Gusty tailwinds reportedly proved too strong to allow the pilots attempting to take off in a Hawker 800XP to lift the nose at rotation speed on Feb. 21, 2022, at Colorado’s Aspen/Pitkin County Airport, the National Transportation Safety Board said. No one was injured after the crew aborted the takeoff and the jet went off the runway and into the snow, although the Hawker was substantially damaged.
According to the NTSB final report, the probable cause of the accident was “the flight crew’s decision to take off in tailwind conditions that were consistently above the airplane’s tailwind limitation, which resulted in a runway overrun following an aborted takeoff. Contributing was the flight crew’s use of the instantaneous wind report for the decision to attempt the takeoff.” Like many business jets, the Hawker’s tailwind takeoff limitation is 10 knots.
When the Hawker was cleared to taxi to Runway 33, the wind was reported at 170 degrees at 18 knots, gusting to 30 knots. After a delay due to arriving traffic, the tower controller cleared the Hawker for takeoff and, according to the NTSB, “reported the wind was from 160 degrees at 16 knots, gusting to 25 knots, and the ‘instantaneous wind’ was from 180 degrees at 10 knots.”
The tower controllers must use the two-minute average wind as the official wind report, based on the standalone weather sensor (SAWS) readings, according to the Aspen tower standard operating procedures (SOPs). Further, “If a pilot requests, the instantaneous wind may be issued after the SAWS two-minute average wind has been given.” The ATIS broadcast is also supposed to include a warning if the wind is above a 10-knot sustained tailwind or gusting above a 15-knot tailwind between headings of 100 to 200 degrees for Runway 33.
However, according to the NTSB, there appears to be no actual definition of “instantaneous wind” and no guidance on whether pilots should use it to try to take off at a moment when the gusts appear to die down enough to avoid exceeding a tailwind limitation. The FAA previously told AIN that “instantaneous wind” gives the pilot a three-second snapshot of current wind conditions.
“‘Instantaneous wind’ is a term used by ASE [Aspen control tower] that is not defined in any FAA publication of record,” the NTSB report noted. “After the accident, the ASE ATM [air traffic manager] was asked why ASE ATC chose to use the phrase ‘instantaneous wind’ when reporting the standalone weather, and the manager stated he was not sure where that [term] had originated. He reported that a few operators routinely request the instantaneous wind reports because of their familiarity with ASE operations, but other operators and general aviation pilots may not be aware of instantaneous wind reports or the definition of the term. In addition, as specified in the ASE SOPs, the instantaneous wind report is only supposed to be provided when requested.”
The Flight Safety Foundation offered some additional insight on this topic: “If an instantaneous wind reading is desired and is requested from ATC, the phraseology ‘instant wind’ should be used in the request. (ATC may provide instant-wind information without request under shifting/gusting wind conditions.)”
When asked about the use of instantaneous wind, an FAA spokeswoman told AIN, “We provide the information so that pilots can make the best decisions for the aircraft.”
In this particular case, it appears the pilots did not request the instantaneous or instant wind from the tower controller.
According to the report, “The flight crew, using a weight of 23,916 pounds and flaps 15 degrees, calculated the airplane’s V1 and VR airspeeds to be 111 knots and 121 knots."
The pilot-in-command and pilot flying from the left seat submitted this report to the NTSB: “We were cleared for takeoff and ATC reported constant winds of 180/10 knots. For takeoff, used all available runway and performed a static takeoff. FO made all callouts, airspeed alive, 80 knots, V1, and rotate. At rotation speed I pulled back on the yoke and there was no slightest indication of nose wheel coming off the ground or airplane becoming airborne. Moreover, the yoke did not have any air resistance or any pressure on it as we experience normally in Hawkers (the weight and pressure on the yoke felt the same as though…the airplane was stationary on ground). I did not [have] any elevator authority as I was pulling back on the yoke during the rotation. The airplane kept accelerating down the runway without any sign of lift off. I continued pulling the yoke for few seconds and when I was absolutely certain the airplane wasn’t responding to my inputs. I immediately decided and called for an abort before the airplane could gain further speed, which would [have] caused more serious issues. Performed the abort with power to idle, all available braking, [thrust reversers], and air brakes. Unfortunately there wasn’t enough runway available for stopping on the runway and the airplane went off the end of the runway into approximately 6 inches of snow. As the aircraft departed the runway, I did not [have] any directional control of the aircraft at that point. The airplane came to an abrupt stop approximately 150 to 200 yards from the end of the runway.”
“At VR, the airplane’s pitch control authority should have been sufficient to raise the airplane’s nose and begin liftoff,” the NTSB report noted. “However, the flight crew reported that the airplane did not rotate. This could imply that when the pilot pulled back on the yoke, that the airplane’s airspeed was insufficient to induce rotation."
“Therefore, for a reported VR of 121 knots, the airplane should have lifted off after reaching an airspeed of 110 knots. A 35-knot wind would not reduce the maximum achieved ground speed of 165 knots sufficiently to prevent the airplane from flying, and thus after achieving V1 (111 knots), the flight crew should have had sufficient air load to rotate the airplane."
“This was not consistent with the flight crew account that the yoke did not have any air resistance when the yoke was pulled back, considering that the wreckage examination revealed no discrepancies with flight control continuity to the elevator system. Even if a tailwind increased to more than the maximum reported gusting of 25 knots after VR or if the flight crew call to rotate was made before VR was achieved, the airplane’s airspeed should have resulted in noticeable air resistance when the yoke was pulled back. These discrepancies could not be resolved with the available evidence.”
According to the NTSB, "Following the accident, the operator informed its flight crews to no longer consider 'instantaneous wind' reports in their decision-making process."