Difference between Level Change and Alt Intervention

[Jetman67 517]

Hello Anybody know the differentiation between Level change and Alt intervention when in Vnav path

[Hawk777th 0]

ALT INT is to clear the FMC up to the next assigned altitude. Level change is more about holding a speed to a selected altitude. To the best of my knowledge.

[Jetman67 517]

thanks anybody else want to chime in here

[safir365 0]

thanks anybody else want to chime in here

LVL CH let you choose a speed in the MCP, so the autopilot adjusts the rate of climb/descent to keep the speed you set in the MCP.ALT intervention is like when you go on CRZ page and change the altitude in the CRZ ALTITUDE...

[Not30Wagain 1]

You are mixing your modes!! For vertical navigation you can either use LVL CHG, VNAV or V/S. Selection of any of these will knock out the previously selected mode. So if in VNAV PTH pushing LVL CHG will cancel VNAV. ALT INTV will remove the next constraint from the FMC. For example on a SID first waypoint has an altitude constraint of 4000', controller clears you to 6000' before you reach the waypoint. To stop the aircraft leveling off at 4000' in VNAV PTH you set 6000' in the MCP and press ALT INTV which clears the 4000' restriction and allows you to continue climbing. It's a complicated subject, if you want more detail I'd be happy to help. Andy

[Spin737 102]

Hello Anybody know the differentiation between Level change and Alt intervention when in Vnav path

LVL CHG climbs at N1 Limit at the MCP Speed or descend at idle and MCP SPDVNAV will also climb at the N1 Limit but at VNAV SPD or attempt to descend at idle and the econ speed for your cost index. LVL CHG doesn't care about any restrictions in the LEGS page (Cross AT, BELOW, ABOVE), only what's in the ALT SEL window.VNAV will follow VNAV PATH, honoring those restrictions. I assumed you meant climbing and descending, not what does pressing the ALT INT button do.