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All Forums >> Radios, Batteries, Clubhouse and more >> The Clubhouse >> Mysterious Spektrum system crash.
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Mysterious Spektrum system crash. - 7/2/2008 9:41:13 PM   
Capt Jim


 

Posts: 1116
Joined: 4/14/2002
From: Boca Raton, FL, USA
Status: offline 		My friend was flying his very nice biplane, using his trusty Spektrum DX-7 system, and the 821 servos....all was going very well, until coming in on final...throttle down...plane nice and level and descending toward the runway, when suddenly, for no known reason, the plane went into what appeared to be a full down elevator condition, from about twenty feet high, and smashed itself on the paved runway. After crash examination finds that the 6 volt battery was still fully charged, all linkages were still intact, all servos acted normally.....what happened??? and it wasn't just dumb thumbs...we are baffled by this event. What could have caused a down elevator command to occur? There were a few dark storm clouds in the area but no rain etc had yet begun at that time. Any ideas out there?

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Captain Jim
       Post #: 1

RE: Mysterious Spektrum system crash. - 7/2/2008 9:49:11 PM   
Dorsal


 

Posts: 248
Joined: 4/21/2005
From: Tracy, CA, USA
Status: offline 		There would seem to be a miniature Black Hole, or at lease a small Neutron Star that had crossed paths with your plane at that exact moment. Bummer!

(in reply to Capt Jim)
       Post #: 2

RE: Mysterious Spektrum system crash. - 7/3/2008 12:35:06 AM   
outdoorhunting


 

Posts: 491
Joined: 9/22/2006
From: Kokomo, IN, USA
Status: offline 		How old are the recievers? How many servos? The reason I'm asking is a buddy of mine was flying his biplane and lost it.( It was at the end of a flight,1 last round & he had been working the plane pretty hard. All of a sudden he said he lost contact with the plane. We didn't know what to think. It couldn't have been a hit he had a SPECTRUM !!! Come to find out, he called Spectrum & it makes sense, the battery voltage was low at the time it crashed. When the older RXs recieve below a certain voltage they shut down for 2 seconds & then reboot & come back on. I know you said you checked your bat & had a good charge. How long was it between the crash & when you checked it? As you know a battery may show a decent charge, although 20 minutes before, at the end of the flight, landing, using all high power servos, it could've had a lot lower charge in the bat. Although the plane is lost, not all is lost. They said they have a fix, & it will only take 2 milliseconds for it to reboot. That's the difference between
saving a plane & losing it" This is second hand info, but it's deffinitely worth checking out. May the Sectrum is not as fool proof as they say. For me, I'm sticking to my little old Futaba for a couple more years !!! Good luck


< Message edited by outdoorhunting -- 7/3/2008 12:39:25 AM >

(in reply to Capt Jim)
       Post #: 3

RE: Mysterious Spektrum system crash. - 7/3/2008 1:14:35 AM   
Capt Jim


 

Posts: 1116
Joined: 4/14/2002
From: Boca Raton, FL, USA
Status: offline 		Most of us know that Spektrum receivers will shut down when they see a low voltage....something below 4 volts...and approaching 3.5 volts. This battery pack is a fairly new 6 volt 5 cell NiMh pack, rated at 2700 Mah, and fully charged just before flying, and only approximately ten minutes on the flight. This is a lightweight plane running four Spektrum 821 servos....hardly enough to deplete the battery in such a short time. After the crash the battery registered 5.9 volts on a loaded digital voltmeter. We can reasonably assume it was not a receiver power loss. Additionally, the receiver did not hold the previous elevator position, but rather ordered full down elevator...with no other servo command in evidence. That is...no roll or yaw was introduced as it dove down.


_____________________________

Captain Jim

(in reply to outdoorhunting)
       Post #: 4

RE: Mysterious Spektrum system crash. - 7/4/2008 5:02:03 AM   
chashint


 

Posts: 913
Joined: 1/1/2002
From: Rowlett, TX, USA
Status: offline 		Here is another Spektrum story ...
Two weeks ago I watched a giant Rascal take off and begin a shallow climb out. Everything was looking very normal. At this time the plane was less than 15 feet off the ground and was flying well. As the initial left turn into the pattern was begun we heard the engine "burp" and then immediately recover. At this point the pilot had no control of the plane at all. It began to roll right and climb steeply, then it rolled right, went inverted and slammed into the runway at full throttle. The plane was a total loss. There was no explaination for it, the plane simply stopped responding to the radio. Of course the servos still attached to the RX worked fine after the crash.
This entire radio system has been sent to the service center for evaluation.
As more of these systems become deployed in the field there will surely be more reports of unexplained failures.

_____________________________

regards,
Charlie

(in reply to Capt Jim)
       Post #: 5

RE: Mysterious Spektrum system crash. - 7/4/2008 11:24:50 AM   
Capt Jim


 

Posts: 1116
Joined: 4/14/2002
From: Boca Raton, FL, USA
Status: offline 		Just to try and keep this thread in balance, I have to say that I have never personally encountered a single failure with either my Spektrum DX-7, or my JR 9303 2.4ghz radios...and that is after several hundred flights in an assortment of 10 different planes, over more than a year of flying. I trust the systems completely and would never ever even think of going back to the extremely vulnerable 72 mhz gear.

That being said...I am wondering if the system is subject to the effects, if any, of a lightning strike, perhaps many miles away. That was the only quick possibility we could think of surrounding this issue....but of course every servo acted fine after the crash..still wired up and functioning even though the airframe was functionally destroyed and the motor broken in two.

Another thought being offered is wind shear...and this sounds like a hell of a stretch...but we read that wind shear doesn't require any wind. The effect can apparently be brought about through disparate temperatures. Could this have been the culprit? It was a very hot humid day, ambient temperature in the low 90's, and no doubt there was an elevated temperature directly above the big asphalt runway.
We may be grasping at straws here, but trying to leave no stones unturned in discovering a solution to why it happened.
Thanks for all your comments.


_____________________________

Captain Jim

(in reply to chashint)
       Post #: 6

RE: Mysterious Spektrum system crash. - 7/5/2008 5:04:07 AM   
rcjetflyer0718-RCU


 

Posts: 41
Joined: 12/12/2001
From: Fontana, CA, USA
Status: offline 		5.9 volts on a 2700mah 5 cell battery is low to me, on my 5 cells if I get a reading below 6.1 I recharge it or cycle it to make sure of its capacity. If its below 85% I dont use it anymore.

(in reply to Capt Jim)
       Post #: 7

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