T-34's Grounded

On Sat, 11 Dec 2004 14:57:45 -0400, "Juan Jimenez"
wrote:

The FAA has just issued an emergency AD that appears to ground _all_ Beech
T-34 aircraft, all models, until further notice, after confirming that the
Texas Air Aces T-34 that went down a few days ago suffered a wing
separation. It only allows a few hours of flight under very strict
restrictions to reposition aircraft to home bases, etc.

See http://www.aero-news.net for more info, I just got the email from the
FAA this morning and posted the news immediately.

Juan
The following was posted on a Beechcraft Email List by George Braly of
GAMI. They've been working to develop a fix for the original problem.


This accident is the second Texas Air Ace crash near Conroe in 13
months.

Conroe crash #1 a year ago was a near perfect application of the rule
of insanity - - as it was a near carbon copy of the 1999 Rydell,
Georgia T-34 crash involving Sky Warriors.

Conroe crash #2 - - this December, is different.

1) The main wing spar (MWS) did have an approved AMOC for the used
Baron Spars, although it may have been technically illegal until
sometime late last spring when the paperwork was approved.

2) In Conroe crash #1 (CC1) the MWS failed in exactly the same
location for the same reasons (substantial fatigue cracking) as the
1999 crash. However, during the investigation, there was some minor
fatigue cracking noted at a rivet hole on the inboard side of the aft
MLG trunion attachment fitting where it attaches to the lower rear
spar. There is evidence that I consider to be compelling that the
first Conroe crash involved g-loading in excess of 9 g's. Yes Nine.
Probably 10 or more.

3) Raytheon had a 2001 AD that provided for eddy current inspection of
this rivet hole found to be a problem in CC1. That RAC AD had,
apparently been complied with - - but - - apparently, missed the
crack in that location on the CC2 crash this week. HOWEVER - - THE
WING DID NOT FAIL THERE SO THAT ISSUE HAD NOTHING TO DO WITH THE CRASH
BUT it has caused the FAA to want to look closer at that inspection
procedure. From our personal experience (we have a $20,000 dollar
eddy current testing machine at our shop) that small hole is
difficult to inspect, as a practical manner.


4) This structure is nearly identical to all Bonanzas and Barons, and
the cracks in this area may be related to landing loads, not flight
loads. We don't know for certain. Again, keep in mind that a Bonanza
at 3650 lbs and 4.4 g is not stressing the wing at levels that are a
lot different than a T-34 at 2900 lbs and 6 g's. But, few people ever
see 3 or 4 g's in their A36, either.

5) We have developed and are testing a structural repair for that
specific area that is relatively simple and relatively inexpensive. I
was doing flight testing last week and recording the strains in that
area, and the repair appears to work well. We are planning on doing
some more testing with some more strain gages, but this should resolve
that for the T-34s and in the future, for all Bonanzas and Barons.
It will probably be a good idea for Bonanza Baron owners to install
the repair, prophylactically at some point.

6) CC2 failed, apparently, just inboard of the lower group of Huck
bolts (the same ones associated with the Bonaza/Baron spar issues) on
the spar carry through section. There may have been some fatigue
there in one of those Huck Bolts. On first glance we should be able
to eddy current inspect in the T34's with a bolt hole inspection.

7) CC2 may have failed at the left rear horizontal stabilizer. If it
did, (we still do not know if it failed primary or secondary to the
wing) we may never know which failed first - - the tail or the wing.
The area of fatigue on the tail is, apparently, an area that has been
subject to a long standing tail inspection AD. If so, the inspection
of this area was inadequate. This surface on the T-34 that revealed
fatigue cracks in CC2 is shared by many straight tail Bonanza type
airframes.

8) None of the approved AMOC's failed to do what they were designed to
do. The bolt hole inspection of the one rivet hole on the aft spar as
described by RAC in the 2001 inspection AD is disappointing, but
until we have further information, it is hard to draw any particular
conclusions from that. Obviously, the FAA wants to take another look
at that, and properly so.

9) in the past I have suggested that commercial air combat type
operations should be required to carry a recording g-meter and to set
standards for exceedences at a threshold well below the 6 g rating of
the airplane and those standards should be part of the operating
certificate for that type of activity. As one participant noted,
they were frequently encountering g-induced loss of vision. Depending
on the person, that normally takes well more than 4 g's. Typically
around 4.5 to 5, in my experience. Thus - - it is clear that the mock
combat operations are imposing a highly accelerated loading spectrum
on the airframes.