During preflight check a B757-200 Captain noticed status messages 'ALTN ANTI-SKID' and 'NORM ANTI-SKID.' Anti-skid system deferred inop; per MEL 32-4a. Captain believes MEL 32-5b (Option 2) should have been used. Reporter questions if 'complete system' requires that 'alternate anti-skid valves are operative.'
Synopsis
During preflight check a B757-200 Captain noticed status messages 'ALTN ANTI-SKID' and 'NORM ANTI-SKID.' Anti-skid system deferred inop; per MEL 32-4a. Captain believes MEL 32-5b (Option 2) should have been used. Reporter questions if 'complete system' requires that 'alternate anti-skid valves are operative.'
Narrative
Possible misinterpretation of MEL. On Preflight; found the following message: (alternate) ALTN ANTI SKID and NORM ANTI SKID. Entered the discrepancies in the logbook; referred to the MEL and called Maintenance. The Mechanic deferred my entry with the following sign-off entry: 'Placarded Anti-Skid system inoperative per MEL.' That was followed by the MEL required downgrade of the aircraft Autoland status. Please refer to the B757 MEL. The reason for this report; is my possible misunderstanding of which MEL should have been used. The Mechanic used (MEL) 32-4a. After reviewing further; I now believe MEL 32-5b (Option 2); should have been used in lieu of; or in addition to 32-4a. I have shared the scenario with 4 mechanics and 4 pilots; all with different opinions of what should be correct. We were in compliance with 32-5b; but the logbook entry may have been labeled (MEL) 32-4a; instead of 32-5b. Recommend that the ANTI SKID MEL's (Norm and Altn) be reviewed and rewritten so that the intent of 32-5b is clear. When 32-5b refers you to 32-4a 'Complete System;' does 'Complete System' include the Alternate system? If so; delete the 5th bullet which reads: 'Alternate anti-skid valves (MEL item 32-5a) are operative.'How can one MEL 32-5b; refer you to another (32-4a); which requires the operation of the very item you're applying the MEL to (vis a vis the ALTN system). Recommend logbook audit.
NASA callback
Reporter stated he was a former Maintenance Officer in the Military and just had a 'gut' feeling the original MEL that was applied was not very clear.Reporter stated he was informed by his Safety Committee that he was correct in his interpretation of MEL 32-5b as being the more appropriate deferral. Reporter stated; when his flight departed; his understanding was he did not have Anti-Skid indication in the NORM or ALTN mode. Mechanics had to verify the Alternate (ALTN) Anti-Skid valves were operative under 32-4a of their Procedures Manual.Reporter stated the reference in MEL 32-5b back to 32-4a only confused the issue and he would like to see a rewrite (revision) of MEL Chapter 32 to drop the 5th bullet item in 32-4a; or clarify 32-5b and remove any reference to 32-4a.
More incidents for this aircraft family →
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.