An organization in Russia has created a helicopter bucket apparatus that creates medium expansion foam, with a volume many times greater than plain water or foam concentrate that is simply injected into water and dropped, forming some bubbles as it passes through the air.
The terminology translated from Russian is difficult to follow, for example, they call it a Helicopter Water Spillway Device.
Apparently the apparatus has water and foam concentrate tanks, and a motor, presumably for pumping water and/or powering fans. Fans may blow air into the water/foam stream to create the high-expansion foam.
The foam from one load can cover 1,000 to 1,500 square meters, or 0.25 to 0.37 acres.
It looks very complex and expensive, but it may have a use on wildland fires. A high-expansion foam fireline should be effective for a longer period of time than plain water dropped from a helicopter. Firefighters on the ground conducting burnouts and backfires could use it as a fireline.
Thanks and a tip of the hat go out to Cameron.
We still inject foam into our water buckets on large fires quite regularly up here in BC and alberta. especially when building a fire line, water alone evaporates too quickly.
Cal Fire was using foam injection on their helicopters over 20 years ago. The fall of the water created enough agitation. They stopped using them though. I think it had something to do with contaminating water sources.