N327BKSmith AEROSTAR 601 · 1973

On July 20, 2018, about 1430 central daylight time, a Piper PA60 Aerostar airplane, 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 registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91 as a maintenance test flight. Visual meteorological conditions prevailed at the time of the accident and no flight plan had been filed. The local flight was departing at the time of the accident.

A review of the air traffic control recording revealed that the pilot requested to takeoff from runway 31 and fly one time around the traffic pattern for a maintenance check. The air traffic controller stated that the airplane dropped below the tree line after takeoff and was unable to reach the pilot on the radio.

After the accident the pilot stated that he completed a preflight inspection about 1400, then boarded the airplane and started both engines. While holding short of runway 31, he performed a pre-takeoff check of the airplane including a run-up for each engine with no anomalies noted. During the takeoff roll he advanced the throttles to takeoff power, then rotated. Shortly after rotation he noticed the right engine was not producing full power and the engine speed was decreasing. With no remaining runway available 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 (figure 1) about 1 mile northwest of the departure end of runway 31.

Figure 1 – Accident airplane

In a postaccident statement, the mechanic who maintained the airplane stated 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. The fuel line was reconnected then checked the fuel flow by measuring the fuel 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 completed the same procedures to flush the fuel system and flow check the fuel nozzles for the right engine. 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 mechanic reported that the pilot stated he was going to "take it around the patch." The pilot ordered fuel from the FBO and proceeded with his preflight.

The mechanic provided copies of the airplane's recent maintenance records. The most recent maintenance entry was completed by the mechanic on June 18, 2018, which involved reinstallation of an overhauled fuel injection servo and the fuel injector nozzles were cleaned; an engine ground run was completed with no discrepancies noted with the left engine. The records revealed that the airplane had accumulated 31.4 hours hours since July 2014, 3.6 hours since October 2017, and 10.8 hours since September 2016. During that time an annual inspection was completed each year by the same mechanic.

A postaccident examination of the engines and fuel system was completed by a third-party mechanic under the supervision of a Federal Aviation Administration (FAA) inspector. The examination revealed no apparent external damage to either engine case or accessories. The fuel supply lines to the fuel servos on both engines appeared clean and exhibited a blue tint consistent with 100 low lead aviation fuel. The amount of fuel retrieved from the fuel supply line and fuel servo corresponding to each engine was not measured but was estimated that less than 5 milliliters of fuel was drained from each fuel servo supply line. 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 revealed that the left engine 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 the electrode was fouled. The spark plugs corresponding to cylinder Nos. 2, 4, and 6 were under torqued. The No. 3 cylinder top spark plug was fouled and the bottom spark 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. A borescope examination showed that 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; however, fuel coming out of the servo was orange in color. A cold engine compression test was performed for each cylinder with a max pressure of 80 psi; the left engine compression values were 58/13/20/12/60/66 psi.

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. No. 6 cylinder exhaust gasket was blown. Cylinder Nos. 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 2 pieces of corroded debris in the plunger orifice; the pieces of debris 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 the 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. A cold engine compression test was performed for each cylinder with a max pressure of 80 psi; the right engine compression values were 60/72/25/45/22/60 psi.