If only I

"If only I

Wrong impression. This is about machines, not people. Breath.

>Pilots should know how to crunch a few numbers in their heads>after flying aircraft for decades/thousands of hours.I would hope so. 150 nm is equal roughly to 20 minutes of flight time - 20 minutes times 1200 fpm and you get almost 25000 ft. Clearly even with doing less accurate arithmetic than this one would expect that initiating DES NOW 150 nm before TOD will have rather significant impact on the profile.Michael J.http://www.precisionmanuals.com/images/for...argo_hauler.gifhttp://sales.hifisim.com/pub-download/asv6-banner-beta.jpg

From a practical viewpoint you would only use the "descend now" feature that far out if you were given a lower level by ATC say due to converging traffic. This would intiate a cruise descent to the new MCP altitude and when there recalculate a new TOD point. Inside 50 mls it doesnt and assumes that you are going to eventually try to pick up the original descent point at some place further down track. It is a useful feature if ATC tell you to decend now and not at pilot discretion (Planned TOD). I notice that the ATC in FS9 always seems to clear you down very early and this is where that feature comes in handy.Q is quite right that pilots do have ball park numbers in their heads the best one being the 3 times table. There are many techniques to descend this beast and "descend now" is just one of them.If ever you get confused with what the aircraft is doing or the VNAV seems to be screwed up just hit FLCH. A brilliant oh s..t mode. As long as you have the altitude you want set in the MCP and the AT engaged it will either climb to or descend to that altitude and all at the press of one button. To check on descent progress multiply your height to lose by 3 and add 10 and this will cover you for about 90% of all eventualities. From then on you can look for a trend and make adjustments as necessary. Use the green arc. Getting a little high? Crank the speed up first (assuming smooth and no procedural speed limitations). This has a radical affect on descent path. Still too high or getting to fast? Speed brake. Too low? either dial the speed back slightly on the MCP (not my personal favourite as jets should be flown fast) or apply a little bit of power. The AT will be in HOLD so this is easily done by hand. Once you have a descent looking VNAV profile again intercept it and select VNAV. Just be careful and remember that if you select VNAV and your current speed is well above the VNAV programmed speed that it may shoot out the top. CheersSteve