NTSB Identification: WPR11LA391
14 CFR Part 91: General Aviation
Accident occurred Wednesday, August 17, 2011 in Cowiche, WA
Probable Cause Approval Date: 05/15/2012
Aircraft: LUSCOMBE 8A, registration: N1444K
Injuries: 2 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
During a training flight, the airplane's occupants heard a hammering sound accompanied by an airframe vibration and reduction in engine power. The certified flight instructor took control of the airplane from the student and began to initiate a return to the airport. He decided that it was unlikely that they would be able to safely return, and he elected to perform a forced landing into a field. The airplane landed hard.
Examination of the engine revealed that the exhaust valve head most likely separated from its stem during flight, resulting in catastrophic failure to its associated cylinder components. Discoloration within the rocker area, exhaust valve guide, and cooling fins was consistent with heat damage, most likely caused by a stuck or sticking exhaust valve. The engine was manufactured in 1948, and its serial number did not match any records on file with the manufacturer. The maintenance records did not reveal a complete history of the engine's total flight time.
The National Transportation Safety Board determines the probable cause(s) of this accident to be:
A partial loss of engine power during maneuvering flight due to an exhaust valve failure.
HISTORY OF FLIGHT
On August 17, 2011, about 1845 Pacific daylight time, a Luscombe 8A, N1444K, force landed into a field after a loss of engine power near Cowiche, Washington. Yakima Aerosport LLC operated the airplane under the provisions of Title 14 Code of Federal Regulations Part 91, as an instructional flight. The certified flight instructor (CFI) and student pilot were not injured; the airplane sustained substantial damage during the accident sequence. The local flight departed Yakima Air Terminal/McAllister Field, Yakima, Washington, about 1800. Visual meteorological conditions prevailed, and no flight plan had been filed.
The CFI reported that they departed Yakima with the intention of performing routine flight training. During performance of ground reference maneuvers, the CFI heard a hammering sound, accompanied by an airframe vibration. He took control of the airplane from the student, and began to initiate a return to Yakima. He stated that the engine continued to operate, but at reduced power. He decided that it was unlikely that they would be able to safely return to Yakima, and as such, elected to perform a forced landing into a crop field. The airplane landed hard, collapsing the main landing gear, and causing substantial damage to the fuselage.
The engine was examined at the accident site by an inspector from the Federal Aviation Administration (FAA). The upper chamber of the number three cylinder exhibited a circumferential crack, which passed through both spark plug bores, separating the upper portion of the head from the engine. Subsequent disassembly revealed that both the exhaust and intake valve heads had separated from their stems, with one of the valves remaining loose within the cylinder chamber. The valve head had sustained crush and bending damage. The remaining valve was not recovered and is assumed to have been ejected from the cylinder during flight. The piston crown and inner cylinder head had become obliterated, and exhibited multiple semicircular, valve-shaped indentations to their surfaces. The damage sustained to the valve stems and heads prevented an examination of their separation surfaces.
Examination of the rocker area revealed black deposits and dark discoloration of the exhaust valve guide and surrounding casting. The external cooling fins displayed green-colored discoloration around the area of exhaust valve.
According to the FAA inspector, the engine was of the C85-12 type, and manufactured in 1948. The engine data tag revealed a serial number of 30376, and a representative from Teledyne Continental Engines reported that no such engine number existed in their records.
Maintenance logbooks revealed that the engine was installed on the airplane in December 2010, about 40 flight hours prior to the accident. The logbooks recorded the total time of the engine at the time of the installation as, "unknown". The engine had undergone an oil change 29 flight hours prior to the accident.
Teledyne Continental Motors Service Bulletin M77-3 addresses the various grades of fuel approved for aircraft engines, and the potential for sticking valves when utilizing 100 low-lead aviation fuel in older series engines. The SB states that 100 low-lead is an acceptable alternative fuel for the C85 series engine, and goes on to indicate that when using this fuel, exhaust valve sticking can result from lead salt accumulation in the lubricating oil. Under such circumstances, an exhaust leak between the exhaust elbow flange and the exhaust port face is possible, resulting in localized cylinder head overheating and subsequent exhaust valve and guide distress. The SB further states that this condition can be reduced with regular oil changes, and by the replacement of the valves and guides with units which are more tolerant of lead contamination.
A flight instructor and his student escape serious injury after their small plane crashes in a hay field in Cowiche northwest of Yakima last night. Witnesses tell us what they saw and heard as the plane went down.
One witness who didn't want to appear on camera says last night he saw the plane skid about ten feet, before it came to a stop in the field.
The skid marks made by the small plane are clearly visible in the alfalfa field owned by Peggy Christenson. She and her grandson were in the yard when she heard the plane flying very low over the trees.
"Next thing I knew my grandson ran up to me and said 'Grandma, a plane just crashed in our hay field,'" says Christenson.
The pilot told the sheriff's office the single engine of his 1946 Luscombe 8A died, and he was forced to make a hard landing, which crumpled the plane's landing gear and damaged one wing.
The pilot, 63 year old Mike Butterfield of Cowiche, and his unidentified 18 year old student from Zillah, were able to make it out of the plane unharmed.
"They both jumped up with their arms up saying 'I'm OK I'm OK, and so we were just very relieved that no one was hurt," says Christenson.
Butterfield owns Yakima Aerosport at the Yakima Airport, and declined to talk to us about the accident.
The property owner tells us the pilot plans to have the plane removed from the field by late tonight.
The National Transportation Safety Board and the Federal Aviation Administration are investigating the plane crash.
HIGHLAND -- A small plane crashed in a field north of Cowiche Road in Highland Wednesday evening.
Authorities tell Action News a flight instructor and one student were on board the plane. The student was behind the wheel when there was engine trouble. The instructor took over and tried to make it to a nearby landing strip. They were unable to reach the strip, and landed the 1940's aircraft in the hay field, instead. No one was injured.
YAKIMA COUNTY NEWS RELEASE -- On August 17, 2011 at approximately 1845 hours the Yakima County Sheriff’s Office received a report of a possible airplane crash near the 100 block of North Cowiche Road. Units from the Yakima County Sheriff’s Office and Highland Fire responded to the area and located a single engine aircraft in an alfalfa field near the intersection of Summitview and North Cowiche Roads approximately 11 miles northwest of the Yakima Airport.
The pilot, 63 year old male from Cowiche and the 18 year old passenger from Zillah were uninjured and out of the plane when units arrived. The pilot reported that the plane, a 1946 Luscombe 8A had suffered an engine failure and he was forced to land. The plane made a hard landing which crumpled the landing gear and damaged one wing.
The incident has been reported to the National Transportation Safety Board and the Federal Aviation Administration for investigation.
The names of the pilot and passenger are not being released.
