In its recently published findings into the Feb. 21, 2022, runway excursion of a Hawker 800XP, the NTSB raised a concern about the term “instantaneous wind.” The twinjet went off the end of the runway during an aborted tailwind takeoff from Colorado’s Aspen-Pitkin County Airport (KASE) after the pilot was unable to rotate. The aircraft overran the runway into snow, substantially damaging the right wing and fuselage, but there were no injuries to the two pilots or four passengers.
When the airplane was cleared to depart, the ATIS-reported wind direction and speed exceeded the aircraft’s maximum tailwind takeoff limitation. Aspen Tower also reported a so-called “instantaneous” wind velocity that was less than the takeoff limitation, and this is what the captain used to make his decision to depart. Nevertheless, the NTSB attributed the accident to the flight crew’s “improper decision to take off in tailwind conditions that exceeded the airplane’s performance capabilities, which resulted in a runway overrun following an aborted takeoff.”
The Safety Board noted in the final report that the “instantaneous wind” term used by Aspen is not defined in any FAA publication. “Because the ambiguous term is not defined in available resources, pilots that infrequently operate at that airport are likely not familiar with the definition and potential operational impact.” Despite this concern, the NTSB made no recommendation asking the FAA to clarify the term.