MOONEY M20K

Full Narrative

On February 10, 2024, about 12:45 mountain standard time, a Mooney M20K airplane, C-FLQQ, was substantially damaged when it was involved in an accident at Burley Municipal Airport (BYI) Burley, Idaho. The pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal cross-country flight.
The pilot reported that, while on a cross-country flight at a cruise altitude of FL 240, he observed a substantial drop in engine oil pressure and a subsequent loss of throttle response. Due to the engine’s low oil pressure, the pilot declared an emergency and diverted to BYI. He was cleared to land on runway 06. The wind indicated about a 7 knot tailwind during the landing. The runway had a displaced threshold that was 796 ft long, allowing for 3,276 ft of available runway for landing.
The pilot stated that the approach was high and fast. He did not think he had enough altitude to circle around for another approach so he pushed the airplane’s nose down to lose altitude. However, his effort to lose altitude allowed the airplane’s speed to increase to about 88 knots during the landing. The pilot further stated that the airplane started to bounce during the landing and that he could not keep the tires on the ground as he tried to brake. Subsequently, the airplane exited the end of the runway, into the grass, and then struck a fence and metal container before it came to rest about 760 ft from the departure end of the runway.
A review of ADS-B data revealed that the airplane was flying in from the northwest and the last data point, about 1 1/4 miles northwest from the runway, revealed that the airplane was heading about 135° magnetic, about 4,700 ft with a -1,216 ft-per-minute vertical rate, and a groundspeed of about 126 knots.
The airplane’s Pilot Operating Handbook (POH) stated that the total oil capacity was 8 quarts and the minimum oil capacity for flight was 5 quarts. The normal operating range for the oil pressure was 30-80 psi. The oil quantity was required to be checked during the exterior preflight check. Additionally, the POH stated that during a normal landing, the airspeed on final was 75 knots. The landing runway indicated about 7 knots of tailwind and the landing distance chart indicated that, at a medium weight and with the tailwind factored in, the calculated landing distance was about 2,700 ft.
FAA Advisory Circular 91-79B, Aircraft Landing Performance and Runway Excursion Mitigation, indicates that both unstabilized approaches and excess airspeed have been shown to increase the risk of a runway overrun. “As a rule of thumb, on dry or wet runways, a 10 percent increase in final approach speed results in a 20 percent increase in landing distance.”
During the postaccident examination of the airplane, the engine was rotated manually, and thumb compression was established at each cylinder and appropriate valve movement was noted. The cylinder overhead components were lubricated and undamaged. The oil lines were secured and intact and the oil filter, oil pickup screen, and governor oil screen were all clear of contaminants.
Initially, only about 1/4 inch of oil was noted on the oil quantity dip stick. After 4 quarts of oil were added, the oil quantity measured from the oil quantity dip stick was about 6 quarts, consistent with about 2 quarts of oil being initially present. The engine was motored from the starter, and 34 psi of oil pressure was indicated. During the motoring, no oil leaks were detected. There was no evidence of oil leaks on the exterior of the airplane, the oil lines, on the engine exterior, or on the engine cowling panels. The airplane’s engine could not be run because the examination facility did not have the appropriate means to secure it.
Overall, the examination revealed no evidence of preimpact failures or malfunctions that would have precluded normal operation of the airplane.
The pilot did not submit the National Transportation Safety Board Pilot/Operator Aircraft Accident/Incident Report Form 6120.1.