Air One F3F goes in with no control - just figuring out reasons...

[ChrisInTheVale]

Hi All,

 

(Warning - another Chris essay)

 

Had a glitch on the air one - 20 meters out today - one second of no response and then back again.

Investigation showed JR connector on battery powering the receiver was very intermittent.

So a few actions were taken -:

• Replaced 5 cell pack with new 4 cell Intellect - slope side
• 4 cell battery topped up with field charger and registering 5.9-6.0V
• solid connections to receiver - no drop-outs at all (lots of wire tugging etc)
• Range check great (50m on reduced power)
• tiny weight added to compensate for 5 cell drop-down to 4 cell

Then threw off top of Hiwaun Common

• All controls ceased to respond 30 meters out -
• Glider flew down and out - fairly straight around 900 meters (mapping flight of death on Google earth this evening proved therapeutic)
• Air One Actually circled back about 200 meters and landed within the bounds of the open cast mining site
• Very long walk - very nice mining bloke assisted (Coal board health and safety insisted) - plane was retrieved - nosed into wet bog - fus snapped nose and tail - smell of burnt servo etc.
•  Nice Mining Fella drove me back up the mountain

Post mortem tonight

• Receiver works fine
• Battery works fine
• All servos operational except the smelly one (one of the v-tails). I am far from electrically bent - but faffing with the multi-meter  (I think set to measure resistance - lowest value - 200 ohms) - all servos indicated a "1" except the non operational servo which registers 48.0. No idea what this means except to say this servo is different electrically to the other five - so I assume a burnt out component.

 

Ponderings

• Given the aluminium v-tail rods buckled (one actually snapped) on impact - it could be the servo burnt out after impact under extreme load
• I guess I am wondering if the servo burnt out mid flight and could that have caused unrecoverable receiver failure.
• The plane was uncontrolled and airborne for about 45 seconds to a minute (excruciatingly long time) - yet receiver at no point sprang back to life.

What next

• Receiver (dried out on radiator) seems fine but is now consigned to the "light use in foamy only if anything pile"
• Battery dumped
• Air One set aside for a rebuild and refit or new Fus whenever I have the heart to address it. (Double carbon wings saved by the wing joiner snapping)

 

Couple of questions

 

- could flying the servos on 5 cells for 2 years and then flying for the first time with 4 cells (but good voltage) encourage any servo to fail? I don't believe this is a low voltage issue - recovered battery constant at 5.7v even now.

 

- Given other glitches recently (other thread on M-Link Glitch) - giving serious thought to replacing the transmitter as at this moment in time a like for like replacement of the Cockpit SX 2.4 at 160 quid almost seems a reasonable price for peace of mind.

 

I also have re-emerging thoughts about fail safe settings and am thinking of 6 ubec's for the Ascot Short (been reading Mikes recent comments about using LIFE and servo Ubecs)

 

If anyone actually managed to get to the bottom of this post - I apologise for the length - documenting the event seemed to have  cheered me up after a frankly rather rubbish day.

(At least my Galaxy phone did congratulate me on managing to walk more than the recommended 10,000 steps today.)

 

Any thoughts, musings welcome...

 

Chris

[satinet]

A faulty servo could cause a large draw on the battery. But it should take long enough for you to notice something wrong. Say a 2amp draw would still take a few minutes to drain the battery.

It seems more likely the burn out was caused by the crash to my mind.

[isoaritfirst]

Just because I know of two recent occurences..

you werent in reduced range/binding  transmitter setting were you..   of course not.. 

 

I did lose a model many years ago that reacted just like you described, my conclusion then was to two failed servos. I had a bad batch of VolZ usually only one would go at a time and the model would carry on without it, but on this occasion all signal was lost to a battery sucked dry.

[satinet]

I wouldn't use a servo connector as a power switch if that is what you did.

[oipigface]

Did you switch the transmitter out of range-check mode? You don't mention any checks you may have carried out on the transmitter after the crash. It appears that it was working (at least in range-check mode) before your unfortunate occurrence, but have you checked it after? Don't ask me how one would do this oneself. If I wanted to do it, I would send it off to whoever services them.

Which is Hirwaun mountain, and where is the access?

[andyharrold]

 check the switch.

i had an old model that would drain a battery in no time due to a faulty switch.

also check all of the connections between battery and rx.

( i had a pattern ship do 12 outside loops at 3/4 throttle on a trimming flight. not much trimming requied after gravity won the battle!

that was a loose battery connection.

[isoaritfirst]

Also try checking each cell of the battery, if you can attach a few probes to a meter and jab them onto the cells.

 

Make sure pack is balanced.

 

Unbalanced packs will show full voltage off the charger and when under no load, but fail very quickly under load.

[Phil.Taylor]

2x glitch/lockouts on 2x flights...

 

first one might not have been the Rx battery, even with dodgy wiring/connector - poor Tx signal?

 

second one - still in range check mode? - poor Tx signal?

 

 ->  check the Tx aerial & all connections to it?

 

Phil.

[isoaritfirst]

Dodgy wiring / short somewhere in the model.

 

I lost my ProdiJ HM a few times to complete reception loss, fortunately after a little spade -  work it was fine. 

 

Always difficult after a crash and torn wires etc but eventually put it down to the flap servo slowly cutting through the wires to the wing servos. 

The install was a bit tight and I didnt make the wing plug on initially, been fine since plugs and wiring all tidied up.

[Bear]

Had an issue with my Evo just before the trip to Ireland, on advice from T9 I replaced the TX aerial. No further issues during a lot of flying. With the old aerial I did once reproduce the problem.

I always set fail safe with crow brakes down so signal loss is evident.

 

 

Roger

[ChrisInTheVale]

Many thanks for the replies!

 

I can confirm the cockpit sx was in full power mode - the thing plays an annoying (but useful) tune at you in low power mode.

I generally don't use the connector as a switch - but do unplug the power switch completely from the battery in-between weekends.
I will be mindful now to check the wiring on these doesn't get loose over time.

Transmitter does seem ok (though I have lost confidence in it). several years use and more than  a few occasion's used when drizzle should have made me put it away.
All seems well with the aerial (has issues before with these) - but this was a newish one.
Inside wiring - especially around antenna all seems connected ok.

I will still investigate further including other wiring.

Paranoia did result a new cockpit sx 2.4 to replace the old one (rather odd carbon red and black version as it happens)
Also awaiting a LIFE to accompany the servo sbecs obtained from Rich.

 

I was even investigating backup possibilities - a few UPS things out there for emergency battery falure
but perhaps none really lending themselves to a skinny F3F type of layout.
It does suprise me that with the super little SmartLipo self regulated batteries out there (like I use on my DLGs) - companies are not
going the extra step to add a diode and lost model style alarm providing a 20gram opportunity to protect a model against battery failure at least. (simpler to say it than build it perhaps )

 

 

John - fyi - Some info on Hirwaun Common (if you don't mind a bit of a walk from the car) 

 

A fabulous flying space in a NW, N or NE with easy landing. Also a huge bowl for when its easterly (further walk around again). Short branch off the heads of the valleys road A4061 Rhigos Road (20 minutes from Bwlch).

Park either by food caravan or a bit closer in an off the road cul-de-sac. stroll along the road - up the hill  and find a concrete post facing N which marks the spot. A worn track makes walking not too uncomfortable along the 600-800 meter stretch.

 

The Area

 

The Walk

 

The Easterly Bowl (inside a low sheep fenced area)

 

Thanks again all for your input.