Daily Archives: December 12, 2023

12 December 1991: In which a Boeing 747 goes supersonic.

Evergreen International Airlines’ Boeing 747-121, N475EV, photographed at Hellinikon International Airport, Athens, Greece, 1 January 1991. The airliner has just been converted to a freighter. (Savvas Garozis)

12 December 1991: A Boeing 747 freighter operated by Evergreen International Airlines was en route from New York’s John F. Kennedy International Airport (JFK) to Tokyo, Japan, with an intermediate stop at Anchorage International Airport (ANC), Alaska, U.S.A. The 747 had a flight crew of six and no passengers.

At about 5:20 a.m., Central Standard Time (11:15 UTC), the 747 was cruising at Flight Level 310 (31,000 feet/9,449 meters) near Nakina, a small village approximately 150 nautical miles (173 statute miles/278 kilometers) northeast of Thunder Bay, Ontario, Canada.

The flight crew observed that the airplane’s Inertial Navigation System (INS) FAIL warning lights were on. Checking their instruments, they found that the 747 had entered a 90° right bank and was in a 30°–35° descent. It was rapidly losing altitude and gaining speed.

Before the crew could recover, N475EV had lost over 10,000 feet (3,048 meters) and reportedly reached 0.98 Mach in its dive. After regaining control of the 747, the crew made an emergency landing at Duluth, Minnesota, at 5:43 a.m., Central Standard Time.

On inspection, a large hole, approximately 3 feet × 15 feet (0.9 × 4.5 meters), was found in the leading edge of the right wing, inboard of the Number 3 engine. Three sheet metal panels had torn off, then struck the right horizontal stabilizer, denting its leading edge. On landing, a flap on the left wing fell off.

According to an article in the Seattle Times, an investigator for the National Transportation Safety Board confirmed that the 747 had exceeded its design speed of 0.92 Mach, but as the Flight Data Recorder had not yet been analyzed, “. . . he could not confirm reports that it reached Mach 1.25. . . .”

The Seattle Times reported the incident:

Dive! 747 In Unexplained Incident — Canada Investigating Automatic Pilot Controls After Near-Supersonic Scare

Canadian authorities are scrutinizing the automatic flight controls of a Boeing 747-100 jumbo jet after the plane inexplicably rolled 90 degrees to its right and dove two miles at near-supersonic speed.

The incident occurred last Thursday as the plane, a passenger jetliner converted to a freighter, was cruising at 31,000 feet above Nakina, Ont., on a New York-to-Anchorage flight. The jet is owned and operated by Evergreen International Airlines, based in McMinnville, Ore.

The pilots righted the craft at 22,500 feet, then made a safe emergency landing at Duluth, Minn.

None of the six Evergreen employees on board, including the three-member flight crew, was injured, according to Dave McNair, investigator for the Transporation Safety Board of Canada.

McNair said the jumbo jet’s four turbofan engines functioned properly. He said a broad investigation would take several months and will include an examination of the sophisticated computers designed to fly the plane automatically for most of the flight.

“What we’ll be doing is looking at the entire autopilot logic and any associated logic,” he said.

At some point during the incident, three large panels beneath the leading edge of the right wing tore off, leaving a 3-by-15-foot hole on the forward, inboard section of the right wing.

The panels damaged the right flap (located on the trailing edge of the wing) and dented the right-side forward edge of the horizontal tail section, according to McNair and Boeing spokesman Chris Villiers. Upon landing, part of the left flap came off, as well, Villiers said.

Authorities said it was unclear whether the panels from the right wing came loose first and, thus, precipitated the roll and dive, or if the parts shook loose as the plane careened at a 30- to 35-degree angle of descent – more than three times a normal rate of descent. McNair said age of the 21-year-old aircraft is not believed to be a factor.

The 747-100 is designed to withstand a top speed of Mach 0.92 – nine-tenths the speed of sound, or more than 500 miles per hour at that altitude. McNair said the plane reached speeds faster than that during the dive, but he could not confirm reports that it reached Mach 1.25, because precise information from the flight-data recorder was not immediately available.

Tacoma aviation safety expert John Nance, a former 747 pilot, said it is plausible that the plane would begin to disintegrate once the speed surpassed its so-called “design limit.”

Nance described modern jetliners as “metallic eggshells, very strong when used exactly as they are designed to be used; very weak when not.”

The Evergreen incident occurred on the same day that whistleblower Darrell Smith, a former Boeing 747 computer analyst, made public an internal Boeing audit outlining major flaws in a software program used by a computer that senses the position of key moving parts on the Boeing 747-400, an advanced version of the 747-100.

Boeing officials said the computer Smith reviewed on the 747-400 doesn’t exist on the 747-100. The Evergreen plane was one of the first delivered from Boeing’s Everett plant in July 1970 to Pan Am.

Even so, Smith’s allegations and the Evergreen roll-and-dive add to a string of instances over the past two years in which alleged or apparent flaws in Boeing technology have become part of a heated air-safety debate:

— Last May, an electronically controlled engine-braking device, called a thrust reverser, inexplicably deployed as a Lauda Air 767-300ER jetliner climbed away from Bangkok, instantly flipping the plane into a supersonic crash dive. All 223 on board were killed.

Authorities still do not fully understand how a stray electrical signal, vibration or some other phenomena could have deployed the reverser. Meanwhile, Boeing has steadfastly declined to answer a call by the National Transportation Safety Board to upgrade pilot instructions on what to do if a reverser warning light illuminates in the cockpit during flight. Electronic reversers are used on all Boeing jetliners delivered in the past few years – nearly 1,700 planes all told.

— Last February, Hoot Gibson, a former Trans World Airlines pilot revealed nine complaints from pilots citing major control problems on Boeing 727 jets apparently related to a random, mysterious malfunction of the autopilot computer.

Gibson has waged a 12-year battle with the NTSB and Boeing to clear his name of allegations that he caused a TWA 727 to careen dangerously from a high altitude by attempting to improperly manipulate the controls to enhance the plane’s performance. Gibson, who wrestled back control of the plane at the last minute, maintains that a flaw in the autopilot triggered the dive.

— In April 1990, the NTSB, relying on Boeing technical data and analysis, ruled that the pilots of USAir Flight 5050 made the wrong decision to abort the takeoff of a 737-400 from New York’s LaGuardia airport on Sept. 20, 1989. The pilot decided to abort takeoff when the plane lurched left because the rudder was stuck full left. (The rudder, the upright section of the tail, is supposed to be in neutral for takeoff.)

The NTSB ruled that the pilots should have noticed the stuck rudder and, in any case, should have followed through with the takeoff, even with the stuck rudder. Two passengers were killed as the plane ditched into Bowery Bay.

The ruling upset pilots who felt little credence was given to scores of reports of problems with a new type “rudder trim.” Reports from pilots said it was moving the rudder without being commanded to do so.

The Seattle Times, 19 December 1991

A year later, the Chicago Tribune reported,

Tom Cole, a spokesman at Boeing Commercial Airplane Co., said original flight tests of 747s conducted in 1969 and 1970 took 747-100 models to speeds of Mach 0.99.

In addition, Boeing knows one case in which a 747 operated by Evergreen International made an emergency descent at speeds that exceeded Mach 1, he said.

Chicago Tribune, 20 December 1992

Following the December 1991 incident, N475EV was repaired and returned to service.

This was not the first time that 19638 had been damaged:

Boeing 747 19638 (RA003) with a nose boom during flight testing, 1969. (Jeff Ohlston/Boeing)

Boeing 747-121, serial number 19638, line number RA003, had made its first flight on 11 July 1969. Boeing used the aircraft for flight and certification testing. On completion of these tests, it was to be flown to Boeing’s Renton plant to be modified to production standards, refurbished, and then delivered to the new owner, Pan American World Airways.

While landing on Runway 15 at Renton Airport, at 11:11 a.m., 13 December 1969, 19638 struck an embankment about 20 feet (6 meters) short of the runway. None the 11 Boeing employees on board were injured. The Number 3 and 4 engines were damaged and caught fire. The right landing gear was pulled backward, but held to the wing by linkages and actuators. The flaps on the right wing were damaged. The right wing’s lower surface was punctured. The fires were quickly extinguished.

A video clip of the accident is available on YouTube:

N732PA was repaired and finally delivered to Pan American on 13 July 1970. The 747 was christened Clipper Storm King. (It was later renamed Ocean Telegraph.)

Pan American World Airways’ Boeing 747-121, N732PA, Clipper Storm King, photographed at London Heathrow, 30 August 1971. © Stephen Rendle (Image used with permission.)

Pan Am operated the airliner for nearly 21 years. It was sold to Evergreen International Airlines, 1 July 1991, and converted to an air freighter at Evergreen’s maintenance depot at Marana, Arizona. It was re-registered N475EV.

Evergreen flew N475EV until it was sold to Tower Air, 13 September 1994. Under new ownership, the Boeing 747 was again re-registered, to N615FF.

Tower Air Boeing 747 N615FF, photographed at Kai Tak Airport, Hong Kong. © Andrew Hunt (Image used with permission)

The FAA registered the 747 to Kalitta Equipment LLC, 3 August 2000. The N-number did not change. The airplane’s registration was canceled 30 June 2017.

© 2020, Bryan R. Swopes

12 December 1957

Major Adrian E. Drew, U.S. Air Force, 1920–1985. (Photograph courtesy of Neil Corbett, Test & Research Pilots, Flight Test Engineers)

12 December 1957: Major Adrian Eason Drew, U.S. Air Force, commanding officer, 481st Fighter Bomber Squadron, 27th Fighter Bomber Wing, Tactical Air Command, set a new Fédération Aéronautique Internationale (FAI) absolute speed record over the 15/25 kilometer course at Edwards Air Force Base, California.¹ Major Drew flew a modified McDonnell F-101A-5-MC Voodoo, serial number 53-2426.

The Voodoo, the ninth production F-101A, had been bailed to Pratt & Whitney by the Air Force to test a new J57-P-55 afterburning turbojet engine intended for the F-101B Voodoo, and it was redesignated JF-101A. The new engine produced 16,000 pounds of thrust with afterburner. The modified aircraft had longer jet exhaust tubes, and air scoops were installed in the belly to provide additional cooling air for the afterburners.

McDonnell JF-101A Voodoo 53-2426, takes off at Edwards Air Force Base on Operation Fire Wall, 12 December 1957. (U.S. Air Force)
McDonnell JF-101A Voodoo 53-2426, takes off at Edwards Air Force Base on Operation Fire Wall, 12 December 1957. (U.S. Air Force)
Thompson Trophy. (NASM)

At 39,000 feet (11,887 meters), Major Drew accelerated for 65 miles (105 kilometers) before entering the 10.1 statute mile (16.25 kilometers) course. He made one pass in each direction. Actual time on course, each way, was 29.8 seconds. The official average speed for the two passes is 1,943.5 kilometers per hour (1,207.64 miles per hour). Although the air temperature was -79 °F. (-62 °C.), frictional heating brought the Voodoo’s skin temperature to 190 °F. (88 °C.), high enough to blister the airplane’s paint.

Major Drew was awarded the Distinguished Flying Cross and the Thompson Trophy for 1957.

Major Adrian E. Drew, 481st Fighter Bomber Squadron, 27th Fighter Bomber Wing, U.S. Air Force, at Edwards AFB, 12 December 1957. (U.S. Air Force via Jet Pilot Overseas)
Major Adrian E. Drew, U.S. Air Force, at Edwards AFB, 12 December 1957.  At right is McDonnell Aircraft Corporation test pilot William S. Ross. In 1986, Ross was appointed president of the Aircraft Division of McDonnell Douglas Corporation. (U.S. Air Force via Jet Pilot Overseas)

Adrian Eason Drew was born 8 October 1920 in Georgia, the first of six children of John Robert Drew, a farmer, and Ada Elma Eason Drew.

After one year of college, Adrian Drew enlisted as a private in the U.S. Army Air Corps, 31 March 1942, at Fort McClellan, Alabama. He was 5 feet, 8 inches (1.73 meters) tall and weighed 143 pounds (64.9 kilograms).

On 14 November 1942, Drew married Miss Sarah B. Kaylor in Pinellas County, Florida. They would have three daughters, Nancy, Bonnie and Jo Anne.

Colonel Drew was a combat pilot during World War II, the Korean War and the Vietnam War. He commanded the 309th Strategic Fighter Squadron from January to October 1955, flying the Republic F-84 Thunderjet. In August 1957, he became the first commanding officer of the 481st Fighter Bomber Squadron at Bergstom Air Force Base,  Austin, Texas. Lieutenant Colonel Drew commanded the 354th Tactical Fighter Squadron at George Air Force Base, California, from 1962 to 1964, flying the Republic F-105D Thunderchief, and briefly commanded the 355th Tactical Fighter Wing.

Two weeks before a scheduled promotion to Brigadier General, Colonel Drew suffered a major heart attack and was forced to retire from the Air Force. He died 27 July 1985 at the age of 64 years. He was buried at Shawnee View Gardens Cemetery, Cumming, Georgia.

McDonnell JF-101A Voodoo 53-2426, holder of the World Absolute Speed Record, 1957. (U.S. Air Force)

The McDonnell F-101 Voodoo was originally designed as a single-seat, twin-engine long range bomber escort, or “penetration fighter” for the Strategic Air Command, but was developed as a fighter bomber and reconnaissance airplane. The Voodoo first flew 29 September 1954, and the first F-101A was delivered to the Air Force 2 May 1957.

The F-101A was 67 feet, 5 inches (20.549 meters) long with a wingspan of 39 feet, 8 inches (12.090 meters). It was 18 feet (5.486 meters) high. The Voodoo weighed 24,970 pounds (11,245 kilograms) empty and had a maximum takeoff weight of 50,000 pounds (22,680 kilograms).

The standard F-101A was equipped with two Pratt & Whitney J57-P-13 afterburning turbojet engines. The J57 was a two-spool axial-flow turbojet which had a 16-stage compressor (9 low- and 7 high-pressure stages), and a 3-stage turbine (1 high- and 2 low-pressure stages). The J57-P-13 was rated at 10,200 pounds of thrust (45.37, and 15,800 pounds (70.28 kilonewtons) with afterburner.

The J57-P-55 engines installed in the JF-101A were rated at 10,700 pounds of thrust (49.60 kilonewtons), and 16,900 pounds (75.18 kilonewtons) with afterburner. They were 20 feet,  11.93 inches (6.399 meters) long, 3 feet, 4.5 inches (1.029 meters) in diameter, and weighed 5,215 pounds (2,365 kilograms).

The maximum speed of the F-101A was 1,009 miles per hour (1,624 kilometers per hour) at 35,000 feet (10,668 meters). Its service ceiling was 55,800 feet (17,008 meters). It carried 2,341 gallons (8,862 liters) of fuel internally. With external tanks, the fighter bomber had a maximum range of 2,925 miles (4,707.3 kilometers).

The F-101A was armed with four 20mm Pontiac M39 single-barreled revolver cannon, with 200 rounds per gun. It could carry a Mark 28 bomb on a centerline mount.

McDonnell JF-101A Voodoo 53-2426 is on static display at Cannon Air Force Base, New Mexico.

McDonnell JF-101A Voodoo 53-2426, FAI World Speed Record Holder and Thompson Trophy winner, Operation Fire Wall, landing at Edwards Air Force Base, 12 December 1957. (U.S. Air Force)
McDonnell JF-101A Voodoo 53-2426, FAI World Speed Record Holder and Thompson Trophy winner, Operation Fire Wall, landing at Edwards Air Force Base, 12 December 1957. (U.S. Air Force)

A McDonnell Aircraft Corporation film about Operations Sun Run and Fire Wall is available of YouTube:

¹ FAI Record File Number 9064

© 2017, Bryan R. Swopes

12 December 1953

Bell X-1A 48-1384 in flight. The frost band on the fuselage shows the location of the cryogenic propellant tank. (U.S. Air Force)

12 December 1953: On its tenth flight, U.S. Air Force test pilot Major Chuck Yeager flew the Bell X-1A rocket plane to Mach 2.435 (1,618 miles per hour/2,604 kilometers per hour) at 74,700 feet (22,769 meters), faster than anyone had flown before.

After the rocket engine was shut down, the X-1A tumbled out of control—”divergent in three axes” in test pilot speak—and fell out of the sky. It dropped nearly 50,000 feet (15,240 meters) in 70 seconds. Yeager was exposed to accelerations of +8 to -1.5 g’s. The motion was so violent that Yeager cracked the rocketplane’s canopy with his flight helmet.

Yeager was finally able to recover by 30,000 feet (9,144 meters) and landed safely at Edwards Air Force Base.

Yeager later remarked that if the X-1A had an ejection seat he would have used it.

Bell Aircraft Corporation engineers had warned Yeager not to exceed Mach 2.3.

Major Charles E. Yeager, U.S. Air Force, seated in the cockpit of the Bell X-1A, 48-1384, circa 1953. (U.S. Air Force)

The following is from Major Charles E. Yeager’s official post-flight report:

After a normal drop at 31,000 feet, chambers , , and were ignited and [the] airplane was accelerated up to .8 Mach number. A flight path was formed holding .8 Mach number up to 43,000 feet where chamber was ignited and the airplane accelerated in level flight to 1.1 Mach number. A climb was again started passing through 50,000 feet at 1.1 Mach number, 60,000 feet at 1.2 Mach number and a push-over was started at 62,000 feet. The top of the round-out occurred at 76,000 feet and 1.9 Mach number. The airplane was accelerated in level flight up to 2.4 [2.535 indicated] Mach number where all of the rocket chambers were cut. The flight path was very normal and nothing uneventful [sic] happened up to this point. After the engine was cut, the airplane went into a Dutch roll for approximately 2 oscillations and then started rolling to the right at a very rapid rate of roll. Full aileron and opposite rudder were applied with no effect on the rate of roll of the airplane. After approximately 8 to 10 complete rolls, the airplane stopped rolling in the inverted position and after approximately one-half of one second started rolling to the left at a rate in excess of 360 degrees per second, estimated by the pilot. At this point the pilot was completely disoriented and was not sure what maneuvers the airplane went through following the high rates of roll. Several very high ‘g’ loads both positive and negative and side loads were felt by the pilot. At one point during a negative ‘g’ load, the pilot felt the inner liner of the canopy break as the top of his pressure suit helmet came in contact with it. The first maneuver recognized by the pilot was an inverted spin at approximately 33,000 feet. The airplane then fell off into the normal spin from which the pilot recovered at 25,000 feet.

Flight test data from Yeager's 12 December 1953 flight superimposed over a photograph of the bell X-1A. (NASA)
Flight test data from Yeager’s 12 December 1953 flight superimposed over a photograph of the Bell X-1A. (NASA)

The following is a transcript of radio transmissions during the flight:

Yeager: Illegible [inaudible]—gasping—I’m down to 25,000 over Tehachapi. Don’t know
whether I can get back to the base or not.
Chase (Ridley): At 25,000 feet, Chuck?
Yeager: Can’t say much more, I got to (blurry—save myself).
Yeager: I’m—(illegible)—(Christ!)
Chase (Ridley): What say, Chuck?
Yeager: I say I don’t know if I tore anything up or not but Christ!
Chase (Murray): Tell us where you are if you can.
Yeager: I think I can get back to the base okay, Jack. Boy, I’m not going to do that any more.
Chase (Murray): Try to tell us where you are, Chuck.
Yeager: I’m (gasping)…I’ll tell you in a minute. I got 1800 lbs [nitrogen] source pressure.
Yeager: I don’t think you’ll have to run a structure demonstration on this damned thing!
Chase (Murray): Chuck from Murray, if you can give me altitude and heading, I’ll try to check you from outside.
Yeager: Be down at 18,000 feet. I’m about—I’ll be over the base at about 15,000 feet in a minute.
Chase (Murray): Yes, sir.
Yeager: Those guys were so right!
Yeager: Source pressure is still 15 seconds, I’m getting OK now.
Yeager: I got all the oscillograph data switches off. 4 fps camera off, it’s okay.
Bell Truck: Jettison and vent your tanks.
Yeager: I have already jettisoned. Now I’m venting both lox and fuel. Leaving hydrogen peroxide alone.
Bell Truck: Roger.
Yeager: I cut it, I got—in real bad trouble up there.
Yeager: Over the base right now, Kit, at 14,500 feet.
Chase (Murray): I have you.

A North American F-86E-10-NA Sabre chase plane, 51-2848, follows the Bell X-1A as it glides toward Rogers Dry Lake. (NASA)
A North American F-86E-10-NA Sabre chase plane, 51-2848, follows the Bell X-1A as it glides toward Rogers Dry Lake. (NASA)

In his autobiography, Always Another Dawn, NACA test pilot Albert Scott Crossfield wrote:

Probably no other pilot could have come through that experience alive. Much later I asked Yeager, as a matter of professional interest, exactly how he regained control of the ship. He was vague in his reply, but he said he thought that after he reached the thick atmosphere, he had deliberately put the ship into a spin.

“A spin is something I know how to get out of,” he said. “That other business— the tumble—there is no way to figure that out.”

. . . Yeager received many accolades. I didn’t begrudge him one of them. If ever a pilot deserved praise for a job well done, it was Yeager. After that X-1A episode, he never flew a rocketplane again.

Always Another Dawn: The Story of a Rocket Test Pilot, by A. Scott Crossfield with Clay Blair, Jr., The World Publishing Company, Cleveland and New York, Chapter 19 at Pages 183–184.  

Bell X-1A 48-1384 (U.S. Air Force)

The Bell X-1A, 48-1384, was an experimental rocket-powered high-speed, high-altitude research aircraft. It was one of four second-generation X-1s (including the X-1B, X-1D and X-1E), specifically designed to investigate dynamic stability at speeds in excess of Mach 2 and altitudes greater than 90,000 feet. It was a mid-wing monoplane with retractable tricycle landing gear. The airplane was 35 feet, 6.58 inches (10.835 meters) long with a wingspan of 30 feet, 6 inches (9.296 meters) and overall height of 10 feet, 2.37 inches (3.261 meters). The wheelbase, measured from the nose wheel axle to the main wheel axle, was  13 feet, 5.13 inches. (4.093 meters). The main wheel tread was 4 feet, 3 inches (1.295 meters). The X-1A design gross weight was 10,668 pounds (4,839 kilograms).

The X-1A was powered by a single Reaction Motors XLR11-RM-5 rocket engine with four independent combustion chambers. The XLR11 was fueled with ethyl alcohol and liquid oxygen. It produced 6,000 pounds of thrust (26.689 kilonewtons).

The Bell X-1A made its first flight 14 February 1953 with Bell test pilot Jean Ziegler in the cockpit. It reached its highest speed, Mach 2.44 on Flight 10. Its highest altitude was 90,440 feet (27,566 meters) on its 24th flight. On 8 August 1955, while still on board its B-50 drop ship, the X-1A suffered an external explosion. The rocketplane was jettisoned and destroyed when it hit the desert floor.

© 2016, Bryan R. Swopes

12 December 1947

Boeing XB-47 Stratojet rollout at Seattle, Washington, 12 December 1947. (U.S. Air Force 061024-F-1234S-065)

12 December 1947: The Boeing XB-47 Stratojet was rolled out of its hangar for public display.

The Arizona Republic reported:

Boeing’s New Jet Bomber Is The Size of Superfort

     SEATTLE, Sept. 13—(AP) A new jet-propelled bomber, the size of a B-29 Superfortress and with sharply sweptback wings and tail surfaces will begin ground and taxiing tests soon.

     Whether the new Boeing XB-47 Stratojet, rolled out of its construction hangar for the first public display yesterday will near or attain speeds of jet fighter planes remains undisclosed. The army air forces and Boeing, showing the plane, made no mention of its expected speed, but streamlining was carried to the extreme.

     The sharply turned-back or inverted wings and tail surfaces appeared to be notable innovations in plane design. Four general Electric-built jet engines are mounted in pairs under the inboard sections of the wing, with another out near each wing tip.

     The wings are also “exceptionally thin,” a Boeing spokesman said, and the plane has a tandem type landing gear with small outrigger wheels. What was also described as 18 jet-assisted takeoff units studded the rear fuselage for added power. There was only one bomb bay, compared with the two on a B-29, but it was longer than those on a Superfortress.

     Compared with the B-29’s wing span of 141 feet and length of 99 feet, the XB-47’s wing span is approximately 116 feet and its length about 108 feet.

     Robert Robbins and Scott Osler, chosen as the plane’s test pilots a year ago, said it would be probably a month or more before it could take to the air. They said its initial flights would be “admittedly hazardous” but believe it will be an “outstanding airplane.”

     Blueprints used in planning the ship provides for two rocket motors near the tail, to be used for emergency bursts of power, experts said. It would be the first combat-type aircraft with such equipment.

     The Boeing company has turned out three other new-type planes this year. They were the new B-50, the successor to the Superfortress, the first 80-passenger Stratocruiser and the XL-15 Liaison plane, being built at the Wichita, Kan., plant.

     Several other jet bombers are under experiment for the army and the Consolidated Vultee XB-46, powered with four engine, and the North American XB-45, also a four-engine plane, have undergone trial flights.

The Arizona Republic, Vol. 58, No. 116, 14 September 1947, Page 12, Columns 1–3

Boeing XB-47 Stratojet 46-065. (U.S. Air Force 061024-F-1234S-004)

The first prototype, 46-065, was powered by six General Electric J35-GE-7 axial flow turbojet engines in four pods mounted on pylons below the wings. The J35 was a single-spool, axial-flow turbojet engine with an 11-stage compressor and single-stage turbine. The J35-GE-7 was rated at 3,750 pounds of thrust (16.68 kilonewtons) at 7,700 r.p.m. (static thrust, Sea Level). The engine was 14 feet, 0.0 inches (4.267 meters) long, 3 feet, 4.0 inches (1.016 meters) in diameter and weighed 2,400 pounds (1,089 kilograms). (The second prototype, 46-066, was completed with J47 engines. 46-065 was later retrofitted with these engines.)

The XB-47 prototype had a maximum speed of 502 knots (578 miles per hour/930 kilometers per hour/0.80 Mach) at 15,000 feet (4,572 meters). The combat speed was 462 knots (532 miles per hour/856 kilometers per hour/0.70 Mach) at 35,000 feet (10,668 meters). The prototype’s empty weight was 74,623 pounds (33,848 kilograms), while its maximum takeoff weight was 162,500 pounds (73,709 kilograms). It required a ground run of 11,900 feet (3,627 meters), or 4,800 feet (1,463 meters) with JATO assist. The bomber could climb at a rate of 3,650 feet per minute (18.5 meters per second) at Sea Level, at combat weight and maximum power. The service ceiling was 37,500 feet (11,430 meters). The XB-47 carried 9,957 gallons (37,691 liters) of fuel. The combat radius was 1,175 nautical miles (1,352 statute miles/2,176 kilometers) with a 10,000 pound (4,536 kilogram) bomb load.

Planned armament (though the XB-47s were delivered without it) consisted of two .50-caliber machine guns in a tail turret, with 1,200 rounds of ammunition, and 10,000 pounds (4,536 kilograms) of bombs.

Boeing XB-47 Stratojet 46-065, the first of two prototypes, on the ramp at Boeing Field, Seattle, 1 December 1947. (U.S. Air Force)

The Stratojet was one of the most influential aircraft designs of all time and its legacy can be seen in almost every jet airliner built since the 1950s: the swept wing with engines suspended on pylons, mounted forward of the leading edge.

2,032 B-47s were built by Boeing Wichita, Douglas Tulsa and Lockheed Marietta. They served the United States Air Force from 1951 to 1977.

The very last B-47 flight took place 18 June 1986 when B-47E-25-DT, serial number 52-166, was flown from the Naval Air Weapons Center China Lake to Castle Air Force Base to be placed on static display.

XB-47 45-065 stalled while landing at Larson Air Force Base, near Moses Lake, Washington, 18 August 1951. The crew of three escaped uninjured. The airplane was damaged beyond repair. The second prototype, XB-47 46-066, is in the collection of the Air Force Flight Test Museum, Edwards Air Force Base, California.

Boeing XB-47 Stratojet 46-065. (U.S. Air Force)

© 2023, Bryan R. Swopes