Mooney Aircraft Corp. M20K N231MW accident near Elizabeth, Louisiana

Probable cause

The pilot’s failure to set the engine fuel mixture to the required setting, which resulted in reduced engine power during a go-around and subsequent impact with trees. Contributing to the accident, the failure of the mechanic to perform a current fuel injection system calibration.

NTSB analysis

The pilot reported that during a go-around after a bounced landing, the engine did not produce full power. The pilot chose to perform the go-around due to the bounced landing on the short, grass runway. During engine throttle application, the pilot noticed that the airplane did not attain the normal acceleration rate. The pilot verified the position of the cockpit engine controls; however, the airplane was still underperforming. Before the pilot could attempt any further actions, the airplane settled into the tree line at the end of the runway, impacted multiple trees, and came to rest inverted about 4 feet off the ground, which resulted in substantial damage to both wings, the fuselage, and the empennage. Multiple witnesses reported that the engine sounded as if it was not producing full rated power.

Postaccident examination of the airframe revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. However, a review of recorded engine data showed that the engine was not producing full power during the approach, landing, and go-around.

Recorded engine monitor data indicated a sharp drop in the No. 1 cylinder’s Exhaust Gas Temperature (EGT) from 1321° F to 365° F as the pilot was turning onto final approach. Over the next minute, the No. 1 cylinder’s EGT rebounded twice before again falling relative to the other cylinders’ EGTs. When the pilot applied full engine power during the go-around, the No. 1 cylinder’s EGT jumped from 532° F to 863° F for less than one second before again dropping down to 526° F. Three seconds later the No. 1 cylinder’s EGT returned to normal, in line with the other cylinders; however, full engine power was not restored until 11 seconds after the pilot commanded full engine power. This is likely the No. 1 cylinder air fuel mixture was too lean for proper combustion.

At the start of the initial decent, the highest recorded cylinder EGT temperature was 1,467° F and the lowest 1,306° F. At the start of the descent from traffic pattern altitude for landing, the highest recorded cylinder EGT was 1,480° and the lowest was 1,351° F. During the go-around, the fuel flow was steady at about 10 gph until the end of the recording when the fuel flow suddenly increased to 15 gph in about one second.

Additional review of the engine data revealed that during takeoff and initial climb, the maximum recorded fuel flow was 20.6 gph which is 2.4 gallons below the minimum required full engine power fuel flow of 23.0 gph. Review of the maintenance logbooks did not reveal a fuel injection system calibration during the most recent annual inspection as required by manufacturer’s maintenance manual. Due to a lack of recent calibration of the fuel injector system, it is likely that the system would not have provided the required fuel flow to the engine.

On the accident flight, the pilot likely did not enrichen the mixture before starting the descent until after established in the go-around. During the go-around, the pilot likely observed that the mixture was not properly set when he noticed the degraded performance of the engine. This is consistent with the sudden increase in recorded fuel flow and engine power before end of the data and subsequent impact with trees.

Text from the NTSB. Open the NTSB docket for CEN25LA021 for the full record.