Danny
Thanks for your information and points you raised. They sent me scurrying for 'Scorpion's Sting', the 84 Squadron history. Happily I can give you a more authoritative explanation than I previously did:
Target identification. In December '43 Arthur discussed the topic with Brig. Wingate, commander of the Chindits. The ground was often too featureless for Wingate's suggestion that troops would identify targets by sending a map reference. Arthur proposed the use of two smoke mortar bombs, one at each end of the target at the appointed Time Over Target (TOT). Wingate raised the risk of the Japs countering the technique by putting smoke down on friendly troops. Arthur proposed that they either used coloured smoke, of a specified colour, or if coloured smoke was not available, using either three mortar bombs to form a triangle, that defined the target area, or four to make a square. This technique was tested on the ground in Gwalior with the Chindits, and was subsequently adopted.
I recall my father explaining that there was an added complication when they were using their low level dive technique, during the monsoon, when cloud was too low to permit a vertical dive. There was a risk of bombs missing the target, usually over-shooting it. This was potentially hazardous for nearby friendly troops. So it was important for the pattern of mortar smoke bombs to define where the troops were. That way, the dive was made across the front of the troops, so that any over-shooting bombs or bombs falling short wouldn't imperil them.
Number of aircraft deployed on an op. 84 Squadron had sixteen Vengeances, 12 available for ops and 4 as reserves or being serviced. Normally 12 were flown for a mission. Sometimes the 12 would separate, 6 attacking one target, while the other 6 went for another one. 3 were enough to destroy a bridge. The formation used was invariably in stepped-down Vics of 3 aircraft, each flight of 3 being stepped below the one in front. This was easy to maintain and was less tiring on long flights (some taking 3 to 4 hours). It also gave optimal protection against attack by fighters, the rearward guns, combining their fire power. The sixth and twelfth aircraft carried cameras, which the pilot would switch on before he peeled-off into the attacking dive. In an attack by 6 aircraft, they would then record the accuracy of bomb-strikes of the first 4 aircraft. Film would be assessed by 221 Group Ops Room, who would decide if a second attack was necessary, depending on the type of target.
Bombs. Bombload was usually 2X 500 lb and 2X 250 lb HE. Nose rods might be fitted to detonate the bomb slightly above ground surface, to maximise blast. Delayed action were used on deep bunkers, to effect penetration. HE and incendaries were used for supply dumps and stores. Bridges received both instantaneous and delayed action bombs. The latter going-off up to seven days later, to spoil attempts to repair the bridge.
Opening the book at random, exactly the right page was before my eyes. I think my father might be taking an interest in this Thread!
