Tag Archives: Structural Failure

18 March 1939

Boeing Model 307 Stratoliner NX19901 taking of at Boeing Field, Seattle, Washington. (San Diego Air & Space Museum Archives)

18 March 1939: At 12:57 p.m., Pacific Standard Time (19:47 G.M.T.), the Boeing Model S-307 Stratoliner, NX19901, took off from Boeing Field, Seattle, Washington, on Test Flight No. 19. Julius Augustus Barr was the pilot in command.

The S-307, Boeing serial number 1994, was a prototype four-engine, pressurized commercial airliner. It had first flown on 31 December 1938, with Boeing’s Chief of Flight Test, Edmund Turney (“Eddie”) Allen, as first pilot (the Pilot in Command), and Julius Barr as his copilot. Allen had flown the first eighteen flights. “The performance of aircraft NX 19901 on flights prior to Test Flight No. 19 had either met or exceeded the manufacturer’s estimates.”

Julius Barr was employed by Boeing as a test pilot, 16 November 1938. Following Flight Test No. 15, Allen approved Barr to act as first pilot on the Model 307. He first served as the pilot in command of NX19901 on 21 January 1939. This was a taxi test, with the Stratoliner never leaving the ground. Barr first flew the airplane nearly two months later, 16 March 1939, with copilot Earl Alvin Ferguson. Barr made two more flights on 17 March. Harlan Hull, Chief Pilot of Transcontinental and Western Air, Inc., flew as copilot.

At takeoff on 18 March 1939, Barr had only 2 hours, 6 minutes as pilot in command of the Boeing 307; and 17 hours, 55 minutes as second in command. He had flown as an observer aboard NX19901 for 1 hour, 52 minutes.

There were ten persons on board the Stratoliner for Test Flight No. 19. In addition to Julius Barr as P.I.C., the designated copilot was Earl Ferguson. There were two alternate copilots, Harlan Hull and Benjamin J. Pearson, an assistant sales manager for Boeing. Ralph LaVenture Cram was first aerodynamcist, assisted by John Kylstra. William C. Doyle served as oscillograph operator, and Harry T. West, Jr., was the engineering officer. These were all Boeing employees. Pieter Guillonard, technical director of Koninklijke Luchtvaart Maatschappij N.V. (KLM Royal Dutch Airlines), acted as recorder and photographer, while Albert Gillis von Baumhauer, an engineer with the Luchtvaartdienst (the Dutch Aviation Authority), acted as an assistant aerodynamicist.

Albert G. von Baumhauer

Specialized test equipment had been installed at the copilot’s position. For this reason, Von Baumhauer, rather than the designated copilot, Ferguson, was in the copilot’s seat during this test flight. (Von Baumgartner held a Dutch private pilot certificate, issued 28 November 1931. Since that time, he had flown only 116 hours, and had no experience flying multi-engine aircraft. He was not qualified to act as copilot.)

Guillonard and Von Baumhauer had recommended a series of tests to be conducted on Test Flight No. 19, including observing the airplane’s behavior following an engine cut on takeoff with no rudder input; a series of side slips and stall tests. Von Baumhauer had emphasized “complete stalls” rather than initiating recovery when stall was detected.

After takeoff, NX19901 climbed to 10,000 feet (3,048 meters) and at 140 miles per hour (225 kilometers per hour) a series of static longitudinal stability tests were performed. According to the test flight plan, side slips were to be investigated next.

Boeing 307 Stratoliner NX19901 with both propellers on right wing feathered. Note the rudder deflection. (Boeing)

     “At 1:12 P.M. (PST) a radio message was transmitted from NX 19901 to the Boeing Aircraft Company radio station located at Seattle, Washington, which message gave the position of the aircraft as being between Tacoma Washington and Mount Rainier at an altitude of 11,000 feet. Some two or three minutes later, while flying at a comparatively slow rate of speed in the vicinity of Alder, Washington, the aircraft stalled and began to spin in a nose down attitude. After completing two or three turns in the spin, during which power was applied, it recovered from the spin and began to dive. The aircraft partially recovered from the dive at an altitude of approximately 3,000 feet above sea level, during which recovery it began to disintegrate. Outboard sections of the left and right wings failed upward and broke entirely loose from the aircraft. Major portions of the vertical fin and portions of the rudder were carried away by wing wreckage. The outboard section of the left elevator separated from the stabilizer and both fell to the ground detached. The right horizontal tail surface, being held on by the fairing long the top surface and also by the elevator trim tab cables, remained with the fuselage. The No. 1 engine nacelle also broke loose from the aircraft and fell to the ground separately. The main body of the aircraft settled vertically and struck the ground in an almost level attitude both longitudinally and laterally at a point approximately 1,200 feet above sea level. Watches and clocks aboard the aircraft, which were broken by the force of the impact, indicated the time of the accident at approximately 1:17 p.m. (PST).”

AIR SAFETY BOARD REPORT, at Pages 34–35.

Diagram of probable flight path of NX19901 from Air Safety Board report.

All ten persons aboard were killed in the crash. The Stratoliner was destroyed. Because of the water ballast in the main fuel tanks, there was no post crash fire.

Wreckage of Boeing Model 307 Stratoliner NX19901, right rear quarter.
Wreckage of Boeing Model 307 Stratoliner NX19901, right front quarter.
Wreckage of Boeing Model 307 Stratoliner NX19901 near Alder, Washington
Wreckage of Boeing Model 307 Stratoliner NX19901 near Alder, Washington. (SDASM)
Wreckage of Boeing Model 307 Stratoliner NX19901, left front quarter.

During the crash investigation it was found that two B-17s had previously been spun. The first,

“. . . while flying with a gross load of about 42,000 pounds at an altitude of 14,000 feet, went into an inadvertent spin and made two complete turns before recovery was effected. During the pull-out from the ensuing dive, permanent distortion occurred in the structure of both wings, necessitating the installation of new wings on the aircraft.

     “In the second of these experiences, a similar ship was intentionally permitted to enter a spin following a complete stall. The controls were immediately reversed and the aircraft responded promptly, enabling the pilot to effect recovery after three-fourths of a turn in—

     “Evidence indicated that power was used in recovery from the spin in the case of NX 19901. It should be noted that in the two instances above described recovery from spin in similar aircraft was accomplished without the employment of power. In one of these cases, permanent distortion occurred in both wings.”

AIR SAFETY BOARD REPORT, at Pages 48 and 49.

Diagram of wing failure under load. (Air Safety Board Report)

PROBABLE CAUSE

     “Structural failure of the wings and horizontal tail surfaces due to the imposition of loads thereon in excess of those for which they were designed, the failure occurring in an abrupt pull-out from a dive following recovery from an inadvertent spin.”

Crash site diagram. (Air Safety Board Report)
Boeing Model 307 Stratoliner NX19901. The engine cowlings have been removed. The inboard right engine is running. The arrangement of passenger windows differs on the right and left side of the fuselage. (San Diego Air & Space Museum Archives)

The Boeing Model 307 was operated by a crew of five and could carry up to 33 passengers.  It was the first pressurized airliner and, because of its complexity, it was also the first airplane to include a flight engineer as a crew member. It could maintain a cabin pressure equivalent to 12,000 feet (3,650 meters) to a pressure altitude of 19,000 feet (5,791 meters).

The Model 307 used the wings, tail surfaces, engines and landing gear of the production B-17B Flying Fortress heavy bomber. The vertical fin and rudder were of the same design as the B-17B’s, though somewhat larger. The fuselage was circular in cross section to allow for pressurization. It was 74 feet, 4 inches (22.657 meters) long with a wingspan of 107 feet, 3 inches (32.690 meters) and overall height of 20 feet, 9½ inches (6.337 meters). The wings had 4½° dihedral and 3½° angle of incidence. The empty weight was 29,900 pounds (13,562.4 kilograms) and loaded weight was 45,000 pounds (20,411.7 kilograms).

The airliner was powered by four air-cooled, geared and supercharged, 1,823.129-cubic-inch-displacement (29.875 liter) Wright Cyclone 9 GR-1820-G102 9-cylinder radial engines with a compression ratio of 6.7:1, rated at 900 horsepower at 2,200 r.p.m., and 1,100 horsepower at 2,200 r.p.m. for takeoff. These drove three-bladed Hamilton-Standard Hydromatic propellers through a 0.6875:1 gear reduction in order to match the engine’s effective power range with the propellers. The GR-1820-G102 was 4 feet, 0.12 inches (1.222 meters) long, 4 feet, 7.10 inches (1.400 meters) in diameter, and weighed 1,275 pounds (578 kilograms).

The maximum speed of the Model 307 was 241 miles per hour (388 kilometers per hour) at 6,000 feet (1,828.8 meters). Cruise speed was 215 miles per hour (346 kilometers per hour) at 10,000 feet (3,048 meters). The service ceiling was 23,300 feet (7,101.8 meters).

Boeing Model 307 Stratoliner NX19901 with all engines running. (San Diego Air & Space Museum Archives)

Julius Augustus Barr was born at Normal, Illinois, 6 December 1905. He was the son of Oren Augustus Barr, a teacher and school superintendent, and Margaret M. Wallace Barr. He grew up in Pittsburg, Kansas. He attended the Kansas State Teachers College at Pittsburg in 1925. He was a member of the Alpha Gamma Tau (ΑΓΤ) fraternity, of which he was the treasurer.

Julius Augustus Barr

Barr enlisted in the Air Corps, United States Army, and was trained as a pilot at Brooks and Kelly Fields, San Antonio, Texas.

On 1 July 1928, Julius Barr married Miss Effie Hortense Roberson at Pittsburg, Kansas. They would have two children, Jo Anne Barr, and Gene Edward Barr.

In 1930, Barr and his family lived in Cheyenne, Wyoming. He flew as an air mail pilot, and was employed by Boeing Air Transport.

During the mid 1930s, the Barr family traveled to China, where he acted as manager of the airport at Hankow, and conducted flight training. He then flew as the personal pilot of Zhang Xueliang (also known as Chang Hseuh-Liang), (“The Young Marshal”). Zhang and another of other communist generals arrested Chiang Kai-Shek in the Xi’an Incident, December 1936. Chiang was released after two weeks, and Zhang placed under house arrest for the remainder of his life. (The others were executed.) Julius Barr then served as the personal pilot for Soong Mei-ling (“Madame Chiang”), and helped General Chang with the air defense of Shanghai during the Second Sino-Japanese War.

Barr and his family departed Hong Kong aboard S.S. Empress of Russia, which arrived at Victoria, British Columbia, Canada, 14 November 1938. He then went to work as a test pilot for Boeing two days later.

Julius Barr had flown a total of approximately 5,000 hours. Of these, 2,030 hours were in single-engine airplanes, 2,240 hours in twin-engine, and 765 hours in 3 engine.

Julius Augustus Barr was buried at the Mount Olive Cemetery, Pittsburg, Kansas.

© 2019, Bryan R. Swopes

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5 March 1966

British Overseas Airways Corporation's Boeing 707-436 Intercontinental, G-APFE. (BOAC)
British Overseas Airways Corporation’s Boeing 707-436 Intercontinental, G-APFE. (British Airways)

5 March 1966: British Overseas Airways Corporation Speedbird 911, an around-the-world flight, departed Tokyo-Haneda Airport (HND) at 1:58 p.m., enroute Hong Kong-Kai Tak (HKG), with 113 passengers and 11 crew members. The airliner was a Boeing 707-436 Intercontinental, serial number 17706, with British registration G-APFE. It was nearly six years old, having been delivered 29 April 1960, and had 19,523 hours on the airframe.

Shortly before takeoff, the flight crew requested a change from an IFR flight plan to VFR, with a course that would take the airliner near Mount Fujiyama. The 707 climbed to an altitude of 16,000 feet (4,875 meters) as it approached the mountain from the southwest. The weather was very clear. A weather station on Mount Fuji recorded wind speeds of 60–70 knots (111–130 kilometers per hour).

Speedbird 911, Boeing 707 G-APFE, in a flat spin. The tail section and engines are missing, the right wing is broken and the airplane is trailing fuel vapor from ruptured tanks.
Speedbird 911, Boeing 707 G-APFE, in a flat spin. The tail section and engines are missing, the right wing is broken and the airplane is trailing fuel vapor from ruptured tanks. (JSDF)

Flying upwind toward Fujiyama at 320–370 knots (592–685 kilometers per hour), Speedbird 911 encountered severe Clear Air Turbulence that resulted in a catastrophic structural failure of the airframe. The vertical fin attachment failed and as it fell away, struck the left horizontal stabilizer, breaking it off. Next, the ventral fin and all four engine pylons failed due to extreme side loads. The 707 went in to a flat spin, trailing fuel vapor from ruptured tanks. The entire tail section broke away, the right wing failed, and the nose section came off.

The 707 left a debris field  that was 10 miles (16 kilometers) long. Speedbird 911 crashed in a forest on the lower flanks of Mount Fujiyama at about the 3,500 foot (1,066 meter) level. The forward section crashed about 1,000 feet (300 meters) away from the main wreckage. All 124 persons aboard were killed.

Disintegrating Speedbird 911 trails fuel vapor as it falls toward Mount Fujiyama, 5 March 1966.
Disintegrating Speedbird 911 trails fuel vapor as it falls toward Mount Fujiyama, 5 March 1966. (JSDF)

PROBABLE CAUSE: “The aircraft suddenly encountered abnormally severe turbulence over Gotemba City which imposed a gust load considerably in excess of the design limit.”

The accident was photographed by the Japanese Self Defense Forces from the East Fuji Maneuver Area, located in the foothills of the volcano. A passenger aboard Speedbird 911 had been filming with an 8 mm movie camera. The camera and film were recovered from the wreckage and the film was developed as part of the investigation. The film showed that the aircraft had experienced severe turbulence immediately before the accident. (Investigators estimated the peak acceleration at 7.5 g.)

A U.S. Navy Douglas A-4 Skyhawk was sent to look for the accident site. When the fighter approached Mount Fujiyama, it also encountered severe turbulence, to the point that the pilot feared the small fighter would break up in flight. After returning to base, the A-4 was grounded for inspection. Its accelerometer indicated that it had experienced acceleration forces ranging from +9 Gs to -4 Gs.

Mount Fujiyama, an active stratovolcano, i steh tallest mountain in Japan, at 12,389 feet (3,776.24 meters). It i sapproximately 62 miles (100 kilometers) southwest of Tokyo on the island of Hinshu.
Mount Fujiyama, an active stratovolcano, is the tallest mountain in Japan, at 12,389 feet (3,776.24 meters). It is approximately 62 miles (100 kilometers) southwest of Tokyo on the island of Honshu. (Alpsdake)

G-APFE was a Boeing 707-436 International, built in 1960 for British Overseas Airways. At the time of the accident, it had made 6,744 flights and accumulated a total of 19,523:33 hours (TTAF).

The -436 was a stretched version of the original 707-120, but with Rolls-Royce Conway 508 bypass turbojet engines (now called turbofans) in place of the standard Pratt & Whitney JT3C-6 turbojet engines. 15 ordered by British Overseas Airways Corporation in 1956.

The fuselage and wings of the Intercontinental were lengthened, allowing an increased load and greater fuel capacity. It could carry 189 passengers and had a range 1,600 miles further than the -120. Transoceanic flights without an intermediate fuel stop were possible.

Initially, British aviation authorities refused to certify the -436 because of low-speed handling concerns. Boeing increased the height of the vertical fin 40 inches and added a ventral fin. These modifications became standard on all future 707s and were retro-fitted to those already manufactured.

The Boeing 707-420 series airliners were 152 feet, 11 inches (46.609 meters) long, with a wingspan of 142 feet, 5 inches (43.409 meters) and overall height 42 feet, 2 inches (12.852 meters) at its operating empty weight. The leading edges of the wings and tail surfaces are swept 35°. The fuselage has a maximum diameter of 12 feet, 8.0 inches (3.759 meters). The 707 International has a typical empty weight of 142,600 pounds (64,682 kilograms), and a maximum takeoff weight (MTOW) of 312,000 pounds (141,700 kilograms). The usable fuel capacity is 23,820 gallons (90,169 liters).

British Overseas Airways corporation Boeing 707-436 International G-APFE photographed at Idlewild Airport, 27 June 1962. (Jon Proctor)

All 707-series aircraft are powered by four jet engines installed in nacelles below and forward of the wings on pylons. The -420 Internationals were powered by Rolls-Royce Conway Mk. 508 engines. The Rolls-Royce Conway (R.Co.12) is a two-spool, axial-flow, low-bypass turbofan engine. The engine has a 7-stage low- and 9-stage high-pressure compressor section, 12 interconnected combustion liners, with a single-stage high- and 2-stage low-pressure turbine. The Mk. 508 has a Maximum Continuous Power rating of 14,625 pounds of thrust (65.055 Kilonewtons), and 17,500 pounds of thrust (77.844 Kilonewtons) at 9,990 r.p.m., for Takeoff. The engine is 3 feet, 6.0 inches (1.067 meters) in diameter, 11 feet, 4.0 inches (3.454 meters) long, and weighs 4,542 pounds (2,060 kilograms).

The -420 series had a maximum cruise speed of 593 miles per hour 954 kilometers per hour) at 30,000 feet (9,144 meters)—0.87 Mach; and economical cruise speed of 550 miles per hour (885 kilometers per hour) at 35,000 feet (10668 meters).

Boeing built 1,010 Model 707 airplanes between 1957 and 1979. Of these, 37 were the 707-420 Intercontinental variant.

A British Overseas Airways Corporation Boeing 707-420-series International airliner, similar in appearance to G-APFE. (Travell Update)

© 2019, Bryan R. Swopes

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24 January 1963

Boeing B-52C-40-BO Stratofortress 53-400, the same type as 53-406, which crashed on Elephant Mountain, 24 January 1963. (San Diego Air & Space Museum)

24 January 1963: A Boeing B-52C-40-BO Stratofortress, 53-0406, call sign “Frosh 10,” of the 99th Bombardment Wing, Heavy, was conducting a low-altitude training flight using terrain-following radar. Eight crewmen were aboard. Flying at or below 500 feet (152 meters) above ground level (AGL) and at 280 knots (322 miles per hour, 519 kilometers per hour) the bomber encountered wind gusts of up to 40 knots (21 meters per second).

As the turbulence became severe, the aircraft commander, Lieutenant Colonel Dante E. Bulli, began a climb to avoid it. At approximately 2:52 p.m., EST, however, the vertical fin attachment failed and the B-52 began rolling to the right and pitching down. Colonel Bulli, unable to control the airplane, ordered the crew to abandon the bomber.

B-52C 53-0406 crashed into the west side of Elephant Mountain, a 3,774 foot (1,150 meters) forest-covered mountain, 6 miles (10 kilometers) from Greenville, Maine. Only three men, Colonel Bulli, co-pilot Major Robert J. Morrison and navigator Captain Gerald J. Adler, were able to get out of the B-52, but Major Morrison died when he hit a tree. Lieutenant Colonel Joe R. Simpson, Jr., Major William W. Gabriel, Major Robert J. Hill, Jr., Captain Herbert L. Hansen, Captain Charles G. Leuchter and Technical Sergeant Michael F. O’Keefe were also killed.

Large sections of Frosh 10 are still on Elephant Mountain. The crash site is a popular hiking destination.

The Boeing B-52 Stratofortress had been designed as a very high altitude penetration bomber, but changes in Soviet defensive systems led to a change to very low altitude flight as a means of evading radar. This was subjecting the airframes to unexpected stresses. Several crashes resulted from structural failures during turbulence.

Less than one year later, Boeing was conducting flight tests of the B-52 in turbulence, using a highly-instrumented B-52H. That airplane also lost its vertical fin when it encountered severe turbulence in Colorado. The Boeing test pilots aboard were able to save the bomber and landed it six hours later.

Boeing B-52H-170-BW Stratofortress 61-023, "Ten-Twenty-Three", after losing the vertical fin, 10 January 1964. (Boeing)
Boeing B-52H-170-BW Stratofortress 61-023, “Ten-Twenty-Three”, after losing the vertical fin, 10 January 1964. (Boeing)
Colonel Dante E. Bulli, United States Air Force

Dante E. Bulli was born at Cherry, Illinois, 17 July 1922, the second child of Italian immigrants Giovanni Bulli, a salesman, and Anna Gareto Bulli.  He attended Hall High School before working on the aircraft assembly lines of the Lockheed Aircraft Company in California.

Bulli enlisted as an aviation cadet in the U.S. Army Air Corps in 1942. He was commissioned as a second lieutenant, Army of the United States, 5 December 1943, and promoted to first lieutenant, 5 December 1946.

In 1947 Lieutenant Bulli married Miss Evelyn Lewis, also from Cherry, Illinois.

“Dan” Bulli was a combat veteran of World War II, the Korean War and the Vietnam War. He flew B-24 Liberators, the B-29 Superfortress and B-52 Stratofortress. He retired from the Air Force in 1974.

Colonel Dante E. Bulli died at Omaha, Nebraska, 30 December 2016, at the age of 94 years.

© 2018, Bryan R. Swopes

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3 June 1973

Tupolev Tu-144S CCCP-77102 at the Paris Air Show. © Aris Pappas

3 June 1973: While maneuvering at low altitude at the Paris Air Show, the first production Tupolev Tu-144S, CCCP-77102, Aeroflot’s new Mach 2+ supersonic airliner, broke apart in midair and crashed into a residential area. All six crew members and eight people on the ground died. Another 25 were injured.

The Tu-144 was built by Tupolev OKB at the Voronezh Aviation Plant (VASO), Pridacha Airport, Voronezh. It was a large delta-winged aircraft with a “droop” nose for improved low speed cockpit visibility and retractable canards mounted high on the fuselage behind the cockpit. It was flown by a crew of 3 and was designed to carry up to 140 passengers.

The airliner was 65.50 meters (214.895 feet) long, with a wingspan of 28.80 meters (94.488 feet). The tip of the vertical fin was 10.50 meters (34.449 feet) high. Empty weight was 85,000 kilograms (187,393 pounds) and the maximum takeoff weight was 180,000 kilograms (396,832 pounds).

The Tu-144S was powered by four Kuznetsov NK-144F afterburning turbofan engines, producing 45,000 pounds of thrust, each.

The airliner’s cruise speed was Mach 1.88 (2,000 kilometers per hour/1,243 miles per hour) with a maximum speed of Mach 2.15 (2,285 kilometers per hour/1,420 miles per hour). The service ceiling was 20,000 meters (65,617 feet).

The cause of the accident is not known, other than the obvious structural failure, but there is speculation that the Tu-144 was trying to avoid another airplane. You Tube has several video clips of the accident. This one, beginning at 1:10, has the best visuals of the inflight break up:

© 2016, Bryan R. Swopes

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