What happened
On January 5, 2010, a Gates Learjet Corp. 35A, registration N720RA, was performing a positioning flight from Oakland County International Airport to Chicago Executive Airport (PWK) to pick up cargo. During the descent, the flight crew encountered moderate rime ice. After transitioning to visual flight rules, the crew canceled their instrument flight rules clearance and began a right, circling approach for runway 34.
As the aircraft was maneuvering on the base leg of the traffic pattern, the captain requested full flaps. During this period, the crew engaged in several discussions regarding airspeed, fuel balance, and the operation of the spoileron system. The first officer noted that the spoileron system did not appear to be functioning correctly. Shortly after the crew attempted to add full power, the aircraft's bank angle increased significantly, and the airplane impacted the water and terrain near the west bank of the Des Plaines River. Both the captain and the first officer sustained 2 fatal injuries.
The investigation
Investigators examined the wreckage and recovered the cockpit voice recorder (CVR). The aircraft was destroyed upon impact. Examination of the flight control components, including the flap and spoiler actuators, revealed no mechanical anomalies that would substantiate a failure in the a/c aileron augmentation system. While the first officer expressed concern regarding the spoilerons, no mechanical cause for a loss of roll control was identified.
Engine data from the digital electronic engine controls (DEEC) showed that both engines were operating and responding to power lever inputs until approximately four seconds before impact. The engines' power levers were moved to settings greater than takeoff just before the crash. The CVR transcript indicated that the crew was aware of icing conditions, and the cockpit environment was noted to be non-sterile during the approach due to discussions regarding airspeed and fuel.
Findings
- The flight crew was focused on identifying the cause of handling difficulties and fuel balance rather than monitoring the aircraft's decaying energy state.
- The crew did not detect the critical loss of airspeed and altitude before the aircraft reached a point of no recovery.
- The cockpit environment was not sterile during the approach, as the crew engaged in non-essential discussions.