PPRuNe Forums - View Single Post - 737NG VNAV question: geometric->idle descent
Old 23rd Jul 2009, 19:31
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CaptainSandL
 
Join Date: Nov 2003
Location: UK
Posts: 495
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The VNAV geometric path descent was so unpopular that Boeing included an option in U10.7 to go back to idle descent and just retain geometric path descent in approach phase only. This was one of the main reasons why we decided to upgrade to U10.7.

You can see if you have this option enabled by checking MAINT > FMCS > PERF FACTORS. This page will show GEO DES FULL/APP at line 1L, where either FULL or APP is highlighted in reverse video. It would be great if in U11 (or the recently announced 10.8A) this option could be line selectable by crew in-flight.



RYR 738 Jock,
The reason all U10.8 operators have been told to rollback to 10.7 is because of a serious bug in geo path desc in the approach phase in which VNAV can command the airplane to descend below the expected path on approach by 200ft !!!
See my write up at FMC Update 10.8 and the imminent 10.8A service pack.

S&L

Last edited by CaptainSandL; 23rd Jul 2009 at 19:38. Reason: To add image
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