I appear to have the hang of this. Thanks Coff.
The topic of the picture is the Low Level Parachute and image credit to the marvellous JATE Photogs circa 1994. the aim of the trial would be to determine safe separation during simultaneous stick parachuting. Both side doors used. The aircraft would have been a K but we did repeat the exercise with the J in South Africa. Khaki chutes went out one side white the other. It was important to get a stagger between sides to avoid entanglement. The short aircraft was worse than the long one. the LLP opened very quickly so was more of an issue than the PX4. When we did the J we found that without tanks and these 6 bladed props the cross over was worse. Sim sticks was not cleared from the short J. In latter years the only chutes we had were Khaki. (Ok have your argument over American Olive Drab or NATO Green!) Khaki works for me! the colours changed over the years and lead to my having to sign of numerous production permits (concessions).
I guess the K trials would have been done at El Cento - the usual haunt of the era. China Lake and YPG became more usual haunts in latter days. The South Africa det was in an effort to save costs. Not sure if it ever did but the game parks were more interesting than spending every night in Applebys.