Failsafes, January article

[Ian McDowell]

I read the article in this months mag, with (to me) the new process for adding pre-set failsafes, and decided to check my fleet and have a go at programming something more useful that 'hold last & cut the throttle'.

By that, I reasoned that reverting to a gentle flat turn at least gives those present a chance of predicting the crash site; it should give more time for normal service to resume; it may prevent a flyaway.

I only fly electric, with a DX7s and, discounting the UMX's, a very limited range of installed Rx's.

After a lot of trial and error with each of the installed Rx's, and trying both binding approaches (normal but with sticks held to desired failsafe position; alternatively insert then remove the bind plug approach), progress is zero.

It seems to be impossible to bind a Spektrum Tx/Rx combo without including at least 'Hold Last/Cut Throttle' set as the failsafe. On the Rx that seemed to suggest pre-set failsafe is achievable, it would bind with the levers held but not with any change to the hold/cut logic.

The DX7s manual is clear that 'pre-set' options exist, but are Rx dependent. It gives no clue that you might remove the bind plug before binding though.

It even quotes the AR8000 as being capable of this...although in the earlier thread Horizon chose not to reveal this!

AR400 - manual is pretty clear, Hold last/cut throttle is the only option and practice seems to bear this out

AR635 (in Dallas Doll - without the 'SAFE' implementation of some models) - The manual is wonderfully silent on the topic, but we all know that means nothing with a Spektrum manual. On reflection I may not have given this one a chance. I tried both binding processes with flaps set at half position. It wouldn't bind, but I havn't actually tried it with flaps at zero.

AR6210 - again not previously listed by Horizon, but this time the manual is word for word as per AR8000 wording. No mention in either manual of the insert bind plug/connect power/remove bind plug/bind routine. But that's OK, because neither that nor the standard approach made one jot of difference.

Anyone had any success with 'pre-set' failsafes?

[trebor]

This is one reason I feel like changing over to a Frsky and open tx.

[FlyinBrian]

Pre set FS is available with some rx, insert the bind plug and switch on the rx, the bind light should flash.

Remove the bind plug and if the rx is capable of pre set FS the light will continue to flash. Set the Tx controls where you want them to be if FS is activated then with the TX bind button pressed switch on the Tx. The Rx should then bind as normal. - Check FS operation.

[Denis Watkins]

Yes Ian, Spectrum Failsafe is integral with Throttle, and arguably, is all that you need in those circumstances. Hold is a real decision making dilemma as at would point would a models attitude would be safe to HOLD? At what height? And speed? And wind direction? And the model heading?

It is too much of a gamble, where throttle cut, will at least reduce the speed and height pretty quickly.

[Jonathan M]

I've been busy jumping through these hoops with a variety of my Spektrum receivers, and remain as confused as ever. Both the TX manual (DX7 black) and various TX manuals are confusing in the extreme.

[Ian McDowell]

Wow, great response and it 's clearly not just me who's puzzled.

I can well understand jumping ship especially to Frsky. But I don't really want to get sucked in to the joys of unrestricted programming. Feels like I have spent half my life designing/resolving databases and programming neat little fixes. Flying is a release for me. And once committed to one system changing is a big deal.

FlyinBrian - useful extra info about the continued flash. It could have saved me a lot of bother. I could only easily see one Rx in situ, the 6210. It did continue to flash after the bind plug was removed and I had 3 or 4 goes at binding with a slow flat turn on the sticks. All it ever did was bind with Hold & Cut stored.

There must be something more to this? How long must the sticks be held? Must they be absolutely steady?

I would happily go for Cut and revert control surfaces to neutral, but in my experience Denis this is not what happens. All the receivers switch to hold last command on each control surface (not sure about flaps, haven't tested it) when contact to the Tx is lost. I get the urgency of getting the thing down, but hold last is just a formula for rapid, unpredictable, destruction. Not so kind to people and things either.

Do you have a method for neutralising control surfaces, but cutting the motor, when communication between the Tx and Rx fails?

Jonathan, one crumb of hope. I have found with Spektrum that getting the manuals for systems bigger/more expensive than the one you are holding generally reveals extra, relevant, information. It's not so reliable now that the Tx's are being upgraded again, but can still help. It's no better with the other big names. I have a chum so distressed by Futaba documentation that he spent a major effort writing a coherent book of 'how to' about just one of their transmitters. It's a good little earner, but stems from the same issues we Spektrum users enjoy.

[Trevor Crook]

The main purpose of a failsafe is surely to prevent the model from entering the airways, or flying a long distance. Any setting of control surfaces will have a result largely depending on pot luck. I certainly wouldn't change radio brands just for a fancier failsafe.

[ChrisB]

The way I see this thread going is similar to that of a heated debate between David Boddington and Keith Mitchell in the monthly letters pages of the magazines back in the 90's (before the mass market internet days)

In terms of how you set a preset fail-safe, it depends on the manufacturer and the type of receiver available by from that manufacturer.

In the old days when everyone used 35mhz, there were two options types of receiver protocol PPM or PCM. All PCM receivers allowed for a fail-safe. PPM receivers enabled a mechanical fail-safe to be used i.e. a third party black box dedicated to cutting the throttle.

Nowadays, with virtually everyone using 2.4, most receivers and transmitters contain the ability to go to fail-safe. BUT each manufacturer and receiver type will have its own process.

Spektrum for example has a couple of different options. Small receivers the 4 channel and 6 channel receivers only allow for 'hold' and throttle cut/idle. The larger receivers, 8 channel upwards allow for 'hold' and 'preset'

Read the instructions and reviews and ground test and all will become clear as to what the receiver is capable of doing. Sadly Spektrum fail to have preset on all its receivers.

Going back to the discussion that took place in the 90's. David was of the view that if a model went into fail-safe it should be immediately put into a spin and the engine stopped. That way the model would crash as quickly as possible in a small envelope. Keith was of the view that the engine should be put put to idle and the control surfaces put to neutral. Therefore the idle engine would act as a flywheel and therefore a brake, as impact damage causes more damage than superficial cuts and bruises. AND the model would slowly descend. Keith was also of the view that most fail-safe occurrences or glitches are so fast that by the time the aircraft has reacted you've regained control and so a spin would both destroy a model and cause more risk than it staying in the air and be safely recovered.

I'm with Keith and set all my suitable Spektrum receivers to control surfaces neutral and throttle idle and a 'clean' airframe.

CB

[Chris Bott - Moderator]

I have a combined Rx/Stabiliser that can be set so failsafe is Thr cut and self level.
This will right a model from any attitude.
So what are folks feelings on that? Could it be a bad thing if a model flies a long way in a straight line?

Edited By Chris Bott - Moderator on 23/01/2017 23:17:46

[ChrisB]

If the throttle is cut and the wing level it will only sustain flight for a short distance before it either stalls or crashes.

[trebor]

I lost a plane just after take off, turning to the right still climbing to fly down the back of the field. I ended up with cut engine and in a sycamore seed spiral spin crash due to "hold last command" Shame it might have glided down better if the ailerons were at neutral with the possibility of re connecting if it had stayed up a bit longer

[ChrisB]

A chap at our club crashed a plane and he asked why the failsafe hadn't activated. It turned out the battery had failed....no battery...no failsafe

[Chris Bott - Moderator]

ChrisB, the autolevel continuously autolevels the model both in roll and pitch.
I agree that if the attitude it holds causes speed to bleed off then it might stall, and probably do a series of stalls. I will try it soon by setting autolevels and cutting the motor.
But you can set the pitch angle it holds. So say it's a glider, set at a pitch angle that gives a slow gentle glide.
Is Mr Bodfington right that we should get the model down quick, within our flying boundary. Rather than let it sail on to a location unknown.

[MattyB]

I always set a smidgeon of rudder into my f/s plus throttle idle (if it's powered). Rationale - after a power failure (which f/s won't help with anyway) the most likely failure of a 2.4 system is blanking of the aerials. If you have set up your aerials correctly and your model is not pure carbon(!) almost any change in aspect should improve your chances of getting it back, even a slow arc due to a spot of rudder trim. I saw this work on the field for someone else a few years ago and have done it ever since; YMMV.

Edited By MattyB on 24/01/2017 00:26:13

[OZ e flyer]

The Spektrum website has handy instructional videos relating to failsafe. I think it's linked in the AS3X rx section.

TP

[Chris Bott - Moderator]

I seem to remember some Spektrum receivers having something called "Smartsafe"

This has 2 quite different actions.

1) when Rx is turned on but is still establishing connection to TX (or TX is off) all channels go to positions set when binding.

2) When signal is lost, Throttle goes to pre set, all others hold.

This is why Spektrum always recommended re-binding after surfaces have all been set up and centred. It also helps keep things like retracts where you want them during switch on, etc.

Edited By Chris Bott - Moderator on 24/01/2017 08:11:39

[Jonathan M]

Interesting debate, but not sure a one-size solution fits all...

My fleet has different specific requirements, so I've done some further research. Only the higher-end of the Spektrum RX range will allow 'pre-set' failsafes, but there might be a way around this challenge on their lower-end receivers.

• BLASTER DLG with AR620 full carbon RX - this has the option of a 'pre-set' failsafe (just a question of re-writing the instructions on a scrap of paper until I understand them!), so I can set some left rudder and full landing flaperons to slow and give me plenty of time either until signal recovers... or for the chase!
• ACRO-WOT I.C. with AR610 - this will only neutralise surfaces and cut engine, but I'd ideally like fast-idle (for later resumption of throttle if the signal recovers) with slight rudder and slight up-elevator or landing flaperons to help confine model in the vicinity.
• MIDDLE-PHASE AILERON sloper with AR400 - same limitations as AR610 above, however don't imagine any sort of 'pre-set' would be much use off a cliff!

Could the way around the problem with these earlier non 'pre-set' capable RXs be to temporarily fiddle the sub-trims etc and re-bind, then return trims to normal?

[Martin McIntosh]

If I may chuck in my 2P worth here, my first propo. set was a Stavely analogue which by its very nature put the throttle to off and the other controls to full deflection (up and right) with only even a brief signal loss, which happened frequently. Not good if the model is low inverted. Quite honestly it was a nightmare, so if anyone is thinking of doing it this way then I urge you not to.

If you set F/S to `hold` you will probably not even notice a short loss. I use preset, but on my JR this only takes place after a 2 sec. delay which is a long time flight wise.

It did save a 44" Spitfire twice due to battery cell failure and kept coming in/out as the pack recovered.

On a much larger version, nothing could have saved it because of a power short (twin batteries/switches). It stayed on its vertically upwards path until gravity took over.

I now use a rather more sophisticated power set up to minimise the risk of that occuring again.

[Cuban8]

Then of course , we had the very colourful figure in the model trade (those of a certain age will remember him very clearly) who used to sing the praises of the radio sytem that he produced and its parachute recovery failsafe..........

[Denis Watkins]

When that model flew out of control on Southport Beach, veering to the left , it very nearly landed on my car parked along the runway.

[Andy48]

I have to say I was very disappointed in this article. It focused on just Hitec, Multiplex and Spectrum. By concentrating on just these thee makes it ignores the groundbreaking failsafe system implemented on the OpenTX. One which all other manufacturers will eventually follow, first in high end sets, then becoming mainstream.

• OpenTX will first warn if a failsafe is not set each time a model is loaded.
• OpenTX failsafes are independent of the binding process.
• Any of the 16 channels can have a failsafe set to any value independent of other channels. How does one cope with multi-engine models when each engine is linked to a different channel?

One unique feature of OpenTX is to be able to have a plane fly in the air and adjust the trim in flight to get a steady glide down without power, or perhaps a tickover setting, using whatever controls needed and then at the flick of a switch program those as the failsafe settings.

Then, of course, with later FrSky receivers, OpenTX reports back verbally when the signal strength received is getting low, so one has plenty of time to turn and avoid losing the signal in the first place. Prevention is far better than cure!

[Don Fry]

I'm with Boddo, crash in safety. I would point out that the troubles our free flight brethren are having with landusers, revolves round an inability to stay within the site, and hence subjecting non consenting members of the public to risk.

The plane is not the primary object to be protected. Many sites size enables throttle cut/idle, all else to neutral while maintaining acceptable safety, i.e., it comes down in the area you can see is unpopulated. But have a thought for a nice big turbine powered jobbi, making a turn towards the crowd. You have to be sure it falls short of the barriers to the croud, lest you need coffins.

[Cuban8]

Please don't get me wrong, the failsafe facility on current radios is a vast improvement over what we had in the old 35Mhz days (nearly all non PCM sets as standard IIRC) and its only a good thing to inform modellers regarding its correct use and their legal responsibilities. However, what also does need to be driven home is the need for a good radio installation in the first place, so that it becomes unlikely that the failsafe will be triggered.

I sometimes still see receivers stuffed into models with the aerials bent to all sorts of odd angles and no thought given to the shielding effects of other components in the model. The notion of an adequate power supply is still a mystery to many flyers - and despite many good articles over the years and the internet being awash with information, a few modellers are still tripped up by relatively simple errors that either leave them with a busted model, or unjustified criticism of their gear.

Perhaps more on correct radio installation and basic electrical knowledge (relating to model radio systems) should be formally included in the 'A' test?

[Don Fry]

Careful Cuban 8, sense might break out.

[john stones 1 - Moderator]

Already is C8, why would an Examiner be taking a test for someone who stuffed his gear in a model ?

John