The Lockheed C-141 Starlifter is a retired four-engine military strategic airlifter that served with the Military Air Transport Service (MATS), its successor organization the Military Airlift Command (MAC), and finally the Air Mobility Command (AMC) of the United States Air Force (USAF). The aircraft also served with airlift and air mobility wings of the Air Force Reserve (AFRES), later renamed Air Force Reserve Command (AFRC), the Air National Guard (ANG) and, later, one air mobility wing of the Air Education and Training Command (AETC) dedicated to C-141, C-5, C-17 and KC-135 training.
Introduced to replace slower propeller driven cargo planes such as the Douglas C-124 Globemaster II and Douglas C-133 Cargomaster, the C-141 was designed to requirements set in 1960 and first flew in 1963. Production deliveries of an eventual 285 planes began in 1965: 284 for the USAF, and a company demonstrator later delivered to National Aeronautics and Space Administration (NASA) for use as an airborne observatory. The aircraft remained in service for over 40 years until the USAF withdrew the last C-141s from service in 2006, after replacing the airlifter with the C-17 Globemaster III.
Development Origins Throughout the early 1960s, the United States Air Force's Military Air Transport Service (MATS) relied on a substantial number of propeller-driven aircraft for strategic airlift.Davis and Willson 2019, p. 74. As these aircraft were mostly obsolescent designs and the USAF needed the benefits of jet power, the USAF ordered 48 Boeing C-135 Stratolifters as an interim step. The C-135 was a useful stop-gap, but only had side-loading doors, thus much of the bulky and oversize equipment employed by the U.S. Army would not fit.Davis and Willson 2019, p. 150.
In spring 1960, the USAF released Specific Operational Requirement (SOR) 182, calling for a new aircraft that would be capable of performing both strategic and tactical airlift missions. The strategic role demanded that the aircraft be capable of missions with a radius of at least with a load. The tactical role required it to be able to perform low-altitude air drops of supplies, as well as carry and drop combat paratroops.Lockheed C-141 Starlifter, The Aviation Zone The final version of SOR 182 was released in fall 1960, and requests for proposals were sent to Boeing, Douglas, Convair, and Lockheed-Georgia.
Lockheed's design team produced their own unique design in response to the requirement, internally designated as the Lockheed Model 300; it would be the first large jet designed from the start to carry freight. In comparison to the firm's previous utility transport, the turboprop-powered Lockheed C-130 Hercules, it was considerably bigger, as well as possessing greater speed and more power.Kirby 2011, p. 68. In terms of its basic configuration, the Model 300 was a large airlifter, furnished with a T-tail and a high-mounted swept wing, under which a total of four pod-mounted TF33 turbofan engines were fitted. The Model 300 possessed a lengthy, unobstructed cargo deck, which provided sufficient space and fittings to safely accommodate up to 154 troops or of cargo.
During March 1961, Lockheed's submission was selected as the winner. President John F. Kennedy's first official act after his inauguration was to order the development of the Lockheed 300 on 13 March 1961, placing an initial contract for five aircraft for test and evaluation, to be designated the C-141. One unusual aspect of the aircraft was that it was designed to meet both military and civil airworthiness standards. The prototype C-141A serial number 61-2775 was manufactured and assembled in record time, having been rolled out of Lockheed's factory at Marietta, Georgia on 22 August 1963. It was also the first aircraft to be designed and produced at the plant that would go into full-rate production.Kirby 2011, p. 50. The prototype performed its maiden flight on 17 December of that year, coinciding with the 60th anniversary of the Wright brothers' first flight.
In conjunction with the USAF, Lockheed subjected the prototype to an intensive flight testing program, which would involve five testing and evaluation aircraft. The first delivery of a production C-141 occurred during April 1965. Over the course of three years, a total of 284 C-141s were manufactured, excluding five aircraft constructed for testing purposes. Production of new-build C-141s ended in February 1968.
Derivatives
During the 1960s, Lockheed made efforts to market the aircraft on the civilian market; this resulted in provisional orders having been placed by both Flying Tiger Line and Slick Airways. These were to be a stretched version, longer than the C-141A, which was marketed as the or SuperstarLifter. Slick's order was ultimately for six firm, and Flying Tiger for eight. Other changes were also incorporated to adapt the design to be more suited to the commercial sector, including the use of a different control yoke. Following the satisfactory completion of civil testing, a Federal Aviation Administration (FAA) type certificate was awarded to the C-141 on 29 January 1965 to allow it to operate commercially. In summer 1965, go ahead on a commercial version seemed likely, but later that year Slick abandoned scheduled and domestic service. When no commercial sales were made, Lockheed donated the aircraft to NASA.Kirby 2011, p. 74.
Another, more ambitious proposal, commonly designated as SC.5/40, sought to combine elements of the Starlifter with another strategic airlifter, the turboprop-powered Short Belfast, was to be performed in partnership with the British aircraft manufacturer Shorts.Flight 19 September 1963, p. 508. For this variant, the fuselage of the Belfast would have been paired with the wing of the Starlifter, which would have readily enabled the adoption of turbojet engines; speculated engines to power the envisioned airlifter included the Pratt & Whitney JT3D-3 (18,000 lb) or JT3D-8 (21,000 lb), Rolls-Royce Conway 550 (21,825 lb) or Bristol Siddeley BS.100 (27,000 lb approximately).Wood 1975, p. 227. A broadly similar but improved proposal, designated as SC.5/45, was heavily promoted by Shorts for Operational Requirement ASR.364, partly on the basis that it would also enable a near-identical civil-orientated model to be produced for home and export use, designated as SC.5/41.Wood 1975, p. 231. Detailed presentations on the SC.5/41 and SC.5/45 proposals were reportedly made to both British Overseas Airways Corporation (BOAC) and to the Royal Air Force (RAF) respectively, but no orders were placed.Wood 1975, pp. 231–232.
Design
The Lockheed C-141 Starlifter is a long range strategic airlifter, designed for transporting large quantities of either cargo or passengers. It is powered by an arrangement of four TF33 turbofan engines, each capable of generating up to of thrust; these were installed in pods beneath the high-mounted swept wing. The underside accommodates the retractable tricycle landing gear, consisting of a twin-wheel nose unit and four-wheel main units, the latter of which retract forward into fairings set onto each side of fuselage. The flight deck is typically operated by a crew of four.
The use of a high-mounted wing enabled internal clearance in the cargo compartment of wide, high and long. Accordingly, the C-141 was capable of carrying, for example, a complete LGM-30 Minuteman intercontinental ballistic missile (ICBM) in its container; it was capable of carrying a maximum of over short distances, and carry up to when appropriately configured to carry the Minuteman, which lacked other equipment. In terms of personnel, the aircraft could carry a maximum of 154 fully-equipped troops, 123 paratroops or 80 litter patients at a time. In practice, it was discovered that, under typical conditions, the cargo deck of the C-141A would run out of volume before the maximum weight value could be reached.Kirby 2011, p. 72.
In terms of ground logistics, an important aspect of the C-141 was the floor height of the cabin being only above the ground, enabling easy access to the cabin via the large rear doors incorporated into the upwards-sweeping rear fuselage. This section is furnished with a large single-piece hydraulically-actuated loading ramp for simplified loading/unloading of both vehicles and general cargo. The two side-facing rear doors were designed to allow the type to be used for dropping paratroops (in August 1965, the C-141 performed the first such drop from a jet-powered aircraft). The rear cargo doors could be also opened in flight to perform airborne cargo drops.
Operational history
The prototype and development aircraft were involved in an intensive operational testing program, along with the first C-141 to be delivered to MATS (63-8078) on 19 October 1964 to the 1707th Air Transport Wing, Heavy (Training), Tinker Air Force Base, Oklahoma.C-141 Tail Number: 63-8078 USAFHRA Document 00495863 The first delivery to an operational unit (63-8088) was conducted on 23 April 1965 to the 44th Air Transport Squadron, 1501st Air Transport Wing, Travis Air Force Base, California.C-141 Tail Number: 63-8088
Although operational testing was still underway, as a consequence of the United States' military involvement in South Vietnam, the C-141 was quickly dispatched to the region to commence operational sorties within the combat zone. The type became heavily used throughout the latter stages of the Vietnam War, its transport capabilities being in high demand.Kirby 2011, p. 76. Even following the arrival of large numbers of C-141s in the Vietnam theatre, the type was never able to replace the C-124 Globemaster II fully due to its inability to transport outsize equipment in-theatre; this situation was later addressed by the introduction of the even larger C-5 Galaxy.Kirby 2011, p. 78. The final duties performed by the C-141 in the conflict were repatriation flights, bringing home thousands of American prisoners of war (POWs).Kirby 2011, pp. 76-77.
Despite some operational issues experienced, the C-141 formed the backbone of the USAF's strategic airlift capability during the late 1960s; it continued to hold this status through to the late 1990s.Kingsbury 2005, p. 20. On 8 January 1966, following the disestablishment of MATS, all C-141s were transferred to the newly established Military Airlift Command (MAC).Davis and Willson 2019, p. 79.
During October 1973, both the C-141 and the larger C-5 Galaxy airlifted supplies from the United States to Israel during the 1973 Yom Kippur War as part of Operation Nickel Grass. Over the course of the operation, C-141s flew 422 missions and carried a total of 10,754 tons of cargo."Operation Nickel Grass."Air Mobility Command Museum. Retrieved: 23 August 2014. By 1975, the C-141 fleet had reportedly accumulated an average of 20,000 flight hours each, two-thirds of their original rated life span.
Despite an early belief that the advantages of the turbojet over preceding propeller-driven cargo aircraft would render the latter obsolete, service experiences with the C-141 found that there was still a useful role for turboprop-driven utility transports such as the Lockheed C-130 Hercules. Capabilities such as short-field takeoff performance and suitability for austere airstrips meant that such aircraft proved useful, while the C-141 proved to be anything but robust, suffering numerous instances of structural failures.Ziman 2003, p. 298. Specifically, the C-141 fleet was troubled by seemingly random cracking through the wing area, which was, according to a report compiled by the Government Accountability Office (GAO), sometimes attributable to stresses imposed under certain types of missions undertaken. A planned remedial program during the 1980s to repair C-141 wing boxes uncovered significant corrosion and cracking, necessitating the replacement of all wing boxes across the fleet instead of making repairs.Kingsbury 2005, pp. 20, 23.