Fail-safe settings for control surfaces

[Dave Reaville]

Hi Larry

Having had a TX failure, I know from experience the utter helplessness that a pilot feels when his plane is no longer in his control. It sucks big time and I do not wish it on anyone. The most important thing is to ensure the safety of  everyone around you as the plane is now simply a projectile on an uncharted course. 

These are my thoughts on "Fail Safe" settings... no one else's.

First and foremost, I consider this a "failure setting" hence the title "Fail" .... not some sort of "glitch-setting" setup to get my plane to maintain a path of flight. If your looking for a "glitch safe" setting I don't have any answers...sorry.

Now following the "Fail" part of your dilemma (i.e. your TX has failed for some reason) comes the "Safe" part. This is setting up your controls to make the airplane do a controlled "arrival" without 1) killing or injuring anyone and 2) causing any property damage. Remember the plane is going in regardless and, unless your on short final when the failure occurs (not likely),  your going to probably lose the airframe.  The intent is to not loose anything else.

Once you come to that realization, the set up is easy. I have a spin programmed into mine. Not a fast one that we see in competition but a slower, winding descent that will cause the aircraft to arrive somewhere within the box (which is where I fly 98% of the time).  Slight right aileron, slight right rudder & some up elevator with the throttle at Idle.  Will this save my plane? No. Will it provide the most safety for everyone around? I believe it will.

For those that have PCM RX/TX's and have no Fail Safe setup whatsoever then your odds of failure equalling disaster are high (same as non PCM types in fact).  For those with Fail Safe set to "steady state" with idle then your a little better off as the plane will likely maintain a relatively steady path until impact with whatever/whomever it hits.  Remember you have no control at all.  And for those like myself with the spin setup, I have somewhat better odds of containing the carnage as it's going in within the box. Last time I checked most of the pattern boxes where devoid of obstacles (cars/people etc)  

Now under some circumstances the "Spin" scenario I use may not give me a lot of time but I would plan to do a couple things to get my plane back under control. 1) Make sure the TX is "On" and you didn't adjust the trim's with the "On" switch.... seen it done:-) 2) push/hold the antenna into the TX (might be a contact or the antenna has twisted loose... seen it done.) 3) Yell your frequency out loud as someone may have turned "on" accidentally. (Or you forgot to tag up yourself and he's on legitimately ... seen it done. )   

Remember PCM Fail Safe is not the be all and end all. You could find yourself in equal trouble when the RX battery dies because you forgot to charge/check the voltage or the RX fails. It just gives you an way to help prevent possible disaster when the TX fails, nothing more.

These are my thoughts and I'll leave it to you and anyone else out there to decide how they want to have their plane react when there is a hard TX failure (not glitches). 

Safe building & flying,

Dave Reaville
NSRCA I-VP
Canada West District
NSRCA 3156
MAAC 56510 
http://members.shaw.ca/patternwestnews/   

----- Original Message ----- 
  From: L Caldwell 
  To: discussion at nsrca.org 
  Sent: Monday, May 16, 2005 7:03 AM
  Subject: Fail-safe settings for control surfaces


  Hi All,

  What is the general concensus for the best setting for the control 
  surfaces on a pattern plane, and why.  I'm going to be put a PCM 
  receiver in my plane, primarily for the throttle fail-safe, but I'm not 
  sure what would be best for the control surfaces.

  I would like to have the safety of the onlookers, other fliers, and 
  field neighbors as the main priority, but still have a chance to recover 
  the plane if it comes out of failsafe.

  I've considered these options:

  1) Low idle, controls at neutral but with a slight amount of up 
     elevator.  That might be a good way to see brief lockouts, but
  the plane could travel a long way if it stayed locked at at high
  altitude.

  2) Last good signal doesn't seem like a good idea to me if it
  stays locked out.  You could get anything there.

  3) This seems safest for the crowd, but probably bad for the future of 
  the plane.  Low idle or engine off, full spin entry on the 
  controls.

  Any better ideas?

  Larry Caldwell
  Brookland, Arkansas
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