I am going to pretend that I didn't just read that you unlocked some CBs without authorisation and then flew the aircraft.
edit, Oh just noticed you are an LAME, not a pilot.
Originally Posted by
EXDAC
Let's say the left switch jams up (AND). When the pilot releases the AND input the right switch will return to center and trim will stop. The other switch did something - It stopped the trim.
Pilot doesn't notice the left switch is stuck and provides a second AND input. Trim responds as commanded. Again the other switch did something. It allowed the required trim change.
Then pilot need ANU trim and tries to move both switches down. He now notices that the left switch is in the wrong place and can't be moved and uses alternate trim. In this case the other switch did not do anything.
All the types I have worked on had two trim switches. I don't know the reason for changing to a single switch.
my bold
My thinking isn't that one jams and cannot be moved.
It is that one of them is acting unreliably and not returning to center. In the case of separate toggles this is noted immediately and can be felt by the pilot. With a single toggle the failure of one switch is masked by the ability of the other to return them both to center via the shared toggle. Rather than giving a warning that one of of the switches is on the road to failure, a single toggle masks that.
No, because the aircraft will warn of a pitch trim problem if one of the switches underneath the rocker fails either mechanically or electrically.
Originally Posted by
Vessbot
The particular advantage has been given multiple times in this thread already: there is no trim runaway with a single jam. And the aviation industry seems to agree with the advantage outweighing the disadvantages, being that most airplanes have this design.
Well, I guess that all the Airbus designers and all the Airbus test pilots in Toulouse are wrong then !
Odd that they would make such a mistake - one that Pprune was able to spot within minutes - because their A320 family is better than the conventional manual pitch trim system.
(yes, I am type-rated on both).