Homer, AK, USA
N522HA
CESSNA 206
The pilot departed on a scheduled passenger flight and, shortly after takeoff, about 300 feet above the ground, the engine began to run rough, lose power, and vibrate violently. He attempted to return to the runway, but, during the turn, the airplane impacted snow-covered terrain, coming to rest inverted about 500 feet from the runway. The airplane sustained substantial damage to the wings, fuselage, and empennage. A postaccident examination revealed that the No. 4 engine cylinder head was cracked and separated from the cylinder barrel, resulting in the power loss. The pilot's decision to attempt to return to the departure runway with insufficient altitude, instead of landing in the 1,800 foot long clearway, precipitated a loss of control and impact with terrain, adding to the severity of the accident.
HISTORY OF FLIGHT On March 23, 2010, about 1415 Alaska daylight time, a Cessna 206 airplane, N522HA, sustained substantial damage during a forced landing shortly after takeoff from the Homer Airport, Homer, Alaska. The airplane was being operated by Homer Air, Homer, as scheduled domestic commuter Flight 114A, a visual flight rules (VFR) flight, under the provisions of 14 CFR Part 135. 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. During a telephone conversation with the National Transportation Safety Board investigator-in-charge on March 23, the pilot reported that just after takeoff from Runway 3, as the airplane climbed to 300 feet above the runway, the engine began to run rough, lose power, and vibrate violently. Unable to restore engine power, he turned the airplane left, 180 degrees, to attempt an emergency landing on Runway 21, but the airplane continued to descend, and collided with an area of snow-covered terrain about 500 feet north of Runway 21. It came to rest inverted, sustaining substantial damage to the wings, fuselage, and empennage. On March 23, a Federal Aviation Administration (FAA) airworthiness inspector from the Anchorage Flight Standards District Office traveled to the accident site to examine the airplane before it was recovered. The inspector reported that his examination of the engine revealed a cracked number four cylinder head, which was 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. He also held 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, and contained no limitations. According to the Pilot/Operator report (NTSB form 6120.1) submitted by the operator, the pilot's aeronautical experience consisted of about 8,000 hours, of which 5,000 hours were in the accident airplane make and model. In the preceding 90 and 30 days prior to the accident, the report listed a total of 70 and 20 hours, respectively. The pilot accrued 3 hours of flight time on the day of the accident. AIRCRAFT INFORMATION The airplane had a total time in service of 10,542.8 hours. The airplane is maintained on an Approved Airworthiness Inspection Program (AAIP). The most recent inspection (event 1), was on March 16, 2010, 15.7 hours before the accident. The airplane had a Teledyne Continental Motors (TCM) IO-520-F series engine, with a total time in service of 3,555.8 hours. The maintenance records note that a major overhaul was done by Aero Recip of Alaska, Anchorage, Alaska, on July 3, 2007, 1,687.1 hours before the accident. The recommended time between overhaul (TBO) for an IO-520-F engine is 1,700 hours. According to the operator's AAIP inspection schedule, a compression test of the engine's cylinders is required during each Event inspection, at 50 hour intervals. During the most recent Event 1 inspection, on March 16, 2010, 15.7 hours before the accident, the engine compression was noted as follows: Cylinder Number 1, 70 psi; Number 2, 70 psi; Number 3, 70 psi; Number 4, 70 psi; Number 5, 70 psi, Number 6, 74 psi. The engine cylinders utilized for the engine overhaul were obtained from Superior Air Parts, Inc., Coppell, TX. METEOROLOGICAL INFORMATION The closest official weather observation station is Homer. On March 23, 2010, at 1353, an Aviation Routine Weather Report (METAR) was reporting in part: Wind, 070 degrees at 8 knots; visibility, 10 statute miles; clouds and sky condition, clear; temperature, 34 degrees F; dew point, 45 degrees F; altimeter, 29.49 inHg. AERODROME AND GROUND FACILITIES The Homer Airport is equipped with a single, hard-surfaced runway on a 030 to 210 degree magnetic orientation. Runway 3 is 6,701 feet long by 150 feet wide. The airport elevation is 84 feet msl. The departure end of Runway 3's clearway extends about 1,800 feet beyond the runway's edge. The terrain within the clearway consists of snow-covered tundra. The terrain beyond the clearway consists of sparsely scattered spruce trees, which extends an additional 2,800 feet, and to the shores of Kachemak Bay. WRECKAGE AND IMPACT INFORMATION All of the airplane's major components were found at the main wreckage area. It came to rest inverted, sustaining substantial damage to the wings, fuselage, and empennage. About 100 feet northeast from the main wreckage site was a crater measuring about 4 feet in diameter, and 1 foot deep. This crater is believed to be the point of original impact. The debris path between the crater and the main wreckage site consisted of groceries, passenger personal effects, and various fragmented aircraft components. The engine cowling and fuselage firewall were crushed and displaced aft. The engine sustained impact damage to the underside, and lower front portion of the engine. The engine oil sump was crushed upward against the case. Tundra was found imbedded in the engine oil cooler. The right wing lift strut remained attached to the wing and its lower attach point. The left wing lift strut was attached to the wing, but was separated from its fuselage attach point. The left wing was separated from the fuselage and the carry-through was broken, and crushed aft. The entire empennage was separated from the fuselage. The flight control surfaces remained connected to their respective attach points. Due to the impact damage, the flight controls could not be moved by their respective control mechanisms, but the continuity of the flight control cables was established to the cabin/cockpit area. TESTS AND RESEARCH The cracked number four engine cylinder, part number: SA52006-A1-F, was sent to the National Transportation Safety Board's Materials Laboratory for examination. A Safety Board metallurgist reported the aluminum head assembly was cracked between the 14th and 15th fins as numbered from the inboard end of the cylinder head. The crack propagated circumferentially approximately 300 degrees. Approximate length of the crack was 11.9 inches. The area of the separation was covered by a dark, heavy layer of material that was consistent with combustion products. A magnified optical examination of the fracture surfaces on the cylinder assembly found fatigue progression features, which originated at multiple origins along the fracture surface. A complete copy of the NTSB's materials laboratory factual report is included in the public docket of this report. ADDITIONAL DATA September 9, 2009, the Federal Aviation Administration's Engine and Propeller Directorate Office, issued an airworthiness directive (AD) requiring a special reoccurring 50-hour inspection of all TCM IO-520 and IO-550 series reciprocating engines with Superior Air Parts, Inc., cylinders assemblies, part numbers SA52000-A1, SA52000-A20P, SA52000-A21P, SA52000-A23P, SA55000-A1, or SA55000-A20P, installed. The accident airplane's number four cylinder, part number SA52006-A1, was not included in the AD.
The fatigue failure of the No. 4 engine cylinder head resulting in a loss of engine power. Contributing to the severity of the accident was the pilot's decision to attempt a low altitude turn back to the airport, resulting in a loss of control.
Source: NTSB Aviation Accident Database
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