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Aerial orientation & failsafes


dave windymiller
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Whilst flying my funfighter FW190 a reasonable distance away (approx 150-200m and quite low at some 15m high),  the engine appeared to stop so I tried to bank for a deadstick landing.  It then became clear that the plane wasn’t responding as I pushed the sticks further over.  Just as I realised this, the engine sprang back to life and the model did a sudden flip and hit the deck at full power (luckily very little damage!).

 

What had happened was the plane had gone into failsafe with the engine going to idle but it did it so quietly I thought it had stopped.  It then came out of failsafe and with the sticks being lent on, the control surfaces suddenly moved and combined with sudden and unexpected full power, brought down the plane.

 

As I looked at the transmitter for some reason for what had just happened I noticed my transmitter aerial was not how I normally orientate it but pointing towards the model.   We did some ground range checks and found the orientation of the aerial did cause failsafe to cut in at a similar distance!  The radios instructions make it clear that the aerial should not point towards the model as this is the weakest transmission direction.  Whether I knocked the aerial or forgot to orientate it I don’t know but a simple error brought the model down!

 

I was using the Futaba SG14 FASST transmitter and Futaba receiver.

 

This worried me as this could have been my jet losing control, all for an aerial pointing in the wrong direction!

 

I have now glued one of the joints in my aerial so it can now only rotate 90 degrees and never point straight forward (towards the model) whilst holding the transmitter.   This will ensure I cannot accidentally have the aerial in the worst direction for range.

 

I will also seriously consider having a failsafe set to kill an IC engine rather than idle – The engine suddenly coming back to life was why I lost control.  A dead engine wouldn’t have been so much of a problem!

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Hi Dave,

 

That’s certainly something to give you cause for concern, particularly as you were able to replicate the failsafe operating with a range check but it does make me wonder what exactly is going on there. I’m sure there is absolutely no doubt it’s aerial orientation but could it in fact be an indicator of an overall feeble signal strength as well?

 

I say this because over the years I’ve spent quite a bit of time experimenting with model kit actually trying to make it not work correctly and very much in the main I’ve completely failed. It started back in days of 27MHz and AM CB radio and went on from there. I’ve often tried to get a result with the aerial direction situation but I’ve not succeeded yet; and I’m talking a full length ground range checks, a measured 700 metres. But still LoS of course. Much more than that and I’d definitely fail the eyeball test first so at that point the signal strength wouldn’t matter that much anyway.

 

So what I’m saying here is that I’ve never met a tx - rx combo that didn’t have a 100% hard link together irrespective of wherever their aerials were pointing even at this sort of distance; which is why I’m thinking a 200 yard limit may be a bit suspicious. Maybe worth a little coat of looking at perhaps……

 

And as an aside, I’ve often seemed to have found that many things aeromodelling on test don’t always behave like convention says they should be behaving…. I even found this happening with the CB radio thingy right back at the start……

 

Good luck.

 

PB

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Dave,

 

This is interesting. One of our club members had a similar occurrence with a recent Futaba TX (I believe it was the 14 channel but not certain). His model that day was luckily a Junior 60, it went into failsafe well within visual sight and flew away (probably helped by some thermal activity). Luckily he had his name and phone number on the model, and was called later that same day by someone who had found it a mile or so away, undamaged.

 

On testing it on the ground it was soon apparent that his ground range (in range check mode) was very short, a dozen or so yards at the most. This clearly accounted for the issue. We then retested the range by binding the model to another member's similar TX and that was fine. Going back to the original TX, it was found that tapping the back cover would sometimes produce a much improved range. This suggested that something was loose within the TX.

 

This all happened about a year ago. At that time, the owner contacted Ripmax with a view to having the TX investigated, but was told that, due to covid, the service department wasn't operating and there was no indication when that would change. Lucky for the owner, his son had a 10J TX which he wasn't using and that has been used ever since with no issues. I don't believe he has since contacted Ripmax again to find out if they can now look at the TX.

 

It may be therefore that your TX is suffering from a similar issue. It's certainly worth looking into it further. It's lucky that you have found it with both minimal damage to your model and no injuries to anyone.

 

Brian.

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Funny we have had a few 'lock outs' lately at less than 100 metres, Futaba 8channel ( the new one ) both the rx ariels were touching in a 26cc petrol Chipmunk, it turned around the model field and the lucky beggar got it back and landed it.

 

 Spectrum Dx 6 or 8, electric Bushmaster ( ? ) took off ok landed with the rudder channel reversed,,,( third problem with different spectrum radios all flying electrics )

 

Graupner MX 12 in an electric flying wing  radio lost at 100 metres landed in the grapevines and never found,,at

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Did a bit of experimenting with the funfighter.  Reduced power range check was a good 50 big steps away and was consistent with many tries until the aerial was pointed directly at the plane. It reduced by some 40-50%

 

The 2 aerials in the plane at the orientation when it lost signal was with one aerial pointing back towards me. When the plane was rotated a bit, the range check improved!

 

Had several flights with the plane with the tx aerial "correct" and it was solid all day.

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