Master Minimum Equipment List Global Change 3

Project Management (Certification of Aeronautical Products)

Master Minimum Equipment List (MMEL)

Transport Canada Master Minimum Equipment List (MMEL) Guidance Book Item 23.3 Cabin Service Interphone System (Flight Deck/Cabin and Cabin/Cabin), passenger carrying operations as a category B is designated Transport Canada Global Change 3 (TCGC-3).

This Global Change (GC) is an approved addendum to all affected existing MMELs. An operator must revise affected Minimum Equipment Lists (MELs) by assigning a category B for this item in passenger carrying operations. Approval of the revised MEL shall be gained using normal procedures or as otherwise directed in the new MMEL Item.



Following an aircraft crash in the U.S. in which an on board fire had occurred, there was considerable discussion regarding the Cabin Service Interphone System in terms of its serviceability, appropriateness of MMEL relief and the issue of communication between the flight deck and the cabin by opening the flight deck door with smoke in the aircraft. This System is clearly required for emergency procedures; yet, like the Public Address System, relief is permitted. This is in violation of the MMEL principle that equipment, which is required to complete an emergency procedure, must be operative. However, because the associated procedures are not usually addressed in the Airplane Flight Manual and are not related to direct control of the airplane, relief has been permitted. It is noted the PA System relief is a category B.

At a 1997 FAA MMEL Flight Operations Policy Board (FOPB) meeting with industry, the argument was made that this item is repaired within three days in most cases. Notwithstanding, during the deliberations for the TC MMEL Guidance Book in Jan 98, this increase in category was proposed to Canadian industry. Although there was some industry objection to increasing the category because of the U.S. industry statements regarding historical repair times, TC felt that by assigning a category B it would ensure that all operators would make these repairs in a timely fashion. This was considered a reasonable compromise to removing the relief entirely in accordance with the arguments made above.

This Global Change reflects the category change, which was approved at Revision 4 of the Guidance Book, 31 Mar 98.

Original signed by:

W.R. Jupp
Acting Chief
Aircraft Certification, Flight Test
for Minister of Transport

April 22, 1998

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