Originally Posted by DaveReidUK
At, for example, 200 kts, a climb gradient of 7% is just under 2500 fpm.
No, that's not correct.
200 kts = 20 253 feet / minute
7% of 20253 = 1418 ft/minute
My rule of thumb where you multiply the required climb gradient in % by the GS in kts to obtain the required climb rate in ft/min is very close and good enough.
So, if the SID reads "this SID requires 7% climb gradient until passing 4000 ft" it comes down to a little experience. An A320 at MTOW will have a typical GS during initial climb of about 165-170 kts (no headwind). Thus a climb rate of around 1200 ft/min (170x7) is needed. Even a new pilot on A320 knows that this will easily be achieved on two engines. In case of doubt when in IMC or by night, you can consider delaying the acceleration and flap retraction until out of the restricting altitude. Make sure you have a good engine out strategy/routing if the climb gradient was necessary because of obstacles.
Cheers!