Bill wrote>

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

Mark wrote>

I haven't worked on Airbus ( we just have Boeing and Canadair) but

Austrian

flies an all Airbus fleet. I went down to the hangar to confirm they

do the

actuation the same way Boeing does it. The three actuators (as well as I
could tell from the hydraulic fluid smears - there were no AUA mechanics
around to talk to) appear completely separate as they are on the Boeing
widebodies.

Your are correct that the 3000psi hydraulic actuators assume all damping
function, there is no mass or aerodynamic balancing.

Strangely enough the 777 has an antibalance tab to increase rudder
effectiveness. A strange addition to a fly by wire design.

The FAA released emergency AD 2001-23-51 to order  up the inspection

of all

A300/310 tails.If this plane was sabotaged/shot down/bombed, you'd think
they would know that already.

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/WebNewEme

rgencyAD/3D35BCB1CF80903586256B06005EA641?OpenDocument

Thanks a lot Mark,

Been trying to puzzle this one out and so far rudder flutter seemed

likely, but

with three physically separate actuators, that seems harder to do.  Going on
your knowledge of the Boeings with separate actuators what will the
actuators do if they lose hydraulic pressure (severed line, drain out fluid)?
Free the rudder to flutter or do they lock up mechanically some way?

If they free up the rudder (basically like a hydraulic cylinder drained of
fluid) the rudder could still flutter, but would have had to had all three
systems severed.

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

AL announced today that they completed the vertical fin inspections but the

question

is; how did they inspect them? I would not trust even a ultrasonic test.
I suspect the only sure way would be coupons cut from the tail that
failed and subject them to  stiffness and tensile strength destructive test.

Paul Lamar

I absolutely agree on the test coupons.  I still want to see the rudder
hinges and
actuators & linkages plus the inside of the actuators.  Flutter will leave
its marks.
The failures in the tabs could be due to overload from flutter of the
rudder, altho
triple actuators makes this harder to fathom.  A DC10 had a triple engine
failure
due to all three oil drain plugs being the wrong part number, which could have
happened here in some similar fashion with the same erroneous maintenance
on all three actuators or links.

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

 
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