DKB GPS Approach Question

[ewrord]

Can anyone explain why the Dekalb, IL GPS runway 9 approach has higher minimums for the LNAV/VNAV than just the LNAV approach? As I understand it, the LNAV/VNAV allows aircraft with approved VNAV systems to navigate a glideslope down to the DA. Why then would an aircraft with this capability have a higher ceiling and visibility minimum then one without it. The LNAV/VNAV minimums are 1543-2 1/4. The LNAV mins are 1460 and 1. This difference seems to only be on runway 9 at DKB. Can anyone explain why??

 

[340drvr]

This is a common situation; the The glideslope portion of the LNAV/VNAV may provide a more stabilized approach descent, clear of obstacles, however, the DA(H) is reached further from the runway. LNAV only flown to an MDA, even if performed as a "dive-and-drive," allows flying closer to a MAP (perhaps even runway threshold), requiring lower visibility. (Don't forget, even though a glideslope is provided, the accuracy parameters are still not considered a "precision" approach in the way an ILS glideslope may be.)

 

[Lynxman]

Very good info here!

 

[Lynxman]

Very good info here!