Incident Overview
At 0918 central standard time on December 14, 2012, a Swearingen SA227-AC, registration N3108B, operated by Encore Air Cargo, experienced a runway incursion with a snowplow at Sloulin International Airport (ISN), Williston, North Dakota. The pilot was not injured, and the airplane was not damaged. The aircraft was being repositioned under 14 Code of Federal Regulations Part 91 on an instrument flight rules flight plan. Instrument meteorological conditions prevailed at the time. The flight was originating with an intended destination of Joe Foss Airport (FSD), Sioux Falls, South Dakota.
Pilot's Account
The pilot reported making several radio calls announcing his intention to depart on runway 29. He did not hear any radio calls from other aircraft or vehicles. He initiated the takeoff, and at the end of the takeoff roll, he heard a "garbled" transmission stating something about runway 11/29. As he lifted off, he saw a snowplow on the runway heading in the opposite direction. He continued the takeoff and flew over the snowplow.
Snowplow Driver's Account
The snowplow driver reported that he did not hear any radio transmissions from the airplane until after it was airborne, when the pilot reported that he was airborne and leaving the area. The driver stated he had been plowing in the area for about 30 minutes and had made radio calls announcing his position every 2–3 minutes.
Airport Operations and Training
Sloulin International Airport is a non-towered airport fully certificated under CFR Part 139. Snow removal personnel are employees of the airport. According to the airport manager, vehicle drivers receive initial training upon hiring and annual training thereafter, which addresses airport communications and operations around aircraft. The airport was in the process of upgrading radios in all airport vehicles. The snowplow involved in this incident was a new vehicle with an upgraded radio, and the radio functioned normally when checked after the incident.
Weather Conditions
Local visibility and cloud conditions recorded approximately 13 minutes prior to the incident were ¾ mile with mist and a 100-foot overcast ceiling.
Additional Witness
Another pilot who landed about 30 minutes after the incident reported seeing a "semi truck size snow broom" sitting on taxiway A on the west side of runway 2/20. He cleared the runway and, while taxiing to the ramp, observed the snowplow cross runway 2/20 and also be on the ramp. He did not hear the snowplow driver make any radio calls.
FAA Guidance
The Federal Aviation Administration's Guide to Ground Vehicle Operations states: "Always yield the right-of-way to moving aircraft." It also states: "Before you cross a runway, ensure that no potentially conflicting aircraft are taxiing, landing or taking off."