Have any of you done much external cargo work with the BK117?
Lots! Apart from water bombing, we also do a heap of sling load work, both at sea level and in the Australian Alps, which are about 6000 ft AMSL. DA in summer gets up around 8-9000ft, and the BK performs remarkably well, although the change to a 117C tail rotor has improved the capability enormously. Engine power is seldom a limitation, but tail rotor authority was woeful with the original TR blades, often hitting the pedal stop at anything above 80% Tq, when at altitude and below translational lift.
At sea level we can lift 1300kg on the hook with 150kg of fuel without any problems, and at 7-8000' DA a good working load is 1000 - 1100kg, depending on fuel load. We shift quite a bit of concrete in aluminium kibbles during ski field construction work, usually on a 100'/30 metre line: the pilot's seat is too far in from the floor to make it a good VR lifter, but as with all things, you get used to it. The BK seems to lift better the longer the line: on fire work, it certainly pulls water in a Bambi more easily and with less power on a 100' line than with the Bambi on the hook. I don't know why, but I reckon there's a 5% Tq difference between the two.