VALLE, AZ, USA
N9439M
Cessna 207A
According to the pilot, he was departing about 50 pounds under gross weight. The paved 8,999-foot runway is located at 6,606 feet msl. The winds were down the runway about 20 to 25 knots, with the temperature about 50 degrees, and the density altitude about 8,100 feet msl. About 3/4 down the runway's length the pilot aborted the takeoff. He taxied back to the terminal and off loaded a passenger, who he estimated to be about 300 pounds. He now estimated the airplane to be about 350 pounds below the gross weight limit. The pilot was again cleared for takeoff. He started his takeoff with the mixture full rich, and then gradually leaned the mixture to about 20 gallons per hour. He said the acceleration felt slow, but normal for a loaded airplane. After becoming airborne, about 100 feet agl, the airplane's climb performance seemed to be getting worse, and it was too late to abort. The control tower advised a 15-degree right turn towards lower terrain, which the pilot performed clearing tree tops about 50 feet. He reported that all preflight and in-flight checks were normal. He performed additional in-flight checks of the engine systems, including simultaneous use of the fuel boost pumps, with no increase in performance. About 10 minutes into the flight, the airplane was still 50 to 100 feet above treetops and approaching high-tension power lines without enough altitude to clear them. The pilot started to look for a landing site. Subsequently the airplane collided with trees about 14 miles from the departure point. Examination of the magnetos by the manufacturer revealed numerous discrepancies affecting the optimum performance of the engine.
On September 23, 2000, about 1510 hours mountain standard time, a Cessna 207A, N9439M, operated as flight 58 by Westwind Aviation, Inc. of Phoenix, Arizona, was substantially damaged during a collision with trees and terrain 14 miles south-southeast of the Grand Canyon near Valle, Arizona. The commercial pilot and three passengers all received minor injuries. The flight was operating as an on-demand air taxi, sightseeing flight under the provisions of 14 CFR Part 135. Visual meteorological conditions prevailed for the flight, and a company visual flight rules (VFR) flight plan was filed. The flight originated at the Grand Canyon, about 1445, as a return flight to Scottsdale, Arizona. According to the pilot, he was departing about 50 pounds below gross weight. The paved 8,999-foot runway (21) is located at 6,606 feet mean sea level (msl). The winds were down the runway about 20 to 25 knots, with a temperature about 50 degrees, and a density altitude about 8,100 feet msl. About 3/4 down the runway's length the pilot aborted the takeoff. He taxied back to the terminal and off loaded a passenger, who he estimated to be about 300 pounds. He now estimated the airplane to be about 350 pounds below the gross weight limit. The airplane was cleared for takeoff from runway 21. The pilot started his takeoff with the mixture full rich, and then gradually leaned the mixture to about 20 gallons per hour. The acceleration felt slow, but normal for a loaded airplane. After becoming airborne, about 100 feet above ground level (agl), he said the airplane's climb performance seemed to be getting worse, and it was too late to abort. The control tower advised a 15-degree right turn towards lower terrain, which he performed, clearing tree tops about 50 feet. The pilot reported that all preflight and in-flight checks were normal. The pilot performed additional in-flight checks of the engine systems, including simultaneous use of the fuel boost pumps, with no increase in performance. About 10 minutes into the flight, the airplane was still 50 to 100 feet above treetops, and approaching high-tension power lines without enough altitude to clear them. The pilot started to look for a landing site. Subsequently, the airplane collided with trees about 14 miles from the departure point. The three passengers provided detailed written reports of the accident flight, which are attached. PERSONNEL INFORMATION The pilot was issued a commercial certificate on December 15, 1999, with 270 total flight hours. He was rated for airplane single engine land and instrument airplane. At the last documented first-class flight physical conducted on July 20, 2000, he reported a total flight time of 650 hours. The pilot reported a total flight time of 858 hours, with 6 hours in make and model. AIRCRAFT INFORMATION According to airplane records, the last documented annual inspection occurred on August 31, 2000, about 43.8 recording tachometer hours before the accident. On March 11, 1999, an engine change was accomplished to increase the horsepower from 285 to 300, as per supplemental type certificate SA00173AT. The change occurred at hour meter 8,745.6 total airframe hours, about 825.3 hours prior to the accident. According to logbook records, on April 5, 2000, at 9,228.5 total airframe hours, a 500-hour midlife magneto inspection occurred about 342.4 hours before the accident. It documents the replacement of magneto points per Unison data M3081, and setting of internal timing. WRECKAGE AND IMPACT INFORMATION A postaccident examination of the airplane and engine occurred after recovery to a storage area in Phoenix, Arizona. TESTS AND RESEARCH During the postaccident examination of the airplane and engine, the magnetos were functionally tested. Because of the poor results, the magnetos were sent to the manufacturer, Unison Industries, for further examination and functional testing. The Federal Aviation Administration, Dupage Flight Standards District Office, West Chicago, Illinois, witnessed the procedure. Examination of the left magneto revealed an intermittent spark on ignition lead T2. Opening of the magneto revealed a point's gap of .019, the factory maximum is .012. The contact point timing was advanced 9 degrees from E-gap. The rotor shaft gear was advanced one tooth of engagement. The right magneto ran intermittently at 750 rpm to 1,700 rpm. According to the manufacturer, the internal examination revealed the contact points to be severely worn; the gap was .021, and the point timing was advanced 11 degrees from E-gap. The spark plugs were removed and examined. The engine manufacturer representative stated that the spark plugs exhibited nominal electrode erosion and wide gapping. Spark plugs 1 and 4, top and bottom, were black and sooty, as were the tops of the pistons. The magneto timing was found set at 26 degrees before top dead center (BTC). The engine specification calls for a magneto timing of 22 degrees BTC. ADDITIONAL INFORMATION The wreckage was released to the insurance company on June 28, 2001.
Improper maintenance and adjustment of the engine magnetos resulting in a loss of optimum performance during a critical takeoff that required peak engine performance.
Source: NTSB Aviation Accident Database
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