Originally Posted by
DozyWannabe
Since when has a single manufacturer's methods been 'usual'? As I understand it, there are differences in the load limiting method used by every manufacturer.
Not really. Usual method FOR Boeing (either variable ratio or force limiting). Only airbus almost exclusivley use variable stop.
Why should they? It's not like everything Boeing makes becomes a de facto standard!
Another thing worth bearing in mind is that the A300 was specified in the late 1960s, around about the same time as Boeing were developing the first generation of aircraft that would use the load-limiting method you refer to. Airbus may not even have been aware of the development of the variable-feedback method.
Again - Not really! I think Airbus were quite well aware of the variable ratio system -
they used it on the A300-600's predeccesor! And then decided to CHANGE to a variable stop design. But then you'd find that in the actual report.
As for why should they? Maybe to avoid the ridiculous situation of having a
10lbs force difference and pedal displacment of
1.2 inches between breakout force and rudder full to the stop at 260 kts!! As opposed to a difference of
43lbs and pedal displacment of
4 inches at 136kts.
Apparently some "other people" have at least a
similar opinion :
"The Safety Board concludes that, because of its high sensitivity (that is, light pedal forces and small pedal displacements), the Airbus A300-600 rudder control system is susceptible to potentially hazardous rudder pedal inputs at higher airspeeds."
I just hate the fact that I think the pilot was unfairly blamed.
Well....To quote the Probable Cause from the NTSB report:
"......created by the first officer’s unnecessary and excessive rudder pedal inputs. "
Seems a lot like blame to me.
I do not wish to give a blanket defence to the PF in this case - or to comment on how poor or otherwise his airmanship was. My original point being that I personally believe the evidence on that one issue is inconclusive - a point which even the official report moots. However, for all the critical comments qouted about a previous wake encounter - there are just as many quotes that could be made from former colleagues describing him as "excellent", "well above the norm" and that he flew "smoothly and accurately".
As for anyone who still insists that the aircraft is fit to fly (despite the NTSB recommending changes) - and that some or more of the blame should have rested with the PF - I can only draw your attention to the following 2 crucial factors:
1) Bearing in mind the definition of Limit Load - the A300-600 and A310 (with almost identical systems and characteristics) have had
SEVEN exceedances of Limit load, some of which actually exceeded
Ultimate Load, on the fin - not all of which involved pilot rudder inputs. To quote
Mr. Henry Offerman Aerospace engineer, FAA regarding Limit loads:"limit load is the maximum load expected in service" and "it is fairly safe to say that the data that was used to develop that envelope would yield a once in a lifetime event", and regarding Ultimate Load;"An aircraft is not expected to experience ultimate load in service."
The A300 B2/B4(variable ratio),A320 and A330 have had none(reported). This is also true for Boeing(again reported).
2) During the course of the investigation, simulator testing showed that "most" of the 6 testees used some rudder input in combination with aileron when using their own "prefered method" of recovery. When this is read with the following statement regarding ground testing, the conclusion should be obvious!:
"Tests were also conducted in which the subjects were instructed to move the control wheel and rudder pedal to 50 percent of their available range. The tests showed that the pedal force applied during the 50-percent condition resulted in full rudder travel, even though that force was one-half of the force applied at the 100-percent condition. The tests also showed that the control wheel force applied during the 50-percent condition resulted in reduced aileron motion."