Martin YB-10 (Model 139), 33-140. (U.S. Air Force)
27 November 1933: The United States Army Air Corps accepted the Glenn L. Martin Company’s first service test YB-10 bomber, serial number 33-140. This was the first all-metal monoplane bomber with an internal bomb bay, retractable landing gear, rotating gun turret and enclosed cockpit. It flew faster than pursuit aircraft of the day.
The prototype Martin Model 123 (XB-907) in flight, 1932. (U.S. Air Force)
There had been a single prototype, the Martin Model 123. It was powered by two Wright R-1820-19 engines rated at 600 horsepower, each. This was designated XB-907 by the U.S. Army Air Corps when tested at Wright Field in 1932. Recommendations for modifications were made, and Martin upgraded the prototype to the XB-907A configuration, which was then designated XB-10 by the Air Corps. The Army then ordered 48 production airplanes.
Martin XB-907A (XB-10 33-139). (U.S. Air Force)
The first group of 14 airplanes were designated YB-10. The YB-10 (Martin Model 139) had enclosed canopies for the pilot and top gunner, and a nose turret. The crew consisted of a pilot, radio operator and three gunners.
These airplanes were powered by two air-cooled, supercharged, 1,823.129-cubic-inch-displacement (29.876 liter) Wright Cyclone SGR-1820-F2 (R-1820-25) 9-cylinder radial engines with a compression ratio of 6.4:1, which were rated at 750 horsepower at 1,950 r.p.m. at Sea Level. The engines turned three-bladed Hamilton Standard adjustable-pitch propellers through a 16:11 gear reduction. The R-1820-25 was 3 feet, 11–13/16 inches (1.214 meters) long, 4 feet, 5-¾ inches (1.365 meters) in diameter, and weighed 1,047 pounds (475 kilograms).
Martin YB-10. (U.S. Air Force)Martin YB-10 at Wright Field, 1933. (U.S. Air Force)Martin XB-907, left profile. (U.S. Air Force)Martin YB-10, left profile. (U.S. Air Force)Martin YB-10, right rear quarter view. (U.S. Air Force)
The bomber could carry two 1,130 pound (513 kilogram) bombs, or five 300 pound (136 kilogram) bombs in its internal bomb bay. Alternatively, a 2,000 pound (907 kilogram) bomb could be carried externally. There were three .30-caliber (7.62 mm) Browning M1919 machine guns for defense.
Martin B-10B in flight. (U.S. Air Force)
The first full scale production version was the B-10B, which was very similar to the service test YB-10s. These airplanes were 44 feet, 9 inches (13.640 meters) long with a wingspan of 70 feet, 6 inches (21.488 meters) and height of 15 feet, 5 inches (4.670 meters). The B-10B had an empty weight of 9,681 pounds (4,391 kilograms).
The engines installed in this variant were Wright Cyclone SGR-1820-F3 (R-1820-33), rated at 700 horsepower at 1,950 r.p.m. at Sea Level. Dimensions, weight and propeller gear reduction for this engine are the same as the R-1820-25, above.
The B-10B had a cruising speed of 193 miles per hour (311 kilometers per hour), and maximum speed of 213 miles per hour (343 kilometers per hour) at 10,000 feet (3,048 meters).
33-140 was converted to a B-10M for towing aerial targets and was assigned to the Tow Target Detachment at March Field, Riverside, California. Piloted by Robert E. Phillips, 33-140 was damaged in a taxiing accident, 8 April 1942.
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 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)
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)
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)
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.
Pan American Airways’ Martin M-130 flying boat, China Clipper (NC14716), leaving the Golden Gate enroute to Honolulu, 22 November 1935. Photographed by Clyde Herwood Sunderland, Jr. (1900–1989).
22 November 1935: The Pan American Airways flying boat, China Clipper, a Martin M-130, NC14716, departed Alameda, California (an island in San Francisco Bay) at 3:46 p.m., Friday, and arrived at Honolulu at 10:39 a.m., Saturday, completing the first leg of a five-day trans-Pacific flight to Manila in the Philippine Islands.
The aircraft commander was Captain Edwin Charles Musick, with First Officer Robert Oliver Daniel (“Rod”) Sullivan. The navigator was Frederick Joseph Noonan, who would later accompany Amelia Earhart on her around-the-world flight attempt. There were also a Second Officer and two Flight Engineers. The cargo consisted of 110,000 pieces of U.S. Mail.
Captain Edwin Musick and R.O.D. Sullivan, at the center of the image, next to the China Clipper before leaving San Francisco Bay with the first transpacific airmail, 22 November 1935. The three men at the right of the image are (left to right) Postmaster General James Farley; Assistant Postmaster General Harllee Branch; and Pan American Airways’ President Juan Trippe.
Pan Am personnel called the Clipper “Sweet Sixteen,” referring to its Civil Aeronautics Board registration number, NC14716. The airplane and Humphrey Bogart starred in a 1936 First National Pictures movie, “China Clipper.”
NC14716 was the first of three Martin M-130 four-engine flying boats built for Pan American Airways and was used to inaugurate the first commercial transpacific air service from San Francisco to Manila in November, 1935. Built at a cost of $417,000 by the Glenn L. Martin Company in Baltimore, Maryland, it was delivered to Pan Am on October 9, 1935. The airplane’s serial number was 558.
Pan American Airways’ Martin M-130m China Clipper, NC14716, over San Francisco, California. (Clyde Herwood Sunderland, Jr./Library of Congress 94509045)
The M-130 was operated by a flight crew of 6–9, depending on the length of the flight, plus cabin staff, and could carry 18 passengers on overnight flights, or a maximum 36 passengers.
Cutaway illustration of Pan American Airways’ Martin M-130 China Clipper. Detail from larger image. (National Air and Space Museum SI-89-1216-A)Martin M-130 3-view drawing. (Flight)
The Martin M-130 was 90 feet, 10.5 inches (27.699 meters) long with a wingspan of 130 feet, 0 inches (39.624 meters). It was 24 feet, 7 inches (7.493 meters) high. The total wing area was 2,315 square feet (215 square meters), including the “sea wings”. Its maximum takeoff weight was 52,252 pounds (23,701 kilograms).
The flying boat was powered by four air-cooled, supercharged Pratt & Whitney Twin Wasp S2A5-G two-row 14-cylinder radial engines with a compression ratio of 6.7:1. They had a normal power rating 830 horsepower at 2,400 r.p.m., and 950 horsepower at 2,550 r.p.m. for takeoff. They drove three-bladed Hamilton Standard Hydromatic constant-speed propellers through a 3:2 gear reduction. The S2A5-G was 3 feet, 11.88 inches (1.216 meters) in diameter, 4 feet, 8.75 inches (1.441 meters) long, and weighed 1,235 pounds (560 kilograms).
Martin M-130 NC14716, right rear quarter view.
The airplane had a cruise speed of 130 miles per hour (209 kilometers per hour) and a maximum speed of 180 miles per hour (290 kilometers per hour). The M-130’s service ceiling was 10,000 feet (3,048 meters). Its range was 3,200 miles (5,150 kilometers).
Martin M-130, NC14716, China Clipper, moored at some distant exotic locale. (Unattributed)
Rank and organization: Captain, U.S. Army Air Corps.
Place and date: L’Isle Adam railroad bridge over the Seine in occupied France, 9 August 1944.
Entered service at: Storm Lake, lowa. Birth: Jefferson, lowa.
G.O. No: 43, 30 May 1945.
Medal of Honor
Citation: On 9 August 1944, Capt. Lindsey led a formation of 30 B-26 medium bombers in a hazardous mission to destroy the strategic enemy held L’lsle Adam railroad bridge over the Seine in occupied France. With most of the bridges over the Seine destroyed, the heavily fortified L’Isle Adam bridge was of inestimable value to the enemy in moving troops, supplies, and equipment to Paris. Capt. Lindsey was fully aware of the fierce resistance that would be encountered. Shortly after reaching enemy territory the formation was buffeted with heavy and accurate antiaircraft fire. By skillful evasive action, Capt. Lindsey was able to elude much of the enemy flak, but just before entering the bombing run his B-26 was peppered with holes. During the bombing run the enemy fire was even more intense, and Capt. Lindsey’s right engine received a direct hit and burst into flames. Despite the fact that his ship was hurled out of formation by the violence of the concussion, Capt. Lindsey brilliantly maneuvered back into the lead position without disrupting the flight. Fully aware that the gasoline tanks might explode at any moment, Capt. Lindsey gallantly elected to continue the perilous bombing run. With fire streaming from his right engine and his right wing half enveloped in flames, he led his formation over the target upon which the bombs were dropped with telling effect. Immediately after the objective was attacked, Capt. Lindsey gave the order for the crew to parachute from the doomed aircraft. With magnificent coolness and superb pilotage, and without regard for his own life, he held the swiftly descending airplane in a steady glide until the members of the crew could jump to safety. With the right wing completely enveloped in flames and an explosion of the gasoline tank imminent, Capt. Lindsey still remained unperturbed. The last man to leave the stricken plane was the bombardier, who offered to lower the wheels so that Capt. Lindsey might escape from the nose. Realizing that this might throw the aircraft into an uncontrollable spin and jeopardize the bombardier’s chances to escape, Capt. Lindsey refused the offer. Immediately after the bombardier had bailed out, and before Capt. Lindsey was able to follow, the right gasoline tank exploded. The aircraft sheathed in fire, went into a steep dive and was seen to explode as it crashed. All who are living today from this plane owe their lives to the fact that Capt. Lindsey remained cool and showed supreme courage in this emergency.
Strike photo, L’Isle-Adam Railroad Bridge, 9 August 1944. (U.S. Air Force)
Darrell Robbins Lindsey was born 30 December 1919 at Jefferson, Iowa. He was the second of two sons of Jesse Lyle Lindsey, a civil engineer, and Grace Alice Puffer Lindsey. Darrell Lindsey grew up in Iowa, where he attended Fort Dodge High School, graduating in 1938. He then studied at Buena Vista College at Storm Lake, before transferring to Drake University in Des Moines.
Aviation Cadet Darrell Robbins Lindsey, circa 1942.
Immediately following the United States’ entry into World War II, 16 January 1942, Lindsey enlisted as an aviation cadet in the U.S. Army Air Corps. He trained as a pilot and on graduating from flight school, was commissioned as a second lieutenant, 27 August 1942.
Lieutenant and Mrs. Darrell R. Lindsey, circa 1942.
Following his commissioning, Lieutenant Lindsey married Miss Evelyn Scott of Storm Lake, Iowa.
Lieutenant Lindsey next trained as a bombardier at Kirtland Field, New Mexico. He was promoted to first lieutenant and was assigned to a Martin B-26 Marauder operational training unit, the 314th Bombardment Squadron (Medium), at MacDill Army Airfield, near Tampa, Florida. He was promoted to captain in December 1943.
Captain Lindsey was assigned to the 585th Bombardment Squadron (Medium), 394th Bombardment Group (Medium), as a B-26 aircraft commander and flight leader. The unit deployed to Europe in February 1944. The 585th was initially stationed at RAF Boreham (AAF-161) in Essex, but in July 1944, moved to RAF Holmsley South (AAF-455), Hampshire, England.
The bombing mission against the L’Isle-Adam Railroad Bridge on 9 August 1944 was Captain Lindsey’s 46th combat mission. Army Air Corps records indicate that at the time of his death, he had flown a total of 1,497:00 hours. 143 hours were in combat.
Captain Lindsey’s remains were buried at an unknown location. In 1959, a cenotaph memorializing Captain Lindsey was placed at Jefferson Cemetery, Jefferson, Iowa.
The Medal of Honor was presented to Captain Lindsey’s widow, Mrs. Evelyn Scott Lindsey, 9 August 1945, by Major General Robert B. Williams, commanding Second Air Force. In November 1946, Lindsey Air Station at Wiesbaden, Germany, was named in his honor.
In addition to the Medal of Honor, Captain Lindsey was awarded the Distinguished Flying Cross, the Air Medal with eight oak leaf clusters (nine awards), and the Purple Heart.
Martin B-26B-55-MA Marauder 42-96153 of the 397th Bombardment Group (Medium), at Peronne Advanced Landing Ground (A-72), France, January 1945. This is the same type as the B-26 flown by Captain Darrell R. Lindsey, 9 August 1944. (U.S. Air Force)
Captain Lindsey’s B-26 was a Glenn L. Martin Company B-26B-55-MA Marauder, serial number 42-96101, built at Baltimore, Maryland. It carried the squadron identification markings 4T N on its fuselage.
The Martin B-26 first flew 25 November 1940. 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-26B-55-MA Marauder 42-96142, 596th Bombardment Squadron (Medium), 397th Bombardment Group (Medium). This is the same type aircraft flown by Captain Lindsey in the attack against the L’Isle-Adam Railroad Bridge. (U.S. Air Force)
The B-26B was 58 feet, 3 inches (17.755 meters) long with a wingspan of 71 feet, 0 inches (21.641 meters) and overall height of 21 feet, 6 inches (6.533 meters). It had an empty weight of 24,000 pounds (10,886 kilograms) and gross weight of 37,000 pounds (16,783 kilograms).
The B-26B-55-MA was powered by two air-cooled, supercharged, 2,804.461-cubic-inch-displacement (45.956 liter), Pratt & Whitney Double Wasp 2SB-G (R-2800-43) two-row, 18-cylinder radial engines with a compression ratio of 6.65:1. The R-2800-43 had a Normal Power rating of 1,600 horsepower at 2,400 r.p.m. to 5,700 feet (1,737 meters), 1,450 horsepower at 2,400 r.p.m. at 13,000 feet (3,962 meters). Its Takeoff Power rating was 2,000 horsepower at 2,700 r.p.m. The Military Power rating was the same as Takeoff Power up to 2,700 feet (823 meters), and 1,600 horsepower at 2,700 r.p.m. to 13,500 feet (4,115 meters). They turned 13 foot, 6 inch (4.115 meter) diameter four-bladed Curtiss Electric propellers through a 2:1 gear reduction. The R-2800-43 was 6 feet, 3.72 inches (1.923 meters) long, 4 feet, 4.50 inches (1.334 meters) in diameter, and weighed 2,300 pounds (1,043 kilograms). All R-2800-43 engines were built by the Ford Motor Company.
The B-26B had a maximum speed of 270 miles per hour (435 kilometers per hour) at Sea Level, and 282 miles per hour (454 kilometers per hour) at 15,000 feet (4,572 meters). The airplane’s service ceiling was 21,700 feet (6,614 meters). It’s maximum ferry range was 2,850 miles (4,587 kilometers).
The B-26B was armed with 11 air-cooled Browning AN-M2 .50-caliber machine guns. One was at the nose on a flexible mount, two fixed guns were on each side of the fuselage in “blister packs,” there were two flexible guns in the waist. A power-operated dorsal gun turret had two, as did the tail turret.
A maximum of four 2,000 pound (907 kilograms) bombs could be carried in the bomb bay.
Martin B-26F-1-MA of the 397th Bomb Group in flight at bomb release. (U.S. Air Force)
When the B-26 entered service, it quickly gained a reputation as a dangerous airplane and was called “the widowmaker.” 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 on wingspan and the size of the vertical fin and rudder, and an emphasis was made on airspeed control during training. The Marauder had the lowest rate of combat losses of any American bomber.
The Glenn L. Martin Co. produced 5,288 Marauders between 1941–1945. It served in the Pacific, Mediterranean and European combat areas. 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 light twin-engine bomber.
Martin-Omaha B-29-45-MO Superfortress 44-86292, Enola Gay, being moved into position over the pit to load Little Boy, 5 August 1945. (U.S. Air Force)
5 August 1945: In the afternoon, the Glenn L. Martin Company B-29-45-MO Superfortress 44-86292 was towed into position over a 13-foot × 16-foot (3.9 × 4.9 meters) concrete pit on the island of Tinian in the Marshall Group. Down in that pit was the most destructive weapon of war yet devised by man: The Mark I, code named Little Boy.
Little Boy was a nuclear bomb, designed to explode with unimaginable force when two masses of highly enriched uranium were forced together at very high speed. This was a “gun-type” bomb, considered to be so simple that it was not even tested before it was used.
Several hours later, at 0245 6 August 1945, the B-29, which had been named Enola Gay, took off from North Field and headed toward Hiroshima, Japan.
Bomb Unit L-11 in the pit before loading aboard Enola Gay, 5 August 1945. (U.S. Air Force)
27 November 1933: The United States Army Air Corps accepted the Glenn L. Martin Company’s first service test YB-10 bomber, serial number 33-140. This was the first all-metal monoplane bomber with an internal bomb bay, retractable landing gear, rotating gun turret and enclosed cockpit. It flew faster than pursuit aircraft of the day.
These airplanes were powered by two air-cooled, supercharged, 1,823.129-cubic-inch-displacement (29.876 liter) Wright Cyclone SGR-1820-F2 (R-1820-25) 9-cylinder radial engines with a compression ratio of 6.4:1, which were rated at 750 horsepower at 1,950 r.p.m. at Sea Level. The engines turned three-bladed Hamilton Standard adjustable-pitch propellers through a 16:11 gear reduction. The R-1820-25 was 3 feet, 11–13/16 inches (1.214 meters) long, 4 feet, 5-¾ inches (1.365 meters) in diameter, and weighed 1,047 pounds (475 kilograms).
