The Lockheed C-130 Hercules is a four-engine turboprop military transport aircraft designed and built originally by Lockheed, now Lockheed Martin. Capable of using unprepared runways for takeoffs and landings, the C-130 was originally designed as a troop, medical evacuation, and cargo transport aircraft. The versatile airframe has found uses in a variety of other roles, including as a gunship (AC-130), for airborne assault, search and rescue, scientific research support, weather reconnaissance, aerial refueling, maritime patrol, and aerial firefighting. It is now the main tactical airlifter for many military forces worldwide. Over 40 models and variants of the Hercules serve with more than 60 nations.
The C-130 entered service with U.S. in the 1950s, followed by Australia and others. During its years of service, the Hercules family has participated in numerous military, civilian and humanitarian aid operations. The family has the longest continuous production run of any military aircraft in history. In 2007, the C-130 became the fifth aircraft—after the English Electric Canberra, Boeing B-52 Stratofortress, Tupolev Tu-95, and Boeing KC-135 Stratotanker, all designs with various forms of aviation gas turbine powerplants—to mark 50 years of continuous use with its original primary customer, in this case, the United States Air Force. The C-130 is one of the only military aircraft to remain in continuous production for over 50 years with its original customer, as the updated C-130J Super Hercules.
Background and requirements
The Korean War, which began in June 1950, showed that World War II-era piston-engine transports—Fairchild C-119 Flying Boxcars, Douglas C-47 Skytrains and Curtiss C-46 Commandos—were inadequate for modern warfare. Thus, on 2 February 1951, the United States Air Force issued a General Operating Requirement (GOR) for a new transport to Boeing, Douglas, Fairchild, Lockheed, Martin, Chase Aircraft, North American, Northrop, and Airlifts Inc. The new transport would have a capacity for 92 passengers, 72 combat troops or 64 paratroopers in a cargo compartment that was approximately 41 feet (12 m) long, 9 feet (2.7 m) high, and 10 feet (3.0 m) wide. Unlike transports derived from passenger airliners, it was to be designed from the ground-up as a combat transport with loading from a hinged loading ramp at the rear of the fuselage. This innovation for military cargo aircraft was first pioneered, known as the Trapoklappe, on the World War II German Junkers Ju 252 and Ju 352 “Hercules” transport prototypes.
The Hercules resembled a larger four-engine brother to the C-123 Provider with a similar wing and cargo ramp layout that evolved from the Chase XCG-20 Avitruc, which in turn, was first designed and flown as a cargo glider in 1947. The Boeing C-97 Stratofreighter also had a rear ramp, which made it possible to drive vehicles onto the plane (also possible with forward ramp on a C-124). The ramp on the Hercules was also used to airdrop cargo, which included low-altitude extraction for Sheridan tanks and even dropping large improvised “daisy cutter” bombs.
A key feature was the introduction of the Allison T56 turboprop power plant, first developed specifically for the C-130. At the time, the turboprop was a new application of turbine engines that used exhaust gases to turn a propeller, which offered greater range at propeller-driven speeds compared to pure turbojets, which were faster but thirstier. As was the case on helicopters of that era, such as the UH-1 Huey, turboshafts produced much more power for their weight than piston engines. Lockheed would subsequently use the same engines and technology in the Lockheed L-188 Electra. That aircraft failed financially in its civilian configuration but was successfully adapted into the Lockheed P-3 Orion maritime patrol and submarine attack aircraft where the efficiency and endurance of turboprops excelled.
The new Lockheed cargo plane design possessed a range of 1,100 nmi (1,300 mi; 2,000 km), takeoff capability from short and unprepared strips, and the ability to fly with one engine shut down. Fairchild, North American, Martin, and Northrop declined to participate. The remaining five companies tendered a total of ten designs: Lockheed two, Boeing one, Chase three, Douglas three, and Airlifts Inc. one. The contest was a close affair between the lighter of the two Lockheed (preliminary project designation L-206) proposals and a four-turboprop Douglas design.
The first flight of the YC-130 prototype was made on 23 August 1954 from the Lockheed plant in Burbank, California. The aircraft, serial number 53-3397, was the second prototype, but the first of the two to fly. The YC-130 was piloted by Stanley Beltz and Roy Wimmer on its 61-minute flight to Edwards Air Force Base; Jack Real and Dick Stanton served as flight engineers. Kelly Johnson flew chase in a Lockheed P2V Neptune.
After the two prototypes were completed, production began in Marietta, Georgia, where over 2,300 C-130s have been built through 2009.
The initial production model, the C-130A, was powered by Allison T56-A-9 turboprops with three-blade propellers and originally equipped with the blunt nose of the prototypes. Deliveries began in December 1956, continuing until the introduction of the C-130B model in 1959. Some A models were re-designated C-130D after being equipped with skis. The newer C-130B had ailerons with increased boost—3,000 psi (21 MPa) versus 2,050 psi (14 MPa)—as well as uprated engines and four-bladed propellers that were standard until the J-model’s introduction.
The C-130B model was developed to complement the A models that had previously been delivered, and incorporated new features, particularly increased fuel capacity in the form of auxiliary tanks built into the center wing section and an AC electrical system. Four-bladed Hamilton Standard propellers replaced the Aero Product three-bladed propellers that distinguished the earlier A-models. An electronic reconnaissance variant of the C-130B was designated C-130B-II. A total of 13 aircraft were converted. The C-130B-II was distinguished by its false external wing fuel tanks, which were disguised signals intelligence (SIGINT) receiver antennas. These pods were slightly larger than the standard wing tanks found on other C-130Bs. Most aircraft featured a swept blade antenna on the upper fuselage, as well as extra wire antennas between the vertical fin and upper fuselage not found on other C-130s. Radio call numbers on the tail of these aircraft were regularly changed so as to confuse observers and disguise their true mission.
The extended range C-130E model entered service in 1962 after it was developed as an interim long-range transport for the Military Air Transport Service. Essentially a B-model, the new designation was the result of the installation of 1,360 US gal (5,150 L) Sargent Fletcher external fuel tanks under each wing’s midsection and more powerful Allison T56-A-7A turboprops. The hydraulic boost pressure to the ailerons was reduced back to 2050 psi as a consequence of the external tanks’ weight in the middle of the wingspan. The E model also featured structural improvements, avionics upgrades and a higher gross weight. Australia took delivery of 12 C130E Hercules during 1966–67 to supplement the 12 C-130A models already in service with the RAAF. Sweden and Spain fly the TP-84T version of the C-130E fitted for aerial refueling capability.
The KC-130 tankers, originally C-130Fs procured for the US Marine Corps (USMC) in 1958 (under the designation GV-1) are equipped with a removable 3,600 US gal (13,626 l) stainless steel fuel tank carried inside the cargo compartment. The two wing-mounted hose and drogue aerial refueling pods each transfer up to 300 US gal per minute (19 l per second) to two aircraft simultaneously, allowing for rapid cycle times of multiple-receiver aircraft formations, (a typical tanker formation of four aircraft in less than 30 minutes). The US Navy‘s C-130G has increased structural strength allowing higher gross weight operation.