KC-135 Stratotanker

The Boeing KC-135 Stratotanker was the first jet powered aerial refueling tanker of the US Air Force, replacing the KC-97 Stratotanker. Similar in design to the later and enlarged Boeing 707 airliner, it was initially tasked to refuel strategic bombers, but was used extensively in the Vietnam war and later conflicts such as Desert Storm to extend the range and endurance of both Air Force and Navy tactical fighters and bombers.

Serving with the United States Air Force since 1957, it is one of just six military fixed wing aircraft with over 50 years of continuous service with the original service along with the Tupolev Tu-95, the C-130 Hercules, the B-52 Stratofortress, the English Electric Canberra and the Lockheed U-2. Supplemented by the larger KC-10, complete replacement is still under study by the Air Force. Despite increased maintenance costs, studies conclude many of the aircraft could be flown until 2040, with ages reaching 80 years before reaching lifetime flying hour limits.

The KC-135 is derived from the original Boeing jet transport "proof of concept" demonstrator, the Boeing 367-80 (commonly called the "Dash-80"). As such, it has a narrower fuselage and is shorter than the Boeing 707 jetliner. Boeing gave the tanker the designation of Model 717. The 367-80 was the basic design for the commercial Boeing 707 passenger aircraft as well as the KC-135A Stratotanker.

In 1954 the USAF's Strategic Air Command ordered the first 29 of its future fleet of 732. The first aircraft flew in August 1956 and the initial production Stratotanker was delivered to Castle Air Force Base, California, in June 1957. The last KC-135 was delivered to the Air Force in 1965.

Developed in the late 1950s, the basic airframe is characterized by swept wings and tail, four underwing mounted engine pods, a horizontal stabilizer mounted on the fuselage near the bottom of the vertical stabilizer with positivedihedral on the two horizontal planes and a hi-frequency radio antenna which protrudes forward from the top of the vertical fin or stabilizer. These basic features make it strongly resemble the commercial Boeing 707 and 720 aircraft, although it is actually a different aircraft.

The Strategic Air Command (SAC) had the KC-135 Stratotanker in service with Regular Air Force SAC units from 1957 through 1992 and with SAC-gained Air National Guard(ANG) and Air Force Reserve (AFRES) units from 1975 through 1992.

Following a major USAF reorganization that resulted in the inactivation of SAC in 1992, most KC-135s were re-assigned to the newly-created Air Mobility Command (AMC). While AMC gained the preponderance of the aerial refueling mission, a small number of KC-135s were also assigned to directly United States Air Forces in Europe(USAFE), Pacific Air Forces (PACAF) and the Air Education and Training Command (AETC). All Air Force Reserve Command (AFRC) KC-135s and most of the Air National Guard (ANG) KC-135 fleet became operationally-gained by AMC, while Alaska Air National Guard and Hawaii Air National Guard KC-135s became operationally-gained by PACAF.

Reconnaissance and command post variants of the aircraft, including the RC-135 Rivet Joint and EC-135 Looking Glass Post Attack Command & Control Systems were operated by SAC from 1963 through 1992, when they were re-assigned to the Air Combat Command (ACC). The USAF EC-135 Looking Glass was subsequently replaced in its role by the U.S. Navy E-6 Mercury aircraft, a new build airframe based on the Boeing 707 and KC-135.

The KC-135R has four turbofan engines, mounted under 35-degree swept wings, which power it to takeoffs at gross weights up to 322,500 pounds (146,300 kg). Nearly all internal fuel can be pumped through the tanker's flying boom, the KC-135's primary fuel transfer method. A special shuttlecock-shaped drogue, attached to and trailing behind the flying boom, may be used to refuel aircraft fitted with probes. A boom operator stationed in the rear of the aircraft controls the boom while lying prone. A cargo deck above the refueling system can hold a mixed load of passengers and cargo. Depending on fuel storage configuration, the KC-135 can carry up to 83,000 pounds (37,600 kg) of cargo.

Specifications (KC-135R)

General characteristics

• Crew: 3: pilot, co-pilot and boom operator. Some KC-135 missions require the addition of a navigator.
• Capacity: 37 passengers
• Payload: 83,000 lb (37,600 kg)
• Length: 136 ft 3 in (41.53 m)
• Wingspan: 130 ft 10 in (39.88 m)
• Height: 41 ft 8 in (12.70 m)
• Wing area: 2,433 ft² (226 m²)
• Empty weight: 98,466 lb (44,663 kg)
• Loaded weight: 297,000 lb (135,000 kg)
• Useful load: 200,000 lb (90,700 kg)
• Max takeoff weight: 322,500 lb (146,000 kg)
• Powerplant: 4× (R/T) CFM International CFM56 (F108-CF-100) turbofan, 21,634 lbf () each
• Maximum Fuel Load: 31,275 US gal (118 kL)

Performance

• Maximum speed: 580 mph (933 km/h)
• Cruise speed: 530 mph
• Range: 1,500 mi (2,419 km) with 150,000 lb (68,039 kg) of transfer fuel
• Ferry range: 11,015 mi (17,766 km)
• Service ceiling: 50,000 ft (15,200 m)
• Rate of climb: 4,900 ft/min (1,490 m/min)