Pilot Debrief

BOMBARDIER INC CL-600-2C10 near Salt Lake City, UT — 2010-11-24

Final reportWPR11LA058
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Date
2010-11-24
Location
Salt Lake City, UT, USA
Airport
SLC
Aircraft
BOMBARDIER INC CL-600-2C10
Registration
N614SK
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Ground

Probable cause

The tug driver’s loss of airplane control during pushback due to a loss of traction in slippery conditions on the ramp. Contributing to the accident was the ground crews’ and airline operators’ inadequate guidance with regard to pushback procedures during low ground traction conditions with an inoperative airplane auxiliary power unit.

Contributing factors

Contributing to the accident was the ground crews’ and airline operators’ inadequate guidance with regard to pushback procedures during low ground traction conditions with an inoperative airplane auxiliary power unit.

NTSB narrative

The airplane was operating 2 hours behind schedule and had been dispatched with its auxiliary power unit (APU) inoperative, a condition that was permissible based on the approved Minimum Equipment List. The ramp area was covered in snow and ice, and it was snowing during aircraft loading and the subsequent pushback attempt. The captain started both engines while the airplane was at the gate, utilizing an external air-start cart in lieu of the APU. The captain stated that he started both engines due to a concern that, by starting one engine only, he would encounter control problems taxiing in the slippery conditions. He recognized that he could also have attempted to start the second engine in the alleyway after pushback using a cross-bleed engine start, but was concerned that attempting such a start would require increased engine thrust on the operating engine and could be disruptive to ground personnel and other traffic within the alleyway. During pushback, the tug was unable to gain enough traction to move the airplane and was subsequently replaced with a larger tug. The larger tug was able to push back the airplane; however, a short time later the thrust from the airplane's engines, which were running at idle, exceeded the traction available to the tug. The captain, seated in the left seat, experienced a sensation of unusual movement as the airplane began to overpower the tug, and he asked the tug driver if the driver still had control of the airplane. The tug driver confirmed that he had control; however, the airplane subsequently moved forward while still attached to the tug, which rotated to the right striking the airplane's fuselage. According to ground personnel and flight crew guidance, if the ramp surface conditions were such that adequate traction was not available, engine start should have been delayed until the pushback was complete. However, an engine start was required prior to pushback due to the inoperative APU. No guidance existed for either the flight or ground crew regarding pushback procedures in low traction ramp conditions with an inoperative APU.

Analysis

Primary failure mode
Human factors
First missed decision gate
Captain could have delayed engine start until pushback was complete due to slippery conditions.

NTSB coding

Evidence available

  • CVR
  • FDR / data
  • Photos
  • 12 docket documents
View NTSB final reportView NTSB docket

Docket documents12

Related mishaps

BOMBARDIER INC CL-600-2C10 near Salt Lake City, UT — 2010-11-24 · Pilot Debrief