Originally Posted by
Pilot DAR
If you're really stuck for the answer, I can ask when I see the maintenance guys next spring. I knew the gentlemen who designed the mod, though they're both pretty well retired now.
In the mean time, this information should get you close.
https://www.bushplane.com/index.php?id=waterbomb
There is a minimum amount of water to be carried before it actually reaches the ground in a salvo. I was doing some design work to have a Cessna Caravan become a water bomber, but it won't carry enough weight in water to make it effective. The Twin Otter seems to be about the minimum, but they work well....
I have visited this fine museum a number of times, and highly recommend it
Also, have a look for the book: Aerial Firefighting, by Wolfgang Jendsch. I have a copy, and it's a very informative read.
When I was a college student I worked as a non-pilot crewmember on the Twin Otter during 2 summers. It was an awesome job.
The floats hold 225 gallons of water each. The water is collected through a probe on the bottom of the float as the aircraft skims the water on the step. There are little openings covered by a flap near the top of the float. When the float reaches capacity it starts to spill out the little opening. It is visible from the pilot seats via a rear-view mirror outside the pilot windows. At that point the pilot flips a switch that retracts the water-collection probe.