Monitoring the standby ADI at critical phases of flight
Flight International 3-9 January 2017 described conflicting indications on the captain's and co-pilot's artificial horizon which led to spatial disorientation and fatal crash of a Bombardier CRJ 300 freighter on 8 January 2016.
A defect in the captain's primary attitude indicator caused it to show a rapidly increasing nose up attitude while the aircraft was in level flight at night at 33,000 feet.
Swedish investigators said the apparent increasing pitch on the captains ADI probably led to an "instinctive reaction' to counter the unusual attitude.
Although the aircraft exceeded 500 knots on the descent the CRJ did not break up in the air. Recorder information showed a shift in the elevator towards a nose-down position and the autopilot disengaged automatically. The recorder also revealed the horizontal stabiliser was moved manually using the left hand control column for 19 seconds in the nose-down direction.
The CRJ would have been fitted with a standby ADI as an "umpire" between the two primary ADI's. At the risk of being wise after the event one could argue that a quick comparison between the standby ADI and the two primary ADI's may have prevented the accident; yet the article fails to make this point. I wonder if the investigators had thought about this?
In simulator training it is rare that scenarios are introduced where more or less instant use of the standby ADI is required. While flight on standby flight instruments in the simulator may be tested during an IPC it is usually after the introduction of failures to all generators and where quite complex non-normal checklist actions are called for.
The standby ADI is rarely monitored as a cross check in normal flight on instrument approaches and this can lead to pilot complacency. From personal experience during black night departures from Pacific atolls in Boeing 737's, where one was on instruments from initial rotation, this writer developed the habit of closely monitoring the operation of both the primary ADI and the standby ADI, until safely established in the climb away.
In fact, monitoring the operation of the standby ADI should be part of normal instrument scan. However, with accent placed in many airlines on following primary ADI flight director indications once rotation is commenced and thus instrument scan is reduced to basically the FD needles to the detriment of other flight instruments, it is no wonder that general monitoring of the standby ADI is considered by some as unnecessary. Good airmanship would suggest otherwise.