Originally Posted by
vapilot2004
I read what was written, and I still say it was disingenuous. As it relates to backdriven controls, the PFC off switch is there because Boeing required it - not the FAA nor EASA.
Sure - and I don't think I said or implied otherwise. What I was getting at was that the reason Boeing required it was as a result of the force-feedback based design.
The FAR 25/EASA type certificate limitations of what you refer to as "force-feedback" on the 777 are satisfied through the use of slip clutches in the case of AFDS back drive actuators going 'rogue' due to computer/electronic malfunction. (no relation to the FBW PFCs).
As I've admitted to in the past, I'm not as
au fait with the T7 architecture as I am with the Airbus system. However....
During a fallback to DIRECT MODE (your "big red button") the feel units are still in operation, but the airspeed-commanded variable resistance is replaced by a flap position based command.
Right - in essence it's bypassing the more complex computerised system in favour of a simpler setup.
All of the feel units and backdrives on the 777 can be overridden by control inputs, albeit, at slightly higher than normal command pressures. Should one set of backdrives or a feel unit jams, there is the breakout mechanism allowing one guy to fly the aircraft unimpeded.
Sure, and I appreciate the information - much of which I didn't have before.
I still think that we're talking at cross-purposes though. I wasn't saying anything about regulatory requirements versus Boeing's inputs, I was simply saying that by introducing a digital computer into the feel system it was a necessity to provide a bypass at the time purely on the basis of sensible engineering principles, and that by making their feel system passive, Airbus didn't have that requirement.
Originally Posted by
vapilot2004
I understand M. Ziegler was a key figure in the development of the Airbus FBW system.
Your understanding is a little off-base. Bernard Ziegler was the nominal engineering head of the A320 project, but he did not have a significant degree of technical input. The passive sidestick system originated from the French/British Concorde "minimanche" project, and I am very reliably informed that M. Ziegler had nothing whatsoever to do with it.