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Servo Torque guide - Sport Flying (electric)

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Bob Cotsford29/07/2019 13:25:07
8591 forum posts
483 photos

In fairness - there were odd reports of individual examples of the kit built AW being a bit prone to tip stalling. Mine was always a complete pussy cat but others claims have to be accepted.

However, we are now talking about a different beast just having a similar outline. The ARTF is much more lightly built with a built up wing and from what I remember of the early reviews it could come out quite badly tail heavy. The ones I've seen balanced fine with 46 two strokes up front so there seems some variation. All examples whether kit or ARTF have been fine on 'standard' eg ~3kg servos.

What does come to mind is my experience with a Joker and a King Altair when flown with a slightly too rearward C of G. Most of the time they flew beautifully, flicks and spins were always controllable until the one occasion they weren't. Both went into terminal spins continuing multiple turns after all corrective actions were tried. The Joker was terminal, the KA survived to fly many other days with no more terminal spins. I still don't know just what caused these but I suspect disorientation on the part of the pilot and a failure to recognise when recovery actions actually reversed the spins instead of stopping them.

Nowadays I'd simply review the telemetry logs to see whether I'd lost signal or not, and I always set failsafe to low throttle and neutral on all channels. Position hold could be a model killer!

Martin Harris29/07/2019 14:04:44
9343 forum posts
252 photos

Like Don, I'm a bit worried about the spiral dive aspect. If it was really a spiral dive with power on then you should consider the airframe twisting effects leading to "aileron reversal" I mentioned earlier.

I think you have inferred that he was attempting to recover from the spin by applying some continuous power which doesn't really equate with a spin recovery taught by an experienced instructor. Was he teaching aerobatics or just the standard syllabus though? For many years it's concentrated on the incipient spin recovery after a number of accidents during spin training and student pilots don't experience full spins so experienced aviator he undoubtedly is, perhaps the application of power and failure to recognise a spiral dive developing out of a spin (something emphasised during my time as a gliding instructor) may have been the cause?

Edited By Martin Harris on 29/07/2019 14:06:56

Richard Ashworth29/07/2019 17:42:09
104 forum posts
70 photos

Hi again

Power on was I understand a last resort. I only saw the last 75ft of the 200ft descent so I don’t know about the previous 125ft.

The electric setup was Quantum 55 motor, 12x8 electric prop, 5S 4000 battery, Overlander 80amp SBEC ESC, 4x Hitec HS322 servos.

The fateful flight was brisk, loops, rolls, inverted and about 4 minutes in duration when the event occurred.

For the last 3-4 months 3 turn spins have been a fairly regular practice feature of his flights on a number of models including at least two on the Acrowot two days earlier so it ‘should’ have been business as usual. It was a bit breezy so the Acrowot which is possibly his biggest model and looked totally stable during the rest of the flight was flown.

Piers Bowlan29/07/2019 19:45:59
2150 forum posts
53 photos

I have only had one model truly spin in and that was when the signal wire of the rudder servo failed, causing full left rudder to be commanded. (it was a rudder/elevator model). The model span pretty flat and up elevator movement just made it spin flatter and faster with a slower rate of decent (as you would expect). The opposite was also true but either way recovery wasn't going to happen without being able to either centre, or apply opposite rudder, to stop the rotation. In the end the model hit the deck in a 45 degree nose down attitude causing extensive damage to the lightweight fuselage. I had it repaired and flying again the following week!

In years past I have entered one or two terminal spiral dives with the model simply burying its nose deep in the ground. RIP!

If you had to dig your Acrowot motor out of the ground I humbly suggest it was in a spiral dive, even if the entry manoeuvre was a spin.

my 2p worth!

PS; I concur - I don't think the choice of servos was the issue.

Edited By Piers Bowlan on 29/07/2019 19:55:23

Bruce Collinson29/07/2019 20:12:44
537 forum posts


Was Steve D there for the post- mortem? He has a knack, often helpful, sometimes demoralising when he proves pilot error, of isolating the defective component, assuming there was one. I assume it was Dave B’s?


Martin Harris29/07/2019 20:27:18
9343 forum posts
252 photos

Sounds about right Piers - my flat spin experience ended with undamaged wings and a "sprung" fuselage that simply needed re-gluing. Even the propeller was undamaged thanks to my rather lucky "choice" of arriving in a thick cover crop of sweetcorn.

Bob Cotsford29/07/2019 23:44:23
8591 forum posts
483 photos

The KA went into a ploughed field as a result of a far from flat spin, the fuselage was left stuck in the ground looking like a misplaced signpost


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