how often is VNAV used in real world ops?

[Guest gooper]

this may be a question best answered by real world pilots like yourself Robert but i was wondering how often this feature is even usd in the real world by pilots give that what the FMC calculates as the TOD point is probably more often than not not when ATC would clear you to begin a descent in which case I assume you would either use LVL Change or the VSI to control your descent.

[Guest btclarke]

Hi,I have flown several times in the jumpseat of the -800 and A320. If I recall correctly, the majority of the time they did use the VNAV function, especially where there is a STAR involved, it can calculate the track miles to touchdown and work out the TOD point accordingly. By profession, I am an ATC, and as a rule of thumb, we work on 3 miles per thousand feet of descent, ie. F330 = 99nm to descend to 0ft amsl. If I ask a pilot for a high-speed descent, ie. 320IAS to 20nm, then that distance shortens quite a bit. If you specify the speed for the descent, then the FMS should calculate a shorter TOD / steeper VNAV path, as you will require a greater ROD to maintain the required speed with thrust idle.Personally, I fly the FS at 2500fpm VSI indicating about 280-300 and allow myself 3nm/1000'. Works 99 % of the time, if I'm too high, I add a vector to lose the altitude and or speed.Bryan

[BAW277 1]

VNAV or as Airbus-Pilots calling it "managed climb/descent" is used on a regular base. Friend of mine works for Germanwings as F/O and so this information is first hand.CheersHolgerEDDK