# NTSB SEA01LA146: Rockwell S-2R, N4237X, Latah, WA, August 4, 2001 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: August 4, 2001, 11:45 local (18:45 UTC) - Place: Latah, WA - Coordinates: 47.240699, -117.109397 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=47.2407&lon=-117.1094&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report October 17, 2001 - Report: Approved by Office Director - Parties: Spokane FSDO - NTSB case key (mKey): 52989 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA01LA146 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/52989/pdf - Page: https://openairdocs.org/ntsb/SEA01LA146 ## Probable cause the failure of a cylinder head exhaust rocker shaft boss while the aircraft was performing aerial application. Factors include soft terrain and a drop-off in the field where the emergency landing took place. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power, maneuvering - aerial application - engine assembly,cylinder - cracked (cause) - On ground/water encounter with terrain/water, emergency landing - terrain condition - drop-off/descending embankment (contributing factor) - terrain condition - soft (contributing factor) ## Analysis During an aerial application flight, the number six cylinder exhaust valve rocker boss cracked, and the engine would not produce enough power to keep the aircraft airborne. The pilot therefore made an emergency landing in a nearby lentil field. Although the touchdown was uneventful, during the landing roll, the aircraft went over a slight rise and became temporarily airborne. When it touched down again its propeller dug into the soft terrain, and the aircraft was thrown sideways, collapsing the main gear and bending the left wing. ## Factual narrative On August 4, 2001, approximately 1145 Pacific daylight time, a Rockwell S-2R, N4237X collided with the terrain during a forced landing about three miles east of Latah, Washington. The commercial pilot, who was the sole occupant, was not injured, but the aircraft, which was owned and operated by the pilot, sustained substantial damage. The 14 CFR Part 137 agricultural application flight, which had been airborne for about 40 minutes, was being operated in visual meteorological conditions. No flight plan had been filed. There was no activation of an ELT. According to the pilot, he had just completed spraying a field, and was preparing to return to Tekoa, Washington, for refueling and reloading when the aircraft's engine started popping and running rough. Soon thereafter, the power output of the engine dropped to what the pilot thought was about 30 percent of normal. He therefore made a forced landing in a nearby field of mature lentils. Although the initial touchdown was uneventful, during the landing roll, the aircraft went off a slight rise and became momentarily airborne. When the aircraft touched down again, it was nose-low, resulting in the propeller coming in contact with the terrain. As the propeller dug into the soft terrain, the aircraft was thrown sideways, collapsing the main gear and bending the left wing. A post-accident inspection of the engine revealed that the exhaust valve rocker shaft boss on the number six cylinder had cracked. According to the FAA Inspector who monitored the inspection, with the boss cracked, the exhaust valve would not open, and the detonating fuel-air mixture backfired into the intake plenum. No other engine anomalies were discovered, and the age and total time of the cylinder could not be determined. ## Aircraft - Registration: [N4237X](https://openairdocs.org/deregistered/N4237X-2004-06-29), registration cancelled 2004-06-29, S/N 2008R, built 1974 (OpenAirDocs) - Reported make and model: Rockwell S-2R - Registry model: [Rockwell International S-2R](https://openairdocs.org/model/rockwell-international-s-2r) (registry code 7630202) (OpenAirDocs) - Registry engine: [Pratt & Whitney R1340 series](https://openairdocs.org/engine/pratt-whitney-r1340-series) (registry code 52016, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 2008R - Airframe hours: 6076 - Engines: P&W R1340 600 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial application, Part 137 - Registered owner: Gregory R. Faunce - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, March 26, 2001, 290 hours before - Departed: Tekoa, WA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 42; injuries: none; commercial; airplane ratings: single-engine land; medical: class 2, valid medical--w/ waivers/lim; seat: rear; flight hours: 4,956 total, 2,256 in this make and model, 4,889 as pilot in command, 240 in the last 90 days, 110 in the last 30 days, 4 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 25 statute miles - Lowest ceiling: none - Temperature: 75 °F ## 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 20010804020689A](https://openairdocs.org/incident/20010804020689A), Aug 4, 2001: Ayres S2R, Latah, WA, No damage. (-23) The pilot had just finished spraying a field with a pre-harvest topcoat of roundup when he noticed the engine lose power and start popping. He said he… ## Other investigations on N4237X (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 OAK76DVA81](https://openairdocs.org/ntsb/OAK76DVA81), Jul 30, 1976: Aero Comdr 600S2R (N4237X), Firebaugh, CA, substantial damage 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.