Tag Archives: First Flight

2 December 1936

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Boeing YB-17 Flying Fortress 36-149. (U.S. Air Force)
Boeing YB-17 Flying Fortress 36-149. (U.S. Air Force)

2 December 1936: The first Boeing YB-17, U.S. Army Air Corps serial number 36-149, made its first flight.

Although the prototype Boeing Model 299, X13372, had crashed at Wright Field, Ohio, 30 October 1935, the Army had ordered thirteen Y1B-17 service test aircraft, serials 36-149–36-161. Prior to the model’s first flight, this designation was changed to YB-17. (The “-1-” in the original Y1B-17 designation indicated that the service test bombers were ordered using funding other than the normal appropriations for new aircraft.)

Boeing YB-17. (U.S. Air Force)
Boeing YB-17 36-149. (U.S. Air Force)

The YB-17 had several improvements over the Model 299, which was retroactively designated XB-17. There was a long carburetor intake on top of the engine nacelles which visually distinguishes the YB-17 from the follow-on YB-17A. The main landing gear has one strut rather than the two of the Model 299. A vertical radio mast is just behind the cockpit.

Boeing YB-17 36-149. (U.S. Air Force)

The Boeing Model 299B, designated YB-17 by the Army Air Corps, was 68 feet, 4 inches (20.828 meters) long with a wingspan of 103 feet, 9⅜ inches (31.633 meters) and the overall height was 18 feet, 4 inches (5.588 meters). It had an empty weight of 24,465 pounds (11,097 kilograms), gross weight of 34,880 pounds (15,821 kilograms) and maximum takeoff weight of 42,600 pounds (19,323 kilograms).

Boeing YB-17 36-149. (U.S. Air Force)

Instead of the Pratt & Whitney engines installed on the 299, the YB-17 had four air-cooled, supercharged 1,823.129-cubic-inch-displacement (29.876 liter) Wright Aeronautical Division Cyclone 9 R-1820G5 (R-1820-39) nine-cylinder radial engines with a compression ratio of 6.45:1. They turned three-bladed Hamilton Standard constant-speed propellers through a 16:11 gear reduction drive, in order to match the engines’ effective power range with the propellers. The R-1820-39 was rated at 805 horsepower at 2,100 r.p.m., at Sea Level, and 930 horsepower at 2,200 r.p.m. for takeoff. The R-1820-39 was 45-7/16 inches (1.154 meters) long and 54¼ inches (1.378 meters) in diameter, and weighed 1,198 pounds (543.4 kilograms).

The cruise speed of the YB-17 was 217 miles per hour (349 kilometers per hour) and the maximum speed was 256 miles per hour (412 kilometers per hour) at 14,000 feet (4,267 meters). Its service ceiling was 30,600 feet (9,327 meters). The bomber’s maximum range was 3,320 miles (5,343 kilometers).

Cutaway illustration of the Boeing YB-17. (John T. Jacobsen)

The YB-17 could carry 8,000 pounds (3,629 kilograms) of bombs. Defensive armament consisted of five .30-caliber air-cooled Browning machine guns.

Boeing YB-17 36-149 nosed over on landing at Seattle, 7 December 1936. (Unattributed)

36-149 was damaged in a landing accident 7 December 1936. It was repaired and then flown to Wright Field, Dayton, Ohio, 11 January 1937. After testing at Wright Field, 36-149 was delivered to the 2nd Bombardment Group, Langley Field, Virginia. By 1938 the bomber was back at Wright Field for additional tests.

“In the summer of 1938, Bill [Captain William C. Bentley, Jr., U.S. Army Air Corps, a B-17 test pilot at Langley Field] and his aircrew flew back to Seattle to pick up an additional aircraft, YB-17 tail number 36-149 from Boeing. This aircraft was different from the original thirteen. During its assembly phase at Boeing, it was packed with additional instruments for recording purposes. Once delivered to Langley, the plane was going to be subjected to a variety of stress tests in order to determine how much damage the plane could take and still operate. During its flight to Langley, Bill arrived over the field in a thunderstorm. The strength of the storm flipped the plane upside down, a stress never envisioned by the designers for such a large aircraft, much less one loaded to capacity with measuring instrumentation and a full crew. Using his fighter pilot training, Bill flew the aircraft at its maximum altitude then performed a slow roll to bring the airplane into its proper attitude. After recovering from a harrowing spin, Bill got control of the plane and landed successfully.

“Much to the crew’s amazement, the wings were slightly bent and some rivets were missing. But the measuring instrumentation had recorded all of the stress placed on the plane. . . .”

—The Touch of Greatness: Colonel William C. Bentley, Jr., USAAC/USAF, by Stewart W. Bentley, Jr., Ph.D., AuthorHouse, Bloomington, Indiana, 2010, Chapter 2 at Page 45.

(This meant that a fourteenth YB-17, which had been built specifically as a static test article, could be completed as a Y1B-17A, 37-369.)

Boeing YB-17 at Hamilton Field, California. (U.S. Air Force)

In October 1940 36-149 was transferred to the 19th Bombardment Group at March Field, California. Finally, on 11 February 1942, it was transferred to the Air Park at Amarillo Army Air Field, a B-17 training base in Texas. It was written off 11 December 1942.

After several years of testing, the YB-17 went into production as the B-17 Flying Fortress. By the end of World War II, 12,731 B-17s had been built by Boeing, Douglas and Lockheed Vega.

Boeing YB-17 36-139 arrives at Langley Field, Virginia, 1 March 1937. (U.S. Air Force)
Boeing YB-17 36-139 arrives at Langley Field, Virginia, 1 March 1937. (U.S. Air Force)
Boeing YB-17 36-149 at Langley Field, Virginia, 1 March 1937. (U.S. Air Force)
Boeing YB-17 36-149 at the Golden Gate International Exposition, Treasure Island, California, ca. 1939. (Stephen Fisher)
Two of the 13 Boeing YB-17 Flying Fortress (Model 299B) service test prototypes. This model can be distinguished from other early B-17s by the vertical radio mast behind the cockpit and the long carburetor intakes on the top of the engine nacelles. (Horace Bristol/LIFE Magazine)

© 2023, Bryan R. Swopes

1909: De Havilland No. 1

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De Havilland No. 1 at Seven Barrows, Hampshire, 1909. (BAE Systems)

History has forgotten the actual date—perhaps because he was no one of  any importance at the time—but one day in the Fall or Winter of 1909, Geoffrey de Havilland, an automotive engineer, took off from Seven Barrows, Hampshire, England, in an airplane of his own design. Today, that airplane is known as the de Havilland No. 1.

De Havilland had borrowed £1,000 from his grandfather, and together with fellow engineer Francis Trounson Hearle, built an airplane.

The de Havilland No. 1 was a single-engine, single-place, three-bay biplane in a pusher configuration. It had a forward elevator (canard), and an aft-mounted rudder and adjustable horizontal stabilizer. Ailerons were mounted on the upper wing.

The structure of the airplane was built of American white wood (which proved to be a poor choice) and was braced with steel wires. The fuselage was an open girder tapered at each end. It was built of 1½″ × 1½″ (3.81 × 3.81 centimeters) longitudinals with 1¼″ × ¼″ (3.175 × 0.635 centimeter) cross braces from the engine aft. It had a cross section at the widest point of 2′4″ x 2′0″ (0.711 × 0.610 meters). The lower longitudinals were reinforced with angled steel beneath the engine

The de Havilland was 29 feet, 0 inches (8.839 meters) long with a wingspan of 36 feet, 0 inches (10.973 meters). Both wings had a chord of 6 feet, 0 inches (1.829 meters) and the vertical gap was also 6 feet, 0 inches. The wings were not staggered. The airplane weighed 850 pounds ( kilograms).

Three-view illustration of the de Havilland No. 1. (FLIGHT, 9 April 1910, Page 267)

The DH.1 was powered by a single water-cooled, normally-aspirated, 302.18 cu in (4.95 liters) de Havilland-Iris four-cylinder horizontally-opposed overhead valve engine, designed by Geoffrey de Havilland and built by the Iris Motor Co., Willesden, London. The engine produced 40 horsepower at 1,050 r.p.m., and 52 horsepower at 1,500 r.p.m. In running condition, it weighed 230 pounds (104 kilograms) including a 30 pound (14 kilogram) flywheel. The de Havilland-Iris used cast iron cylinders with a copper water jacket. The two-throw crankshaft was prone to failures after a only few hours of operation.

The engine was mounted in the airframe with its crankshaft at a right angle to the direction of flight. It drove two 7 foot, 4 inch (2.235 meter) diameter counter-rotating propellers made of aluminum. The paddle-type blades could be adjusted for pitch before flight. Tubular shafts drove through 90° bevel gears and turned the propellers at 550–600 r.p.m.

De Havilland 302 cubic inch (4.95 liter) 45-horsepower four-cylinder horizontally-opposed aircraft engine. (FLIGHT)
Cross section of de Havilland-Iris four-cylinder engine. (FLIGHT)

And it should be added that the past tense has advisably been used in the foregoing paragraph, inasmuch as the first free flight of the machine terminated in almost complete wreckage. The first time that it left the ground it did so after travelling some 40 yards on a downward slope under its own power; it then rose at a rather steep angle, which was corrected by the pilot; and almost immediately afterwards—about 35 yards from the take-off—the left main plane doubled up, causing the machine to fall heavily forward and to the left. Luckily, Mr. de Havilland himself was not hurt, but it will be observed from some of the photographs which we reproduce that the machine as such, apart from the propelling mechanism, the rudder, and the tail, was, for all practical purposes, virtually annihilated by the fall.

—FLIGHT, No. 67 (Vol. II, No. 15), 9 April 1910, Page 266, Column 1

(Flight No. 68, Vol. II, No. 16, 16 April 1910, Page 286)

The airplane’s engine was salvaged and reused in de Havilland No. 2.

Geoffrey de Havilland, O.B.E., A.F.C., photographed 2 January 1920 by Bassano Ltd. (© National Portrait Gallery, London)

© 2019, Bryan R. Swopes

25 November 1940

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The first Martin Marauder, B-26-MA 40-1361, takes off for the first time at Middle River, Maryland, 25 November 1940. (U.S. Air Force)
The first Martin Marauder, B-26-MA 40-1361, takes off for the first time at Middle River, Maryland, 25 November 1940. (U.S. Air Force)

25 November 1940: Glenn L. Martin Company’s engineer and test pilot William Kenneth Ebel, co-pilot Ed Fenimore and flight engineer Al Malewski made the first flight of the first B-26 Marauder, Army Air Corps serial number 40-1361.

The B-26 was a twin-engine medium bomber designed with high speed as a primary objective. Production of the new airplane was considered so urgent that there were no prototypes. All aircraft were production models.

Martin B-26-MA Marauder 40-1361, right profile, with bomb bay doors open. (U.S. Air Force)
Martin B-26-MA Marauder 40-1361, right profile, with engines idling. (U.S. Air Force)

The B-26 Marauder was 58 feet, 2.5 inches (17.742 meters) long with a wingspan of 65 feet, 0 inches (19.812 meters) ¹ and overall height of 19 feet, 10.3 inches (6.053 meters). At the root, the wings’ chord was 12 feet, 10.5 inches (3.924 meters), with an angle of incidence of 3° 30′. The wing center section had no dihedral, while the the outer panels had +1° 17′. The total wing area was 602 square feet (56 square meters). The bomber had an empty weight of 21,375 pounds (9,696 kilograms) and gross weight of 32,025 pounds (14,526 kilograms).

The prototype was powered by two air-cooled, supercharged, 2,804.4-cubic-inch-displacement (45.956 liter), Pratt & Whitney R-2800-5 two-row, 18-cylinder radial engines with a compression ratio of 6.65:1. The R-2800-5 had a Normal Power rating of 1,500 horsepower at 2,400 r.p.m. to 7,500 feet (2,286 meters) and a Takeoff/Military Power rating of 1,850 horsepower at 2,600 r.p.m. to 2,700 feet (823 meters). They turned 13 foot, 6 inch (4.115 meter) diameter four-bladed, constant-speed Curtiss Electric propellers through a 2:1 gear reduction. The R-2800-5 was 6 feet, 3.72 inches (1.923 meters) long, 4 feet, 4.06 inches (1.322 meters) in diameter, and weighed 2,270 pounds (1,030 kilograms).

40-1361 had a maximum speed of 326 miles per hour (525 kilometers per hour) at 14,250 feet (4,343 meters) with the engines turning 2,400 r.p.m. Its service ceiling was 25,000 feet (7,620 meters), and the absolute ceiling was 26,200 feet (7,986 meters).

Martin B-26-MA Marauder 40-1361, the first production airplane, 25 November 1940. (U.S. Air Force)
Martin B-26-MA Marauder 40-1361, the first production airplane, 25 November 1940. (U.S. Air Force)

When the B-26 entered service, it quickly gained a reputation as a dangerous airplane and was called the “widowmaker,” and also had several less polite nicknames. The airplane had relatively short wings with a small area for its size. This required that landing approaches be flown at much higher speeds than was normal practice. With one engine out, airspeed was even more critical. Some changes were made, such as a slight increase of the wingspan and the size of the vertical fin and rudder. At the same time, an emphasis was made on airspeed control during training. During World War II, the Marauder had the lowest rate of combat losses of any American bomber.

Prototype Martin B-26 40-1361 taxiing. (U.S. Air Force)
Prototype Martin B-26 40-1361 taxiing. (U.S. Air Force)

201 B-26s were built before production switched to the B-26A. Glenn L. Martin Co. produced 5,288 Marauders between 1941 and 1945, with manufacturing taking place at Middle River, Maryland, and Omaha, Nebraska. The Marauder served in the Pacific, Mediterranean and European combat areas, with both the United States and several Allied nations. When it was removed from service at the end of World War II, the “B-26” designation was reassigned to the Douglas A-26 Invader, a twin-engine light bomber.

The first Martin Marauder, B-26-MA 40-1361, was written off after a belly landing at Patterson Field, Ohio, 8 August 1941.

Martin B-26 40-1361 with engines turning, 28 November 1940. (U.S. Air Force)
Martin B-26 40-1361 with engines turning, 28 November 1940. (U.S. Air Force)

William Kenneth Ebel was born at Orangeville, Illinois, 2 January 1899. He was the first of two sons of Willam Henry Ebel, a farmer, and Nora Agnes Rubendall Ebel.

Ken Ebel attended Heidelberg College at Tiffin, Ohio. While at Heidelberg, on 1 October 1918, he enlisted as a private in the Student Army Training Corps (S.A.T.C.). With World War I coming to an end in November, Private Ebel was discharged 20 December 1918. Ebel graduated from Heidelberg in 1921 with a bachelor of arts degree.

Ebel returned to military service, enlisting as a private in the 104th Squadron (Observation), Maryland National Guard, based at Baltimore, Maryland.

Ebel continued his college education at the Case School of Applied Science in Cleveland, Ohio. In 1923, he earned a bachelor of science degree in mechanical engineering (B.S.M.E.)

Ken Ebel, 104th Observation Squadron.

On 11 September 1923, Private Ebel was appointed an aviation cadet, graduating from primary flying school on 3 June 1924. He received a commission as a 2nd lieutenant, Officers Reserve Corps (O.R.C.), United States Army, on 12 June 1925.

Continuing to serve as a reserve officer, in 1926 Ebel went to work as an engineer for the Glenn L. Martin Company, then located in Cleveland, Ohio. As a test pilot and engineer, Ebel flew the Martin M-130 four-engine flying boat.

2nd Lieutenant Ebel,still with the 104th Squadron, Maryland National Guard, was promoted to the rank of 1st lieutenant on 21 December 1928. The U.S. Army advanced his rank to 1st lieutenant, Air Corps, 15 February 1929.

On 21 October 1929, William K. Ebel married Miss Florence E. Sherck at Seneca, Ohio. They would have two children, William Kenneth, Jr., and Lydia Lynn Ebel.

While testing a Martin BM-2 dive bomber, on 11 August 1932, W.K. Ebel “leaped to safety in a parachute Friday when a bombing plane he was testing failed to come out of a spin and crashed at Dahlgren, Virginia. The plane was going through its final tests before being delivered to the navy. It was wrecked in the crash.” Ebel became Member No. 495 of The Caterpillar Club.

Martin M-130 NX14714 during engine testing. (Glenn L. Martin Co.)

On Thursday, 20 December 1934, Chief Pilot Ken Ebel took the new four-engine Martin M-130 flying boat, Pan American Airways System’s Hawaii Clipper, for its first flight from Middle River, Maryland. He also made the first flight of the M-156 “Russian Clipper” in 1935.

Ebel was promoted to captain, Air Corps, on 5 January 1935. On 21 August, he delivered the new Martin Model 146 “mystery bomber” to Wright Field for evaluation by the Bombardment Board.

The Martin Model 146 medium bomber prototype at Wright Field for evaluation, 1935. (Ray Wagner Collection, San Diego Air & Space Museum Archives)

In 1942, Ken Ebel earned a doctorate (Ph.D.) in engineering from the Case School of Applied Science.

On 3 July 1942, Ken Ebel took the Martin XPB2M-1 Mars flying boat prototype for its first flight.

Martin XPB2M-1 Mars taxi test, 1942. (Charles M. Daniels Collection, San Diego Air & Space Museum Archives)

In 1948, Ken Ebel became director of the Airplane Division of the Curtiss-Wright Corporation in Columbus, Ohio. Soon after, Curtiss-Wright sold its airplane division to North American Aviation. In 1950, the U.S. Navy’s primary submarine builder, the Electric Boat Company, appointed Ebel as Vice Pressident of Engineering for its Canadair Ltd., aircraft manufacturing subsidiary in Montreal, Quebec, Canada. (In 1952, after acquiring Convair, the corporation reorganized as General Dynamics.

William K. Ebel

Ebel returned to the United States in 1961 and served as a consultant for General Dynamics in Washington, D.C. Ebel retired in 1963, purchasing teh Mount Pleasant Orchards near Baltimore.

Mrs. Ebel died in 1968. He later married Helene H. Topping.

William Kenneth Ebel, Ph.D., died at the Greater Baltimore Medical Center, 12 July 1972.

¹ The wing span was increased to 71 feet, 0 inches (21.641 meters) with the B-26B-10-MA.

© 2018, Bryan R. Swopes

25 November 1940

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The prototype de Havilland DH.98 Mosquito, W4050, takes off on its first flight at Hatfield, 25 November 1940. (BAE Systems)

25 November 1940: De Havilland Aircraft Company’s Chief Test Pilot, Geoffrey Raoul de Havilland, Jr., and engineer John Walker, made the first flight of the DH.98 Mosquito prototype, E0234, at Hatfield, Hertfordshire, England. The prototype’s Royal Air Force identification was W4050. The multi-role combat aircraft was constructed primarily of layers of balsa covered with layers of birch, then a layer of doped cotton fabric. It was powered by two Rolls-Royce Merlin V-12 engines.

Sir Geoffrey de Havilland, Jr, with a DH.98 Mosquito, 14 October 1943. (Photo by Reg Speller/Fox Photos/Getty Images 3320005)

The construction materials took advantage of plentiful supplies of wood, and also made workers who were not in the standard metal aircraft industry able to take part.

The prototype was rolled out 19 November 1040, painted overall yellow.

The prototype de Havilland DH.98 Mosquito, E0234, outside the Assembly Building, 19 November 1940. (BAE Systems)

The prototype had a wingspan of 54 feet, 2 inches (16.510 meters), and its gross weight was 19,670 pounds (8,922 kilograms). W4050 was powered by two liquid-cooled, supercharged, 1,648.96-cubic-inch-displacement (27.01 liter) Rolls-Royce Merlin Mk.21 single overhead camshaft (SOHC) 60° V-12 engines, producing 1,460 horsepower at 3,000 r.p.m. at 10,000 feet (3028 meters), with 10 pounds (0.69 Bar) of boost, and driving three-bladed de Havilland Hydromatic propellers through a gear reduction.

The prototype DH.98 Mosquito,now marked W4050, in the field behind Salisbury Hall (where it was designed and built) just before its first flight, 25 November 1940. (HistoryNet)

The DH.98 had been predicted to be 20 miles per hour (32 kilometers per hour) faster than the Supermarine Spitfire, but was actually much faster. In testing, the prototype reached 392 miles per hour (631 kilometers per hour) at 22,000 feet (6,706 meters). Improvements were continuously made, and with 2-stage superchargers, W4050 reached a maximum 437 miles per hour (703 kilometers per hour). The DH.98 prototype had a service ceiling of 34,000 feet (10,363 meters) and range of 2,180 miles (3,500 kilometers).

The production fighter variant, the Mosquito F. Mk.II, was 41 feet, 2 inches (12.548 meters) long with a wingspan of 54 feet, 2 inches (16.510 meters) and height of 15 feet, 3 inches (4.648 meters) in 3-point position. The wings had 1½° incidence with approxmatey 2½° dihedral. The leading edges were swept aft 2½°. The total wing area was 436.7 square feet (40.6 square meters). The fighter’s empty weight was 13,356 pounds (6,058 kilograms) and the maximum takeoff weight was 18,649 pounds (8,459 kilograms). The Mk.II had a total fuel capacity of 553 gallons.

The Mk.II had a cruise speed of 265 miles per hour (426 kilometers per hour) at 15,000 feet (4,572 meters) and maximum speed of 380 miles per hour (612 kilometers per hour) at 21,400 feet (6,523 meters).

Mosquito bomber variants could carry four 500 pound bombs, or two 2,000 pound bombs, but were otherwise unarmed. Fighters were equipped with four Hispano Mk.II 20 mm autocannon and four Browning .303-caliber Mk.II machine guns in the nose.

6,411 DH.98 Mosquitoes were built in England, 1,134 in Canada and 212 in Australia. It was produced in bomber, fighter, night fighter, fighter bomber and photo reconnaissance versions.

The prototype DH.98 Mosquito, W4050, at Hatfield, Hertfordshire. (Royal Air Force)

W4050’s (the prototype’s Royal Air Force identification) fuselage was damaged while taxiing at Boscombe Down, 24 February 1941, and had to be replaced with one intended for a second prototype, W4051. It remained at de Havilland and was used to test different engines, armaments and versions. After a series of tests conducted in December 1943, the prototype Mosquito was permanently grounded. It was used as an instructional airframe and later placed in storage.

In September 1958, W4050 was turned over to the de Havilland Aircraft Heritage Centre. Today, the restored prototype DH.98 Mosquito is at the museum at London Colney, Hertfordshire, England.

The Mosquito prototype with camouflauged upper surfaces as it appeared at Boscombe Down, (de Havilland Aircraft Museum)
The Mosquito prototype with camouflaged upper surfaces as it appeared at Boscombe Down, 1941. (de Havilland Aircraft Museum)

© 2020, Bryan R. Swopes

23 November 1959

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Boeing 720-022 c/n 17907, N7201U. (Boeing)
Boeing 720-022 c/n 17907, N7201U, parked on the taxiway at the south shore of Lake Washington. (Boeing)

23 November 1959: The first Boeing 720 airliner, a 720-022, registered as N7201U, made its first flight at Renton, Washington. The 720 was a development of the 707 and no prototype was built. N7201U was used by Boeing for flight testing and was then delivered to United Airlines, 1 October 1960. The airline named the new 720 Jet Mainliner Capt. F. M. Crismore. Over the next two years, United acquired 29 Boeing 720s.

N7201U was sold to Contemporary Entertainment, owned by singer Bobby Sherman and his manager, Ward Sylvester, in January 1973. It was repainted in a gold and black livery and christened The Starship. As a VIP transport, it was used by such rock bands as Led Zeppelin, Deep Purple, The Rolling Stones, Alice Cooper and Elton John. It was last chartered by Peter Frampton.

N7201U was withdrawn from service in 1977 and after being stored for several years, was broken up at Luton Airport near London, England, in 1982.

The Boeing 720 was a variant of the Model 707, intended for short to medium range flights. It had 100 inches (2.54 meters) removed from the fuselage length and improvements to the wing, decreasing aerodynamic drag.

Boeing built 154 720 and 720B airliners from 1959 to 1967.

The Boeing 720 was operated by a flight crew of four and could carry up to 149 passengers. It was 136 feet, 2 inches (41.25 meters) long with a wingspan of 130 feet, 10 inches (39.90 meters) and overall height of 41 feet, 7 inches (12.65 meters). The airplane had an empty weight of 103,145 pounds (46,785 kilograms) and Maximum Takeoff Weight of 220,000 pounds (100,800 kilograms).

The Boeing 720 was powered by four Pratt & Whitney Turbo Wasp JT3C-7 turbojet engines, a civil variant of the military J57 series. The 720B was equipped with the more efficient P&W JT3D-1 turbofan engines. The JT3C-7 was a “two-spool” axial-flow engine with a 16-stage compressor (9 low- and 7 high-pressure stages), 8 combustion tubes, and a 3-stage turbine (1 high- and 2 low-pressure stages). It was rated at 12,030 pounds of thrust (53.512 kilonewtons) for takeoff.

The JT3D-1 was a dual axial-flow turbofan engine, with a 2-stage fan section 13-stage compressor (6 low- and 7 high pressure stages), 8 combustion chambers and a 4-stage turbine (1 high- and 3 low-pressure stages). This engine was rated at 14,500 pounds of static thrust (64.499 kilonewtons) at Sea Level, and 17,000 pounds (75.620 kilonewtons), with water injection, for takeoff (2½ minute limit). Almost half of the engine’s thrust was produced by the fans. Maximum engine speed was 6,800 r.p.m. (N1) and 10,200 r.p.m. (N2). It was 11 feet, 4.64 inches (3.471 meters) long, 4 feet, 5.00 inches (1.346 meters) wide and 4 feet, 10.00 inches (1.422 meters) high. It weighed 4,165 pounds (1,889 kilograms). The JT3C could be converted to the JT3D configuration during overhaul.

The maximum cruise speed was 611 miles per hour (983 kilometers per hour) and maximum speed was 620 miles per hour (1,009 kilometers per hour). Range at at maximum payload was 4,370 miles (7,033 kilometers).

The last flight of a Boeing 720 was on 9 May 2012, when a 720B aircraft used by Pratt and Whitney Canada as a test aircraft was placed in the National Air Force Museum of Canada at Trenton, Ontario.

United Airlines' Boeing 720-022, N7201U. (Unattributed)
United Airlines’ Boeing 720-022, N7201U. The airliner’s name, “Jet Mainliner Capt. F. M. Crismore,” is visible under the cockpit windows. (Bill Larkins via Wikipedia)

© 2018, Bryan R. Swopes