Receiver Battery Failsafe

[Granpappy]

I know that it is a legal requirement to set Failsafe for signal loss. I've set mine to throttle cut and cyclic, collective and rudder centred. However if your system has low receiver battery failsafe, are you legally required to set this as well?

My concern would be high power demands momentarily dropping the receiver voltage below the threshold and initialising low battery failsafe which then has to be re set by whatever switch or stick position you program. Typically moving throttle to zero and back up again.


Just wondered whether it was a legal requirement for insurance claims.

[GIXERMAN]

isn't this why we have optiguards as a backup!

[trillian]

I've never heard of an RX battery failsafe, so to answer about the BMFA, they only talk about the failsafe settings in the RX or FBL unit that kick in if it loses signal.

Regarding a momentary low battery / RX power situation, I don't want my RX to do any kind of failsafe I want it to continue to respond if possible and wait for the power to recover and return to full operation as quickly as possible. Ideally you want an RX power supply capable of handling everything that is thrown at it so that the voltage never dips far enough to brown out the RX.

[coolice]

Hey all.

Personally I think the best advice is to make sure your power system is up to the task of power your model, if it's on the limit and you're relying on additional items to keep it out of trouble then somethings wrong.
An OptiGuard is there in case of a complete failure in the flight gears power supply, it should not be fitted to act as a buffer.

With failsafe I advocate all controls to neutral, collective pitch to zero and throttle to idle (IC) or off (electric).
There can be for and against arguments as to what is best, but a floaty model on its way down is easier to keep an eye on than one suddenly changing attitude due to a sudden change in collective pitch. I've seen models suddenly slam themselves into the ground a few metres away under a failsafe situation, they're not nice to be around.

Usually a sudden drop in power and subsequent drop in vibration sometimes brings control back if there is a failure. A quick landing then ensues, ive done this myself many years ago tracing an old 35mhz glitch/lockout problem, turned out to be a knackered mainshaft bearing.
Any brownouts will likely also effect the servos ability to reach their failsafe positions anyway due to the lack of volts, hence the ESC manufacturers killing any motor power on signal failure to the ESC.

Ian

[hedge]

If you think it though, with the loss of signal failsafe set you are also protected for the RX low voltage - effectively loss of signal - as well. So your covered. Great that you have set it as it is often overlooked.

[Grumpy]

Other than cutting power (which I assume all agree with) then on a heli it really doesn't make much difference what you do with the remaining controls. The heli is coming down and where it comes down and how it hits is entirely in the lap of the gods at that point. As you never know what position the heli will be in when it fails and what stick input (if any) you have at the time then it's impossible to say for sure if 'fail in position' or 'reverting to a pre determined failsafe position' would be safest.

On the other hand.. By dictionary definition a 'fail-safe' is a system that:

causing a piece of machinery to revert to a safe condition in the event of a breakdown or malfunction.

So in a court of law (if it came to that) having servos simply stay in last commended position on radio link failure might not be seen as a 'fail-safe'.. because there is no 'reverting' to any pre determined 'safe condition'. I guess you could probably argue that cutting power alone was all the fail-safe that could reasonably be achieved on a heli.

A battery back-up is entirely different to a failsafe. A backup system is designed to prevent overall system failure.

[Granpappy]

To summarise. My transmitter has the above as a safety feature. Am I legally required to enable it for insurance purposes.

[paul 5ive-t]

while we are on the subject I use a futaba 14sg on a trex 450L dom with GPRO and a 6303sb receiver using sbus, I have set failsafe all at zero and when I switch off tx it all works perfect and return to neutral yet on my goblin 700 comp using all same as 450 apart from I am using msh brain when tx is switched off all servos stay in last position but tx is set to f/s not hold?

[trillian]

To summarise. My transmitter has the above as a safety feature. Am I legally required to enable it for insurance purposes.

No, there is no requirement that pertains to such a feature. The failsafe is only pertaining to a 'loss of controlling signal'

The latest guidelines are:

Level 1

Rotorcraft with no electronic stability or programmable flight control capability.

Failsafe to be programmed to move throttle to idle or closed position on loss or corruption of the controlling signal, as per current requirements set out in CAP658.

Level 2

Rotorcraft with electronic stability capability but no programmable flight control capability.

Failsafe to be programmed to initiate an immediate hover followed by a controlled descent on loss or corruption of the controlling signal.

Level 3

Rotorcraft with electronic stability and programmable flight control capability.

Failsafe to be programmed to initiate a “loiter” at the point of signal loss or corruption, followed by a return to launch position on continued loss or corruption of the controlling signal after a predetermined time period, at a set altitude above launch position, followed by a controlled descent.

This level requires careful consideration and robust practices to ensure a lawful and safe return to the launch position on the triggering of the failsafe function.
Level 3 rotorcraft must only be made “live” once out on the flight line and this location must be confirmed as the RTH point prior to the commencement of any flight.

[Granpappy]

Thanks Sheryl. Is this from CAP658 or BMFA?

[Grumpy]

Great info Sheryl !.. that makes it crystal clear.

I guess the remaining question (as there is no legal requirement) would be if you wanted to enable such a feature anyway?.. Personally it seems like a bad idea to me. I'd rather just have an alarm on low Rx battery voltage rather than everything going un-commanded to fail safe with no warning.

[Granpappy]

Great info Sheryl !.. that makes it crystal clear.

I guess the remaining question (as there is no legal requirement) would be if you wanted to enable such a feature anyway?.. Personally it seems like a bad idea to me. I'd rather just have an alarm on low Rx battery voltage rather than everything going un-commanded to fail safe with no warning.

I wouldn't for the reasons stated in my first post.

[coolice]

If the servos hold, there is no sudden change in collective or anything. The problem going to zero degrees collective, is you retain HS and cause more damage when the heli hits ground. It will only slam into the ground if you have a fixed position set on the servos, not hold.
As you say though, arguments for and against.

Hey Buddy.

Sort of, the problem comes if the hold happens when mid-way through a tic-toc perhaps when using full positive/negative for the Toc. Or any sudden control input, which let's face is the most likely cause for a receiver brownout as all servos are commanded to move in unison and pulling to many amps from the setup.

A few post downs nails any failsafe, brownout, lockout on the head and that is that the model is likely coming down and where no one really knows.

while we are on the subject I use a futaba 14sg on a trex 450L dom with GPRO and a 6303sb receiver using sbus, I have set failsafe all at zero and when I switch off tx it all works perfect and return to neutral yet on my goblin 700 comp using all same as 450 apart from I am using msh brain when tx is switched off all servos stay in last position but tx is set to f/s not hold?

Hey Buddy.

This is interesting, as you're using a normal SBus receiver I am guessing it should still output the failsafe commands to the FBL controller once it looses signal. Guessing you've tried resetting the failsafe just in case?

Great info Sheryl !.. that makes it crystal clear.

I guess the remaining question (as there is no legal requirement) would be if you wanted to enable such a feature anyway?.. Personally it seems like a bad idea to me. I'd rather just have an alarm on low Rx battery voltage rather than everything going un-commanded to fail safe with no warning.

Hey Buddy.

Sadly I think by the time the alarm sounds it will be too late and the receiver will then shortly go into failsafe following a drop in Rx voltage and then recover accordingly.
A low Rx battery alarm is great when using a normal Lipo perhaps, but not so good for a BEC supply.

It's a very sinking feeling when your model sudden locks-out on you leaving no control, having gone through it a few times on the old 35mhz gear and once with 2.4ghz when my old DSX12 Rf module went low RF with the model no more than 4 metres in front of me, it's scary.

Ian

[waveydavey]

It may have been posted above but if a low voltage failsafe occurs would there be enough in the pack etc to move the servos in the first place. A loss of signal is different, interesting thread

[coolice]

It may have been posted above but if a low voltage failsafe occurs would there be enough in the pack etc to move the servos in the first place. A loss of signal is different, interesting thread

Evening Mate.

Very valid point and most likely no, as the receiver will be rebooting, it will certainly not be thinking about moving the servos to any failsafe positions. Also once it was back up & running, it would then have to relay these commands to the FBL unit. We're only talking miliseconds, but in reality that ground is fast approaching

Ian