Unstabilised Approach Accident at Aspen

Unstabilised Approach Accident at Aspen

On 5 January 2014 Bombardier CL-600-2B16 Challenger N115WF impacted the runway during landing at Aspen (ASE), Colorado (a “high-altitude, terrain-limited airport”).

Wreckage of CL600 Challenger N115WF at Aspen (Credit: NSTB)

Wreckage of CL-600 Challenger N115WF at Aspen (Credit: NSTB)

The copilot was killed and the captain and passenger received serious injuries. The US National Transportation Safety Board (NTSB) describe in their final report that:

As the flight neared its destination…air traffic control (ATC) provided vectors to the localizer/distance measuring equipment (LOC/DME)-E approach to runway 15. About 1211, the flight crew reported that they were executing a missed approach and then requested vectors for a second approach. ATC vectored the airplane for a second LOC/DME-E approach to runway 15. About 1221, the local controller informed the flight crew that the wind was from 330° at 16 kts and the 1-minute average wind was from 320° at 14 kts gusting to 25 kts. The weather at the time of the accident was near or in exceedance of the airplane’s maximum tailwind and crosswind components for landing, as published in the airplane flight manual…: “the maximum tailwind component approved for take-off and landing is 10 kts.” The initial part of the airplane’s second approach was as-expected for descent angle, flap setting, and spoilers. During the final minute of flight, the engines were advanced and retarded five times, and the airplane’s airspeed varied between 135 kts and 150 kts. The final portion of the approach to the runway was not consistent with a stabilized approach. The airplane stayed nose down during its final descent and initial contact with the runway. The vertical acceleration and pitch parameters were consistent with the airplane pitch oscillating above the runway for a number of seconds before a hard runway contact, a gain in altitude, and a final impact into the runway at about 6 g.

Wreckage of CL600 Challenger N115WF at Aspen (Credit: NSTB)

Wreckage of CL-600 Challenger N115WF at Aspen (Credit: NSTB)

The NTSB say that both crew had low experience on type (the captain having no more than 14 hours):

Airport surveillance video of the runway showed the airplane landing at ASE. The following sequence of events was seen in the video: the airplane above the runway in a slightly nose-down attitude, a flash of light consistent with a runway strike, the airplane in the air above the runway in a nose-down attitude, and the airplane impacting the runway in a nose-down attitude and being engulfed in light. About 4 seconds elapsed between the runway strike and the final impact. https://youtu.be/KAorF4UfMpU …performance calculations were completed to determine if the airplane could successfully perform a go-around. Assuming the crew had control of the airplane, and that the engines were advanced to the appropriate climb setting, anti-ice was off, and tailwinds were less than a sustained 25 kts, the airplane had the capability to complete a go-around, clearing the local obstacles along that path.

The NTSB determined the probable cause to be:

The flight crew’s failure to maintain airplane control during landing following an unstabilized approach. Contributing to the accident were the flight crew’s decision to land with a tailwind above the airplane’s operating limitations and their failure not to conduct a go-around when the approach became unstabilized.

Wreckage of CL600 Challenger N115WF at Aspen (Credit: NSTB)

Wreckage of CL-600 Challenger N115WF at Aspen (Credit: NSTB)

The NTSB also report that shortly after the accident the airport changed its procedures for dissemination of wind information:

1-minute average wind data was established to be the “official winds to be issued” to pilots at ASE. While the local controller provided the 1-minute wind average (and associated gust information) to the accident flight crew during arrival, the procedure in place at the time of the accident allowed wind reporting to be controller discretion. Local controllers at ASE could provide flight crews either the instantaneous wind readings or the 1-minute average with 10-minute gust information. Although the ASOS continued to provide pilots with the 2-minute average wind with 10-minute gust data via the ATIS, the most updated wind data available (the 1-minute average wind data) from the stand-alone weather station (SAWS) was required to be provided by the ASE ATCT controllers.

Safety Resources

IATA Unstable Approaches, Risk Mitigation Policies, Procedures and Best Practices.  The 2nd Edition of this document, collaboratively written by the International Air Transport Association (IATA), the International Federation of Air Line Pilots’ Associations (IFALPA), the International Federation of Air Traffic Controllers’ Associations (IFATCA), the Civil Air Navigation Services Organisation (CANSO) was issued in 2016. More can also be found on the FSF Approach and Landing Accident Reduction (ALAR) project here.

See also:

UPDATE 7 May 2017: We also look at a less dramatic Challenger accident: Ground Collision Under Pressure: Challenger vs ATV: 1-0

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