Carroll, IA, USA
N7315P
AIR TRACTOR INC AT-401
The commercial pilot had completed half of a planned aerial application of a field when the airplane’s engine lost power. The pilot performed a forced landing to a field which resulted in substantial damage to both wings. Postaccident examination of the airplane revealed the inline airframe fuel boost pump would not provide normal fuel output due to wear of the pump motor shaft and leakage of the pump seal. The pump also did not bypass fuel during the on-scene examination but did bypass fuel during testing at the pump manufacturer. The differences in bypass test results were most likely due to plumbing differences between the airplane and the test fixture. The pump manufacturer recommended a 10-year overhaul of the pump and did not provide an hours-in-service overhaul recommendation. The pump was manufactured in 2007, and an airplane logbook record indicated it had been last overhauled in 2013.
On July 13, 2021, at 1654 central daylight time, an Air Tractor Inc. AT-401, N7315P, sustained substantial damage when it was involved in an accident near Carroll, Iowa. The pilot was not injured. The airplane was operated under Title 14 Code of Federal Regulations Part 137 as an aerial application flight. The pilot stated that he had completed half of the planned aerial application of a field when the engine lost power coming out of a turn. The pilot then performed a forced landing. The airplane impacted terrain and sustained substantial damage to its wings. The airplane was modified by the installation of a Walter M601E-11 turbine engine through supplemental type certificate SA01281CH issued to Johnson Airspray Inc. On-scene examination of the engine by a Federal Aviation Administration (FAA) principal maintenance inspector and representatives from GE Aviation revealed no mechanical anomalies that would have precluded normal operation. Subsequent removal and testing of the engine-driven fuel pump and fuel control revealed that both units met test specifications. During the on-scene examination, a crane was used to level the aircraft, which ensured that the airplane header fuel tank was full. The main fuel line from the airplane fuel filters to the engine-driven fuel pump was disconnected at the fuel pump end and placed in a bucket to capture fuel. The electric-driven airframe inline boost pump was turned on, and there was no fuel flow from the main fuel line. The B-nut on the hose from the header tank to the selector valve was loosened at the selector valve end to confirm there was fuel in the header tank, and fuel was noted to be present. The B-nut was retightened, and the output fuel line from the airframe boost pump was loosened; a small amount of fuel dripped. The dripping could be stopped and started by opening and closing the airplane fuel selector valve. The airframe boost pump was again turned on; there was no steady flow output; and there was no bypass of fuel. The airframe boost pump was removed for further testing and examination at its manufacturer. The airframe boost pump was a Weldon pump, part number 2003-B, serial number 130661, manufacturing date August 6, 2007. The pump was sent to the facilities of Weldon Pump for testing and examination under the supervision of an FAA aviation safety inspector. During testing, the pump was placed on a test stand and power was applied. The pump energized and turned; however, there was no fuel output, and fuel leaked from the shaft seal. The pump bypass was also checked on the test stand with no restrictions noted; fuel was able to flow through the pump. Disassembly of the pump from its electric motor revealed the motor’s slotted shaft was worn to the point that it would not engage with the pump’s rotor tang. Weldon Pump representatives stated that the company recommended a 10-year overhaul requirement of the pump. There was no time-in-service requirement in Weldon Pump’s recommendation. An airplane logbook record, dated July 8, 2013, with an hour meter reading of 2,497.8 hours, stated, “R&R FUEL PUMP P/N 2003B WITH OH UNIT. OPS CHECK GOOD.” At the time of the accident, the hour meter indicated 5,136.7 hours.
The wear-related failure of the airframe fuel boost pump, which resulted in fuel starvation and a loss of engine power.
Source: NTSB Aviation Accident Database
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