Narrative:

Aircraft X arrived at B-28 with write-up IRU left position deviation and/or residual ground speed is excessive. Crew comments: GS 16 KTS 3 hours in navigation. Used MEL reference 34 21B to defer the left IRU. While I was on the phone with dispatch; I received calls on the radio for B-26 items and also more B-28 items. I asked for help with this deferral several times but did not receive any help. I was told there were no right&east's available. The outcome of all this was that I missed the separate deferral on the GPWS reference the MEL reference 34 21B. Callback conversation with reporter revealed the following information: reporter stated whenever the left inertial reference unit (IRU) is deferred; the MEL also requires the deferral of the GPWS which includes windshear function.

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Original NASA ASRS Text

Title: A MECHANIC REPORTS MISSING A SEPARATE DEFERRAL ON THE GPWS AFTER DEFERRING THE LEFT INERTIAL REFERENCE UNIT (IRU) ON A B757-200 AIRCRAFT.

Narrative: ACFT X ARRIVED AT B-28 WITH WRITE-UP IRU L POS DEV AND/OR RESIDUAL GND SPD IS EXCESSIVE. CREW COMMENTS: GS 16 KTS 3 HRS IN NAV. USED MEL REF 34 21B TO DEFER THE L IRU. WHILE I WAS ON THE PHONE WITH DISPATCH; I RECEIVED CALLS ON THE RADIO FOR B-26 ITEMS AND ALSO MORE B-28 ITEMS. I ASKED FOR HELP WITH THIS DEFERRAL SEVERAL TIMES BUT DID NOT RECEIVE ANY HELP. I WAS TOLD THERE WERE NO R&E'S AVAILABLE. THE OUTCOME OF ALL THIS WAS THAT I MISSED THE SEPARATE DEFERRAL ON THE GPWS REF THE MEL REF 34 21B. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED WHENEVER THE LEFT INERTIAL REFERENCE UNIT (IRU) IS DEFERRED; THE MEL ALSO REQUIRES THE DEFERRAL OF THE GPWS WHICH INCLUDES WINDSHEAR FUNCTION.

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.