B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 73
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification
Procedure; Aircraft
During cruise at FL360; we encountered a MASTER CAUTION light with the FLT CONT and IRS lights illuminated on the System Annunciator Panel. The overhead panel had the SPEED TRIM light illuminated; and the aft overhead panel had IRS #2 FAULT light illuminated. We complied with the QRH and were unable to clear the IRS fault light. With this malfunction we also lost both autopilots; so after confirming with Company Dispatch that RVSM procedures were the same in Mexican airspace; we notified ATC of our 'unable RVSM due to equipment failure'. (We were with Merida Center) ATC acknowledged the failure and stated 'maintain 360'. We repeated the instructions and verified that they knew we had the equipment failure.Due to weather beneath us; as well as not wanting to face a possible international divert; due to insufficient fuel at a lower altitude; we opted to stay at FL360 and not request lower ourselves. We were also a bit concerned that the language barrier may have been preventing ATCs full understanding of our failure; which is why we made sure they understood our equipment situation. Traffic along our route was light; and we monitored TCAS very carefully to stay ahead of any traffic that would fly near us. We never experienced any difficulties with altitude or flight path control. When switched to Monterey Center; we informed them of the 'unable RVSM due to equipment failure' and were immediately told to descend to FL270. We flew the aircraft for two hours without autopilot; and without incident.
B737 Captain reported an IRS #2 fault at FL360 rendering both autopilots inoperative. Merida Center was advised 'unable RVSM due to equipment failure' and the crew was told to maintain FL360. When the crew advised the next ATC sector of the equipment problem; they were told to descend and maintain FL270.