# NTSB SEA98LA106: Schweizer G-164B, N7502C, Oakdale, WA, June 27, 1998 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: June 27, 1998, 06:30 local (13:30 UTC) - Place: Oakdale, WA - Coordinates: 47.119388, -117.249221 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=47.1194&lon=-117.2492&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report January 10, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 42805 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA98LA106 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/42805/pdf - Page: https://openairdocs.org/ntsb/SEA98LA106 ## Probable cause A fatigue failure of the number three cylinder exhaust rocker box assembly, compromising the ability of the exhaust valve to operate. Factors include a ditch at the end of the runway. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, takeoff - initial climb - engine assembly,other - failure (cause) - engine assembly,valve,exhaust - inoperative (cause) - Forced landing, descent - emergency - terrain condition - ditch (contributing factor) - On ground/water encounter with terrain/water, emergency landing - terrain condition - ditch (contributing factor) ## Analysis According to the pilot, during takeoff, approximately 10 feet above the ground, the aircraft started backfiring and losing power. He aborted the takeoff, but was unable to get the aircraft stopped before impacting a ditch just off the departure end of the airstrip. A post-accident inspection of the engine by an FAA Airworthiness Inspector found that a portion of the number three cylinder head casting through which the exhaust valve rocker pin passes had fractured. This allowed the number three cylinder exhaust valve to remain in the closed position during the time that it should have been open, resulting in a loss of power. The rocker box casting was sent to the NTSB metallurgical laboratory for further analysis. That examination revealed that the fracture in the casting was the result of a fatigue crack that originated in the wall of the hole in the casting through which the rocker arm pivot bolt passed. It could not be determined what caused the fatigue crack to initiate. ## Factual narrative On June 27, 1998, approximately 0630 Pacific daylight time, a Schweizer G-164B, N7502C, impacted a ditch during an aborted takeoff from a private agricultural airstrip near Oakdale, Washington. The commercial pilot, who was the sole occupant, was not injured, but the aircraft, which was owned and operated by Darrell Fender, of Colfax, Washington, sustained substantial damage. The attempted takeoff, which took place during visual meteorological condition, was for the purpose of a 14 CFR Part 137 aerial application flight. No flight plan had been filed, and there was no report of an ELT activation. According to the pilot, during takeoff, approximately 10 feet above the ground, the aircraft started backfiring and losing power. He therefore aborted the takeoff, but was unable to get the aircraft stopped before impacting a ditch just off the departure end of the airstrip. A post-accident inspection of the engine by an FAA Airworthiness Inspector found that a portion of the number three cylinder head casting through which the exhaust valve rocker pin passes had fractured. This allowed the number three cylinder exhaust valve to remain in the closed position during the time that it should have been open, resulting in a loss of power. As part of the investigation, the rocker box casting was sent to the NTSB metallurgical laboratory for further analysis. That examination revealed that the fracture in the casting was the result of a fatigue crack that originated in the wall of the hole in the casting through which the rocker arm pivot bolt passed. It could not be determined what caused the fatigue crack to initiate. ## Aircraft - Registration: [N7502C](https://openairdocs.org/aircraft/N7502C), registered now, S/N 817B, built 1989 (OpenAirDocs) - Reported make and model: Schweizer 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: 817-B - Airframe hours: 4048 - Engines: P&W 1340 600 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Derrell Fender - Registered owner: Darrell & Linda Fender - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Unknown, February 25, 1998, 347 hours before - Airport: Oakesdale ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 60; commercial; airplane ratings: single-engine sea, single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: center; flight hours: 19,400 total, 600 in this make and model, 200 in the last 90 days ## Weather - Conditions: Visual (VMC), Day - Wind: 180° at 5 knots - Visibility: 15 statute miles - Lowest ceiling: none ## 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 19980627015189A](https://openairdocs.org/incident/19980627015189A), Jun 27, 1998: Scwzer G164B, Oakdale, WA, Substantial damage. Lost power on takeoff. No further information. 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.