Accident Overview
On November 3, 2012, at about 1040 central daylight time, a Cessna 172S, registration N985GE, impacted an automobile while on final approach to runway 17 at Northwest Regional Airport (52F) in Roanoke, Texas. The airplane was operated by Marcair, Inc. under 14 Code of Federal Regulations Part 91 as a solo instructional flight. Visual meteorological conditions prevailed, and the flight was operated on a visual flight rules flight plan. The cross-country flight originated from Possum Kingdom Airport (F35) in Graford, Texas, around 1005, with an intended destination of 52F.
Sequence of Events
The student pilot reported that he was returning from a solo cross-country flight and entered a left traffic pattern for runway 17 at 52F. He recalled that the approach was normal and airspeed was about 60 knots when crossing the fence near the end of the runway. Just after crossing the fence, the landing gear impacted an automobile, resulting in a hard landing. The nose and left main landing gear collapsed, and the airplane veered off the right side of the runway before coming to rest in the grass. The student pilot stated there were no malfunctions or failures associated with the airplane before the impact.
The driver of the automobile reported that he had been to the airport before and was aware of the proximity of the road to the runway, describing the layout as "precarious." He did not see or hear the approaching airplane prior to the accident, although he had rolled down the car windows and turned off the radio to assist in hearing any airplane traffic. He stated the vehicle was about halfway across the road immediately north of the runway when he first heard the airplane engine, and the airplane impacted his car immediately afterward. He noted the airplane struck his car about 4-1/2 feet above the road.
Airport Details
The accident airport consisted of a single north-south oriented runway, designated 17/35, with published dimensions of 3,500 feet by 40 feet. The Federal Aviation Administration (FAA) Airport Facility Directory (AFD) current at the time noted a 400-foot displaced threshold for runway 17, but the actual threshold displacement was approximately 140 feet at the time of the accident. Satellite imagery indicated that runway threshold markings changed between June 12, 2011, and the accident date. The edge of the roadway crossing the runway 17 approach path was located about 25 feet from the end of the runway and about 165 feet from the displaced threshold. The roadway had a faded "Stop" indication painted on the pavement at each side of the runway, but there were no signs requiring drivers to stop or advising them of low-flying aircraft. Because the airport was privately owned, management was under no obligation to maintain the airport to any federal standard.
FAA airport design guidance specifies a standard approach slope of 20:1 (about 3 degrees). Guidance on Visual Approach Slope Indicators (VASI) notes a standard glide path angle of 3 degrees, but it may be up to 4.5 degrees if necessary for obstacle clearance. The calculated glide path height above the roadway, considering the 165-foot distance from the displaced threshold to the edge of the roadway, would be 8.6 feet for a 3-degree glide path and 13.0 feet for a 4.5-degree glide path. This does not account for elevation differences between the roadway and runway or safety margins for momentary operations slightly below the glidepath.