Narrative:

While prepping new nh speed sensor for installation on #1 engine; I noticed that the o-ring obtained from stores seemed small. I called back to the office and verified with my lead the part number marked on the bag with the ipc. Once verified that the part numbers were correct; I installed the nh sensor on the #1 engine. I then ground ran the engine to verify proper operation. A leak check was performed; and no oil leaks were noted at the time. The event happened at the aircraft maintenance hardstand in ZZZ; the weather was driving snow; and it was dark out. It was determined an event had occurred when a line check was performed on the aircraft a week later; as the same fault code that drove the original nh speed sensor change recurred. The mechanic correcting the issue found oil leaking from the sensor. When verifying the part number with my lead; I noticed that the air carrier expendable parts tag was placed directly over the printed part information on the paper packaging. To my knowledge; the part number on the parts tag was the correct one. If the parts tag had been placed on the other side of the package; I would have been able to see that the numbers did not match. Ensure that store verifies the part numbers on the packaging and the parts tags they place on our parts. Callback conversation with reporter revealed the following information: reporter stated the PW150A engines used on their dhc-8-400's have two nh speed sensors mounted on the high pressure compressor case. The two sensors function as channel 'a' and 'B' and send compressor rotational speed signals to the engine fadec system; which in turn sends a signal to the cockpit single EICAS display screen with a percentage indication of rotation.

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Original NASA ASRS Text

Title: Approximately one week after replacing a NH speed sensor on a PW150A for the #1 engine on a DHC-8-400; Mechanic is informed the same speed sensor was found leaking oil.

Narrative: While prepping new NH speed sensor for installation on #1 engine; I noticed that the O-ring obtained from stores seemed small. I called back to the office and verified with my Lead the part number marked on the bag with the IPC. Once verified that the part numbers were correct; I installed the NH sensor on the #1 engine. I then ground ran the engine to verify proper operation. A leak check was performed; and no oil leaks were noted at the time. The event happened at the aircraft maintenance hardstand in ZZZ; the weather was driving snow; and it was dark out. It was determined an event had occurred when a line check was performed on the aircraft a week later; as the same fault code that drove the original NH speed sensor change recurred. The Mechanic correcting the issue found oil leaking from the sensor. When verifying the part number with my Lead; I noticed that the Air Carrier Expendable parts Tag was placed directly over the printed part information on the paper packaging. To my knowledge; the part number on the parts tag was the correct one. If the parts tag had been placed on the other side of the package; I would have been able to see that the numbers did not match. Ensure that Store verifies the part numbers on the packaging and the parts tags they place on our parts. Callback conversation with Reporter revealed the following information: Reporter stated the PW150A engines used on their DHC-8-400's have two NH speed sensors mounted on the high pressure compressor case. The two sensors function as channel 'A' and 'B' and send compressor rotational speed signals to the engine FADEC system; which in turn sends a signal to the cockpit single EICAS display screen with a percentage indication of rotation.

Data retrieved from NASA's ASRS site as of May 2009 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.