Along with a single Hughes 500D helicopter, BCMC operates a pair of C-131Fs (Convair 340) fitted with spray booms to combat the relentless mosquito population, there are no fewer than 57 species to be found in this low lying coastal community.
The mosquito season generally runs from April to November with early morning sorties being the norm for BCMC, as they must stop application if the temperature rises above 82°F (27.7°C) for this is when the mosquitoes become inactive. Early morning is also preferred as the area's honey bees are still resident in their hives and are therefore not placed at risk.
The Field Supervisor and the Deputy Director evaluate all the gathered information available from the county and they then develop a spray mission map for the pilots. That will be handed to either the chief pilot or the engineer in the afternoon so the mission can be flown at daybreak the following day.
The crew scope out the area using a map and when the spraying starts switch over to special AG-NAV Guia GPS system that is fitted to each aircraft. The unit has the capability to document the spray patterns advising the crew where they have sprayed and where to spray next, taking into account wind and drift.
Spraying is usually done at around 200 feet and at 170 knots and unlike most aerial applications an ultra-low volume spray or thermal fogging technique is used - the actual volume of insecticide is only around one to one and a half ounces per acre. Aqua Anvil is the insecticide of choice and it is diluted with water at a 1:1 ratio. The very small droplets produce a fog which drifts into sites where adult mosquitoes are flying, biting, or resting. The insecticide interferes with the mosquito nervous system and causes paralysis and eventual death.
The aircraft themselves are fitted with a single 600 gallon tank and at 170 knots with their large wingspan they can cover an astonishing 606 acres per minute and 3600 acres per mission.
Operated on the Public Use Category, they are limited to 38,900 lbs take-off weight due to the 3400 foot runway they operate from.
Beaufort County has over 2,000 islands many of which are prime breeding grounds for mosquitoes, but any spraying over salt water marshes is prohibited due to environmental concerns. They are only allowed to spray within the County (600 square miles), although in exceptional circumstances the Federal Emergency Management Agency (FEMA) could call upon them to operate anywhere within the USA.
Beaufort County started utilising aerial application for mosquito control in the 70s, and up until the 80s the work was contracted out to a separate DC-3 operator. The County acquired two TH-55 Osage (Hughes 269) helicopters in 1987, thereby taking over the operation internally. In June 1987 a C-117 (DC-3S) was donated to the County from the Drug Enforcement Administration (DEA), and this was operated for 12 years. But the numerous engine failures and the ever dwindling supply of spare parts available were beginning to hinder operations, so discussions surrounding a replacement began. This particular C-117 (N53315) now flies for TransNorthern in Alaska as N30TN and was sold in 2004.
Tom Ray, the County's Airports Director contacted both the Air Force and the Navy Surplus offices, and the Air Force offered to donate upwards of four C-123 Provider aircraft with the Navy offering all 16 of the C-131F Samaritan planes in storage at Davis-Monthan AFB. However, due to the limited length of the runway at Lady's Island airport, and the limited parts supply for the C-123, they opted for the C-131s.
Beaufort County chose three of the C-131Fs, donated by the US Navy to the State of South Carolina, which were then in turn sold to Beaufort County for $1000 a-piece. The County had an obligation to utilise the aircraft for five years, after which the State releases full control to the County which then owns them outright.
In April 1998, the first of the three C-131s arrived in Beaufort, SC. This was the Admiral's former-plane, Bureau number 141018, N444F and a contract crew flew the aircraft first from Tucson International to Dothan, Alabama Napier Field; with the flight to Lady's Island Airport completed the following day. The contract pilot subsequently admitted to major concerns about landing at Lady's Island (these emerged when he first sighted the short runway!) and he almost deviated to Walterboro in the north. Co-incidentally, Walterboro, Lowcountry Regional Airport, is where the unit performs most of the crew training at the beginning of each mosquito season. This first aircraft aircraft was used for training and obtaining type ratings, enabling flight crews to travel to Tucson in November 1998 to pick up the two remaining Convairs.
Bu141008, N8149H and Bu141009, N8149P were both flown non-stop to Beaufort, 1890 nautical miles with a flight time of seven hours and ten minutes. Over the following months N81940P was the first to be converted into an aerial sprayer and the summer of 1999 saw the aircraft's first spray season - flying for 71 hours and spraying 498,000 acres.
In 2000 N8149H was flown to Southern Field in Americus, Georgia, and the Airframe and Powerplant (A&P) students at the South West Technical College installed the beef plates on the underside of the wings at no charge to the county.
Since the aerial spraying missions began in June 1999 over four million acres have been sprayed without a single mishap and both sprayers have performed flawlessly, with the second aircraft entering service in 2001. Not a single spray mission has been cancelled due to maintenance which is both a testament to the reliability of this aged aircraft and the maintenance crew, ably led by Gary Davy at Lady's Island.
The only problem that had to be overcome with operating the Convairs at Lady's Island was the length of the runway. At 3430 feet this limits the take-off weight to 36,900 pounds and, with the aircraft at this weight, it is still more than capable of coping with an engine failure on take-off.
Chief Pilot, Truman Davis, takes up the story. "We had one instance where the door warning light came on during our take-off roll. We were almost past our V1 speed of 92 KIA when the abort was called and the airplane came to a full stop with over 300 feet of runway remaining. The small cargo door on the right side of the plane had not been closed properly and it was that which gave us the unsafe door warning.
"As for the Convairs, they are an absolute delight to fly. They are very stable, reliable, safe and overall an excellent airplane without any adverse flight characteristics regardless of configuration or airspeed while the Pratt and Whitney R2800 CB16 engine was one of the best radials ever produced. It is worth notinh that both Eastern and Delta flew the Convair 340 and 440 for many years and, when they retired them in the 1970s, neither carrier had suffered a single loss despite operating them in all kinds of weather conditions. That in itself is testament of the safe and reliable planes they were and are."
Truman continues, "Beaufort County was the first and the only operator to use the Convair for aerial spraying so we really did not know exactly what to expect after we installed our own in-house designed and built spray system. After thoroughly testing them, we were amazed at how good a spray platform the aircraft turned out to be.
"We fly them at 170 KIA, at 200 feel AGL and this gives us an operating swatch width of 1500 feet. The actual swatch width is well over 2,000 feet. We cover 606 acres per minute and a normal mission treats around 25,000 to 30,000 acres with fuel consumption averaging 130 gallons an hour total.
"On a personal note, I have flown several different heavy multi engine aircraft that have round or radial engines, including the B-25, B-17, Martin 404, PV2, DC-3 (C-47) and DC-3S or Super 3 - all of these airplanes have their own characteristics and qualities and faults, but I would rate the Convair as my number one choice to fly and maintain. It truly was a quantum leap ahead of the DC-3 that it was designed to replace."
Although the Convairs have been relatively inexpensive to operate this is potentially the last season for the old birds as the county is looking to replace them with three ex military C-12 King Airs. One reason is that spare parts are becoming harder to find and more expensive, but the biggest hurdle is finding rated aircrew to fly them with the insurance requirements stipulating 500 hours of agricultural twin time which is an increasingly rare asset.
Typically a budget is formulated for each fiscal year using historical data for a "standard" period. Every year is different due to weather etc however, so while some years would see money left over that can be reinvested in to the aircraft, other years, when the mosquito population is heavy, would see the unit short of funds and BCMC has to go back to the County Council to request capital.
A further complication is that two mosquito seasons actually fall into the same fiscal year. The accountant's fiscal year is from 1st July to 30th June of the next year, so the first mosquito season falls between 1 July to November then the second season starts and falls within the April though 30 June part of the fiscal year - this often proves to be a huge problem for the BCMC.
Mosquito control is reactive and largely based around environmental conditions. High tides, rainfall and temperatures all become a factor in the type of response needed, and this is impossible to plan for in advance. Beaufort County's current mosquito control budget is $1.8M and it has one of the lowest salary to operational budget ratios (51%). Of this budget, air operations surprisingly only takes up 37%, with the rest taken up by research, surveillance and ground operations.
Aircraft Histories:
C-131F 141008 - N8149H
1974 - NAS Sigonella
1976 - Guantanamo Bay
1981 - Bermuda
1986 - MASDC
1998 - Beaufort County - current
C-131F 141009 - N8149P
1967 - NAS Norfolk
1971 - NAF Mildenhall
1981 - Guantanamo Bay
1986 - MASDC
1998 - Beaufort County - current
C-131F 141018 – N4444F
various assignments in the USA
1986 - MASDC
1998 - Beaufort County for spares.
Note: N4444F was never converted to a sprayer and was originally acquired as a spares source. It was in such good condition that it was used as a trainer until 2007 when it was stood down and relegated to its original use as a spares ship. Eleven years of airworthy life for a spares source is pretty good going!
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