SEA96LA055
SEA96LA055

On February 15, 1996, approximately 1300 mountain standard time, a Cessna 172P, N96879, registered to and operated by Minuteman Aviation of Missoula, Montana, received substantial damage after it departed the runway following a loss of control on landing roll at Lemhi County Airport, Salmon, Idaho. The student pilot, who was on a 14 CFR 91 solo cross-country instructional flight from Missoula, was not injured. Visual meteorological conditions existed and a visual flight rules (VFR) flight plan had been filed.

The pilot was landing on runway 17 at Salmon (5,150 by 60 feet, elevation 4,045 feet above sea level.) Winds at the time were calm. The pilot stated: "...I was on a decent approach, full flaps in, on centerline. As I was flaring in ground effect, I noted a slight left yaw. As I tried to correct for this, the right main touched down and I instantly started to jitter. I further tried to correct the problem. The airplane started a pronounced skid off the runway and I attempted an immediate go around, at which time the aircraft somehow flipped on its back side...."

The FAA on-scene investigator reported that the airplane came to rest in an inverted position, with its nose pointed west, in an irrigation canal approximately 90 feet to the left of runway 17. Post-accident investigation revealed sidewise flat spots on both main tires. The right main wheel would not turn until the right main brake line was disconnected and fluid released. The right main brake torque plate was bent. Photographs taken at the accident scene showed the bottom of the forward part of the right main wheel fairing partially separated from the remainder of the fairing. The nosewheel was broken off at the fork and was located behind the airplane (with respect to its direction of travel) in a rock pile. The portion of the nose gear strut which remained attached to the aircraft was bent aft and cocked to the right. The left main wheel turned freely and no damage to the left main wheel or wheel fairing was visible in the photographs. The rudder and pedal position were slightly left of center in the photographs; the right rudder pedal was jammed into the firewall, which was shown buckled in this area. The control yokes were rotated about 50 degrees to the left. A control cable continuity check revealed no abnormalities. There was a skid mark on the runway approximately 90 feet long, starting at approximately the midpoint of the runway and arcing from the approximate runway centerline to the left edge of the runway. The aircraft was lying about 120 to 130 feet down the length of the runway from the end of the skid mark.

The 1984 Cessna 172P pilot's operating handbook specifies a flaps-down landing airspeed of 60 to 70 knots indicated airspeed (KIAS) for a normal landing. Based on an airspeed of 60 KIAS, a density altitude of 4,000 feet, and no wind, the time for the airplane to travel 90 feet (the approximate length of the skid mark) was calculated to be 0.84 seconds. The straight-line distance from the end of the skid mark (at the left edge of the runway) to the aircraft wreckage was calculated to be approximately 158 feet, based on 90 feet laterally from the runway and 130 feet down the runway. The time for the aircraft to travel 158 feet at 60 KIAS, 4,000 feet density altitude and no wind was calculated to be 1.47 seconds. The angle off the runway centerline from the beginning point of the skid mark to the end point of the skid mark, based on a distance of 30 feet from the runway centerline to the runway edge and an approximate distance of 90 feet from the beginning of the mark to the end of the mark, was calculated to be 19.5 degrees.

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