Lowell, ID, USA
N8805W
Piper PA-28-235
While in cruise flight, the aircraft's engine began to lose power, resulting in the pilot being unable to maintain his assigned altitude. Eventually the engine quit, and the pilot was forced to attempt a controlled crash in heavily forested mountainous terrain. A post-accident inspection determined that the number four exhaust valve had stuck in the fully open position, and that there was a build-up of valve guide material on the valve stem. An inspection of the aircraft logs revealed that the valve guides and stems had not been inspected in accordance with Lycoming Mandatory Service Bulletin 388C (not mandatory for aircraft operating under part 91) at the recommended 400 hour interval. It was also determined that the engine had been displaying symptoms typical of intermittent valve sticking (rough running for a few seconds immediately after start-up) prior to the accident flight and a number of other prior flights. The pilot, who was unaware that the rough running was possibly associated with sticking valves, had not taken the aircraft to an Airframe and Powerplant mechanic to determine the reason for the symptom.
HISTORY OF FLIGHT On May 9, 2005, approximately 1640 mountain daylight time, a Piper PA-28-235, N8805W, impacted the terrain about eight miles south of Lowell, Idaho. The private pilot, who was the sole occupant, received serious injuries, and the aircraft, which is owned and operated by the pilot, was destroyed. The 14 CFR Part 91 personal IFR cross-country flight, which departed Jackson Hole, Wyoming, about an hour and a half prior to the accident, was in an area of visual meteorological conditions at the time the accident sequence began. The pilot was on an IFR flight plan, and he was communicating with Seattle Air Route Traffic Control (Seattle Center). There was no report of an ELT activation. On the day of the accident, the pilot checked the en route weather both through the internet DUATS service and by contacting a FAA Automated Flight Service Station. He received a full standard briefing from the FAA, and then filed an IFR flight plan for the flight from Jackson Hole to Lewiston, Idaho. The flight departed Jackson Hole Airport at 1513, and after becoming airborne the IFR flight plan was activated. About one hour and fifteen minutes into the flight, while cruising at 16,000 feet, the pilot was handed off from Salt Lake Air Traffic Control Center to Seattle Air Traffic Control Center. About four minutes after the handoff, the pilot contacted the center controller and stated that he was unable to hold altitude. About one minute later, the controller cleared the flight to descend and maintain 14,000 feet. About two minutes after the flight was cleared to 14,000 feet, the controller advised the pilot that radar showed the aircraft to be at 13,200 feet. Seeing the pilot's inability to maintain altitude, the controller asked him if the aircraft had ice on it, and the pilot responded that he was negative ice, but that he was not getting the engine to "run properly." The controller immediately cleared the pilot to descend to as low as 12,000 feet, and then within 30 seconds the controller cleared him to as low as 9,000 feet, which he advised the pilot, was the lowest altitude that he could clear an IFR flight to. About one minute after clearing the pilot to as low as 9,000 feet, the controller asked the pilot if he had the carburetor heat on, to which the pilot replied that he did have it on, and that the engine was starting to run better. About 30 seconds after the pilot said that the engine was starting to run better, he transmitted that the engine had "resumed power." Then for about two minutes there were no further communications between the aircraft and Seattle Center, but two and one-half minutes after the pilot transmitted that the engine had resumed power, he transmitted that " Zero five Whiskey has lost power, declaring an emergency." At that point, the controller gave the pilot a vector to the nearest airport (13 miles), and asked the pilot for people and fuel on board figures. The pilot reported that there was one person on board, and that the aircraft had three hours of fuel remaining. Approximately 30 seconds later, with the aircraft at 46 degrees, 03.03 minutes North and 115 degrees, 30.24 minutes West, both radio and radar contact where lost. According to the pilot, after radio contact was lost, he switched fuel tanks at least once, cycled the magnetos, and adjusted the mixture, but he was unsuccessful in getting the engine to restart. He therefore looked for a suitable place for a forced landing in the mountainous terrain, but finding none available, he slowed the aircraft and flew it into the densely forested terrain in a controlled crash. In a post-crash interview with the NTSB, the pilot stated that although the engine had been running fine in flight, it had lately been running rough for the first few seconds after it was started. He attributed the rough running to the possibility of humidity in a magneto, or the fouling of a spark plug. He had not had the problem looked at by an Airframe and Powerplant mechanic (A&P). When asked by the IIC whether he was aware that rough running immediately after start up was often an indication of intermittent valve sticking, he said that he was not. METEOROLOGICAL INFORMATION The 1756 surface aviation weather report (METAR) at Lewiston, Idaho, which is located approximately 60 miles northwest of the accident site, indicated 10 statute miles visibility, light rain, 5,000 scattered, 7,000 broken, a temperature/dew point of 16/09 Celsius. According to the pilot, in the area where he lost power there was an overcast layer at 10,000 feet (7,000 feet above the ground), and a forward visibility of greater than 10 miles. As he descended after the power loss, he passed through the overcast layer, encountered some falling snow, but eventually entered any area of VFR conditions underneath the overcast. WRECKAGE AND IMPACT INFORMATION The aircraft impacted trees and dense brush at the 3,500 foot level of mountainous terrain at 46 degrees, 01.61 minutes North and 115 degrees, 33.91 minutes West. Although heavily damaged from the impact sequence, the entire aircraft came to rest at this location. Two days later, around 1400, the wreckage and pilot where located by search and rescue aircraft. After recovery from the accident site, the aircraft was transported to the facilities of Discount Aircraft Salvage, Deer Park, Washington, where, on May 18, a teardown inspection was performed on the airframe and engine. There was no evidence of non-impact anomalies or malfunctions in the airframe, and the only anomaly associated with the engine was limited to the number four cylinder. When that cylinder was removed for further inspection, it was determined that its exhaust valve was stuck firmly in the valve guide in the open position. A comparison of the position of the number four exhaust valve with the exhaust valves of the other cylinders when they were moved to their full open position revealed that the subject valve was stuck in a position where it was further open than it would be in normal operation. This over-open position is consistent with the valve initially sticking at its normal full-open position, which would leave the rocker and pushrod freely floating within their full range of movement, followed by the valve being impacted by the free-floating rocker after the rocker had been impacted by the free-floating pushrod moving at high velocity after it was struck by its associated rotating camshaft lobe. Although the intake valve from the number four cylinder was easily removed from its guide with no resistance, the stuck exhaust valve required repeated forceful blows with a hard plastic mallet and a metal drift before it could be dislodged. Once the valve was removed, an inspection of its stem revealed galling and the transfer of valve guide material onto the surface of the stem (see photo # 3). An inspection of the valve guide inner wall revealed a heavy build-up of carbon, and scratching/gouging of the wall in the area associated with the material build-up on the valve stem. As part of the inspection, a rotary wire bottlebrush attached to a hand drill was used to removed most of the carbon accumulation from the valve guide walls. After the carbon was removed from the valve guide walls, the valve was able to be reinserted with no resistance. The guide and stem were then dimensionally checked, and it was determined that both the guide and the stem were within serviceable limits. ADDITIONAL DATA AND INFORMATION Valve sticking in Lycoming reciprocating aircraft engines is a longstanding issue, and is addressed in Lycoming Mandatory Service Bulletin 388C and Lycoming Service Instruction 1485A. Mandatory Service Bulletin 388C, which according to Federal Aviation Administration regulations is not mandatory for aircraft operated under FAR Part 91, calls for all Lycoming reciprocating aircraft engines to be inspected at 400 hour intervals, or earlier if valve sticking is suspected. If the valve/guide do not pass the inspection, then corrective action is to be taken as defined in Service Instruction 1485A. Once the guides are replaced with the newer Hi-Chrome guides, inspection is called for at every 1,000 hours, half of the published TBO, or when valve sticking is suspected, whichever occurs first. Valve sticking is often associated with an engine that runs rough for a few seconds each time it is started up after being allowed to cool, especially during the first flight of the day (within the aviation community commonly referred to as "morning sickness"). The subject engine was overhauled in May of 2002, and at that time Engine Components Incorporated (ECI) cylinders were installed. Although Lycoming started using the new Hi-Chrome guides in 1998, ECI did not start installing them in their cylinders until June of 2003, one year after the rebuild of the subject engine. Therefore this engine, with the old style guides installed, had the potential for sticking valves as operational time accumulated on these cylinders, and it was still subject to the 400 hour inspection intervals. A review of the entries in the engine logbook since the engine overhauled revealed that the engine had accumulated 791 hours since the overhaul, and there was no entry indicating that it had undergone the aforementioned inspection or corrective action. The aircraft was released to Phoenix Aviation Managers on 6/21/05. At the time of the release, the wreckage was in storage at Discount Aircraft Salvage, Deer Park, Washington. .
The number four exhaust valve sticking in the open position during cruise flight. Factors include the pilot's failure to have an Airframe and Powerplant mechanic look at the engine after it had run rough immediately after start-up prior to this and a number of other flights, and no suitable terrain and a dense forest in the area where the loss of engine power occurred.
Source: NTSB Aviation Accident Database
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