Failsafes, January article

[Cuban8]

Posted by john stones 1 on 24/01/2017 11:36:02:

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

John

Yep, reference to the BMFA safety codes will have the information advising good installation and adequate power supply. However I'd like to see this info tested for in the 'A' as a compulsory part rather along the lines of the recent legal stuff. Depending on the examiner's choice of questions from the BMFA safety codes, this whole vital area could be missed out.

As for poorly installed gear in a 'plane presented for a test, AFAIA, there is no requirement for an examiner to physically inspect how well a model is constructed in detail. This was something that I raised at an Examiners workshop, and the thinking was that the pilot in command (the candidate) was responsible for ensuring that the flight could be made safely.

 

Edited By Cuban8 on 24/01/2017 12:06:06

[ChrisB]

Posted by Donald Fry on 24/01/2017 10:57:59:

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.

It is very rare that failsafes cause signal loss for more than a second or two. If its longer that then its usually another cause. Therefore a model flying conventionally in failsafe at idle is safer than being put in a spin. Its maintaining forward flight but at idle its gently descending in a predictable direction. By switching off the engine/motor and spinning the model in it will increase airspeed and the model might end up crashing within the confines of the field but that could be the pits, the car park or the club hut. What if the model won't spin, or it breaks up?

As i'm sure we've all done, put a model in a 45degree dive at idle and it will reach terminal velocity and no more. Deadstick it will exceed the idle speed and therefore any impact speed will be far higher. Its impact that causes the most injury.

Its one of those subjects that will always generate differing opinions.

CB

[Chris Bott - Moderator]

Posted by Cuban8 on 24/01/2017 11:12:24:

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?

I do wish there was a "like" button on this forum.

[Ian McDowell]

Thanks Tipsy. Anything but intuitive that website, but knowing there was a video I eventually found it. Anyone interested follow this link (**LINK**), video step 13. There is a very discreate arrow to the side of the bottom panel that shows more videos.

Other research reveals that Dallas Doll has an AR636 Rx. Mine is set to Hold/Cut and that appears to be fixed until I get a programming cable. However a chum at the field today checked his Visionaire (AR635 prefitted), which appears to have been factory set to allow pre-set and cut. Nice one Spektrum. Top marks for inconsistency.

Time will tell if this process is true of the UMX AS3X Rx's.

You have been warned. Whatever your preference for failsafe settings, on this limited evidence you can't assume you know how the Rx is set without a test.

The setting process is also radically different to anything in any Spektrum manuals I have read, and different from the guidance in this weeks RCM&E.

The debate about what failsafe is desireable is useful. But I am still no wiser about how to set anything other than Hold/Cut (in fact I can't avoid setting Hold/Cut) in a 'standard' servo. I haven't found an equivalent video/page for non AS3X Rx's yet, but will persist.

[Trevor Crook]

I thought the article was pretty good, and quite generic. Of the four pages, less than one gave examples of how to set failsafes on three brands the author was familiar with, so I don't consider it focussed on them. It did inspire me to have a little play with an AR6210 I had spare, which doesn't seem to allow programming of functions other than throttle. Must try one of my 8000s.

It also made me re-read the rx instructions, because I hadn't realised, or had forgotten, that there is a red flashing "hold" led that you can use to check your installation is sound.

[ChrisB]

AR400

AR400 Failsafe • Prevents unintentional electric motor response on start-up. • Establishes low-throttle failsafe if the RF signal is lost. • Removes servo output pulses to all channels except the throttle channel during failsafe. • Failsafe position is stored via the throttle stick position on the transmitter during binding. HOW AR400 FAILSAFE WORKS Receiver Power Only • When the receiver only is turned on (no transmitter signal is present), the throttle channel has no output. This prevents arming of the electronic speed control. Shown using a separate receiver pack. The battery can be plugged into any open port except the Bind port. Shown using an ESC/BEC and flight pack. EN 9 • All other channels will have no signal output. Some analog servos may coast slightly, even though no signal is present. This is normal. After Connection • When the transmitter is turned on, and after the receiver connects to the transmitter, normal control of all channels return. • If a signal loss occurs, the AR400 Failsafe drives the throttle servo to its preset failsafe position (low throttle) that was set during binding. • All other channels receive no output pulses/commands, and are not active during failsafe

AR6210

SmartSafe Failsafe The AR6210 features SmartSafe failsafe. SmartSafe is ideal for most types of aircraft. With SmartSafe, when signal is lost the throttle channel only is driven to its preset failsafe position (normally low throttle) while all other channels hold last command. • Prevents unintentional electric motor response on startup. • Eliminates the possibility of over-driving servos on start-up by storing preset failsafe positions. • Establishes low-throttle failsafe and maintains last-commanded control surface position if the RF signal is lost. Receiver Power Only • When the receiver only is turned on (no transmitter signal is present), the throttle channel has no output, to avoid operating or arming the electronic speed control. • All other channels are driven to their preset failsafe positions set during binding. Note: Some analog servos may coast slightly even though no signal is present. This is normal.

AR8000

SmartSafe™ Failsafe The AR8000 features SmartSafe failsafe. SmartSafe is ideal for most types of aircraft. With SmartSafe, when signal is lost the throttle channel only is driven to its preset failsafe position (normally low throttle) while all other channels hold last command. • Prevents unintentional electric motor response on start-up. • Eliminates the possibility of over-driving servos on start-up by storing preset failsafe positions. • Establishes low-throttle failsafe and maintains last-commanded control surface position if the RF signal is lost. Receiver Power Only • When the receiver only is turned on (no transmitter signal is present), the throttle channel has no output, to avoid operating or arming the electronic speed control. • All other channels are driven to their preset failsafe positions set during binding.

AR9000

Failsafe functions The Powersafe features two types of failsafe: SmartSafe and Preset Failsafe. SmartSafe This type of failsafe is recommended for most types of aircraft. Here’s how SmartSafe works. When the transmitter and receiver are turned on the receiver connects to the transmitter and normal control of all channels occurs. If loss of signal occurs, SmartSafe drives the throttle servo only to its preset failsafe position (low throttle) that was set during binding. All other channels hold their last position. When the signal is regained, the system immediately regains control. Preset Failsafe Preset failsafe is ideal for sailplanes and is preferred by some modelers for their glow- and gaspowered aircraft. When the transmitter and receiver are turned on and the receiver connects to the transmitter normal control of all channels occurs. If loss of signal occurs Preset failsafe drives all servos to their preset failsafe positions. For sailplanes it’s recommended that the spoilers/flaps deploy to dethermalize the aircraft, preventing a flyaway. Some powered modelers prefer to use this failsafe system to program a slight turn and low throttle to prevent their aircraft from flying away. When the signal is regained, the system immediately regains control. Programming SmartSafe During the binding process the bind plug is left in throughout the process and is removed only after the receiver connects to the transmitter. After the connection is made, confirmed by operating the servos, the bind plug can be removed. The receiver is now programmed for SmartSafe. Programming Preset Failsafe During the binding process the bind plug is inserted in the bind port, then the receiver is powered up. The LEDs in each receiver should blink, indicating that the receiver is in bind mode. Now before binding the receiver to the transmitter and with the receiver in bind mode, remove the bind plug. The LEDs will still be blinking. With the control sticks and switches in the desired failsafe positions, bind the transmitter to the receiver. Follow the procedures of your specific transmitter to enter Bind Mode. The system should connect in less than 15 seconds. The receiver is now programmed for preset failsafe. Note: Failsafe positions are stored via the stick and switch positions on the transmitter during binding. Receiver Power Only • With SmartSafe or Preset Failsafe, when the receiver only is turned on (no transmitter signal is present), the throttle channel has no output, to avoid operating or arming the electronic speed control. • All other channels are driven to their preset failsafe positions set during binding. Note: Some analog servos may coast slightly even though no signal is present. This is normal.

[ChrisB]

Above is the copied text for each of those receivers taken from the Spektrum manuals.

CB

Edited By ChrisB on 24/01/2017 23:21:24

Edited By ChrisB on 24/01/2017 23:21:48

[Martin Harris - Moderator]

The perennial debate over failsafe setting will go on until we can predict the circumstances of a future signal loss...

Arguably, at a display, throttle cut and spin initiation would be safer as any incident should start well away from the crowd line and the crash is likely to occur on the flying area - a model gliding freely could easily end up in the crowd. For general flying, the main purpose of fail safe is to prevent hazard to full size traffic, so throttle to idle may well be sufficient and allow a chance to recover the model.

I suspect that the CAA and BMFA instruction that specifies only to set the throttle to idle or cut reflects that there can be no correct answer to what to do with the flying control surfaces that will cover all circumstances. 

Edited By Martin Harris on 25/01/2017 00:34:03

[Jonathan M]

ChrisB, thanks for posting the guff on the various Spektrum receivers.

Having read, re-read and re-read again the spec for each of these, I'm now completely clear that none will do Pre-Set failsafe except the very highest spec one. All the others only do variations around basic failsafe and SmartSafe failsafe (which is very little different). In terms of signal loss (rather than start-up situations) both these last two are identical: they just cut the power but leave all control surfaces at their last-command positions.

The best thing then - as per other advice given - is to ensure installations are first-class and TX and RX batteries are kept in excellent shape.

[Don Fry]

I believe, someone may know better, the CAA accepts throttle cut because they have a primary interest that the runaway does not climb into controlled airspace.

[ChrisB]

Posted by Jonathan M on 25/01/2017 06:56:26:

ChrisB, thanks for posting the guff on the various Spektrum receivers.

Having read, re-read and re-read again the spec for each of these, I'm now completely clear that none will do Pre-Set failsafe except the very highest spec one. All the others only do variations around basic failsafe and SmartSafe failsafe (which is very little different). In terms of signal loss (rather than start-up situations) both these last two are identical: they just cut the power but leave all control surfaces at their last-command positions.

The best thing then - as per other advice given - is to ensure installations are first-class and TX and RX batteries are kept in excellent shape.

 

Jonathan

I can confirm that the the AR8000 does allow for preset and is available from some retailers for around £45.

Cheers

Chris

Edited By ChrisB on 25/01/2017 08:33:05

[Trevor Crook]

It surprises me that the failsafe setting method on my 1990s Fleet set hasn't been widely adopted. You just hold the sticks at the desired failsafe positions, and press the failsafe button. The Rx then remembers these positions. You can even do it while flying. Haven't flown on 35MHz for a few years now, but I still have the tranny.

[trebor]

That would be too easy in this day and age of technology, things just get more complicated because they can

[Ian McDowell]

More fool me. The DX7s manual, pp20, is clear that if preset failsafe is available on an Rx you get to it by removing the bind plug after powering up the Rx but before igniting the Tx in bind mode.

Nevertheless, the manuals just seem to sprinkle confusion:

• The AR8000 manual is functionally identical to the AR6210 manual on failsafes, pages 4/5 in both
• Neither refer to a change in the bind mode approach, but maybe that's a transmitter thing
• The AR8000 was not listed by Horizon as being preset failsafe capable in the earlier thread
• However, the DX7s manual specifically says it is, and ChrisB has confirmed it is (have you done it Chris?)
• So, presumably the AR6210 can enter preset failsafe mode. I can't persuade it to, despite following the correct routine and watching the lights
• AS3X capable Rx's (does that include UMX versions?) CAN go to preset failsafe, Not a murmur in the manual that I can find, but the video link is somewhere in a response above

Incidentally the AR8000 is discontinued and replaced by the AR8010T. I can't say that the new Rx's manual is clear about the process though. It seems to introduce yet another binding method involving several pairs of hands? Page 6 if you care.

Or is this odd set of instructions just because some of the most recent Tx's have a menu item for bind mode...so you have the option of switching the Tx on in advance of the Rx?

Oh, help!

[Former Member]

[This posting has been removed]

[Martin McIntosh]

Surprised that no one has commented on the Trident incident. Even with a $40Bn. expenditure they had to blow the thing up when it went haywire. Not even a throttle down and hold last command. Perhaps we should load our models with an explosive charge?

On a more serious note, really there are only a few things which could initiate failsafe:

1) A failure of one cell on a four cell Rx pack causing a brown out.

2) A Rx aerial breaking. A total Rx failure would probably not result in failsafe anyway.

3) A Tx failure.

4) Total signal loss due to interference, unlikely on 2.4 but would apply to 35mHz.

[Former Member]

[This posting has been removed]

[MattyB]

Posted by Martin McIntosh on 25/01/2017 14:58:19:

...On a more serious note, really there are only a few things which could initiate failsafe:

1) A failure of one cell on a four cell Rx pack causing a brown out.

2) A Rx aerial breaking. A total Rx failure would probably not result in failsafe anyway.

3) A Tx failure.

4) Total signal loss due to interference, unlikely on 2.4 but would apply to 35mHz.

As Steve points out the loss of a cell will not cause a failsafe. Either the RX sees enough voltage to operate and puts out commands to the servos based on what it is receiving, or it doesn't have enough voltage so shuts down and doesn't send any signal to the servos. 

You missed the most prevalent cause of a failsafe though - receiver aerial blanking due to a poor installation. This is far more likely than all the others you list put together, and I have seen it quite a few times during crash investigations... "What, you can't just stuff the aerials anywhere? I put mine down the sides of the battery, it's the only place I could get em to fit..."!

Edited By MattyB on 25/01/2017 16:50:36

[Denis Watkins]

I believe Martin is assuming the resistance in one failed cell pulling down the voltage left in the remaining 3 cells below 3v, which is likely. I would not dismiss cell failure as it is not uncommon. And again, would add support to a motor cut failsafe setting, as required by the BMFA

[ChrisB]

Posted by Ian McDowell on 25/01/2017 11:06:02:

More fool me. The DX7s manual, pp20, is clear that if preset failsafe is available on an Rx you get to it by removing the bind plug after powering up the Rx but before igniting the Tx in bind mode.

Nevertheless, the manuals just seem to sprinkle confusion:

• The AR8000 manual is functionally identical to the AR6210 manual on failsafes, pages 4/5 in both
• Neither refer to a change in the bind mode approach, but maybe that's a transmitter thing
• The AR8000 was not listed by Horizon as being preset failsafe capable in the earlier thread
• However, the DX7s manual specifically says it is, and ChrisB has confirmed it is (have you done it Chris?)
• So, presumably the AR6210 can enter preset failsafe mode. I can't persuade it to, despite following the correct routine and watching the lights
• AS3X capable Rx's (does that include UMX versions?) CAN go to preset failsafe, Not a murmur in the manual that I can find, but the video link is somewhere in a response above

Incidentally the AR8000 is discontinued and replaced by the AR8010T. I can't say that the new Rx's manual is clear about the process though. It seems to introduce yet another binding method involving several pairs of hands? Page 6 if you care.

Or is this odd set of instructions just because some of the most recent Tx's have a menu item for bind mode...so you have the option of switching the Tx on in advance of the Rx?

Oh, help!

Yep, I checked my YT Spitfire last night and the 8000 is set to surfaces neutral and throttle idle (preset).

I've just got another 8000 from Nexus for £45 for a 1/4 SE5

[Former Member]

[This posting has been removed]

[Denis Watkins]

Exactly

[Peter Beeney]

Post 1

I think I’ve always considered the term ‘failsafe’ in this context to be a bit of a misnomer anyway, any self respecting failsafe system will automatically go to a preset safe condition in the event of anything in the system failing; and how often can the user ‘adjust’ or perhaps better ‘tamper with’ the various ‘fail’ settings as a matter of course? Using a lift in a building as an example, I suspect that if the power fails when in use there is more than one condition applied which ensures that the lift car stops and remains at a standstill; and no one can interfere with this state, either. If the power fails on a model aircraft the control conditions will stay as they are, it will instantly be totally out out of control and if it just should happen to be a 10lb warbird with a 120 FS going at full chat and it impacts close enough to the pits such some debris finally finishes up there it certainly grabs everyone’s attention a bit smartish… I know this from experience…. All the way through my model flying times and tribulations I’ve never seen a case of genuine outside interference, but I’ve seen a fair few number of power failures, that situation may be (hopefully) improving now, but it still occasionally happens.

A long while ago there was a very serious incident which led to quite a lot of comments and instructions, much of which related to failsafes, at the time this was the latest radio development. We didn’t fully understand much of this because some of it appeared to be contradictory or even impossible to implement anyway. So we decided to do our own experiments and try and decide exactly what the real live effects would be in the field. As it happens, I’d bought a fun fly model second hand with a Futaba PPM/PCM receiver all ready on board, and I also had a FF7 PPM/PCM tx, which I often used as a buddy. I spent time kicking this around until I was conversant with the PCM failsafe procedures and we then tried it with the model up in the air using a second tx on the same frequency. It was a bit windy that day, but with practise I eventually found I could tolerate the interfering signal for up to a few minutes at the time, from well up wind to well down wind although it was always going to finally come down, fortunately it was never ever going to get very far away. We even switched on a second tx at one point, also on the same channel, but that made not an iota of difference. However this little episode did inspire one of my long time friends and inspired modeller that was involved to drily remark “PCM radio sure don’t behave like wot it’s supposed to”. We never did pursue this any further, though, because it seemed a bit pointless. Every case of interference would be different.

I did discover one interesting little snippet on the way though. In the beginning, whilst I was tinkering with this on the ground, sometimes the settings would function ok and occasionally they wouldn’t. At first I thought it was a fault but on really getting into the system I found it was a natural quirk of the FF7 tx/rx. The servo positions were set by holding the sticks in the required positions like as now, this memory was stored in the tx and the info. was sent to the rx as a short pulse, once on switch on and thereafter about every minute. When the combo was switched off and then switched back on again the rx had no settings until it received the first pulse. Usually this was ok, but if I switched the tx on first, (as normal) and then slightly delayed the rx turn on it was possible it had no settings for up to a minute… Which is exactly what my problem was… I considered that this might not be too much of a problem with ic models, from tx on to take off is invariably greater than a minute I would think; but an electric hot liner which is carried to the strip the battery connect up there and launch can be quite swift. So in theory I thought it was possible here to have a short period of flight with no failsafe settings. In those days the PCM radio sent the last good signal to the servo…and the ESC…so full throttle with no control…

I never saw this flagged up or even mentioned anywhere so I don’t think this was ever common knowledge and I’m sure this was all very insignificant at the time anyway, but my personal point is - If there is ever a serious incident for which there appears to be no explanation, could it be down to some arcane and mysterious set of circumstances of which no one is aware, such as this one? And if this situation did happen I suspect it never would be investigated, either…

[Peter Beeney]

Post 2

Regarding the aerial blanking and poor installation stories, I’ve again spent considerable time trying to actually create such a kettle of fish for real but I’ve never managed it yet; but I suppose I could now say I’ve just been unlucky in this respect. I’ve also related in a thread before the story of our stringent full range test (long!) including attempts at interference and aerial orientation. This again has been a total success every time, and that also includes a DX5e with it’s AR500 rx. So I just continue to fly on rewardless regardless…

When I did a low voltage test on the AR500 receiver on two separate occasions I found it went down to 2.7 volts before it locked out; but at this point the servos were also seriously complaining of the cold too, so I arranged to keep them up to 5 volts and just reduced the receiver. Exactly the same result. Oddly enough, when I’d previously done a similar check on a 35 meg set, at the time I was interested in range distance combined with low voltage, I found the receiver still had range at 2.9 volts but ceased working completely at 2.8 volts; so in this case anyway a fail at 0.1V higher than the 2.4!

We live and learn…

PB

[Martin McIntosh]

Steve J,

I am sorry but you are quite wrong here. The nominal voltage of a four cell NmHi pack is 4.8V. A cell going short circuit will drop this under load to less than the 3.7V required by most Rx`s on 2.4 so that the Rx shuts down for while until the battery recovers a bit. Control is resumed until the servos again drop the voltage below the critical level. The sensible thing to do is to use five cells so that this cannot normally happen.

Matty B, see my earlier post to see the effect of a cell failure please.

Rx blanking would surely be for such a short time that you would not even notice it under normal circumstances.

I really think that there is too much hype about so called F/S. There is no such practical thing which you can do to prevent a crash in the wrong area in my opinion.