The optimum climb rate

Beginners pitch up the nose and think they can climb like a rocket. The steeper, the faster.

There is actually an optimum angle for climbing - not too low, not too fast - and it varies by plane type, upgrade status and altitude.

I'll tell you two general rules of thumb here:

(1)

Save for jets and biplanes, the optimum climb rate for a fighter is at about 250-280 kph speed for most planes and at about 220-250 kph speed for turnfighters with low wing loading (weight divided by wing area) such as Ki-43, A6M or most Spitfires.

(2)

A much better rule of thumb is to look at the climb angle instead of the speed, since you may inititally be faster anyway. Switch to the "F4" view with the "F4" key. There you see a head up display as used in 1970's and newer military aircraft. It indicates your angle of climb, similar to an artificial horizon.

For good climbers (propeller monoplane fighters) such as fully upgraded P-63, Fw 190D-9, Spitfire LF Mk IX etc use this:

Initially climb at 25-30°, drop to about 20° at about 3,500-4,000 m and drop to 15° (or even later on 10°) at unusually high altitudes (fitting to rule (1)).

For most (propeller monoplane) fighters try to climb at 20° at first and drop to 15° at about 3,500 m.

Bombers (propeller) should usually climb at about 10°, some good climbers (Do 217, Il-4 etc) at 15° up to about 5,000 m at least. At very high altitudes (above 7,000 m) as little as 5° may be most useful.

Jets; climb at about 10-15°.

Remember; climbing slows you down, and slow planes are easy targets. Switch to level flight or even gain speed  by dropping about 300 m before you engage in combat with a fighter who's aware of your presence! Do this in time or you'll be shot down before you can make good use of your energy!

500 m ~ 1,500 ft  (accurately: 1,640 ft)