The script in that shape runs and checks for the chutes only once. You might run it more than once waiting 2 or 3 seconds. Or:
~2
_chutes = nearestObjects[_pos_chute_drop, ["ParachuteWest"], 200]
{if (!alive driver _x) then {deleteVehicle _x}} forEach _chutes
~2
_chutes = nearestObjects[_pos_chute_drop, ["ParachuteWest"], 200]
{if (!alive driver _x) then {deleteVehicle _x}} forEach _chutes
~2
_chutes = nearestObjects[_pos_chute_drop, ["ParachuteWest"], 200]
{if (!alive driver _x) then {deleteVehicle _x}} forEach _chutes
~2
_chutes = nearestObjects[_pos_chute_drop, ["ParachuteWest"], 200]
{if (!alive driver _x) then {deleteVehicle _x}} forEach _chutes
That will delete chutes ever 2 seconds four times.