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Ia (inspection authorized mechanic) reported an small aircraft sel engine overhaul problem which resulted in the grounding of the aircraft.
| Attributes | |
| ACN | 264304 |
| Time | |
| Date | 199402 |
| Day | Thu |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : n81 |
| State Reference | NJ |
| Altitude | agl bound lower : 0 agl bound upper : 0 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tower : sat |
| Operator | general aviation : personal |
| Make Model Name | Any Unknown or Unlisted Aircraft Manufacturer |
| Operating Under FAR Part | Part 91 |
| Flight Phase | ground : parked other |
| Flight Plan | None |
| Person 1 | |
| Affiliation | Other |
| Function | other personnel |
| Qualification | other other : other pilot : commercial |
| Experience | flight time total : 3500 |
| ASRS Report | 264304 |
| Person 2 | |
| Affiliation | Other |
| Function | flight crew : single pilot |
| Qualification | pilot : private |
| Events | |
| Anomaly | non adherence other other anomaly other |
| Independent Detector | other other : unspecified |
| Resolutory Action | none taken : detected after the fact |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | other |
Narrative:
Aircraft engine (cont. T510-360-F) has only 267 hours from major overhaul with a history of #4 cylinder eating exhaust valves. This inspection, #4 cylinder compression test was 16/80 cold -- 20/80 hot. A list of unairworthy items on engine was given to owner. I feel that the cure is more than just replacing the valve. The engine is being returned again to the overhauler (columbia). I suspect cam lobe, but couldn't determine. Callback conversation with reporter revealed the following information: reporter stated that he had since learned that the valve push rods were found to be too long causing the valves not to seat properly. This would explain the lack of compression when the engine was cold and even after warming up. This was not a manufacturing defect since the engine had been overhauled. During overhaul, the push rods need to be either replaced with shorter ones or ground down to allow full seating since the valve seats have been ground down also for perfect seating which then requires a slightly shorter valve push rod. Subsequent inspection of the engine disclosed that the push rods were standard and not shorter than standard. However, the reporter does not necessarily agree with this finding since the valves are hydraulically operated which would allow for small difference in the valve push rod length. Of course, keep in mind that the manufacturer of the engine specifies that the rod length has to be adjusted when the valves are ground!
Original NASA ASRS Text
Title: IA (INSPECTION AUTHORIZED MECH) RPTED AN SMA SEL ENG OVERHAUL PROB WHICH RESULTED IN THE GNDING OF THE ACFT.
Narrative: ACFT ENG (CONT. T510-360-F) HAS ONLY 267 HRS FROM MAJOR OVERHAUL WITH A HISTORY OF #4 CYLINDER EATING EXHAUST VALVES. THIS INSPECTION, #4 CYLINDER COMPRESSION TEST WAS 16/80 COLD -- 20/80 HOT. A LIST OF UNAIRWORTHY ITEMS ON ENG WAS GIVEN TO OWNER. I FEEL THAT THE CURE IS MORE THAN JUST REPLACING THE VALVE. THE ENG IS BEING RETURNED AGAIN TO THE OVERHAULER (COLUMBIA). I SUSPECT CAM LOBE, BUT COULDN'T DETERMINE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT HE HAD SINCE LEARNED THAT THE VALVE PUSH RODS WERE FOUND TO BE TOO LONG CAUSING THE VALVES NOT TO SEAT PROPERLY. THIS WOULD EXPLAIN THE LACK OF COMPRESSION WHEN THE ENG WAS COLD AND EVEN AFTER WARMING UP. THIS WAS NOT A MANUFACTURING DEFECT SINCE THE ENG HAD BEEN OVERHAULED. DURING OVERHAUL, THE PUSH RODS NEED TO BE EITHER REPLACED WITH SHORTER ONES OR GND DOWN TO ALLOW FULL SEATING SINCE THE VALVE SEATS HAVE BEEN GND DOWN ALSO FOR PERFECT SEATING WHICH THEN REQUIRES A SLIGHTLY SHORTER VALVE PUSH ROD. SUBSEQUENT INSPECTION OF THE ENG DISCLOSED THAT THE PUSH RODS WERE STANDARD AND NOT SHORTER THAN STANDARD. HOWEVER, THE RPTR DOES NOT NECESSARILY AGREE WITH THIS FINDING SINCE THE VALVES ARE HYDRAULICALLY OPERATED WHICH WOULD ALLOW FOR SMALL DIFFERENCE IN THE VALVE PUSH ROD LENGTH. OF COURSE, KEEP IN MIND THAT THE MANUFACTURER OF THE ENG SPECIFIES THAT THE ROD LENGTH HAS TO BE ADJUSTED WHEN THE VALVES ARE GND!
Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.