ATR CLUTCH
The ADSB info shows a modest performance level of the aircraft from quite early on after takeoff. The loss of control is abrupt, as it almost always is, but the lead up to it, if due to an asymmetry in thrust is not abrupt, it has been there for a considerable time. If so, there will be some long hard looks at standards.
SITUATIONAL AWARENESS
China Eastern was an abrupt event, the problem arose and caused a quick follow on to loss of control. The crew are startled and also not necessariy aware of the problem, an SA Level 1 type failure.
CI006 engine failure in cruise resulted in a decay of performance and while the crew were deliberating, the aircraft, well above it's 3 engine ceiling, lost speed, and the APLT lateral control diminished to the point the plane rolled over. an SA Level 3 failure of the engine loss, and an SA Level 1 failure related to the APLT aileron authority and airspeed decay.
Endsley (& Jones) came up with the taxonomies of Situational Awareness (SA) failures as:
- Level 1: failure to correctly perceive the information
- Level 2: failure to comprehend the situation
- Level 3: failure to project the situation into the future
Level 1 failures can be cured in time, with warning systems and good training.
Level 2 failures need well-understood warning systems (Helios type problem) and good crew training
Level 3 failures need soul searching by the selection and training and monitoring systems. They are fundamental to the humans involved and are hard to defend against, and are latent failures within our systems at all times.
Endsley evaluated ASRS reports and found that:
- 76.3% were Level 1 SA errors,
- 20.3% were Level 2, and
- 3.4% were Level 3
For one major airline, I evaluated their accident and incident database and found that 97% of all reports involved SA failures of one or more of the types. The only events that did not involve an SA failure of some sort were birdstrikes, and some mechanical failures that were correctly presented, perceived and responded to. On the hull loss cases, which there were far too many, involved almost always multiple forms of SA failure. Possibly the saddest case, an SA Level 3 failure, had 34 occasions in the last 30 minutes of the CVR where the crew showed they recognized the problem, but didn't recognize the impact on their flight path management and parked a billboard on the top of a hill, killing a couple of hundred people, the crew rather surprised when they saw the goats in the clouds. When a robust, reliable countermeasure for SA Level 3 failures arises, aviation will be a lot safer.
APLT CHANNELS
Apart from the curiosity of the A340-600, the majority if not all of the APLT fitted act as 2 axis autopilots, for flight path management. Only yaw damping is usually functioning by a rudder channel, or a torsion/load relief mode as in the B74 rudder. When configured to autoland, a rudder channel may be active for runway alignment manoeuver and rollout control, and a system such as the B777 and B787 Thrust Asymmetry Computer, TAC, may function. On most the yaw damper has a limited turn coordination function as well, however essentially APLTs function in 2 axis for operations, drivers feet still have a use.