The United States Air Force (USAF) initiative that eventually begat the Lockheed C-5 "Galaxy" heavy-hauler was born from an effort to produce a long-range partner to operate alongside the existing USAF fleet of Lockheed C-141 "Starlifter" strategic transports. The complementary-minded C-5 was designed along the same strategic "heavy-hauling" (i.e. "out-sized") lines but became a much larger, more ambitious program which ultimately faced a variety of hurdles, both politically and technologically, before it became the robust, reliable platform seen today. While similar in mission scope to the C-141, the C-5 was to provide better performance and a longer-range, unrefueled cargo-hauling capability when ferrying dimensionally larger, heavier loads to points anywhere in the world - all this while operating from conventional airstrips and even unpaved landing zones.
The new aircraft arrived by way of the USAF's ever-evolving heavy-haul-minded programs of the 1960s that ultimately became the "Cargo Experimental - Heavy Logistics System" (CE-HLS). The service sought a four-engined product with a payload capability of 250,000lb flying over ranges of 3,000 miles without requiring aerial refueling. Because of the operating weights and power involved, it became obvious that a wholly-new fuel-efficient engine would be required. Additional qualities called for a fuselage with front and rear cargo access for "straight-through" loading / unloading.
The new proposal was drawn up in 1964 and some of the more traditional "big aircraft" American manufacturers responded like Boeing, Douglas, and Lockheed. These three passed into the design study phase and General Electric was commissioned to develop the engine. In the end, the Lockheed proposal won out over the others on cost despite authorities favoring the Boeing submission. The official announcement came in September of 1965 and the engines became the General Electric "TF39".
The Lockheed aircraft carried shoulder-mounted, swept-back wing mainplanes to which each held a pair of underslung engine nacelles towards their leading edges. The flightdeck was seated over a short, downward-sloped nose cone giving a commanding view of the ground ahead. The nosecone was hinged to open upwards allowing access to the hold within the body of the aircraft. The tail unit was raised aft of center mass to provide unrestricted access to the rear cargo area. The tail itself was arranged as a "T-style" assembly in which a single vertical fin supported very-high-mounted horizontal planes (these planes also swept-back). To round out the list of details, a multi-wheeled / multi-legged undercarriage configuration relying on new fewer than 28 wheels (!) was used to better balance the heavy aircraft on runways. The typical crew numbered seven to include three loadmasters and two flight engineers.
The cargo hold was designed to be large enough to accept a Sikorsky UH-60 type helicopter or similar up to the more modern Boeing V-22 Osprey systems. Beyond aircraft, the hold could also support all manner of cargo palettes and military vehicles giving the USAF a comprehensive heavy-lifter regardless of operating theater.
When introduced in 1970, the C-5 Galaxy became the largest aircraft in the world and remains one of the largest today (2016) - its dimensions include a wingspan of 222.8 feet, a length of 247 feet, and a height of 65 feet.
First-flight of a Galaxy was recorded on June 30th, 1968 and the aircraft was already proving heavier than initially planned. This added stresses to the wide-spanning wings which forced several modifications to their design. The expected payload capability, therefore, was decreased some. Beyond technical issues with such an expansive project, the inherently ambitious nature of the entire program ensured that the C-5 would become an expensive beast to develop and procure - the product indeed came under fire from Congress on several occasions during its development phase. Testing finally ended in 1969.
Ultimately the bloated program yielded some fruit in the arrival of the first production form - the "C-5A". Formal service introduction followed in June of 1970 with deliveries to the 437th Airlift Wing (Charleston AFB). At this time, Lockheed faced financial troubles that required government support simply to keep the C-5 program alive. In 1976 it was revealed that the wings, in an effort to address payload/range performance, were made too light in their design and proved prone to cracking so a new initiative was established to "re-wing" C-5As. Other welcomed changes included introduction of the TF39-GE-1C engines of 43,000lb thrust which increased the Maximum Take-Off Weight (MTOW). This work was completed from 1980 through 1987.
The "C-5B" was born from the revised A-model as an improved form and was born in 1982, arriving for service in 1986. Beyond the A-model introductions (including the wings), upgraded General Electric engines, updated avionics, and a revised undercarriage greeted the mark. A first-flight of a C-5B was recorded in September of 1985 and 50 total units were delivered from 1986 until 1989.
From the B-models came the "C-5C" which were technically recognized as C-5A(C) SCM = "Space Cargo Modified". As their name implied these were developed with increased internal volume in mind though only two of this mark were completed. The aircraft have served NASA with out-sized cargo delivery.
In 1998, the Galaxy fleet was modernized as a whole under the "Avionics Modernization Program" (AMP) and nearly all facets of the avionics fit were improved including cockpit displays and the autopilot system. Following in 2006 was a new program (RERP = "Reliability Enhancement & Re-engining Program") to address engines in an effort to extend the service life of the aircraft - the General Electric F138-GE-100 series of 50,000lb thrust each were introduced as a result. These units now promoted shorter take-off runs and a better climb-to-altitude rate while other facets of the large aircraft were further addressed to keep the mammoth machine flying for decades to come. The latest incarnation, based on this modernization program, has become the C-5M "Super Galaxy".
Beyond these produced variants were several unrealized forms - the "L-500" was a proposed civilian-minded model that came to naught, not only due to Lockheed's troubles but also because it managed little commercial interest. Another short-lived offshoot was a specially-modified C-5 to serve NASA's shuttle program as its space shuttle "carrier". The program eventually pursued the Boeing 747 for the role instead.
The C-5 series has served under the banners of Military Airlift Command / Air Mobility Command, Air Education & Training Command, the Air Force Reserve, and the Air National Guard. It has seen combat service (in a support role) since the Vietnam War (1955-1975), was critical to coalition operations in the 1991 Gulf War and in Yugoslavia later that decade, and - more recently - in serving coalition forces operating in Afghanistan. Beyond its obvious military value, the product has also contributed to multiple humanitarian, missions around the world.
Because of the project's infamous cost overruns, the C-5 Galaxy came to be known by some as the "Fantastic Ridiculous Economic Disaster" - or "FRED". The "Galaxy" name continued the Lockheed space-minded naming convention for its big aircraft products - "Starlifter", "Constellation", and so-forth.
C-5A models were produced from the period spanning 1968 to 1973 while C-5B models were manufactured from 1985 until 1989. Totals reached 131 of both systems, 81 A-models and 50 B-models. It is intended by the USAF that the C-5 family will continue to fly into 2040. The current (2016) inventory states 26 C-5A and 52 C-5B/C/M models in service.
August 2018 - Lockheed Martin delivered its final production C-5M (Modernized) Galaxy to the United States Air Force on August 2nd, 2018. The upgrades involved modernization of key systems, such as diagnostics, avionics and engines, to extend the service lives of these mammoth aircraft into the 2040s.
C-5 "Galaxy" - Base Series Designation
C-5A - Initial production model series; 81 examples delivered; most re-winged in later years to counter structural weaknesses.
C-5B - Improved C-5A with improved automatic flight control system; redesigned and simplified undercarriage; new engines and wings for extended service life.
C-5C - Pair of modified C-5A models for satellite carriage (outsized space cargo operations); two examples completed.
C-5M "Super Galaxy" - Modernized Galaxy aircraft fleet.
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