C-130 Hercules Aerial Spraying

“We do some specialized flying mixed with a lot of science,” noted Maj. Phil Townsend, the chief of aerial spray with the 757th Airlift Squadron at Youngstown ARS, Ohio. “Our mission is to provide a large-area spray capability to control disease-carrying insects, eradicate undesirable plants, or disperse oil spills. And we are getting busier every year.”

Assigned to Air Force Reserve Command’s 910th Airlift Wing, the 757th AS is the only large-area, fixed-wing aerial spray unit in the US Department of Defense. Aircrews, maintainers, and a couple of the unit’s six entomologists—almost half of the insect specialists in the US Air Force—deploy more than twenty-five times a year for extended operations at locations ranging from southern Florida to Mountain Home AFB, Idaho, and from Parris Island, South Carolina, to Hill AFB, Utah.

Flying C-130Hs equipped with palletized Modular Aerial Spray System, or MASS, units, 757th AS crews spray thousands of acres every spring, summer, and fall. “A C-130 can spray up to 150,000 acres per day,” noted Lt. Col. (Dr.) Mark Breidenbaugh, who heads the entomology department at Youngstown. “Some places, a spray-equipped Hercules is literally the only way to manage invasive plants or to apply pesticide.”

The mission of the 757th AS, known as the Blue Tigers, dates back to the Pacific theater in World War II. Eradicating disease-carrying insects, or vectors, from the air became a priority once the US military saw how many hundreds of thousands of Soldiers and Marines became incapacitated—and how many died—from malaria and other diseases. The Special Aerial Spray Flight was created soon after the Air Force became a separate service in 1947.

Air Force crews flew insect spray missions during the Korean War with T-6 and C-46 aircraft. During the Vietnam conflict, aircrews, primarily flying the UC-123 Provider transport, carried out 1,500 insect control missions in addition to the thousands of flights spraying the controversial defoliant Agent Orange. “There is now an executive order preventing using herbicide in war,” noted Breidenbaugh. “And in this unit, we are stricter than the strictest state environmental laws and safety requirements when it comes to handling and applying pesticides and herbicides. We closely monitor the health of everyone involved. That all came about because of Agent Orange.”

On 1 April 1973, the active duty Air Force UC-123K spray aircraft and the service’s entomology staff were transferred to the Air Force Reserve. The aerial spray mission shifted from the 355th Tactical Airlift Squadron at Rickenbacker ANGB, Ohio, to the 757th AS at Youngstown in January 1992. At the same time, the spray aircraft changed from the C-130E to the C-130H.

Tools Of The Trade
A dedicated spray maintenance flight was also established in 1992 to take care of, load, and operate the MASS units. This group of twenty technicians, part of the wing’s 910th Maintenance Squadron, works out of its own garage at one end of the Youngstown flightline. “Many of us have been here for twenty years,” notes CMSgt. Ken Pauley, the aerial spray flight chief. “You have to be a bit of a zealot in this job.”

Conair Aviation, a Canadian aviation services company, delivered the first MASS unit in 1988. Each unit weighs 8,900 pounds empty and takes up three pallet positions in the C-130. The sixth and final unit arrived at Youngstown in 1992. “These spray systems are the only ones in the world like them,” Pauley noted.

Each MASS unit can carry 2,000 gallons of pesticide, herbicide, or dispersant, but only one type of agent is carried at a time. The system consists of two 500-gallon stainless steel tanks, two 500-gallon aluminum tanks, one 200-gallon aluminum flush tank, in addition to pumps, pipes, and a control station. The heavier stainless steel tanks are required for agents that are corrosive to aluminum, which limits overall capacity for missions requiring those agents. The four main tanks are tilted up toward the flight deck to use gravity to help them drain completely.

In the maintenance flight garage, the MASS units are stored on individual flatbed trailers. Each unit has a dedicated crew chief and assistant, who are allowed to personalize the systems with artwork on the control panel. The flatbeds allow for ease of transport and installation of the MASS units in one of the four 757th AS C-130s that have been modified for aerial spray. The units are transferred from the flatbed to a cargo loader, and then rolled directly onto the aircraft. Installation takes about one hour.

The primary spray aircraft, all delivered in the late 1980s and early 1990s, feature upgraded electrical connections, paratroop doors with a sealable port that accommodates the four-inch diameter pipe for the spray nozzles, and internal plumbing for an inner and outer set of spray bars mounted under each wing. “The spray bars give us extra coverage per pass, but they are not used on most missions,” notes Townsend. “We mainly use the door nozzles.” The nozzles and spray bars are installed on the aircraft after arrival at a deployed location.

Two C-130s assigned to Youngstown’s second flying squadron, the 773rd AS, are partially modified for spray operations. “We only have manning authorization for the four primary aircraft,” said Townsend. “We’d only use the other aircraft in an emergency. Those C-130s are the ultimate spares.”

Airborne Exterminators
“Flying at low altitudes and fairly high speeds in congested areas with towers isn’t for everyone,” observed Townsend. “This is a high-competency, high-visibility program. Experience and performance really matter. It may take five years for an experienced copilot to become a spray mission commander.” Qualification for spray navigators and flight engineers are much the same.

“Loadmasters have to have about 1,000 hours of flight time before we’ll consider them for the spray mission,” said Townsend. Two loadmasters are carried on spray missions, one to operate the MASS control panel and the other to monitor the tanks, lines, and pumps and to ensure the agent is being dispensed. “There is, by necessity, a lot of coordination between the flight deck crew and the two spray operators in the back of the aircraft,” added Pauley.

Once trained, a MASS-qualified crewmember has to participate on two training or operational flights every six months and at least one actual spray mission every calendar year. The training missions can come at Youngstown or at the end of a deployment when one final mission is flown over the previously sprayed area to flush the large tanks with water or, for some agents, with mineral oil. One of the spray units, MASS 6, is only used for local training flights. It has never been filled with anything but water as both a safety and a liability concern.

“Spraying is not just quantity dumping,” stated Townsend. “We need to make sure the agent goes where we want it to and doesn’t drift onto a farmer’s field. We also have to put out the exact dosage per acre.” For instance, a shot glass of insecticide mixed with water is enough to kill mosquitoes over an entire acre. Breidenbaugh noted that the right size droplet to kill a flying mosquito is roughly twenty microns. “A fifty micron droplet will kill a mosquito simply on impact, but it wastes material and puts more chemicals in the environment than necessary.”

Although the 757th AS now has seven fully qualified spray crews, it is working to get all of its aircrew members qualified because business is booming.

After Hurricanes Katrina and Rita in 2005, squadron crews treated nearly 2.9 million acres for mosquitoes and flies in Louisiana and Texas, the largest aerial spray mission ever conducted under AFRC. More than 771,000 acres were treated in Louisiana after Hurricane Gustav in 2008. More than 30,000 acres of open water in the Gulf of Mexico were treated with dispersant in the aftermath of the Deepwater Horizon oil rig disaster in 2010. “We now regularly conduct mosquito abatement operations on federal installations in nine states,” noted Breidenbaugh. “We’ve been very successful at controlling the cheatgrass at Mountain Home, which allows native prairie grasses to reestablish, which reduces the potential for range fires. We’ve done research on droplet drift through foliage and validated computer models. We’ve got a lot going on.”

Out In The Field
Since 1983, one of the regular stops for the 757th AS is Hill AFB, Utah. This spring, two aircrews and six spray maintenance flight technicians deployed to the base near Salt Lake City to treat the bombing ranges in the North Utah Test & Training Range, an isolated, desolate expanse of land west of the Great Salt Lake. The objective of the mission is to rid the ranges of Halogeton, an invasive, non-native succulent plant that grows fast and is toxic to animals. Killing this plant clears the range to allow weapons testers to see results immediately and explosive ordnance disposal technicians to disarm weapons unimpeded.

The herbicide used on the Hill ranges is called Krovar. Like all the agents used by the MASS crews, Krovar is delivered from local vendors—spray materials are never transported in raw form on the aircraft as a safety precaution. The load crews mix the Krovar with blue dye, water in specific amounts, an additive to keep the mix from foaming in the tanks, and an agent to increase the surface tension of each droplet to control drift. After the first batch of 1,800 gallons is loaded into the MASS unit, a second batch is prepared for the second aircraft. Crews apply about twenty-two gallons of mixture per acre.

The aircrews stagger their takeoffs, so while one crew is spraying, the second aircraft is being loaded. Each lift, as the crews calls them, at Hill requires about twenty minutes of transit time, about thirty minutes of to spray, and about twenty minutes back. Each crew flew two lifts per day over the ten-day deployment.

A commercial agricultural spray GPS attached to the upper escape hatch provides an additional tool for the navigator on most missions. But at Hill, the spray crews take advantage of an old navigational tool – the human eye.

The Utah ranges are so wide open, a truck is parked at each end of the areas to be sprayed--which, in 2011, were the nearly 1,300 acres of the range designated as Targets 21 and 24. The C-130 pilot lines up on the truck, and the navigator, taking winds into account for drift, calls “spray on” as the aircraft passes over the first vehicle. The loadmaster then opens the nozzles. The navigator calls “spray off” before the aircraft passes over the truck at the other end of the target. The aircrew repositions, and the drivers in the trucks move forward thirty-five feet to park in the middle of the next swath to be sprayed. Because of the dye, it appears the crew is using a roller to tint the desert blue as they fly back and forth.

As at all operating locations, the MASS unit tanks were flushed at Hill. But just like after every operation, the units were taken apart and thoroughly cleaned and reassembled once back at Youngstown. The biggest issue with the MASS units is their age, increasing the need for upkeep and maintenance, and their uniqueness. Because these systems were the only MASS units ever built, spare parts are becoming a serious issue. “We now make a lot of our own parts,” said Pauley. “One of our crew chiefs found some new and better pipe endcaps in a junkyard.”

“We continue to get calls from other Department of Defense installations as word gets out about what we can do,” concluded Townsend. “New missions for us are being discussed, such as supporting US Africa Command and fighting malaria there or providing a capability to remediate large chemical spills. We have a big job and it’s getting bigger.”