History of Flight
On May 27, 2021, about 0750 eastern daylight time, a Grumman G-164B airplane, N8376K, was substantially damaged when it was involved in an accident near Celina, Ohio. The pilot sustained serious injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight.
Earlier in the morning, the pilot repositioned the airplane from Defiance Memorial Airport (DFI), Defiance, Ohio, to Lakefield Airport (CQA), Celina, Ohio. Shortly after departing DFI, the pilot noticed he forgot to bring his GPS and returned to DFI. After retrieving the GPS, he departed again and flew to Charloe Airport (53OH), Paulding, Ohio, to retrieve a hose connector before continuing to CQA. No issues were noted during preflight or the repositioning flights.
The accident occurred during the first agricultural flight of the day. Before departure, the retailer loaded the water/product solution while the pilot fueled with 27 gallons of Jet-A. The pilot estimated total fuel at 80 gallons and water/product at 330 gallons, with the airplane below maximum gross weight.
The pilot back taxied on runway 8 at CQA and performed an uneventful engine runup. During takeoff, engine torque and propeller speed indicated 52 psi and 100% respectively. The pilot stated he did not perform a maximum-performance takeoff, and a normal liftoff was achieved.
During initial climb, about 20-75 ft above ground level, the airplane experienced a sudden fluctuation in engine power from high to low and back to high. The pilot was thrown forward into his restraints and then back, occurring once. After the power loss, propeller speed remained 100% but climb performance diminished. The pilot did not cross-check other engine gauges.
The pilot pitched for best glide and turned right to avoid trees. Believing the engine was still running, he did not jettison the load. The engine lost all power shortly after the turn. The pilot heard only wind and jettisoned the load, but the airplane descended and impacted a levee, nosing over into the river.
Wreckage and Impact Information
The airplane came to rest inverted on the riverbank, sustaining substantial damage to the vertical stabilizer, rudder, upper wings, and fuselage.
Engine examination revealed the airframe control linkage to the propeller pitch control (PPC) was disconnected from the splined end of the shouldered shaft. The retaining bolt was loose and lacked safety wire. The PPC shaft had an internally threaded hole, but no evidence of a secondary retention feature was found.
Postaccident engine disassembly showed rotational scoring on compressor impeller blades, impeller shroud, and propeller shaft. Light metal spray was present on 3rd stage turbine stator vanes, and earthen debris coated the gaspath. The torsion shaft aft spline was fractured 1.25 inches from the aft end. No preimpact failure or other anomalies were found that would have prevented normal operation.
The engine fuel pump failed pressure testing; the high-pressure gear stage carbon bushing was fractured, consistent with impact damage. The fuel control unit (FCU) exhibited out-of-limits fuel flow readings on acceleration and deceleration schedules, but no internal failure was found. The propeller governor tested normally.
The propeller remained attached with all three blades intact at the hub but fractured near the tips. Damage included chordwise scoring, bending opposite rotation, and leading edge gouging. No evidence of preimpact failure was found; damage was consistent with high impact forces and the propeller was in normal blade angle range at impact.
Additional Information
The engine was previously installed on a Mitsubishi MU-2B-20, removed November 12, 2014, and installed on the accident airplane March 24, 2015 under STC No. SA7987SW. The HOBBS meter read 1,382.4 hours at the accident. The airplane had 14.1 hours since the last 100-hour and annual inspections. Total airframe time was 9,187.2 hours; engine time since new was 7,733 hours, with 521.2 hours since last overhaul.
FAA AD 75-16-20 (July 29, 1975) required repetitive inspections of the PPC lever for security and rigging on MU-2 models. Engine manufacturer SB TPE331-72-2190/2191/72291 (December 21, 2011) recommended inspecting PPC assembly for a threaded hole to accommodate a secondary retention feature. FAA AD 2020-26-14 (December 29, 2020) superseded AD 75-16-20 and mandated secondary retention and repetitive inspections for MU-2 airplanes, but did not cover other models modified by STCs. In response to this accident, FAA AD 2022-01801-A (May 17, 2023) mandated the secondary retention feature on G-164A and G-164B airplanes equipped with TPE331 engines.
According to the Honeywell TPE331 overhaul manual, the PPC acts as an oil passage in propeller-governing mode and provides manual control in beta mode. A disengagement of the airframe PPC linkage results in inability to change fuel flow and/or propeller pitch during flight and landing.