An
Army acronym for Quadrant Fire Control. The QFC is a nifty device found within the turret of older
tanks and is used for indirect shooting.
Indirect shooting is the technique of "lobbing" shells onto an
enemy target (similar to the artillery) whereas direct shooting is where the main armament is shot directly at the target. The QFC basically allows the gunner to determine the proper angle to place the main armament at in order to
lob shells onto a target that is beyond the range of direct fire.
The QFC consists of two scales, one with an elevation/depression scale measured in mils and the other listing ranges for the various types of main armament and a bubble, used as a level. The entire system is connected to the main armament such that given the setting of the two scales, the bubble will be level when the gun is at the correct angle. The actual mathematics of the system is quite easy, except I can't rememeber the names of all the various angles.
In modern tanks, this is all taken care of automatically by computers, however in older tanks, such as Britain's Scorpion and Canada's Cougar (which uses the Scorpion turret), the QFC is an integral part of being a gunner. The QFC also uses a radioactive element to allow the scales to be read in the dark.