Fun With ALES Full Throttle Yoke Failure - RC Groups
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Apr 20, 2011, 08:13 PM
Paul Naton's Avatar

Fun With ALES Full Throttle Yoke Failure

I was out practicing today with my ALES plane, when the prop yoke failed at full throttle. Conditions were very breezy with strong but broken late day thermals moving at 15-20kts downwind.

Plane is a modified Aria HLG (more info on the plane here:

I got one of Randy's CAM units last week and have been practicing getting 10 from 600 feet. First flight was a 10 though very turbulent and got low a few times. I didn't want to land so came over the tree line and pushed upwind diving for speed and to get below the wind gradient. Felt some air blow through a few seconds earlier and the plan was to build speed, hit power, accelerate, then pull up hard into the gradient, and go downwind to catch that air and start another 10 minute cycle. I was 40 meters away from myself and hit the power button, still diving slightly.

The plane spooled up quickly, and at 15 feet, I started to pull up going about 60kts. Just then I noticed something leave the plane and a hundredth of a second later the plane pulled vertical, and I saw another object leave the plane!

Plane shot up to 50 feet and I had no pitch control. OK, I now know the motor left the plane, and my CG is now at the trailing edge of the wing. The plane flopped around, and landed in the parking lot, with only some slight v-tail damage.

I found the motor and spinner a hundred feet upwind, with one blade missing. A long search turned up the other blade, confirming the it was not the blade but the yoke that failed. The picture shows the plastic yoke broken at the bolt hole and missing firewall.

Note to self: never use plastic yokes again, especially after you put in a Hi-C battery.
Ordering some new spinners tonight!

Paul Naton
Radio Carbon Art Productions
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Apr 20, 2011, 10:35 PM
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Leadchucker's Avatar
Yow!!! Don't look like your aircraft faired too badly considering.
I don't think I've ever seen a plastic yoke and your's is a good reason to not want to.
Apr 21, 2011, 08:22 AM
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Andy W's Avatar
Is that the one for graupner props? If so, they are designed for 2.3mm shafts (i.e. "Speed 400" motors) and the power they can put out (100W or so)..
Apr 21, 2011, 06:45 PM
turn, turn, turn.
Nice to see your fuse didn't rip completely apart....nice that you found the pieces and discovered the cause.
May 01, 2011, 11:34 PM
OK,so what's the speed of dark
mred3's Avatar
I was told never to use a plastic yoke, so the only thing I buy is metal. Then I forgot to put locktite on the nut and it threw a blade one day because the nut came off. The nose on my Vista didn't come out looking quite as good as yours did.

May 02, 2011, 12:34 AM
Registered User
Originally Posted by Andy W
Is that the one for graupner props? If so, they are designed for 2.3mm shafts (i.e. "Speed 400" motors) and the power they can put out (100W or so)..
Noooo they are not dude.......
May 02, 2011, 08:07 AM
Registered User
Andy W's Avatar
You're right:
8x4.5 CAM Folding Prop, 3.2mm shaft, 38mm spinner, 6mm yoke. The CAM Folding Prop series is for electric airplanes using SPEED 280, 400, 480, 500 and 600 motors, both geared and direct drive.

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