History of Flight
On March 23, 2010, at about 1415 Alaska daylight time, a Cessna 206, registration N522HA, sustained substantial damage during a forced landing shortly after takeoff from Homer Airport, Homer, Alaska. The airplane was operated by Homer Air as scheduled domestic commuter Flight 114A under visual flight rules. The commercial pilot was not injured; the two passengers sustained minor injuries. Visual meteorological conditions prevailed, and company flight following procedures were in effect. The flight was en route to Nanwalek, Alaska.
According to the pilot, just after takeoff from Runway 3, while climbing to 300 feet above the runway, the engine began to run rough, lose power, and vibrate violently. Unable to restore power, he turned left 180 degrees to attempt an emergency landing on Runway 21, but the airplane continued to descend and collided with snow-covered terrain about 500 feet north of Runway 21. It came to rest inverted, sustaining substantial damage to the wings, fuselage, and empennage.
A Federal Aviation Administration airworthiness inspector examined the engine and found a cracked number four cylinder head, slightly separated from the cylinder barrel.
Crew Information
The 37-year-old pilot held a commercial pilot certificate with airplane single-engine land and multiengine land ratings, as well as a flight instructor certificate with airplane single-engine and instrument airplane ratings. His most recent second-class medical certificate was issued on June 19, 2009, with no limitations.
The pilot's aeronautical experience totaled about 8,000 hours, including 5,000 hours in the accident airplane make and model. He had flown 70 hours in the preceding 90 days and 20 hours in the preceding 30 days. On the day of the accident, he accrued 3 hours of flight time.
Aircraft Information
The airplane had a total time in service of 10,542.8 hours and was maintained under an Approved Airworthiness Inspection Program. The most recent inspection (Event 1) was on March 16, 2010, 15.7 hours before the accident.
The airplane was equipped with a Teledyne Continental Motors IO-520-F series engine, with a total time in service of 3,555.8 hours. A major overhaul was performed by Aero Recip of Alaska on July 3, 2007, 1,687.1 hours before the accident. The recommended time between overhaul for the engine is 1,700 hours.
During the most recent Event 1 inspection, compression tests of the engine cylinders showed values of 70 psi for cylinders 1-5 and 74 psi for cylinder 6. The engine cylinders used in the overhaul were obtained from Superior Air Parts, Inc.
Meteorological Information
The closest official weather observation station was at Homer. At 1353 on March 23, 2010, an Aviation Routine Weather Report reported: wind 070 degrees at 8 knots; visibility 10 statute miles; clear skies; temperature 34°F; dew point 45°F; altimeter 29.49 inHg.
Aerodrome Information
Homer Airport has a single hard-surfaced runway oriented 030/210 degrees magnetic. Runway 3 is 6,701 feet long by 150 feet wide. The airport elevation is 84 feet msl. The departure end of Runway 3 has a clearway extending about 1,800 feet beyond the runway edge, consisting of snow-covered tundra. Beyond that, terrain includes sparsely scattered spruce trees extending an additional 2,800 feet to the shores of Kachemak Bay.
Wreckage and Impact Information
All major components were found at the main wreckage area. The airplane came to rest inverted, with substantial damage to the wings, fuselage, and empennage. About 100 feet northeast of the main wreckage was a crater about 4 feet in diameter and 1 foot deep, believed to be the initial impact point. The debris path between the crater and main wreckage included groceries, passenger personal effects, and fragmented aircraft components.
The engine cowling and firewall were crushed and displaced aft. The engine sustained impact damage to the underside and lower front. The oil sump was crushed upward. Tundra was embedded in the engine oil cooler.
The right wing lift strut remained attached; the left wing lift strut separated from its fuselage attach point. The left wing separated from the fuselage, and the carry-through was broken and crushed aft. The entire empennage separated from the fuselage.
Flight control surfaces remained connected to their attach points. Due to impact damage, controls could not be moved by their mechanisms, but flight control cable continuity was established to the cabin/cockpit area.
Tests and Research
The cracked number four engine cylinder (part number SA52006-A1-F) was examined by the NTSB Materials Laboratory. The aluminum head assembly was cracked between the 14th and 15th fins from the inboard end, propagating circumferentially approximately 300 degrees, with an approximate length of 11.9 inches. The separation area was covered by a dark heavy layer consistent with combustion products. Magnified optical examination found fatigue progression features originating at multiple origins along the fracture surface.
Additional Data
On September 9, 2009, the FAA's Engine and Propeller Directorate issued an airworthiness directive requiring a recurring 50-hour inspection of all TCM IO-520 and IO-550 series engines with certain Superior Air Parts cylinder assemblies. The accident airplane's number four cylinder (part number SA52006-A1) was not included in the AD.