Tag Archives: Eddie Allen

18 February 1943, 12:26 p.m., Pacific War Time

February 18, 2024Aviation1, 41-0003, 42-24579, Aircraft Accident, B-29-40-BW, Boeing Aircraft Company, Boeing B-29 Superfortress, Boeing Field, Boeing XB-29, Eddie Allen, Edmund Turney Allen, Frye Meat Packing Plant, PrototypeBryan Swopes

The second prototype Boeing XB-29 Superfortress, 41-0003, takes off from Boeing Field, 12:09 p.m., 18 February 1943. (Boeing)

18 February 1943: At 12:09 p.m., Boeing Aircraft Company Chief Test Pilot Edmund Turney (“Eddie”) Allen took off from Boeing Field, Seattle, Washington, in the Number 2 prototype XB-29 Superfortress long-range heavy bomber, serial number 41-0003. Allen’s co-pilot was engineering test pilot Robert R. Dansfield. The rest of the XB-29 flight crew were Charles Edmund Blaine, flight test engineer; Fritz Mohn, senior inspector; Vincent W. North, aerodynamicist; Harry William Ralston, radio operator; Barclay J. Henshaw, flight test analyst; Thomas R. Lankford, engineer; Robert Willis Maxfield, flight test engineer; Raymond Louis Basel, flight test engineer; Edward I. Wersebe, flight test engineer.

Edmund T. ("Eddie") Allen. (San Diego Air and Space Museum Archive) — Edmund Turney Allen. (San Diego Air & Space Museum Archive)

41-0003 had first flown on 30 December 1942, piloted by Allen. During that flight, the prototype bomber suffered a major engine fire and Eddie Allen’s performance in returning the airplane to the airport later earned him the U.S. Army’s Air Medal, awarded on the specific orders of President Harry S. Truman.

Problems with the XB-29s’ Wright R-3350-13 engines had caused major delays in the B-29 testing program. The Number 2 aircraft had its engines replaced with those from the first XB-29, 41-0002. By 18 February, 41-0003 had made only eight flights, with a total flight time of 7 hours, 27 minutes.

The ninth test flight of 41-0003 was planned to test the climb performance to 25,000 feet (7,620 meters) and to collect engine cooling data.

At 12:17 p.m., 41-0003 was climbing through 5,000 feet (1,524 meters) when the #1 engine (the outboard engine on the left wing) caught fire. The engine was shut down and CO2 fire extinguishers were activated. Eddie Allen began a descent and turned back toward Boeing Field.

The wind was out of the south at 5 miles per hour (2.24 meters per second) so it was decided to land on Runway 13, the southeast/northwest runway. At 12:24, radio operator Harry Ralston reported that the XB-29 was 4 miles (6.4 kilometers) northeast of the field at 1,200 feet (366 meters).

The airplane was in the landing pattern turning from the downwind leg to the base leg when at 12:25 an explosion occurred. Ralston was heard to say, “Allen, better get this thing down in a hurry. The wing spar is burning badly.”

In order to save weight, various parts of the Wright R-3350 engine were made of magnesium, a flammable metal which burned at a very high temperature. With an engine on fire, the bomber’s wing structure was extremely vulnerable.

The prototype bomber was now shedding parts and left a trail behind it on the ground. The fire was now burning inside the fuselage. Three crew members bailed out but the altitude was too low and they were killed.

At 12:26 p.m., Boeing XB-29 41-0003 crashed into the Frye Meat Packing Plant, south of downtown Seattle, and exploded. Nearly 5,000 gallons (18,927 liters) of gasoline started a massive fire. The 8 men still aboard the prototype bomber were killed, as were 20 employees inside the building. A firefighter who responded was also killed.

Frye packing plant fire, 18 February 1943. (Seattle Post-Intelligencer) — The Frye packing plant on fire, 18 February 1943. (Seattle Post-Intelligencer)

Three XB-29 prototypes were built. The XB-29 was 98 feet, 2 inches (29.896 meters) long with a wing span of 141 feet, 3 inches (43.053 meters), and 27 feet, 9 inches (8.458 meters) high to the top of its vertical fin. The prototype bomber had a gross weight of 105,000 pounds (47,627.2 kilograms).

Boeing XB-29-BO, 41-002, the first XB-29 built. (U.S. Air Force)

The XB-29 was powered by four 3,347.662-cubic-inch-displacement (54.858 liter) air-cooled, supercharged, Wright Aeronautical Division Cyclone 18 670C18H1 (R-3350-13) two-row 18-cylinder radial engines (also known as the Duplex-Cyclone) with a compression ratio of 6.85:1. The R-3350-13 had a Normal Power rating of 2,000 horsepower at 2,400 r.p.m., and 2,200 horsepower at 2,800 r.p.m. for takeoff, using 100 octane aviation gasoline. The engines turned 17-foot-diameter (5.182 meters) three-bladed Hamilton Standard Hydromatic constant-speed propellers through a 0.35:1 gear reduction. The R-3350-13 was 76.26 inches (1.937 meters) long, 55.78 inches (1.417 meters) in diameter, and weighed 2,668 pounds (1,210 kilograms).

The XB-29 had a maximum speed of 368 miles per hour (592 kilometers per hour) and cruised at 255 miles per hour (410 kilometers per hour). Its service ceiling was 32,100 feet (9,784 meters). The airplane was designed to carry 20,000 pounds (9,072 kilograms) of bombs.

The B-29 Superfortress was the most technologically advanced—and complex—aircraft of the War. It required the manufacturing capabilities of the entire nation to produce. Over 1,400,000 engineering man-hours had been required to design the prototypes. It would be manufactured by Boeing at Seattle and Renton, Washington and at Wichita, Kansas; by Glenn L. Martin Company at Omaha, Nebraska; and by Bell Aircraft Corporation, Atlanta, Georgia.

There were three XB-29 prototypes; 14 YB-29 pre-production test aircraft; 2,513 B-29; 1,119 B-29A; and 311 B-29B Superfortress aircraft. The bomber served during World War II and the Korean War and continued in active U.S. service until 1960.

The employees of the Boeing plant at Wichita, Kansas donated the money to build a B-29 to be named in honor of Eddie Allen. B-29-40-BW 42-24579 flew 24 combat missions. On its final mission over Tokyo, Japan, the Eddie Allen was so badly damaged that, though it was able to reach its base on the island of Tinian, it never flew again.

Boeing B-29 Superfortress "Eddie Allen." (U.S. Air Force) — Boeing Wichita-built B-29-40-BW Superfortress 42-24579, “Eddie Allen,” of the 45th Bombardment Squadron (Very Heavy), 40th Bombardment Group (Very Heavy), XX Bomber Command, circa 1944. (U.S. Air Force)

Boeing's acknoledgemnt of the sacrifice of its flight test crew, 18 February 1943, — Boeing’s acknowledgement of the sacrifice of its flight test crew, 18 February 1943, from the annual report to the shareholders.

9 January 1943

January 9, 2024Aviation43-10309, c/n 049-1961, Eddie Allen, Kelly Johnson, Lockheed Aircraft Company, Lockheed L-049 Constellation, Lockheed L-1049 Super Constellation, Lockheed Model 49-46-10, Lockheed PO-1W Warning Star, Lockheed XC-69 Constellation, Milo Garrett Burcham, Muroc Army Airfield, NX25600, NX6700, PrototypeBryan Swopes

Lockheed L-049 Constellation NX25600 in flight. (San Diego Air and Space Museum Archive) — Lockheed XC-69 Constellation 43-10309 (L-049 NX25600) in flight. (San Diego Air & Space Museum Archive)

9 January 1943: At the insistence of the United States Army Air Forces, Boeing’s Chief Test Pilot, Eddie Allen, made the first flight of the Lockheed L-049 Constellation prototype, NX25600, from Lockheed Air Terminal at Burbank, California, to Muroc Army Airfield (today known as Edwards Air Force Base). Lockheed’s Chief Test Pilot, Milo G. Burcham, was the co-pilot.

Lockheed XC-69 Constellation 43-10309 (L-049 NX25600) in flight, right front, from below. (San Diego Air & Space Museum Archive, Catalog # 00068294) — Lockheed XC-69 Constellation 43-10309 (L-049 NX25600) in flight. (San Diego Air & Space Museum Archive)

Also on board were Lockheed’s chief research engineer, Clarence L. (“Kelly”) Johnson; Rudy Thoren, Johnson’s assistant; and Dick Stanton, chief mechanic.

The Lockheed Constellation was designed by a team led by Chief Engineer Hall Livingstone Hibbard, left, and Chief Research Engineer Clarence Leonard “Kelly” Johnson. (Lockheed)

When the flight ended after 58 minutes, Allen said, “This machine works so well that you don’t need me anymore!” With that, Allen returned to Seattle.

The Los Angeles Times reported:

SUPER TRANSPORT PLANE IN DEBUT

Lockheed’s Air Marvel Makes First Flight; Believed to Be World’s Largest and Fastest; Built Like Fighter, Can Outspeed Jap Zero

BY MARVIN MILES

Into the winter sky yesterday swept a brilliant new star—Lockheed super-transport Constellation.

First of a galaxy to come, the four-engine colossus sped down the long east-west runway at Lockheed Air Terminal, skipped nimbly off the concrete and boomed upward with the surging roar of 8000 unleashed horses.

A few breath-taking seconds’ full throttle had written a matter-of-fact climax to two years of secret development that evolved a 60-passenger transport faster than a Jap Zero fighter.

There were no fanfares, no speeches—simply an unvarnished war production takeoff, emphasizing as nothing else could the grim driving need for huge work planes to carry the battle swiftly to the ends of the earth.

Yet it was the first significant aviation event of 1943.

Lockheed XC-69 Constellation 43-30109 during its first flight, 9 January 1943. (Lockheed Martin Aeronautics Company/world war photos) — Lockheed XC-69 Constellation 43-30109 during its first flight, 9 January 1943. (Lockheed Martin Aeronautics Company)

Built along the slim, graceful lines of a fighter the craft is faster than any four-engine bomber now in service. It can cross the continent in less than 9 hours,fly to Honolulu in 12. Even at half power its cruising speed is approximately 100 miles per hour faster than that of a standard airliner!

Within its supercharged cabin, air-density will remain at the 8000-foot level when the Constellation is cruising at “over-the-weather” altitudes up to 35,000 feet. So great is its power that the monster can maintain 25,000 feet on three engines, 16,500 on two.

As for economy of operation, the new sky queen can fly her full load hour after hour using but one gallon of gasoline per mile.

Lockheed XC-69 Constellation 43-10309 (L-049 NX25600) at Lockheed Air Terminal, Burbank, California, with engines running. Looking west-northwest across the San Fernando Valley. (San Diego Air & Space Museum Archive, Catalog # 00013539) — Lockheed XC-69 Constellation 43-10309 (L-049 NX25600) at Lockheed Air Terminal, with engines running. Looking west-northwest across the San Fernando Valley. (San Diego Air & Space Museum Archive)

ONE TAXI TEST

At the controls when the super-transport lifted its tricycle gear in flight were Eddie Allen, Army pilot and veteran four-engine flyer, and Milo Burcham, Lockheed test pilot noted for his substratosphere testing of the P-38. Also in the ship were C.L. (Kelly) Johnson, chief research engineer for the aircraft company; Rudy Thoren, Johnson’s assistant, and Dick Stanton, chief mechanic.

Johnson, Clarence L., "Kelly," with Milo G. Burcham, standing to left front of Lockheed XC-69 Constellation (L-049) NX25600, at Lockheed Air Terminal, Burbank, California. (Lockheed Martin Aeronautics Company photograph Z-5573) — Chief Research Engineer Clarence L. “Kelly” Johnson (left) and Chief Engineering Test Pilot Milo G. Burcham, with the XC-69 Constellation. (Lockheed Martin Aeronautics Company)

There was but one taxi test yesterday, highlighted by a brief blaze in one of the four engines following a backfire as the ship turned to roll back to the head of the runway.

The fire was doused quickly and the Constellation stood ready for her maiden flight, he nose into a gentle breeze, the focal point of hundreds of eyes of workers, Army guards and officials watched expectantly.

Each engine “revved up”in turn, sending deep-throated echoes over the sun-drenched terminal.

Then the four black propellers whirled as one.

The Constellation shot forward, the wind in her teeth, a hurtling, bellowing land monster—until her propellers plucked her from the earth in an incredibly short span of runway and sent her thundering triumphantly toward the sun.

GLIDES BACK EASILY

In a moment she had almost vanished, only to bank in a wide turn and drone back over the terminal twice before leading her covey of lesser following craft off toward the desert to the Army airport at Muroc Dry Lake where she landed gracefully an hour later.

Prototype Lockheed Constellation at Muroc Dry Lake, 1942. (Unattributed) — Prototype Lockheed L-049 Constellation NX25600 at Muroc Dry Lake on the high desert of southern California, 9 January 1943. (San Diego Air & Space Museum Archive)

Shortly before dusk the giant craft returned to the Burbank terminal, slipped down the long “landing groove” of air and settled easily to the runway.

Her debut was over.

Today she will begin the exhaustive test flights to determine her performance before she is turned over to T.W.A. and the Army for the grueling business of war. . . .

—Los Angeles Times, Vol. LXII, Sunday morning, 10 January 1943, Page 1, Columns 1 and 2; Page 2, Columns 2 and 3. The article continues in Column 4. (The photographs are not a part of the original article.)

The prototype Lockheed XC-69, 43-10309 (NX25600), landing at Lockheed Air Terminal, Burbank, California, 1943. (Lockheed Martin Aeronautics Company)

The Lockheed Model 49-46-10, company serial number 049-1961, was designated XC-69 by the U.S. Army Air Forces and assigned serial number 43-10309.

The Constellation was operated by a flight crew of four: two pilots, a navigator and a flight engineer. It could carry up to 81 passengers. The airplane was 95 feet, 1 3⁄16 inches (28.986 meters) long with a wingspan of 123 feet, 0 inches (37.490 meters), and overall height of 23 feet, 7⅞ inches (7.210 meters). It had an empty weight of 49,392 pounds (22,403.8 kilograms) and maximum takeoff weight of 86,250 pounds (39,122.3 kilograms).

The XC-69 was powered by four air-cooled, supercharged, 3,347.662-cubic-inch-displacement (54.858 liter), Wright Aeronautical Division Cyclone 18 745C18BA2 engines. Also known as the Duplex Cyclone, these were a two-row, 18-cylinder radial engines with a compression ratio of 6.5:1, which required 100/130-octane aviation gasoline. They were rated at 2,000 horsepower at 2,400 r.p.m., or 2,200 horsepower at 2,800 r.p.m. for takeoff, (five minute limit). The 745C18BA2 was 6 feet, 4.26 inches (1.937 meters) long, 4 feet, 7.78 inches (1.417 meters) in diameter and weighed 2,595 pounds (1,177 kilograms). The engines drove 15 foot, 2 inch (4.623 meter) diameter, three-bladed Hamilton Standard Hydromatic 43E60 constant-speed propellers through a 0.4375:1 gear reduction.

The L-049 had a cruise speed of 313 miles per hour (504 kilometers per hour) and a range of 3,995 miles (6,429 kilometers). Its service ceiling was 25,300 feet (7,711 meters).

In this photograph of the Lockheed XC-69 prototype, the civil experimental registration numbers, NX25600 are visible under the left wing. (Unattributed) — In this photograph of the Lockheed XC-69 prototype at Lockheed Air Terminal, the civil experimental registration numbers, NX25600, are visible on the rudder and under the left wing. Looking northeast, the Verdugo Mountains of Southern California are in the background. (San Diego Air & Space Museum Archive)

This is a rare color photograph of the prototype Lockheed XC-69 Constellation, 43-10309, (L-049 NX-25600) with a Lockheed UC-101, 42-94148 (ex-Vega 5C NC14236) at Lockheed Air Terminal, Burbank California. This picture represents 15 years of technological advancement. (Lockheed Martin Aeronautics Company)

The prototype XC-69 was later re-engined with Pratt & Whitney Double Wasp 2SC14-G (R-2800-83) engines and designated XC-69E. These had a Normal rating of 1,700 horsepower at 2,600 r.p.m., to 7,300 feet (2,225 meters), 1,500 horsepower at 17,500 feet (5,334 meters), and 2,100 horsepower at 2,800 r.p.m. for Takeoff.

Lockheed XC-69 Constellation 43-10309. (Lockheed Martin Aeronautics Company/Burbank Public Library pub00017) — Lockheed XC-69 Constellation 43-10309. (Lockheed Martin Aeronautics Company)

Lockheed XC-69 Constellation 43-10309. (Lockheed Martin Aeronautics Company/Burbank Public Library pub00014) — Lockheed XC-69 Constellation 43-10309. (Lockheed Martin Aeronautics Company)

After the war, the Constellation prototype was sold to Howard Hughes’ Hughes Aircraft Company for $20,000 and registered as NX67900. In May 1950, Lockheed bought the prototype back from Hughes for $100,000 and it was again registered as NC25600. It had accumulated just 404 flight hours up to this time.

The prototype Lockheed XC-69 Constellation, 43-10309, is parked at Howard Hughes’ Culver City airport. In the foreground is the Hughes XF-11, 44-70155. Photographed 7 July 1946. (University of Nevada, Las Vegas Libraries)

Lockheed L-1049 Super Constellation prototype, NX6700, ex-L-049 NX25600. (Lockheed Martin) — The prototype Lockheed L-1049 Super Constellation NX25600 (XC-69 43-10309), flying above an inversion layer. The San Gabriel Mountains of Southern California are in the background. (Lockheed Martin Aeronautics Company)

The prototype Lockheed L-1049 Super Constellation NX25600 (XC-69 43-10309), flying above an inversion layer. The San Gabriel Mountains of Southern California are in the background. (Lockheed Martin Aeronautics Company)

31 December 1938

December 31, 2023AviationAirliner, Boeing Aircraft Company, Boeing C-75 Stratoliner, Boeing Model 307 Stratoliner, Eddie Allen, Edmund Turney Allen, First Flight, NC19903, NX19901, s/n 1994, Steven F. Udvar-Hazy Center, Test Pilot, Wright Aeronautical Corporation, Wright Cyclone 9 GR-1820-G102Bryan Swopes

Boeing Model 307 Stratoliner with all engines running, Boeing Field, Seattle, Washington, circa 1939. (San Diego Air & Space Museum Archives, Catalog #: 00061667) — Boeing Model 307 Stratoliner with all engines running, Boeing Field, Seattle, Washington, circa 1939. (San Diego Air & Space Museum Archives)

31 December 1938: Boeing Model 307 Stratoliner NX19901 made its first flight at Boeing Field, Seattle, Washington. The test pilot was Eddie Allen, with co-pilot Julius A. Barr.

The Model 307 was a four-engine commercial airliner that used the wings, tail surfaces, engines and landing gear of the production B-17B Flying Fortress heavy bomber. The fuselage was circular in cross section to allow for pressurization. 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.

Boeing 307 Stratoliner NX19901 with both propellers on right wing feathered. (Boeing)

The Associated Press news agency reported:

Test Of Big Craft Begins

SEATTLE, Dec. 31—(AP)—The world’s first plane, designed for flying in the sub-stratosphere, the new Boeing “Stratoliner”, performed “admirably” in a 42-minute first test flight in the rain today.

The big ship, with a wingspread of 107 feet, three inches, climbed to 4,000 feet, the ceiling, and cruised between here, Tacoma and Everett. Speed was held down to 175 miles an hour.

“The control and stability and the way it handled were very nice,” Edmund T. Allen, pilot, said. “She performed admirably.”

The 33-passenger ship was built to fly at altitudes of 20,000 feet.

No more tests are planned until next week. The supercharging equipment for high altitude flights will be installed later.

—Arizona Republic, Vol. IL, No. 228, Sunday, 1 January 1939, Page 2, Column 4

Boeing Model 307 Stratoliner NX19901 taking of at Boeing Field, Seattle, Washington. (San Diego Air & Space Museum Archive Catalog # 01 00091290) — Boeing Model 307 Stratoliner NX19901 taking of at Boeing Field, Seattle, Washington. (San Diego Air & Space Museum Archives)

Giant ‘Stratoliner” Wheeled From Factory, On First Flight

SEATTLE, Dec. 31—(AP)—The newest thing in aviation—a giant, 33-passenger stratoliner named and built by Boeing Aircraft Company—met enthusiastic approval of its test pilot today after preliminary test runs.

Scarcely 24 hours after it left the factory, the newest Boeing plane tested its wings yesterday. Test Pilot Edmund T. Allen taxied the plane along the ground, gunned it a bit and flew it in the air a short time at an altitude from 15 to 30 feet.

Allen did not class the short hop as the ship’s maiden flight, which he said formally remained to be made, probably within a week.

He said the big ship, minus general airplane characteristics, would not require any super-airports as the demonstration showed it would be able to take off and land at any ordinary-sized field.

The stratoliner has four 1,100-horsepower motors which will enable it to cruise at an altitude of four miles at a speed of more than four miles a minute.

Most unusual feature of the silver colored plane is the shape of the cabin, which bears a distinct resemblance to a metal dirigible. The cabin is circular throughout its length of 74 feet, four inches.

The shape was adopted because of the necessity of sealing the cabin so passengers can enjoy low-level atmospheric conditions while soaring at high altitudes. The door, instead of opening outwards, is opened from the inside, so that the higher air pressure in the cabin will keep it sealed.

The stratoliner’s wings compare in design with the Boeing flying fortresses but because of the larger cabin, the wing span is 107 feet, three inches, greater than that of the bombers, the new plane’s height is 17 feet, three inches.

“Outside of scientific and engineering circles the substratosphere has been generally regarded as something far away and mystical, but now it is being brought ‘down to earth,’ C. L. Engtvedt, president of Boeing said.

“The stratoliner will fly below the true stratosphere, but above the heavy air belt that brews surface weather conditions. Here we get most of the benefits of the stratosphere without getting into complex problems of flight in the extremely rare atmosphere and low temperature of the true stratosphere,” he said.

Engtvedt predicted stratosphere type planes would lend a tremendous stimulus to the growth of air transportation.

The first three stratoliners are being built for pan-American airways. Six more are in the course of construction for buyers whose identity has not been announced.

—Eugene Register-Guard, Vol. 95, No. 1, January 1, 1939 at Page 3, Columns 5 and 6

On March 18, 1939, during its 19th test flight, the Stratoliner went into a spin, then a dive. It suffered structural failure of the wings and horizontal stabilizer when the flight crew attempted to recover. NX19901 was destroyed and all ten persons aboard were killed.

Boeing Model 307 Stratoliner NX19901. (San Diego Air & Space Museum Archives, Catalog #: 00061659) — Boeing Model 307 Stratoliner NX19901. (San Diego Air & Space Museum Archives)

Boeing 307 Stratoliner NX19901, right rear quarter. (San Diego Air & Space Museum Archives, Catalog #:01_00091289)

Boeing Model 307 Stratoliner NX19901. (San Diego Air and Space Museum Archive, Catalog # 01 00091288) — 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 33 passengers. 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 cockpit of a Boeing 307 Stratoliner, photographed 12 March 1940. (Boeing)

Cutaway illustration of a Boeing Model 307 Stratoliner. (NASM SI-89-4024)

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).

Boeing Model 307 Stratoliners under construction. (SDASM Archives Catalog #: 00061653)

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 and Space Museum Archive, Catalog # 01 00091291) — Boeing Model 307 Stratoliner NX19901 with all engines running. (San Diego Air & Space Museum Archives, Catalog #: 01_00091291)

A Transcontinental and Western Airlines (TWA) Boeing 307 Stratoliner with cabin attendants. (TWA) — A Transcontinental and Western Airlines (TWA) Boeing 307 Stratoliner with cabin attendants. (Trans World Airlines)

As a result of the crash of NX19901, production Stratoliners were fitted with a vertical fin similar to that of the B-17E Flying Fortress.

Pan American Airways’ Boeing 307 Stratoliner NC19903, photographed 18 March 1940. Note the new vertical fin. (Boeing via Goleta Air and Space Museum)

During World War II, TWA sold its Stratoliners to the United States government which designated them C-75 and placed them in transatlantic passenger service.

Boeing C-75 Stratoliner. (San Diego Air and Space Museum Archive, Catalog # 01 00091316) — Boeing C-75 Stratoliner “Comanche,” U.S. Army Air Corps serial number 42-88624, formerly TWA’s NC19905. (San Diego Air & Space Museum Archives, Catalog # 01_00091316)

Two TWA stewardesses with a Boeing 307 Stratoliner, circa 1950. (San Diego Air & Space Museum)

In 1944, the 307s were returned to TWA and they were sent back to Boeing for modification and overhaul. The wings, engines and tail surfaces were replaced with those from the more advanced B-17G Flying Fortress. The last one in service was retired in 1951.

Of the ten Stratoliners built for Pan Am and TWA, only one remains. Fully restored by Boeing, NC19903 is at the Stephen F. Udvar-Hazy Center of the Smithsonian Institution.

The only existing Boeing Model 307 Stratoliner, NC19903, Clipper Flying Cloud, at the Smithsonian Institution National Air and Space Museum, Steven F. Udvar-Hazy Center. (Photo by Dane Penland, National Air and Space Museum, Smithsonian Institution)

Boeing Model 307 Stratoliner NX19903 after upgrade, circa 1945. (Boeing)

15 October 1937

October 15, 2023Aviation35-277, Boeing Airplane Company, Boeing Model 294, Boeing XB-15, Eddie Allen, Edmund Turney Allen, First Flight, NACA Full Scale Wind Tunnel, Pratt & Whitney R-1830-11, Pratt & Whitney Twin Wasp S1B3-GBryan Swopes

Boeing XB-15 35-277 takeoff at Boeing Field. (United States Air Force 060511-F-1234S-050) — The Boeing XB-15 takes off on its first flight, Boeing Field, 15 October 1937. (U.S. Air Force)

15 October 1937: Test pilot Edmund Turney (“Eddie”) Allen, a consulting engineer to Boeing, and Major John D. Korkille, Air Corps, United States Army, made the first flight of the prototype Boeing XB-15, 35-277, at Boeing Field, Seattle, Washington. Major Corkille reported that the airplane “handled easily and maneuvered readily.”

The flight deck of the Boeing XB-15. The radio operator’s station is on the left, and the navigator’s on the right. (The Boeing Company)

The Boeing Model 294, designated XB-15 by the Air Corps, was an experimental airplane designed to determine if a bomber with a 5,000 mile (8,047 kilometers) range was possible. It was designed at the same time as the Model 299 (XB-17), which had the advantage of lessons learned by the XB-15 design team. The XB-15 was larger and more complex than the XB-17 and took longer to complete. It first flew more than two years after the prototype B-17.

The Boeing Model 294 (XB-15) at Boeing Field, Seattle, Washington. The prototype bomber was rolled out for engine tests, 27 September 1937. (The Boeing Company)

Designers had planned to use an experimental 3,421.19-cubic-inch-displacement (56.063 liter) liquid-cooled, supercharged and turbosupercharged Allison V-3420 twenty-four cylinder, four-bank “double V” engine which produced a maximum of 2,885 horsepower at 3,000 r.p.m. The engine was not available in time, however, and four air-cooled Pratt & Whitney R-1830 (Twin Wasp) engines were used instead. With one-third the horsepower, this substitution left the experimental bomber hopelessly underpowered as a combat aircraft.

Boeing XB-15 35-277, left front quarter view. (United States Air Force 060511-F-1234S-038) — Boeing XB-15 35-277. (U.S. Air Force)

Boeing XB-15 35-277, front view. (United States Air Force 060511-F-1234S-039) — Boeing XB-15 35-277. (U.S. Air Force)

Boeing XB-15 35-277. right rear quarter view. (United States Air Force 060511-F-1234S-043) — Boeing XB-15 35-277. (U.S. Air Force)

The XB-15 was a very large four-engine mid-wing monoplane with retractable landing gear. It was of aluminum monocoque construction with fabric-covered flight control surfaces. The XB-15 had a ten-man crew which worked in shifts on long duration flights.

The prototype bomber was 87 feet, 7 inches (26.695 meters) long with a wingspan of 149 feet (45.415 meters) and overall height of 18 feet, 1 inch (5.512 meters). The airplane had an empty weight of 37,709 pounds (17,105 kilograms) and maximum takeoff weight of 70,706 pounds (32,072 kilograms)—later increased to 92,000 pounds (41,730 kilograms).

As built, the XB-15 was powered by four air-cooled, supercharged, 1,829.39-cubic-inch-displacement (29.978 liter) Pratt & Whitney Twin Wasp S1B3-G (R-1830-11) two-row 14-cylinder radial engines, rated at 850 horsepower at 2,450 r.p.m. at 5,000 feet (1,524 meters), and 1,000 horsepower at 2,600 r.p.m. for take off. The engines turned three-bladed controllable-pitch propellers through a 3:2 gear reduction. The R-1830-11 was 4 feet, 8.66 inches (1.439 meters) long with a diameter of 4 feet, 0.00 inches (1.219 meters), and weighed 1,320 pounds (599 kilograms).

These gave the experimental airplane a maximum speed of 197 miles per hour (317 kilometers per hour) at 5,000 feet (1,524 meters) and a cruise speed of 152 miles per hour (245 kilometers per hour) at 6,000 feet (1,829 meters). The service ceiling was 18,900 feet (5,761 meters) and maximum range was 5,130 miles (8,256 kilometers).

The Boeing XB-15 experimental long-range heavy bomber flies in formation with a Boeing YP-29 pursuit. (U.S. Air Force)

The bomber could carry a maximum of 12,000 pounds (5,443 kilograms) of bombs in its internal bomb bay, and was armed with three .30-caliber and three .50-caliber machine guns for defense.

Only one XB-15 was built. During World War II it was converted to a transport and redesignated XC-105. In 1945 it was stripped and abandoned at Albrook Field, Territory of the Canal Zone, Panama.

The XB-15 set several Fédération Aéronautique Internationale (FAI) world records: On 30 July 1939, the XB-15 carried 14,135 kilograms (31,162 pounds) to an altitude of 2,000 meters (6,562 feet) over Fairfield, Ohio.¹ The same flight set a second record by carrying 10,000 kilograms (22,046 pounds) to an altitude of 8,228 feet (2,508 meters).² On 2 August 1939, the XB-15 set a World Record for Speed Over a Closed Circuit of 5000 Kilometers With 2000 Kilogram Payload, at an average speed of 267.67 kilometers per hour (166.32 miles per hour).³

¹ FAI Record File Number 8739

² FAI Record File Number 8740

³ FAI Record File Number 10865

21 September 1942

September 21, 2023Aviation41-002, Al Reed, Boeing B-29 Superfortress, Boeing Model 345, Boeing XB-29, Eddie Allen, Edmund Turney Allen, First Flight, Flight Test, Long Range Heavy Bomber, Prototype, Test Pilot, Wright Aeronautical Division, Wright Aeronautical Division 670C18H1 Duplex-Cyclone, Wright R-3350-13Bryan Swopes

Boeing XB-29 prototype takes off from Boeing Field, Seattle, Washington, 1942. (San Diego Air & Space Museum, Catalog #: 16_002357) — A Boeing XB-29 takes off from Boeing Field, Seattle, Washington. (SDASM)

21 September 1942: At Boeing Field, Seattle, Washington, the Boeing Model 345, the first of three XB-29 prototypes, Air Corps serial number 41-002, took off on its first flight.

Edmund T. “Eddie” Allen, Director of Aerodynamics and Flight Research, was in command, with Al Reed, Chief of Flight Test and Chief Test Pilot, as co-pilot. They climbed to 6,000 feet (1,829 meters) and began testing the XB-29’s stability and control, control power and response, and stall characteristics.

The flight was uneventful. Landing after 1 hour, 15 minutes, Allen is supposed to have said, “She flew!”

Allen, Edmund Turney ("Eddie"), leans out of a cockpit window of the Boeing XB-29 after its first taxi test. (Boeing Images BI219398). — Eddie Allen lean’s out of a cockpit window following the first taxi test of the XB-29. (Boeing)

The XB-29 was 98 feet, 2 inches (29.921 meters) long with a wing span of 141 feet, 3 inches (43.053 meters), and 27 feet, 9 inches (8.458 meters) high to the top of its vertical fin. The prototype bomber had a gross weight of 105,000 pounds (47,627 kilograms).

The prototype bomber was powered by four air-cooled, supercharged and fuel-injected 3,347.662-cubic-inch-displacement (54.858 liter) Wright Aeronautical Division Duplex-Cyclone 670C18H1 (R-3350-13) twin-row 18-cylinder radial engines with a compression ratio of 6.85:1. The R-3350-13 was rated at 2,000 horsepower at 2,400 r.p.m., and 2,200 horsepower at 2,800 r.p.m. for takeoff, burning 100-octane gasoline. These engines drove 17-foot-diameter (5.182 meters) three-bladed Hamilton Standard constant-speed propellers through a gear reduction of 0.35:1. The R-3350-13 was 76.26 inches (1.937 meters) long, 55.78 inches (1.417 meters) in diameter, and weighed 2,668 pounds (1,210 kilograms). Wright built 50 of these engines.

Boeing XB-29 41-002. (San Diego Air & Space Museum Archives, Ray Wagner Collection, Catalog #: 16_006342) — Boeing XB-29 41-002. (SDASM)

The XB-29 had a maximum speed of 368 miles per hour (592 kilometers per hour) and cruised at 255 miles per hour (410 kilometers per hour). Its service ceiling was 32,100 feet (9,784 meters).

The airplane was designed to carry 20,000 pounds (9,072 kilograms) of bombs. Though the prototypes were unarmed, the production B-29s were defended by 10 Browning AN-M2 .50-caliber machine guns in four remotely-operated power turrets, with 2 more .50-caliber machine guns and a single AN-M2 20mm autocannon in the tail.

Boeing XB-29 41-002, left rear quarter view. (San Diego Air & Space Museum, Catalog #: 16_002355) — Boeing XB-29 41-002. (SDASM)

The B-29 was manufactured by Boeing at Seattle and Renton, Washington, and at Wichita, Kansas; by the Glenn L. Martin Company at Omaha, Nebraska; and by Bell Aircraft Corporation, Marietta, Georgia. There were three XB-29 prototypes, 14 YB-29 pre-production test aircraft, 2,513 B-29, 1,119 B-29A, and 311 B-29B Superfortress aircraft. The bomber served during World War II and the Korean War and continued in active U.S. service until 1960.

The first prototype, 41-002, was scrapped in 1948.

Boeing B-29A-30-BN Superfortress 42-94106, circa 1945. (U.S. Air Force)

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