Stall Test in Icing Cited in 2024 Hawker 900XP Accident

A Hawker 900XP crashed in Utah on Feb. 7, 2024, after the flight crew conducted a post-maintenance stall test in icing conditions, resulting in wing contamination, degraded aerodynamic performance, and a loss of control from which the pilots were unable to recover, according to the NTSB’s final report. The accident killed both crew members.

The business jet departed on a Part 91 positioning flight from Grand Junction Regional Airport (KGJT), Colorado, after the airplane underwent routine maintenance that included the removal and reinstallation of the wing leading edges and de-icing panels. While climbing to 20,000 feet msl, the crew initiated a planned stall warning and identification system check. Flight data showed the airplane slowed and pitched up before entering a stall at essentially the same moment the stick shaker activated.

The NTSB found that the degraded stall warning sequence was likely caused by wing contamination from icing or recent maintenance, noting that even brief icing exposure could reduce lift and critical angle of attack substantially. The investigation determined the airplane entered a flat spin and descended rapidly until impact, with no evidence of mechanical anomalies in the engines or flight controls.

Investigators also cited deficiencies in pilot preparation and manufacturer guidance. Although the pilots had received simulator training on stall avoidance systems, the NTSB found they were not adequately trained to conduct full stall tests or respond to unacceptable stall characteristics. The manufacturer’s guidance did not clearly define experience or training requirements for pilots conducting stall tests.

”After the airplane entered the stall, the flight crew input full left-wing-down aileron when the airplane abruptly banked right and applied full power and full aft control column, which aggravated the aerodynamic stall/spin. The flight crew’s attempted remedial action suggested that they were insufficiently trained for the flight and the brief guidance from the POM provided no clear instructions,” the report noted.

Contributing factors included the crew’s decision to conduct the stall test in conditions that did not meet the airplane’s operating manual requirements for visual meteorological conditions, cloud clearance, altitude limits, and ice-free external surfaces.

The findings echo safety issues identified in other post-maintenance test flights, including a recent Hawker 800XP accident during a post-maintenance flight that AIN reported on earlier this year.