A Dozen Of The Most Unusual Variants Of The Ubiquitous KC-135 Family Of Aircraft
The KC-135A Stratotanker has been reworked into many different configurations, some of which are bizarre, to accomplish a dizzying array of missions.
Since its first flight on August 31st, 1956, there have been more than 80 variants of the KC-135A. For some of these, the differences were minor and often reflected only internal changes. For others, modifications significantly altered the appearance of the jet. In tribute to these many versions, The War Zone presents—as Rod Serling would say—for your consideration a dozen versions of the weird and wonderful. Selecting just 12 was insanely difficult, especially as the many testbed variants could easily account for twice that many.
12. It’s Just Paint.
Originally delivered in natural metal, the KC-135 has had relatively few color schemes. Coroguard was eventually applied to limit corrosion, later followed by a light grey. In the 1980s, Strategic Air Command (SAC) was concerned about tankers over Europe being shot down while in support of NATO, which prompted the hideously ineffective “Shamu” scheme of dark grey-green. This might have helped hide the KC-135 when viewed from above over cloudless terrain, but it made the jet more visible in the air and played havoc with the interior heat.
Today the jets wear a more effective grey. Still, there are a few KC-135s—too few, IMHO—that have sported unique paint schemes worthy of mention here.
In 1976, the American Bicentennial craze resulted in special paint schemes for just about every airplane in the inventory, but the then-Commander in Chief of Strategic Air Command (SAC) General Russell Dougherty was not convinced that his bombers and tankers should take part. Nonetheless, as this airshow image reveals, KC-135A 63-8012 did manage to sneak in a colorful scheme. At least one other jet had red, white, and blue striping on the engine cowls and around the nose radome.
Never let it be said that the French don’t know how to celebrate an anniversary, as C-135FR 63-8471 attests. There’s plenty of time to start planning the 80th anniversary of USAF KC-135s in 2037, which will probably be about the time the KC-46 is declared fully mission capable and retired to the Boneyard.
11. Civilian KC-135s?
Both the KC-135 and the Boeing 707 were derived from the company's earlier 367-80—famously barrel-rolled by the late, great “Tex” Johnston—but each was designed for separate markets: military and civilian. Nonetheless, two civil users—well, U.S. government agencies, to be precise—did acquire KC-135As. One of these helped put men on the moon, while the other helped make global commercial jet travel safer.
The original “Weightless Wonder” zero-gravity simulator was a Convair C-131, but the availability of spare KC-135s allowed for longer-duration training flights. Three different C/NKC/KC-135As were used at Wright-Patterson Air Force Base, Ohio, but by 1974 the Air Force wanted to divest the zero-g mission to NASA. KC-135A 59-1481 had a terrible maintenance record, which is why the Air Force offered it to NASA. That agency, not surprisingly, declined. After much bureaucratic wrangling and extensive repairs, however, it went on to fly 57,667 parabolas over its 22-year career. It would also support Space Shuttle transport flights alongside NASA’s 747s.
The Air Force was happy to shunt its hangar queens to civilian agencies, and, like NASA's KC-135, 59-1518 was in pretty sorry shape when the FAA asked for a jet. Not that the FAA did much better. As N96, it suffered maintenance issues throughout its career with the agency. The airplane flew intercontinental and domestic routes at high altitudes and jet speeds to evaluate existing air traffic control (ATC) procedures and instrument approaches.
Along with KC-135A N98 (59-1481 which went to NASA), what it found while executing its research mission was appalling, as the procedures and how the airways operated were designed for the previous generation of piston-powered airliners. As such, today’s air travel owes its safety to the two FAA KC-135As. N96 eventually returned to the Air Force in 1979 for conversion into an EC-135K Head Dancer airborne command post.
10. In the Navy
Much to the surprise of many SAC alumni, two NKC-135As served with the U.S. Navy.
As part of its electronic warfare training to the fleet, the Navy operated three ex-SAC B-47 bombers carrying electronic countermeasure (ECM) pods and jammers. These soon proved too old and too small for the expansion needed as electronic warfare technology evolved, so the Navy requested replacements.
In December 1977, 55-3134 and 56-3596 joined the Fleet Electronic Warfare Support Group (FEWSG) operated by Douglas Aircraft in Tulsa, Oklahoma, bristling with antennae and the Tree Horn and Tree Shark jammer pods capable of simulating a variety of foreign (read Soviet) aircraft that might attack a carrier task force.
9. Don’t Point Those at Anyone
Although SAC wanted to put ejection seats in the KC-135—Boeing said “no” because it might undermine public perception of the 707 airliner’s safety—there were never any plans to arm the tanker as it would not operate in a threatened environment. That didn’t mean the type wasn’t involved in aerial weapons tests, notably the Airborne Laser Lab (ALL), preserved today at the National Museum of the Air Force at Wright-Patterson Air Force Base, and precursor of the YAL-1A 747.
Interestingly, JKC-135A 55-3128 was involved with tests of wingtip-mounted rocket pods. Official records have yet to be uncovered that reveal exactly what these were, but they may well have been associated with test of the forward-firing AN/ALE-25 chaff rocket pods for the B-52.
8. Everyone Else Has Them, Why Not Me?
Look around at any airport and you’ll see them on just about every airplane designed and built since the 1990s. From hang gliders to 747s and A380s, winglets improve fuel efficiency and aerodynamic performance. First tested jointly with NASA in 1979 on NKC-135A 55-3129—previously a Weightless Wonder, with a bulkhead autographed by the Mercury Seven astronauts—they were never adopted for the KC-135 fleet.
Results were impressive though: 6.5% fuel savings per annum—45 million gallons of fuel at $0.86 per gallon = $38,700,000 saved—not to mention improved safety due to dissipation of wingtip vortices. SAC, however, opted for a computerized fuel/flight management system that offered a mere 2% savings if the jet was flown in an atypical airline flight profile and, for the first five years, never worked.
7. Nuke ‘Em ‘Til They Glow
Beginning with the October 31st, 1961 Tsar Bomba detonation monitored by JKC-135A 55-3127—it was not 20 miles away, but that’s another story—KC-135 variants have been used to assess dozens of atmospheric atomic tests from the United States, Soviet Union, and even France.
In an effort to ensure DoD support for the 1963 Partial Test Ban Treaty, Congress approved the purchase of three Early Day/Rivet Digger NC-135As as part of the National Nuclear Test Readiness Program (NNTRP). Each one was configured by the three U.S. atomic labs: Los Alamos Diagnostic Lab, Sandia National Lab, and the Lawrence Livermore National Lab. Each carried a variety of nuclear sensors, high-speed cameras, and technical equipment. Two—60-0369 and 60-0370—lacked all markings on the right side, while 60-0371 was unmarked on the left side to avoid flash burns to the paint from any the fireball. This proved unnecessary, but the paint scheme was retained anyway.
During one program, 60-0369 carried what is believed to be an ionization sensor mounted on a long strut off the right side of the forward fuselage.
6. Aim Right Here
As long as there’s been aerial gunnery, there have been aerial target towing aircraft, as well as target drones. Two KC-135 variants have served as “targets” for airborne laser experiments, beginning in 1977 with NC-135A 60-0371.
For tests with the YAL-1 747 laser platform, big crow NKC-135E 55-3132 acted as the target, simulating an incoming ballistic missile. To make sure the YAL-1’s sensors could see the “missile” clearly, a white ICBM was painted on the black forward fuselage to simulate re-entry against an exoatmospheric background. In addition, light and heat source emitters were placed at the exhaust of the “missile.” It worked, but the YAL-1 was canceled anyway.
5. Rockets, Missiles, and Capsules, Oh My!
During the early years of the US space program, scientists and engineers sought to understand the survivability of spacecraft as they exited and then re-entered the atmosphere. Several programs, such as the two JKC-135As that took part in Operation Skyscraper, tracked unmanned spacecraft immediately after launch and during re-entry. Beyond the pure research and “space race” benefits of these flights, there was a significant, but unmentioned, military component.
Efforts such as the Radiation Monitoring Program (RAMP) and Terminal Radiation Program (TRAP) built a database of American—never Soviet—missile and re-entry vehicle (warhead) infrared signatures. This would allow targeting of Soviet ICBMs during the boost phase, including by Kelly Johnson’s proposed Low Card laser-equipped U-2s hovering around the USSR, and incoming warheads.
Filled with cameras and infrared sensors mounted in a large dorsal fairing, JKC-135A 55-3134 operated from Patrick AFB, FL, unseen by the multitudes who watched rocket launches from the adjacent Cape Canaveral.
4. It’s Not a Tumor
Long before any new electronic equipment is installed on an operational platform, it undergoes extensive testing and evaluation. As part of the 1963 Reconnaissance Strike Program, JKC-135A 56-3596 tested the performance of the side-looking radar (SLAR) for the planned RB-58 Hustler. Eventually, this was replaced by NKC-135A 55-3132 in Recce Strike II associated with the Quill satellite-based bomb damage assessment (BDA) project, designed to provide SAC with real-time re-targeting data for use in its nuclear war plan.
Both aircraft had a huge fairing scabbed onto the right side of the fuselage plus a huge air intake on top for systems cooling, although this intake was later removed.
3. Does That Affect Your Gas Mileage?
Although NASA had ground communications and data stations around the world to link to satellites and its manned spacecraft, there were still gaps over the southern Atlantic and Pacific Oceans. For the Apollo moon missions, this was complicated by the rotation of the Earth.
In 1966, Douglas received the contract to install a 7ft diameter, 700 lb steerable antenna inside a 10 ft diameter nose on eight surplus C-135A transports. These were known as Apollo Range Instrumented Aircraft (ARIA). After Apollo 17 the name was changed to Advanced Range Instrumented Aircraft. As if these were not sufficiently ungainly, four were configured to carry the Airborne Lightweight Optical Tracking System (ALOTS) pod. This allowed an operator, sitting inside a plexiglass bubble atop the fuselage, to track and film rockets, missiles, and spacecraft during launch and re-entry. One ARIA was lost in a tragic accident over Maryland during a spouse orientation flight.
2. You’re Joking, Right?
When originally delivered, the KC-135 was equipped with Pratt & Whitney J57 engines. These used water injection to increase available thrust on initial takeoff, but were nonetheless woefully inadequate in terms of overall performance and fuel consumption. Indeed, there were some emergency situations where the KC-135 could neither climb nor accelerate after takeoff, all but guaranteeing the loss of a jet and its crew.
Consequently, SAC sought to re-engine its KC-135 fleet as a cost-saving alternative to procuring hundreds of new airplanes. In one example, two additional jets were mounted in a single pod on each wingtip and used only for takeoff.
Perhaps the most unusual proposal was Boeing’s KC-135ME—which stood for Mixed Engine—that, fortunately, never got off the drawing board. The outboard engines were still J57s, but the inboard engines were of the same caliber as today’s CFM-56 (F108) engines, figuring that it would halve the cost of the re-engining program.
Some ideas are best left untested…
1. You’ll Need a Lot More Than Four Engines
On the 4th of October, 1957, Americans were shocked by the Soviet Sputnik satellite. US defense planners, however, were far more concerned about the R-7 Semyorka rocket that launched it, as they quickly understood that its next payload could well be an atom bomb aimed at Washington, DC. This prompted a dedicated program to assess Soviet ICBM development, leading to specialist variants of the B-47 and RC-135.
One of these was the unique RC-135E Lisa Ann, later known as Rivet Amber. It carried a version of the massive Hughes radar installed on the island of the USS Enterprise to track incoming Soviet warheads to the Klyuchi Test Range on the Kamchatka Peninsula, and steered a Ballistic Streak Camera that filmed the event. The radar and associated equipment were far too big to fit in the jet, so the Big Safari conversion team extended the fuselage by 18 inches. No, this wasn't the advent of the longer “hog” nose on the RC-135, but a stretch of the actual fuselage—prompting Boeing to disavow all responsibility for the airframe.
Moreover, the four TF33 engines could not produce enough electricity to power the radar, so a Lycoming T55 engine was mounted in a pod beneath the left wing, and a heat exchange pod was installed under the right wing to dissipate the 1 million BTUs of additional heat generated by the radar. This gave rise to spurious claims of a “six-engine RC-135.” A fiberglass radome covered half of the fuselage over the radar, but it was not wrap-around, as some have claimed.
Rivet Amber was quite successful, and during May 1969 it collected evidence that proved the Soviet SS-9 Scarp’s three warheads were not multiple independently targetable re-entry vehicles (MIRVs).
Tragically, the RC-135E and 19 souls disappeared over the Bering Sea on 5th June 1969, likely the result of the failure of the vertical stabilizer following damage from severe turbulence during an operational mission the previous day.
So, that's our list. Which ones do you think should be on it? Let us know in the comments below!
Robert S Hopkins, III, is an independent scholar and aviation historian. Previously he was a US Air Force pilot and flew 17 different variants of EC-, KC-, and RC-135s. He has appeared on a variety of aviation programs on the BBC, Smithsonian, Discovery, NRK (Norway), and the History Channel. Hopkins earned a PhD in History from the University of Virginia and has published multiple books on the history of strategic airpower and aerial reconnaissance.
Contact the editor: Tyler@thedrive.com