NTSB Factual Report

On February 18, 2005, at 1423 central standard time, a Mooney 20P, N321DT, registered to and operated by the private pilot, collided with a tree during a forced landing into a field in Smith, Alabama. The personal flight was operated under the provisions of Title 14 CFR Part 91 and instrument flight rules. Visual meteorological conditions prevailed and an instrument flight plan was filed. The pilot received serious injuries and the airplane sustained substantial damage. The flight originated in Decatur, Alabama, on February 18, 2005, at 1319.

According to the pilot, while descending on approach into the Columbus Metropolitan Airport, the engine stopped and oil covered his wind shield. The Air Traffic Controller at the Atlanta TRACON was unsuccessful in providing the flight with radar vectors to a grass airstrip in Phoenix City, Alabama. The pilot selected an off-airport location for an emergency landing, and established an approach to land in an open field. The airplane collided with a tree as the pilot maneuvered on the approach to land.

Post-accident examination revealed the airplane came to rest 7 miles west of Columbus Metropolitan Airport. The left wing exhibited circular crush damage on the leading edge, the cockpit door was separated from the fuselage, and the fuselage exhibited damage. Oil was observed on the windshield, and vertical and horizontal stabilizers.

Post-accident examination of the propeller revealed that the propeller remained attached to the engine and exhibited slight damage to both blades, which were found loose in the hub. Examination of the fuel injector servo and flow divider revealed that the servo inlet screen was clean and fuel was found in the lines of the servo and flow divider. The pump was fractured at the flange. Examination of the oil system revealed small metal particles in the oil filter element, but no measurable quantity of oil remained in the engine.

Post-accident examination reveled a lack of torque on the adjacent cylinders hold down nuts. Torque requirements per Lycoming Service Instruction SI No.1029D specifies 600 in/lbs for 1/2 diameter nuts, and 300 in/lbs for 3/8 diameter nuts.

Position Reference: Top Forward (TF), Top Aft (TA), Bottom Forward (BF), Bottom Aft (BA), Damaged (D). The Torque readings were record as follows:

#1 Cylinder 1/2 nuts- TF=550, TA=600, BF=500, BA=550. 3/8 nuts-- TF=300, TA=300, BF=300, BA=300.

#3 Cylinder 1/2 nuts- TF=(D), TA=550, BF=(D), BA=600. 3/8 nuts-- TF=300, TA=300, BF=300, BA=300.

#4 Cylinder 1/2 nuts- TF=400, TA=600, BF=350, BA=550. 3/8 nuts-- TF=300, TA=300, BF=300, BA=300.

Post-accident examination of the engine revealed that the #2 cylinder assembly had separated from the crankcase. Fretting was observed on the cylinder mount pad surface of the crankcase and all of the hold down studs were broken. The #2 cylinder was recovered and exhibited fretting on the mating surface of the base flange. The adjacent crankshaft connecting rod throws #1 and #3 showed signs of heat distress from a loss of oil while operating. All cylinders were removed and the crankcase was disassembled for examination. The interior mating surfaces of the crankcase halves exhibited fretting located at the center main bearing web and at the front main bearing web.

A review of the engine maintenance records revealed that on 12/18/2002, at a tach time of 1142.6 hours, the #1 cylinder assembly was replaced. The cylinder was overhauled by Aviation Engines and installed by North Alabama Aviation. At the time of the accident the tach time was 1228.2, or 85.6 hours since the #1 cylinder assembly had been replaced.

NTSB Probable Cause

Maintenance personnel failure to properly torque the cylinder head during installation that resulted in the separation from the engine assembly and the subsequent loss of power.