Wednesday, 15 April 2015

Maiden and Death of a Classic Aerobatic Airframe

Clive Weller's Concept

Designed in 1984 in anticipation of the new Turn-Around Schedules, Clive produced this new design which was very different than the current models in vogue at the time.

Built from plans - started in September 2014 this was my winter project. The model was completed just before Easter 2015 and was waiting for its maiden flight. Powered by an OS61VR with tuned pipe with FrSky Taranis providing control

Engine Placement

Completed Airframe

Ready for a Maiden

Got the maiden in last night. Eventually managed to get the engine to run OK, 2 tanks of fuel and reasonable pick up and idle so just before sunset I placed the model on the strip, taxied to the end, lined it up and wound open the throttle.

First impressions was that it is very hairy on the ground, that rudder is huge and it was difficult to track straight. However, got it off the ground more or less in the direction I wanted and noted that the model was distinctly under-elevated. Needed full up trim and holding a little up to keep it level. Elevator was very sensitive so dropped it from medium to low expo/end point and that tamed it nicely. Aileron control was very smooth but the rudder was still very over sensitive.

So Flying around for about 6 minutes just getting the feel for it, decided to land it as light was fading and on the downwind stretch the telemetry kindly gave me a warning letting me know the receiver battery was dying - 2 seconds later no control at all, 2 seconds later - this.

The model went in vertically from about 250 feet....

Not much usable airframe left..


So what happened?

The battery was charged just before I went on holiday- about 2 weeks ago. I don't have the luxury of planning my flying, I just have to seize the moment so I tend to keep all models fully charged up.
The battery in the other model that I had taken had died (left the receiver turned on - probably inadvertently knocked the power switch.

So I borrowed the battery from the Concept and had a couple of flights - about 20-30 minutes switched on time.

Then put the battery back in the Concept and turned it all on, ran a tank of fuel through the engine (still running it in), allowed it cool then decided to go for that fatal flight. - Say another 10 minutes..

But, while we were prepping the Telemetry informed me that the battery was low, I realised I hadn't calibrated the battery level. Measure the voltage on my battery checker - 5.5V (NiMh), set the telemetry up correctly - set the alarm to 4.7V - this cleared the warning, we started and went off.

What I had forgotten - probably with nerves as all this was happening and the imminent Maiden, that I was using a 5 cell (6V) battery and it really was very low. No-one to blame but myself..

SO 6 months building, 6 minutes flying, not the best ratio in the world...

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