ORIGINAL: Sandor
ORIGINAL: GrayUK
Gents
I had the opportunity to examine the tail plane after the incident
I enclose photos showing my concern on this issue.
At the point of maximum load (where the tail plane leaves the support of the fuselage) the spar is notched to fit over the rib.
This left aprx. 6mm, 1/4" of spar to carry the load.
The remainder of the spar is butt jointed to the rib but unfortunately no glue appeared to be present on the butt face.
2 fillets of glue had been run down the sides but these were not very substantial.
in my opinion the spar should continue un cut with the rib parts butt jointed to the spar.
These appear to have failed which left the 6mm of balsa spar in free compression, You can see this on the photo.
This puts the top skin in compression and the bottom skin in tension.
The top skin has compressed and the bottom skin torn.......the tail plane failed.
You can see how the top skin is rippled and bent in the picture where as the lower skin is cleanly torn.
The most likely source of the start of the tear is the servo arm cut out in the lower skin.
I did not see any scrape marks on the tail plane halves indicating they had touched the runway on the one and only previous flight.
this represents my opinion only.
I am sure Comp ARF will take all necessary action to correct any safetey issues they feel exist.
but why both sides?
seems like a unlucky event then?
seen many things fails , and flutter can do a lot of damage.
even if one would not be glued correctly , both at the same time?
As much as I dislike Carf and their business practices, and oftimes shabby construction, and as much as I dislike Sandor
, the root cause is most LIKELY(not definitely) flutter. While I find the tailplane spar pictures to be pretty frightening, it's only possible, and not probable, that a stronger spar would have survived a flutter issue.
KEEP IN MIND THIS IS ONLY SPECULATION...before anybody jumps down my throat, I do not KNOW why this tailplane failed, this is pure speculation.
Did anybody hear the classic "brrrraaap!" of flutter before the plane went in?