The Rockwell B-1 Lancer
The heavy bomber seemed like it was headed for extinction in the 1960s, with development projects cancelled in favor of long-range strategic missiles. However, the US Air Force still felt a need for the type, and in the 1970s and 1980s pushed the development of a new heavy bomber, the Rockwell "B-1", which is now a prominent tool of American power. This document provides a history and description of the B-1.
The Rockwell B-1 Lancer Origins
In the late 1950s, the US Air Force planned to obtain large numbers of a Mach 3 bomber, the North American "B-70 Valkyrie", as the backbone of their strategic nuclear bombing force. However, improvements in Soviet air defenses and the development of the US long-range ballistic missile force rendered a high-altitude bomber like the B-70 obsolete. Only two "XB-70s" were completed, as high-speed research aircraft.
The Air Force still remained interested in a new manned bomber, and in fact no sooner had the B-70 been given the axe than the USAF began to consider another new bomber. The result was an "alphabet soup" of studies beginning with the "Subsonic Low Altitude Bomber (SLAB)" in 1961; the "Extended Range Strike Aircraft (ERSA)" in 1963; the "Advanced Manned Precision Strike System (AMPSS)" in 1964; and finally the "Advanced Manned Strategic Aircraft (AMSA)" in 1965:1969. Some jokers suggested that "AMSA" actually stood for "America's Most Studied Aircraft".
AMSA led to a request for proposals by the Air Force in November 1969. After due consideration of proposals from Boeing, General Dynamics, and North American Rockwell, the USAF awarded the contract for the "B-1" bomber to Rockwell on 5 June 1970, while General Electric was awarded a contract on the same day for the F101 afterburning turbofan engine that would power the aircraft.
The USAF originally wanted to build two ground-test airframes and five flying prototypes, but the requirement was cut in 1971 to one ground-test airframe and three flying prototypes. A fourth flying prototype would be ordered in 1976. The Air Force wanted 240 production machines, with the last of them to be delivered in 1979.
The initial flight of the first B-1 prototype was on 23 December 1974, followed by the first flight of the third prototype on 26 March 1976; The second prototype had been reserved for ground tests and didn't fly until 14 June 1976. The fourth prototype performed its initial flight on 14 February 1979. The fourth prototype featured, at least for part of its life, a distinctive dorsal spine housing test electronics. The spine was not fitted to any other B-1.
By the time of the first flight of the fourth prototype, however, the B-1 seemed all but dead. The 1970s saw a push for disarmament, and production of the B-1 was cancelled by US President Jimmy Carter on 30 June 1977. The price of the B-1 had been creeping upward, and Carter believed that cruise missiles would be a cheaper nuclear deterrent. The four B-1 prototypes were to remain in flight test as a form of "insurance". The Air Force went on to conduct another series of studies. Rockwell proposed a cost-reduced version of the B-1 that had fixed wings and could be used as a nuclear or conventional bomber, or a tanker. The Air Force didn't bite on that proposal, but was interested in an improved B-1 known as the "Long Range Combat Aircraft (LRCA)".
A resurgence of tensions with the Soviets and other factors led to the election of Ronald Reagan as US president in 1980. Reagan was committed to a major arms buildup, and this led to the resurrection of the B-1 LRCA as the "B-1B", which was promoted as a cruise-missile carrier though it still retained its free-fall nuclear bombing capability. The original B-1 prototypes were retroactively given the designation "B-1A". Reagan announced the decision to go ahead with the B-1B in October 1981, and formal contracts for a hundred production machines were finalized on 20 January 1982.
The second and fourth B-1A prototypes were to be used for B-1B development, with the fourth built up as the B-1B pre-production prototype. The second prototype was lost in a crash on 29 August 1984, killing the pilot, Rockwell chief test pilot Doug Benefield, and badly injuring the rest of the crew.
Despite the accident, the program went forward. The first production machine performed its initial flight on 18 October 1984, with initial service delivery on 29 June 1985. The last of the hundred was delivered by the end of the decade, with five bomb wings operating the type. Although formally named the "Lancer", the B-1B is more generally known as the "Bone", from "B-One".
The Rockwell B-1B Lancer description
The B-1B is a sleek, dartlike aircraft with a variable geometry "swing wing", which can be extended to full span for takeoff, landing, and long-range cruise, and swept back for high-speed penetration of adversary airspace. The swing wing does impose a weight penalty, but when extended it increases range and allows the B-1B to use shorter airstrips, assisting in dispersal of forces or forward-basing in time of war, while giving the bomber a good solid low-level ride in sweptback position.
Minimum sweep is 15 degrees and maximum sweep is 67.5 degrees. The junction where the wing sweeps into the wing glove features a "seal" to ensure aerodynamic cleanliness. The sealing system was derived from that developed for the European swing-wing Panavia Tornado strike fighter / interceptor, and features an inflatable bag covered with "fingers".
The wing has lift-enhancement devices for relatively short takeoffs with a full load, including seven-segment full-span leading-edge slats and six-segment trailing-edge Fowler-type flaps. There are no ailerons, with four spoilers on the top of each wing to provide lateral control and for use as airbrakes.
|Numbers built||approx 100|
|Wingspan||41.67 meters||136.71 feet|
|Wingspan swept||23.84 meters||78.22 feet|
|Length||44.81 meters||147.01 feet|
|Height||10.36 meters||33.99 feet|
|Empty weight||87,100 kilograms||192,000 pounds|
|MTO weight||216,400 kilograms||477,000 pounds|
|Max speed||1,330 kmh||826 mph|
|Service ceiling||15,300 meters||50,000 feet|
|Range||12,000 kilometers||7,460 miles|
|Crew||Four, Pilot, Co-Pilot, DSO & OSO|
|Engine type||F101-GE-102 afterburning turbofans|
|No. of Engines||Four|
The tail is of conventional configuration, with an all-moving horizontal tailplane and a single tailfin. The rudder has three sections, and the tailplanes can move in opposite directions to help with lateral control. They are also turned to their maximum nose-down position to act as an airbrake on landings.
There are small moveable vanes made of composites alongside the nose, with an anhedral of 30 degrees, referred to in an absolutely opaque way as the "structural mode control system (SMCS)" foreplanes. They were fitted because the long B-1B fuselage tends to flex fore-and-aft in low level flight. The SMCS vanes are linked to a set of accelerometers near the center and nose of the bomber under computer control to ensure a smooth ride at low level, increasing crew comfort and airframe life.
The keen-eyed will also notice a set of small fixed fins partly ringing the tailcone. These are not antennas, being instead "vortex generator" vanes that break up stagnant airflow over the "boundary layer" next to the surface of the tailcone. Vortex generators are often seen on wings to ensure that they maintain lift at low speeds, but it is unclear why boundary layer separation would be a problem over the tailcone.
There are eight self-sealing fuel tanks, filling up much of the fuselage and parts of the wing assembly. Additional fuel tanks can be installed in the weapons bays. All fuel tanks are pressurized with inert nitrogen to reduce fuel explosion hazard. Incidentally, the B-1B's "Fuel & Center Of Gravity Management Subsystem (FCGMS)" shifts fuel from one tank to another to maintain trim when the aircraft changes the sweep of its wings.
There is a midair refueling socket in the nose, just forward of the windshield. The position of the socket allows the bomber's flight crew to keep an eye on a tanker's refueling boom. The top of the nose is painted with a white "fishbone" pattern to help the tanker boom operator find the bomber's refueling socket at night.
The B-1B is made mostly of aluminum alloys and titanium, with a few composite elements. The central "box" that supports the swing wings is made of titanium. The aircraft is structurally reinforced to withstand the shock of a nuclear blast. The fuselage has smooth contours, with wing-body blending, and uses radar absorbing material (RAM) to give it a radar cross section only about one or two percent of that of the B-52, despite the fact that the two aircraft are roughly the same size. While the original prototype B-1As flew in a natty white anti-nuclear flash or a multitone camouflage paint scheme, operational B-1Bs have been given dark color schemes, eventually standardizing on an overall "gunship gray" paint job.
Rockwell B1-B powerplants
The B-1B is powered by four F101-GE-102 afterburning turbofans with 75.6 kN (7,710 kg / 17,000 lb) dry thrust and 136.9 kN (13,960 kg / 30,780 lb) afterburning thrust each. The B-1B can fly on only two engines if necessary, and can even stay in the air on one if much of the fuel is dumped.
The engines are organized into two pods with two engines each, mounted under the rear of the wing root gloves. Engine bleed is distributed throughout the aircraft for cabin pressurization and a range of other purposes. There is an auxiliary power unit (APU) mounted between the engines in each pod, primarily to start the engines, though the APUs can also be used for ground power. The APUs allow a quick startup of the engines so the bomber can get off the runway in a hurry. There's a switch on the nosewheel gear that a crewman can use to get the APUs and engines going even as the crew is getting into the bomber. A single APU can be used to fire up all four engines.
The engines have fixed inlets, instead of the variable inlets of the B-1A. The B-1A had been designed to perform high-altitude penetration at dash speeds in excess of Mach 2, but this was unrealistic even at the time, and though the B-1B's fixed inlets cut the high-altitude dash speed to Mach 1.25, they raised its low-level speed from the B-1A's Mach 0.85 to Mach 0.92. The B-1B's inlets are also designed to shield the engine fans from radar to improve stealth. The inlets feature a de-icing system.
One of the interesting minor details of the B-1B is that the Bone was originally delivered with "turkey feathers" shroud around the variable engine exhaust. The shroud was removed in the 1990s as a weight and maintenance reduction measure, leaving the variable exhaust actuators exposed.
The B-1B has tricycle landing gear, with twin-wheel nose gear and main gear with four-wheel 2-by-2 bogeys. The steerable nose gear retracts forward, while the main gear retracts into the center of the aircraft. The landing gear was reinforced from the B-1A to handle greater takeoff weights. Carbon brakes are fitted to help reduce landing roll.
B-1B Lancer weapon systems
The B-1B is fitted with three weapons bays that can carry a total of up to 34,020 kilograms (75,000 pounds) of munitions. There is a partition between the two forward weapons bays that can be moved or removed to permit carriage of different types of stores, including cruise missiles.
The B-1B was originally tasked for delivery of free-fall nuclear weapons. with each bay carrying a single "Multi-Purpose Launcher (MPL)" with a capacity of eight nukes. The destructive capability of a single B-1B loaded up with 24 nuclear weapons is beyond realistic comprehension.
The bomber could carry up to 24 Short Range Attack Missiles (SRAMs), but SRAM was obsoleted in 1990, and although the B-1B was partly promoted as a cruise missile carrier, arms limitation treaties ensured that it has never carried such weapons operationally. As a result, the partition between the front two weapons bays has never been moved or removed operationally, and Russian arms-treaty inspectors check to see that it stays where it is.
As discussed in the next section, there was some delay in qualifying the B-1B for conventional munitions. In principle, the B-1B can also be fitted with up to eight underfuselage hardpoints that can carry up to 26,760 kilograms (59,000 pounds) of munitions. In practice, it's never been done operationally, again because of arms-limitation treaties.
The Bone carries a crew of four, including pilot, copilot, "Defensive Systems Operator (DSO)", and "Offensive Systems Operator (OSO)". The pilot sits on the left in the forward compartment, with the copilot on the right. The DSO sits on the left in the rear compartment, with the OSO on the right. The two compartments are connected by a tunnel, which can be used as a sleep station on long missions. Although the B-1A had no windows in the rear compartment, test crews claimed that this made the place feel claustrophobic, and so the B-1B has a small window on each side of the rear compartment.
The crew enters the bomber through a hatch with an integral ladder behind the nosewheel bay that opens into the rear compartment. Crew accommodations are much more comfortable than those of the B-52, and the cockpit is regarded as very well laid out, with a clean dashboard arrangement and fighter-style stick controls for pilot and copilot. The B-1B is said to handle very nicely for an aircraft of its size, with one USAF test pilot commenting: "Sometimes you've got to stop and think how big this aircraft is before you do some things because it handles so well."
A toilet and galley are provided to support long missions, and there is space for two instructors along with the crew of four. However, the instructors sit on fixed seats, meaning that they have to bail out manually in case of an emergency. After the deaths of two instructors in a crash in 1987, USAF procedures were changed so that only four crew are taken on low-level training missions.
The large, sloping windshield has an electrical demisting and deicing system, and is reinforced against birdstrikes, a big threat in low-level flight. All windows can be covered with nuclear flash shields with zirconium titanate ports. While the first three B-1As featured a crew escape capsule, whose malfunction led to the fatal results in the loss of the second B-1A prototype, it was judged unstable at high speeds, and so the fourth B-1A and the B-1Bs use individual upward-ejecting Weber ACES II ejection seats.
The B-1B's avionics suite is more sophisticated than that of the B-1A. The "Offensive Avionics System (OAS)" used by the OSO was integrated by Boeing. One of the main elements is the Westinghouse AN/APQ-164 multimode offensive radar system, derived from the AN/APG-66 radar used on the F-16 fighter. The AN/APQ-164 features a phased array antenna, mounted in the nose of the bomber; and "low probability of intercept" operation, including the capability to take single "snapshot" sweeps, or partial sweeps. The radar has eleven modes, including terrain-following; navigation; tanker rendezvous; and targeting with a "synthetic aperture radar (SAR)" imaging capability.
The B-1B's original navigation systems include a precision inertial navigation system (INS), TACAN and ILS, and a Honeywell AN/ASN-121 radar altimeter. Honeywell also provided the offensive and defensive system displays, which includes three color multifunction displays (MFDs). Two of the displays are used by the OSO, while one is used by the DSO.
The DSO relies mainly on the Eaton "Defensive Countermeasures System (DAS)", which includes an AN/ALQ-161 receiver / jammer set; a tail warning radar; and an AN/ASQ-184 defensive management system, which can automatically control jamming functions and dispersal of chaff or flares from the "expendable countermeasures (EXCM)" system. There are eight dispensers arranged over the B-1B, with each dispenser having a capacity of twelve flares or 120 chaff cartridges. Current doctrine involves crosstraining the DSO and OSO to do each other's job if need be.
The B-1B also carries an extensive communications suite, including an Air Force Satellite Communications (AFSATCOM) link. There are a number of blade antennas for the communications and defensive that slightly disfigure the Bone's elegant contours. Most of the electronic systems are linked by quadruple-redundant MIL-STD 1553 data buses, and all are "hardened" to allow them to operate through the electromagnetic pulse (EMP) accompanying a nuclear blast, or other sources of electronic interference.
Other features of the B-1B include a "central integrated test system (CITS)" to help maintain the bomber; an "on-board oxygen generating system (OBOGS)" to eliminate the need to stock oxygen bottles; and a redundant hydraulic system.