MATINICUS, ME, USA
N1523U
Cessna U206F
The pilot reported a partial loss of engine power while on final approach and he made a forced landing to the right of the runway, collapsing the main gear. Examination of the engine revealed that the fuel metering unit inlet screen was 75 percent blocked with green, lint-like debris. The debris was removed from the screen. The engine started normally and ran without interruption. The operator used the Cessna Progressive Care and Continuous Inspection (CPCCI) program to maintain the 1973 U206F airplane. According to Cessna, the CPCCI program was designed for 1977 through 1986 airplanes. However, Cessna established procedures for vintage airplanes not specifically covered in this program. The CPCCI Operations Manual stated, "After reviewing the specific aircraft, add inspection requirements to the Operation Schedule for specific items which were not covered." A review of the 1969 through 1976 206 Service Manual revealed that the "fuel injector screen" should be inspected "each 50 hours." According to the TCM 100-hour maintenance schedule, "remove fuel metering unit inlet screen and inspect for foreign material." A review of the 1977 through 1986 206 Service Manual revealed that there was no requirement to inspect the fuel injector screen. Cessna could not explain why the inspection was included in the 1969 through 1976 206 Service Manual, and not in the 1977 through 1986 206 service manual. On April 17, 2002, the operator added the fuel metering unit inlet screen inspection to Operation #1 and #3, item J25, to the company's CPCCI program.
On April 3, 2002, at 1120 eastern standard time, a Cessna U206F, N1523U, was substantially damaged during a forced landing on Matinicus Island, Maine. The certificated commercial pilot was not injured. No flight plan was filed for the flight that originated at Knox-County Regional Airport (RKD), Rockland, Maine, at 1100. Visual meteorological conditions prevailed for the mail retrieval flight conducted under 14 CFR Part 91. According to the pilot, he performed a pre-flight inspection of the airplane prior to departure, which included checking the fuel from each fuel sump. The fuel was absent of debris and water. During the flight, the engine operated normally until the airplane was 500 feet above the water, on final approach to the island airstrip. The engine failed to respond when the pilot applied power to compensate for the gusty wind conditions. The pilot established best glide speed, switched fuel tanks, and turned on the fuel pump. The propeller continued to turn, but the engine was "spitting as if it was not getting fuel." As the airplane neared the water, the pilot realized the engine had low, but partial power. He was able to reach the shoreline, and landed 40 feet to the right of runway 18, a 1,800-foot-long by 23-foot-wide gravel runway. A Federal Aviation Administration (FAA) inspector performed an on-scene examination of the airplane and engine on April 4, 2002. According to the inspector, the main nose gear had collapsed, the windshield was broken, the right wing exhibited leading edge damage, the firewall was wrinkled, and all three propeller blades were bent aft. The inspector reported that the fuel selector was found set to the left wing fuel tank. Approximately 22 gallons of fuel was in the left wing fuel tank, and approximately 20 gallons was in the right wing fuel tank. The fuel strainer bowl was inaccessible and could not be examined. However, when the fuel strainer drain knob was pulled, fuel was observed to pour freely from the strainer. The fuel manifold valve was disassembled and examined. When the top section of the manifold valve was removed, fuel was found under pressure, the diaphragm was intact, and the fuel screen was absent of debris. The inspector also reported that valve train continuity from the power train to the accessory section was established when the propeller was manually rotated. During the valve train continuity check, compression was established on each cylinder and spark was produced to each ignition lead. The top spark plugs were removed and appeared normal. On April 8, 2002, the operator attempted to run the engine on the airframe, utilizing the airplane's fuel system. A test propeller was installed on the engine, and several unsuccessful attempts were made to start it. On April 12, 2002, the operator recovered the airplane and secured it at the company maintenance facility. An engine examination was scheduled to be performed at the maintenance facility on April 15, 2002, under FAA supervision. The operator's vice president of operations reported that prior to the scheduled examination, the operator replaced a bent fuel line that was crushed when the nose wheel collapsed. Also, the firewall fuel strainer screen and metering unit fuel inlet screen were removed. When the fuel metering unit inlet screen was removed, about 75 percent of the screen was found to be covered with a green-colored "lint-like" debris. The debris was fuel soaked, and upon removal of the screen, the debris collapsed on itself. The debris was removed from the screen, and the screen was placed back into the fuel control unit. A small amount of similar lint-like debris was also found and removed from the firewall fuel filter screen. The engine was examined on April 15, 2002, with a representative of Teledyne Continental Motors (TCM) and an FAA inspector present. According to the inspector, the engine started immediately and ran continuously at various power settings without interruption. The debris from both screens was examined at the Safety Board's Materials Analysis Laboratory, Washington, D.C. The examination revealed that a majority of the debris consisted of 1/10-inch green and tan flat fibers. Some of the fibers were also red and blue. The fibers were examined with a scanning electron microscope with energy dispersive spectroscopy (EDS), which revealed major peaks of carbon, oxygen, and calcium. On April 23, 2002, an examination of the operator's above-ground fuel tank and fuel truck was conducted under FAA supervision. According to the FAA inspector, the fuel truck, fuel tank, and their respective fuel screens were found to be clean and absent of debris. Also, a fuel sample was tested by the vendor and was found absent of debris. The airplane was a 1973 U206F airplane, which had accrued 9,151.4 total airframe hours. The engine was a TCM IO-520-F27B, and had 1,306 hours since overhaul. The last maintenance inspection was completed on February 8, 2002. The operator used the Cessna Progressive Care and Continuous Inspection Program to maintain the airplane, which, according to a representative from Cessna Aircraft Company, was designed for 1977 through 1986 U206/TU206 model airplanes. The company also encouraged owners/operators of airplanes that did not fall within the inclusive dates to use the program, and established procedures for them. According to the Cessna Progressive Care and Continuous Inspection Operations Manual, section J(2)(e): "After reviewing the specific aircraft, add inspection requirements to the Operation Schedule for specific items which were not covered." A review of the 1969 through 1976 206 and T206 series Service Manual, page 2-23, revealed that the "fuel injector screen" [also known as fuel metering unit inlet screen] should be inspected "each 50 hours." According to the Teledyne Continental Motors, 100-hour maintenance schedule, item 11, "remove fuel metering unit inlet screen and inspect for foreign material." A review of the 1977 through 1986 206 and T206 series Service Manual revealed that there was no requirement to inspect the fuel injector screen. Cessna could not provide a detailed explanation as to why this inspection was included in the 1969 through 1976 206 and T206 series Service Manual, and not in the 1977 through 1986 206 and T206 series Service Manual. On April 17, 2002, the operator added the fuel metering unit inlet screen inspection to Operation #1 and #3, item J25, to the company's Cessna Progressive Care and Continuous Inspection program. The inspection would be completed every 50 hours. The pilot reported a total of 5,500 flight hours, of which, 1,064 hours were in make and model. Weather reported at Rockland, Maine, at 1115, included wind from 210 degrees at 14 knots gusting to 21 knots, visibility 10 statute miles, and ceiling 3,200 broken.
A partially blocked fuel metering unit inlet screen, which resulted in a partial loss of engine power. Also causal, was the operator's lack of inlet screen inspection procedures.
Source: NTSB Aviation Accident Database
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