[NSRCA-discussion] Ideas on radio beserkness-cause of crash??

Tue Sep 2 15:11:23 AKDT 2008

Possibly everything just started with elevator flutter, possibly from a broken hinge.  If it was violent enough, and it there was some common mounting platform to the throttle servo, maybe that tray broke loose and started thrashing the throttle.  Last failure on the ailerons, maybe a stressed elevator/rudderthrottle servo overloaded the power bus enough to cause the receiver decoder to not be able to send a decent quality signal, or maybe the voltage was just pulled too low to allow the aileron servos to process a good signal properly. All speculation, but it's a possibility. Tough loss no matter what happened.

Ed

----- Original Message ----- 
  From: Keith Black 
  To: General pattern discussion 
  Sent: Tuesday, September 02, 2008 11:24 AM
  Subject: Re: [NSRCA-discussion] Ideas on radio beserkness-cause of crash??

  I was standing next to Gray when this occurred. What I observed didn't look like a battery failure because the plane began violently oscillating in what appeared to me to be in pitch. This oscillation was so severe that I thought the plane was experiencing flutter. I told Gray to cut the throttle, at which point he said he already had. I looked at his transmitter and the throttle stick was indeed all the way down, however, the engine continued oscillating from high to low. I also looked at his battery meter on his TX and it was well into the black. A couple of times I thought the plane was going to fly off into the distance in this out of control manner but thankfully Gray was able to keep it close to the field.

  What's puzzling are the following:

  1. If it were interference the PCM would have gone into lockout.

  2. A combination of in and out of lockout fluctuations would not cause the throttle to go up and down since the throttle stick was down and the lockout was set to idle.

  3. If it were RX battery related I would not expect it to oscillate the control surfaces and the throttle, unless the RX freaks out at low voltage.

  Therefore, I believe this was some type of radio related failure either on the TX or RX side, most likely the RX. 

  One last thought, I have heard people report a bad servos in the system making all the other servos behave badly. Maybe someone has some feedback on this.

  Keith Black

  ----- Original Message ----- 
    From: Gray E Fowler 
    To: General pattern discussion 
    Sent: Tuesday, September 02, 2008 9:24 AM
    Subject: Re: [NSRCA-discussion] Ideas on radio beserkness-cause of crash??

    Hey Anthony 

    Never set up that warning function. Several people have indicated a low battery. Lance thinks fractured crystal...10 years old, stored in my garage at 105F to 25F or so. Every battery failure I have seen (none were mine) the radio flat out quit. Lance and I are going back out today, better equipped (long pants-machetes!!!) If I find it I can re-test the battery..It tested about 150 MAH of its rated capacity, but I do not have the tester drain the crap out of the volatge. 
    Man that plane flew good....9 lbs 15 oz...My skills are so deteriorated. 

    Gray Fowler
    Senior Principal Chemical Engineer
    Radomes and Specialty Apertures
    Technical Staff Composites Engineering
    Raytheon 

          Anthony Romano <anthonyr105 at hotmail.com> 
          Sent by: nsrca-discussion-bounces at lists.nsrca.org 
          09/02/2008 09:18 AM Please respond to
                General pattern discussion <nsrca-discussion at lists.nsrca.org> 

         To General pattern discussion <nsrca-discussion at lists.nsrca.org>  
                cc  
                Subject Re: [NSRCA-discussion] Ideas on radio beserkness-cause of crash?? 

    Hi Gray,
    What a huge bummer. Did you have the low rx alarm function turned on? On the Stylus that is a switchable function that will drop the throttle to alert you to a low rx voltage. Now I am paranoid and have to go check mine.
    Have heard of similiar "brown out" type of behavior with a Nimh rx battery failure. Hope you can recover the aircraft. This time of year the growth in most places can swallow anything.
    Many solid flights for almost ten years on my Stylus but it is serviced every winter.

    Anthony

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    To: NSRCA-discussion at lists.nsrca.org
    From: gfowler at raytheon.com
    Date: Tue, 2 Sep 2008 08:30:17 -0500
    Subject: [NSRCA-discussion] Ideas on radio beserkness-cause of crash??

    Guys 

    Yesterday on my 4th flight of the day my PCM Stylus went nuts. PCM program was set for idle throttle and about 5-6 clicks(trim wise) of up elevator-all other surfaces neutral, and this was tested as such by turning off the transmitter.  As I passed by center I noticed that I could not gain altitude and the the throttle started going from idle to high...then ailerons started oscillating small left-right deflections. I cut the throttle to the kill position but the engine persisted up-down bursts. I was able to do a 180 degree turn with aileron coming back to center...never losing altitude, but unable to change the altitude,elevator seemed unresponsive. As I passed by center again I was losing more and more control. The plane flew over the wooded area south of the field at about 200 feet high, I could not turn and the ailerons rolled the plane upside down and it went straight down into the trees. This whole episode last about 45 seconds. Cannot find the plane, and remnants of Gustav are headed my way. 

    Plane was new had about 10 flights on it. 

    New battery..NiMH 5 cell pack -no regulator (ran 5 cell packs for years, no regulator) 
    Reciever-1999 Stylus PCM-never crashed, wrapped in foam 
    New switch 
    Transmitter-1999 Stylus, never been serviced, never had problems 

    What would cause a PCM receiver to do such a thing? If I had and intermittent signal, once the receiver did get a signal the only two throttle signals should have been idle (PCM hold) and off (transmitter).  I am going to send the transmitter in just to get checked. 

    Thanks guys....

    Gray Fowler
    Senior Principal Chemical Engineer
    Radomes and Specialty Apertures
    Technical Staff Composites Engineering
    Raytheon

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