Paul wrote.
It is real tough to detect delimitation visually. Unless they used
ultrasonic
or even the coin tap test in the structural parts  of the vertical tail they
would
not find the damage. A quick way to test things like that is put an
accelerometer
on the tip of the tail and hit the tail someplace else with a hammer and
record the resonant frequency. To my knowledge they are not doing that on
check "C's".

Mark, what kind of structural inspections are you doing over there?

Paul Lamar

Mark Wrathall wrote:
The Manufacturer issues an MPD (maintenance planning doc) with each
inspection and its recommended interval. We add our requirements and put
together a maintenance program  to group these individual tasks into logical
checks and get it approved by the authority. The MPD is a living doc and
will be modified to include the airlines check findings. Almost all airlines
report all structural findings back to the manufacturer.

We run a monthly A-Check and annual C-check as the basic format. In our plan
the uneven C-Checks are pretty small. Every fourth or sixth C-Check -
depending on model, is a real structures monster . However, with no previous
event driven AD mandating a specific NDT (non-destructive test) ispection,
it is all general visual and detail visual inspections, plus corrosion

inspections.

I checked the 767 MPD, and it has general visuals inside the vertical stab
every C-check. Detailed visual in the attach fittings every C3, and a
retorque and corrosion inspection every C6. There are about 30 diffferent
tasks in the vertical stab. The NDT cards (none involve the vertical stab)
start at 25000 cycles, which a large number at 50000 cycles. To put that

in perspective,

50000 cycles is the design life from Boeing, so if you every reached that

you need

to NDT all critical primary structure if you want to extend the life. Very
few large airliners (Japanese domestic) and maybe 50% of medium sized
airliners will ever reach the design cyclic life.

The A300 which went in was an 88 build, which is pretty late in the
production. I wonder if the carbon vertical stab was in the original 1972
design, or if that got developed later.

Mark,

 Is the A300 rudder actuator capable of a structural disconnect from the rudder
 (i.e. not physically separate multiple actuators)?

Am I correct in guessing that the A300 rudder has no mass balance and is only
flutter protected by the actuator?

THANKS.

Bill Freeman
Long EZ builder & pilot
BSME, MSME
EAA Technical Counselor

 
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