Boeing KC-135

Boeing KC-135 Stratotanker
A KC-135R of the United States Air Forces in Europe
Type:	Tanker aircraft
Design country:	United States
Manufacturer:	Boeing
First flight:	August 31, 1956
Commissioning:	June 1957
Production time:	1954 to 1965
Number of pieces:	808

The Boeing KC-135 Stratotanker is a four- engine tanker aircraft developed in the 1950s for the United States Air Force (USAF) . It replaced the Boeing KC-97 . In addition to air refueling, it is also used to transport cargo and troops. It is a sub-type of the variant C-135 family, which, like the Boeing 707, is based on the Boeing 367-80 . In 1954 initially intended as an interim solution, the US Air Force ordered a total of 732 KC-135A units. Since then, the model has been converted many times and equipped with more modern turbo engines. In October 2014, around 422 aircraft were still in use worldwide, 397 of which were in the US Air Force and around two dozen in France , Turkey and Singapore . In all military conflicts in the United States since the late 1960s, this model played a crucial role in supporting fighter jets , bombers and reconnaissance planes , the range of which was increased considerably by aerial refueling. In the US Air Force, machines of this type, with an average age of over 50 years , are the oldest still active aircraft , alongside the Boeing B-52 .

Development history

origin

The Strategic Air Command (SAC), founded in March 1946 after the Second World War , had the task of attacking targets with long-range bombers in an emergency . To do this, it had B-29 bombers and, from 1948, B-50 bombers as well , but they had no intercontinental range. As a result, bases far away from home remained indispensable for refueling.

The US armed forces wanted to reduce this dependency through the introduction of new long-range bombers and the further development of the up to then rather experimentally operated air refueling . The first tanker aircraft of the SAC were converted B-29 and B-50, from 1951 KC-97 were added. The refueling was initially carried out by gravity via a hose from the higher-flying tanker to the recipient aircraft flying lower behind.

Starting in 1948, Boeing experimented for the first time with a rigid, controllable telescopic boom , the flying boom , which is still in use today . With it and by means of pressure refueling, transfer rates of around 2300 liters per minute could be achieved instead of around 950 l / min with the hose system.

After the jet-powered B-47 bomber went into service with the US Air Force at the end of 1951, it was only refueled in a very unsatisfactory manner by the propeller -powered tanker aircraft. Because of the vastly different flight performance , the rendezvous required for this could only take place at relatively low altitude and speed and while descending. The additional fuel consumption of up to 50 percent of the fuel that had just been taken up, caused by the subsequent climb to the operational altitude, further reduced efficiency. The impending introduction of the B-52 bomber made the procurement of jet-powered tankers inevitable.

Boeing's universal prototype

Boeing had already started studies for passenger and transport aircraft with the new jet drive in the mid-1940s . But the airlines feared that the operating costs would be too high, and in the fall of 1951 the Air Force also rejected the proposal for a revised C-97 (Model 367) as a jet-propelled tanker. It invested primarily in new strategic bombers and did not want to finance the development of a tanker as well.

So in the spring of 1952, Boeing decided to build a demonstration aircraft at its own expense and risk. On April 22, 1952, the Boeing Board of Directors approved $ 15 million for the development and production of the Boeing 367-80 , later increased by another million.

The rollout took place on May 14, 1954 in Renton , Washington , two months ahead of schedule. The machine, also known as the Dash 80 , made its first flight on July 15, 1954.

USAF decisions

In November 1953, the Strategic Air Command recommended the purchase of 200 tankers for the 1954 budget year for the first time . In the meantime, the US Air Force had various draft proposals, in addition to Boeing's 367-80, the draft for a Douglas tanker with J67 jet engines from the the Douglas DC-8 and the Douglas XC-132 were developed. On May 5, 1954, the Air Force invited Boeing , Consolidated Vultee Aircraft Corporation , Douglas , Fairchild , Lockheed and Martin to an official tanker tender, although Martin refused. However, Boeing's four remaining competitors calculated at best theoretical chances of being taken into account in the decision planned for August 27, 1954. Because while the Dash 80 was already rehearsing air refueling maneuvers with a B-52 on its seventh flight on July 22, 1954, the competition proposals only existed on the drawing board until then. In addition, Boeing had influential advocates, especially the then SAC commander, General Curtis E. LeMay , who did not tolerate any further delay in the procurement of tankers.

On August 3, 1954, the US Air Force decided to purchase 29 tankers based on the Boeing design for $ 150 million as an "interim solution" until the final competition winner would be ready for use. About two weeks later - and still before the end of the bidding process - she increased the order by another 88 copies for $ 240 million. The new tanker and transport aircraft was given the military designation KC-135A Stratotanker . Boeing used the model number 717 for this. Compared to the Dash 80, the fuselage diameter increased by around 30 centimeters. On July 13, 1955, Boeing received approval from the USAF to produce a civil aircraft in addition to the tanker version. Boeing then marketed this civilian version of the 367-80 as the Boeing 707 and received its first order from Pan American World Airways on October 13, 1955 . Compared to the C-135 line, it has a trunk diameter that is 10 cm larger. The Air Force feared that Boeing was not paying enough attention to the KC-135. It therefore demanded a promise that the B707 project will not delay the production of the Stratotankers under any circumstances.

It was only in February 1955 that the Air Force announced Lockheed as the winner of the tanker competition. But while Lockheed was only allowed to build a prototype (based on its L-193), Boeing's order was increased again by 169 KC-135A. By now it was clear that the winner of the tender was also one of the losers, because the USAF never intended to operate two similar types of tanker at the same time in the years that followed - for cost reasons alone.

The paradoxical outcome of this competition sparked criticism and protests and culminated in an investigation by the US Congress , which came to the conclusion in February 1956 that the Air Force had improperly supported Boeing in the construction of the 367-80, including by the Provision of factory buildings and delivery of military J57 engines for commercial use. These findings did not change anything in the tanker business, since the KC-135 was the only design available at short notice.

Production contract

Production of the KC-135

Type	Model no.	Block no.	USAF serial number	number
KC-135A	717-100A	1-4	55-3118 to -3146	29	732
	717-146	5-7	56-3591 to -3658	68
	717-148	8–10 / 1 10/2 11–14 15–17 18 19–21 22–24 / 1 24 / 2–26 / 1 26/2 27	57-1418 to -1514 57-2589 to -2609 58-0001 to -0130 59-1443 to -1523 60-0313 to -0368 61-0261 to -0325 62-3497 to -3580 63-7976 to -8045 63- 8871 to -8888 64-14828 to -14840	97 21 130 81 56 65 84 70 18 13
KC-135B	717-166	1	62-3581 to -3585 63-8046 to -8057	5 12	17th
C-135F	717-165	1 2	63-8470 to -8475 (F-UKCA to -UKCF) 63-12735 to -12740 (F-UKCG to -UKCL)	6 6	12

The US Air Force and Boeing began contract negotiations on December 13, 1954, which culminated in a first production contract for the KC-135A on September 30, 1955: Boeing undertook to build 29 machines for $ 6.82 million each. In addition, there were 15.66 million for the initial equipment of spare parts, 1.16 million for manuals and technical documentation and 1 million for an additional hull for static tests. The output should be 13 aircraft per month in Renton, the acceptance flights should take place at Larson Air Force Base . The actual price was finally $ 7.48 million per aircraft in October 1958.

The second contract for 68 tankers followed on June 5, 1956, 20 fewer than planned in August 1954. Another eight contracts up to 1964 totaled the orders for the A-model alone to 810 machines, of which 732 were ultimately built.

Rollout and first flight

The first series machine, a KC-135A, was presented to the public at the festive rollout on July 18, 1956 at Boeing's Renton plant . The wife of Renton's Mayor Joseph R. Baxter named the new tanker (USAF serial number 55-3118) the City of Renton with a bottle of water from nearby Cedar River . A few minutes before the first KC-135, the last of a total of 888 C- 97s had also left the workshop. The Dash 80 and a B-52 then flew over the event in greeting.

After some ground tests, the KC-135A took off on its maiden flight on August 31, 1956 , which lasted an hour and 19 minutes. There was no prototype with the designation XKC-135 or YKC-135, as Boeing was able to carry out most of the pre-production tests with the 367-80. The US Air Force took over the 55-3118 on January 24, 1957 and flew it to Edwards Air Force Base for further testing .

Tests and flight trials

After several Comet passenger jets crashed due to material fatigue in 1953 and 1954 , the US Air Force ordered in October 1955 that the KC-135 fuselage be specially examined using hydrostatic tests. Boeing took the eighth fuselage (without serial number) from ongoing production and sunk it in a 1.6 million liter tank. Different flight phases were simulated by increasing and decreasing the internal pressure. 14 hydraulic rams simulated external influences such as wind gusts and steering forces. A test cycle represented six hours of flight. After 12,155 cycles (corresponding to 72,930 flight hours), the first cracks appeared in the outer skin at the end of 1957. The weak points have been strengthened in aircraft that have already been delivered and series production has been adapted.

The flight tests of the KC-135A in 1957 and 1958 showed significantly improved flight performance compared to the previous KC-97 tankers. The flight altitude for in-flight refueling rose from around 5500 meters (18,000  feet ) to the operating altitude of the strategic bombers of around 10,700 meters (35,000 feet). The maximum operating altitude was 12,000 m, the rate of climb was 671 meters per minute, the maximum take-off weight was 134.7  tons . With 100,000 liters, the new Stratotanker was able to transfer almost twice as much fuel in flight as a KC-97F (56,700 l), with a transfer rate of up to 3400 liters per minute.

KC-135 on a “wet” start with J57 engines and water injection

In addition, however, some problems also emerged, some of which took years to resolve. Boeing was able to remedy the poor controllability of the tank boom very quickly with a hydraulically supported control system. The insufficient stability around the vertical axis proved to be more persistent . It manifested itself in high-frequency flutter of the fin at speeds above Mach 0.8  and in pendulum movements of the tail ( Dutch Roll ), especially when flying slowly. This should be remedied by stiffening the vertical stabilizer and a yaw damper , which is controlled by the autopilot , which is already provided . This Lear MC-1 system itself suffered from massive development problems, so that the first series machines were delivered without an autopilot - and therefore without a yaw damper - and repairs were repeatedly necessary in the following years. From 1962 onwards, Boeing revised the vertical stabilizer again: the height increased by around one meter, the rudder was given a larger area and hydraulic power amplification.

The greatest shortcoming of the Stratotanker, however, was the low propulsion power. Depending on the atmospheric conditions, the fully loaded KC-135A with the standard J57-P-43W engines with water injection required a taxiing distance of 2800 to 3300 meters - a runway length that not every USAF air force base could show. In the event of an engine failure during take-off and a take-off weight of over 119 tons, the take-off had to be aborted. The result was weight restrictions until the KC-135 fleet was upgraded to E and R / T models from 1982 onwards with more powerful turbofan engines .

technology

Fuselage and tail unit

Cockpit of a Boeing KC-135A

Cargo door and access hatch of a KC-135A

The KC-135 is a four - jet low- wing aircraft with 35 ° swept wings and a conventional tail unit . The 39.3 m long, windowless hull is completely pressurized and is divided into the main deck with cockpit , cargo space and a luggage compartment and the lower deck, in which the entry area in the bow, three fuel tanks, the landing gear shafts, the water injection tank (only A- and Q- Version) and in the stern the tank boom operator's compartment is located. The loading space measures 24.7 m in length, 3.28 m in width and 2.11 m in height and offers around 170 m³ of space for six standard pallets of the type 463L and a maximum of 37.6 t of freight. The KC-135A offered 80 seats along the sides, which could be increased to 160 seats with an additional row of double seats. The KC-135R has room for 37 people in the hold as standard. After conversion for MedEvac inserts, up to 44 patients can fit in on stretchers. A 2.97 m wide and 1.98 m high, upward-opening cargo door on the left-hand side in front of the wing is used for loading. The KC-135 does not have a bow or tail tailgate, so that the cargo has to be lifted to a height of three meters with a forklift or lifting platform .

Like the fuselage, the wings are mainly made of aluminum. They have a wingspan of 39.88 m and an area of ​​226.0 m². This results in an aspect ratio of 7.0. They each have an aileron for low and high speeds, spoilers and landing flaps . From 1959, Boeing retrofitted slats . This reduced the stall speed by 11 km / h.

The landing gear consists of a nose landing gear with two wheels and two main landing gear supports with four wheels each under the central fuselage.

The crew includes the pilot, co-pilot, navigator and boom operator. After the KC-135 received modern navigation aids and a digital cockpit as part of the Pacer CRAG conversion program (CRAG for Compass, Radar , GPS ) in the mid-1990s, the navigator's workplace was no longer required.

drive

The KC-135 is powered by four jet engines that are individually attached to pylons below the wings. So far, three different types have been used: J57, TF33 and F108.

The Pratt & Whitney J57 , developed for the Boeing B-52 in the late 1940s, is a second-generation turbojet engine. The first three KC-135A received the J57-P-29 with a thrust of 47  kN , the next 26 the J57-P-31W. Boeing replaced this in 1956 with the more modern J57-P / F-43W (50 kN) also manufactured by Ford . Due to poorly forged titanium blades, it had to be replaced from October 1956 by the 180 kg heavier, but also 100,000 dollars cheaper J57-P / F-59W (50 kN), with which all KC-135A, -D and C-135F were equipped from now on .

The engine bleed air is used for pneumatic starting of the engines, for de-icing and it supplies the air conditioning system and the pumps for water injection . This injection made it possible to increase the thrust per engine at take-off by around 10 kN. The tank for the demineralized water was located in the fuselage between the main gear shafts and held 2,536 liters, which was sufficient for a maximum of two minutes of injection. The system was cumbersome and expensive. If the temperature on the floor fell below −7 ° C, the water had to be drained. If the water injection failed during the take-off run of an engine, the asymmetrical thrust often left the take-off aborted. Before the next start, the water tank first had to be refilled. In the 1950s, the treated water cost almost as much as kerosene and first had to be elaborately produced or brought here on remote bases.

With the introduction of the TF33, the military version of the Pratt & Whitney JT3D , from 1981 onwards, water injection could be dispensed with, as the turbofans provide up to 30% more thrust than the J57. The KC-135B received the TF33-P-9 with 71.4 kN, the KC-135D and -E took over used JT3D-3B (TF33-PW-102, 80 kN) from civilian B707 . Only the latter have thrust reversers .

The F108, the military name of the CFM56-2 , has powered the KC-135R and -T as well as the C-135FR since 1982. The turbofan drive units with a high bypass ratio are with 98.5 kN again much stronger than the TF33 and meet more modern requirements for noise and exhaust emissions. During the conversion program from September 1981 to June 2005, Boeing equipped the US Air Force 420 KC-135, 14 for France, seven for Turkey and four for Singapore with F108.

The standard fuel for the Stratotanker was initially JP-4, until the Air Force replaced it with JP-8 in the 1990s . Alternatively, the JP-5 of the marine or civilian fuel (Jet A, A-1 / Kerosene and B) can be used.

Tank system

Workplace of the boom operator, here refueling a B-52 Stratofortress

The Stratotanker has a total of ten fuel tanks, three each in the two wings (8660 liters, 7825 l and 1650 l reserve), one in the lower deck between the wings (27,670 l), one each in the lower deck in front of (21,980 l) and one behind the wings ( 24,285 l) and one on the main deck at the end of the hold (8,265 l). If the tank is not installed on the main deck, only three of the four cells of the foremost tank (then 17,060 l) may be filled in order not to shift the aircraft's center of gravity too far forward. All in all, a KC-135R can hold a maximum of 118,470 liters of fuel and, apart from a reserve of around 2300 liters, also release it back into the air. The A version had a total capacity of 113,560 liters. The fuel can be pumped between all tanks, only the KC-135Q had two separate fuel systems in order to be able to transport and transfer special fuel. Eight KC-135 can even be refueled in the air, as they were previously used for special operations. The filling opening is on the front side above the cockpit.

The boom for refueling other aircraft is located below the stern. Refueling is carried out from a compartment at the end of the lower deck. Here the boom operator lies face down on a platform and controls the position of the tank boom with his right hand and its length with his left.

Refueling container with hose and funnel

This flying boom consists of two tubes pushed into one another, the total length of which can be varied telescopically between 8.5 and 14.3 m. The inside diameter of the fuel line is around 10 centimeters. It is controlled by two rudder surfaces (ruddevators) that move with hydraulic support. In the rest position the boom rests on the tail cone of the fuselage, in the typical operating position it is inclined downwards by 30 ° and extended to 12.2 m. Movements of 30 ° to both sides and up to 50 ° downwards are possible. Various markings and light signals show the pilot of the receiving aircraft the correct position for contact. Once the boom operator has hit the filler neck of the receiving aircraft, the connection is mechanically locked and the refueling process is started via electrical contacts according to the specifications (quantity, pump power). The transfer rates are between 570 and 1700 liters per minute for combat aircraft and other small machines and up to 3400 l / min for large transporters and bombers, at a pressure of 3.5  bar . Refueling takes a few minutes, for example with an F-16 Fighting Falcon or up to over half an hour with a C-5 Galaxy .

Installation of the hose adapter on the tank boom of a KC-135E

Conversely, the Flying Boom can also be used to refuel the KC-135 from another aircraft, which has happened several times in emergencies, as well as using the tank boom as a “tow bar”.

Since the mid-1990s, 20 of the more modern KC-135R have had brackets for two external Mk 32B-753 refueling containers from the British manufacturer Flight Refueling . The 4.4 meter long containers with a diameter of 0.9 m can be attached to the underside of the wing tips if required. They house a hose reel that unwinds the hose with a catch funnel over a length of 24 m. At the top of the tank there is a dynamic pressure turbine with a two-bladed rotor that drives the fuel pump and winch, so that the system can work independently of the KC-135's power supply if necessary. The pumping capacity is 1500 liters per minute. A Stratotanker equipped with this Multipoint Refueling System (MPRS) can transfer its fuel to other USAF aircraft with a rigid boom as well as to aircraft of the US Marine / US Marine Corps and NATO with a hose boom . A hose adapter (Boom Drogue Adapter, BDA) can also be mounted on the rigid boom of all KC-135 for refueling these types of aircraft with a tank probe .

variants

overview

Two-sided drawing

• KC-135A: First model, 732 pieces with Pratt & Whitney J57 engines produced from 1956 to 1964.
• KC-135B: 17 newly built specimens from 1963 onwards, flying command post of the SAC. Renamed to EC-135C in 1965.
• KC-135D: Tankers created in 1979 from RC-135A , four pieces.
• KC-135E: A models equipped with new TF33 engines from 1982 , 160 pieces, 110 of which are still in service with the reserve forces. With up to 49 years of age, the E-models are the USAF's oldest still active aircraft.
• C-135F: Export model of the KC-135A for France , twelve pieces.
• KC-135Q: Between 1961 and 1968, 56 KC-135A were converted to refuel the Lockheed SR-71 with specialty fuel.
• KC-135R: 365 from 1982 onwards, including modernized A and E models with F108 engines. Also in use in Turkey and Singapore .
• KC-135T: Q models modernized from 1993 to 1995 with F108 engines to the level of the R models, 54 pieces.

KC-135A

The KC-135A is the original version of the Stratotanker and the only newly built tanker version for the US Air Force. From the beginning of 1956 to the end of 1964, Boeing produced 732 units in 27 blocks. Apart from the test aircraft, the USAF took over the first machine on June 28, 1957 for the 93rd Air Refueling Squadron at Castle Air Force Base , California , where crew training took place. At the end of the same year, the Air Force put the first KC-135 into service for regular missions. The last A-model (USAF serial number: 64-1480) reached its unit on January 12, 1965. Quite a few KC-135s have been converted into a variety of variants over the years, including JKC-135 and NKC-135 for testing, EC-135A and -L as airborne command posts and relay stations, and RC-135 for reconnaissance purposes. A total of 56 KC-135Qs were built between 1961 and 1967 for the transport and distribution of special fuel for the SR-71 and its predecessors .

From 1981 the Air Force had most of the KC-135A modernized. Around 160 machines received more powerful turbofan engines of the type TF33 and then the designation KC-135E . Around 345 copies were upgraded to KC-135R from 1982 to 1995, including F108 turbofans .

"Vomit Comet"

KC-135A with winglets (1979)

The US Air Force used a total of four KC-135A from 1960 together with NASA for parabolic flights for astronaut training and for experiments in weightlessness. The machines were given a padded main deck, the auxiliary power unit installed there and the rear tank as well as the tank boom were removed, and the electrics and hydraulics were adapted to the new operating conditions. The aircraft converted in this way were known as Weightless Wonder (German: weightless wonder) or Vomit Comet (German equivalent: Kotzbomber). Two of these KC-135s (55-3129 and 62-3536) and one C-135A operated the Air Force Systems Command from 1960 to 1973 from Wright-Patterson Air Force Base . In 1974 NASA took over the program management and initially used the 59-1481 as NASA 930 (registration number N930NA) from Ellington Air Force Base , which flew over 57,600 parabolas by the end of its mission in December 1995. From May 1995 on, the 63-7998 followed as NASA 931 (N931NA), which was decommissioned in October 2004 after 13,605 flight hours and 34,757 parabolas. The NASA 931 was also used for pilot training for the budding astronauts and accompanied the shuttle missions as a transport aircraft.

After being used as a weightless wonder , NASA's Dryden Flight Research Center tested the use of winglets on the 55-3129 . In July 1979 this machine received 2.7 m high winglets at the wing tips and made 39 flights by January 1981. They provided important information about the flow behavior and possible fuel savings, but were never used in series with the KC-135.

The US Federal Civil Aviation Administration (FAA) used two KC-135A from 1960 to 1975. The two aircraft (59-1481 and 59-1518) with the civilian registration numbers N98 and N96 checked existing and planned flight routes and navigation systems.

KC-135B

origin

After US President John F. Kennedy took office in 1961, the United States changed its military strategy, which had been coordinated with NATO , from massive retaliation to flexible response . Until then, it was a matter of starting an all-encompassing atomic counter-attack as automatically as possible after an enemy attack, now a series of metered and controlled counter-attacks should be possible. For this, however, it was necessary that the command structures of the Strategic Air Command (SAC) - and beyond that up to the President as commander in chief - still functioned after the destruction of the SAC command centers on the ground. The Air Force therefore decided to use airborne command posts (Airborne Command Post, ACP) . For this purpose she had already successfully tested five converted KC-135A in the mid to late 1960s. The machines received a refueling system in order to be able to extend the service life. A compartment with communication devices and a table for meetings was created on the main deck, and additional antennas were installed on the outside. The SAC also referred to the overall system as the Post Attack Command and Control System (PACCS) .

Looking Glass

An EC-135C (62-3585) from the 7th ACCS, Offutt Air Force Base, with MILSTAR equipment

In early 1961, the SAC's flying command centers began regular operations under the name Looking Glass . By the end of 1962 the fleet had grown to 16 units. At the same time, the USAF ordered 17 new aircraft for this purpose, which Boeing built from 1963 as the KC-135B and delivered from February 1964 to February 1965. These second-generation command posts were compared with the older version more powerful turbofan engines of the type Pratt & Whitney TF33-P-9 , additional wire antennas for long wave radio and modernized communication technology. They too could be refueled in the air.

Because of their special role and to be able to distinguish them from the other tankers, the ACPs of the KC-135B series received the new designation EC-135C on January 1, 1965 . After the commissioning of the newer version, the command posts of the first generation now served under the code EC-135A as reserve machines and, among other things, as a flying relay station for military radio communications. The tank system including the telescopic boom was retained in all of these machines and was used regularly for training or for emergencies. In early 1990, the Air Force equipped four EC-135Cs with a system for satellite communication through the Pacer Link program , externally recognizable by a hump on the fuselage, under which the antenna for the MILSTAR radio was hidden.

The Looking Glass missions consisted of eight-hour shifts. If the replacement could not take place due to bad weather or technical problems, the use of an ACP was extended by a further eight hours. If necessary, refueling was carried out in the air. In addition to the actual aircraft crew (pilot, copilot, navigator, boom operator), the crew consisted of a further 10 to 14 members, including an SAC commander (often a general , but at least one colonel ), deputy chief of operations, specialists in intelligence , data processing and weather as well several radio technicians. The USAF initially stationed the EC-135 at Andrews Air Force Base ( Maryland ), Barksdale AFB ( Louisiana ), March AFB ( California ), Offutt AFB ( Nebraska ) and Westover AFB ( Massachusetts ). They were initially assigned to existing tanker and reconnaissance units, but on April 1, 1970, the Strategic Air Command founded independent squadrons for the PACCS aircraft, the Airborne Command and Control Squadrons (ACCS), and distributed them to various other bases in the USA.

From February 3, 1961 to July 24, 1990 such a Looking Glass machine was constantly in the air. Only twice, in 1963 and 1972, was the mission interrupted for a maximum of 20 minutes, each time a sick crew member had to be dropped off. At least in the two years up to the dissolution of the Strategic Air Command on June 1, 1992, only one operation per day started. The Luftwaffe decommissioned four EC-135Cs in 1992 and 1993 and stored them in the 309th Aerospace Maintenance and Regeneration Group (AMARG) . Around half a dozen remained in service with the 7th ACCS of the Air Combat Command in Offutt in support of the United States Strategic Command until the end of the 1990s . From October 1, 1998, the US Navy's Boeing E-6 TACAMO took over the Looking Glass missions. The MILSTAR equipment was removed from the EC-135C and installed in the E-6A, which was then named E-6B.

Further use

Interior of an EC-135 as an Airborne Launch Control Center

The EC-135C were equipped to take the President, his Deputy and the Secretary of Defense ( National Command Authority ) on board in an emergency . She served as National Emergency Airborne Command Post (NEACP) , so as the command center in case of emergency (state of emergency) . For this purpose, the machines had additional radio devices for specially protected, encrypted communication with other command points. From 1965 to 1967, three C models under the Night Watch III program were initially equipped with more modern electronics and a more spacious compartment for the commanders-in-chief and were then given the designation EC-135J . The Air Force stationed them at their headquarters at Andrews Air Force Base near the government seat of Washington DC One of them was constantly on alert for night watch operations . From 1974 the Boeing E-4 took over the NEACP role from the EC-135J. The SAC then passed them on to Joint Base Pearl Harbor-Hickam in Hawaii , where they served the commander of the Pacific Air Forces under the name Blue Eagle as a flying command center until 1993, replacing older EC-135Ps. In February 1980 a fourth EC-135J was added, which had previously served as the EC-135C in Hickam for two years as a training aircraft for Blue Eagle .

Another special feature of EC-135C - and some EC-135A and EC-135G - was the possibility of board of remotely launches of intercontinental ballistic missiles trigger if the start centers had been devastated about by an opponent's attack. These Airborne Launch Control Centers (ALCC) were officially operational on May 31, 1967. During the Cold War , in the event of a crisis, two to three ALCCs would have circled over the US missile silo fields, waiting for orders to start the Minuteman or Peacekeeper .

The Air Force converted a former KC-135B and later EC-135C (USAF serial number 63-8050) into a test aircraft for laser weapon systems for the Air Force Materiel Command . From 1993 she was stationed at Edwards Air Force Base . In October 1996 it was named NKC-135B and was later also called Big Crow II . The USAF has been calling it NC-135E since early 2006 . Since then, her front hull has been painted completely black on the port side, with a white missile painted on it. Strong light and heat sources are installed at the stern of this "rocket", which simulate the hot recoil jet of a rocket. The aiming device of the prototype Boeing YAL-1A Airborne Laser is to be tested from Kirtland Air Force Base .

An EC-135C (62-3582) was renamed WC-135C after 1998 and is used to measure meteorological and atmospheric data.

KC-135D

In 1962, the Luftwaffe ordered nine RC-135A for photogrammetric tasks to replace the older RB-50s . By 1964, the program shrank to four machines that Boeing delivered at the end of 1965 (USAF serial numbers 63-8058 to -8061). It was the last four of the entire C-135 series. In the spring of 1970, they helped to determine the then controversial border between Argentina and Chile . Overall, however, the system suffered from technical problems and never reached full operational readiness. In addition, because of its involvement in the Vietnam War , the USAF wanted to spend less and less money on such projects with no direct military benefit. Therefore, the survey missions of the RC-135A ended in 1971 and from then on they served as transport aircraft for the Strategic Air Command .

The Luftwaffe had them converted into tanker aircraft in 1979. Although the RC-135A were outwardly identical to the KC-135A except for the tank boom, there were still more than 70 major technical differences. For example, the RC-135A had a second electric drive for the landing flaps instead of a mechanical one and a differently designed air conditioning system to cool the photo equipment. As a result, the four converted aircraft were given the designation KC-135D . In the next few years, the 305th Air Refueling Squadron used them as tankers from Grissom Air Force Base until they received new turbofan engines of the type TF33-PW-102 instead of the J57 turbojets in 1990. Then they served the Air National Guard first in Alaska and after 1995 with the 117th Air Refueling Squadron of the 190th Air Refueling Wing at Forbes Field in Kansas . In March and April 2007, the KC-135D were flown to AMARG and decommissioned.

KC-135E

A KC-135E refuels an F-16 Fighting Falcon

From 1975 the US Air Force gave the oldest KC-135A to the reserve units of the Air Force Reserve Command and the Air National Guard . In order to improve the performance of the around 130 aircraft and to reduce environmental pollution, they were equipped with new engines from 1981. Boeing received an order in September 1981 to overhaul used Pratt & Whitney JT3D engines from surplus civilian B707 and to replace them with the J57 of the KC-135A. Compared to the old turbojets , the JT3D-3B turbofans (military designation TF33-PW-102) with 80.1 kN offered 30% more thrust, 12% lower fuel consumption, 60% less noise and 90% less exhaust. With the TF33, the water injection responsible for the highest emissions was eliminated . Boeing also took over some cockpit instruments, the horizontal stabilizer and yaw dampers from the decommissioned B707 ; an anti-lock braking system improved the braking system.

The converted machines were given the designation KC-135E . Thanks to the increased propulsion power and lower consumption, it was able to deliver around 20% more fuel to receiving aircraft than its predecessor. The take-off taxi route was shortened by around 500 meters. Due to the civilian origin of their engines, only the D and E models have thrust reversers . Boeing handed the first E-model over to the Air Force on January 26, 1982, and by 1991 around 150 A-variant tankers and some special versions (EC-135H, NKC-135A) had been modernized in this way. From 1996 the USAF had around 20 KC-135Es upgraded to KC-135R.

At the end of March 2008, 67 KC-135E were still in service with the Reserve Forces, of which only 15 are actually in use. 25 machines are kept ready to fly but not used, which costs 121,400 dollars per aircraft per year. Some of the remaining 27 have been banned from flying for years because they were found to have been damaged by corrosion in the area of ​​the engine mountings. In the 2008 budget year, the Air Force may decommission a maximum of 48 KC-135Es (based on a fleet of 85 aircraft in autumn 2007). The remaining 37 aircraft may only be taken out of service once the development contract for the successor KC-X has been finally awarded. With an age of up to 50 years, these E-models are the oldest still active aircraft in the US Air Force.

KC-135Q and -T

A KC-135Q refuels an SR-71 Blackbird

At the end of the 1950s, Lockheed developed the A-12 Oxcart reconnaissance aircraft for the US secret service CIA , from which the YF-12 and finally the SR-71 Blackbird for the Air Force emerged a few years later . The high flight speed of up to Mach 3.3 and the associated frictional heat required a special thermally stable fuel . Because of the limited internal fuel capacity of the A-12 and its successors, they had to be able to be refueled for their missions in the air. For this purpose, the CIA financed the conversion of almost 20 KC-135A from 1961. In June 1966 at the latest, they were given the out-of-order designation KC-135Q , and the logical version would have been C.

The fuselage tanks in the lower deck and on the main deck were used to accommodate the special fuel PF-1, while the standard fuel JP-4 was housed in the wing tanks for the KC-135's own supply. In order to be able to transport the PF-1 despite its caustic effect, the fuel lines and tanks were provided with ceramic coatings. When the Air Force replaced the PF-1 with the less aggressive JP-7 in the early 1970s, the traditional fuel system was reinstalled. The KC-135Q carried up to 33.8 tons of specialty fuel and 49.9 tons of JP-4. It was also possible, after flushing the JP-7 fuel system in all tanks, to transport and transfer JP-4. So the Q version was not limited to air refueling of the A-12 or SR-71, but also served other types of aircraft.

Other changes concerned the avionics . An additional, third UHF radio (AN / ARC-50) with a distance measuring device helped to locate an SR-71 over several hundred kilometers. Conversely, a tracking transmitter ( TACAN , AN / ARN-90) on board the KC-135Q supplied the crew of the SR-71 with data to safely hit the tanker. There were also devices for precise navigation away from directional radio beacons ( LORAN ) as well as flashing lights and spotlights for orientation during the rendezvous. A wired voice connection via the tank boom enabled communication between the aircraft crews even when the radio was silent during the secret reconnaissance missions.

By the end of 1966, 21 KC-135Q were available, in 1967 the Luftwaffe converted another 35 A-models, making a total of 56 KC-135Q. However, only 21 of them received the complete avionics equipment, 35 were only equipped with the AN / ARC-50 and should only carry the other devices with them when required.

The use of the KC-135Q began immediately after the first flight of the A-12 in April 1962, the first refueling attempts were still made with ordinary JP-4. After the introduction of the SR-71 in 1966, the Q models were stationed with her at Beale Air Force Base in California and were part of the Strategic Air Command's 903rd aerial refueling squadron . To support the reconnaissance missions, the KC-135Q were relocated together with the A-12 and SR-71, including from 1967 to Kadena Air Base ( Japan ) or to RAF Mildenhall ( Great Britain ). Since 1981 the KC-135Q has been relieved by the KC-10 extenders , which can also refuel the Blackbird. After the USAF had decommissioned the SR-71 in early 1990, the Q version served as a normal tanker or transported special fuel for the U-2 Dragon Lady to their locations.

Two KC-135Qs were lost in accidents: on June 3, 1971, the machine with the serial number 58-0039 crashed while approaching Torrejon Air Base in Spain, killing all five crew members. The 60-0338 caught fire on February 8, 1980 while refueling at Plattsburgh Air Force Base , New York , and was badly damaged. The fuselage then served as a test object for antenna assemblies.

Between mid-1993 and the end of 1995, the Air Force had all 54 remaining KC-135Qs equipped with new F108 engines , bringing them up to the technical standard of the R version. They were then given the designation KC-135T .

A single Stratotanker had the designation KC-135T earlier. The machine with the serial number 55-3121 was created in December 1969 from a KC-135R (old) and was used for electronic reconnaissance . At the end of 1970 the Luftwaffe had it converted for telecommunications reconnaissance missions and from May 1971 carried it as the RC-135T.

KC-135R

A KC-135A refuels the prototype of the KC-135R (61-0293)

A KC-135R Stratotanker the US Air Force refuels an F-22 Raptor

KC-135R with external refueling canisters supplies British tornadoes

In the mid-1970s, the US Air Force was planning to modernize its tanker fleet. The Ministry of Defense had started a program for a new combined tanker and transport aircraft (Advanced Tanker / Cargo Aircraft, ATCA) , which eventually became the KC-10 Extender in 1980. After the end of the operations in the Vietnam War , the Strategic Air Command (SAC) delivered around 130 KC-135s to the reserve forces. The remaining tankers should be upgraded in order to be able to use them more efficiently. Starting in 1977, five proposals made it onto the shortlist. At 10.6 million US dollars per aircraft, the most expensive and complex involved replacing the J57 turbojet engines with modern turbofans and installing newly designed wings with a supercritical profile . According to the cheapest - and most unusual - design, the KC-135 were to receive a mixed engine, in which only the two inner engines would be replaced.

In 1979, Boeing equipped its last B707, built for civilian purposes, with CFM56-2 turbofan engines, and in 1980 took this B707-700 on an advertising tour of 15 air force bases in order to introduce the new engine to as many pilots and officers as possible. In the end, the Luftwaffe decided on exactly this type of engine, but against new wings. However, between 1975 and 1988, she had the planking of the underside of the wing of all KC-135s renewed in order to increase their service life. In 1981 Boeing received the order to upgrade the SAC's 400 KC-135s. In addition to the CFM56 engines (military designation: F108-CF-100), this included two auxiliary engines instead of one, a reinforced landing gear, a horizontal stabilizer that was enlarged from 46.5 to 50.6 square meters and over 20 other technical changes.

The modernized tanker version received the designation KC-135R . The first copy left on June 22, 1982 Boeing workshops in Wichita ( Kansas ) and first flew on 4 August of the same year. The prototype was the 61-0293, a former flying command post (EC-135A) of the SAC, which could be refueled in the air since the early 1960s. The flight tests of the R model benefited from this, as it made it easier to determine the performance at different flight weights. In fact, the flight performance improved enormously with the new drive: In a typical mission profile (take-off, 3700 km flight to the rendezvous, 3700 km return flight to the base), a KC-135R can transfer a maximum of 31.8 tons of fuel, a KC-135A only 18, 1 t. The thrust increased by around 70% to 98.5 kN, consumption fell by 25% and noise emissions by 96%. The lower maintenance and operating costs are also a decisive plus. Basically, two R models perform the same as three A models. In long-distance operations, the performance of the KC-135R even exceeds that of the KC-10, as it requires a relatively large amount of fuel for its own consumption despite its high weight.

By June 2005, Boeing had upgraded 345 A-models and 20 E-models of the USAF to R-versions, as well as around 25 export models for France (C-135FR, see below), Singapore and Turkey. Eight US Air Force KC-135R can be refueled in the air because they were previously used for special tasks, such as SAC mobile command stations or reconnaissance. You have been part of the 22nd Air Refueling Squadron at McConnell Air Force Base since 1994 . Twenty machines have brackets for external Mk 32B refueling containers on the underside of the wing tips, which can be used to refuel two aircraft of the US Navy and other NATO countries at the same time using a hose and collecting funnel (Multipoint Refueling System, MPRS) .

KC-135R was also the name of an early reconnaissance version of the KC-135A. The four machines (55-3121, 58-0126, 59-1465 and 59-1514) were given this name on June 1, 1967, were based at Offutt Air Force Base ( Nebraska ) and took part in special missions worldwide. By 1976 they had either been converted into other variants or crashed (59-1465, July 17, 1967 in Offutt), so that the designation could be used again for the newly motorized tankers from 1981.

C-135F - tanker for France

background

Active KC-135

Until the mid-1990s, France remained the only country to which the US exported the KC-135, although inquiries from Iran , Israel and Canada had also been received . The delivery of twelve newly built tanker aircraft in 1964 was controversial in the US government, because France wanted to use it to make its Nuclear Dissuasion Force even more powerful and independent.

Originally, in the mid-1950s , the French Air Force planned to build a supersonic strategic bomber to attack targets in the Soviet Union , but it was never realized for cost reasons. Instead, the existing Dassault Mirage IV bomber received from 1962, among other modernizations, an air refueling facility to increase its range. This new Mirage IVA could now fly 5510 kilometers with air refueling instead of 2870 km without refueling. In order to be able to quickly supply the bomber fleet with fuel in an emergency, only a tanker with jet propulsion was possible. A Transall variant that was considered briefly turned out to be too slow.

negotiations

France began negotiations with the United States in 1960 to purchase ten Stratotankers. A tanker should be able to operate four Mirages, so that the Armée de l'air calculated with a planned bomber fleet of 36 machines with nine KC-135 plus a reserve machine. Without tankers, the bombers would be ineffective as they would not reach the distant destinations in the east. The talks were initially unsuccessful, because the US did not want to promote France's military independence under any circumstances. Some US generals endorsed the delivery, but President John F. Kennedy publicly stated on June 7, 1962 that support for the French nuclear weapons program was not an issue. On the same day, however, US Secretary of Defense Roswell Gilpatric approved the sale of twelve KC-135s valued at $ 50 million to France. Nine days after this deal, Defense Minister Robert McNamara railed against the French strategy of deterrence, describing it as inadequate, implausible and dangerous. Another month later, he announced the treaty, which reflected the improved relations between the two states.

Production and delivery

Boeing produced the tankers in two blocks of six machines each under the internal model number 717-165. Since France wanted to use them both as a tanker and as a transport aircraft , they were given the designation C-135F . They have license plates based on the US Air Force (63-8470 to 8475 and 63-12735 to 12740) and the last two letters of a pseudo-national license plate that serve as a call sign (F-UKCA to -UKCL).

France originally wanted turbofan engines as the engine, but ultimately opted for the usual Pratt & Whitney J57 turbo jets because of the lower acquisition costs . In contrast to the US Air Force's Stratotankers, the C-135F were fitted with a hose on the tank boom as standard, as the French Air Force only used the hose-probe system for air refueling until 1990 .

The rollout of the first C-135F took place on November 5, 1963 in Renton , Washington , the first flight on November 26. The United States delivered the first tanker to France on February 3, 1964, the twelfth and last on October 10, 1964.

On August 1, 1963, the Armée de l'air set up its first unit for aerial refueling, the 90th Escadron de Ravitaillement en Vol (ERV, German: Luftbetankungsstaffel) at air force base 125 in Istres . The 90th ERV received its first Ravitailleur (French for tanker) on February 3, 1964 . The twelve C-135F were distributed over three bases, in addition to Istres, Mont-de-Marsan and Avord . Since July 1976 the tankers have been part of the 93rd ERV.

Modernizations

Boeing renewed the outer skin on the underside of the wings in 1977 in order to increase the service life of the aircraft. In 1980, France decided that tankers with new turbofan engines type CFM56 equip -2B1. The first modernized machine (63-12736) flew for the first time on August 3, 1985, by 1988 the conversion was completed. The newly motorized tanker aircraft were given the designation C-135FR .

From 1993, the machines were equipped with refueling containers at the wing ends, so that two receivers can now be operated at the same time. The rigid boom at the stern now has a higher throughput without a hose adapter, which improves the supply of the French AWACS reconnaissance aircraft E-3F . However, this option has not been used in practice for a long time. Since the operation was not trained either, Allied combat aircraft equipped with this system, such as the F-16 , could not be supplied by French tankers during the international military operation in Libya in 2011 .

To meet the increased need for air refueling capacity, France leased three KC-135Rs from the US Air Force from late 1992 to 1997. From mid-1997, the Armée de l'air took over five KC-135Rs to compensate, which had previously been temporarily stored at AMARG as KC-135A and received new CFM56 engines before delivery in order to bring them up to the status of the R version.

commitment

Cold War

The regular missions of the KC-135 began at the end of 1957. Among other things, they supplied the airborne command post of the Strategic Air Command over the territory of the USA and refueled the B-52 Stratofortress, which was constantly carrying nuclear weapons in the 1960s in the Operation Chrome Dome Patrolled near the Soviet Union . During the Cold War, part of the tanker fleet was on constant alert on the ground in order to support the SAC's strategic bombers in a first or second strike in an emergency . In addition, there were the special missions of the KC-135Q to refuel the high-altitude reconnaissance aircraft SR-71 Blackbird. After the end of the Cold War and the dissolution of the SAC in June 1992, the Air Mobility Command of the US Air Force took over the tanker fleet.

Combat missions

On June 9, 1964, the KC-135 was used for the first time in combat operations, when it refueled over Vietnam F-100 Super Saber fighter jets , which then attacked targets in Laos . The missions in Southeast Asia began in October 1961 with the support of reconnaissance flights, and from mid-1962 to the end of 1963 200 KC-135 accompanied a total of 29 transfers of fighter jets to the crisis region. During the Vietnam War , up to 172 KC-135s were on site, mainly at Kadena Air Base ( Japan ), U-Tapao Air Base ( Thailand ), Andersen Air Force Base ( Guam ) and Clark Air Base ( Philippines ). During the war, the Stratotankers flew a total of 194,687 sorties, carried out 813,878 refueling operations and delivered around 4.07 million tons of fuel.

In the Second Gulf War , the tankers were deployed 13,168 times during the first 22-week Desert Shield phase from August 1990 and refueled 28,857 receivers with 160,425 tons of fuel. In the subsequent six weeks of Desert Storm , 262 KC-135s completed 13,587 sorties and 40,781 refueling with 234,562 tons of fuel. During this Gulf War, the Air Force first used the more modern KC-135R in combat, which did the job of two KC-135A or -Q in often hot and humid weather. In the Kosovo War ( Operation Allied Force ) in 1999 151 KC-135 took part. During the invasion phase of the Iraq war (Operation Iraqi Freedom) from March to May 2003, 149 KC-135 and 33 KC-10 of the USAF flew over 6,000 sorties and transferred more than 136,000 t of fuel.

From 1966 the French C-135F flew regular tank missions for the alert Mirage bombers, of which twelve were constantly in the air until 1967. The Ravitailleurs' first combat mission took place in 1977, when the French Air Force was fighting Polisario rebels in Mauritania (Operation Lamantin). This was followed by missions in Chad in 1983 and 1986 (operations Manta and Épervier). The French tanker aircraft have been supporting the coalition forces in the Gulf Wars since 1990 .

Although the KC-135 is also a transport aircraft, it was rarely used in this role. On the one hand, there were pure freighter variants with the C-135A and -B, on the other hand, from 1965 the Air Force had more suitable transporters with more accessible and larger ones with the C-141 Starlifter and later with the C-5 Galaxy and C-17 Globemaster III Hold. In 2006, the more than 200 KC-135s of the Air Mobility Command carried only around 284 tons of cargo compared to 1,732 tons of the 59 KC-10 and 228,875 tons of the 150 C-17.

Incidents

A total of 76 Boeing C-135 family aircraft were lost in crashes or accidents.

Aircraft type	Number of accidents	Death toll
KC-135A	56	350
KC-135E	2	6th
KC-135P	1	5
KC-135R	2	6th
KC-135Q	2	5
C-135A	1	84
C-135B	2	87
C-135F	1	4th
EC-135C	1	0
EC-135J	1	0
EC-135K	1	20th
EC-135N	1	21st
EC-135P	1	0
RC-135E	1	19th
RC-135S	1	0
RC-135T	1	3
VC-135A	1	0

As of January 1, 2010

In the early years, several KC-135A crashed during the critical launch phase. If an engine failed or the water injection failed , the engine could often no longer be intercepted. The other losses were mostly due to technical defects, maintenance errors or bad weather in connection with pilot errors. No Stratotanker was lost through direct enemy action.

Only four Stratotankers had an accident during the actual in-flight refueling. The most momentous incident of this type occurred on January 17, 1966 over the Spanish Mediterranean coast. During a Chrome Dome mission, a KC-135A collided with a B-52G, whereupon both aircraft crashed near Palomares and seven of the eleven occupants died. Two of the four hydrogen bombs on the B-52 were damaged and contaminated the ground. Another bomb could not be recovered from the Mediterranean until April 1966.

A Washington Air National Guard KC-135E crashed on January 13, 1999 while attempting to take off at the German NATO airfield in Geilenkirchen . The cause of the accident, in which all four crew members perished, was an incorrect position of the trim tab of the horizontal stabilizer . However, it could not be clear whether this was due to a technical error or incorrect operation.

The C-135F that crashed was the 63-8473 / F-UKCD. It crashed on July 1, 1972 immediately after taking off on a weather reconnaissance flight from the Hoa base ( Tuamotu Archipelago , French Polynesia ). An engine of the fully loaded machine was destroyed during take-off because the injection water was contaminated. All six crew members were killed in the accident.

Present and Future

Of the total of 732 Stratotankers built for the US Air Force, it was still operating around 490 at the end of March 2008. Based on the various variants, 67 were KC-135E, 365 are R and 54 T models. Of these, around 200 belonged to the active air force, most of them to the Air Mobility Command , but the Pacific Air Forces and the United States Air Forces in Europe also maintain their own squadrons. The Air National Guard decreed in 2007 over 24 seasons with 250 Stratotanker tankers and represented 45% of the total tanker fleet. 84 KC-135 were assigned to the Air Force Reserve Command . Some machines are also used for test purposes at the Air Force Materiel Command .

In February 2011, the US Air Force selected the Boeing KC-46 as the successor to the KC-135.

User states

 United States

397 Total in active service

United States Air Force ( Air Mobility Command / USAFE / Pacific Air Forces )

• 171 × KC-135R / T
• 4 × GKC-135E as flightless training machine for mechanics

Air National Guard

• 163 × KC-135R

Air Force Reserve Command

• 63 × KC-135R

 France

Armée de l'air (French Air Force)

• 14 × KC-135FR / R

 Turkey

Turkish Air Force (Turk Hava Kuvvetleri)

• 7 × KC-135R

 Singapore

Singapore Air Force

• 4 × KC-135R

Technical specifications

Parameter	KC-135A	KC-135E	KC-135R
Operator:	United States		Singapore, Turkey, USA, France
Commissioning:	June 1957	January 1982	July 1984 (USA)
Length:	41.5 m
Span:	39.9 m
Height:	11.7 m (from 1962: 12.7 m)	12.7 m
Wing area:	226 m²
Drive:	four Pratt & Whitney J57-P-59W with 50 kN thrust each	four Pratt & Whitney TF33-PW-102 with 80 kN thrust each	four CFM International F108-CF-100 with 99 kN thrust each
Top speed:	980 km / h
Marching speed:	850 km / h
Range:	10,000 km	12,000 km	17,700 km
Service ceiling:	15,200 m
Empty weight:	44.6 t	approx. 50 t	54.1 t
Maximum payload:	37.6 tons of freight or 80 passengers or 85 tons of fuel		37.6 tons of freight or 37 passengers or 92 tons of fuel
Maximum take-off weight:	132.4 t	134.7 t	146.3 t
Take-off run: (at max. Take-off weight)	3,400 m	2,900 m	2,500 m
Crew:	4 (pilot, co-pilot, navigator, boom operator)		3 (pilot, co-pilot, boom operator)

literature

• Robert S. Hopkins: Boeing KC-135 Stratotanker. More than just a tanker. Earl Shilton (UK), 1997. ISBN 1-85780-069-9 .
• Mark Ayton: 135 The World's Greatest Tanker… and more. Key Publishing Ltd, 2014.

Web links

Commons : KC-135 Stratotanker  - Album with pictures, videos and audio files

• The KC-135 on the Boeing website. Accessed December 1, 2019 . 
• Factsheet on the United States Air Force website. May 14, 2018, accessed December 1, 2019 . 

Individual evidence

1. ↑ Jane's all the world's aircraft 1956–1957.
2. ↑ Aerospaceweb.org | Aircraft Museum - C-135 Stratolifter / KC-135 Stratotanker
3. ↑ Boeing delivers final re-engineered KC-135. boeing.com, July 2005
4. ↑ NASA Johnson Space Center: The History of KC-135A. ( Memento of the original from July 1, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. NASA 931 of the Reduced Gravity Research Program (April 11, 2007).  
5. ↑ Statement (PDF) ( memento of April 8, 2008 in the Internet Archive ) by USAF General Arthur J. Lichte, Commander of the Air Mobility Command, before the Armed Forces Committee of the US House of Representatives, April 1, 2008, p. 9f.
6. ^ National Defense Authorization Act for Fiscal Year 2008, Section 135.
7. ↑ Richard L. Olsen et al. a .: Gulf War Air Power Survey . Washington, DC, 1993. Volume III, Part I Logistics , pp. 180f.
8. ↑ Christopher Bolkcom: Air Force Aerial Refueling. Congressional Research Service (Ed.) Report RS20941 (PDF; 46 kB) . Washington, DC, September 19, 2005
9. ^ Air Force Magazine, Daily Report, Jan. 11, 2007 overview
10. ↑ Aircraft accident data and report in the Aviation Safety Network (English)
11. ↑ Air Force unable to deterministic mine cause of crash. (No longer available online.) In: kitsapsun.com. June 6, 1999, archived from the original on January 12, 2014 ; accessed on January 12, 2014 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  
12. ↑ Airman Magazine, The Book 2007. ( Memento of March 16, 2007 in the Internet Archive )
13. ^ E. Stan Wilson (Ed.): National Guard and Reserve Equipment Report for Fiscal Year 2007. Washington, DC, Feb. 2006, Chapter 5

This article was added to the list of excellent articles on May 4, 2007 in this version .