Receiver Choices/PCM fail safe

[NSRCA Canada-West]

Hi Jerry

A couple thoughts on PCM Failsafe for you to ponder. Having been recently through this exercise, I am a strong believer in safety over asset. I.E. I would rather have a plane go in rather than fly in an "unknown" manner and possibly cause property damage, injury or death. This is where you can have some input into what the airplane does when the failsafe mode is activated (by signal loss - Tx failure & RX failure to a degree). 

Many people are reluctant to program it because 1) they don't understand it or 2) they see no need (the equipment works great, why bother!) 3) They believe it's too complicated. 

If everything works as planned you will never, in all likelihood, need it. It's when things go bad (component failure) that it can be an important asset to you and those around you.

For pattern ships we are generally, other than landing & takeoff, in the box somewhere between the 60 degree marks.  We can be high, low, inverted, vertical, in the middle of a roll, on a forty five... pretty much any attitude when things happen. Lets say the TX fails and signal is lost, without an active programmed failsafe, that plane is going in anywhere within a mile or two (maybe more) and at an unknown speed .... not really comforting to me. Most planes probably end up proximate to the field and so nothing gets hurt except for the pilots pocket book. It's the chance that it flies away that bothers me the most. It is, without a doubt, the most helpless feeling in the world to lose control and become a "spectator" to your airplane in the sky. 

I don't profess to know all the best ways to program failsafe but I'll tell you what I do and, if you think it's a good idea, then use it. I program in idle throttle, full up elevator, right rudder and some right aileron that should eventually produce as slow a spin as I can get. For most flying conditions this will cause your plane, regardless of what phase of flight it's in, to come down within the confines of the box or, at worst, the departure/arrival ends of the runway should you be in that phase of flight. Will the airframe survive? No. Will I have an opportunity to save it? Maybe.... depending on altitude & phase of flight that the receiver goes into failsafe. If you are lucky and have time (altitude as your plane spins toward earth) I would 1)Yell out your frequency # in case some inattentive flyer behind you has turned his radio on. 2) Twist your antenna, making sure it's tight (some TX models have removable antennas and it could simply be a connection. Even non-removable antennas can come loose (unscrew) on their own). Try turning your radio off and on (make sure you bring the throttle stick to idle as some TX's have built in safety features to stop you from transmitting with anything but idle stick position (i.e. no full throttle starts). This switch thing may sound silly to some but it's possible to inadvertently turn off your transmitter, either by thinking it's trim (don't laugh I've seen it!) or the switch location is poorly placed under your palm. When you reach down to turn it "off" it may already be there! Turn it on and maybe, just maybe you can get your plane back. If not, it's going to spin in in-front of you rather than flying to a destination unknown.  

Some folks may say that it won't spin in if you doing a knife edge pass or four point roll. No it will probably snap in and be toast before you can say "what the ..." It will not be saved but it will, I believe, not be a danger to anyone's life or limb. Unless of course your doing a "doubleweedon" way outside the box :-)   

First flight I always turn my radio off and test the failsafe feature before taking the plane up (during the range check as I walk back to the airplane). This can catch a wrong failsafe setup or an inhibited failsafe. 

I'll side with Mr. Newman on this and say that a properly programmed, active PCM failsafe is the safest route to go.

I am sure others will add their idea's as to what is best and I look forward to hearing how others set up their failsafe. I am always open to new idea's. 

Some thoughts anyway...... 

Dave Reaville

---- Original Message ----- 
  From: Jerry Wilson 
  To: discussion at nsrca.org 
  Sent: Monday, September 30, 2002 6:36 PM
  Subject: RE: Receiver Choices/PCM fail safe


  I've heard it suggested that the right way to program a fail-safe/hold
  position was to be sure a plane which was no longer under control was
  brought to earth quickly so that the danger was minimized.  In other words
  the fail safe is to protect other people and property, not the operator's
  model aircraft.

  Personally I have not done this and am reluctant to do so.  But they have a
  point.

  Would like to hear comments from the list.

  TIA
  Jerry Wilson
  Houston, TX




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