# NTSB CEN11LA512: WSK PZL Mielec M-18A, N92640, Anderson, IN, July 25, 2011 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 25, 2011, 14:17 local (18:17 UTC) - Place: Anderson, IN - Coordinates: 40.147499, -85.540832 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=40.1475&lon=-85.5408&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-low-alt flying: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report August 29, 2013 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Honeywell, FAA-Indianapolis FSDO, Woodward - NTSB case key (mKey): 81239 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN11LA512 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/81239/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=81239 - Page: https://openairdocs.org/ntsb/CEN11LA512 ## Probable cause The fatigue failure of the propeller governor speeder spring, which resulted in the pilot’s inability to control engine output power. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Propeller system: propeller governor](https://openairdocs.org/ntsb-findings/01046122): Aircraft › Aircraft propeller/rotor · Failure (probable cause); cases with it: [WSK PZL Mielec M-18A, 1 case](https://openairdocs.org/ntsb-findings/01046122/cases.md?model=9810103), [All aircraft, 16 cases](https://openairdocs.org/ntsb-findings/01046122/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) (defining event); cases with it: [WSK PZL Mielec M-18A, 1 case](https://openairdocs.org/ntsb-events/341/sequence.md?model=9810103), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Landing-flare/touchdown: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [WSK PZL Mielec M-18A, 9 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=9810103), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The pilot was marking a field in preparation for an aerial application when he experienced what he thought was an engine failure. He stated that the engine was still running, but it was not producing power. The pilot pushed the power lever forward; the engine power did not increase, but the engine temperature increased. He stated that the engine was idling fast and that he forced the airplane into a bean field about 150 to 200 yards ahead of a tree line. The pilot ground looped the airplane before contacting the trees. A postaccident examination of the engine did not reveal any anomalies. A bench test of the propeller governor revealed that the maximum speed was above the nominal limit and the minimum speed was below the nominal limit. The control lever position was set higher than the specified position, which indicated that the governor had been adjusted in an attempt to regulate the propeller speed. X-rays and a teardown revealed that the propeller governor speeder spring was fractured. A metallurgical examination revealed a preexisting fatigue crack that, over time, resulted in the failure of the spring. The failed speeder spring would have resulted in a loss of oil pressure to the propeller piston, which allowed the propeller blades to rotate to a high blade angle, which then decreased the engine speed and overall power output of the engine. Maintenance records showed the propeller governor was overhauled on May 19, 2009. The speeder springs did not have serial numbers, and, therefore, the maintenance history of the speeder spring could not be determined. ## Factual narrative On July 25, 2011, at 1417 eastern daylight time, a WSK PZL MIELEC M18A airplane, N92640, collided with the terrain near Anderson, Indiana, during an aerial application flight following a loss of engine power. The airline transport rated pilot was not injured. The airplane was substantially damaged. The flight was being operated by Forest Air Services under 14 Code of Federal Regulations Part 137 without a flight plan. The local flight originated from Marion, Indiana, about 1335. The pilot stated he was beginning to mark his second field when the accident occurred. As he started the second marking pass, he experienced what he thought was an engine failure. He stated the engine was still running, but it was not producing power. He turned away from a nearby town and corn field, and located a bean field in which to land. The pilot pushed the power lever forward and the engine power did not increase, but there was an increase in engine temperature. He stated the engine was idling fast and he forced the airplane onto the ground about 150 to 200 yards prior to a tree line. The pilot ground looped the airplane prior to contacting the trees. The airplane was equipped with a Hartzell 5-bladed, hydraulically operated, constant speed propeller, model number HC-B5MP-5BL, hub serial number EVA3036. The blades contained varying degrees of impact damage. Impact marks between the link arms and the bottom of the blade counterweights indicated that the blades were not in either the feather or reverse position at impact. A postaccident inspection of the propeller did not reveal any failure or malfunction that would have precluded normal operation. The engine, a Honeywell model TPE331-11U-612G, serial number P44089C, was last installed on the accident airplane on October 28, 2009. The engine was shipped to Honeywell for a teardown inspection under the supervision of the Federal Aviation Administration. The teardown inspection did not reveal any failure or malfunction that would have precluded normal operation of the engine. The fuel control, fuel pump, propeller governor, fuel nozzles, and fuel manifold were removed for further testing. All of the components tested normally with the exception of the propeller governor which showed the minimum stop adjustment was out of limits. The governor was found to be delivering sufficient oil volume and pressure. The propeller governor, Woodward part number 897410-16, serial number 1758842 was subsequently examined at Woodward. A bench test of the governor revealed the maximum speed was 44 rpm above the nominal limit at the maximum control lever position of 112 degrees, and the minimum speed was 410 rpm below the nominal limit. The maximum control lever position, which should have been 84 +/- 5 degrees, was set at 112 degrees. The maximum speed to minimum speed control lever position was set at 30 degrees and it should have been set to 10.2 degrees. A non-Woodward lockwire was present on the control lever indicating thatadjustments had been made to the control lever position. The propeller governor was x-rayed. The x-ray appeared to show a fracture of the speeder spring, part number 1522-666. Two of the spring coils were in contact with each other near the spring seat. Disassembly of the governor revealed the speeder spring was fractured at a point 1-1/2 to 1-3/4 coils from the end of the spring. A metallurgical examination of the speeder spring revealed the fracture was a result of a fatigue crack which propagated through the fracture surface. Contact marks were visible between the coils. The depth and wear of marks on the contacting surfaces of the coil adjacent to the fracture indicate the spring continued to function after the fracture was initiated. The surface finish of the spring adjacent to the fracture origins contained pitted areas. Maintenance records show the propeller governor was overhauled on May 19, 2009. Speeder springs do not contain serial numbers and therefore the history of the fractured spring could not be determined. Further testing on an exemplar spring was performed by Woodward to determine the change in load rating of the spring at a condition where wear was occurring before and after the fracture occurred. This was accomplished by measuring the spring both prior to and after an electrical discharge machine cut through 90 percent of the coil. Prior to the cut with an applied load of 8 pounds, the spring length was measured at 1.1842 inches; with a 16 pound load, the spring length was 1.0707 inches. Following the cut with the same loads applied, the spring length was 1.1657 inches and 1.0642 inches respectively. In addition, it was calculated that, during the time the crack was present, but prior to complete failure, the resulting governor speed output would have been 244 rpm (6.5 percent) lower than with a non-cracked spring. This value would would be an additional 2.7 percent lower in speed. ## Aircraft - Registration: [N92640](https://openairdocs.org/deregistered/N92640-2022-05-11), registration cancelled 2022-05-11, S/N 1Z025-22 (OpenAirDocs) - Reported make and model: WSK PZL MIELEC M-18A - Registry model: [WSK PZL Mielec M-18A](https://openairdocs.org/model/wsk-pzl-mielec-m-18a) (registry code 9810103) (OpenAirDocs) - Registry engine: [Wsk-Pzl-K PZL ASZ-62IR](https://openairdocs.org/engine/wsk-pzl-k-pzl-asz-62ir) (registry code 67203, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 1Z025-22 - Airframe hours: 2934 - Engines: Honeywell TPE331-11U-61 1000 horsepower turbo prop - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Forest Air Services Inc, doing business as Forest Air Services, Inc - Registered owner: Canam Aviators Inc - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, June 15, 2011 - Departed: Marion, IN - Destination: Marion, IN ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 61; injuries: none; airline transport, flight instructor, commercial, flight engineer; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review February 27, 2010; seat: center; flight hours: 21,000 total, 800 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 360° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 82 °F, dew point 72 °F - Altimeter: 29.95 inHg - Observed at: MIE, 12 nm away ## 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 20110725016629A](https://openairdocs.org/incident/20110725016629A), Jul 25, 2011: Wsk Pzl Mielec M-18A, Anderson, IN, Substantial damage. The aircraft lost power while completing a turn during spraying operations. The pilot stated that upon experiencing power loss, he leveled the wings and… ## Other investigations on N92640 (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 CEN10CA406](https://openairdocs.org/ntsb/CEN10CA406), Jul 10, 2010: WSK PZL Mielec M-18A (N92640), Muncie, IN, substantial damage. Probable cause: The pilot's failure to see and avoid the power line during an aerial application flight. - [NTSB LAX96LA113](https://openairdocs.org/ntsb/LAX96LA113), Feb 16, 1996: Wsk Pzl Mielec M-18-A (N92640), Blythe, CA, destroyed. Probable cause: the pilot's premature lift-off and subsequent loss of control due to his failure to monitor the airspeed indicator during the takeoff roll. ## Docket (14 files) The files NTSB released with the investigation on June 26, 2013, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=81239. 4.3 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 939 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40394662&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Parts Traceability Record (item 2, .PDF, 88 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40394663&FileExtension=.PDF&FileName=Parts%20Traceability%20Record-Redacted.PDF - Honeywell Governor Test Sheet (item 3, .PDF, 415 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40394664&FileExtension=.PDF&FileName=Honeywell%20Governor%20Test%20Sheet-Redacted.PDF - Woodward Governor Test Sheet (item 4, .PDF, 93 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40394665&FileExtension=.PDF&FileName=Woodward%20Governor%20Test%20Sheet-Redacted.PDF - Woodward Investigation Report (item 5, .PDF, 74 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40394666&FileExtension=.PDF&FileName=Woodward%20Investigation%20Report-Master.PDF - Woodward Material Laboratory Report (item 6, .PDF, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40394667&FileExtension=.PDF&FileName=Woodward%20Material%20Laboratory%20Report-Redacted.PDF - Woodward Operational Maintenance Manual Excerpt (item 7, .PDF, 104 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40394684&FileExtension=.PDF&FileName=Woodward%20Operational%20Maintenance%20Manual%20Excerpt-Master.PDF - Engine Data Download (item 8, .PDF, 157 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40394669&FileExtension=.PDF&FileName=Engine%20Data%20Download-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 9, .PDF, 263 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40394708&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF - Evidence Control Sheets (item 10, .PDF, 217 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40394701&FileExtension=.PDF&FileName=Evidence%20Control%20Sheets-Redacted.PDF - Photo 1. Propeller Governor (Woodwaard Photograph) (item 11, .PDF, 207 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40394671&FileExtension=.PDF&FileName=Photo%201.%20Propeller%20Governor%20(Woodwaard%20Photograph)-Master.PDF - Photo 2. Speeder Spring (Woodward Photograph) (item 12, .PDF, 215 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40394672&FileExtension=.PDF&FileName=Photo%202.%20Speeder%20Spring%20(Woodward%20Photograph)-Master.PDF - Photo 3. Speeder Spring (Woodward Photograph) (item 13, .PDF, 231 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40394674&FileExtension=.PDF&FileName=Photo%203.%20Speeder%20Spring%20(Woodward%20Photograph)-Master.PDF - Photo 4. Speeder Spring (Woodward Photograph) (item 14, .PDF, 133 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40394676&FileExtension=.PDF&FileName=Photo%204.%20Speeder%20Spring%20(Woodward%20Photograph)-Master.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.