New Orleans, LA, USA
N8440N
PIPER PA 28-161
The pilot/owner reported that, while on final approach to the destination airport, the engine experienced a total loss of power. The pilot was unable to restart the engine, and the airplane was unable to glide to the runway, so the pilot subsequently ditched the airplane into a lake. The pilot evacuated the airplane and swam to shore; the airplane sank into the lake but was subsequently recovered. A postaccident examination of the engine's crankshaft gear, retaining bolt, and lockplate revealed that the retaining bolt had fractured; the fracture surfaces and the fine ratchet marks in the initiation area were consistent with fatigue crack propagation. Defined fretting wear scars were noted partially around the circumference of the bolt through-hole. The lockplate exhibited areas of fretting wear and polishing wear scars. The lockplate's retention tab was in the "open" position and did not exhibit typical mechanical deformation associated with bending to the "closed" position, which indicates that the lockplate was not installed properly. The engine manufacturer had issued a service bulletin (SB) that outlined additional maintenance actions that should be taken if an engine experienced a propeller strike. Subsequently, the Federal Aviation Administration issued an airworthiness directive (AD) that made compliance with the SB mandatory. During the course of the investigation, the pilot reported that the engine had experienced a propeller strike days before the accident flight. He stated that he was unaware of the AD, so it was not accomplished after the propeller strike. It is likely that the crankshaft gear retaining bolt tension was loosened when the propeller strike occurred and that the improperly installed lockplate allowed the bolt to lose its clamping force. The loose bolt became fatigued and subsequently failed during the accident flight.
On August 22, 2014, at 1554 central daylight time, a Piper PA 28-161 airplane, N8440N, ditched into Lake Pontchartrain near the Lakefront Airport (NEW), New Orleans, Louisiana. The pilot, who was the sole occupant, was not injured. The airplane sustained substantial damage. The airplane was registered to and operated by a private individual under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed at the time of the accident and the flight was operated on a visual flight rules flight plan. The airplane departed the Jack Brooks Regional Airport (BPT), Beaumont/Port Arthur, Texas, at 1353 and was enroute to NEW. The pilot stated that he departed BPT with about 17 gallons of fuel in the left tank and 24 gallons in the right tank. He departed with the right fuel tank selected and switched fuel tanks every 30 minutes during the flight. The flight was uneventful until the descent from 1,500 feet above ground level (agl) when the engine experienced a total loss of power. He attempted to restart the engine multiple times without success. He was cleared to land on runway 09, but the airplane was unable to glide to the runway. The pilot ditched the airplane into Lake Pontchartrain a quarter mile west of runway 09's threshold. The pilot egressed from the airplane and swam to shore. The airplane sank into the lake. The responding Federal Aviation Administration (FAA) inspector stated that the airplane was removed from the lake and placed inverted on a barge. He observed fuel leaking from the right wing. A postaccident examination revealed that the engine's crankshaft gear retaining bolt was separated at the head. The lockplate did not appear to be bent or out of place. The crankshaft gear, gear retaining bolt, and associated lockplate were sent to the NTSB Materials Laboratory, in Washington, D.C. for examination. The exam revealed that the bolt fractured at the fillet radius between the shank and the head. Examination of the fracture surfaces with a field emission scanning electron microscope (FE-SEM) revealed very fine fatigue striation features within the fracture surfaces. The inner surfaces of the counterbore on the crankshaft gear exhibited areas of fretting wear and polishing wear scars. A defined fretting wear scar was noted partially around the circumference of the bolt through-hole. The lockplate exhibited areas of fretting wear and polishing wear scars. The lockplate's retention tab was in the open position and did not exhibit typical mechanical deformation associated with bending to the closed position (e.g. 90° position). Defined circumferential fretting wear scars were noted partially around the circumference of the bolt through-hole. According to Lycoming Service Bulletin (SB) 375 Revision C, January 30, 2003, "Damage to the crankshaft gear and the counterbored recess in the rear of the crankshaft, as well as badly worn or broken gear alignment dowels are the result of improper assembly techniques or the reuse of worn or damaged parts during reassembly. Since a failure of the gear or the gear attaching parts would result in complete engine stoppage, the proper inspection and reassembly of these parts is very important. The procedures described in the following steps are mandatory." The Service Bulletin was to be complied with during an engine overhaul, whenever crankshaft gear removal is required or after a propeller strike. The FAA issued Airworthiness Directive (AD) 2004-10-14 on June 28, 2004. The AD made the Lycoming Service Bulletin mandatory and compliance with the AD is required before further flight if an engine experiences a propeller strike. Initially, the pilot reported that he was unaware of any propeller strikes in the past. During a subsequent conversation on December 11, 2014, between the pilot and an FAA inspector, the pilot reported that a propeller strike had occurred days before the accident flight. The pilot stated that he was unaware of the corresponding AD and so the AD was never completed after the propeller strike.
The in-flight fatigue failure of the crankshaft gear retaining bolt, which resulted in a total loss of engine power. Contributing to the accident were the pilot/owner’s failure to maintain the airplane in accordance with an airworthiness directive following a propeller strike and the improper installation of the lockplate.
Source: NTSB Aviation Accident Database
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