The MCP logic for VNV is different if you don't have ALT INTV. During climb or descents, VNAV disarms at each intermediate level off and has to be re armed each time. With ALT INTV you don't have to do that. Also, all waypoint restrictions have to be manually removed in the FMC.
Ken Hair
PMDG 737 NG had a setup option to exclude ALT INTV? You fly the MCP differently when so equipped. Many airlines choose not to equip with ALT INTV. It may have been discussed before, but why is this setup option missing from NGX?
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Ken Hair