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History and Development of the Lockheed C-5 Galaxy
School of Aeronautics, Liberty University
AVIA455: Turbine Engines and Jet Transports
March 5, 2024
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History and Development of the Lockheed C-5 Galaxy
The Lockheed C-5 Galaxy is a four-engine strategic transport and cargo aircraft with
a high cantilever wing and T-shaped tail. It was produced by the Lockheed Martin
Corporation and used by the United States Air Force (USAF). The prototype's first flight took
place on June 30, 1968, and until 1982, it was the biggest aircraft in the world. Only three
planes are bigger than it: the Russian An-124 Ruslan and An-225 Mriya from Antonov and
the A380 from Airbus (Eden, 2015). The C-5 will remain in service with the USAF until
2030. Development of the Galaxy began in the early 1960s to meet the USAF's CX-4 (later
CX-HLS) requirement. Surrounded initially by political and economic controversies, C-5
significantly enhanced the military aircraft command’s (MAC) ability to transport cargo
worldwide, especially when the country was involved in the Vietnam War (Eden, 2015). As
of 2023, four versions of this aircraft have been developed, owing to its strategic significance.
This paper delves into the history of this aircraft’s development and the innovative design
that underlies it.
Development Background
In the 1960s, the United States' "global strategy" was established, and the need to
strengthen "flexible response capabilities" and "strategic air mobility" was very urgent. In
early 1960, the U.S. Air Force proposed a "Special Operations Requirement" (SOR-214)
(Griffin, 2008). According to this operational requirement, the U.S. Air Force needed an
aircraft that could take off, land 'normally' on a field runway, and have a load capacity of
about 50 to 100 tons (Eden, 2015) - a strategic transport aircraft for intercontinental flight.
However, although the existing C-133 and C-124 transport aircraft of the USAF could still
meet the needs of the Army, they were nearing the end of their life cycle.
The C-141 transport aircraft in service could not effectively fulfill the transportation
task. Due to the width and design of the cargo compartment, the C-141 could not carry 7% of
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the airborne division equipment, 22% of the infantry division, or 32% of the armored division
(Reed, 2000). This gap only increased as the Army adopted more heavy equipment. It was
estimated that by the 1980s, more than a third of the light infantry divisions and more than
half of the total weight of the mechanized and armored divisions would have equipment that
exceeded the allowable width of the C-141 cabin (Petrescu et al., 2017). In addition, since
1960, the strategic focus of the United States has shifted from pure nuclear war to limited
traditional war, which also increased the demand for strategic transportation.
Construction History
In October 1961, the Military Air Transport Service (MATS) proposed the need to
replace the C-133 transport aircraft, and the Air Force planned the design of the CX-4.
However, in August 1962, the Army Vice Chief of Staff told the Air Force Chief of Staff that
the proposed design plan did not have a big difference compared to the C-141's transportation
capacity. The Army hoped that the maximum load capacity would be 82.5 tons and the cabin
width would be at least 4.5 meters to perform airdrop missions, take off, and land at relatively
simple airports (Eden, 2015). Under this proposal, the Air Force relaxed the takeoff runway
length requirement to 2,424 meters but shortened the landing runway length requirement to
1,212 meters.
At the end of October 1962, the Air Force System Command (AFSC), responsible for
research and development, launched the CX-X plan based on their research and predictions.
This plan used new technologies, but the service time was delayed. Later, it conflicted with
the Army's expectations. At this time, the Army's desired design included a 9,000-kilometer
range with a payload of 57.5 tons, a minimum cruising speed of 720 kilometers per hour, and
a 5.3-meter-wide cargo bay that could accommodate two transport platforms side by side
(Griffin, 2008). It could be moved up and down from the front and rear of the fuselage
simultaneously. In 1964, the program was officially renamed C-5A. In March 1964, the U.S.
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Air Force issued design requirements for an aircraft with four turbofan engines, a cruising
speed of Mach 0.77, and the ability to carry 50 tons. The cargo flight range was 9,900
kilometers, and the first flight was expected in July 1968.
Research and Development (R&D) Design
On April 27, 1964, the U.S. military began identifying contractors for the fuselage
and propulsion system of the heavy transport aircraft proposal (Heavy Logistics System, or
CX-HLS), which required four engines. On May 18, 1964, Martin Marietta, Lockheed-
Georgia, General Dynamics, Douglas, and Boeing competed for the fuselage, with Pratt &
Co. Whitney Company, Curtiss-Wright, and General Electric bidding for the engine. At the
end of 1965, Boeing, Douglas, and Lockheed submitted their design proposals. General
Electric Company (G.E.) and Pratt & Whitney (P.W.) also presented their respective high-
bypass ratio turbine engine designs (Hendry, 2023). The Air Force stated that it would select
the one they were most satisfied with from these three airframe designs for prototype
production and testing. The final order quantity would be around 200 aircraft. In August
1965, the military selected General Electric's engine design. On September 30, 1965, the Air
Force selected the Lockheed GL-500-13-7 design, the C-5A.
C-5A Test Flight Delivery
The plane that left the Lockheed factory at the beginning of 1968 was similar to the
Lockheed C-141 Starlifter. It was a four-jet aircraft with a high cantilever wing, T-shaped
empennage (tail), and incorporated cargo doors that could be opened mid-flight. However,
the front section of the fuselage was quite different from the C-141, especially concerning the
cockpit located over the front of the cargo hold (Reed, 2000). This arrangement, unusual for
the time, allowed the front part of the fuselage to "open" upwards, allowing volumes to be
loaded or unloaded from both ends of the plane simultaneously.
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Thus, the loading and unloading procedure could be unidirectional, which was
particularly advantageous if the load was vehicles, as they would not have to reverse (a
complicated and dangerous maneuver to do inside an aircraft and which could damage the
aircraft) to get on or off the plane. They could move inside the aircraft in only one direction
(Petrescu et al., 2017). A tank, for example, could enter from the front (when loading) and
exit from the back (when unloading) or vice versa. The Lockheed C-5A fuselage had two
floors capable of being used variably for passengers, cargo transport, or a combination of
both.
The C-5 transport aircraft made its first test flight at Dobbins Air Force Base in
Georgia on June 30, 1968. It quickly demonstrated its powerful flight transportation
capabilities in various test flights and evaluations. The aircraft set numerous records,
including landing with a weight of 300 tons in 1969 and taking off with a weight of 380 tons.
It could fly at Mach 0.8 at 10,000 meters and became the heaviest aerial oil-receiving aircraft.
It could also load 154 tons of fuel and 100 tons of simulated cargo and glide 360 meters after
landing.
In December 1969, the USAF's first C-5 transport aircraft was officially equipped
with troops. In June 1970, the first C-5A Galaxy was delivered to the 437th Airlift Wing at
Charleston Air Force Base in South Carolina, USA. In September 1970, the first C-5
transport squadron achieved operational capability at the Air Force base in South Carolina.
Beginning in 1970, the U.S. Military Airlift Command ordered 120 aircraft twice, which was
later reduced to 81 aircraft, and all were delivered in May 1973. The 81 aircraft produced
between 1969 and 1973 suffered from premature wing structure fatigue, so all aircraft had to
be fitted with a new reinforced wing (Leland & Wilcoxson, 2003). Fifty C-5Bs, more
powerful and with modified wings, were therefore built. Its modified C-5B made its first
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flight in September 1985 and began to be equipped with the U.S. Air Force in January 1986.
By the end of 1987, 25 C-5Bs were delivered. In April 1989, all 50 C-5Bs were delivered.
Development of the Latest Version
Initiated in the late 90s, the C-5 Galaxy modernization program was put into practice
at the request of the Air Mobility Command (AMC), which identified that military freighters
at this time still had more than 80% useful life and therefore decided to carry out an
aggressive modernization program that was divided into two parts (Griffin, 2008). The first
was the Avionics Modernization Program (AMP), which adapted the aircraft to the global
management of air traffic with better communication and air navigation systems, in addition
to new screens in the cockpit and a new autopilot system (Leland & Wilcoxson, 2003). The
second and last part was the Reliability and Reengineering Improvement Program (RERP),
which replaced engines and systems and made structural improvements to the fuselage and
landing gear.
Development of the latest version of the Lockheed Martin company aircraft, C-5M
Super Galaxy, began back in 2004. Flight tests of the first samples began in 2006 (first flight
- June 19) (Lockheed Martin Corporation, 2024). Like its predecessor, the aircraft's mission
remained unchanged: strategic cargo transportation during remote theaters of military
operations (Hendry, 2023). The aircraft is used for the landing and parachute landing of
troops, military equipment, and cargo, as well as evacuating wounded and injured personnel.
The C-5M Super Galaxy can fly 5250 nautical miles (9723 km) on an aircraft weighing
120,000 pounds (over 54 tons). Its predecessors of the same weight could only overcome
4350 miles (8056 km) (Lockheed Martin Corporation, 2024).
According to Lockheed Martin, after upgrading, the reliability of the aircraft
increased by 90%, and the payload increased by 20%. More than 70 improvements and
changes were made to the plane as part of the modernization program. The aircraft's
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maximum capacity was increased by strengthening the fuselage and updating the power
plant. The TF39-GE-1C engine was replaced by the more modern, reliable, and fuel-efficient
General Electric CF6-80C2 (F108-GE-100) engine (Lockheed Martin Corporation, 2024). In
the Lockheed Martin booklet, it is noted that the engine has a 22% increase in thrust, a 58%
increase in rate of climb, and a fuel savings of 10% compared to the previous version
(Lockheed Martin Corporation, 2024).
In 2018, Lockheed Martin announced the conclusion of the Lockheed C-5 Galaxy
modernization program after delivering the last unit to the United States Air Force in the
same year, twenty years after the start of the program. Fifty units have been modernized and
will continue flying for twenty-two years (Lockheed Martin Corporation, 2024). The C-5M is
scheduled to be used until around 2040 as it is being replaced with a new engine, the cockpit
is modernized, and the installation of latest navigation and communication system.
Conclusion
The Lockheed C-5 Galaxy was the largest aircraft worldwide until the Soviet Antonov
An-124 appeared. It was designed as a strategic transport aircraft capable of operating from
crudely developed terrain. The C-5A Galaxy made its initial flight in June 1966. This aircraft,
which can carry missile batteries as well as tanks or heavy artillery pieces, is characterized by
a 28-wheel landing gear, a high wing, four TF39-GE-1 turbofan engines, swept tailplanes, a
ventral loading ramp, and an articulated front fuselage. The cargo hold, which measures 37 m
in length, 5.80 m in width, and 4.10 m in height, has handling equipment, and the upper deck
is designed to accommodate 90 passengers. The two doors allow simultaneous loading and
unloading.
The C-5 Galaxy aircraft played a strategic role in transporting 500,000 passengers and
519,300 tons of equipment during the Gulf crisis. However, it is the most expensive aircraft
to maintain in the American Army. The C-5M will be used until around 2040, as it is being
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upgraded with a new engine, a modernized cockpit, and the latest navigation and
communication systems. Due to its colossal size, the C-5 was only introduced by the USAF
and has not been exported since.
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References
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Hendry, J. (2023, November 25). An absolute unit: Everything you need to know about the
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