On May 12, 2017, about 1930 mountain daylight time, a Mooney M20TN, N9306, sustained substantial damage to its right wing during an overrun after a loss of engine power during an aborted landing from runway 27 at Granby-Grand County Airport (GNB), near Granby, Colorado. The pilot was not injured. The aircraft was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which was not on a flight plan. The flight originated from the Centennial Airport (APA), Denver, Colorado, at an unconfirmed time.

The pilot reported that during landing, the airplane bounced and that he added engine power to abort the landing but the engine lost all power. He stated that the propeller was still windmilling and he thought the power loss was due to the high altitude and full rich mixture used on approach. He leaned the fuel mixture thinking that the engine would restart but when it didn't, he applied brakes and attempted to stop on the remaining runway. The airplane overran the end of the runway and was damaged.

The pilot had recently purchased and received flight training in the accident airplane during the previous 2 days. He said that he knew he would be operating the airplane from high altitude airports, including GNB (elevation 8,207 ft), and questioned his flight instructor regarding leaning procedures during approach at high altitude airports. He said that the flight instructor told him to adhere to the procedures in the Pilot's Operating Handbook, which instruct pilots to apply full rich mixture on final approach. The pilot reported that he did so on the accident landing approach, but in retrospect believed that the full rich mixture may have created a situation where the engine was not able to respond to throttle input with the combined high density altitude (8,441 ft), and full rich mixture.

A representative of the airplane manufacturer was queried about the possibility of the engine not responding to throttle input, or the spark plugs fouling, during high altitude approaches due to full rich mixture. The manufacturer did not believe this was possible if the fuel control adjustments were properly set up.

Examination of the airplane revealed that movement of the fuel mixture control arm on the fuel control was striking a fuel hose within the engine compartment. According to the airplane manufacturer, the hose routing found was not as it came from the factory. Although the mixture control arm was striking the hose at the end of its travel it did not appear that the travel of the mixture arm was limited when compared to the factory installation. No other anomalies were found with respect to the airplane or engine; however, the spark plugs and fuel controls were not removed during the engine examination.