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Control surface Failsafe settings.


Terry Plumridge 1
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7 minutes ago, PatMc said:

@Jon - Laser Engines, I've limited my responses to be pertinent to the question asked by the OP.

Nevertheless I disagree with your failsafe risk assessment.

 

You always disagree with me on principal so im hardly surprised. if i said the sky was blue you would probably argue about it. 

 

You are right that the OP is talking about a powered foamy glider, and peter echo's a point i already made. The failsafe setting may be variable depending on the model in question and where you fly. A light glider may never be seen again unless its given a nudge towards the ground and for the op zero power and a very slight nudge down might be appropriate. A 20lb warbird or 50cc aerobat on the other hand should have its energy state reduced as much as possible before impact as its a big mass and it will cause a great deal of damage if you dive it straight at the earth and hit something/someone so trying to point it at the earth is not a good idea. 

 

Also consider a turbine. Do you want to drive that into the floor and have it explode, or would a engine off glide be a better choice to give the turbine a chance to cool and perhaps keep the crash soft enough to prevent a fuel tank rupture and ensuing fire. Deploying the air brakes might also be prudent and this would apply to a glider as well. 

 

Critique my risk assessment all you like, but you will find that i have actually considered more factors than may be apparent at first glance. with all respect to John, i cant see an argument for a bunch of down elevator. Not just because i think its dangerous to drive a model into the ground, but because the radio could fail at any time and at any attitude. With a model inverted a heavy pitch down command would make it climb, and if high it might flop around all over the place in an unpredictable way. Setting the controls mostly neutral and cutting power will give the model a predictable straight flight path no matter the attitude at which the radio lets go. Predictability and time gives you options to either get out of the way and/or regain control.  

 

One other point worth mentioning is that the failsafe is your last resort anyway. In 30 years of model flying i have only had one failsafe kick in due to a ruptured fuel tank flooding the rx in flight. I was fortunate in that it recovered after 4 or 5 seconds, but in general you should not be having failsafe activations in the first place and its probably better to spend time focusing on a reliable and secure installation of all systems. 

 

Ron, you got any more of those cans mate? i think the first one is empty 

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I don't think we should get bogged down into argument as this subject is, rather like the other thorny subject of system redundancies, one with no single correct answer.  So much depends on the type of model, expected failure situation and flying environment.

 

My personal recommendation for a lightly loaded model as per the OP's question would be throttle closed and spin inputs, simply to avoid an unintentional flyaway and recovery of the model - or its components - in the incredibly unlikely event that failsafe is deployed.  If it has effective airbrakes or is capable of crow braking then that would be a viable alternative in many cases but again, it's model and situation dependent. As Jon says, a heavily loaded warbird is a very different kettle of fish - it won't catch a thermal and drift several miles downwind at increasing height.  Whatever your choice, only the throttle is mandatory and necessary.

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34 minutes ago, Jon - Laser Engines said:

 

You always disagree with me on principal so im hardly surprised. if i said the sky was blue you would probably argue about it. 

 

 

Que ?

I can't remember the last time I expressed an opinion in the same thread as you let alone disagreed or even commented on your opinion in any thread for years.

Ironically I seem to be disagreeing with you now & dare I mention that the model mentioned by the OP isn't a foamy. (oops I've disagreed with you again) ? 

 

 

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of course, with my models with a flight controller & a GPS I can have them return to "home" - the takeoff point, or some predefined coordinate - on failsafe, then either loiter until the battery runs out, attempt to land, or potentially have the radio link restore.

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5 hours ago, andyh said:

of course, with my models with a flight controller & a GPS I can have them return to "home" - the takeoff point, or some predefined coordinate - on failsafe, then either loiter until the battery runs out, attempt to land, or potentially have the radio link restore.

 

Unless there is a tall building in the way, presumably. In which case it would nicely fly into it...... in a controlled manner ? For example, ther are a number of barns and grain silos near our field.

 

Aye, more worms here than under our grass runway - and we have a lot!

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1 hour ago, GrumpyGnome said:

Unless there is a tall building in the way, presumably. In which case it would nicely fly into it...... in a controlled manner ? For example, ther are a number of barns and grain silos near our field.

Well the return to home on signal loss could first be programmed to climb to x height, thus clearing trees and buildings. That’s how I used to programme my drones when filming (legally!) in built up areas or near trees around fields. Having said that, they also had obstacle avoidance but I never really trusted that!

 

Anyway, a bit off topic, I think my failsafe cut in.

Edited by Ron Gray
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8 hours ago, andyh said:

of course, with my models with a flight controller & a GPS I can have them return to "home" - the takeoff point, or some predefined coordinate - on failsafe, then either loiter until the battery runs out, attempt to land, or potentially have the radio link restore.

That's an interesting one, because technically it doesn't follow the ANO which states is a failsafe is fitted it should cut or bring the engine/motor to idle, https://bmfa.org/info/articles/failsafes but CAP 722 states "Make use of any available technology or safety features which may reduce the risk of harm if control is lost" probably another thread discussion. 

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Thanks for the replies, lots to think about. Once I am confident at controlling the model I guess I could get it up to altitude and try different things out. One thought that I have is if I can reduce the motor (electric) speed so that the propellor is turning, but not providing any propulsion, it might act as a brake. Maybe that is already accepted practice, I am learning as I go.

Cheers, Terry.

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