737NG VNAV question: geometric->idle descent
Join Date: Jan 2008
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I'm thinking that if someone were to replicate the 737NG FMC for the simmers to play with, then they could probably have it figured out for you all pretty pronto.
Ducking in 1 - 2 - 3
Ducking in 1 - 2 - 3
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Join Date: Jul 2009
Location: Denver CO
Age: 49
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I got one suggestion from my own company's training department:
Say you're decending to cross fix XXX at FL270, with more altitude restrictions further down the LEGS page (i.e., YYY at FL240, etc...) So far, you are only cleared to FL270. As you descend to within 800' of the restriction altitude (i.e. FL278 in this case), dial the MCP altitude knob down one click to 26900, press ALT INTV, then dial the MCP altitude knob back to 27000. This deletes the FL270 restriction from the LEGS page, but being within 800' causes VNAV to stay in PTH for reasons that have not been explained to me yet. But I've tried it, and hey, it works. The subsequent leg is converted into a idle descent, as indicated by the presence of a new T/D donut on the ND.
Of course, this requires you to actually pay attention and be ready to do the procedure in the time between you arrive at 800' above the restriction and the time that the MCP changes to VNAV ALT at level-off. A downside is that the altitude alert sounds twice...once as you descend to within 900' of the MCP altitude (as usual), and a second time after you change the MCP altitude by 100'. It tends to wake your partner in the other seat.
If you don't have an ALT INTV button (I understand it is optional, and who knows why), I'm not sure if you could achieve the same thing by deleting the altitude restriction on the FMC instead. Maybe I'll try it one day.
Try and enjoy!
Say you're decending to cross fix XXX at FL270, with more altitude restrictions further down the LEGS page (i.e., YYY at FL240, etc...) So far, you are only cleared to FL270. As you descend to within 800' of the restriction altitude (i.e. FL278 in this case), dial the MCP altitude knob down one click to 26900, press ALT INTV, then dial the MCP altitude knob back to 27000. This deletes the FL270 restriction from the LEGS page, but being within 800' causes VNAV to stay in PTH for reasons that have not been explained to me yet. But I've tried it, and hey, it works. The subsequent leg is converted into a idle descent, as indicated by the presence of a new T/D donut on the ND.
Of course, this requires you to actually pay attention and be ready to do the procedure in the time between you arrive at 800' above the restriction and the time that the MCP changes to VNAV ALT at level-off. A downside is that the altitude alert sounds twice...once as you descend to within 900' of the MCP altitude (as usual), and a second time after you change the MCP altitude by 100'. It tends to wake your partner in the other seat.
If you don't have an ALT INTV button (I understand it is optional, and who knows why), I'm not sure if you could achieve the same thing by deleting the altitude restriction on the FMC instead. Maybe I'll try it one day.
Try and enjoy!
Join Date: Jan 2006
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During descent, update the fix you are flying to about every 2000 feet. Vertical path solution is calculated with minimal disruption to the path descent based on FMC computed winds and current anti-ice configuration.
I don’t know… trying to trick the system by selecting phantom altitudes on the MCP??? Watch out for mister level bust with this technique in high density areas of frequent frequency, heading and altitude changes. Is this SOP??? who know? Remember... KISS
I don’t know… trying to trick the system by selecting phantom altitudes on the MCP??? Watch out for mister level bust with this technique in high density areas of frequent frequency, heading and altitude changes. Is this SOP??? who know? Remember... KISS
Join Date: Aug 2009
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If there is a level off restriction at some waypoint during the descent route, the new T/D from this intermediate level off altitude will be calculated and displayed on the DESC page.
