Cessna 172 Crash After Engine Failure

This Cessna 172 had a student pilot and an instructor in it. After takeoff they noticed that oil pressure was low and oil temperature was rising. They attemped an emergency landing but ended up hitting some power lines. The NTSB summarized report is below, the last paragraph tells the cause of the accident.

NTSB Identification: MIA05LA046.
Accident occurred Tuesday, January 11, 2005 in Orlando, FL
Aircraft: Cessna 172M, registration: N9336H
Injuries: 1 Fatal, 1 Serious.

The airplane experienced a total loss of engine power and collided with wires and a power line pole while descending for a forced landing. The pilot-rated student reported that while returning to the departure airport (KORL), he noted a smell of something burning which triggered him to look at the engine gauges; he noted "...that we had no oil pressure." No oil was noted by the student on the windscreen or on the sides of the airplane. The flight continued towards KORL, and 5 minutes 3 seconds after an occupant first advised the controller of having no oil pressure, an occupant advised the controller that the engine quit. The CFI took the controls and maneuvered the airplane towards a nearby golf course for a forced landing. He made several s-turns to lose altitude with full flaps extended, but while maneuvering to possibly land on a nearby road, the airplane collided with power lines, then a power pole. Postaccident, an oil film was noted on the exterior surface of the fuselage bottom skin, and in the engine compartment area on the aft side of the baffling. During postaccident testing, a leak was noted from a flexible hose near the oil cooler end; the cure date of the hose was the 3rd quarter 1981. Ten ounces of oil were drained from the engine, which exhibited internal evidence of oil exhaustion with resulting failure of the No. 2 cylinder connecting rod cap and bolt. The engine was overhauled last in 2001. The engine manufacturer recommends replacement of oil hoses at normal engine overhaul. A note in the airplane maintenance manual indicates that rubber engine compartment hoses are to be replaced every 5 years or at engine overhaul, whichever occurs first. Examination of the hose by the NTSB Materials Laboratory revealed a .7 inch long crack located approximately 4.25 inches from the oil cooler adapter end. The crack was oriented "slightly away from the longitudinal axis." Bench binocular microscope (BBM) examination of the hose revealed the woven fiber strands were missing in the cracked area. Scanning electron microscope (SEM) and BBM examination of the face of the crack revealed the thickness of the outer layer of rubber was reduced, and a portion of the reduced outer layer of rubber that was located midspan of the crack was missing. Additionally, the fiber strands that were located between the inner and outer rubber layers were fractured. The inner layer of rubber was found to contain fracture lines that emanated from the outer surface layer in an area that contained an impression of fiber strands from the fibers between the 2 rubber layers. The lines on the surface crack indicated that cracking of the inner layer propagated towards the inner diameter of the hose; cracking on a flat plane was noted to within .01 inch of the inside surface of the hose. Examination of other areas of the inside surface of the hose revealed extensive longitudinal cracks. Additionally, the exterior surface of the contained abrasion damage in three areas other than the cracked area of the hose; the abrasion damage did not extend through the outer layer of rubber.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:

The failure of the CFI to initiate a precautionary landing after noticing zero oil pressure with corresponding oil temperature increase, resulting in total loss of engine power due to oil exhaustion. A contributing factor in the accident was the failure of company maintenance personnel to replace the flexible oil cooler hoses during engine installation following overhaul, as recommended by the engine manufacturer.

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