On 12 April 2007, a Bombardier CRJ-600 being operated by Pinnacle Airlines on a scheduled night passenger flight from Minneapolis-St. Paul to Traverse City overran the end of the slippery landing runway by 90 metres in normal visibility. There were no injuries to any of the 52 occupants but the aircraft sustained substantial, but repairable, damage, primarily at the forward lower fuselage.
An Investigation was carried out by the National Transportation Safety Board (USA) (NTSB). It was established that the PF for the accident flight had been the aircraft commander, who had been acting as a Line Training Captain in respect of the required initial operating experience (OE) of the inexperienced First Officer. The Captain told the Investigation that he had initially tried to find another check airman to conduct the First Officer’s OE because the accident pilots were personal friends. However, no other check airman was available and he had attempted to perform the OE with the same strictness he would have done for any other candidate.
The accident landing took place outside the hours of ATC TWR service as would have been the case even if it had arrived on schedule. This meant that the only current information on the actual conditions for landing available to the flight crew were broadcasts of automated surface observations (ASOS) and R/T conversations with the ground operations personnel at Traverse City, with ATC service for the ILS approach being limited to that provided area ATC. The Investigation noted that Federal Aviation Administration (FAA) Regulations for provision of ATC TWR service are based solely on the amount of traffic at the airport, specifically the number of flight operations per hour. According to local procedures, the ATC TWR “will remain open longer than the designated hours if an inbound or outbound flight crew requests such staffing”. However, the FAA indicated to the Investigation that such requests were uncommon, and confirmed that no such request had been made on the night of the accident.
The flight crew had been advised that snow clearance had been undertaken and about 16 minutes prior to landing, the airport operations supervisor advised the pilots that the measured braking action on the landing runway 28 was “40+ with “thin wet snow (over) patchy thin ice.” About 2 minutes from landing, in the vicinity of the approach FAF, the same source advised the crew that the braking action was estimated as “nil” and the probable snow depth was 1.25cm. The required visual reference for landing off the ILS approach was obtained just prior to MDA and the Flight Data Recorder (FDR) data showed that the aircraft had crossed the landing runway threshold at Vref + 6 knots before touching down approximately 730 metres along the 1980 metre long runway. A speed of 47 knots was recorded as the aircraft overran the far end of the runway. Two minutes after the overrun, the ASOS Report gave the surface wind velocity as 020° / 8 knots, visibility of less than 500 metres in heavy snow, sky obscured with vertical visibility 200 feet and Temperature 0°C. This was a deterioration compared to the last broadcast ASOS Report which the flight crew had accessed about half an hour before landing which gave a wind velocity of 040° / 7 knots and a visibility of 2800 metres in light snow.
The Investigation carried out a landing performance study calculation using the runway conditions which prevailed for the accident flight and concluded that the aircraft could only have completed a landing on the available runway length with the usual 15% safety margin for compacted snow conditions, which were not the prevailing snow condition.
The Investigation also considered that given that the accident had occurred at the end of a long and demanding duty day, flight crew fatigue was likely to have played a part in “the poor decision-making shown by the accident pilots, including their failure to account for the changing weather and runway conditions during the approach; their failure to perform a landing distance calculation; and their failure to reassess or discontinue the approach accordingly”. The fact that the Operator had a policy that allowed pilots to remove themselves from trips because of fatigue was noted and it was considered possible that the accident pilots did not elect to do so because they did not recognise their level of fatigue until they were en route.
The Conclusions of the Investigation also included the following:
- The pilots failed to perform the landing distance assessment that was required by (the Operator’s procedures) and that had they done so, using current weather information, the results would have shown that the runway length was inadequate for the contaminated runway conditions described.
- Because the pilots had ample evidence that wet snow was accumulating rapidly on the runway at (the destination) Airport, they should have anticipated a landing on a contaminated runway and performed a landing distance assessment as required by (Company procedures).
The Probable Cause of the accident was determined as:
“The pilots’ decision to land (at the destination airport) without performing a landing distance assessment, which was required by company policy because of runway contamination initially reported by (destination) ground operations personnel and continuing reports of deteriorating weather and runway conditions during the approach. This poor decision-making likely reflected the effects of fatigue produced by a long, demanding duty day and, for the Captain, the duties associated with check airman functions”.
It was also considered that the following contributed to the accident:
- The FAA pilot flight and duty time regulations that permitted the pilots’ long, demanding duty day and
- The (destination airport) operations supervisor’s use of ambiguous and unspecific radio phraseology in providing runway braking information.
Four new Safety Recommendations were made to the FAA as a result of the Investigation to:
- Emphasise with Principal Operations Inspectors the importance of conducting timely post accident drug and alcohol testing. (A-08-40)
- As part of the Takeoff/Landing Performance Assessment Aviation Rulemaking Committee, address the need for initial training on the rationale for and criticality of conducting landing distance assessments before landing on contaminated runways. (A-08-41)
- Issue a CertAlert to all 14 Code of Federal Regulations Part 139 certificated airports that describes the circumstances of this accident, emphasizes the importance of specific and decisive radio communications, and urges airports to ensure that those criteria are being met in all airfield radio communications. (A‑08-42)
- Require all 14 Code of Federal Regulations Part 139 certificated airport operators to include in their airport’s snow and ice control plan absolute criteria for type and depth of contamination and runway friction assessments that, when met, would trigger immediate closure of the affected runway to air carrier operations. Friction assessments should be based on pilot braking action reports, values obtained from ground friction measuring equipment, or estimates provided by airport ground personnel. (A-08-43)
The Final Report of the Investigation was adopted on 10 June 2008 and may be seen in full at SKYbrary bookshelf: NTSB/AAR-08/02 PB2008-910402