APLUS 400 V2 Tail Rotor Problem - RC Groups
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Jan 19, 2007, 12:15 AM
Walkera Crash Expert

APLUS 400 V2 Tail Rotor Problem

Ok Scott, here is a good one for you. As you know, I had problems with the wood blade debacle with the APLUS, but that got sorted when I micromeasured the shaft and spent an hour getting it back to within .001 inches of perfect round on my lathe. After reassembling the bird and doing a couple of slow run ups looking for vibration it was good to go for flight it appeared.

The flights were perfect. Flight 1 was 8m10s with a good solid hover the entire time, Flight 2 was 7m30s and the bird was responding great and it was easily staying within the 3' hover box, Flight 3 went for 8m6s with another beautiful hover. Here is where is sucked.

Flight 4 - 7m5s of a nice hover. After getting off the ground it was responding fine up until the last 10 seconds. It started to rotate right slightly and the gyro was apparently not able to keep it in check. I set a little counter rudder on the trim and then one of the tail blades went past my head. On a good note the bird was set down with no damage to anything other than the tail missing some pieces. I am still searching for the second tail grip and tail blade, but the one that I did find was in fine shape other than not being attached to the helicopter.

So in total I have 40m12s (including the 9m18s from before the wood blade incident) and now I have a downed bird because it appears the tail literally disintigrated. I am including some pics to see if you may have an idea what happened to it.

I am at a loss as to what happened, especially since both tail grips and tail blades were shot off at the exact same time. The poor tail adjustment device and linkages are trashed now as well.

Please tell me you have some of these parts in stock so I can get back to flying soon. It was working so well that I can't hardly believe what happened.

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Jan 19, 2007, 09:21 AM
Registered User
Scott_RC-TEK's Avatar

I have never seen a tail come apart like that.

Ok, time to upgrade that tail to a SJM400 v3 since you're going to have to replace most of the parts anyway and the upgrade is a cheaper route

Get this:

1. http://www.rc-tek.com/us_store/tup00...ade-p1624.html

2. If you need a new tail rotor set, get this: http://www.rc-tek.com/us_store/al201...set-p1576.html

I will see if we can trow in some tail blades for free if we have an extra set. How are you on screws and nuts for the tail blades?

Last edited by Scott_RC-TEK; Jan 19, 2007 at 11:12 AM.
Jan 19, 2007, 10:11 AM
Walkera Crash Expert
My original thought was that the tail grips might have come loose and when one of them came completely out it caused the catastrophic failure seen there. I can only imagine that the amount of weight generated by 15k RPM rotation has to be pretty extreme on the parts. It is annoying because you can clearly see the loctite on the screw that goes into the central hub. I have no idea how it would be able to pull completely out like that. Even weirder that both came out at the exact same time.

I placed my order this morning for the parts you specified. As for screws and nuts I only have one set of them off of the existing blade grip (since I have no idea where the other one landed, I'll find it one day with the lawnmower).

By sheer mystery there was no damage caused to anything else. That is what makes me wonder about the loosening blade grip theory. It would seem that if they came loose that it would cause some other damage or vibration. Everything happened so fast on this that it didn't get a chance to I guess. One theory we have so far that might make sense is the tail adjustment device came unscrewed from the post it screws down onto (which had happened on the second flight causing the tail to stop responding to left control input). Joesnuffie has seen this on his bird as well but never seen it totally disintigrate like this. He says usually it just loses response and you sent it down and tighen the adjustment collar back down.

Thanks for all the help you have given so far. Hopefully this is a one time failure.
Jan 19, 2007, 11:12 AM
Registered User
Scott_RC-TEK's Avatar
Simply weird... I have forwarded your case to the manufacturer for investigation.

Thanks for the order and we are also looking to send you a few extra SJ30005 M2x8 countersunk screws and SJ70001 M2 nuts so you can get the bird back in the air.

I can't guarantee some tail blades, but we will see.

Jan 19, 2007, 11:35 AM
Walkera Crash Expert
If they want to see other pics of the parts or want the parts themselves I can send them along. Anything to help design a better bird!

Thanks again for all the help. They don't call me Murphy for nothing, because if it is gonna happen it is gonna happen to me. I think from now on I need to video record all my flights so I can show people that I am not actually hitting anything when this stuff fails! You shoulda seen it though, she set back down so nice and smooth after the tail fell apart that you almost couldn't tell the tail was gone except for a slight rotation to the left. That is a testament to how smooth and balanced it is.

One of these days it will get to fly more than 2 ft off the ground!
Jan 19, 2007, 12:04 PM
Registered User
Scott_RC-TEK's Avatar
Your pictures speak a thousand words so we don't need them sent back. Maybe send them to Fung . The new V3 tail should solve any potential issues and keep any slop at 0%.

Jan 19, 2007, 12:25 PM
Registered User
I've had some trouble with my tail unit but nothing that caused damage. It would come unscrewed a little and the helicopter would rotate I solved this simply by hand tightening and using the 'Screw Glue'. In my efforts to get things perfectly aligned, I noticed that part AL2020 can slip too closely to the blades, causing the arms to bind. If the part slipped on the bearings, I can see how it could easily have caused a situation where the tail would bind and parts would break. Luckily I never experienced this in flight, but I did while adjusting. The tolerances are exact and just the right angle will allow the AL2020 part to slide with little force. Even with the screw tightened all the way it slips. I guess Loctite is needed here.

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