By Bennie J. Davis III, Airman Magazine
/ Published August 13, 2018
The KC-135 Stratotanker provides the core aerial refueling capability for the United States Air Force and has excelled in this role for more than 60 years. This unique asset enhances the Air Force's capability to accomplish its primary mission of global reach. It also provides aerial refueling support to Air Force, Navy, Marine Corps and allied nation aircraft. The KC-135 is also capable of transporting litter and ambulatory patients using patient support pallets during aeromedical evacuations.
A KC-135 Stratotanker refuels an SR-71. The SR-71 was capable of flying 3,200 statute miles before needing to refuel. (U.S. Air Force photo)
(U.S. Air Force photo/Tech. Sgt. James L. Harper Jr.)
KC-135 STRATOTANKER (U.S. Air Force photo)
C-17 Globemaster III
(U.S. Air Force photo/Master Sgt. Jeremy Lock)
A KC-135R Stratotanker assigned to the 6th Air Refueling Wing, 91st Air Refueling Squadron, at MacDill Air Force Base, Fla., flies a training mission over central Florida. The KC-135's principal mission is air refueling while four turbofans, mounted under 35-degree swept wings, power the KC-135 to takeoffs at gross weights up to 322,500 pounds. (U.S. Air Force photo by Master Sgt Keith Reed)
A 401st Tactical Fighter Wing F-16C Fighting Falcon aircraft refuels from a KC-135 Stratotanker aircraft as another F-16 stands by during Operation Desert Storm. (U.S. Air Force photo)
A 927th Air Refueling Wing KC-135 Stratotanker soars overhead after refueling a C-17 Globemaster III July 1, 2014. The C-17 relies on aerial refueling to complete long-distance missions into and out of the theater of operations. (U.S. Air Force photo/Airman 1st Class Clayton Cupit)
While it may sound cliché, it’s a common motto within the tanker community. For more than 60 years of continuous service, the KC-135 Stratotanker has been the core aerial refueling capability for U.S. operations around the world.
The KC-135 provides the Air Force with its primary mission of global reach, but it also supports the Navy, Marine Corps and allied nations in assisting training, combat and humanitarian engagements.
The aircraft is also capable of transporting litters and ambulatory patients using patient support pallets during aeromedical evacuations.
The stratotanker was the Air Force’s first jet-powered refueling tanker, replacing the KC-97 Stratofreighter. It was originally designed and tasked to support strategic bombers, but has been heavily used in all major conflicts since its development, extending the range and endurance of U.S. tactical fighters and bombers.
The KC-135 is a mid-air refueling aircraft with a telescoping “flying boom” tube located on the rear of the plane. A boom operator lays prone and guides the boom insert into a receptacle on the receiving aircraft. With a single boom, aircraft refuel one at a time.
The mid-air refueling capability changed the landscape of air dominance during the Vietnam War and enabled tactical fighter-bombers of the Air Force, Navy and Marine Corps to stay on the front lines for hours rather than minutes due to their limited fuel reserves and high fuel consumption.
For bombers, all targets were now within reach without the need of hopping from base to base until striking their targets. No longer are lives at stake to build airstrips to support bombing campaigns, as they were in WWII.
The Boeing Company’s model 367-80 jet transport, commonly called the “Dash-80,” was the basic design for the commercial 707 passenger plane as well as the KC-135A Stratotanker.
In 1954, the Air Force purchased the first 29 of its future 803 aerial refueling tanker fleet. 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.
The aircraft’s KC identifier stands for (K) tanker (C) transport.
The aircraft is powered by four turbofan engines mounted on 35-degree swept wings, has a flight speed of more than 500 mph and a flight range of nearly 1,500 miles when loaded with 150,000 lbs. of fuel.
The KC-135 has been modified and retrofitted through the years with each update providing stronger engines, fuel management and avionics systems. The recent Block 45 update added a new glass cockpit digital display, radio altimeter, digital autopilot, digital flight director and computer updates.
Of the original KC-135As, more than 417 were modified with new CFM-56 engines.
The re-engined tanker, designated either the KC-135R or KC-135T, can offload 50 percent more fuel, is 25 percent more fuel efficient, costs 25 percent less to operate and is 96 percent quieter than the KC-135A.
In 1981 the KC-10 Extender was introduced to supplement the KC-135. The KC-10 doubles the fuel carrying capacity of the KC-135, which is critical in supporting mobility operations of large cargo aircraft like the C-5 Galaxy and the C-17 Globemaster III.
Through the years, the KC-135 has been altered to do other jobs ranging from flying command post missions to reconnaissance. RC-135s are used for special reconnaissance and Air Force Materiel Command’s NKC-135As are flown in test programs. Air Combat Command operates the OC-135 as an observation platform in compliance with the Open Skies Treaty.
The KC-135R and KC-135T aircraft continue to undergo life-cycle upgrades to expand their capabilities and improve reliability. Among these are improved communications, navigation and surveillance equipment to meet future civil air traffic control needs.
There have been 11 variants or models through the years of the C-135 family.
The aircraft carries a basic crew of three, a pilot, co-pilot and boom operator. Some missions require the addition of a navigator.
Nearly all internal fuel can be pumped through the flying boom. A special shuttlecock-shaped drogue attached to and trailing behind the flying boom may be used to refuel aircraft fitted with probes. Some aircraft have been configured with the multipoint refueling system, which consists of special pods mounted on the wingtips. These KC-135s are capable of refueling two receiver aircraft at the same time.
In 2007 the Air Force announced plans for the KC-X tanker replacement program for the KC-135. In 2011, the Boeing KC-46 Pegasus was selected as the winner of the program.
The first 18 combat-ready Pegasus tankers are expected for delivery by 2019.
The KC-135 E and R models are expected to continue service until 2040 when they will be nearly 80 years old.
Air Mobility Command manages the current inventory of 396 Stratotankers, of which the Air Force Reserve and Air National Guard fly 243 aircraft in support of AMC’s mission.
While AMC gained the control of the aerial refueling mission, a small number of KC-135s were also assigned directly to U.S. Air Forces in Europe, Pacific Air Forces and the Air Education and Training Command.
All Air Force Reserve Command KC-135s and most of the Air National Guard KC-135 fleet are operationally controlled by AMC, while Alaska Air National Guard and Hawaii Air National Guard KC-135s are operationally controlled by PACAF.
The Stratotanker is constructed with almost 500,000 rivets. The installed cost of these rivets range from 14 cents to $1.50 each.
The KC-135 as 23 windows, nearly all of which are heated electrically or with hot air to prevent fogging.
The tanker has a cargo area easily capable of holding a bowling alley, with enough room left over for a gallery of spectators. The cargo area is almost 11 feet wide, 86 feet long and 7 feet high: the equivalent of 220 automobile trunks.
The KC-135 transfers enough fuel through the refueling boom in one minute to operate the average family car for more than one year.
It can transfer more fuel in 8 minutes than a gas station could pump in 24 hours.
Primary function: Aerial refueling and airlift
Builder: The Boeing Company
Power plant: CFM International CFM-56 turbofan engines
Thrust: 21,634 pounds of thrust in each engine
Wingspan: 130 feet, 10 inches (39.88 meters)
Length: 136 feet, 3 inches (41.53 meters)
Height: 41 feet, 8 inches (12.7 meters)
Speed: 530 mph at 30,000 feet (9,144)
Range: 1,500 miles (2,419 kilometers) with 150,000 pounds (68, 039 kilograms) of transfer fuel; ferry mission, up to 11,015 miles (17,766 kilometers)
Ceiling: 50,000 feet (15,240 meters)
Maximum takeoff weight: 322,500 pounds (146, 285 kilograms)
Maximum Transfer Fuel Load: 200,000 pounds (90,719 kilograms)
Maximum Cargo Capability: 83,000 pounds (37,648 kilograms), 37 passengers
Crew: 3 (pilot, co-pilot and boom operator. Some KC-135 missions require the addition of a navigator. The Air Force has a limited number of navigator suites that can be installed for unique missions.)
Aeromedical Evacuation Crew: A basic crew of five (two flight nurses and three medical technicians) is added for aeromedical evacuation missions. Medical crew may be altered as required by the needs of patients.
Initial operating capability: 1956
Unit cost: $39.6 million
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