(OXMORON1) wrote:

The mail/supplies in the bucket trick goes back farther than that. IIRC the
"bucket trick" was the inspiration for the AC-47 development for holding the
fire on the target in a steep banked turn.

In addition to the Amazon, the technique was used by missionaries in Borneo,
both sometime in the late twenties or early thirties.

Oxmoron1
Don't ask me where I read it,but it was a long time ago.

As the legend goes, the missionaries discovered that by squaring
their groundspeed and dividing that figure by 15, they would arrive at
the proper "pivotal altitude" from which to fly circles allowing them
to lower a bucket of medicine and supplies to people on the ground.
Nowadays the maneuver is called Eights On Pylons.