Mooney M20 N304MA

Summary

On 12 February 2023 at about 15:58 local time, a Mooney M20 registered N304MA was involved in an accident near Lakeway, Texas, United States. One person was on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

12 February 2023 at 15:58

Classification

Accident

Location

Lakeway, Texas, United States

Coordinates

30.3632, -97.9953

Aircraft

Mooney M20

Registration

N304MA

Category

Airplane

Year built

1997

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Spring Branch → Clarksville

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CEN23LA107

Nobody was injured.

A total loss of engine power due to detonation and preignition in the No. 6 cylinder.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

Before purchasing the airplane, the pilot had an inspection performed. One of the findings on the inspection stated that, “spark plugs are worn past limits.” There were no indications that the magneto timing was checked during the inspection. The pilot reported that the airplane had been run with a lean mixture in the past. After the pilot purchased the airplane, he flew the airplane on a cross-country flight to relocate it to his home base. While in flight, the engine had a low manifold pressure reading and then the engine sustained a total loss of power. The pilot attempted to fly to the nearest airport, but instead performed a forced landing to a golf course. During the forced landing sequence, the airplane impacted trees and a wood fence, and came to rest near a diesel generator. The airplane sustained substantial damage to the fuselage and to both wings. Examination of the airframe revealed no mechanical anomalies. Examination of the engine revealed a hole in the corner of the No. 6 piston; however, the No. 6 cylinder was intact. The No. 6 piston had eroded crown material and a darkened periphery. The engine case was found intact. The top spark plugs from the Nos. 3, 5, and 6 cylinders and the bottom spark plugs from the Nos. 3 and 5 cylinders were found in a “worn out - normal condition.” The right magneto timing was found at 22°, when it is supposed to be at 20°. The left magneto timing was found at 15°, when it is supposed to be at 20°. The oil breather tube was found intact, and the slot was not blocked. Engine oil was found splattered in and around the oil breather tube area, including traveling rearward on the area underneath the oil breather tube. No anomalies were noted with the turbocharger system or the propeller. It is likely a total loss of engine power occurred when the No. 6 piston developed a hole from burn through, consistent with detonation and preignition signatures consisting of combustion deposits and excessive temperature exposure. The hole in the piston likely allowed exhaust gases, caused by the detonation and preignition, to force engine oil out of the oil breather tube. The combination of the engine being previously run with a lean mixture, worn spark plugs, and incorrect magneto timing, likely lead to the preignition and detonation and a subsequent total loss of engine power.

Quoted verbatim from the NTSB record.