# NTSB LAX97LA261: Classic Waco YMF, N369BP, Sedona, AZ, July 26, 1997 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 25, 1997, 19:09 local (Jul 26, 1997, 02:09 UTC) - Place: Sedona, AZ - Coordinates: 34.940219, -111.939628 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.9402&lon=-111.9396&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 3 uninjured - Status: Completed, report June 9, 1999 - Report: Approved by Office Director - NTSB case key (mKey): 29852 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX97LA261 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/29852/pdf - Page: https://openairdocs.org/ntsb/LAX97LA261 ## Probable cause A partial loss of engine power due to a loose rocker arm adjustment nut on the number 6 cylinder. The loose adjustment nut was due to inadequate maintenance adjustment performed by the engine manufacturer. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(partial) - mech failure/malf, cruise - engine assembly,rocker arm/tappet - loose (cause) - maintenance,adjustment - inadequate, manufacturer (cause) - engine assembly,valve,exhaust - not engaged (cause) - Forced landing, emergency descent/landing - On ground/water collision with object, landing - roll - object - utility pole ## Analysis During a local sightseeing flight, the engine started running rough. The pilot began a turn back toward the airport and noticed a decrease in power, which continued to escalate. He was unable to maintain altitude and selected a road to attempt a forced landing. During the landing, the airplane's right wing struck a telephone junction box. An exam revealed that the number 6 cylinder exhaust valve rocker arm adjustment nut was loose and the exhaust valve was not functioning. Review of the maintenance records disclosed that the valves were adjusted at the factory about 5 months and 200 hours prior to the accident. ## Factual narrative On July 25, 1997, at 1909 hours mountain standard time, a Classic Aircraft Waco YMF, N369BP, collided with a signpost during the ground roll portion of an emergency landing on a roadway near Sedona, Arizona. The forced landing was precipitated by a partial loss of engine power during cruise. The aircraft sustained substantial damage, and the pilot and two passengers were not injured. The aircraft was operated by Red Rocks Bi-Plane Tours of Sedona as a for-hire sightseeing flight under 14 CFR Part 91 when the accident occurred. The flight originated in Sedona at 1845 on the day of the accident. Visual meteorological conditions prevailed and no flight plan was filed. The pilot stated that approximately 10 minutes into the flight he noticed roughness in the engine and turned back towards the airport. Shortly thereafter he noticed a decrease in power, which continued to escalate. When the power reached a point that he was unable to maintain altitude, he decided to attempt to find a suitable landing site and landed the aircraft on the centerline of a local roadway. He stated that approximately 100 feet into the rollout, about 60 mph, the right wing struck a telephone junction box. This caused the airplane to veer to the right. The airplane and engine were examined under the supervision of the Safety Board on July 31, 1997. Control continuity was established for the throttle, carburetor heat, and the mixture controls. The air intake screen was clean with no debris found. Both magnetos were examined and rotated, with sparks developed at each ignition lead. The number 6 cylinder exhaust valve rocker arm adjustment nut was found loose, and the valve would not operate with crankshaft rotation. Jacobs Engines, the manufacturer of the engine, was contacted for information on the effect of a nonoperational exhaust valve on the engine's ability to produce power. The representative reported that a nonoperational valve could effect power output; however, they had no test data to quantify the effects. A request was made to the company to perform a test cell run in an attempt to duplicate the problem and quantify the amount of power loss. Impact damage precluded use of the accident engine for the test. As of the submission of this report, the manufacturer had not been able to locate an engine to run on the test cell. Review of the aircraft maintenance records disclosed that the engine was returned to the factory on February 18, 1997, about 200 hours prior to the accident, for repair of a broken internal cluster gear. The logbook notes in that entry that the valves were readjusted at that time. Examination of all subsequent entries disclosed no record of valve adjustments. The aircraft and all associated components were turned over to the insurance company representing the owner on July 31, 1997. ## Aircraft - Registration: [N369BP](https://openairdocs.org/aircraft/N369BP), registered now, S/N F5-005, built 1987 (OpenAirDocs) - Reported make and model: Classic Aircraft Corp. WACO YMF - Registry model: [Classic WACO YMF](https://openairdocs.org/model/classic-waco-ymf) (registry code 2240101) (OpenAirDocs) - Registry engine: [Jacobs R755B series](https://openairdocs.org/engine/jacobs-r755b-series) (registry code 35007, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 005 - Airframe hours: 856 - Engines: Jacobs R755-2B 275 horsepower reciprocating - Damage: Substantial damage - Flight: Part 91 - Registered owner: Dakota Territory Tours Inc. - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, July 18, 1997, 9 hours before - Departed: SEZ, AZ - Flight plan: Company VFR - Airport: SEZ, Sedona ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 29; commercial, flight instructor; airplane ratings: single-engine sea, multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: rear; flight hours: 4,638 total, 1,539 in this make and model, 4,337 as pilot in command, 96 in the last 90 days, 45 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 180° at 10 knots - Visibility: 25 statute miles - Lowest ceiling: none - Temperature: 84 °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 19970725019679A](https://openairdocs.org/incident/19970725019679A), Jul 25, 1997: Waco YMF, Sedona, AZ, Substantial damage. Aircraft lost engine power and made emergency landing on a highway, hit a sign, ran into a ditch. (.4)during a local sightseeing flight, the engine started… 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.