The pilot/owner reported that, while on final approach to the airport in New Orleans, the Piper PA28-161’s engine experienced a total loss of power.
He was unable to restart the engine, and the airplane was unable to glide to the runway, so he 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 post-accident 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 FAA 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. 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.
The NTSB determined the probable cause as 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.
NTSB Identification: CEN14LA449
This August 2014 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
It appears the engine was operating normal until the prop strike. Any time there is a prop strike, ( and this one was significant ) not just hitting a chock or the like, but a real prop strike where the prop comes to an abrupt stop. The owner should seek professional help and let him decide what to do, and not make the decision yourself. This is very dangerous to say the least. There are so many different variables and they are all very dangerous. Bottom line, If you can’t afford to fly safely you can’t afford to fly. No second guessing. Sorry !!
Looked it up
Quote
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.
the root cause here was the improber installation of the lock plate not the propstrike
Dunno that I totally agree. You might say that the problem was really improper maintenance by the owner who wasn’t keeping up on ADs that affected his engine. Even an SB, though not required for Part 91, should be considered by owners as important information about the machine. Whether to comply with an SB… that’s a risk preference/risk avoidance decision. The materials lab report after the accident shows very clearly the reason for the AD (and the previous SB) http://dms.ntsb.gov/public/57000-57499/57282/572919.pdf In this case the AD was issued in June 25, 2004… 10 years prior to the accident. http://dms.ntsb.gov/public/57000-57499/57282/572924.pdf His A&P certified AD compliance TWICE! This occurred first in 2010 and again in 2012 after an engine rebuild. http://dms.ntsb.gov/public/57000-57499/57282/572927.pdf
Regardless, prop strikes have long been known as contributory to crank shaft fractures. IMHO, the owner failed to exercise reasonable care following the prop strike. The mechanic… maybe needs a class in how to search ADs.
Me thinks that if I had a prop strike I would exercise due diligence to find out everything I could from the manufacturer related to post strike actions that should taken with respect to the engine before I climbed back into the air with it. And don’t trust Joe Schmuckatella the local mechanic to know everything either.
Exactly
The owner/operator is responsible for aircraft airworthiness. The A&P Mechanic or Repair Station should have verified the AD before returning the aircraft to service. But was the AD compliance date “immediately” before further flight or at next annual or even next engine overhaul?
It is the pilots’ responsibility to know about all airworthiness requirements including ADs.
The A&P and repair stations should do the research and at least advise the owner that there is an AD or service bulletin, but they did not insist.
Prop strikes often are cleared by checking runout on a flange of the crankshaft without an engine tear down. Insurance companies often won’t pay for a tear down unless damage is found, so tear downs often are not done.
Glad the pilot knew how to swim.