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Aviation Accident

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NTSB Identification: CEN17FA331
14 CFR Part 91: General Aviation
Accident occurred Monday, August 28, 2017 in Ellabell, GA
Probable Cause Approval Date: 11/06/2019
Aircraft: BEECH A36, registration: N87RY
Injuries: 3 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The commercial pilot was conducting a business flight; while climbing out after departure, the pilot declared an emergency and reported a loss of engine power to air traffic control. The controller provided vectors to a private airport about 6.5 nautical miles (nm) behind the airplane and stayed in communication with the pilot until communications and radar were lost. The airplane then began a wide turn to head back to the private airport, traveling about 6.3 nm during the turn. The airplane impacted trees and terrain about 6 miles from the private airport.

The airplane's maintenance records showed that all six engine cylinders were replaced about 15 months and 227 engine hours before the accident. Postaccident examination of the engine revealed that four of the eight nuts that retained the No. 1 cylinder and one nut that retained the No. 2 cylinder were loose during disassembly, and no breakout torque reading could be measured. Two of the loose nuts on the No. 1 cylinder were on the through-studs that provided clamping force on the No.1 main crankshaft bearing. Disassembly of the crankcase revealed that the No. 1 main bearing had shifted to the rear of the crankcase, which obstructed the oil flow to the No. 1 main bearing and the No. 1 connecting rod bearing.

Given the available evidence, it is likely that, during replacement of the engine cylinders, improper torque of the cylinder hold-down bolts and through-studs resulted in an insufficient clamping torque, which allowed the No. 1 main bearing to shift. This shift precluded oil from reaching the No. 1 main bearing and the No. 1 connecting rod bearing, which led to the failure of the connecting rod during the accident flight.

The emergency obstruction video map (EOVM) used by the controller handling the flight did not depict another private airport, which was closer (3.4 nm) and was in more of a direct path from the airplane's heading and position at the time of the emergency. The Federal Aviation Administration order governing EOVM displays stated that they must contain satellite airports and other airports that could serve in an emergency. The order also noted that the information depicted on the EOVM should be restricted to only the information that is "absolutely essential." On the basis of the distance that the airplane was able to glide after the pilot declared the emergency (6.3 nm), the airplane should have been able to reach the closer airport that was ahead of it. Thus, the omission of this airport on the controller's EOVM resulted in the pilot attempting, at the direction of the controller, to reach an airport that was beyond the airplane's gliding distance.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
  • The total loss of engine power due to oil starvation to the No. 1 connecting rod, which resulted from the improper torque of the No. 1 cylinder hold-down bolts and through-studs at the time of the cylinder's installation, which resulted in the failure of the connecting rod due to oil starvation. Contributing to the accident was the omission, from the air traffic control emergency obstruction video map, of a closer alternate airport for the emergency landing.