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Having a screw loose.

When I got to work that day, I had no idea that my squadron would discover a discrepancy for which there were no checklists, Interactive Electronic Technical Manuals (IETMS) specifications, or inspection criteria. I thought it would be just like any other day, as an Airframes Collateral Duty Inspector (CDI). Usually, I am called on to do everything from phase maintenance, to assisting with the troubleshooting of pilot discrepancies on Functional Check Flights (FCF). On this day I was working as a troubleshooter on a post phase aircraft, helping out where I could and trying to finish signoffs as efficiently as possible so that we could get this aircraft flying again.

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So far the aircraft's progress was slow but steady. There were a few discrepancies that were being corrected by other shops but the ground turns were progressing rapidly. After the last set of ground turns, the pilots had a discrepancy of feedback chatter in the flight controls. Normally the cause of such a discrepancy is basic and relatively easy to troubleshoot. But just to make sure I didn't miss anything, I headed out to the aircraft and opened the hydraulics bay to see if anything unusual jumped out at me.

As hydraulic power was applied I watched the flight controls move through their entire range of motion. Initially I'd thought that a faulty pump may have been the culprit when, out of the corner of my eye, I saw a movement that didn't make sense. Upon closer inspection, I noticed the entire pilot assist servo base plate shifting back and forth as the flight controls moved. There are eight bolts that should have held the base plate tightly against the skin of the aircraft. Instead, the bolts were loose and the plate was rubbing back and forth on the airframe, easily visible to the eye. Needless to say this was NOT supposed to happen.

Realizing that although this was not the cause of the original flight control discrepancy, it was a serious problem that needed immediate attention. When I tried to look up inspection criteria and torque specifications for the attachment bolts, I came up short. I couldn't find any amplifying information anywhere in IETMS or any other inspection cards. After additional research, the inspection of the base plate is not called for in any inspection cycle, either at the squadron or depot level. The only time the bolts are ever inspected is during initial production at the plant. This aircraft had flown over 3,200 hours and there was a distinct possibility that the base plate had never been reinspected.

Luckily, the damage to the aircraft was slight because the discrepancy was discovered early. Had it continued, abrasions to the airframe would have continued and likely caused a separation or catastrophic failure of the flight controls. Fortunately, insufficient time had passed and only minor abrasion and surface corrosion had occurred where the plate was slipping.

The original flight control feedback gripe was later corrected, even though it was unrelated to the shifting base plate. The aircraft was once again up and flying and my fellow maintainers and I were all the wiser in discovering a gap in the time tested maintenance inspection cycle. The experience emphasized the importance of the maintenance troubleshooter. For every discrepancy, even the seemingly insignificant ones, avoid jumping to conclusions and take a deep breath before you turn a wrench or replace a component. Focusing my attention on the surrounding area and looking for "anything out of the ordinary" allowed me to identify a potentially hazardous situation. Following the incident, my new mantra is, "If you expect the unexpected, you will never be surprised".

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1) Specific publication within the IETM: A1-H60RA-450-300 WP 01300.

2) Table of Content path within the IETM: MH-60R\Hydraulic Power Systems\Hydraulic Power System\Pilot-Assist Module Manifold and Base Plate\Procedure.

AM3(AW) Pecoraro is a CDI at HSC-85 on NAS North Island
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Author:Pecoraro, Michael
Publication:Mech
Geographic Code:1USA
Date:Mar 22, 2012
Words:657
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