Accident Overview
During takeoff to the east over the ocean, the twin-engine jet climbed to about 2,200 ft and 200 knots groundspeed. The copilot reported an "engine failure" and requested radar vectors back to the departure airport. The controller assigned an altitude and heading, but the copilot replied "not possible" and requested a 180-degree turn. The controller approved, but the airplane continued a gradual left turn to the north while slowing and descending.
Cockpit Communications and Actions
The copilot declared a "mayday" and again requested vectors. Over three minutes, the copilot acknowledged multiple instructions to turn left to the southwest, yet the airplane maintained its slow left turn and descent northbound. It slowed to 140 knots and descended to 900 ft while flying parallel to the shoreline, away from the airport. Eventually, the airplane tracked toward the airport but continued descending, impacting the ocean about 1 mile offshore.
Cockpit Voice Recorder Findings
CVR conversations revealed that no checklists were called, offered, or used during normal operations or after the emergency. After the "engine failure" declaration, the pilot asked the copilot for unspecified "help" because he did not "know what's going on" and could not identify the emergency or direct the copilot. The copilot did not identify or verify a specific emergency and provided no guidance or assistance.
Wreckage Examination
Recovered wreckage showed damage to the left engine's thrust reverser components, including separation of the lower blocker door. The stretched filament of the left engine's thrust reverser "UNLOCK" status light indicated illumination at impact, demonstrating that the thrust reverser became unlocked and deployed (at least partially, possibly fully) in flight. Impact damage precluded testing of electrical, pneumatic, and mechanical continuity, so the reason for deployment could not be determined. No previous instances of inflight thrust reverser deployment on this make and model were documented.
Emergency Procedures and Data
The airplane's flight manual supplement contained procedures for inadvertent thrust reverser deployment during takeoff. For deployments above V1, the procedure included maintaining control, placing the rocker switch in "EMER STOW," shutting down the engine, and performing a single-engine landing. Data from the left engine's digital electronic engine control (DEEC) showed that the rocker switch was not placed in "EMER STOW" and the engine was not shut down. DEEC data indicated a reduction in N1 about 100 seconds after takeoff, followed by a rise about 35 seconds later, consistent with deployment and subsequent separation of the lower blocker door. Full engine power was applied throughout the flight.
Crew Performance and Qualifications
Neither crewmember recognized the problem as an inflight thrust reverser deployment. Certification flight test data indicated the airplane would have been controllable in its configuration. If the crew had applied the "engine failure" procedure (the perceived problem), the airplane would have been more easily controlled and could have landed successfully. The airplane required two fully-qualified flight crewmembers; however, the copilot was not qualified to act as second-in-command and provided no meaningful assistance. The pilot's performance was highly deficient: he did not adhere to best practices in executing checklists, was unprepared for the emergency, did not refer to appropriate procedures, and did not direct the copilot to checklists.