Lessons Learned

Technical Related Lessons

If manual override of an automatic flight control system becomes necessary, it should be accompanied by an immediate disconnection of the system. (Threat Category: Incorrect Piloting Technique)

  • Prior to landing, the autothrottles were engaged, and the AFDS was in VNAV mode, though the autopilot was disconnected. VNAV is not intended as an approach mode, and its associated automatic functions (such as autopilot and auto-throttles) are required to be disengaged at the designated missed approach point in order to proceed with the landing. In this case, when reaching the missed approach point and since VNAV was still an engaged mode, the designed airplane response was to initiate a go-around. When the throttles automatically advanced to go-around thrust, the pilot flying manually restrained the throttles and held them at the idle position. Just before touchdown one of the throttles escaped his grip, and once again advanced to go-around thrust. Further, advancement of the number 1 thrust lever inhibited the activation of the ground spoilers and automatic brakes.

Common Theme Related Lessons

Automatic flight control systems which, when operating as designed can control, or take over control of the airplane, should be fully described by the manufacturer, and fully trained by the operator. (Common Theme: Organizational Lapses)

  • VNAV was not intended to be engaged all the way to touchdown. The design was such that once reaching a predetermined altitude on any non-precision approach, the automatic features, and VNAV, would be disengaged, and the airplane would be landed manually. According to the investigators, Boeing had not adequately described the various features of VNAV to airline customers, and as a result, airlines had not provided training to flight crews regarding many aspects of some automated functions. The crew of Air France Flight 072 was not aware that VNAV would initiate a go-around at the missed approach point. When the go-around was automatically initiated, they deviated from normal procedures and manually overrode the system in order to complete the landing. The investigation concluded that if the crew had been aware of the constraints associated with VNAV usage, they would have disengaged the system at an appropriate altitude and successfully completed the landing manually.

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