Narrative:

Well; it all boiled down to: I got in a hurry; skipped a step and messed up. I noticed oil on the transmission deck. Upon further investigation I determined that the hydraulic pump was leaking. An L4 hydraulic pump had been ordered for another aircraft but ended up not needed; so it was returned to my inventory. I entered it into the parts inventory list but had not had time to put it on the shelf. I saw the pump on the desk; and decided to use it and not pull the other pump off the shelf. (Keep in mind that at this time I did not know that there was a difference in the L1/L3 and L4 pumps.) I looked at the bell ipb (illustrated parts breakdown) and noted the P/north's (part numbers) for the three o-rings and gasket. I saw two pumps in the illustration but the drawing showed a physical difference; so nothing flagged a problem in my mind since the two pumps I had were identical on the outside. I installed the pump and we (the pilot and myself) performed an [engine] run-up. Everything started well; but after about ten minutes of run the pilot noticed a whining noise coming from the upper deck. He shutdown and after checking things out we opted to try another run-up. The second run-up went just as well and no noise was noticed. We figured that there was an air bubble in the pump that had worked out upon shutdown; so with no operational check flight required; we put the bird (helicopter) back in service. I asked the pilot if he wanted to do a 'turn around the patch' but he didn't think it was necessary. The crew was dispatched on a flight around xa:30 the next morning. After flying about six miles from base the medical crew noticed a whining noise and expressed uneasiness with continuing the flight. The pilot turned the aircraft around and flew direct back to the hangar. About half way back to the hangar the pilot was able to hear the whining noise. I replaced the hydraulic pump with the pump on our parts shelf. During the change; I noticed the difference in P/north's and went back to the bell ipb and researched the difference in the pumps and realized the mistake I had made. I stopped everything and contacted our supervisor to see how I needed to proceeded from this point.the supervisor contacted bell and they determined that no damage was done to the aircraft and all I needed to do was to install the correct pump. I installed the correct pump and the aircraft has been working properly since.lessons learned: -don't just think you know something; check to be sure. -Always check all the parts in the ipb; not just the parts that you can't remember the P/north's-other than my shame and embarrassment; this situation turned out well; this same kind of mistake with other situations may have catastrophic results.

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Original NASA ASRS Text

Title: A Technician reports he noticed oil on the transmission deck of a Bell Long Ranger helicopter; but he got in a hurry and installed an incorrect hydraulic pump on the transmission. The Medical Crew and Pilot later noticed a whining noise coming from the upper deck. Helicopter returned to hangar base.

Narrative: Well; it all boiled down to: I got in a hurry; skipped a step and messed up. I noticed oil on the transmission deck. Upon further investigation I determined that the hydraulic pump was leaking. An L4 Hydraulic pump had been ordered for another aircraft but ended up not needed; so it was returned to my inventory. I entered it into the Parts Inventory List but had not had time to put it on the shelf. I saw the pump on the desk; and decided to use it and not pull the other pump off the shelf. (Keep in mind that at this time I did not know that there was a difference in the L1/L3 and L4 pumps.) I looked at the Bell IPB (Illustrated Parts Breakdown) and noted the P/N's (Part Numbers) for the three o-rings and gasket. I saw two pumps in the illustration but the drawing showed a physical difference; so nothing flagged a problem in my mind since the two pumps I had were identical on the outside. I installed the pump and we (the Pilot and myself) performed an [engine] run-up. Everything started well; but after about ten minutes of run the Pilot noticed a whining noise coming from the upper deck. He shutdown and after checking things out we opted to try another run-up. The second run-up went just as well and no noise was noticed. We figured that there was an air bubble in the pump that had worked out upon shutdown; so with no Operational Check Flight required; we put the bird (helicopter) back in service. I asked the Pilot if he wanted to do a 'turn around the patch' but he didn't think it was necessary. The crew was dispatched on a flight around XA:30 the next morning. After flying about six miles from Base the Medical Crew noticed a whining noise and expressed uneasiness with continuing the flight. The Pilot turned the aircraft around and flew direct back to the hangar. About half way back to the hangar the Pilot was able to hear the whining noise. I replaced the hydraulic pump with the pump on our Parts shelf. During the change; I noticed the difference in P/N's and went back to the Bell IPB and researched the difference in the pumps and realized the mistake I had made. I stopped everything and contacted our Supervisor to see how I needed to proceeded from this point.The Supervisor contacted Bell and they determined that no damage was done to the aircraft and all I needed to do was to install the correct pump. I installed the correct pump and the aircraft has been working properly since.Lessons learned: -Don't just think you know something; check to be sure. -Always check all the parts in the IPB; not just the parts that you can't remember the P/N's-Other than my shame and embarrassment; this situation turned out well; this same kind of mistake with other situations may have catastrophic results.

Data retrieved from NASA's ASRS site as of April 2012 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.