FORT GAINS, GA, USA
N6630Q
Grumman-Schweizer G-164B
The flight was loaded with fertilizer and had taken off, when the engine lost power. The pilot made a forced landing, and the airplane's landing gear went into a ditch and separated. The pilot had made 3 previous takeoffs under similar load conditions without incident. The pilot said, 'initially during the takeoff roll the aircraft accelerated normally.' However, immediately after breaking ground, during the initial climbout, the engine began to loose power, and the aircraft began to loose lift. The airplane continued to sink with partial power until impact. Examination of the engine revealed no exterior damage. The engine teardown revealed that improper atomization of the fuel resulted in a non-atomized fuel stream at the first-stage turbine rotor. The subsequent atomization and ignition of this fuel resulted in a localized area of increased temperature and non-uniform thermal damage to the second- and third-stage turbine stators. The localized area of increased temperature resulted in thermal damage to the second- and third-stage turbine rotors, and increased second- and third-stage turbine rotor blade tip clearance, rendering the engine incapable of producing full power. There was no evidence that the engine control system components contributed to the loss of engine power reported during the accident flight.
On December 1, 1998, about 1600 eastern standard time, a Grumman-Shweizer G-164B, N6630Q, registered to Ag Pilots Inc., impacted with a ditch during a forced landing near Fort Gains, Georgia. Visual meteorological conditions prevailed at the time, and no flight plan was filed for the 14 CFR Part 137 aerial application flight. The airplane was substantially damaged. The commercial-rated pilot reported no injuries. The flight was originating at the time. The flight was loaded with fertilizer and had taken off, when the engine lost power. The pilot made a forced landing, and the airplane's landing gear went into a ditch and separated. According to the pilot, "...I had made 3 previous takeoffs under similar load conditions. I had taken on fuel, about 3/4 of a tank, the previous load, and took off without incident....initially during the takeoff roll the aircraft accelerated normally. However, immediately after breaking ground, during the initial climbout, the engine began to loose power, and the aircraft began to loose lift. Because of the terrain, at the departure end of the runway, I was forced to make [a] right turn of approximately 20 degrees, to avoid [a] collision with tall trees. The aircraft continued to sink with partial power until impact...." According to the FAA inspector's statement, "...about 100 feet the pilot experienced a power loss...[he] veered 20 degrees to the right and landed in a field over-grown with weeds. The aircraft struck a small ditch and sheared off the left main landing gear. The right gear folded and the aircraft skidded on its belly to a stop about 100 feet from the impact point. The upper left wing was ruptured and leaking fuel." The FAA inspectors examined the engine and according to their statement they found the following,"...oil quaintly checked normal. The engine had no exterior damage...found what appeared to be a fertilizer residue build up obstructing the first stage compressor intake air flow. The buildup was hard and had not dislodged during the crash impact forces; nor, during the aircraft transportation to the storage sight. The shut down solenoid is electrically and mechanically controlled. It normally should open and close electrically; however, it [would] only close mechanically by a lever available to the pilot. Inspection found the 'electric closed' wire to have been cut. The aircraft powerplant shut-down was reportedly done with the use of the mechanical handle. Additionally, the fuel heat system had been deactivated. Lines were capped off. The start enrichment system had been deactivated. One end had been capped and the other end crimped. According to the FAA, examination of the airplane's fuel system revealed, "...the main fuel filter was removed for inspection, and found to be contaminated with a substantial amount of what appeared to be dirt, scalant (sic); or rust." On April 1, 1999, the engine from N6630Q was examined under the supervision of the FAA at Allied Signal's facilities Phoenix, Arizona. Examination of the engine revealed that improper atomization of the fuel resulted in a non-atomized fuel stream at the first-stage turbine rotor. The subsequent atomization and ignition of this fuel resulted in a localized area of increased temperature and non-uniform thermal damage to the second- and third-stage turbine stators. The localized area of increased temperature resulted in thermal damage to the second- and third-stage turbine rotors, and increased second- and third-stage turbine rotor blade tip clearance, rendering the engine incapable of producing full power. It was determined that the thermal damage to the turbine components occurred prior to the accident flight based on oxidation found on the second-stage turbine rotor, and the oxidation found on all damaged surfaces of the turbine components. The ITT (inlet turbine temperature) thermocouple assembly was cable of providing an accurate indication of inter-stage turbine temperature to the aircraft indication system. There was no evidence that the engine control system components contributed to the loss of engine power reported during the accident flight (Excerpts of Allied Signal's teardown report are attachments to this report). The FAA concurred with the Allied Signal teardown report, and were in agreement that the second- and third-stage turbine rotor and stators displayed thermal damage.
a power loss due to internal damage to the second- and third- stage turbine rotor blades, due to thermal heat, rendering the engine incapable of producing full power, resulting in a forced landing, and subsequent impact with the terrain.
Source: NTSB Aviation Accident Database
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