B737 LNAV MEL
I recently had an aircraft with the mode control panel LNAV switch on MEL. The MEL document did not specify any specific operating procedures (O). However, in the remarks section, is the following statement: "Except for ER operations, may be inoperative provided RNAV operations, both enroute and terminal, are not conducted." To be clear, the LNAV switch simply allows the FD or autopilot to directly track the selected course to the active waypoint. Any deviation from the course will be displayed on the course deviation indicator on the ND. Therefore, it is possible to track the LNAV course in heading select rather than using the LNAV switch. Talking with colleagues, there seems to be some disagreement as to what is required to be in compliance with the MEL. Terminal RNAV operations seems to be well defined: any procedure with the word RNAV in the title. However, enroute operations do not seem to have this nice distinction. I would be interested in a discussion about whether tracking an LNAV course to a waypoint in the enroute phase using Heading Select instead of LNAV would be in compliance with this particular MEL.