Tag Archives: First Flight

13 August 1976

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 prototypye, N9988K, in flight. Note T-tail configuration. (Bell Helicopter)
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 Bell 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.

¹ FAI Record File Number 986

² FAI Record File Number 983

³ FAI Record File Number 989

⁴ FAI Record File Number 990

© 2018, Bryan R. Swopes

9 August 1884

Photo prise par l’observatoire de Meudon.par l’astronome Jules Janssen.

9 August 1884: At the parade grounds at Chalais-Meudon, a town on the banks of the Seine near Paris, France, engineers Charles Renard and Arthur Constantin Krebs made the first controllable free flight when they piloted their airship, La France, over an approximately 4¾ mile (7.6 kilometers) course and returned to their starting point. The airship completed the circuit in 20 minutes at an average speed of 15.75 feet per second (10.74 miles per hour, or 17.28 kilometers per hour).

Track of La France, 9 August 1884

Charles Renard later said,

“As soon as we had reached the top of the wooden plateaus which surrounded the valley of Chalais we started the screw, and had the satisfaction off seeing the balloon immediately obey it, and readily follow ever turn of the rudder. We felt we were absolutely masters of our own movements, and that we could traverse the atmosphere in any direction as easily as a steam launch could make its evolutions on a calm lake. After having accomplished our purpose we turned our head toward the point of departure, and we soon saw it approaching us. The walls of the park of Chalais were passed anew, and our landing appeared at our feet about 1,00 feet below the car. The screw was then slowed down, and at a pull of the safety valve started the descent, during which, by means of the propeller and rudder, the balloon was maintained directly over the point where our assistants awaited us. Everything occurred according to our plan, and the car was soon resting quietly upon the lawn from which we had started.”

The Practical Engineer, Volume 9, Number 371, Friday, 6 April 1894, Page 266, Column 1

From 9 August 1884 to 23 September 1885, La France made seven flights and was able to return to its starting point five times. On its final flight, it reached an average speed of 21.33 feet per second (14.54 miles per hour, or 23.40 kilometers per hour).

Plan de l’enclos de l’étang de Chalais et de ses dépendances. (Bibliothèque nationale de France)

La France was a powered, steerable, gas balloon, approximately 167 feet long (50.9 meters) and 27½ feet (8.4 meters) in diameter. Buoyancy was provided by 65,000 cubic feet (1,841 cubic meters) of hydrogen.

Under the balloon envelope hung a 108 foot (32.9 meter) long gondola made of bamboo and covered with silk. This was where the airmen and any passengers, the 8½ horsepower (6.25 kilowatts) electric motor and a chromium chloride storage battery were placed. The motor weighed 220.5 pounds (100 kilograms), and the battery, 580 pounds (263 kilograms.)

At the forward end of the gondola was a four-bladed wooden propeller with a 23-foot (7.0 meters) diameter and 28-foot (2.4 meters) pitch, providing thrust to drive the airship. The propeller was driven by a 49 foot (14.9 meters) drive shaft. On the 9 August flight, the propeller turned 42 r.p.m. On later flights, this was increased to a maximum 57 r.p.m.

La France was controlled by a rudder and elevator. A sliding weight allowed for changes in the center of gravity.

Drawing of le dirigeable ballon La France de Charles Renard et Arthur Krebs.

La France was designed and built by Captain Paul Renard, Captain Charles Renard and Captain Arthur Constantin Krebs, all officers of the French Armée de Terre Corps du Génie (Corps of Engineers) at the central military aeronautics establishment at Chalais-Meudon.

Charles Renard

Charles Renard was born at Damblain, Viosges, France, 23 November 1847. In 1873, he had developed an unmanned glider which was controlled by a pendulum device linked to its control surfaces. The glider was flown from a tower at Arras.

Renard also developed the powered Renard Road Train, in which the trailers were powered by drive shafts from the forward power car, and each car was steered through a system of linkages attached to the car ahead of it. He also developed the concept of preferred numbers. (ISO 3)¹

Charles Renard remained in charge of the aeronautical establishment at Chalais-Meudon until his death. He committed suicide, 13 April 1905.

Arthur Constantin Krebs was born 16 November 1850 at Vesoul, France.

Arthur Constantin Krebs

Krebs was a prolific inventor. Following his work with La France, he completed the development of Gymnote (Q1), the world’s first all-electric submarine. His work on automobiles was extensive. He developed the concept of the front engine/rear wheel drive (Systeme Panhard); engine balancing; caster in the steering and suspension system, which allowed the steering wheels to self-center; the steering wheel; shock absorbers; four-wheel drive and four-wheel steering, etc. He invented the electric brake dynomometer which is used to measure power output of engines.

Arthur Krebs died 22 March 1935.

Airship La France at Hangar Y, Chalais-Meudon, circa 1885. (NASM)

¹ “Preferred numbers were first utilized in France at the end of the nineteenth century. From 1877 to 1879, Captain Charles Renard, an officer in the engineer corps, made a rational study of the elements necessary in the construction of lighter-than-air aircraft. He computed the specifications for cotton rope according to a grading system, such that this element could be produced in advance without prejudice to the installations where such rope was subsequently to be utilized. Recognizing the advantage to be derived from the geometrical progression, he adopted, as a basis, a rope having a mass of a grams per metre, and as a grading system, a rule that would yield a tenth multiple of the value a after every fifth step of the series. . . .”

ISO 17:1973, International Organization for Standardization

© 2017, Bryan R. Swopes

8 August 1946

Convair XB-36 Peacemaker 42-13570 engine run-up
The prototype Consolidated-Vultee XB-36, 42-13570, stands at the end of the runway with all six engines running. (U.S. Air Force)

8 August 1946: At Fort Worth, Texas, the Consolidated-Vultee Aircraft Corporation XB-36 prototype, 42-13570, made its first flight. Convair test pilots Beryl Arthur Erickson and G.S. “Gus” Green, along with Chief Flight Test Engineer James D. “J.D.” McEachern, were in the cockpit. Six other crew members were aboard.

Chief Test Pilot Beryl Arthur Erickson. (Convair)

In a 1992 interview published in Code One Magazine, Erickson said that he and his crew had been ready to take off at 5 a.m., but they didn’t get their release until noon. The Texas summer temperature was 100 degrees (37.8 °C.), but inside the cockpit, the temperature was 140° F. (60 °C.) The engines were overheating and the oil pressure was low. When they pushed the throttles forward, the XB-36 accelerated smoothly and lifted off at 110 knots (126.6 miles per hour, 203.7 kilometers per hour). The retired test pilot said, “The XB-36 controlled nicely in the takeoff run and in the transition to steady climb. We flew conservatively with the gear down. The flight was uneventful and lasted thirty-eight minutes.”

Chief Test Pilot Beryl Arthur Erickson at the aircraft commander’s station of the Consolidated-Vultee XB-36 long-range heavy bomber. (Code One).

The B-36 was the largest and heaviest airplane built up to that time. It was designed as a long-range heavy bomber, able to reach targets on the European continent from the United States and return, should England fall to Nazi Germany during World War II. With the end of the war, its purpose was changed to that of a long range strategic bomber, carrying large nuclear weapons that weren’t even imagined when the design process had begun.

A size comparison between the Convair XB-36 prototype and a Boeing B-29 Superfortress.
A size comparison between a Boeing B-29-55-BA Superfortress, 44-84017, and the Consolidated-Vultee XB-36 prototype, Carswell AFB, June 1948. (U.S. Air Force Historical Research Agency)

The XB-36 was 162 feet, ½ inch (49.390 meters) long with a wing span of 230 feet (70.104 meters), nearly 90 feet longer than that of the B-29 Superfortress that it would replace. Its height was 46 feet, 9-7/8 inches (14.272 meters) to the tip of the vertical fin. The wings’ leading edges were swept aft 15° 5′ 39″, and the trailing edges, 3°. They had 2° dihedral. The wings’ angle of incidence was 3° and they incorporated 2° of negative twist. The total wing area was 4,772 square feet (443.33 square meters). The prototype’s empty weight was 131,240 pounds (59,530 kilograms), and it had a maximum gross weight of 274,929 pounds (124,706 kilograms).

Convair XB-36 three-view illustration with dimensions. (U.S. Air Force)

The XB-36 was powered by six air-cooled, supercharged, 4,362.49 cubic-inch-displacement (71.489 liter) Pratt & Whitney Wasp Major TSB1P-G (R-4360-25) 28-cylinder four-row radial engines, with a normal power rating of 2,500 horsepower at 2,550 r.p.m. to 5,000 feet (1,524 meters), and 3,000 horsepower at 2,700 r.p.m. for takeoff. They were mounted inside the wings. The engines were arranged in a “pusher” configuration with intake and cooling air entering through inlets in the wing leading edge. They drove three-bladed Curtiss propellers with a diameter of 19 feet (5.8 meters) through a 0.381:1 gear reduction. The R-4360-25 was 9 feet, 1.75 inches (2.788 meters) long, 4 feet, 4.50 inches (1.334 meters) in diameter, and weighed 3,483 pounds (1,580 kilograms).

The airplane’s estimated maximum speed was 347 miles per hour (558 kilometers per hour) at 35,000 feet (10,668 meters) and the cruising speed, 216 miles per hour (348 kilometers per hour). The service ceiling was predicted at 36,080 feet (10,997 meters) with all six engines running. It had an estimated range of 9,430 miles (15,176 kilometers) with a 10,000 pound (4,536 kilogram) bomb load.

The prototype Convair XB-36, 42-13570, lifts off the runway at Fort Worth, Texas. (U.S. Air Force)
The prototype Consolidated-Vultee XB-36, 42-13570, lifts off the runway at Fort Worth, Texas. (U.S. Air Force)

The bomber was designed to carry a maximum bomb load of 72,000 pounds (32,659 kilograms): as many as 132 500-pound bombs; 72 1,000 pound; 44 1,600 pound; 28 2,000-pound; or 12 4,000-pounders. Defensive armament was planned as two 37mm cannon in each of the forward upper and lower turrets, with 100 rounds of ammunition per gun; four .50-caliber machine guns in the rear upper and lower turrets with 1,000 rounds per gun; and one 37 mm cannon and two .50-caliber machine guns in the tail. The tail cannon would have 300 rounds, and the machine guns, 1,000 rounds per gun.

After testing, improvements were incorporated into the second prototype, YB-36 42-13571. In June 1948, the XB-36 was modified with R-4360-41 engines, and the main landing gear was changed from a single-wheel design to a 4-wheel bogie. With these and other changes the XB-36 was redesignated YB-36A. It was used for continued testing for the next several years, but was eventually stripped of its engines and equipment and used for firefighter training at the adjacent Carswell Air Force Base.

The YB-36 was selected for production as the B-36A Peacemaker. The B-36 series was produced in both bomber and reconnaissance versions and was in front line service from 1949 to 1959. Beginning with the B-36D, four turbojet engines were mounted beneath the wings in pods similar to those on the Boeing B-47 Stratojet, greatly increasing the bomber’s performance. A total of 384 were built. Only five still exist. The Peacemaker was never used in combat.

The Convair XB-36 in flight. (U.S. Air Force)
The Consolidated-Vultee XB-36 prototype, 42-13570, in flight. (U.S. Air Force)

© 2023, Bryan R. Swopes

7 August 1963

The first Lockheed YF-12A interceptor, 60-6934, flown by James D. Eastham, lands at Groom Lake, Nevada, after its first flight, 7 August 1963. (U.S. Air Force)
James D. Eastham
James D. Eastham (1918–2016)

7 August 1963: The first Lockheed YF-12A interceptor, 60-6934, took off from a top secret air base at Groom Lake, Nevada, on its first flight. Lockheed test pilot James D. Eastham was at the controls.

Three YF-12A prototypes s were built. They were Mach 3+ interceptors developed from the Central Intelligence Agency “Oxcart” Lockheed A-12 reconnaissance airplane.

The interceptors were equipped with a very effective Hughes fire control system and armed with three Hughes AIM-47 Falcon air-to-air missiles. In 1965 the U.S. Air Force placed an order for 93 F-12B interceptors for the Air Defense Command, but Secretary of Defense Robert McNamara continually refused to release the funds which Congress had appropriated. Eventually the contract was cancelled.

In testing, a YF-12A launched a Falcon missile while flying at Mach 3.2 at 74,000 feet (22,555 meters). It successfully intercepted and destroyed a target drone flying at only 500 feet (152 meters).

Lockheed YF-12A 60-6934 at Groom Lake, Nevada. (Central Intelligence Agency via Burbank Aviation Museum)

On 1 May 1965, YF-12A 60-6936, flown by Colonel Robert L. Stephens and Lieutenant Colonel David Andre, set a world speed record of 2,070.101 miles per hour (3,331.505 kilometers per hour) and a sustained altitude record of 80,257.86 feet (22,677 meters).

Lockheed YF-12A 60-6934 in flight. (U.S. Air Force)
Lockheed YF-12A 60-6934 in flight. (U.S. Air Force)

60-6934 was damaged beyond repair in a runway accident at Edwards Air Force Base, 14 August 1966. Part of the airplane was salvaged and used to construct the only SR-71C, 64-17981, a two-seat trainer. The third YF-12A, 60-6936, was destroyed when the crew ejected during an inflight fire near Edwards AFB, 24 June 1971. The only remaining YF-12A, 60-6935, is in the collection of the National Museum of the United States Air Force, Wright-Patterson AFB, Ohio.

Lockheed YF-12A 60-6934. (U.S. Air Force)
Lockheed YF-12A 60-6934. (U.S. Air Force)
Clarence L. (“Kelly”) Johnson, Director of Lockheed’s Advanced Development Projects (“the Skunk Works”) with the first YF-12A interceptor, 60-6934. (Lockheed Martin)

© 2017, Bryan R. Swopes

7 August 1941

A prototype Grumman XTBF-1 torpedo bomber. (Ray Crupi Collection)

7 August 1941: Grumman Aircraft Engineering Corporation chief engineer and test pilot, Robert Leicester (“Bob”) Hall, took the XTBF-1, a prototype torpedo bomber, for its first flight. He quickly returned to the airfield. The airplane was seriously over-weight, its center of gravity was too far aft, and it was unstable in the yaw axis.

The first XTBF-1, U.S. Navy Bureau of Aeronautics serial number (“Bu. No.”) 00373, was modified to correct these faults. The engine mount was revised, moving the engine farther forward. A triangular fillet was added to the top of the fuselage in front of the vertical fin, and the weight was reduced.

Grumman XTBF-1 Bu.No. 00373. Note the dorsal fillet. (Northrop Grumman)

On 28 June 1942, 00373 caught fire during a test flight. Its crew safely bailed out but the prototype was destroyed.

The second prototype XTBF-1 was sent to the National Advisory Committee for Aeronautics Langley Memorial Aeronautical Laboratory at Hampton, Virginia, for testing in the 30- × 60-foot Full Scale Tunnel.

The second Grumman XTBF-1 prototype in the NACA Full Scale Tunnel. (NASA)

Before the airplane’s first flight, the U.S. Navy had ordered 286 production aircraft. In October 1941, the type was officially named “Avenger.” The first production airplane, Bu. No. 000393, made its first flight on 15 December 1941.

A flight crew boards a Grumman TBF-1 Avenger torpedo bomber, circa late 1941–early 1942. (Rudy Arnold Collection, Smithsonian Institution, National Air and Space Museum NASM-XRA-0780)

The Grumman Model 40, designated TBF-1 Avenger by the United States Navy, was a single engine torpedo bomber designed to operate from aircraft carriers. Initially it had a four-man crew: pilot, navigator, radio-operator/gunner and ball turret gunner. The TBF was 40 feet, 11½ inches (12.484 meters) long with a wingspan of 54 feet, 2 inches (16.510 meters) and height of 16 feet, 4¼ inches (4.991 meters).

Grumman TBF Avenger three-view illustration with dimensions. (U.S. Navy)

The XTBF-1 was powered by an air-cooled, supercharged, 2,603.943-cubic-inch-displacement (42.671 liters) Wright Cyclone 14 GR2600B698 (R-2600-8) two-row, fourteen-cylinder radial engine with a compression ratio of 6.9:1. The R-2600-8 was rated at 1,500 horsepower at 2,400 r.p.m., and 1,700 horsepower at 2,800 r.p.m. at Sea Level for Takeoff. The engine drove a 13 foot, 1 inch diameter ( meters), three-bladed Hamilton Standard constant speed propeller through a  0.5625:1 gear reduction unit. The R-2600-8 was 5 feet, 4.91 inches (1.649 meters) long, 4 feet, 6.26 inches (1.378 meters) in diameter, and weighed 1,995 pounds (904.9 kilograms).

A Grumman TBF-1 Avenger, mid-1942. (Hans Groenhoff Collection, Smithsonian Institution, National Air and Space Museum NASM-HGC-906)

© 2020, Bryan R. Swopes