Narrative:

[I was] involved with originating plane swap in ZZZ. New aircraft MEL 34-35 inertial reference system (IRS) for left IRU (inertial reference unit) applied by previous captain; restricted to VMC day only operation. Reviewed operational weather restrictions with dispatch and was satisfied our leg to our destination could be conducted VMC. [We] reviewed MEL 34-35 IRS with previous captain. All required placarding was done correctly by previous captain. [We] reviewed MEL 34-35 IRS procedural step and autopilot restrictions with previous captain. First officer and I were satisfied that we understood and were in compliance with MEL 34-35; inoperative left IRS to 'off;' IRS select switch moved from normal to both on right. Engine start and accompanying system recall showed no inoperative items. Taxi out system recall showed no inoperative items. Takeoff uneventful; but shortly thereafter TCAS showed inoperative. In descent first officer selected autobrakes and received an auto brake disarm light. All landing braking levels generated same light. Rejected takeoff did not generate [do not arm] light on preflight; nor in the air. Complied with QRH guidance and selected autobrakes 'off.' system recall from descent checklist generated master caution cap 'flight cont' speed trim fail; single channel. [We] complied with QRH guidance. Landing uneventful [we] contacted maintenance control regarding the system failures. Maintenance control grounded aircraft. [We] stayed with aircraft until repaired. Mechanics replaced left IRU and conducted bite check on the three systems that failed en route. All systems functional after left IRU replacement. Mechanics traced left IRS input signals to all three systems. I believe we followed the MEL 34-35 IRS correctly; but believe that the MEL is possibly incomplete in identifying all the associated systems that are affected by the left IRU. While it is possible that this is a single isolated event; the ramifications of a systemic problem with the B737-700/-800 fleet may warrant further investigation. MEL [is] incomplete regarding affected associated systems.

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Original NASA ASRS Text

Title: Two pilots report their B737-700 aircraft MEL does not list the AUTOBRAKES; TCAS or RTO Systems as possibly affected by a deferral of the Left Inertial Reference Unit (IRU). Captain's suggestion to verify that all three systems are functioning prior to dispatch was also raised.

Narrative: [I was] involved with originating plane swap in ZZZ. New aircraft MEL 34-35 Inertial Reference System (IRS) for left IRU (Inertial Reference Unit) applied by previous Captain; restricted to VMC day only operation. Reviewed operational weather restrictions with Dispatch and was satisfied our leg to our destination could be conducted VMC. [We] reviewed MEL 34-35 IRS with previous Captain. All required placarding was done correctly by previous Captain. [We] reviewed MEL 34-35 IRS procedural step and autopilot restrictions with previous Captain. First Officer and I were satisfied that we understood and were in compliance with MEL 34-35; inoperative LEFT IRS to 'Off;' IRS select switch moved from Normal to both on RIGHT. Engine start and accompanying System Recall showed no inoperative items. Taxi out System Recall showed no inoperative items. Takeoff uneventful; but shortly thereafter TCAS showed inoperative. In descent First Officer selected autobrakes and received an Auto Brake Disarm light. All Landing Braking Levels generated same light. RTO did not generate [Do Not Arm] light on preflight; nor in the air. Complied with QRH guidance and selected autobrakes 'Off.' System Recall from Descent Checklist generated Master Caution cap 'Flight Cont' Speed Trim Fail; single channel. [We] complied with QRH guidance. Landing uneventful [we] contacted Maintenance Control regarding the system failures. Maintenance Control grounded aircraft. [We] stayed with aircraft until repaired. Mechanics replaced left IRU and conducted BITE check on the three systems that failed en route. All systems functional after left IRU replacement. Mechanics traced left IRS input signals to all three systems. I believe we followed the MEL 34-35 IRS correctly; but believe that the MEL is possibly incomplete in identifying all the associated systems that are affected by the left IRU. While it is possible that this is a single isolated event; the ramifications of a systemic problem with the B737-700/-800 fleet may warrant further investigation. MEL [is] incomplete regarding affected associated systems.

Data retrieved from NASA's ASRS site as of July 2013 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.