Originally Posted by
FlightDetent
Think redundancy.
- If "B" is the only one remaining, it remains connected to both elevators! So pitch control is possible with good authority. No need for THS.
- If "Y" or "G" would be the last one you have, either of them will give you THS and one side of the elevator.
These conditions aren’t valid in mechanical backup. In mechanical backup you have only rudder and THS. With blue system you can’t control THS in mechanical backup situation. You have to fly aircraft with only rudder. I am just wondering why Airbus designed A320 that way. Rudder is supplied by three hydraulic systems but not THS. Why?
Maybe they think having mechanical backup with blue system has a very very low probability so they designed that way or they thought THS supplied by three systems could create another problems like complexity but there is a probability having mechanical backup with only blue system. Never say never
As a person getting A320 type rating, i want to know what engineering idea is behind that design.