Originally Posted by
Stuka Child
That is simply not true. When is the last time you've watched them?
I've watched them recently, and Warren Vandenburgh repeatedly urges caution when using the rudder because of the sheer size and force of it. Yeah he doesn't say "you might rip the fin off", but that wasn't known at that point - that you might cause the vertical stabilizer to fail even at relatively low speeds.
But there are multiple warnings to be gentle with the rudder in those videos, and certainly no suggestion that it's ok to repeatedly swing it from one side to the other.
The A300-605R rudder limiter had (has) a fundamental conceptual flaw in the design. This is not just semantics. On Boeing aircraft, protection of the structure from rudder inputs at high speeds is achieved by either de-powering the system operating pressure, or by altering the ratio of input to output. For the A300, a limiter to the rudder throw was provided mechanically. The alteration of the stops reduces the ultimate force that can be obtained from the rudder, which is the intent of the system.
but...
In a Boeing design, with a rudder ratio changer, the rudder pedals would move the same distance, however the rudder itself would move through a smaller arc. e.g., a 4" rudder pedal movement at low speed may give 100% throw of the rudder, but at high speed, the same rudder pedal deflection would give a partial throw, say 30% rudder deflection. With a rudder limiter design, for the same 4" of pedal movement at low speed, which gives 100% throw, at high speed, the 30% (for arguments sake) deflection is achieved with 1 1/2" of rudder pedal deflection. The force required to move the pedals 1 1/2" in the A300 case is the same for low speed to high speed. The sensitivity of the system has increased by 300%.. In the Boeing case, of ratio, the force to move the pedal 4" is the same at low or high speed, but the deflection is less, so the sensitivity is reduced, by 60% roughly. With the Boeing designs that reduce rudder hydraulic pressure at high speed, the throw is reduced by the high pedal force, but the pedal movement is reduced as well, so the load is protected, and the sensitivity remains similar in both high speed and low speed cases.
The A300 system worked well enough, and was simple, but a pilot doing a doublet would find that the sensitivity was much higher than would have been anticipated, so over control is a likely outcome.
The second issue with the A300 design that was of concern was that the yoke secondary structure was designed in such a manner that if a primary structure failure occurred, the primary failure would act with a lever arm on the yoke that assured secondary structure failure would occur, which it did.