Waiex Tail Service Bulletin.. WTF!

[chris]

The report mentioned a Garmin 510 was being analyzed. That should provide ground speed and ground track. I would like to know attitude information at the time of the break up.

I am assuming some larger than usual forces were being applied to the plane when this occured. If it was in straight and level flight that would seem to place a lot more urgency on getting the modification completed...fast.

Jeff Shultz has an image of the accident aircrafts panel on his website. It was equipped with a Dynon EFIS. I cant read the number but its probably a D100 or D60 since another EIS is installed. I'm not familiar with dynons. Is flight information like attitude airspeed and altitude recorded and recoverable from these units if not too damaged?

[fastj22]

At the risk of jumping to a conclusion and leading others to speculation...
I don't think this is a fatigue or design issue.
Obviously, Sonex got a look at the separated tail structure, did some analysis and issued an SB. Paid for by them. Good on them.
I think its a situation they didn't factor into their design. And since it happened, they did an analysis and adjusted their design.
From their own words, "an asyncronous load factor". What that means to me is the tail was subjected to a load that wasn't in the design.
Think bird strike. A big bird. Hitting the tail near the tip and ripping the mount. The tail pulls free, and separates from the aircraft. Aircraft tumbles end over end. Makes sense to me. I ain't jumping to conclusions and the NTSB will have final say. But I bet that's the case. Sonex simply did a new engineering analysis considering a 10lb bird hitting the tip of the tail at 100MPH and found their mounting bracket could use some more beef.
I consider myself pretty fortunate that I chose a Sonex over a Zenith. They kept refusing to accept a design flaw in their wing until several people died and the FAA effectively grounded the fleet.

[142YX]

The thing that really stands out to me with the SB is the upgrade to 6 NAS bolts from the original 4 AN bolts (in addition to the 1/4" plate). Doesn't seem to me like they are just bolting on some more margin for grandma and adding a psychological safety factor on top of everything.. but more it gives me the impression that something was seriously overlooked in the original load case. There would be no reason to upgrade to the NAS bolts otherwise.

[Andy Walker]

The thing that really stands out to me with the SB is the upgrade to 6 NAS bolts from the original 4 AN bolts (in addition to the 1/4" plate). Doesn't seem to me like they are just bolting on some more margin for grandma and adding a psychological safety factor on top of everything.. but more it gives me the impression that something was seriously overlooked in the original load case. There would be no reason to upgrade to the NAS bolts otherwise.

Interesting, I didn't realize more/stronger bolts were added. Also note that big honking doubler bar at the base of the mount bracket. That is some *serious* metal added, and not in a place I would expect failure. :?:

[142YX]

At the risk of jumping to a conclusion and leading others to speculation...
I don't think this is a fatigue or design issue.
Obviously, Sonex got a look at the separated tail structure, did some analysis and issued an SB. Paid for by them. Good on them.
I think its a situation they didn't factor into their design. And since it happened, they did an analysis and adjusted their design.
From their own words, "an asyncronous load factor". What that means to me is the tail was subjected to a load that wasn't in the design.
Think bird strike. A big bird. Hitting the tail near the tip and ripping the mount. The tail pulls free, and separates from the aircraft. Aircraft tumbles end over end. Makes sense to me. I ain't jumping to conclusions and the NTSB will have final say. But I bet that's the case. Sonex simply did a new engineering analysis considering a 10lb bird hitting the tip of the tail at 100MPH and found their mounting bracket could use some more beef.
I consider myself pretty fortunate that I chose a Sonex over a Zenith. They kept refusing to accept a design flaw in their wing until several people died and the FAA effectively grounded the fleet.

Asynchronousness does not need to imply a random event like a bird strike.. it simply means that the load is not uniformly distributed over both surfaces. From the letter that they released on the yahoo group (the one that they are sending with the upgrade kit), Sonex was beating around the bush implying full rudder deflection + pitch input to the tune of the airframe's design rating of 6 g's resulted in a load case that they did not originally consider in the design.

I agree that i am glad to be building an airplane from a company with this level of customer support. Then again, rumors (even ones that are not necessarily true) spread like wildfire, and i think that it is in their best interest to beat this issue into submission before the layman starts telling his buddy not to build a Waiex because their tails fall off. (just think of the bad reputation that bonanza's received)

[fastj22]

Given the altitude, flight phase and distance from the airport that this even occurred, I doubt the pilot was subjecting the aircraft to full deflection of the control surfaces in an asycronous way. Something else entered into the equation.

[142YX]

Interesting, I didn't realize more/stronger bolts were added. Also note that big honking doubler bar at the base of the mount bracket. That is some *serious* metal added, and not in a place I would expect failure. :?:

AN bolts are in the 125 ksi range, where NAS bolts are in the 160 ~ 180 ksi range. They are doubling their shear loading allowable between the aft "y-spars" (the load path that is communicated between the plates).

Also, the addition of the front 3/4" blocks is increasing the bearing surface through the front spar.

[fastj22]

Another thing to keep in mind is that Sonex did not issue a warning for any mandatory inspection of the mounting brackets for signs of fatigue. Had this been a fatigue issue, that would have been their first line of defense and responsibility to the fleet.

[chris]

...i think that it is in their best interest to beat this issue into submission before the layman starts telling his buddy not to build a Waiex because their tails fall off. (just think of the bad reputation that bonanza's received)

I think that doing the testing, finding a solution, and getting out a SB just 24 days after the accident is a pretty good start on doing that.

[fastj22]

I think it demonstrates we chose the right company to build with.