be able to cut both engines when required. It was sad to see an unusual aeroplane damaged this way.

Ian.

A good point Ian. With a battery problem (or switch, my bugbear) then failsafe will not, of course, happen. Maybe a kill switch should be mandatory on a two rx system?

Good video of what happened on youtube.......CriCri crash. LMA model show Cosford....

CriCri back in one piece, very little major damage. Can now stop both engines from either receiver and nose wheel steering is on both receivers. Lessons learned from something that has never happened to one of my models before.

https://www.youtube.com/watch?v=v71EZTuRDkw

Great to hear Dave. You did a great job getting it down considering the problems you had. Look forward to recording an uneventful flight!