@paco_bist du dir da absolut sicher? Siehe folgende Erklärung meiner Quelle, die sich offenbar auf das Telar-Manual bezieht:
BUK TELAR crew have manual which describe their action during firing.
For target coming ahead (or running away) TELAR crew should fire ONE missile because probability for hit target is close to maximum (near 0.9). If TELAR firing into other targets (from side, group targets, targets using ECM or missiles) then crew should use TWO missiles - both from TELAR or one from TELAR + one from TEL ( if firing as battery). You can offten see this on video.
Now reasons why manual talk about one and two missiles. One missile is for easy target, two missiles for hard target so both multiple chances to hit.
Physical reasons:
1. Inbound or outbound target have HIGH RADIAL VELOCITY and radar receive answer from target as signal with Doppler Shift, more radial speed (part of plane speed which have direction to radar point) then more change of frequence = much easier for detect it, measure and track it.
2. Calculation of Meeting Zone for in/outbound target is easy (because missile fly faster then target so will meet target almost on same distance as calculated), but for cause side-flying target it can be changed fast by maneur and missile can fly too high or too low for intercept in next Meeting point or dont find target when turning on seeker.
3. Radar on Telar have Wind Correction which cancel effect from wind-moving objects which blink screen with false targets. But it is also decrease lower limit of Radial Speed which radar designated as target (read #1)
4. Missile on SA-11 before and after launch receive information about doppler shift so tune up seeker on this frequency. If this difference between main signal and re-emitted signal is low it can be gone under noise signals. Then missile lost target. Same happen if frequency changed and radar cannot transmitt new shift.
5. TELAR crew have 2 modes for lock targets - by range and by speed. If speed (radial speed) too low or change too much then radar can lost this track and should remark target (by moving marker on new speed position)
6. Firing to side-flying target (with course parameter) have limitation for difference between directions radar-target and radar-missile.
7. Sequence of firing for two missiles launch first and second missile with two different guidance modes so one of missile always look on target by seeker, another only when reach close area.