19980318008029A

On March 18, 1998, at 1445 hours pacific standard time, a callair A-9, N7211V, lost engine power while towing a glider at the Thermal, California, airport. The aircraft collided with ground obstructions during the subsequent off airport forced landing. The aircraft sustained substantial damage and the commerical pilot, the sole occupant was not injured. The glider returned to the airport and landed with no damage. Visual meteorological conditions prevailed and no flight plan was filed. The flight originated from Thermal at 1440 as a glider tow operation. The pilot reported to a federal aviation administration inspector from the riverside flight standards district office that he tookoff and climbed to 1500 feet. He reported that the rate of climb seemed "sluggish" and he noticed that the tachometer was falling through 2200 RPM, whereas it should have been at 2400-2500 RPM. The pilot further stated that the engine was still running smoothly with full power and mixture rull rich. He then waved the glider off and initiated a 180 degree turn. The engine subsequently quit, with the tachometer reading 1900 RPM. The pilot switched the fuel tanks from the left to right with no response fromthe engine. He landed in an open field, damaging the firewall and powerplant. The glider pilot on tow stated that after he was released, he noticed smoke trailing the aircraft on its descent. According to the pilot/operator report, the engine had 1586 hours since overhaul at the time of the accident. The safety board conducted an examination of the engine on may 6, 1998. Initial examination revealed that the crankcase upper surface near the number three cylinder was cracked and displace outward. No other ecternal damage was observed. There was no evidence of fire damage. The number three and four cylinders were removed and examined. The connecting rods for those cylinder were found detached from their respective crankshaft journals. The crankshaft journals and respective connecting rods displayed signatures consistent with heat distress. The connecting rod bolts and nuts for the number three cylinder were found attached to the rod assembly. The number four cylinder connecting rod end pieces were recovered. One of the bolts was found intact in the remaining piece of rod cap and the remaining bolt was seperated. The seperated bolt displayed an appearance consistent with seperation during heat distress. Extruded bearing material was found in the sump. The oil suction screen and full flow oil filter were removed and examined. There were no metal particles found in either of the filters. The oil cooler thermostatic by pas valve(vernatherm) was removed and found intact. Metal contamination was limited to the confines of the oil sump. The accessory housing was removed to gain access to the oil pump assembly. Initial examination of the accessory gears revealed damaged to the oil pump drive coupling at the crankshaft gear. The coupling displayed signatures consistent with heat distress. The oil pump drive at the oil pump would not rotate. The oil pump asssembly was removed from the mounting pad and examined. Engine oil flowed freely from the oil pump assembly as it was removed from the mounting pad. The oil pump gears were lubricated and appeared undamaged. The oil pump housing and mounting pad were free of any rotational scoring and did not display evidence of oil stravatiaon or metal contamination. The oil pump dirve shaft was removed from the oil pump housing and did not display any signs of overheating of lubrication starvation where the shaft rotates inside the housing. The crankshaft gear was a Lycoming part number 13S19648 and is the part number for the Lycoming 1P-540 series engines. The engine in the accident aircraft is a Lycoming O-540-B2B5 and the crankshaft gear part number for this engine is 13S19647. (-23) on March 18, 1998, at approximately 1445 PST, daniel b. pavao departed from Thermal Airport in callair A-9, N7211V, towing a glider for the purpose of glider passenger rides being offered that day. Mr. Pavao took off west, climbed to 1500 feet and noticed the tachometer falling through 2200 RPM whereas it should have been 2400-2500 RPM. The engine was running smoothly with full power and mixture rich. Mr. Pavao waved the glider off, started a 180 degree turn and noticed the tachometer at 1900, then the engine quit. Mr. Pavao estimated his descent at 1500 feet/min., he switched fuel tanks to left to right but nothing happened. Mr. Pavao stated that he picked a spot in a field and landed with full flaps. The glider pilot on tow stated that he noticed smoke coming from the aircraft. Upon further investigation a large crack was discovered in the upper left crankcase. This accident inve stigation is now closed.