Originally Posted by
evil7
Devil49
So after two hours of flying you end up at 12.000 feet???
Never happened, it's a rule of thumb. I wasn't often in a helicopter with two hours of usable fuel? I can't remember
ever being so more than a couple times in 48 years.
The idea is to run a turbine at max continuous for efficiency and minimize drag, yes? Often I could climb to better winds and
reduce power and still have a significant gain in ground speed. You never find that poking around contour or at 300, 500 feet. Plus, I could see a lot further, reduced potential obstacles significantly and expanded emergency landing selection geometrically.
I did it like this, half in cruise half in climb or descent- a 40 minute leg, a 4000 foot climb limit: climb at 600 fpm checking speed across the ground on the GPS; then level and cruise at nearest recommended cruise altitude for 20 minutes, checking ground speed and adjust as necessary for most efficient altitude; plan the descent for 300 fpm at whatever speed I could get at cruise power- this offsets the reduced speed in the climb segment. If you're flying into significant headwind component, adjust as necessary, usually lower is better. But I have gotten tailwinds on both in-bound and out-bound legs by flying over the scattered to broken of a weak front. Everybody else poking around in 3 - 5 mile vis while I'm CAVU on the one leg.
The practical limits were weather, of course, and engine/airframe capability. The Allison 250 C20 and contemporary airframes maxed at about 4500 DA, so you'd get the best out of them at that or lower. One might get better ground speed with higher and reduced power, one doesn't know without looking.