Accident Report: Snowy Scenarios

Slick surfaces (see “An Icy Situation,” p. 38) and wingtip clearances in tight spaces or between high snow banks become everyday hazards—especially if there’s a cold snap that keeps the accumulated snows from melting for a prolonged period.

Even when the sun is shining, blowing snow can take down visibility and pack your shoveled-out aircraft back into its plowed-out tiedown spot. Checking notices to airmen about surface conditions and braking reports becomes routine.

This winter, pilots will be adjusting to interpreting a new format for field condition (FICON) notams. The new format uses a runway condition assessment matrix to assign values to runway contamination, and it provides guidelines for the practical operational meaning of pilot braking action reports.

That’s an awful lot of information to help pilots cope with the effects of snow, but it doesn’t tell the whole story. Hidden traps remain, so it’s wise to build some season-specific margins into all surface operations, or phases of flight near the surface, at snowy airports—as two accidents from February 2016 illustrated.

Nothing breaks up the monotony of a stormy spell of weather like going flying as soon as the weather clears. Waiting for clean-up operations to proceed may be necessary, but even if the heavy equipment is still rumbling around the airport, the return of fair weather sees pilots quickly getting back in the air when runway closures are lifted.

But all that snow has to go somewhere. Sometimes it is deposited off the runway ends—creating a hazard of ever-changing dimensions that may not stand out appreciably from equally snow-covered surroundings.

Notices to airmen don’t tell the whole story. Hidden traps remain, so it’s wise to build some season-specific margins into surface operations at snowy airports.Such a hazard exacted a heavy price shortly after a four-inch snowfall in Shirley, New York, on February 12, 2016, indirectly bringing about the destruction of a Cessna 152 that was landing at Brookhaven Airport. “The pilot reported that on his second landing he felt a ‘small’ impact just before touchdown, and then the airplane pitched down and skidded to a stop,” said a National Transportation Safety Board accident summary of the mishap, in which the occupants were uninjured but the aircraft caught fire and was destroyed. “The pilot reported that he observed evidence of where the airplane’s nosewheel impacted a snow berm located on the approach to the runway.” He estimated that the snow berm was about five feet high and about 20 feet wide.

The NTSB report also contained information from the airport manager about preaccident weather and field conditions that provided a slightly different description of the offending berm. “The airport manager reported that about four inches of snow accumulated on the ground prior to the accident, but that almost all of the snow had been plowed from the runway. He further reported that the accident airplane’s nose gear impacted a snow berm that was about 10 feet off the end of the runway, and about 28 inches high.”

The bottom line, concluded the NTSB, was that the probable cause of the accident was “the pilot’s failure to maintain adequate terrain clearance while landing, which resulted in a collision with a snow berm, nose gear collapse, and postimpact fire.”

What if you know a surface is snow-covered and there is no FICON available to help with decision-making because the site is not an airport? A snow-covered dry lake bed in Park Valley, Utah, presented that challenge to the pilot of a Cessna 210 single-engine airplane who wanted answers on February 2, 2016—but the answers were more than the pilot bargained for.

According to the NTSB, the pilot “decided to ‘drag’ the left main landing gear to ‘better assess the surface condition.’ When the tire touched down, the pilot reported, ‘Drag rapidly increased and sucked the aircraft down.’” Adding full power to the engine of the high-performance single didn’t help, as “the airplane sunk further into the snow, turned to the right, and nosed over,” causing substantial damage to the fuselage and vertical stabilizer.

The NTSB determined the probable cause of the accident to be the pilot’s decision to drag the left main landing gear on the snow-covered surface, resulting in a loss of directional control “and a nose over during an aborted landing.”