A line mechanic reports a deactivate isolation (iso) valve (15HQ) maintenance procedure in MEL 21-26...

Attributes
ACN	966574
Time
Date	201108
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	Parked
Component
Aircraft Component	Aircraft Cooling System
Person 1
Function	Technician
Qualification	Maintenance Powerplant Maintenance Avionics Maintenance Airframe
Experience	Maintenance Technician 25
Events
Anomaly	Aircraft Equipment Problem Critical

Narrative:

Avncs system fault [message] displayed on upper ECAM. Chronic issue. Tried to implement MEL 21-26E; deactivate isolation (iso) valve. The iso valve (24HQ) needs to be placed in the 'open' position. But the MEL 21-26E does not tell the aircraft maintenance technician (amt) to 'remove' the cannon plug from the iso valve (24HQ). The avionics equipment ventilation computer (aevc) test must be accomplished before each flight and the override switch in the flight deck selected; this would move the iso valve to 'open'. Per maintenance manual (MM) 21-26-00; deactivation of iso valve (24HQ) does not match MEL 21-26E.

Original NASA ASRS Text

Title: A Line Mechanic reports a Deactivate Isolation (ISO) Valve (15HQ) Maintenance Procedure in MEL 21-26E for the A320 should include disconnecting the cannon plug to the same valve in order to assure the ISO Valve remains in the 'Open' position in flight.

Narrative: AVNCS SYS FAULT [message] displayed on UPPER ECAM. Chronic Issue. Tried to implement MEL 21-26E; Deactivate Isolation (Iso) Valve. The Iso Valve (24HQ) needs to be placed in the 'Open' position. But the MEL 21-26E does not tell the Aircraft Maintenance Technician (AMT) to 'Remove' the cannon plug from the Iso Valve (24HQ). The Avionics Equipment Ventilation Computer (AEVC) Test must be accomplished before each flight and the override switch in the flight deck selected; this would move the Iso Valve to 'Open'. Per Maintenance Manual (MM) 21-26-00; Deactivation of Iso Valve (24HQ) does not match MEL 21-26E.

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.

A line mechanic reports a deactivate isolation (iso) valve (15HQ) maintenance procedure in MEL 21-26E for the A320 should include disconnecting the cannon plug to the same valve in order to assure the iso valve remains in the 'open' position in flight.