2007-12-02 11:15:57 · 6 answers · asked by Anonymous in Cars & Transportation ➔ Aircraft
Redundancy is a good thing. Many aircraft have quadruple redundancy built into their many systems.
2007-12-02 11:21:12 · answer #1 · answered by Milo 3 · 0⤊ 0⤋
Because we have seen so very many things go wrong before. Same reason the B747 has 4 independant hydraulic systems and that doesn't seem excessive to good engineers.
Basically with two systems, one of which has failed, you only know that the two systems disagree. With three systems two will agree and we hope two haven't failed at the same time.
There are three artificial horizons on some commercial aircraft (can't guarantee it's on all), the pilot and co-pilot can each select theirs or the other input, but there's a third horizon to reference when you think one has gone wrong and need to know which one can be trusted.
Airbus were so 'paranoid' about single mode failures that the triple redundant flight control system runs on hardware designed by two separate teams and runs software developed by two separate teams. That way they hope the same assumption won't occur in most of the twelve possible combinations. But that was back in the 80s and who knows what has changed since then?
2007-12-02 16:01:29 · answer #2 · answered by Chris H 6 · 0⤊ 0⤋
It's actually for the auto land, where the plane lands itself. The three autopilots cross check each other. If one is giving erroneous reading it will be able to figure which one it is. If they only had two, it wouldn't know which one was operating correctly and if it only had one it would assume it was working correctly.
A good thing to have, especially when the plane is landing itself.
The plane can be dispatched with only one autopilot but it won't be able to land in zero or near zero visibility conditions
2007-12-02 16:20:31 · answer #3 · answered by stolsai 5 · 2⤊ 0⤋
You never place trust in a single component without redundancy and with autopilots, two are required in order that they be able to 'talk' to each other and 'compare'.
With triple redundancy, should a single autopilot fail...two still remain allowing for unrestricted usage of the system.
This SOP may vary from company to company or aircraft to aircraft....but with our company...thats why.
2007-12-02 11:38:54 · answer #4 · answered by helipilot212 3 · 2⤊ 0⤋
redundancy.....sure would suck to be on an autopilot coupled approach in low vis and have that one computer go out wouldn't it? and there have been instances, although rare, where the backup went out also.....having 3 makes sure that you've always got a backup for the backup.....
2007-12-02 11:31:56 · answer #5 · answered by #1 bossman 5 · 0⤊ 0⤋
Iike others have said, redundancy is a good thing...
2007-12-02 14:32:47 · answer #6 · answered by ALOPILOT 5 · 1⤊ 1⤋