Accident Overview
On December 19, 2013, at 2351 eastern standard time, a Cessna 210N, registration N5307A, was substantially damaged during a forced landing after a total loss of engine power while on approach to Tampa International Airport (TPA), Tampa, Florida. The commercial pilot was seriously injured. Visual meteorological conditions prevailed, and the airplane was operating on an instrument flight rules flight plan. The flight had originated from Valdosta Regional Airport (VLD) at about 2307 and was destined for TPA. The on-demand air cargo flight was conducted under Title 14 Code of Federal Regulations (CFR) Part 135.
Accident Sequence
According to air traffic control (ATC) radar and voice communications, the pilot was cleared to land on runway 1R at 2345. At 2346, the pilot advised ATC that he needed to land on runway 10 and that the airplane's engine had "lost oil pressure." ATC advised that runway 10 was closed for construction and offered runway 19R. At 2347, when asked if emergency equipment was required, the pilot initially declined, stating the engine was "running a little rough here, I should be able to make it though." About 30 seconds later, the pilot requested emergency response equipment. No further transmissions were received.
A Tampa Police Department helicopter observed the airplane as it approached and impacted a berm short of runway 19R on airport property. The helicopter landed adjacent to the accident site, and one crewmember successfully extracted the pilot from the wreckage.
Pilot Information
The pilot held a commercial pilot certificate with ratings for airplane single and multi-engine land, as well as instrument airplane. The operator reported that he had accumulated 6,912 total hours of flight experience, 412 hours of which were in the accident airplane make and model. The pilot's most recent CFR 135 proficiency check was completed on a flight immediately preceding the accident flight.
Aircraft and Engine Details
The airplane was manufactured in 1979 and equipped with a Continental Motors IO-520-L reciprocating engine rated at 285 hp. The engine was installed following a rebuild by Continental Motors on December 18, 2009. The airplane's most recent 100-hour inspection was completed on November 26, 2013. At that time, the number 1 cylinder was removed to replace a broken exhaust valve, and the exhaust valve seats of cylinders number 1, 2, and 3 were lapped. The engine oil filter was changed, the old filter element examined, the oil drained, and the engine serviced with 11 quarts of oil. At the inspection, the engine had accumulated 1,579 total hours since installation in 2009. The maintenance logs did not detail further maintenance, and at the accident the airplane had accumulated 41 additional flight hours since the inspection. The operator's operations specifications listed the engine model's overhaul time-in-service interval as 1,700 hours.
Post-Accident Examination
The airframe was examined at the accident site under FAA supervision. The left wing tip, engine, and lower forward fuselage displayed considerable compression-type damage. Engine oil residue was observed on the fractured windscreen and vertical stabilizer. Flight control continuity was established. The elevator trim actuator extension corresponded to a 10-degree tab trailing edge down position. The flaps were between 0 and 10 degrees of extension, with the flap switch handle in the 20-degree position. Fuel was found in both fuel tanks; the fuel selector valve was positioned to the left tank, and the fuel boost pump switch was ON. The landing gear selector handle was DOWN, and the main landing gear was down and locked. The nose landing gear had separated during impact.
The engine remained attached to the fuselage; the top of the crankcase was breached near cylinders 2 and 4. The piston pin and connecting rod of the number 4 cylinder were recovered from inside the cowling. The engine was sent to the manufacturer for detailed examination.
Engine Disassembly and Metallurgical Analysis
The throttle and fuel metering assembly had impact damage. The finger screen was clean; the fuel pump rotated freely and functioned properly in flow testing. The manifold valve plunger assembly was intact. The number 2 fuel injector showed impact damage; the number 6 injector was clogged with debris; numbers 1, 3, 5, and 4 were clear. The number 4 spark plugs were oil-soaked; others were normal. Magnetos produced spark. The oil pump cavity contained scoring and small metallic particulates. The oil filter had an abundance of flakes and slivers. The oil sump was breached with residual oil and significant metallic debris. The oil suction screen had metallic material but was not obstructed. Cylinder combustion chambers were normal. The number 3 cylinder intake push rod tube was displaced; rocker arms were normal.
Piston heads had normal deposits; all skirts except numbers 5 and 6 showed mechanical damage. A crescent-shaped impression on the number 3 piston face matched the exhaust valve diameter. Rings were mostly intact; some had missing portions. The crankshaft and counterweight assembly showed lubrication distress and thermal/mechanical damage on journals 1, 2, 4, and 5. Main bearings had evidence of contamination and incipient oil starvation. Connecting rods 2 and 4 were fractured; the number 4 connecting rod cap and bolts were sent for metallurgical examination.
Stereomicroscopic examination revealed that the number 4 connecting rod cap fracture surface had fatigue cracking initiating from both inner and outer surfaces, comprising 57% and 21% of the fracture, respectively, with the remainder overstress. Bolts showed necking and overstress features. Alloy analysis identified Grade 4340 steel for the rod and cap, and Grade 8740 for the bolts, meeting material requirements. Hardness measurements for the rod (29.7 HRC) and cap (38.5 HRC) met specifications, but the bolt hardness (37.1 HRC) was slightly below the specified range of 38-42 HRC.