The legendary tanker that refuels planes in flight
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.
A Cold War-era image of B-52D refueling from a KC-135A.
(U.S. Air Force photo)
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.
Development and design
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.
Airmen of the 86th Aeromedical Evacuation Squadron perform lifesaving procedures to a patient in a KC-135 Stratotanker, at Ramstein Air Base, Germany, March 26, 2015. Aircrew and a KC-135 from Royal Air Force Mildenhall, England, spent multiple days at Ramstein performing aerial refueling missions, which also gave AES Airmen the opportunity to train on their mission inside a different airframe.
(Photo by Damon Kasberg)
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.
An A-10C Thunderbolt II receives fuel from a KC-135 Stratotanker over Afghanistan Oct. 2, 2013. The A-10 is deployed from Moody Air Force Base, Ga., to the 74th Expeditionary Fighter Squadron in support of Operation Enduring Freedom. The KC-135 is assigned to the 340th Expeditionary Air Refueling Squadron.
(Photo by Stephany Richards)
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.
A KC-135 Stratotanker flies through storm clouds on its way to refuel a C-17 Globemaster III off Florida's east coast, July 12, 2012. The KC-135 was the Air Force's first jet-powered refueling tanker and replaced the KC-97L Stratofreighter.
(Photo by Jeremy Lock)
Operation and deployment
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.
Did you know?
- The Stratotanker is constructed with almost 500,000 rivets. The installed cost of these rivets range from 14 cents to id="listicle-2595814234".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.
A U.S. Air Force B-52 Stratofortress leads a formation of aircraft including two Polish air force F-16 Fighting Falcons, four U.S. Air Force F-16 Fighting Falcons, two German Eurofighter Typhoons and four Swedish Gripens over the Baltic Sea, June 9, 2016. The formation was captured from a KC-135 from the 434th Air Refueling Wing, Grissom Air Force Base, Indiana as part of exercise BALTOPS 2016.
(Photo by Erin Babis)
KC-135 Stratotanker fact sheet:
- 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: .6 million
This article originally appeared on Airman Magazine. Follow @AirmanMagazine on Twitter.