LAX07LA004

Upon experiencing a total loss of engine power during cruise flight, the pilot made a forced landing during which the airplane overran the runway's departure end and impacted a fence. The pilot reported that during the flight she "heard an abnormal noise coming from the engine - a loud knocking sound. Within just a few seconds, the engine exploded and a rush of oil from the engine compartment flooded the wind screen, obscuring about 90 percent of the forward field of view....The cabin started to fill with smoke from burnt oil," and the propeller stopped rotating. The pilot force landed on a 2,000-foot-long airstrip. Upon exiting the airplane the pilot observed that the top portion of the engine's case was punctured. The pilot had purchased the 1978 model airplane earlier during 2006, and she had possession of its maintenance records. The records indicated that the engine received three (field) overhauls in 1980, 1991, and in 1994. By the accident date, the engine's total time and time since last overhaul was 5,538 and 950 hours, respectively. Examination of the engine found that it had sustained an internal catastrophic mechanical failure, which resulted in a breach of the crankcase at the forward top section. The oil lines were found secure at their respective engine fittings, the crankshaft and respective connecting rods exhibited severe heat distress consistent with lubrication deprivation. The number 1, 2 and 4 connecting rods were displaced from their respective journals. The number 3 connecting rod remained on the journal, which exhibited severe heat distress. The crankshaft and camshaft remained intact. No anomalies were found with the accessory components and gears, or with the lubricating system. The specific event leading to the lubrication deprivation and heat distress was not identified.

History of flight

On October 8, 2006, about 1316 Pacific daylight time, a Grumman American AA-5B, N39ER, experienced a total loss of engine power while cruising. The pilot made a forced landing on the Kistler airstrip, overran its departure end, and impacted a fence. The Kistler airstrip is privately owned, and it is located about 15 nautical miles northeast of Oakdale, California. The airplane was substantially damaged. Neither the private pilot nor the student pilot rated passenger (who are joint owners of the airplane) was injured during the personal flight. Visual meteorological conditions prevailed, and no flight plan had been filed for the intended flight to San Carlos, California. The flight was performed under the provisions of 14 CFR Part 91, and it originated from Groveland, California, about 1245.

In pertinent part, the pilot reported to the National Transportation Safety Board investigator that the 1978 model airplane had received an inspection prior to her purchasing it earlier during 2006. During the accident flight, no evidence of any mechanical malfunction was apparent until seconds after leveling off at 6,500 feet mean sea level (msl). In the pilot's completed "Pilot/Operator Aircraft Accident/Incident Report" she made the following statement regarding the sequence of events that followed:

"At approximately 12 nm from Oakdale, we heard an abnormal noise coming from the engine - a loud knocking sound. Within just a few seconds, the engine exploded and a rush of oil from the engine compartment flooded the wind screen, obscuring about 90 percent of the forward field of view....The cabin started to fill with smoke from burnt oil; however, there were no flames at any time. The engine operated with some residual power down to about 3,000 feet, when it finally stopped rotating....With smoke in the cabin and coming in a little high, we went off the end of the runway and followed a dirt road around 20 degrees to the right for about 200 yards, broke through a gate and came to rest approximately 50 feet beyond the gate."

The pilot landed on the 2,000-foot-long dirt airstrip, elevation 1,025 feet msl, in a northwesterly direction. The wind was light and variable. After exiting the airplane the pilot looked at the top portion of the engine's case. It was punctured.

Engine overhaul and maintenance history

Engine logbook records indicate that operation of the accident engine commenced in July 1978. The engine received its first major overhaul on May 20, 1980. Upon completion of this first overhaul, the engine's total time was recorded as 2,190 hours.

On December 8, 1991, the engine received its second field overhaul at an approximate total time of 4,353 hours (2,163 hours since first overhaul). A notation in the records indicates that, in part, during this overhaul the crankcase was repaired, and factory new cylinders were installed.

On July 28, 1994, the engine received its third overhaul at an approximate total time of 4,639 hours (286 hours since last field overhaul).

The engine's last inspection was accomplished on June 21, 2006, at an approximate total time of 5,538 hours (899 hours since last overhaul). In part, during the inspection no metal was found in the oil, the spark plugs were replaced, and compression in all cylinders was at or above 73/80. The engine was test run and was found "satisfactory." By the accident date, the engine's total time and time since last field overhaul was about 5,589 and 950 hours, respectively.

Engine examination

Under the direction and supervision of the Safety Board investigator, the Lycoming Engine participant examined the engine. In pertinent part, the following observations were made:

1. The engine remained attached to the airframe by the engine mount. The engine had sustained catastrophic mechanical malfunction, which resulted in a breach of the crankcase at the forward top section. The metal fixed pitch propeller remained attached at the crankshaft flange.

2. The engine compartment oil lines were found secure at their respective fittings on the engine and oil cooler. The oil filter remained secure and properly safety wired. The sump drain (quick drain) operated normally. The oil sump remained intact and exhibited no impact damage. The crankshaft nose seal remained in place.

3. The crankshaft and respective connecting rods exhibited severe heat distress consistent with lubrication deprivation. The number 1, 2, and 4 connecting rods were displaced from there respective journals. The number 3 connecting rod remained on the journal, which exhibited severe heat distress. The crankshaft and camshaft remained intact.

4. The accessory case was removed. The accessory gears including the crankshaft gear, bolt, and dowel were intact, and remained undamaged by any preimpact malfunction. The oil pump remained intact and was free to hand rotate at the drive. The oil pressure galley plugs remained in place.

5. The accessory pad gaskets at the various mounting pads subjected to pressurized oil were examined and found to be properly secured and exhibited no evidence of leakage.

6. The oil cooler and oil lines were submerged in water and leak tested utilizing a remote air source. There were no leaks observed at the oil cooler core or hoses during the testing.

7. The exhaust system remained free of oil residue.

The precipitating event leading to the inadequate lubrication and heat distress to rotating components was not identified.