Boeing B-47 Stratojet

The Boeing B-47 Stratojet was the first swept-wing jet bomber built in large numbers, and it carried Strategic Air Command’s nuclear strike force through the 1950s. It first flew on December 17, 1947, entered service in 1951 and was out of bomber service by the mid-1960s. It never dropped a bomb in anger, but its swept wing and podded engines became the layout that jet airliners copied.

This page covers how the B-47 was designed, why pilots found it so hard to land, what it did along the edge of Soviet airspace and how many were lost. The full specification table for the aircraft is on this page, beside the article.

Where the B-47 came from

The B-47 began as an Army Air Forces requirement for a jet-powered bomber, formalized in November 1944. The breakthrough that shaped it came from Germany. Boeing’s chief aerodynamicist, George Schairer, studied German swept-wing research and asked that it be applied to the new design, according to Air & Space Forces Magazine.

Boeing engineer Vic Ganzer suggested a sweepback angle of about 35 degrees. The design went through Boeing Models 424, 432 and 448 before settling on the Model 450, and the Army Air Forces ordered two XB-47 prototypes in April 1946.

The first XB-47 flew on December 17, 1947, from Seattle to Moses Lake, Washington, with Bob Robbins and Scott Osler at the controls. Robbins later said that before the flight he had prayed, “Oh God, please help me through the next two hours.” He soon realized he had an extraordinary aircraft.

The Air Force placed its first production order, for 10 B-47As, on September 3, 1948. It had beaten rival jet bomber designs that included the North American XB-45 Tornado, the Convair XB-46 and the Martin XB-48.

Swept wings, podded engines and bicycle landing gear

Almost everything about the B-47 broke with the propeller bombers it replaced. The wing swept back about 35 degrees. Four of the six engines hung in twin pods on pylons about a third of the way out along each wing, and the other two sat at the wingtips.

The slim fuselage left no room for conventional landing gear. Boeing used bicycle gear instead: two main gear assemblies in tandem under the fuselage, with retractable outrigger wheels to keep the aircraft upright.

That arrangement had a price. The aircraft could not be rotated for takeoff or flared for landing. The two pilots sat in tandem under a long fighter-style bubble canopy.

The shape proved influential. Air & Space Forces Magazine credits the B-47 with influencing the KC-135 Stratotanker, the Boeing 707 family and the Douglas DC-8.

The three-man crew and the B-47 cockpit

A B-47 flew with three people in a pressurized crew compartment. The pilot and copilot sat in tandem, and the navigator, who also served as bombardier, worked from radar in a dark compartment in the nose.

The original plan called for all three crew members to be “triple rated” in every crew skill. That proved unsustainable as the program grew.

The B-47’s only defensive armament was a remote-controlled tail turret with two 20 mm cannons, aimed by radar. The copilot ran it. On early B-47Bs the radar fire-control system was often replaced with an optical sight, and the copilot could swivel his seat to face backward and aim the guns directly.

On the B-47A, the ejection seats fired the pilots upward and the navigator downward.

Engines and rocket-assisted takeoffs

The XB-47 prototypes flew on J35 turbojets. Production aircraft moved to the General Electric J47, and the B-47E used the J47-GE-25A. Each engine produced 7,200 lbf (32 kN) of thrust, but only while water-methanol injection was running, and the injection left a heavy trail of black smoke.

Early B-47E engines without injection produced noticeably less. Jet engines of the period were also slow to respond, taking 12 to 20 seconds to spool up from idle to full power.

A heavily loaded B-47 could need help getting airborne. Early aircraft had mounts for nine rocket-assisted takeoff (RATO) bottles on each side of the rear fuselage.

The slow engine response matters for the landing story below. A pilot who throttled back on approach could not count on getting full power quickly if something went wrong.

Was the B-47 hard to fly?

Yes, in several ways. Chuck Yeager, who also flew the XB-47, noted it was so aerodynamically clean that he had difficulty landing it. Wikipedia sums up the aircraft as sluggish on takeoff and too fast on landing.

Flight testing turned up two early problems. A tendency to “Dutch roll,” weaving in widening S-turns, was cured by a yaw damper that moves the rudder automatically. A tendency to pitch up at high speed was cured with small vanes called vortex generators.

The wing flexed so much that the ailerons lost their effect above 456 knots, so the aircraft was placarded to 425 knots. At the top of its envelope, around 35,000 feet (10,700 m), the margin between maximum Mach number and stall speed shrank to about 5 knots, a condition pilots call the coffin corner.

Landing was the hardest part. The wing loading demanded an approach speed of 180 kt (207 mph, 333 km/h), and the clean airframe would not slow down on its own. Pilots descended from cruise altitude with the rear landing gear lowered for drag, then deployed a 16-foot approach parachute in the pattern and a 32-foot ribbon parachute for the landing roll.

Because the engines took so long to spool up, a B-47 could not easily make a touch-and-go landing.

What the B-47 carried

The B-47E carried its weapons internally. Wikipedia lists up to 25,000 lb (11,300 kg) of ordnance, including two Mark 15 nuclear bombs, four B28 bombs, a single B41 with a yield listed at 25 megatons, or 28 conventional 500-lb bombs.

Those loads were never dropped in anger. The B-47 spent its career as a deterrent.

How many B-47s were built

Most sources put B-47 production at 2,032 aircraft, split between Boeing (1,373), Lockheed (385) and Douglas (274). Other sources print totals from 2,039 to 2,042.

The B-47E was by far the most numerous version, with 1,341 built. Production included 10 B-47As and 399 B-47Bs, and many of the B-47Bs were later brought up to B-47E standard.

The reconnaissance versions were smaller in number: 240 RB-47Es, 32 RB-47Hs, 3 ERB-47Hs and 15 RB-47Ks.

B-47 variants

The RB-47E was the main photo-reconnaissance version. Its nose was stretched by 34 inches (0.86 m) to hold up to 11 cameras. The RB-47H carried extra crew and electronics to collect intelligence on Soviet radar and air defenses.

Lockheed converted 34 B-47Es into WB-47E weather reconnaissance aircraft in the early 1960s. They replaced B-50 weather aircraft that had suffered several fatal crashes. Fourteen RB-47Es became radio-controlled QB-47E target drones.

The B-47 also served as a testbed. The Navy used an NB-47E to test the engine for the Lockheed S-3 Viking, and a Canadian CL-52 tested engines for the Avro CF-105 Arrow. B-47E serial number 53-2280 was used as a fly-by-wire testbed shortly before the type left service.

The B-47 in Strategic Air Command

In 1951 the B-47 began replacing the propeller-driven B-29 and B-50 in SAC’s medium bomber units. It carried about the same bomb tonnage as those aircraft, but it was much faster, according to the National Museum of the U.S. Air Force.

Peak strength came in 1958, with roughly 1,360 B-47 bombers in 28 wings plus about 175 RB-47 reconnaissance aircraft, depending on the source.

The B-47 lacked the range of the B-36 and, later, the B-52. SAC wings therefore deployed to forward bases around the world.

Tours began at three months and were cut to three weeks under the Reflex Action program from 1957. Aerial refueling extended the B-47’s reach further.

B-47 vs B-52

The B-47 was a medium bomber with a three-man crew. The B-52 that followed was a heavy bomber with the range the B-47 never had. For a full look at the later aircraft, see our B-52 Stratofortress page.

The B-47’s end came as the B-52 and, increasingly, missiles took over the strategic mission. The Federation of American Scientists links its phase-out in the 1960s to the arrival of ICBMs and submarine-launched missiles and to better replacement aircraft. For a wider view of the category, see types of bomber planes and the best bombers in the world.

Reconnaissance flights over the Soviet Union

The first overflight of Soviet territory by a B-47B came on October 15, 1952. Between 1952 and 1956, photo-reconnaissance B-47s made several overflights, bringing back pictures of Soviet military and industrial sites, according to the Air Force museum.

In 1956, 16 RB-47Es and five RB-47Hs operating from Thule, Greenland, flew 156 overflights along the length of Siberia under Project HOMERUN. For other aircraft built for this work, see the U-2 and our spy planes roundup.

The flights were dangerous.

Soviet fighters damaged one reconnaissance Stratojet and shot down two, killing seven Air Force personnel and leaving two imprisoned for a time. The best-known loss was an RB-47H, serial number 53-4281, shot down by a MiG-19 over the Barents Sea on July 1, 1960. Four of its six crew died, and the two survivors were held until 1961.

Did the B-47 see combat?

Not as a bomber. Wikipedia notes that the B-47 never saw combat as a bomber, while reconnaissance RB-47s occasionally came under fire near or within Soviet airspace.

The Stratojet was built to deter a war, and it spent its career on alert and on reconnaissance.

How many B-47s crashed?

Wikipedia reports that 203 B-47s were lost in crashes over the type’s operating life, with 464 deaths. Structural fatigue was one of the causes.

Between March 13 and April 16, 1958, six B-47s crashed. Investigators traced the failures to fatigue in the lower wing skin, caused by stress corrosion of the “milk bottle pin,” the main fitting that attached the wing to the fuselage. The fix, called Project Milk Bottle, strengthened the wing mountings and extended the fleet’s service life by six years.

Several accidents involved nuclear weapons. On March 10, 1956, four B-47s left MacDill Air Force Base in Florida for Morocco. One failed to make contact with its tanker over the Mediterranean, and neither the aircraft, its two nuclear weapon cores nor its crew were ever found.

On July 27, 1956, a B-47 of the 307th Bombardment Wing crashed at RAF Lakenheath, England. It killed the crew and hit a storage igloo holding three Mark 6 nuclear weapons. The weapons lacked their fissile cores, and the high explosives did not ignite.

On February 5, 1958, a B-47 carrying a Mark 15 bomb without its core was damaged during a simulated combat exercise against an F-86 and had to drop the weapon off the Georgia coast near Tybee Island.

Retirement, survivors and the last flight

The last B-47 bombers retired to Davis-Monthan Air Force Base in Arizona by February 1966. The last RB-47H left service in December 1969, and the last Air Force Stratojets, WB-47E weather aircraft, flew until 1969. The Navy used test and electronic-warfare versions into the mid-1970s.

One offer never went anywhere. During the 1962 Sino-Indian war, India’s prime minister asked for two squadrons of B-47s and training for Indian bombardiers. The deal did not progress.

The last recorded B-47 flight took place on June 17, 1986. A B-47E was restored to flying condition for a one-time ferry from Naval Air Weapons Station China Lake, California, to Castle Air Force Base, where it went on display.

Wikipedia lists 22 surviving B-47s, all in the United States and none airworthy. They include the only surviving XB-47 prototype, now at the Air Force Flight Test Museum at Edwards Air Force Base, and an RB-47H at the National Museum of the U.S. Air Force in Dayton, Ohio.

How much did a B-47 cost?

Aerospaceweb lists a unit cost of $1,887,770, and the Federation of American Scientists puts it at under two million dollars per airplane. Neither source states a dollar year, so read it as a contemporary figure, not a modern-dollar one. The panel on this page shows $1.9 million.

The prototype program was far more expensive. Air & Space Forces Magazine puts the XB-47 prototype contract at nearly $10 million.

Explaining the B-47’s numbers

The specification table for the aircraft is on this page, and a few of its figures need context.

The panel’s range of 4,038 nm (4,650 mi, 7,480 km) is a ferry range with underwing tanks. It is not what a B-47 could do on a bombing mission. With a 20,000 lb bomb load, Wikipedia lists a combat range of 2,013 miles (3,240 km), which is why SAC leaned on forward bases and aerial refueling.

The panel’s maximum speed of 606 mph (976 km/h) is a performance figure, but the aircraft was placarded to 425 knots. Its service ceiling is 40,500 ft (12,300 m), yet the margin between stall and maximum Mach was already thin near 35,000 ft. Maximum takeoff weight also varies by source and sub-model, so treat any single figure as an indication.

The panel’s 6 × 7,200 lbf (32 kN) thrust is the water-injection rating of the J47-GE-25A. Without injection the engines produced less, which is part of why heavy takeoffs needed rocket assistance.

Frequently Asked Questions

Are any B-47s still flying?

No. Wikipedia lists 22 surviving B-47s, all in the United States and none airworthy. The last recorded flight was a one-time ferry on June 17, 1986, from China Lake to Castle Air Force Base.

Did the B-47 see combat?

Not as a bomber. The B-47 never dropped a weapon in anger. Reconnaissance versions came under fire near Soviet airspace, and an RB-47H was shot down over the Barents Sea on July 1, 1960.

Was the B-47 hard to fly?

Yes, especially to land. Its clean airframe produced a high approach speed, its bicycle gear could not be rotated or flared, and its engines were slow to spool up. Pilots used drag chutes and lowered the rear gear to slow down.

How many B-47 crashed?

Wikipedia reports 203 B-47s lost in crashes, with 464 deaths. Six crashes in March and April 1958 led to Project Milk Bottle, which strengthened the wing mountings.

How many crew did a B-47 have?

Three: a pilot, a copilot who also operated the tail guns, and a navigator who served as bombardier. The pilots sat in tandem under a fighter-style canopy.

What guns did the B-47 have?

Two 20 mm cannons in a remote-controlled tail turret, aimed by radar. It had no other defensive guns.

How much did a B-47 cost?

About $1.9 million per aircraft, based on a published unit cost of $1,887,770. No source states the dollar year.

What replaced the B-47?

The B-52 Stratofortress took over the heavy strategic role, and missiles increasingly took over the deterrent mission. The last B-47 bombers left SAC service by 1966.