We are all familiar with the 747 and some of its variants, such as the Dreamlifter and Air Force One (VC-25). How about some of the lesser-known variants, some designed for very specific roles, while others never even left the drawing board.
E-4 Advanced Airborne Command Post (AACP). Photo Balon Greyjoy /commons.wikimedia.org
Referred to as the "Nightwatch" aircraft, the E-4 is an airborne command post designed for use in the case of nuclear war. Four of these specially modified 747-200Bs were built. Formerly known as the National Emergency Airborne Command Post ("Kneecap"), it is now referred to as the National Airborne Operations Centre (NAOC)
Cruise Missile Carrier Aircraft (CMCA) Image Boeing
During the search for a replacement for the U.S. Air Force's ageing fleet of B52s, a suggestion was made by Boeing to the U.S. Air Force to modify 747-200Cs to carry and launch 70 AGM-86 ALCM fitted on rotary launchers. Boeing's aim was to create a low-cost bomber, at 15 per cent the price of the B-2 Stealth Bomber, but with a big advantage being that the enemy would find it difficult to differentiate them from civilian 747s and would also make it flexible enough to land at civilian airports without raising alarm. However, this plan was abandoned in favour of more conventional strategic bombers.
YAL-1 Airborne Missile Défense System. Photo YAL-1A. Photo by US Missile defence Agency / commons.wikimedia.org
An experimental Airborne Laser, planned as part of the U.S. National Missile Defence , armed with a megawatt-class chemical oxygen iodine laser (COIL) mounted on the nose of a modified Boeing 747-400F. Mainly designed as a missile defence
system to destroy ballistic missiles in their "boost phase". the aircraft was designated YAL-1A in 2004 by the U.S. Department of Defence. When fired, the laser produced enough energy in a five-second burst to power a typical American household for more than an hour. A high-energy laser was used to intercept a test target in January 2010, and the following month, successfully destroyed two test missiles. Funding for the program was cut in 2010 and finally cancelled in December 2011 as the laser did not have enough power or range to destroy a missile launched from a hostile environment. It made its final flight on February 14, 2011 to Arizona to be kept in storage at the "Boneyard
and was ultimately scrapped in September 2014 after all usable parts were removed.
Shuttle Carrier Aircraft (SCA). Photo by NASA / commons.wikimedia.org
NASA's Space Shuttles had alternative landing sites as far as Europe that could be chosen as circumstances changed. To retrieve the shuttles, two 747s were modified by NASA to ferry Space Shuttles from landing sites back to the Kennedy Space Centre. The first SCA was a 747-100 and the second a 747-100SR. Modifications included additional vertical stabilizers, a ballast and an internal escape slide behind the flight deck to allow the crew and other NASA personnel to bail out in the case of any serious mid-air failure. It takes 170 personnel a week to prepare the Shuttle and SCA for flight. With the Shuttle attached performance was reduced to a ceiling of 15,000 feet and a maximum cruise speed of 386 kts/ 716 km/h.
Airborne Aircraft Carrier (AAC). Image by Stefanobiondo / commons.wikimedia.org
On long range tactical missions, bombers usually fly with a fighter escort. Bombers can fly for hours on end, however fighters could not. So, what could be done? How about carrying the fighters with the bombers and deploying them when needed? Thus, started research by Boeing under contract of the USAF for an "airborne aircraft carrier" carrying up to 10 with the ability to launch, retrieve, re-arm and refuel them. Boeing believed that the scheme would be able to deliver a flexible and fast carrier platform with global reach. Needless to say, the scheme never got out of the design stage.
747 Supertanker. Photo by Fire Aviation.
Modified for firefighting, the 747 Supertankers were 3 different 747s modified to carry 76,000L of fire retardant or water. The first was a 747-200 that never entered service, the second a 747-100 originally meant for Delta Airlines and the third and only active Supertanker today, a 747-400 converted and operated by Global Supertanker Services.
Stratospheric Observatory for Infrared Astronomy (SOFIA). Photo by Jim Ross /NASA / commons.wikimedia.org
The creation of a joint venture between NASA and DLR (German Aerospace Centre) a former Pan Am Boeing 747SP was modified with a large door in the aft that can be opened in flight to a 2.5 m diameter . The telescope is designed for at altitudes of around 41,000 ft, above almost all the water vapor in the atmosphere, which blocks infrared waves. SOFIA can also travel above almost any point on the earth's surface, allowing observation from the northern and southern hemispheres.
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