Bombardier Learjet Corp. 35A N544LM incident near Anchorage, Alaska

Probable cause

The flightcrew's loss of visual reference to the runway after encountering severe in-flight icing conditions, which resulted in a loss of control while landing and exceedence of the capabilities of the airplane's windscreen anti-ice systems. Contributing to this incident was the failure of the approach controller to relay a pilot report of severe icing conditions near the route of flight to the incident flight crew.

NTSB analysis

As the medical transport flight descended below the cloud cover during dark night, instrument meteorological conditions while on approach, the flight crew discovered that the first officer's windscreen was entirely covered with ice and that she would not be able to continue the approach. Although the captain's windscreen was partially covered with ice, he could still see the runway, so he took control of the airplane and continued the approach. The flight crew then confirmed that the windscreen heating and alcohol anti-ice systems were on. As the airplane passed over the runway threshold, the captain's windscreen abruptly iced over, and he had no forward visibility as the airplane's main landing gear wheels touched down. Unable to see the runway ahead and with limited visibility to each side, the flight crew attempted to activate the engine thrust reversers to slow the landing roll, but the airplane subsequently veered to the right of the runway centerline, and the right wing collided with a snow berm. The pilots reported no preincident mechanical malfunctions or failures that would have precluded normal operation.

About 15 minutes before the incident, the approach controller at an airport about 7 miles northeast of the incident airport advised the destination airport's north radar position controller that the pilot of another airplane had reported that he was "going around" due to severe icing on the airplane's canopy. No record was found indicating that this pilot report (PIREP) was relayed to the incident flight crew or other aircraft operating near the incident airport. Both airports are under the control of the same approach control facility. The meteorological conditions at the time of the accident were conducive to a very light freezing or frozen precipitation environment very close to or at the surface. Therefore, it is likely that the airplane encountered significant in-flight icing conditions during the approach and landing that exceeded the capabilities of the airplane's anti-ice systems. In addition, if the pilots had been made aware of the severe icing PIREP from the nearby airport, they likely would have had other options available for landing. The Federal Aviation Administration has indicated that it will form a PIREP working group to address issues associated with the dissemination of PIREPs.

Text from the NTSB. Open the NTSB docket for ANC12IA024 for the full record.