 Beginning in January 1944 , training exercises were conducted carrying the <unk> and their crews inside <unk> gliders . These exercises were successful ; during the training by ' C ' Squadron of the <unk> Pilot Regiment , which specialised in flying the <unk> , over 2 @,@ 800 <unk> were made with an average of 50 <unk> per crew . Only three incidents resulted in fatalities or injuries , with seven pilots killed during the training . When the <unk> was re @-@ designated as an airborne tank , several changes were made to its design . A number of tanks had their 2 pounder guns replaced with a 76 @.@ 2 @-@ millimetre ( 3 @.@ 00 in ) infantry support howitzer ; these tanks were then designated as <unk> 1 <unk> ( Close Support ) . Additionally , <unk> <unk> were added to those <unk> which still possessed their 2 pounders to increase their muzzle velocity and armour penetration . 
