What was found
REAR AFT CROSSTUBE FAILED WHILE AIRCRAFT WAS NOT RUNNING. CREW WANTED TO FILL BELLY TANK WITH WATER AND MARK NUMBER OF GALLONS, DURING FILLING OPERATIONS FROM WATER TENDER, REAR CROSSTUBE FAILED, BREAKING IN HALF, CAUSING HELICOPTER TO SETTLE ON ISOLAIR BELLY TANK USED FOR DROPPING WATER ON FIRES. EXTENSIVE DAMAGE CAUSED TO AFT CROSSTUBE TUNNEL AS WELL AS AIRCRAFT JACK POINTS.