MIA98LA037

While in cruise flight, the engine began making banging and hissing sounds, emitting white smoke, and steadily losing power. The pilot requested vectors from ATC to the nearest airport, Dobbins ARB, but couldn't stretch his glide, and made a forced landing onto a construction site. The airplane came to a stop in trees and was destroyed. An NTSB-supervised teardown inspection revealed failure of the oil cooler core resulting in oil starvation.

On December 1, 1997, about 1105 eastern standard time, a Cessna FR-172J, N14493, registered to The Flight School of Gwinnett, Inc., operating as a 14 CFR Part 91 ferry flight, experienced a loss of engine power during cruise flight about 10 miles southwest of Dobbins Air Reserve Base, Georgia. Visual meteorological conditions prevailed and an instrument flight rules flight plan was filed. The aircraft was destroyed, and the commercial pilot sustained minor injuries. The flight originated from Gwinnett County/Briscoe Field, Lawrenceville, Georgia, about 20 minutes before the accident.

The pilot stated while in cruise flight at an altitude of 6,000 feet, under the control of Atlanta Approach Control, the engine tachometer suddenly increased about 100 rpm and as he adjusted power, he experienced "hissing" and "banging" from the engine. Simultaneously, he experienced gradual rpm decay, cowling vibration, oil on the windscreen, and white smoke from under the cowl and in the cockpit. Upon notification of the problem, ATC gave the pilot an immediate vector toward Dobbins ARB. The pilot realized he could not make the airfield, and made a forced landing to a graded, terraced construction site, and came to rest in a wooded area.

NTSB supervised teardown inspection of the engine revealed a rupture in the core of the oil-cooler, indication of no oil from dipstick, heavily scored and burned connecting-rod-to-crankshaft bearing surfaces and scored and burned crankshaft journals. The No. 2 connecting rod cap had separated and the rod was protruding through a hole in the upper crankcase. The No. 1 connecting rod was broken at the crankshaft journal. Parts of the broken No. 1 connecting rod end, the No. 2 rod cap, a pushrod tappet assembly, and other metal fragments were found in the bottom of the crankcase.

FAA supervised engine manufacturer's inspection revealed the oil-cooler leak as "severe", and "..would empty the engine oil supply in a short period of time." No previous repair to the oil-cooler was visible, and no reason for the core failure could be determined.

From the engine logbooks, it was determined that on September 14, 1988, the oil-cooler was installed as a reconditioned component. At the time of the accident, using tachometer readings, the oil-cooler had accumulated about 422 hours.