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

[Ron Van Putte]

Regarding the "last thought", this happened to me many years ago.  I  
was performing a 4-Point Roll when the airplane stopped rolling at  
the third point and crashed.  After having the transmitter and  
receiver serviced, I was installing the same servos into a new  
airplane and was doing a bench check.  As I was slowly putting in  
aileron,  the whole system locked up.  After I shut off the receiver  
and turned it back on, the system behaved normally.  However, I could  
repeat the failure by slowly approaching the same aileron  
deflection.  Each time I got to "that spot", the whole system would  
lock up.  Now, Gray's symptoms were not the same, but it demonstrates  
that a servo can take down the whole system.  I'll leave it for you  
electronics experts to explain why.

BTW, the system was not a PCM system, it was an FM system, a Kraft  
KP-7Z, the "top of the line"  back in the 1970s.  I still have that  
old servo as a reminder to check the servos too.

Ron VP

On Sep 2, 2008, at 11:24 AM, Keith Black wrote:

> 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
>
>
>
>
>
> 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
>
> Get ideas on sharing photos from people like you. Find new ways to  
> share. Get Ideas Here!_______________________________________________
> NSRCA-discussion mailing list
> NSRCA-discussion at lists.nsrca.org
> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>
>
>
>
> _______________________________________________
> NSRCA-discussion mailing list
> NSRCA-discussion at lists.nsrca.org
> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
> _______________________________________________
> NSRCA-discussion mailing list
> NSRCA-discussion at lists.nsrca.org
> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion