Vaughn wrote:
On 1/26/2013 8:18 AM, Keith W wrote:
Bottom line is that the pilot overstressed the airframe as
his use of alternate full rudder inputs resulted in large
angle of sideslip which tore off the stabilizer. The loads
imposed by the sideslip were more than double the design
limits.

None of which excuses the design. Pilots are taught from day one that
full deflection of flight controls is generally permissible below a
certain magic "maneuvering speed" without causing harm to the
airframe. Given that the accident flight was in the climb phase,
that plane was almost certainly below that speed.


Trouble it was at that speed which at the altitude in
question was 250 knots. When the stabilizer failed the
speed was at 251 knots and the pilot had applied full power

So this turned out to be a flight limitation that the pilots hadn't
been told about and was nowhere in the flight manual.

True to an extent but the issue was not in an Airbus flight manual
but in an FAA document ( Title 14 CFR 25.1583, "Operating Limitations")

This stated that

Quote
that full application of rudder and aileron controls, as
well as maneuvers that involve angles of attack near
the stall, should be confined to speeds below this value."
Quote

This was found to be ambiguous in that it implied that multiple
full deflection inputs were safe at or below the safety speed.
This the NTSB and FAA found was not true for most large
transport aircraft and the FAA document was amended to
inform operators that operating at or below maneuvering speed
does NOT provide structural protection against multiple full control
inputs in one axis or full control inputs in more than one axis at the
same time

After the accident Boeing issued the following clarification to its users.

"Boeing aircraft are not designed to a requirement of full authority
rudder reversals from an "over yaw" condition. Sequential full
or nearly full authority rudder reversals may not be within the
structural design limits of the aircraft, even if the airspeed is
below the design manoeuvring speed. "


The AA flight training centre was using faulty
simulator training that encouraged the use multiple
cyclic full rudder inputs to control wake roll
problems and had fostered the mistaken belief that
the rudder limiter would prevent any bad results from
excessive inputs.

The extent of the forces caused by the rudder inputs may be
gauged from the fact that the flight data recorder showed
they caused alternate lateral accelerations of between
0.3 and 0.4 G

This DESIGN
DEFECT was "fixed" by changing the flight manual to add new flight
limitations and retraining pilots. To be fair, I know of no other
similar accidents since then.

Going back to my central point, the A300 easily survived that negative
publicity, as will the 787.

I am sure that it will, battery and charging system problems
should be easy to resolve.

Keith