View Full Version : Fail-operational, 737NG

8th Jul 2011, 08:53
Hello chaps

I have a question specifically regarding the 737 fail-operational status.

Since we have only two autopilots, what makes the system triple redundant and hence fail-operational?


8th Jul 2011, 10:53

8th Jul 2011, 11:12
Extract from CS-AWO:

(4) Fail-operational Automatic Landing System: An automatic landing system is fail-operational if, in the event of a failure, the approach, flare and landing can be completed by the remaining part of the automatic system. In the event of a failure, the automatic landing system will operate as a fail-passive system.

The following are typical arrangements:

(i) Two monitored automatic pilots, one remaining operative after a failure.
(ii) Three automatic pilots, two remaining operative (to permit comparison and provide necessary failure detection and protection) after a failure.

Apparently you can receive fail-operational status with two monitored autopilots. But what a monitored autopilot is, I'am clueless :confused: