# NTSB CEN21LA237: Grumman G164, N8376K, Celina, OH, May 27, 2021

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Class 3 · Limited · Final report
- Date: May 27, 2021, 07:50 local (11:50 UTC)
- Place: Celina, OH
- Coordinates: 40.481742, -84.548806 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=40.4817&lon=-84.5488&mi=10
- Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping)
- Defining event: [Takeoff: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342)
- Highest injury: Serious injuries
- Injuries: 1 serious
- Status: Completed
- Report: Approved by Office Director
- Investigation class: Class 3
- NTSB office: Central Region
- Parties: Hartzell Propeller, Federal Aviation Administration - Columbus FSDO, Woodward, Honeywell Aerospace
- ADs cited in the narratives: [AD 75-16-20](https://openairdocs.org/ad/75-16-20), [AD 2020-26-14](https://openairdocs.org/ad/2020-26-14) (OpenAirDocs)
- NTSB case key (mKey): 103157
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN21LA237
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/103157/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=103157
- Page: https://openairdocs.org/ntsb/CEN21LA237

## Probable cause

A loss of engine power for undetermined reasons.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Grumman Acft ENG Cor-Schweizer G-164B, 11 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=3952802), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Takeoff: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Grumman Acft ENG Cor-Schweizer G-164B, 8 cases](https://openairdocs.org/ntsb-events/342/sequence.md?model=3952802), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md)

## Analysis

The pilot was departing on an agricultural flight when shortly after liftoff the airplane had a sudden engine power fluctuation from high-power to low-power and back to high-power. The pilot stated that he was “thrown forward” into his safety restraints and then “thrown back” into his seat. The forward/backward motion only occurred once and was “pretty quick and hard.” The pilot stated that after the loss of engine power, the propeller speed remained at 100% but the airplane’s climb performance was significantly diminished. The pilot pitched the airplane for best glide airspeed and entered a slight right turn from the runway heading to avoid trees. Believing the engine was still running, the pilot did not want to jettison the airplane’s load unnecessarily into the river near the airport. The pilot reported that the engine lost all power shortly after he entered the right turn. He then jettisoned the airplane’s load in an attempt to maintain a climb, but the airplane descended and impacted a levee, where it nosed over into the river. The airplane sustained substantial damage to the vertical stabilizer, rudder, upper wings, and the fuselage. Postaccident examination of the engine and propeller revealed no evidence of internal failure or other anomalies that would have precluded normal operation. The rotational rub/scoring observed in the engine, metal spray on the turbine stator vanes, and earthen debris throughout the engine core are all consistent with the engine producing power at impact. The engine’s torsion shaft aft spline was fractured consistent with sudden stoppage damage sustained when the propeller impacted the ground. The propeller exhibited impact-related damage that was consistent with high impact forces with the propeller rotating in the normal blade angle range of operation at moderate engine power. During takeoff and initial climb, the engine speed is controlled by the propeller governor and fuel flow is determined by the fuel control unit (FCU) Power Lever Schedule. Although postaccident testing of the FCU revealed anomalies with the Standard Day Acceleration and Deceleration Schedules, the FCU did not contribute to the loss of engine power because the Power Lever Schedule controls fuel flow to the engine during takeoff/initial climb. Additionally, according to the pilot, the propeller speed remained at 100% after the initial power fluctuation and is consistent with the engine operating with the condition lever set for takeoff. Postaccident examination revealed that the airframe control linkage to the engine propeller pitch control (PPC) was disconnected from the splined end of the shouldered shaft of the PPC, and the retaining bolt that normally secured the airframe linkage to the splined end was loose and was not secured by safety wire. Additionally, although the PPC shouldered shaft had an internally threaded hole for a secondary retention feature, there was no evidence that the secondary retention feature was installed at thetime of the accident. There are no outside forces acting on the PPC other than the linkage connection to the cockpit power lever. The PPC and FCU main metering valve are connected through the concentric shaft and are rigged to move together. A disengagement of the airframe PPC linkage will result in the pilot’s inability to change fuel flow and/or propeller pitch (blade angle) during flight and landing. If the airframe control linkage disconnected from the PPC shouldered shaft during initial climb at takeoff power, vibration could potentially rotate the PPC cam and reduce engine power as if the cockpit power lever had been pulled back by the pilot. The pilot’s description of being thrown-forward and then backward would have required the PPC cam to rotate from high-power to low-power and back to high-power before settling at a low power setting that would not sustain a climb. However, it is unlikely the propeller blade angle pitch change would be fast enough to cause the pilot to believe the engine had surged. As such, the pilot’s description of being thrown-forward and then backward is not consistent with a disconnected PPC airframe linkage. Although the airframe control linkage to the PPC shouldered spline was found disconnected after the accident with a loose retention bolt that was not secured with safety wire, the investigation was unable to conclusively determine if the control linkage disconnected from the PPC while inflight or during impact. Additionally, the investigation did not reveal any evidence of a preimpact failure or other anomalies that would have prevented normal engine operation.

## Factual narrative

The engine was previously installed on a Mitsubishi MU-2B-20 airplane and was removed on November 12, 2014. On March 24, 2015, the engine was installed on the accident airplane in accordance with supplemental type certificate (STC) No. SA7987SW. The airplane HOBBS meter indicated 1,382.4 hours at the accident site. The airplane had accumulated 14.1 hours since the last 100-hour and annual inspection completed on May 19, 2021, and May 20, 2021, respectively. The airframe and engine total time since new were 9,187.2 hours and 7,733 hours, respectively. The engine had accumulated 521.2 hours since the last overhaul completed on May 17, 2019. On July 29, 1975, the Federal Aviation Administration (FAA) issued Airworthiness Directive (AD) 75-16-20 for several Mitsubishi MU-2 models requiring repetitive inspections of the propeller pitch control lever for security and proper rigging. On December 21, 2011, the engine manufacturer released service bulletins (SB) TPE331-72-2190, TPE331-72-2191, and TPE331-72-72291 that recommended TPE331 operators inspect the PPC assembly to verify the splined end of the shouldered shaft had an internally threaded hole to accommodate a secondary retention feature for the aircraft linkage control interface. If the hole was not present or damaged, the SB included instructions to drill, tap, and countersink a threaded hole. The aircraft linkage control and secondary retention (bolt, washer, and lockwire) are considered airframe components. On December 29, 2020, the FAA issued AD 2020-26-14 for the Mitsubishi MU-2 fleet that superseded AD 75-16-20 and required the installation of a secondary retention feature on the PPC lever linkage, repetitive inspections of the PPC lever linkage, and reporting inspection results to the FAA. However, because AD 2020-26-14 was only applicable to Mitsubishi MU-2 airplanes it did not include other airplane make/models that were modified by STCs with a TPE331 engine and a comparable PPC linkage like the accident airplane (Grumman G-164B AgCat). In response to the accident, on May 17, 2023, the Federal Aviation Administration released Airworthiness Directive (AD) 2022-01801-A to mandate the installation of the PPC secondary retention feature on Allied Ag Cat Productions, Inc. model G-164A and G-164B airplanes to include those airframes that were equipped with a TPE331 engine installed under several identified STCs. According to the Honeywell TPE331 overhaul manual: The propeller pitch control (PPC) is mounted at the rear of the [engine’s] reduction gear section on the propeller shaft centerline. The PPC is composed of a ported sleeve, which is positioned by cam. The control end of the beta tube (which also has oil-supply ports) rides inside the ported sleeve. The positioning cam-control shaft is connected to the main metering valve power-lever shaft by mechanical linkage. During propeller-governing mode, the propeller pitch control serves no basic function other than oil passage and housing forthe beta tube. In beta-mode (under-speed governing) the propeller pitch control provides for operator control of propeller blade pitch angle. Operator control is accomplished by manually positioning the propeller pitch control cam. The beta tube oil supply holes are then aligned with the ported sleeve so that the pressure supplied to the propeller balances the propeller piston spring. During takeoff, the propeller governor controls propeller pitch. The only function the PPC has in propeller governing mode is to act as an oil passageway. The PPC and FCU main metering valve are connected through the concentric shaft and are rigged to move together. The cockpit power lever is connected to the splined end of the shouldered shaft of the PPC in the Grumman G-164B (AgCat) installation. The cockpit condition lever is connected to the propeller governor. According to Honeywell Service Bulletin TPE331-76-2002, a disengagement of the airframe PPC linkage will result in the pilot’s inability to change fuel flow and/or propeller pitch (blade angle) during flight and landing. 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 he departed DFI the pilot noticed that he forgot to bring his GPS and returned and landed at DFI. After retrieving the GPS, the pilot departed DFI a second time and flew to Charloe Airport (53OH), Paulding, Ohio, where he retrieved a hose connector before continuing to CQA. According to the pilot, there were no issues with the airplane or its engine during his preflight inspection or the repositioning flights. The accident occurred during the first agricultural flight of the day. Before departure, the retailer who sold the fungicide and insecticide loaded the water/product solution on the airplane while the pilot fueled the airplane with 27 gallons of Jet-A aviation fuel. The pilot estimated the fuel load at departure was about 80 gallons, and the water/product solution was likely about 330 gallons in total. The pilot stated that the loaded airplane was below the airplane’s maximum gross weight, and that he had previously flown the airplane with similar loads without any performance issues. The pilot back taxied on runway 8 at CQA and completed an uneventful engine runup before starting the takeoff roll. During the takeoff roll, the engine torque and propeller speed gauges indicated about 52 psi and 100%, respectively. The pilot stated that he did not perform a maximum-performance takeoff and a normal liftoff was achieved without any issues. The pilot reported that during the initial climb, about 20-75 ft above groundlevel, the airplane had a sudden fluctuation in engine power from high-power to low-power and back to high-power. The pilot stated that he was “thrown forward” into his safety restraints and then “thrown back” into his seat. The forward/backward motion only occurred once and was “pretty quick and hard.” The pilot stated that after the loss of engine power the propeller speed remained at 100% but the airplane’s climb performance was significantly diminished. He did not cross-check any other engine gauges. The pilot pitched the airplane for best glide airspeed and entered a slight right turn from the runway heading to avoid trees. Believing the engine was still running, the pilot did not want to jettison the airplane’s load unnecessarily into the river near the airport. The engine lost all power shortly after he entered the right turn. The pilot was wearing an active noise-canceling helmet, but he noticed there was a noticeable lack of engine noise, and that he only heard the wind passing outside the cabin. The pilot jettisoned the airplane’s load in an attempt to maintain a climb, but the airplane descended and impacted a levee, where it nosed over into the river. The airplane came to rest inverted on the bank of a small river. The airplane sustained substantial damage to the vertical stabilizer, rudder, upper wings, and the fuselage. Examination of the engine before it was removed from the airframe revealed that the airframe control linkage to the propeller pitch control (PPC) was disconnected from the splined end of the shouldered shaft of the PPC, and the retaining bolt was loose and was not secured by safety wire, as shown in figure 1. The PPC shouldered shaft did have an internally threaded hole, but there was no evidence that the secondary retention feature was installed at the time of the accident. The secondary retention feature is discussed in more detail in the Additional Information section. Postaccident engine examination and disassembly revealed rotational scoring at multiple locations, including the compressor impeller blades, impeller shroud, and propeller shaft. Light metal spray was adhered to the 3rd stage turbine stator vanes. Surfaces throughout the engine gaspath were coated with earthen debris. The torsion shaft aft spline was fractured 1.25 inches from the aft end. The disassembly and examination of the engine revealed no evidence of a preimpact failure or other anomalies that would have prevented normal operation. The engine fuel pump was unable to hold pressure during bench testing and was subsequently disassembled. The high-pressure gear stage carbon bushing was found fractured and, according to the engine manufacturer, is consistent with impact-related damage. Otherwise, the fuel pump examination was unremarkable. The fuel control unit (FCU) and propeller governor were tested and examined at the manufacturer. The FCU Standard Day Acceleration Schedule had significantly high out-of-limits fuel flow discharge at all testpoints and FCU pressure readings did not respond normally to speed input changes. The Deceleration Schedule fuel flow discharge readings were low out-of-limits during testing. All other schedules were within the expected range for similar service run units that have undergone customer adjustments. The FCU was disassembled and there was no evidence of internal failure. All springs were intact, and all bearings and levers moved freely. The propeller governor was bench tested, and all test points were consistent with similar service run units. The propeller remained attached to the engine propeller shaft flange, and all three blades remained attached to the propeller assembly. A counterweight puncture mark on the spinner dome was consistent with the propeller in the normal range of operation at about 24° blade angle at impact. There was no damage or evidence to indicate the propeller was feathered or in the beta/reverse range at the time of impact. All three blade shanks remained attached via the retention clamps and no pilot tubes were fractured. All three blades were fractured near the tip. The damage to the blades included chordwise/rotational scoring on both camber and face sides, bending opposite rotation, leading edge gouging with material deformation towards high pitch, and progressive compound bent/twisting, as shown in Figure 2. The propeller examination and disassembly revealed no evidence of a preimpact failure or other anomalies that would have prevented normal operation. All observed damage was consistent with high impact forces. Blade damage and impact signatures on the cylinder and spinner dome indicated the propeller was rotating in the normal blade angle range of operation at moderate power. Figure 1 – Airframe propeller pitch control (PPC) linkage disconnected from PPC splined shaft, and loose retaining bolt without safety wire (Honeywell Photo) Figure 2 – Propeller (Hartzell Propeller Photo)

## Aircraft

- Registration: [N8376K](https://openairdocs.org/deregistered/N8376K-2024-04-01), registration cancelled 2024-04-01, S/N 675B, built 1982 (OpenAirDocs)
- Reported make and model: GRUMMAN G164 (B)
- Registry model: [Grumman Acft ENG Cor-Schweizer G-164B](https://openairdocs.org/model/grumman-acft-eng-cor-schweizer-g-164b) (registry code 3952802) (OpenAirDocs)
- Registry engine: [Pratt & Whitney R1340 series](https://openairdocs.org/engine/pratt-whitney-r1340-series) (registry code 52016, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 675B
- Year built: 1982
- Airframe hours: 9187.2
- Engines: Honeywell TPE331-1-151A 665 horsepower turbo prop
- Damage: Substantial damage
- Flight: Aerial application, Part 137
- Operator: Gaerte Ag Service, LLC
- Registered owner: Gaerte Ag Service, LLC
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: Annual, May 20, 2021, 14.1 hours before
- Airport: KCQA, Lakefield Airport, runway 8, 4,400 × 75 ft, asphalt
- Equipment: Satellite tracking device

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 43; injuries: serious; commercial; airplane ratings: single-engine land; medical: class 2, with waivers/limitations; seat: single; restraint: 4-point; flight hours: 3,300 total, 1,350 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: 70° at 8 knots, gusting 15
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 57 °F, dew point 55 °F
- Altimeter: 30.15 inHg
- Observed at: KAXV, 11.9 nm away
- METAR: METAR KAXV 271155Z AUTO 07008G15KT 10SM 14/13 A3015 RMK AO2=

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 20210527010209A](https://openairdocs.org/incident/20210527010209A), May 27, 2021: Grumman Acft Eng Cor-Schweizer G-164B, Celina, OH, Substantial damage. N8376K, G-164-B, crashed into waterway 1 mi off end of rwy 8 at Celina (kcqa) shortly after take off. Aircraft stopped producing thrust after takeoff rotation…

## Other investigations on N8376K (2)

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

- [NTSB WPR11CA261](https://openairdocs.org/ntsb/WPR11CA261), Jun 15, 2011: Grumman Acft ENG Cor-Schweizer G-164B (N8376K), Pullman, WA, substantial damage. Probable cause: The pilot's failure to maintain clearance from power lines while maneuvering.
- [NTSB SEA06CA145](https://openairdocs.org/ntsb/SEA06CA145), Jul 23, 2006: Grumman-Schweizer G-164B (N8376K), Lamont, WA, substantial damage. Probable cause: The pilot's failure to maintain terrain clearance while maneuvering.

## Docket (18 files)

The files NTSB released with the investigation on August 16, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=103157.

- NTSB record of conversation (mark gaerte) (item 1, PDF, 3 pages, 91 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15873176&FileExtension=pdf&FileName=01%20-%20NTSB%20Record%20of%20Conversation%20(Mark%20Gaerte)-Rel.pdf
- FAA record of conversation (mark gaerte) (item 2, PDF, 2 pages, 89 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15869844&FileExtension=pdf&FileName=02%20-%20FAA%20Record%20of%20Conversation%20(Mark%20Gaerte)-Rel.pdf
- Ohio state highway patrol crash report (item 3, PDF, 7 pages, 724 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15869607&FileExtension=pdf&FileName=03%20-%20Ohio%20State%20Highway%20Patrol%20Crash%20Report_Redacted-Rel.pdf
- Honeywell examination summary (item 4, PDF, 17 pages, 29 photos, 1.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15869962&FileExtension=pdf&FileName=04%20-%20Honeywell%20Examination%20Summary-Rel.pdf
- Hartzell propeller examination report (item 5, PDF, 15 pages, 16 photos, 3.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15869172&FileExtension=pdf&FileName=05%20-%20Hartzell%20Propeller%20Examination%20Report_Redacted-Rel.pdf
- NTSB powerplants factual report (item 6, PDF, 22 pages, 23 photos, 2.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15870472&FileExtension=pdf&FileName=CEN21LA237-%20Powerplants%20Group%20Chair_s%20Factual%20Report%20(Final-Docket)-Rel.pdf
- Powerplants attachment 2- woodward propeller governor teardown report and as received test run sheets (item 7, PDF, 4 pages, 516 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15195646&FileExtension=pdf&FileName=CEN21LA237-%20Powerplants%20Attachment%202-%20Woodward%20Propeller%20Governor%20Teardown%20Report%20and%20As%20Received%20Test%20Run%20Sheets-Rel.pdf
- Powerplants attachment 1- woodward fuel control teardown report and as received test run sheets (item 8, PDF, 10 pages, 2.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15196029&FileExtension=pdf&FileName=CEN21LA237-%20Powerplants%20Attachment%201-%20Woodward%20Fuel%20Control%20Teardown%20Report%20and%20As%20Received%20Test%20Run%20Sheets-Rel.pdf
- Airframe logbook (excerpts) (item 9, PDF, 15 pages, 3.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15870516&FileExtension=pdf&FileName=09%20-%20Airframe%20Log%20(Excerpts)_Redacted-Rel.pdf
- Engine logbook (excerpts) (item 10, PDF, 11 pages, 5.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15868959&FileExtension=pdf&FileName=10%20-%20Engine%20Log%20(Excerpts)_Redacted-Rel.pdf
- Propeller logbook (excerpts) (item 11, PDF, 7 pages, 2.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15870670&FileExtension=pdf&FileName=11%20-%20Propeller%20Log%20(Excerpts)_Redacted-Rel.pdf
- Honeywell TPE331 engine overhaul manual (engine controls description) (item 12, PDF, 6 pages, 274 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15870868&FileExtension=pdf&FileName=12%20-%20Honeywell%20TPE331%20Engine%20Overhaul%20Manual%20(Engine%20Controls%20Description)-Rel.pdf
- FAA AD 2020A��26A��14 (released 29 dec 2020) (item 13, PDF, 8 pages): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15870305&FileExtension=pdf&FileName=13%20-%20FAA%20AD%202020%E2%80%9026%E2%80%9014%20(Released%2029%20DEC%202020)-Rel.pdf
- FAA AD 2023A��08A��07 (released 17 may 2023) (item 14, PDF, 7 pages, 3.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15870833&FileExtension=pdf&FileName=14%20-%20FAA%20AD%202023%E2%80%9308%E2%80%9307%20(Released%2017%20MAY%202023)-Rel.pdf
- Weather summary (item 15, PDF, 2 pages, 101 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15902277&FileExtension=pdf&FileName=15%20-%20Weather%20Summary-Rel.pdf
- Photos (item 16, PDF, 6 pages, 6 photos, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15871543&FileExtension=pdf&FileName=16%20-%20Photos-Rel.pdf
- Honeywell service bulletin TPE331-76-2002 (excerpt) (item 17, PDF, 1 page, 74 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15919693&FileExtension=pdf&FileName=17%20-%20Honeywell%20Service%20Bulletin%20TPE331-76-2002%20(Excerpt)-Rel.pdf
- Statement of party representatives to NTSB investigation (item 18, PDF, 3 pages, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15931063&FileExtension=pdf&FileName=18%20-%20NTSB%20Party%20Forms%20(CEN21LA237)_Redacted-Rel.pdf

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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