A Transportation Safety Board (TSB) investigation has concluded a runway overrun at Prince Rupert Airport (YVR) in February was likely caused by slippery conditions on the tarmac.
On Feb. 7 at approximately 7:45 a.m., a chartered Air Summit Flight from Nanaimo with 34 passengers and four crew on board arrived in Prince Rupert. Upon touching down and applying the first set of hydraulic brakes, the flight crew noticed no deceleration so switched to the second set of brakes with a similar lack of result, the TSB report states.
"As the aircraft started to lose speed and neared the end of the runway with little appreciable deceleration from the application of brakes with either hydraulic system, the flight crew activated the emergency brake system in a final attempt to slow the aircraft," wrote TSB investigator Glenn Whitney.
"The flight crew also initiated the shutdown of engines No. 1 and No. 4 in an attempt to reduce thrust. As the aircraft was approaching the end of the runway, the captain tried to steer it using the nose wheel tiller. The aircraft started to slide sideways, and it subsequently contacted two runway end lights and slid beyond the end of the runway by approximately 30m."
There were no reported injuries and the aircraft, a British Aerospace Avro 146 Series RJ100, sustained only minor damage.
The investigation concluded that the last runway surface condition (RSC) assessment had been issued at approximately 1:30 p.m. the previous day (Feb. 6) and that Summit Air had not requested a new one before arrival.
There was, however, an automatic aerodrome routine meteorological report (METAR AUTO) available issued at 7 a.m. that indicated the temperature was -1C. The investigation also determined that while it had not been forecast for YPR, a previous METAR AUTO from approximately 11 hours before the flight arrived had recorded 29 minutes of freezing precipitation.
A new RSC assessment was done following the incident and noted the Canadian Runway Friction Index measurements for the runway (measured in thirds of the length of the runway) were 0.19, 0.23, and 0.21 at -1C.
"These small numbers represent low braking coefficients of friction," wrote Whitney. "In contrast, numbers from approximately 0.8 and above indicate the braking coefficients associated with dry runways."
The TSB investigation was classified as a Class 4 investigation, which is a lower-level classification. This means that while an incident could have some serious outcomes such as injury or death, it generally involves minor localized damage, is of local interest only and the likelihood of identifying new safety lessons and advancing transportation safety is low.
Since the incident, Summit Air has amended its standard operating procedures and Air Flight Dispatch Manual. Two amendments require coordination between the pilot-in-command and dispatch when runway conditions are of concern, particularly when runway reports are not unavailable.
Three of the amendments prohibit flight crews from initiating an approach if the temperature is below 5C unless the crew has a runway report. If a runway report has expired the crew must check the historical weather reports for precipitation and high winds that could create large snow drifts and for temperatures falling from above 0C to below 0C that could allow ice or frost to form on a runway.
