Under-slung loads can be quicker for the helicopter on short trips, provided the ground staff can prepare the loads and someone can recover the nets and strops. They are used a lot at sea for short cargo transfers.
For longer trips, aid delivery may be slower because with a big load underneath the helicopter has to fly slower.
These loads also hang right under the centre of gravity of the helicopter; so some helicopters can lift more under-slung.
A Jet Ranger can lift more under-slung, but there are better helicopters for cargo delivery. Bigger helicopters are better for cargo, for example an Mi-8 can lift about 3 tonnes.
Also the stops and nets cost, and getting the helicopter and the pilot certified for sling work can cost as well.
Under-slung in 2007
All that work done, here Bob Gillan and the Hope of the Nations helicopter deliver non-food aid in the 2007 floods. Here the loads are being prepared by Mark Mitchell our ground crew and an experienced disaster logistician.
It takes a lot of skill to fly under-slung loads. If they are not loaded properly they can fly themselves and hazard the helicopter. Also if the pilot is not careful they can swing under the aircraft.
So there is a place in the disaster response lexicon for under-slung loads.
We want them as an option to help those who are really isolated by floods or other disasters..