#1 - To convert climb gradient to climb rate, multiply
the gradient by the airspeed in knots.
Climb rate (fpm) = Climb gradient (%) x Airspeed (kts)
-- 1% climb gradient over a mile = 60 ft (1% of 6000ft=1nm)
-- No wind; groundspeed = airspeed
example: Climb gradient = 5.5 %
Airspeed = 220 knots
Climb rate = 5.5 x 220 = 1210 feet per minute
#2 - To convert the climb gradient to the climb rate in hundreds of feet,
divide your current ground speed by 60 and multiply by climb gradient.
example: If you want to gain 200 ft per nm and have a 150 kts ground speed,
your rate of climb in hundreds of feet is 500. (150/60 * 200 = 500)