There’s plenty of info available on this, but I thought I’d share a particular chart I’ve built to calculate descents. I figure people can use this, and I fully recognize that I’m no expert, I put some effort into this but I would appreciate if anyone can correct me or provide feedback on how I can improve it. This was inspired by the fact that I’ve found different descent calculators to be little off somehow, so I calibrated this by hand, using solo mode to make sure it represents the performance of the sim as accurately as possible.
Some notes before I explain: This was done with no wind, so at least two things should be adjusted if wind is significant- the GS and therefore the distance covered, as well as the altitude at which you cut the throttle to get under the speed limit at 10,000ft. Also, you’ll notice that I’m flooring it at 340kts IAS all the way down to FL150, when I cut the throttle. Throttle remains idle until setting at 190kts IAS under 5,000ft. Under the given conditions, no flight spoilers are necessary. A final note- this was done in a 777-300, so cruising speed is specific to that airplane, as well as its aerodynamics. In the “actions” column you’ll see that I am managing the throttle in a specific way, as well as the vertical speed, so this may not work ideally for other aircraft. It likely will be close though, as long as you do what needs to be done to hit the listed airspeed.
The most important columns are “altitude” and “total”. “Total” gives you the distance needed to reach 3,000ft of altitude, from a cruising altitude given in the first column. These distances are calculated based on the vertical speed listed, which needs to be adjusted as you descend. The TAS/ground speed column is just a function of your airspeed of course. The “dist/-1000ft” column is the distance traveled in the previous 1,000ft of altitude, this isn’t that important unless you’re interested in my math, I’ve basically done some rough calculus without calculus here, if that makes sense to you.
If you begin your descent at the listed distance from your 3,000ft-altitude-waypoint given your cruising altitude, this really should be nearly spot on without wind. Again, I hope it’s helpful to someone, and in turn feedback is much appreciated, this is an ongoing pet project.