Accident Summary
On July 20, 2018, about 1430 central daylight time, a Piper PA60 Aerostar airplane, registration N327BK, experienced a loss of engine power and landed in a field after takeoff from Baton Rouge Metropolitan Airport (BTR), Baton Rouge, Louisiana. The commercial pilot and one passenger were not injured, and the airplane sustained substantial damage. The airplane was operated under Title 14 Code of Federal Regulations Part 91 as a maintenance test flight. Visual meteorological conditions prevailed, and no flight plan had been filed.
Pilot Statement
The pilot stated that after completing a preflight inspection at about 1400, he started both engines. While holding short of runway 31, he performed a pre-takeoff check, including a run-up for each engine, with no anomalies noted. During the takeoff roll, he advanced the throttles to takeoff power and rotated. Shortly after rotation, he noticed the right engine was not producing full power and its speed was decreasing. With no remaining runway to land, he continued and looked for an off-field landing location. He retracted the landing gear and feathered the right propeller. The airplane was unable to maintain altitude, so the pilot made a hard forced landing to a grass-covered field about 1 mile northwest of the departure end of runway 31.
Mechanic Statement
In a postaccident statement, the mechanic who maintained the airplane reported that on the morning of the accident, the right engine was unable to start. He examined the airplane and found the fuel system contaminated with water. The owner and mechanic then examined the left engine. They removed and cleaned the left engine fuel injector nozzles using an ultrasonic cleaner, purged the left fuel tank, removed the fuel line at the flow divider, and flushed the left fuel tank with the electric boost pump. After reconnecting the fuel line, they checked fuel flow by measuring the volume at each nozzle; about 3 ounces was recovered per nozzle. The nozzles were reinstalled, and an engine ground run was completed with no anomalies noted. Next, they performed the same procedures to flush the right engine fuel system and flow check its fuel nozzles. The mechanic stated that the fuel nozzles were not removed on the right engine, but the fuel flow volume was the same as the left engine. No water or other contamination was found in the right engine or fuel lines. An engine ground run was completed with no anomalies noted. The pilot ordered fuel from the FBO and proceeded with his preflight.
Maintenance Records
The mechanic provided copies of recent maintenance records. The most recent entry, dated June 18, 2018, involved reinstallation of an overhauled fuel injection servo and cleaning of the fuel injector nozzles. An engine ground run was completed with no discrepancies noted with the left engine. The records showed that the airplane had accumulated 31.4 hours since July 2014, 3.6 hours since October 2017, and 10.8 hours since September 2016. An annual inspection was completed each year by the same mechanic.
Postaccident Examination
A postaccident examination of the engines and fuel system was conducted by a third-party mechanic under FAA supervision. No apparent external damage was found to either engine case or accessories. The fuel supply lines to the fuel servos appeared clean and exhibited a blue tint consistent with 100 low lead aviation fuel. The amount of fuel retrieved from each fuel servo supply line was estimated to be less than 5 milliliters. The fuel sump drains in the left and right fuel tanks were corroded and unable to move. The cockpit engine controls were stiff but moved through their full range of travel when actuated by hand.
A borescope examination of the left engine revealed that the piston faces were generally clean and free from deposits, erosion, or signs of fouling. The fuel flow divider cover was not safety wired. The No. 6 cylinder lower spark plug wire connector was only hand tight. The No. 1 cylinder top spark plug was over torqued, and its electrode was fouled. Spark plugs for cylinders 2, 4, and 6 were under torqued. The No. 3 cylinder top spark plug was fouled, and its bottom plug was both fouled and improperly gapped. The No. 5 cylinder bottom plug was improperly gapped. Improper hardware was used to secure the fuel injector lines between the flow divider and the cylinders. The exhaust gasket on cylinder No. 6 showed signs of failure and leakage. The No. 3 exhaust valve would not seat properly. The fuel servo screen appeared new with a new gasket and no contamination noted. Fuel from the servo supply line was clean, but fuel coming out of the servo was orange in color. Cold engine compression test results for the left engine (max 80 psi) were 58/13/20/12/60/66 psi.
In the right engine, piston faces exhibited signs of fouling, carbon deposits, and erosion on the edges of the valve recesses. All spark plugs were improperly torqued. The No. 6 cylinder exhaust gasket was blown. Cylinders 2 and 3 were lead fouled with large chunks of debris lodged between the case and insulator. The fuel servo screen contained contamination and was corroded. The fuel flow divider contained two pieces of corroded debris in the plunger orifice; the pieces were almost the size of a BB. Corrosion debris was found in the 45-degree inlet fitting on the fuel flow divider. Standing oil was found in the No. 2 cylinder, with its bottom spark plug oil soaked. The throttle cable was improperly installed, exhibited excessive bends, and the swaged end guide was found separated from the throttle body. Cold engine compression test results for the right engine (max 80 psi) were 60/72/25/45/22/60 psi.