# NTSB CEN12LA501: Beech H35, N4684D, Holly Lake Ranch, TX, August 1, 2012 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: August 1, 2012, 11:20 local (16:20 UTC) - Place: Holly Lake Ranch, TX - Coordinates: 32.697498, -95.207778 - Nearby events: https://openairdocs.org/map.md?lat=32.6975&lon=-95.2078&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-descent: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: Serious injuries - Injuries: 1 serious - Status: Completed, report November 6, 2013 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Continental Motors, Dallas FSDO - NTSB case key (mKey): 84539 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN12LA501 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/84539/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=84539 - Page: https://openairdocs.org/ntsb/CEN12LA501 ## Probable cause The incomplete maintenance performed by maintenance personnel, which resulted in a total loss of engine power. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Maintenance: repair](https://openairdocs.org/ntsb-findings/02062015): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Beech H35, 1 case](https://openairdocs.org/ntsb-findings/02062015/cases.md?model=1151520), [All aircraft, 99 cases](https://openairdocs.org/ntsb-findings/02062015/cases.md) - [Engine (reciprocating)](https://openairdocs.org/ntsb-findings/01058500): Aircraft › Aircraft power plant · Incorrect service/maintenance (probable cause); cases with it: [Beech H35, 1 case](https://openairdocs.org/ntsb-findings/01058500/cases.md?model=1151520), [All aircraft, 497 cases](https://openairdocs.org/ntsb-findings/01058500/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-descent: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Beech H35, 7 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=1151520), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Beech H35, 3 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=1151520), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Maneuvering: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Beech H35, 8 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=1151520), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The airplane’s engine lost power during the descent to the destination airport, and the airplane struck trees during the ensuing forced landing attempt. A postaccident examination of the engine revealed that the idler gear pin was not in position and no retaining bolts were found. Additionally, the nuts from the forward left, lower through bolt on the crankcase half and the forward left engine mount bolt were missing. A logbook entry indicated that the engine had been reassembled and re-installed on the airplane about 1 week before the accident due to a previous propeller strike. Based on the available information, it is likely that the improper assembly of the engine, specifically the omission of the idler gear pin retaining bolts, resulted in the idler gear falling out of its position and a subsequent complete loss of engine power. ## Factual narrative On August 1, 2012, about 1120 central daylight time, a Beech H35 airplane, N4684D, sustained substantial damage when it struck trees following a loss of engine power near Holly Lake Ranch, Texas. The pilot received serious injuries. The aircraft was registered to an individual and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a business flight. Visual meteorological conditions prevailed for the flight, which was not operated on a flight plan. The flight originated from the Wood County Airport (JDD), Mineola, Texas, about 1100, and was destined for the Gilmer Municipal Airport (JXI), Gilmer, Texas. The pilot reported that he performed a pre-flight run-up with no anomalies noted. He then departed JDD and climbed to 7,500 feet altitude en route to JXI. During the descent to JXI, at 6,500 feet altitude, the engine experienced a total loss of engine power. The pilot reported that he turned the airplane toward the Holly Lake Ranch Airport (16TE), and attempted an engine restart to no avail. The airplane struck trees off the end of runway 27 at 16TE. Examination of the airplane’s engine after recovery from the accident scene revealed that the idler gear pin was missing from the rear of the engine, and both nuts and washers were missing from the idler gear pin attachment studs. The idler gear pin was found in a plastic trash bag that contained smaller parts recovered from the wreckage site. The idler gear had fallen in to the rear crankshaft gear and damaged the rear crankshaft gear teeth. The nut was missing from the forward left side lower through bolt on the crankcase half. The nut was also missing from the forward left side engine mount bolt. Examination of the maintenance records revealed a piece of paper attached to the log book indicating that the engine was disassembled and inspected after a propeller strike. The crankshaft was turned 0.010 inches undersize and the engine was re assembled. The entry was dated July 25, 2012 and was signed by the pilot, who also held a mechanic certificate with airframe and powerplant ratings issued by the Federal Aviation Administration. According to manufacturer drawings, the aft crankshaft gear engaged the idler gear which in turn engaged both magneto drive gears. Without the idler gear in place the magnetos would cease to operate. ## Aircraft - Registration: [N4684D](https://openairdocs.org/deregistered/N4684D-2017-10-06), registration cancelled 2017-10-06, S/N D-4867, built 1956 (OpenAirDocs) - Reported make and model: BEECH H35 - Registry model: [Beech H35](https://openairdocs.org/model/beech-h35) (registry code 1151520) (OpenAirDocs) - Registry engine: [Continental O-470 series](https://openairdocs.org/engine/continental-o-470-series) (registry code 17026, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: D-4867 - Engines: CONT MOTOR O-470 SERIES 230 horsepower reciprocating - Damage: Substantial damage - Flight: Business, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: July 25, 2012 - Departed: JDD, Mineola, TX - Destination: JXI, Gilmer, TX - Airport: 16TE, Holly Lake Ranch Airport, runway 27, 2,700 × 30 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 63; injuries: serious; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 3, with waivers/limitations; last flight review February 12, 2012; seat: left; flight hours: 3,915 total, 162 in this make and model, 3,915 as pilot in command, 16 in the last 90 days, 9 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 210° at 8 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 91 °F, dew point 68 °F - Altimeter: 29.97 inHg - Observed at: JXI, 13 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 20120801021009A](https://openairdocs.org/incident/20120801021009A), Aug 1, 2012: Beech H35, Hawkins, TX, Destroyed. The pilot departed wood county airport (jdd) time unknown for fox stephens field (kjxi). (27.8 n. miles distance). Incurred engine trouble and diverted to… ## Docket (5 files) The files NTSB released with the investigation on August 26, 2013, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=84539. 4.9 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40399400&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Maintenance record entry (item 2, .PDF, 261 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40399401&FileExtension=.PDF&FileName=Maintenance%20record%20entry-Redacted.PDF - Diagram of engine accessory drive gear arrangement (item 3, .PDF, 60 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40399402&FileExtension=.PDF&FileName=Diagram%20of%20engine%20accessory%20drive%20gear%20arrangement-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 4, .PDF, 205 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40399410&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF - Engine manufacturer's report (item 5, .PDF, 3.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40399411&FileExtension=.PDF&FileName=Engine%20manufacturer%27s%20report-Redacted.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.