Hi Neil,
We normally use the following system for working out capacity.
Each model aircraft = 3 aircraft
E.g. A Russian An-24 carries approx 50 troops x 3 = 150 troops therefore 1 model aircraft can carry 3 infantry units. So I think a Il-76 holds about 125 paratroops x 3 = 375 paratroops so about 7-8 infantry units per aircraft (if in 2 level configuration it can hold around 225 armed troops x 3 = 675 armed troops so about 13 or 14 units but it has to land). Using this system then a single aircraft model would hold 3 BMD's, and maybe say 4 GAZ Tigr's.
Hope this helps.
Cheers
Richard P
