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descent will result in difficulty con- trolling airspeeds and descent rates. The two types of VNAV descents that are mostly invisible to pilots are the performance path and the geometric path. Performance path provides a more efficient (at least for jets) de- scent at or near idle power to the
first constrained waypoint. A geo- metric path provides a computed 3-D point-to-point path between two con- strained waypoints and is a shallower descent, typically not at idle power.
ATC may issue a clearance to “de- scend at pilots’ discretion” where the pilot may begin the descent whenever
they choose. During our descent on the LUCKI 1 RNAV ARRIVAL into San Diego, the bottom altitude on the arrival at LYNDI Intersection was charted at 5,000 feet and 210 kts; however, ATC advised us to de- scend via the arrival, except maintain 12,000 feet. At 12,000 feet ATC later
Figure 3
Figure 4
May 2024 / TWIN & TURBINE • 7
