Aircraft Factfile and Recognition Guide - KC-135 Stratotanker

 

Background

The need for an all-jet tanker was realized as the jet age came to be in the early 1950's. Jet aircraft were beginning to show up in the United States Air Force's inventory and larger aircraft like the B-47 Stratojet and the B-52 Stratofortress were no match for the piston-driven tankers of the day - consisting of the very few KB-29s and KB-50s and the majority of which being KC-97s. While these were good tankers in their own respects, they could not sufficiently refuel jet aircraft in midair. Take for instance a KC-97 and a B-52. The tanker would have to ask for the B-52 to fly at a much higher altitude to connect, then fly down to a lower altitude so that the tanker can gain speed. Even with jet engines fitted onto the KC-97 (becoming the KC-97L), the Air Force realized that they really needed an all-jet tanker.

The Boeing Company's model 367-80 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 fleet. The first aircraft flew in August 1956 and the initial production Stratotanker was delivered to Castle Air Force Base, Calif., in June 1957. The last KC-135 was delivered to the Air Force in 1965. Of the original KC-135A's, almost 400 have been modified with new CFM-56 engines produced by CFM-International. 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. Under another modification program, Air Force Reserve and Air National Guard tankers were re-engined with the TF-33-PW-102 engines. The re-engined tanker, designated the KC-135E, is 14 percent more fuel efficient than the KC-135A and can offload 20 percent more fuel. Through the years, the KC-135 has been altered to do other jobs ranging from flying command post missions to reconnaissance.

The KC-135 has a crew of four - the pilot, co-pilot, navigator, and boom operator. The boom operator, or boomer, takes his position in the cockpit "jump seat" on takeoffs and landings and moves to his position in the boomer's compartment during refueling operations. The boomer sits in a very awkward position in his "post", as he is flying flat on his stomach with his chin resting on a chinrest. In front of him, he has a great view of the boom and the receiving aircraft.

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. However, the decision to fly with the drogue must be done while the aircraft is on the ground.

The EC-135C is U.S. Strategic Command's flying command post. One EC-135C is on alert at all times, ready to take to the air and control bombers and missiles if ground control is lost. Special reconnaissance uses RC-135s and NKC-135A's are flown in test programs for Air Force Systems Command. Air Combat Command operates the OC-135 as an observation platform in compliance with the Open Skies Treaty.

With projected modifications, the KC-135 will fly and refuel into the next century. A new aluminum-alloy skin grafted to the underside of the wings will add 27,000 flying hours to the aircraft. Over the next few years, the aircraft will undergo a number of upgrades to expand its capabilities and improve its reliability. Among these are wingtip, air refueling pods (French C-135FRs carry these modification); improved cockpit instrument displays; additional communication equipment and enhanced navigation aids.

The future of the KC-135E Stratotankers remains in the hands of Congress as they fight to get an approval for the Air Force to lease, buy, and acquire at least 100 Boeing 767s to be modified as tankers. If and when the 767s (will be designated KC-767s) enter service, the Reserve and ANG KC-135Es will most likely be retired and their jobs taken over by KC-135Rs from active duty units. MacDill AFB in Tampa, Florida is slated to be a KC-767 base.

Recognizing the KC-135 Series

The KC-135 series of aircraft are rather easy to identify. However, they can very easily be confused with any other aircraft that shares a similar silhouette. If you THINK you see a KC-135, but aren't sure if it really is one, keep in mind the following:

Wings: Low-mounted, swept-back, and tapered with a positive slant.
Engines: Four turbofans mounted on pylons under the wings. Engines extend well forward of the wings' leading edges.
Fuselage: Round, cigar-shaped, tapers to the rear. Rounded nose, stepped-up cockpit.
Tail: Swept-back, tapered fin with a square tip. Horizontal stabilizers are swept-back, tapered, and mid-mounted on the fuselage.
Boom: Aft of the fuselage is a little set of "ruddervators" that belong to the refueling boom. Found on all KC-135s and most EC-135s.

If there is NO BOOM on the aircraft and it shares the same characteristics, you're looking at the following:

NKC-135A: Air Force testbed for laser lab projects. The NKC-135A at the USAF Museum in Dayton, OH has a giant laser turret on the top of its forward fuselage.

(O)C-135: Basic KC-135 airframe WITHOUT the boom. Some C-135s may have some unusual bumps from the top and the bottom of the fuselage while the OC-135s are easily identified by the "Open Skies" stripe on the tail.

KC-135 "Vomit Comet": Operated by NASA, the aircraft is recognized by its NASA markings. It is used to train astronauts in weightless environments (like in space) by flying parabolas.

WC-135: Easily identified with the "Weather" stripe on the tail.

If the aircraft has an extended-length nose, it could be either of the following:

EC-135N/E ARIA/ALOTS: Monstrous "Snoopy" nose housing a seven-foot diameter parabolic radar. The ALOTS pod is located on the left-side of the fuselage and it is an external fairing. E-model ARIAs are identifiable with their TF-33 turbofans (similar to those on the KC-135E) while N-model ARIAs are powered by J57 turbojets (same powerplant as the KC-135A/Q).

RC-135S Cobra Ball: In addition to "thimble" noses, electronic receivers mounted in cheek fairings and a teardrop-shaped fairing on the aft fuselage, these also have large circular windows in the fuselage for the photography of foreign ballistic-missile tests at long range.

RC-135U Combat Sent: Cheek fairings and additional fairings in the chin, boomer, wingtip, tailcone and fin-top positions.

RC-135V/W Rivet Joint: Extended "thimble" noses and large plate aerials under the center-section. External differences between the two variants are restricted to a lengthened cheek fairing on the W-model, which also lacks auxiliary air intakes on its engine pods.

If the aircraft does NOT have a boom or an extended-length nose, it is NOT a C-135 series aircraft. Examples below include:

E-3 Sentry: Slightly larger, but most notable feature is a giant rotating radome on the rear fuselage.

E-6B Mercury: Flown by the US Navy and is powered by CFM turbofan engines (similar to the KC-135R)

E-8 Joint STARS: Giant section of electronics hanging off the bottom right side of the forward fuselage.

The E-3, E-6, and E-8 are all based off the Boeing 707-320 airliner while the C-135 series is based off the 367-80 Prototype.

The Dash 80 is smaller than the Boeing 707s that were in commercial service.

Specifications

Primary Function: Aerial refueling and airlift
Prime Contractor: The Boeing Company
Power Plant:
    KC-135R/T: CFM International CFM-56 turbofan engines
    KC-135E: Pratt and Whitney TF-33-PW-102 turbofan engines
Thrust:
    KC-135R: 21,634 pounds each engine
    KC-135E: 18,000 pounds 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 miles per hour at 30,000 feet (9,144 meters)
Ceiling: 50,000 feet (15,240 meters)
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)
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
Pallet Positions: 6
Crew: Four: pilot, co-pilot, navigator, boom operator.
Aircraft equipped with PACER CRAG do not have a navigator on most missions.
The Air Force procured a limited number of navigator suites that can be installed for unique missions.
Date Deployed: August 1956
Inventory: Active duty, 253; Air National Guard, 222; Air Force Reserve, 70

Sources: USAF KC-135 Stratotanker factfile, The Aviation Zone

© 2003-2010 Steven Holzinger