In testimony Wednesday before the Senate Appropriations Committee, Chief of the Forest Service Tom Tidwell said the agency hopes to obtain the C-27J aircraft that the Air Force may decide to declare surplus, and the USFS would outfit them with scaled down versions of the Modular Airborne FireFighting System (MAFFS) tank systems that are used in military C-130s. When asked, he said the C-27Js would hold 1,800 gallons of retardant in the MAFFS unit. When used in C-130s, the systems can carry up to 3,000 gallons, during favorable density altitude and fuel load conditions.
Some would say that choosing a MAFFS design rather than a conventional gravity powered tanking system is misguided. The retardant in a MAFFS is pumped out by a complex compressed air system and the delivery has been criticized as not being able to penetrate tree canopy as well as a gravity system. A MAFFS would have a much lower retardant capacity since it requires an air compressor, tanks for compressed air, and a complex system of additional valves and piping. All of that extra equipment means less capacity for carrying retardant. It also requires two loadmasters, in addition to the two or three person air crew, to operate the MAFFS, doubling the personnel cost.
I just don’t see the advantage of installing a MAFFS unit in a government-owned air tanker rather than a conventional gravity system. It holds less retardant and does a less than desirable job of retarding the spread of a timber fire.
Sure, you would be able to remove the MAFFS and use the plane for hauling cargo in about a day, but how often during the winter does the USFS need seven cargo planes? It could be used during fire season to haul firefighters, smokejumpers, and fire equipment, but then that makes it unavailable as an air tanker. So you’re either going to use it for hauling stuff, or as an air tanker, but not both.
It should be relatively simple to scale down an Aero Union gravity tank, which has been tested, approved, and used for decades in C-130s, to fit into a C-27J.
Coulson is using an Aero Union designed tank, slightly modified, for the C-130Q they are building right now in San Bernardino. The tank has wheels, and Britt Coulson told Fire Aviation that they can install or remove the tank in about 30 minutes, making it available to haul cargo.