Geoffrey de Havilland, 1913. (FLIGHT, 22 February 1913, Page 207))
18 August 1911: At 6:30 a.m., the Royal Aircraft Factory F.E.2 prototype took off with its designer, Geoffrey de Havilland,¹ at the controls. He made the short flight from Farnborough to Laffan’s Plain where he made a series of takeoffs and landings.
The airplane was a single-engine, two-place, two-bay biplane with a pusher propeller. The crew, a pilot and an observer/gunner, were in an open nacelle, with the engine aft, and an open tail boom.
The F.E.2 was 28 feet (8.5 meters) long with a wing span of 33 feet (10.0 meters). The total wing area was 340 square feet (31.6 square meters). It weighed 1,200 pounds (544 kilograms), loaded, and had a maximum speed of 47.5 miles per hour (76.4 kilometers per hour). The F.E.2 prototype, in its original configuration, was powered by an air-cooled Gnome 7-cylinder rotary engine which produced 50 horsepower.
Royal Aircraft Factory F.E. 2 with Maxim gun (RAF Museum)
In 1913, the F.E.2 prototype was redesigned and rebuilt with an air-cooled Renault V-8 engine, rated at 70 horsepower, driving a four-bladed fixed-pitch propeller. The wings were identical to those of the the B.E.2A. The Renault-powered F.E.2 variant was 30 feet, 0 inches (9.144 meters) long with a wingspan of 42 feet, 0 inches (12.802 meters). The wings had a chord of 6 feet, 4 inches (1.930 meters). The wing area increased to 425 square feet (39.5 square meters). The gross weight was now 1,865 pounds (846 kilograms). The F.E.2 (Renault) had a maximum speed of 67 miles per hour (108 kilometers per hour) and a service ceiling of 5,500 feet (1,676 meters).
At about 11:45 a.m., Monday, 23 February 1914, test pilot Roland Campbell Kemp (R.Ae.C. Aviator’s Certificate No. 80) was flying the F.E.2 at about 500 feet (152 meters). Also on board was a passenger, Ewart Temple Haynes. The wind was estimated at 30 miles per hour (13 meters per second). After about five minutes, the prototype entered a steep—but not heavily banked—right-hand spiral descent and crashed near Wittering, Chichester. The airplane “was completely wrecked.” Haynes was killed. Kemp was seriously injured and had no memory of the day.
The Accidents Investigation Committee of the Royal Aero Club was “of the opinion that there is no positive evidence to show why the accident occurred, but such evidence as is available points to the conclusion that the most probable cause was that the pilot’s foot slipped over the rudder bar, and that he thus lost control.” ²
After another redesign, the first production variant of de Havilland’s biplane was the F.E.2A, a three-bay biplane with a water-cooled Green six-cylinder inline engine, rated at 100 horsepower. This airplane was 32 feet, 3 inches (10.135 meters) long, with a wingspan of 47 feet, 8 inches (14.529 meters). The chord was decreased to 5 feet, 6 inches (1.676 meters). The F.E.2A’s gross weight was 2,680 pounds (1,216 kilograms). It had a maximum speed of 75 miles per hour (121 kilometers per hour) and ceiling of 6,000 feet (1,829 meters). Twelve F.E.2As were built.
Modified for a 120 horsepower Beardmore 6-cylinder engine with a 9-foot-diameter propeller (2.7 meters), the airplane was designated F.E.2B, or Fighter Mark I. The wingspan increased 1 inch to 47 feet, 9 inches (14.554 meters). The airplane had an overall height of 12 feet, 7½ inches (3.848 meters). The wings had a 3° 30′ angle of incidence and were not staggered. There was 4° dihedral. Gross weight increased to 2,827 pounds (1,282 kilograms). Its maximum speed was 73 miles per hour (117 kilometers per hour), and the service ceiling was 9,000 feet (2,743 meters). These were first used in France during World War I.
The B.E.2B was also built with a 160 horsepower Beardmore engine. The series continued with the F.E.2C and a Rolls-Royce powered F.E.2D. Dimensions remained constant, though the angle of incidence was increased to 4°.
The F.E.2 and F.E.2.A were armed with Maxim machine guns. The B.E.2B and later models had one or two .303-caliber Lewis guns.
A total of 1,939 F.E.s were built.
Three-view illustration of the Royal Aircraft Factory F.E.2B, Fighter Mark I. (FLIGHT and Aircraft Engineer, No. 2290, Vol. LXII, Friday, 12 December 1952, at Page 726)
The Royal Flying Corps initially used the F.E.2 (most sources say that “F.E.” stood for Farnham Experimental, ³ meaning that it was a pusher configuration) as a scouting and reconnaissance airplane.
On 16 October 1912, Geoffrey de Havilland was appointed Second Lieutenant (on probation), Royal Flying Corps, Military Wing, antedated to 2 September 1912. He was promoted to Lieutenant, 5 August 1914. Captain de Havilland was appointed Officer of the Most Excellent Order of the British Empire (O.B.E.), 7 June 1918. He was awarded the Air Force Cross, 1 January 1919.
De Havilland soon founded his own aircraft design and manufacturing company, the de Havilland Aircraft Company. He would later be known as Captain Sir Geoffrey de Havilland, O.M., C.B.E., A.F.C., R.D.I., F.R.Ae.S.
¹ Many sources, including The Peerage, Person Page – 55358, identify Sir Geoffrey as “Geoffrey Raoul de Havilland.” As his son is known as Geoffrey Raoul de Havilland, Jr., that would seem reasonable, and may even be correct. However, his birth registration (England & Wales Civil Registration Birth Index, January, February, and March 1883, at Page 149, Column 1), marriage banns and certificates for both marriages, numerous announcements in The London Gazette, contemporary news articles, and his civil death registration do not include any middle name.
² Accidents Investigation Committee of the Royal Aero Club, Report No. 26
³ “Fighting Experimental” —J.M. Bruce, M.A., in Flight, No. 2290, Vol. LXII, Friday, 12 December 1952 at Page 728
Prototype Northrop XF-89, 46-678, parked on the dry lake bed at Muroc Air Force Base. (U.S. Air Force)
16 August 1948: The prototype Northrop XF-89 all-weather interceptor, 46-678, made its first flight at Muroc Air Force Base (later, Edwards Air Force Base). Company test pilot Fred Charles Bretcher, Jr., was at the controls.
The Northrop XF-89 was a two-place, twin-engine, mid-wing monoplane with retractable tricycle landing gear, designed as an all-weather interceptor. The pilot and radar intercept officer sat in tandem in the pressurized cockpit. Similar to Northrop’s World War II-era P-61 Black Widow night fighter, the XF-89 was painted gloss black.
Northrop XF-89 prototype, 46-678, near Edwards Air Force Base, California. (U.S. Air Force)
The XF-89 was 50 feet, 6 inches (15.392 meters) long, with a wingspan of 52 feet, 0 inches (15.847 meters). The wing had a 1.5° angle of incident, and1° dihedral. The total wing area was 606.2 square feet (56.32 square meters). The prototype had an empty weight of 23,010 pounds (10,437 kilograms), gross weight of 31,000 pounds (14,061 kilograms), and maximum takeoff weight of 43,000 pounds (19,505 kilograms).
The XF-89 was powered by two Allison J35-A-9 single-spool, axial-flow turbojet engines. The J35 had an 11-stage compressor section and single-stage turbine. The J35-A-9 was rated at 3,750 pounds of thrust (16.68 kilonewtons). The engine was 12 feet, 1.0 inches (3.683 meters) long, 3 feet, 4.0 inches (1.016 meters) in diameter, and weighed 2,455 pounds (1,114 kilograms).
Northrop XF-89 46-678. (U.S. Air Force)
The prototype crashed during a demonstration flight, its 102nd, at Hawthorne Airport, 22 February 1950. Vibrations caused by the engines’ exhaust caused the tail to separate. The pilot, Charles Tucker, escaped, but flight test engineer Arthur Turton was killed.
The F-89 went into production as the F-89A Scorpion. 1,050 were produced in eight variants. The final series, F-89J, remained in service with the Air National Guard until 1969.
Northrop F-89J Scorpion 53-2509 (converted from F-89D-55-NO) at the National Museum of the United States Air Force. The interceptor is carrying two AIR-2 Genie rockets on its underwing pylons. (U.S. Air Force)
Fred Charles Bretcher, Jr., was born 22 September 1920, at Cincinnati, Ohio. He was the son of Fred Charles Bretcher, a pharmacist, and Frieda Juliana Emma Poggenbeck Bretcher. His father, Sergeant Bretcher (or Bretscher), had served in an ambulance company at Ypres and the Meuse-Argonne during World War I, and had been honorably discharged, 18 April 1919.
The younger Bretcher attended Western Hills High School in Cincinnati. He played with the golf team and worked on the school newspaper. Bretcher graduated in 1938. He then worked as a sales clerk while attending college.
Bretcher enlisted as an aviation cadet in the U.S. Army Air Corps at Fort Thomas, Kentucky, 29 May 1941. He was sent to the Southeast Air Corps Training Center, Maxwell Field, Alabama, as a member of Class 42A. He graduated 8 January 1942, and was released from his enlistment to accept a commission as a second lieutenant, effective 9 January 1942. Lieutenant Bretcher was then assigned to Wright Field, Ohio, as a trainee test pilot. While at Wright, he flew every aircraft in the Air Corps inventory.
Lieutenant Bretcher flew combat missions in the European Theater in the Curtiss-Wright P-40 Warhawk, Republic P-47 Thunderbolt and North American P-51 Mustang. Temporarily assigned to the Royal Air Force, he flew the Supermarine Spitfire and Hawker Tempest fighters and the Avro Lancaster long-range heavy bomber. While serving in Europe, Bretcher was promoted to the rank of captain.
Captain Bretcher returned to Wright Field in May 1944. Promoted to major, he was assigned as the Chief of the Bomber Test Section, working on the Boeing B-29 Superfortress and Consolidated B-32 Dominator heavy bomber projects.
Major Bretcher also flew at Muroc Army Airfield in California, testing the Bell YP-59 Airacomet, Lockheed YP-80A Shooting Star, and the experimental Northrop N-9M flying wing proof-of-concept airplane. Major Bretcher was released from active duty, 13 January 1946.
Fred Charles Bretcher, Jr.
Fred Bretscher went to work for the Northrop Corporation, Hawthorne, California, as a civilian test pilot. He flew as co-pilot to Chief Test Pilot Max R. Stanley on the first flight of the Northrop YB-35, 15 May 1948.
In 1950, Bretcher was assigned to the flight test program of Northrop’s N-25 Snark cruise missile (which would be developed into the SM-62 Snark) at Holloman Air Force Base, near Alamogordo, New Mexico.
Bretcher married Miss Jean Taylor at Albuquerque, New Mexico, 18 December 1951. He retired from the Northrop Corporation in 1952.
Fred Charles Bretcher, Jr., died at Sedona, Arizona, 2 June 2004. He was 83 years old.
Commonwealth Aircraft Corporation CA-26 Sabre A94-101 (Royal Australian Air Force)
14 August 1953: Near Avalon Field, Geelong, Victoria, Australia, Flight Lieutenant William H. Scott, Royal Australian Air Force, the 28-year-old Chief Test Pilot of the Government Aircraft Factories, put the new Commonwealth Aircraft Corporation, Pty. Ltd., prototype into shallow dive from 25,000 feet (7,620 meters) over Port Phillip Bay. This was the new airplane’s sixth test flight. Scott passed 670 miles per hour (1,078 kilometers per hour) and broke the “sound barrier.” A triple sonic boom was heard throughout the Melbourne area.
The aircraft was the CA-26 Sabre, A94-101. The Australian-built Sabre had made its first flight 1 August, also with Flt. Lt. Scott in the cockpit. After about a week there were reports of sonic booms in the area around Melbourne.
Commonwealth Aircraft Corporation CA-26 Sabre A94-101 (Royal Australian Air Force)
Based on the highly successful North American Aviation F-86F Sabre, the C.A.C. variant used a license-built Rolls-Royce Avon RA.7 turbojet with 7,350 pounds of thrust. The Sabre’s fuselage had to be extensively redesigned to allow installation of the new engine. Although it was about the same size as the J47 it replaced, the Avon needed a much larger intake duct. And because it weighed less than the J47, it had to be moved aft to maintain the Sabre’s center of gravity. Only about 40% of the original structure remained.
Other changes were replacing the fighter’s basic armament of six .50-caliber Browning machine guns with two 30 mm ADEN revolver cannon. In testing, it was found that the muzzle blast of the ADEN cannons could cause the engine to flame out. “Maxim” shock wave baffles were installed to eliminate the problem.
Commonwealth Aircraft Corporation CA-26 Sabre A94-901. (Royal Australian Air Force)
The aircraft, often called the “Avon Sabre,” was put into production as the CA-27 Sabre Mk 30. Twenty-two aircraft were built in the version. With the introduction of the Mark 31, the original Sabres were upgraded to the new standard. Sixty-nine Sabre Mk 32 fighters were built with the Avon 25 engine and increased fuel capacity.
The CA-27 was in service with the Royal Australian Service from 1954 until 1971. Several were transferred to Malaysia and Indonesia and operated for those countries until 1982.
The prototype CA-26 Sabre, A94-901, flew with several RAAF squadrons, including the 76 Squadron “Black Panthers” Aerobatic Team, 1961–1965. It was withdrawn from service in 1966. The Sabre was restored by Hawker de Havilland at Bankstown Airport, before being sent to the Historical Aircraft Restoration Society Museum (“HARS”) at Illawarra Regional Airport, south of Sydney, New South Wales, Australia. The airplane is again in the livery of the “Black Panthers.”
A94-901 ias it appeared when assigned to 76 Squadron “Black Panthers,” 1961–1965. (HARS Museum)
The prototype Bell 222 hovering in ground effect during its first flight, 13 August 1976. (Bell Helicopter TEXTRON)
13 August 1976: At the Bell Helicopter facility at Arlington, Texas, the prototype Model 222 twin-engine helicopter, registration N9988K, made its first flight. During the 42-minute flight, test pilots Donald Lee Bloom and Louis William Hartwig flew the aircraft through a series of hovering maneuvers and transitions to forward flight. A Bell spokesperson described it as, “One of the most successful prototype flights we’ve ever had.”
The prototype Bell 222 in flight with landing gear retracted, 13 August 1976. (Bell Helicopter TEXTRON)
The Model 222 (“Two Twenty-Two”) was Bell Helicopter’s first completely new helicopter since the Model 206 JetRanger series. Classified as a light twin, the aircraft was originally powered by two Lycoming LTS101-650C-3 turboshaft engines. The two-blade main rotor was similar in design to that used on the AH-1 Cobra attack helicopters. The first four prototypes were built with a T-tail configuration, but problems discovered early in the test program resulted in a change to the arrangement used in the production version.
Bell Model 222 prototype, N9988K, in flight. Note T-tail configuration. (Bell Helicopter TEXTRON)
The Bell 222 is used as an executive transport, a utility transport and an aeromedical helicopter. It can carry a maximum of ten persons, and is operated with either one or two pilots. The 222 is certified for Instrument Flight Rules. The standard aircraft has retractable tricycle landing gear but the Model 222UT replaces that with a lighter weight skid gear.
The Bell Model 222 is 47 feet, 6.16 inches (14.482 meters) long with rotors turning. The helicopter has a maximum height of 14 feet, 7.25 inches (4.451 meters) with the forward main rotor blade against its droop stop. The height from ground level to the top of the vertical fin is 11 feet, 0.56 inches (3.367 meters). The helicopter’s maximum width is 11 feet, 4.0 inches (3.454 meters). The empty weight is 4,555 pounds (2,066 kilograms), and the maximum gross weight is 7,848 pounds (3,560 kilograms).
The fifth prototype Bell 222, N222BX (c/n 47005), in the 40′ × 80′ (12.2 × 24.4 meters) wind tunnel at the NASA Ames Research Center, Moffett Field, California. The man at the lower left corner of the image shows scale. (NASA)
The 222’s main rotor mast is tilted 5° forward and 1° 15′ to the left. This contributes to a higher forward air speed and counteracts the helicopter’s translating tendency in a hover.
The two-bladed, underslung, semi-rigid main rotor system rotates counter-clockwise as seen from above (the advancing blade is on the right.)and turns 324 r.p.m at 100% NR. The main rotor has a diameter of 39 feet, 9.0 inches (12.116 meters). The blades have a chord of 2 feet, 4.6 inches (7.264 meters) and are pre-coned 3° 30′. The two-bladed tail rotor is positioned on the left side of the tail boom and turns clockwise as seen from the helicopter’s left (the advancing blade is below the axis of rotation). The tail rotor’s diameter is 6 feet, 6.0 inches (1.981 meters). The blades’ chord is 10.0 inches (0.254 meters).
The Bell 222 was originally powered by two Lycoming LTS101-650C-3 engines. The LTS101 is a compact, light weight, turboshaft engine. The 2-stage compressor section has 1 axial-flow stage and 1 centrifugal-flow stage. The turbine section has 1 high-pressure gas generator stage and 1 low-pressure free power stage. The LTS101-650C-3 was has a maximum continuous power rating of 598 shaft horsepower (446 kilowatts at 49,159 r.p.m. (N1) at Sea Level, and 630 shaft horsepower (470 kilowatts) at 49,638 r.p.m. for takeoff (5-minute limit). The output shaft (N2) turns 9,545 r.p.m. With one engine inoperative (OEI), the -650C-3 is rated at 650 shaft horsepower (485 kilowatts) at 50,169 r.p.m. (30-minute limit), and a maximum 675 shaft horsepower at 50,548 r.p.m. N1/9,784 r.p.m. N2 (2½-minute limit). The LTS101-650C-3 is 1 foot, 10.6 inches (0.574 meters) in diameter, 2 feet,7.3 inches (0.795 meters) long, and has a dry weight of 241 pounds (109 kilograms).
The Bell 222 has a maximum speed of 130 knots. Its hover ceiling is approximately 9,000 feet (2,743 meters). The service ceiling is 12,800 feet (3,901 meters). The maximum range is 324 nautical miles (373 statute miles/600 kilometers).
During early production, problems were experienced with the LTS101 engines, which were also used on the Sikorsky S-76 and the Aérospatiale AS-350D A-Star. This seriously hurt the reputation and sales of all three helicopters. Bell Helicopter’s parent corporation, Textron, bought the Lycoming factory and modernized it in order to improve the engine. (The engine is now owned by Honeywell Aerospace.) Operators began to replace the two Lycoming engines with a pair of Allison 250-C30 turboshafts, and eventually Bell Helicopter modified the aircraft, marketing it as the Model 230. A four-bladed variant with a longer cabin is called the Model 430.
After the test program was completed, the first prototype, N9988K, was used as a static prop on the popular television series, “Airwolf.”
Bell 222 N34NR, an aeromedical helicopter operated by Air Angels, Inc., Bolingbrooke, Illinois. (Photograph courtesy of Chris Hargreaves)Donald Lee Bloom
Donald Lee Bloom was born in Tulsa, Oklahoma, 23 April 1932. He was the son of Fred Miles Bloom, a telegraph operator for the Standard Oil Company, and Georgia Randolph Bloom.
Don Bloom attended the University of Houston as a Naval Reserve Officers Training Corps (NROTC) midshipman. He graduated in 1955. Bloom was commissioned as a second lieutenant, United States Marine Corps, 15 September 1955. He was assigned to pilot training at NAS Pensacola, Florida.
Lieutenant Bloom was promoted to the rank of first lieutenant, 15 March 1957. He married Miss Anne Marie Carruthers in Los Angeles, California, 5 September 1958. They would have four children, Susan, Stacy, Robert and Todd.
Lieutenant Bloom was released from active duty in 1960, and joined the Kaman Aircraft Corporation as a test pilot. In 1961, began his 29-year career as an experimental test pilot with the Bell Helicopter Company.
The first production Bell OH-58A-BF Kiowa, 68-16687. Don Bloom flight-tested this type in his investigation of Loss of Tail Rotor Effectiveness. (U.S. Army)
In 1984 the Society of Experimental Test Pilots gave its Iven C. Kincheloe Award to Don Bloom for his experimental research into the Loss of Tail Rotor Effectiveness (LTE).
After flying as a test pilot on 187 projects, Don Bloom retired from the Bell Helicopter Corporation in 1990 as Senior Experimental Test Pilot. He then worked for the Federal Aviation Administration Southwest Region as its Designated Engineering Representative Flight Test Pilot, testing aircraft for government certification. During his aviation career, Bloom flew over 14,000 hours in 102 different aircraft.
In 2011, the Federal Aviation Administration presented its Wright Brothers Master Pilot Award to Don Bloom.
Donald Lee Bloom died 18 July 2017 at Grapevine, Texas. He was buried at the Dallas-Fort Worth National Cemetery, Dallas, Texas.
Don Bloom was a project development test pilot for the Bell AH-1G Cobra. (U.S. Army)
Louis William Hartwig was born at Sherman, Iowa, 26 July 1922. He was the son of Lawrence C. Harwig and Alta May Gaughey Hartwig. He attended Bowie High Schoo in Bowie, Texas.
Lou Hartwig enlisted in the United States Army 8 September 1942. (s/n 17119277) He was assigned to the 304th and 902nd Field Artillery Battalions, 77th Infantry Division.
Lou Hartwig married Miss Katherine Elizabeth Healzer, a school teacher, at Rustburg, Virginia, 19 February 1944. They would have a son, Ronald.
Piper L-4 Grasshopper. (Harry S. Truman Library & Museum)
Hartwig was deployed to the Pacific theater of operations, 24 March 1944. He flew a Piper L-4 Grasshopper as an artillery spotter at Guam and Okinawa. He was discharged from his enlistment 18 June 1944, and commissioned a second lieutenant, 19 June 1944 (s/n O-1821011). Lieutenant Hartwig returned to the United States on 21 November 1945. He was released from active duty 24 January 1946.
Lou Hartwig was one of the early students of the Bell Aircraft Corporation’s helicopter flight school at Niagara Falls Airport, New York. The school was for experienced pilots only, and required 10–15 days to complete. Each student received a minimum 22½ flight hours in a Bell Model 47. The cost of the course was $600. Hartwig was then employed as an agriculture “crop dusting” pilot in California.
While spraying insecticide in a field near Sacramento, California, Hartwig was overcome by the poisonous chemicals and lost consciousness. The helicopter struck power lines and crashed. Hartwig was thrown from the cockpit. Crash investigators described the accident as “unsurvivable.” He spent the next 11 months in hospital.
Lou Hartwig was a test pilot for the U.S. Navy’s HSL-1 ASW helicopter. (Bell Aircraft Corporation)
The Bell Helicopter Company hired Hartwig as a test pilot on 15 February 1955. One of his first projects was flight testing the Model 61, the only tandem rotor helicopter ever produced by Bell. It was used as an anti-submarine warfare helicopter by the U.S. Navy, designated HSL-1.
On 31 January 1961, Hartwig set a Fédération Aéronautique Internationale (FAI) World Record for Speed Over a Closed Circuit of 100 Kilometers Without Payload, when he flew a Bell Model 47J Ranger at an average speed of 168.36 kilometer per hour (104.61 miles per hour).¹
On 2 February 1961, Lou Hartwig flew a Bell Model 47G, N967B, to set three more FAI world records: Distance in a Closed Circuit Without Landing, 1,016.20 kilometers (631.44 miles); ² Speed Over a Closed Circuit of 500 Kilometers Without Payload, averaging 119.07 kilometers per hour (73.99 miles per hour); ³ and Speed Over a Closed Circuit of 1,000 Kilometers, 118.06 kilometers per hour (73.36 miles per hour.⁴ The Model 47G had been modified with an additional fuel tank from the earlier Model 47D-1, and curved landing skids from the Model 47J.
The Bell 533, 56-6723, in one of its many configurations. It was flown with two- and four-bladed main rotors, with and without wings, and with and without turbojet engines. (Bell Helicopter Corporation)
Lou Hartwig worked on the U.S. Army’s High Performance Helicopter project. A pre-production YH-40 Iroquois, serial number 56-6723, was modified into a winged and compound helicopter configuration, designated Model 533. Hartwig flew the helicopter to a speed of 274.6 knots (316.00 statute miles per hour/508.56 kilometers per hour). In 1971, the Vertical Flight Society gave its Frederick L. Feinberg Award to Hartwig.
Mrs. Hartwig died 10 February 1989, in San Diego, California. Lou Hartwig married his second wife, Joanne Dunning, in 1990.
Louis William Hartwig died 12 April 2016, at the age of 93 years. He was buried at the Dearborn Memorial Park, Poway, California.
Bell XP-39 Airacobra 38-326 in the NACA Full Scale Wind Tunnel at Langley Field, Virginia, 9 August 1939. The man at the base of the supports shows scale. (NASA)
9 August 1939: After General Henry H. Arnold had ordered that the prototype Bell Aircraft Corporation XP-39 Airacobra be evaluated in the National Advisory Committee for Aeronautics (NACA) Full-Scale Tunnel at the Langley Memorial Aeronautics Laboratory, Langley Field, Virginia, it was flown there from Wright Field. It was hoped that aerodynamic improvements would allow the prototype to exceed 400 miles per hour (644 kilometers per hour).
NACA engineers placed the full-size airplane inside the large wind tunnel for testing. A number of specific areas for aerodynamic improvement were found. After those changes were made by Bell, the XP-39’s top speed had improved by 16%.
Bell XP-39 Airacobra 38-326 in the NACA Langley Memorial Aeronautical Laboratory Full-Scale Wind Tunnel, Langley Field, Virginia, 9 August 1939. The fuselage has had all protrusions removed. Right profile. (National Aeronautics and Space Administration NACA 18423)
The Bell XP-39 Airacobra was a single-place, single-engine prototype fighter with a low wing and retractable tricycle landing gears. The airplane was primarily built of aluminum, though control surfaces were fabric covered.
As originally built, the XP-39 was 28 feet, 8 inches (8.738 meters) long with a wingspan of 35 feet, 10 inches (10.922 meters). The prototype had an empty weight of 3,995 pounds (1,812 kilograms) and gross weight of 5,550 pounds (2,517 kilograms). Changes recommended by NACA resulted in a recontoured canopy, lengthened the airplane to 29 feet, 9 inches (9.068 meters) and reduced the wing span to 34 feet, 0 inches (10.362 meters). Its empty weight increased to 4,530 pounds (2,055 kilograms) and gross weight to 5,834 pounds (2,646 kilograms).
Bell XP-39 Airacobra 38-326 in the NACA wind tunnel at Langley Field. The man at the base of the supports shows scale. (NASA)
The XP-39 was unarmed, but it had been designed around the American Armament Corporation T9 37 mm autocannon, later designated Gun, Automatic, 37 mm, M4 (Aircraft). The cannon and ammunition were in the forward fuselage, above the engine driveshaft. The gun fired through the reduction gear box and propeller hub.
The XP-39 was originally powered by a liquid-cooled, turbosupercharged and supercharged 1,710.597-cubic-inch-displacement (28.032 liter) Allison Engineering Co. V-1710-E2 (V-1710-17), a single overhead cam (SOHC) 60° V-12 engine with a compression ratio of 6.65:1. The V-1710-17 had a Maximum Continuous Power rating of 1,000 horsepower at 2,600 r.p.m. at 25,000 feet (7,620 meters), and Takeoff/Military Power rating of 1,150 horsepower at 3,000 r.p.m. at 25,000 feet, burning 91 octane gasoline. The engine was installed in an unusual configuration behind the cockpit, with a two-piece drive shaft passing under the cockpit and turning the three-bladed Curtiss Electric constant-speed propeller through a remotely-mounted 1.8:1 gear reduction gear box. The V-1710-17 was 16 feet, 1.79 inches (4.922 meters) long, including the drive shaft and remote gear box. It was 2 feet, 11.45 inches (0.900 meters) high, 2 feet, 5.28 inches (0.744 meters) wide and weighed 1,350 pounds (612 kilograms).
Bell XP-39B prototype, s/n 38-326, at Bell Aircraft Co., Buffalo, New York
Army Air Corps strategy changed the role of the P-39 from a high-altitude interceptor to a low-altitude tactical strike fighter. The original turbocharged V-1710-17 was replaced with a V-1710-37 (V-1710-E5) engine. The turbosupercharger had been removed, which reduced the airplane’s power at altitudes above 15,000 feet (4,572 meters). The V-1710-37 had a maximum power of 1,090 horsepower at 3,000 r.p.m. at 13,300 feet (4,054 meters). With the NACA-recommended aerodynamic changes and the new engine, the prototype Airacobra was redesignated XP-39B.
A Bell P-39 Airacobra fires all of its guns at night. (U.S. Air Force)
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