A repair shop mechanic describes the events that led to the discovery that unapproved chrome cylinde...

Narrative:

Customer brought aircraft to me with a complaint of high oil consumption. I performed a differential cylinder compression test with all cylinders reading in the 70's. The only problem I could find was oil on the bottom plugs in the number 1 and number 2 cylinders. At the owner's request; I removed the number 1 and number 2 cylinders and delivered them to engine shop X; an [far] 145 engine repair station in ZZZ1. Shop X repaired the cylinders in question knowing the model of the engine and the model cylinders they where repairing. They delivered them to me with yellow [serviceability] tags and I re-installed them in the original number 1 and number 2 position. This was in october 2012. After (4) to (8) hours of operation; the cylinders were still using oil so the owner of the airplane; who is also an airframe/powerplant (a/P) mechanic; removed them to verify I had the rings installed correctly. The engine was near time between overhaul (tbo) so the owner had been looking at options of a complete overhaul or just a top overhaul so he had the cylinder part numbers fresh in his mind. While we where discussing the situation over the phone in november 2012; he noticed the part numbers on the yellow tags supplied by engine shop X; did not match the part numbers for the engine in the parts manual. In researching the logbooks; we learned another a/P had installed lw-11633 cylinders on the engine almost 24-years ago. This cylinder is used on the later series engines but not approved for the 0-235-C2C. I had no reason to suspect the cylinders I removed from the engine were the wrong cylinders for the engine. The engine shop did not catch the problem when they repaired the cylinders and I again had no reason to suspect a problem. I re-installed the cylinders on the engine and signed the engine off as eligible for return to service. The solution to this would be to suspect part numbers of anything removed from an airplane.

Original NASA ASRS Text

Title: A Repair Shop Mechanic describes the events that led to the discovery that unapproved chrome cylinders had been installed on a Grumman AA1 aircraft's Lycoming 0-235-C2C engine; approximately 24 years earlier.

Narrative: Customer brought aircraft to me with a complaint of high oil consumption. I performed a Differential Cylinder Compression Test with all cylinders reading in the 70's. The only problem I could find was oil on the bottom plugs in the Number 1 and Number 2 cylinders. At the owner's request; I removed the Number 1 and Number 2 cylinders and delivered them to Engine Shop X; an [FAR] 145 Engine Repair Station in ZZZ1. Shop X repaired the cylinders in question knowing the model of the engine and the model cylinders they where repairing. They delivered them to me with yellow [Serviceability] tags and I re-installed them in the original Number 1 and Number 2 position. This was in October 2012. After (4) to (8) hours of operation; the cylinders were still using oil so the owner of the airplane; who is also an Airframe/Powerplant (A/P) Mechanic; removed them to verify I had the rings installed correctly. The engine was near Time Between Overhaul (TBO) so the owner had been looking at options of a complete overhaul or just a top overhaul so he had the cylinder part numbers fresh in his mind. While we where discussing the situation over the phone in November 2012; he noticed the part numbers on the yellow tags supplied by Engine Shop X; did not match the part numbers for the engine in the Parts Manual. In researching the logbooks; we learned another A/P had installed LW-11633 cylinders on the engine almost 24-years ago. This cylinder is used on the later series engines but not approved for the 0-235-C2C. I had no reason to suspect the cylinders I removed from the engine were the wrong cylinders for the engine. The Engine Shop did not catch the problem when they repaired the cylinders and I again had no reason to suspect a problem. I re-installed the cylinders on the engine and signed the engine off as eligible for return to service. The solution to this would be to suspect part numbers of anything removed from an airplane.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	1050182
Time
Date	201211
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	Yankee AA1
Operating Under FAR Part	Part 91
Flight Phase	Parked
Component
Aircraft Component	Cylinder Head
Person 1
Function	Technician
Qualification	Maintenance Powerplant Maintenance Airframe
Experience	Maintenance Lead Technician 3
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural Published Material / Policy

A repair shop mechanic describes the events that led to the discovery that unapproved chrome cylinders had been installed on a grumman AA1 aircraft's lycoming 0-235-C2C engine; approximately 24 years earlier.