The pilot, with two passengers, was conducting a trip in a Piper Lance from Archerfield to Moorabbin and return. During the engine run-up checks prior to departure from Archerfield, the pilot noted that the aircraft engine ran roughly, however increasing the engine RPM and leaning the mixture cleared the problem. During the flight to Moorabbin, he heard a slight miss in the engine note. On arrival at Moorabbin, the pilot noticed some oil on the outside of the engine cowl.
The pilot intended to depart from Moorabbin for the return flight to Archerfield two days before the day of the accident. On that day, the aircraft required the usual leaning to clear the engine roughness during taxi. Shortly after take-off, after the pilot had reduced the power settings to normal climb power, he noticed the vacuum gauge indicated zero. At about the same time, the engine began to run roughly and the pilot elected to return to Moorabbin. After landing, he removed the engine cowling, and noticed a significant amount of oil on the engine. The pilot then asked an engineer to investigate the problems. The engineer determined that there was a substantial oil leak from one of the top crank case bolts, and that the engine had lost approximately 3 L of oil. After resealing the bolt, refilling the engine with oil and replacing the vacuum pump, the engineer conducted a further engine run, during which there was no evidence of rough running.
History of the flight
Two days later, on the day of the accident, the pilot again attempted to depart Moorabbin for Archerfield. The pilot stated that shortly after takeoff, as the aircraft climbed through approximately 1,600 ft, the engine appeared to cut out but then immediately operated normally again. Soon afterwards, the engine lost all power.
The pilot conducted a forced landing onto a stretch of road that was clear of vehicles. The aircraft was substantially damaged during the accident sequence when it collided with various obstacles, including powerlines, poles, a tree and a fence. The occupants of the aircraft were not injured, but were unable to open the doors. While exiting the aircraft through broken windows, both passengers sustained minor injuries.
Damage to the propeller indicated that the engine was rotating on impact, but not under power. A subsequent examination of the engine established that the magneto timing was between approximately 20 and 25 degrees after top dead centre. The correct timing for the engine was 25 degrees before top dead centre. The magneto gear was missing three teeth. The idler gear that drove the magneto gear and the engine-driven fuel pump, was no longer secured in either the accessory housing or the crankcase. At the accessory housing end, the mounting boss had cracked away from the housing and most of the fracture surfaces had worn smooth. At the crankcase end, the mounting bore had been substantially worn, and remnants of a bush remained in the bore. During normal operations, both idler gear mounts were subject to significant side loads from the engine-driven fuel pump drive cam.
Further examination of the idler gear shaft boss and bore established that the crankcase idler gear shaft bore had been repaired. This repair involved drilling out the bore and subsequent installation of a bush. The bush had not been secured to the crankcase bore and the metal used to manufacture the bush was commercially pure aluminium, a metal with low resistance to plastic deformation.
History of the aircraft
The aircraft was exported to Australia from the United States in early 1989. The Lycoming IO-540 engine installed in the aircraft at the time of the accident had been overhauled in 1988 in the USA, just prior to the aircraft being exported to Australia. According to the aircraft logbooks, in December 1989 the Australian company that imported the aircraft replaced the crankcase with an overhauled crankcase supplied by a USA crankcase repair company. There was no record of the reason it was replaced.
The USA company that supplied the overhauled crankcase had detailed its requirements for idler gear shaft bore repairs in its Federal Aviation Administration approved repair scheme. The repair involved drilling out the bore to a diameter of 0.813 inches, installing a bush to an interference fit and welding the bush to the crankcase. The repair scheme did not specify the material from which the bush should be manufactured.
The engine manufacturer issued a number of service instructions related to bushed repairs of idler gear shaft bores. The most recent of these, number 1417 issued 1 October 1982, required that the bore be drilled out to a diameter of 0.812 to 0.813 inches and that the outside diameter of the bush be machined to 0.814 to 0.815 inches. The instruction also stipulated that the bush be fixed to the crankcase by dowels and that the bush should be manufactured from AMS 4118 aluminium alloy. AMS 4118 referred to an alloy of aluminium and 3.5% magnesium. This alloy had a higher resistance to plastic deformation than commercially pure aluminium.
The crankcase idler gear shaft bore repair in the accident aircraft had not been conducted in accordance with either the Lycoming approved repair scheme or the US crankcase overhaul company repair scheme.
At the time of the accident, the engine had approximately 114 hours to run before it was due for overhaul. The aircraft was being maintained using the Civil Aviation Safety Authority Maintenance Schedule detailed in Schedule 5 to the Civil Aviation Regulations 1988. Section 2 (4)(c)(ii) of that schedule required that if a cartridge full-flow oil filter was fitted, that maintenance personnel should remove, open and inspect the filter at each periodic inspection. Because oil filters remove particulate contamination, such as metal, from engine oil, internal inspections of oil filters can provide an indication of the engine's condition.
The aircraft's engine was equipped with a cartridge full-flow oil filter, and periodic inspections were being conducted at 100 hourly intervals. The engine manufacturer recommended that the oil and oil filter be changed at 50 hourly intervals. The aircraft documentation indicated that the aircraft had been operating for approximately 83 hours since the last periodic inspection. There was no record that the oil and oil filter had been changed since the periodic inspection.
At the time of the accident, the pilot held a Private Pilot's Licence and had accumulated approximately 270 hours of flying experience. He had completed approximately 9 hours in the accident aircraft, his only experience in Piper PA32R-300 aircraft.
The pilot's training on the aircraft type involved two check flights, conducted a week before the accident. The aircraft engine ran roughly during taxi, however increasing the engine RPM and leaning the mixture cleared the problem. The pilot was told that the engine used a lot of oil and that the rough running and oil use related to the age of the engine.
The investigation determined that an improper crankcase idler gear shaft bore repair resulted in increased vibration levels and excessive wearing of the accessory gears. These conditions led to various failures in the accessory drivetrain and the eventual failure of the engine. It was inappropriate to repair the crankcase idler gear shaft bore with a bush manufactured from a material with low resistance to plastic deformation, as the bush was subject to significant side loads.
It appeared that the personnel who operated the aircraft did not recognise that the problems they were experiencing were more than merely those of a worn engine. Had a 50-hourly oil filter inspection been carried out, as recommended by the manufacturer, it would have provided an opportunity for the problems in the accessory area to be identified prior to the engine failure.
|Date:||27 January 1999||Investigation status:||Completed|
|Time:||0914 hours ESuT|
|Location:||9 km N Moorabbin, Aero.|
|State:||Victoria||Occurrence type:||Forced/precautionary landing|
|Release date:||30 April 2001|
|Report status:||Final||Occurrence category:||Accident|
|Highest injury level:||Minor|
|Aircraft manufacturer||Piper Aircraft Corp|
|Type of operation||Private|
|Damage to aircraft||Destroyed|
|Departure point||Moorabbin, VIC|
|Departure time||0901 hours ESuT|
|Role||Class of licence||Hours on type||Hours total|