This is a work in progress.
Mach Slow / Medium / High
What is the cost of going fast in this jet? What does that speed get you in terms of minutes? This is just an annecdotal example showing how much gas and time it takes to go from San Francisco, California (KSFO) to Bedford, Massachusetts (KBED). But it could give us something to start with.
At Mach 0.80 it takes 12,017 lbs. to get there in 4:56.
Speed up to Mach 0.85 it will take an extra 323 lbs (not much) but gets you there 15 minutes faster (considerable).
Speed up to Mach 0.90 it will take an extra 1,618 lbs (enough to think about) but gets shaves off another 13 minutes.
PlanePerformance Wet Runway Bug
If you need to get off a wet runway you might want to think twice about using the PlanePerformance application. The numbers appear to be overly pessimistic and there is the strange problem that it seems to think it takes more runway using Flaps 20° than 10° if the runway is wet. I've asked about this and am still waiting for an answer.
Using the PlanePerformance
I was at White Plains the other day, on hot day in the rain and was wondering the G500 would do using 10° flaps off of Runway 34. Not so good, it turned out. The numbers were worse than what I had expected from my G450. So I thought using 20° flaps would improve things.
Far from it! In fact, the effective runway length increased using 20° flaps. How could that be? I turned to the AFM for help.
Using the AFM charts
Photo: G500 Effective Runway Length Required Flaps 10 and Flaps 20, AFM, §05-02-00, figures 2 and 3
Click photo for a larger image
Using the same conditions in the AFM results in shorter distances than PlanePerformance. It also appears to result in a shorter distance using 20° flaps until you consider the note on the 20° flap chart which says "When entering this chart with a known weight, increase resulting effective runway length by 300 feet." With this correction, the ERL appears to be unchanged with a change from 10° to 20° flaps.
Gulfstream GVII-G500 Airplane Flight Manual, Revision 1, August 31, 2018
Gulfstream GVII-G500 Production Aircraft Systems, Revision 1, Oct 1, 2018