This fin exceeded regulatory requirements by very healthy margin
… Airbus composite fins and rudders in general … or this particular (repaired) fin?
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… in any event … are the ‘regulatory/certification requirements’ reasonable in that case??
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… surely one must consider ‘possible’ rudder induced side load/s on the fin and attach points when paired with side load from inertial yaw forces + the H-M interface of 1.2 inches of pedal travel at 250kt??
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… in turbulent wake, is 1.2 inches really giving pilots a fighting chance of achieving fine, targeted rudder effect ..which in turn might help avoid PIO’s??
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.. common sense suggests the formular in a crude sense is:-
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- provide enough surface and structural strength to enable management of required/possible flight envelope (then add margins)-
- limit control input parameters to protect the structure whilst providing necessary control authority to the pilots for 'unusual' encounters!
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This should apply to all combinations of composite or alloy structures irrespective of control method (hydro-mechanical and/or fly-by-wire)
Perhaps metal would bend before breaking,
.. anyone aware of a ‘wake fin off’ accident with a wing slung alloy machine??
but that would be hardly helpful.
.. what .. damaging a metal fin/rudder (whilst retaining it on the airframe) would give a crew less of more chance of a safe return that the whole thing breaking off?? …
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.. besides, if the initial aileron movement is indicative of the strength of the wake, the vortex may have clobbered the side of the fin/rudder in any number of directions over the elapsed time of the upset encounter ... is it therefore reasonable to expect pilots to provide a physical foot input of 'less' than 1.2inches in either direction whilst counteracting what they may well feel as substancial yawing (perhaps in more than one direction in quick sucession) effects!?
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.. it is possible that if the aircraft encountered the wake climbing from beneth, the fin would be affected first and from one side (as a result of the rotational vortex stream), then if the aircraft was climbing at a greater rate than the aircraft ahead causing the wake, it would not take long for the fin to receive reverse side force from the upper area of the rotational horizontal wake vortex!
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.. either way (weakened or not) .. and irrespective of the training and informed best intentions of pilots .. the question remains in my mind..
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.. could any A300-600 airframe/pilot/turbulence combination result in a similar outcome ..???
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… 1.2inches …. couple of rudder reversals at slow-ish' speed??
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… hands up how many folks at the pointy end of these things tend to want to keep their feet up on the glare shield???
