# NTSB WPR21LA299: Schweizer G-164B, N3629F, Tracy, CA, July 30, 2021 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: July 30, 2021, 14:23 local (21:23 UTC) - Place: Tracy, CA - Coordinates: 37.84131, -121.52415 - Nearby events: https://openairdocs.org/map.md?lat=37.8413&lon=-121.5242&mi=10 - Phase of flight: [Emergency descent](https://openairdocs.org/ntsb-phases/600) (OpenAirDocs' grouping) - Defining event: [Emergency descent: Unknown or undetermined](https://openairdocs.org/ntsb-events/000) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: Honewell, Federal Aviation Administration, Hartzell - NTSB case key (mKey): 103594 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR21LA299 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/103594/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=103594 - Page: https://openairdocs.org/ntsb/WPR21LA299 ## Probable cause A loss of thrust during a low-level agricultural application flight, which resulted in a descent and impact with terrain. The reason for the loss of thrust could not be determined based on available information. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine (turbine/turboprop)](https://openairdocs.org/ntsb-findings/01057200): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Schweizer G-164B, 2 cases](https://openairdocs.org/ntsb-findings/01057200/cases.md?model=8059055), [All aircraft, 67 cases](https://openairdocs.org/ntsb-findings/01057200/cases.md) - [Engine (turbine/turboprop)](https://openairdocs.org/ntsb-findings/01057200): Aircraft › Aircraft power plant · Unknown/Not determined (probable cause); cases with it: [Schweizer G-164B, 2 cases](https://openairdocs.org/ntsb-findings/01057200/cases.md?model=8059055), [All aircraft, 67 cases](https://openairdocs.org/ntsb-findings/01057200/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering-low-alt flying: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341); cases with it: [Schweizer G-164B, 6 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=8059055), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Emergency descent: Unknown or undetermined](https://openairdocs.org/ntsb-events/000) (defining event); cases with it: [Schweizer G-164B, 4 cases](https://openairdocs.org/ntsb-events/000/sequence.md?model=8059055), [All aircraft, 1,703 cases](https://openairdocs.org/ntsb-events/000/sequence.md) ## Analysis The pilot reported that he was performing a low-level agricultural pesticide application on a hay field when the engine suddenly lost all power. Although the airplane was at a high airspeed at the time, the pilot was unable to climb due to the presence of high-tension powerlines above him in his flightpath. During the subsequent descent, he flew beneath a set of powerlines, turned, and landed in a field after his airspeed had decreased. During the landing, the airplane contacted the ground and trees, which resulted in substantial damage to the fuselage and wings. Postaccident examination of the engine and accessories did not reveal any mechanical anomalies that could have precluded normal operation. Evidence of rotational scoring and metal spray deposits in the engine indicate that it was operating at the time of impact. The fuel solenoid shutoff valve was in the CLOSED position, which would have prevented fuel flow to the engine. However, due to the overwhelming evidence that the engine was rotating at the time of impact, it is likely that the shutoff valve moved to the CLOSED position as a result of the impact. Propeller signatures indicated that the blades impacted the ground while rotating at low power. An examination of the propeller did not reveal any visible discrepancies that would have affected performance prior to impact. The damage to the start lock brackets, start lock plates, and a contact mark on the internal surface of the piston suggest the propeller was on or below the start lock angle at impact. This was likely the result of impact forces, as the pilot stated that he did not reduce throttle input or attempt to feather blades before impact. Previous maintenance indicated that the blade radius was properly set. The pilot did not recall the power lever position at the time of the power loss and the investigation did not reveal any evidence of preimpact mechanical malfunctions or failures. Therefore, the reason for the pilot’s reported loss of power could not be determined. ## Factual narrative On July 30, 2021, about 1423 Pacific daylight time, a Grumman G-164B airplane, N3629F, was substantially damaged when it was involved in an accident near Tracy, California. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight. The pilot reported that he was just beginning his 8th pass over a hay field that was located beneath high-tension power lines. He planned to repeat his previous passes by flying south below the high-tension power lines, which ran diagonally across the field (northeast to southwest) and the flightpath. When the pilot was about midway through the spray pass, he experienced a total loss of engine power accompanied by a vibration; however, the pilot could not recall if the vibration occurred before or after the power loss. The pilot stated that his airspeed was about 130 mph at the time of the power loss but was decaying rapidly. He was unable to enter a climb due to the power lines located overhead. The pilot flew about 10-15 ft above ground level under another set of power lines at the south end of the field to an adjacent field. He then began a shallow right tun to orient the airplane parallel to a series of raised dirt beds. However, during the turn the airplane contacted the ground and several trees. The wings and fuselage were substantially damaged. In a subsequent statement the pilot reported that he was likely running the engine at 70-80% of full power as he was nearing the end of the load at the time and did not require a high power setting. The pilot could not recall the exact position of the power lever. Engine Examination Postaccident examination of the engine revealed that the engine’s rotating group rotated with some resistance but was free to rotate after the planetary gear assembly was removed from the nose cone assembly. Continuity of the direct drive fuel control drive train was confirmed from the fuel control drive shaft to the power shaft. Additionally, evidence of rotational scoring was observed in several locations including the propeller shaft, first stage compressor impeller, second stage compressor impeller, and to the entire turbine rotating group. Compressor shroud metal spray deposits were observed in several locations of the first, second, and third stage turbine rotor blades, and on the first, second, and third stage turbine rotor vanes. Accessory Testing Testing of the fuel control showed that the unit operated outside the manufacturer’s specifications in several areas including fuel flow, the flight idle setting, and various test points. However, according to the manufacturer, none of the tests that were beyond specifications would have been contributing factors in a loss of power event. Testing of the fuel pump also did not reveal any anomalies. The propeller governor was tested, and both the maximum rpm and minimum rpm were beyond their normal limitations. Additionally, the arm travel range was out of limits.According to the manufacturer, the test data were the results of typical adjustments made to the propeller governor in the field and the operational testing showed that the unit was functioning properly at the time of the accident. Fuel Solenoid Shutoff Valve with Manual Override The engine was equipped with a fuel solenoid valve to introduce fuel to the engine when the speed switch is actuated during engine start and to cease fuel delivery when the stop switch is actuated. When the valve is open, fuel passes through a ball valve and out to the fuel atomizers. The manual override lever and shaft at the upper end of the valve is connected to the manual stop and feather lever in the cockpit. The valve can be opened and closed electrically but cannot be opened manually. An examination of the valve revealed that the scribe mark on the end of the override shaft was positioned at the top of the valve, consistent with an OPEN position. Low pressure air was applied to the fuel inlet port of the valve, which did not pass through the valve, consistent with the ball valve being in the CLOSED position. According to the manufacturer, the CLOSED position of the ball valve would prevent fuel flow to the engine fuel nozzles. The manufacturer noted that the closed position of the ball valve is inconsistent with the findings of metal spray in the turbine section, which indicates the engine was rotating and fuel was being delivered to the engine to generate a flame at the time of impact. However, according to the manufacturer, these opposing findings can only exist if the fuel shutoff valve closed at impact, either through pilot intervention, an electrical short, or inertial movement during the impact sequence. Removal of the beta tube required 18 – 18.5 turns, which was consistent with the turns required in another propeller/engine configuration and consistent with normal alignment. Propeller According to the propeller manufacturer, no visible discrepancies were noted that would have degraded normal operation prior to impact. The blades remained in their respective clamps and no slippage was noted. All three pilot tubes were intact and minimal blade-to-hub contact marks were observed. Some deformation was observed on one of the drive dowel holes in the direction of rotation. All three propeller blades exhibited chordwise/rotational scoring on the camber-side near the tip. Blade No. 2 displayed some S-bend characteristics and an approximately 3-inch-long tip fracture, which was not recovered. Blade Nos. 2 and 3 exhibited some bending opposite the direction of rotation and twisting towards the low pitch. Some scuffing and abrasions were present on each of the blade faces with no evidence of rotational scoring. Maintenance records showed that the propeller’s most recent overhaul took place in 2012. A work order from that overhaul showed that the blade angles were set to 30 inches radius, and the manufacturer noted this angle was consistent with published guidance.Lock Brackets, Start Lock Plates, and Piston All three start lock brackets were fractured and the start lock plates displayed signatures consistent with forceful impact with the start lock pin. According to the propeller manufacturer, the counterweight puncture in the spinner dome was consistent with a low blade angle when the spinner impacted terrain and the signatures on the start lock bracket indicated forceful contact in the high pitch direction. The start lock pins were actuated by a hand tool and when the blade/clamp assemblies were rotated only blade No. 2 would intermittently lock near the start lock angle. Both the blade No. 1 and blade No. 2 start lock plates passed by the displaced pin/bracket without locking. Marks on the piston/cylinder showed a mark about 1.85 inches from the bottom of the piston consistent with an approximate blade angle of -1° and a start lock angle of about 2.0°. Another mark located about 2.35 inches from the bottom of the piston was consistent with an estimated blade angle of about 15.6°. Finally, a mark about 1.9 inches from the top of the cylinder was consistent with an approximate blade angle of -1° to 0.7° and corresponded with the piston marks and the blade damage and near the start lock angle. ## Aircraft - Registration: [N3629F](https://openairdocs.org/deregistered/N3629F-2023-06-10), registration cancelled 2023-06-10, S/N 745B, built 1984 (OpenAirDocs) - Reported make and model: SCHWEIZER AIRCRAFT CORP G-164B - Registry model: [Schweizer G-164B](https://openairdocs.org/model/schweizer-g-164b) (registry code 8059055) (OpenAirDocs) - Registry engine: [Pratt & Whitney R1340 series](https://openairdocs.org/engine/pratt-whitney-r1340-series) (registry code 52016, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 745B - Year built: 1984 - Airframe hours: 197778 - Engines: Garrett/Honeywell TPE331-2 715 horsepower turbo prop - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Haley's Flying Service - Registered owner: Haley's Flying Service - Airworthiness certificate: Special, Restricted (Special) - Last inspection: 100 hour, July 12, 2021, 58 hours before - Departed: NA, Tracy, CA - Destination: NA, Tracy, CA - Airport: NA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 56; injuries: none; flight instructor, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review January 8, 2021; seat: single; restraint: 4-point; flight hours: 6,250 total, 2,300 in this make and model, 5,843 as pilot in command ## Weather - Conditions: Visual (VMC), Day - Wind: 320° at 11 knots, gusting 19 - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 104 °F, dew point 32 °F - Altimeter: 29.82 inHg - Observed at: TCY ## 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 20210730011559A](https://openairdocs.org/incident/20210730011559A), Jul 30, 2021: Schweizer Aircraft Corp G-164B, Tracy, CA, Substantial damage. Pilot was performing agriculture operations when he reported the engine suddenly vibrated and then stopped. The pilot was approaching two sets of high power… ## Other investigations on N3629F (1) 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 LAX00LA162](https://openairdocs.org/ntsb/LAX00LA162), Apr 20, 2000: Schweizer G-164B (N3629F), Lodi, CA, substantial damage. Probable cause: A loss of engine power for undetermined reasons. ## Docket (10 files) The files NTSB released with the investigation on June 8, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=103594. 12.7 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 10 pages, 3.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15276101&FileExtension=pdf&FileName=NTSB%20Accident%20Report%20N3629F_Redacted-Rel.pdf - Email correspondence with accident pilot (item 2, PDF, 4 pages, 172 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15277541&FileExtension=pdf&FileName=Email%20correspondence%20with%20pilot_Redacted-Rel.pdf - Aircraft logbooks (item 3, PDF, 9 pages, 6.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15304685&FileExtension=pdf&FileName=a%20logs%20redacted_Redacted-Rel.pdf - Propeller maintenance records (item 4, PDF, 3 pages, 592 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15277015&FileExtension=pdf&FileName=Propeller%20maintenance%20records_Redacted-Rel.pdf - Woodward propeller governor functional test report (item 5, PDF, 1 page, 15 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15276995&FileExtension=pdf&FileName=CSU%20SN%201110432%20OEINVST%201180359-Rel.pdf - Memorandum for record, Honeywell engine teardown report excerpt (item 6, PDF, 6 pages, 194 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15277395&FileExtension=pdf&FileName=Memorandum%20for%20record%20HWL-Rel.pdf - Fuel control unit functional test report (item 7, PDF, 2 pages, 15 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15277005&FileExtension=pdf&FileName=FCU%20SN%201478487%20OEINVST%201180358-1-Rel.pdf - Manufacturer propeller examination report (item 8, PDF, 11 pages, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15277096&FileExtension=pdf&FileName=prop%20exam%20report_Redacted-Rel.pdf - Statement of party representatives to NTSB investigation (item 9, PDF, 2 pages, 602 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15302508&FileExtension=pdf&FileName=party%20forms_Redacted-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 10, PDF, 2 pages, 123 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15277190&FileExtension=pdf&FileName=Release%20of%20Wreckage_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. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.