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View Full Version : For Who the Bell Tolls, AT6 Texan


Bad_B
02-11-2008, 06:11 AM
The curse of the pre-maiden photos, pilot error, radio interference, bad BEC, who knows? Alas the e-flight AT6 is no more. Pre flight range check was fine, battery was good too showing 4.21 volts on all 3 cells, motor run up was also fine. Flaps down, throttle firewalled she climbed well, but quickly showed a tendency to pitch head up erratically. I was able to climb to altitude turn back towards me, getting ready to trim her out Ö.then it began; the spiral of death. Hard over 200 feet or so up, the left hand death throes of a bird going in, I was able to cut the throttle, but nothing I could do would stop the death spiral. Both wings sheared off the center panel, motor pushed back into the battery compartment, battery tray into Öwell the area below, 4250 flight power battery looked like it took one from Cassius Clay. Ugly, ugly day.

Iím not very good at failure analysis, other than the fairly obvious, so Iíll chalk this one up to me. I was using my Spektrum DX 7 with an AR 9000 rx and the plane was setup with a Castle 60A ESC with a separate Castle 10A BEC. I had 8 servos (only using 7 as I could not get the retracts working correctly, retract servo was not plugged in) running off the 10A Castle BEC, putting out 6 volts.

Iíll post some pics later. I canít quite bring myself to take some now. I am consoling myself with a few rum and cokes and maybe things will look better in the morning. Oh, Iíll post the pre-flight photos belowÖ.the plane has a couple of coats of Testors dull coat matte finish on it

Brian

Murocflyer
02-11-2008, 06:30 AM
Dang shame Brian, dang shame. Sure was a beauty that's for sure. Was anything salvageable?

Sure is odd that's for sure. I did a search in RCG for similar crashes in the big AT-6 thread (I just used the word "crash") and got some DX7 failures and this one (http://www.rcgroups.com/forums/showthread.php?p=8763641&highlight=crash#post8763641). Can't say it is exact, but sounds close although Sarge never made it up to altitude.

Darn shame that for sure.

Frank

Bad_B
02-11-2008, 08:51 AM
Hey Frank,

Thanks for your kind words. Sad to day Iíve had lockout problems with my DX7 before, but I didnít learn from them. Yes, Iím gonna blame this crash on the rx/tx. Iíve had the DX7 lockout on my little Sea5 and Fokker VII before, but I switched to the Castle 25A ESC and Iíve had no problems since (thinking the BEC dropped below average voltage w/the old SS25 ESC). I was also unsure of running so many servos off a BEC, even thou I wired in a separate DEC, maybe a separate battery pack for the servos would have been better???

I feel Iím a pretty good pilot, getting lot of air time, as Iím retired and the park is 5 min away. I usually get in two sessions a day (weather permitting) off 9, 1425 mAh batteries flying the GP Fokker and SE5a park flyers. I am truly mystified as to why the AT6 crashed, but as a flyer I try to take these things in stride.

I have a JR 9309 and a 790 PCM rx on the way as well as an Onyx sailplane to ease the pain: http://www.soaringusa.com/products/product.htm?product_id=16756&category_id=259 (http://www.soaringusa.com/products/product.htm?product_id=16756&category_id=259). The good news is the Onyx will take batteries I purchased for the Texan. Iím going to switch my little park flyers over to the 9303 too, going old school and getting away from the 2.4 stuff.

I will say that the e-flight kit was great. The fit and finish of the ARF kit was truly first class. I would recommend the kit to anyone interested in a standoff scale war bird. The kit does have a few issues, like having you use self tapping wood screws to tread into aluminum tube. I did invest a lot time and money in the AT6, but it is a lovely ship and it looks good in the air, even going down, lol.

I think the repairs required are a bit beyond what I can do with my limited workshop, but I did buy two AT6 kits, so I might get to building the second one someday.

Brian

Franny
02-11-2008, 10:55 PM
Hi Brad,

Boy, I really feel for your loss. I build mostly scale and would be so bummed if one of them went in. I too fly a DX7 and had a re-boot on my glider that resulted in a crash. I have been using external BECs since and have not had a repeat. A question? Do you think it may have been a CG problem? Tail heavy? Like the battery slid back a ways or something? That would account for the strong pitch up, but I don't know about the spiral. I had a small airplane do that to me, then entered the death spiral a couple times until I push the CG a bit forward. Just a thought. I would hate to think it is the radio as that is all I fly. Did the radio survive? How is it?

Well, have a great time with your sailplane. So sorry for your loss.

Franny

MrMulligan
02-11-2008, 11:59 PM
I just bought one of these EFlite Texans. I find it a beautiful kit and am most interested in why yours went in. I hope you'll let us know when You find out.

Bad_B
02-12-2008, 11:52 PM
Hi All:

Yes, the radio gear and servos all survived. I havenít checked the ESC and the separate BEC or motor yet. The battery tray and the servo tray both pushed in after impact. The retracts broke their mounts and the motor has cracked the firewall. This CG was balanced out to the recommended point in the instructions, the model was nose heavy until I added 3 oz of weight to the back of the fuse, then it looked good. I did use the great planes CG stand I have, so balance should not have been an issue. The only other thing I can think of was maybe an overload condition existed during flight with all 7 servos drawing power while the motor was firewalled. As I stated earlier I was using a CC10A BEC programmed to put out 6 volts to run the servos.

As far as anything mechanically or structurally catastrophic occurring during flight I was unable to tell from my post mortem. I really wish I could get to the bottom of why this plane went in on me as it was rather expensive to outfit, but oh, well.

Iím going to hold off on putting my other AT6 together and focus on trying to get this new sailplane together without the benefit of instructions, should be fun.:blah:

Fly Time
02-13-2008, 11:52 PM
And here's another Spektrum-induced AT-6 crash....

http://www.rcgroups.com/forums/showpost.php?p=9053622&postcount=1852

Sorry to hear about yours. That's a helluva plane to loose on your first flight :(

Airhead
02-13-2008, 11:57 PM
Hey Brian,
Sorry to hear about your crash.:( Hard way to end a maiden flight. Hope you'll be able to get to the bottom of the problem..

Bad_B
02-14-2008, 12:37 AM
Thank you to everyone for their input. Yes, the Texan was a very expensive lesson for me and a bit painful too. I can take the crashes as part of the hobby, but the thing that really gets to me is not understanding why.

Hereís my solution; throw money at the problem, lol. I have a new tx, a JRXP9303 with a P790 rx using a separate battery pack to run the rx and servos. I bought the new tx/rx combo mainly for my new carbon/kevlar fuse on my new sailplane.
I also lost my GP SE5a to Spektrum lockout. Unfortunately, I invested rather heavily in Spektrum rxs: AR6100, AR6000, AR7000, AR9000. I know I can convert my XP9303 to 2.4 and it will bind with the AR series of rxs, but Iíve been burned twice, not to mention the lockouts that didnít result in a crash, so Iím done playing with 2.4 for now. NOW, having said that after I switch over to the new tx/rx, if I continue to put planes into the ground Iíll go out and buy a boat..that way Iíll know why Iím throwing my money away.


Thanks again,

Brian

Fly Time
02-14-2008, 12:49 AM
I have a new tx, a JRXP9303 with a P790 rx using a separate battery pack to run the rx and servos.

I have a JR 7202 synthesized frequency Tx and use mostly Berg microstamp Rx's. Never a problem, and cheaper Rx's than 2.4.

the big O
02-22-2008, 04:09 AM
Hello guys. Sorry about the crash. I saw this thread on RC groups and
thought it had a similar theme.

http://www.rcgroups.com/forums/showthread.php?t=817759

It's a really long read, sounds like the spektrum folks are on it.