Martin JRM-3 Mars Bu. No. 76822, Marshall Mars, burning off Diamond Head, Oahu, Hawaiian Islands, 5 April 1950. (U.S. Navy)
While on a test flight following an engine change, a United States Navy Martin JRM-3 Mars seaplane, Marshall Mars, Bu. No. 76822, suffered an engine fire (inboard, left wing) and made an emergency landing at Ke’ehi Lagoon, off Diamond Head, Hawaii, 5 April 1950. The airplane’s crew was rescued but the airplane exploded and sank.
The wreck was discovered on the sea floor in August 2004 at a depth of approximately 1,400 feet (427 meters).
The Martin JRM Mars was a large four-engine flying boat transport built by the Glenn L. Martin Company for the U. S. Navy. originally designed as a patrol bomber, the prototype XPB2M-1 Mars made its first flight on 3 July 1942, Only five transport variants were built, four designated JRM-1, with the last one being a JRM-2. Each airplane was given an individual name derived from the names of island chains in the Pacific Ocean: Marianas Mars, Hawaii Mars, Philippine Mars, Marshall Mars and Caroline Mars. These airplanes were used to transport personnel and cargo between the West Coast of the United States and the Hawaiian Islands. All were upgraded to JRM-3.
Four Martin JRM-3 Mars flying boats in formation. (U.S. Navy)
The Martin JRM-2 Mars had a normal crew of 4, with accommodations for a relief crew. It was designed to carry 138 combat troops or 34,000 pounds (15,422 kilograms) of cargo. It was 120 feet, 3 inches (36.652 meters) long with a wingspan of 200 feet, 0 inches (60.960 meters) and height of 43 feet, 8 inches (13.310 meters), with beaching gear. The wing area was 3,686 square feet (342.4 square meters). The flying boat had an empty weight of 80,701 pounds (36,605 kilograms) and a maximum takeoff weight (MTOW) 0f 165,000 pounds (74,843 kilograms).
Martin JRM-2 Mars three-view illustration with dimensions. (U.S. Navy)
A NASA publication states, “A zero-lift drag coefficient of 0.0233 and a maximum lift-drag ratio of 16.4 made the JRM the most aerodynamically efficient of any of the flying boats. . . .”
Martin JRM-3 Mars, Bu.No. 76822, Marshall Mars. (U.S. Navy)
The Martin Mars was powered by four air-cooled, supercharged, direct-fuel-injected, 3,347.662-cubic-inch-displacement (54.858 liter) Wright Aeronautical Division R-3350-24WA (Cyclone 18 825C18BD1) (also known as the Duplex-Cyclone), a two-row 18-cylinder radial engines with a compression ratio of 6.70:1 and water/alcohol injection. This engine has a normal power rating of 2,000 horsepower at 2,400 r.p.m at 5,500 feet (1,676 meters) and 1,800 horsepower at 2,400 r.p.m. at 15,000 feet (4,572 meters). The engine’s takeoff power rating is 2,500 horsepower at 2,900 r.p.m. 100/130 octane aviation gasoline was required. The engines drove four-bladed 16 foot, 8 inch (5.080 meter) Curtiss Electric variable-pitch propellers through a 0.4375:1 gear reduction. (After modification to the JRM-3, the propellers on the inboard engines were reversible.) The R-3350-24WA is 6 feet, 8.58 inches (2.047 meters) long, and 4 feet, 6.13 inches (1.375 meters) in diameter. Its dry weight is 2,822 pounds (1,280 kilograms).
The JRM-3 had a cruise speed of 165 knots (190 miles per hour/306 kilometers per hour) and a maximum speed of 211 knots (243 miles per hour/391 kilometers per hour) at 15,600 feet (4,755 meters). The service ceiling was 19,700 feet (6,005 meters) and its range was 3,790 nautical miles (4,361 statute miles/7,019 kilometers).
A U.S. Navy Martin JRM Mars. (Glenn L. Martin Co.)
Martin XB-51 46-685, the number one prototype, on takeoff. (Lockheed Martin)
25 March 1956: At approximately 10:50 a.m., the first of two prototype Martin XB-51 three-engine attack bombers, serial number 46-685, crashed on takeoff from Runway 22 at El Paso International Airport (ELP). The pilot, Major James Otto Rudolph, United States Air Force, survived the crash although he was seriously burned. Staff Sergeant Wilbur Robert Savage, 28, engineer, was killed. Major Rudolph died of injuries 16 April 1956.
Pieces of wreckage were marked “Gilbert XF-120” which had been painted on the airplane for the filming of the William Holden, Lloyd Nolan movie, “Toward The Unknown.” (Toluca Productions, 1956). The second prototype, 46-686, had previously crashed at Edwards AFB.
A newspaper article from the El Paso Times is quoted below [I have corrected some typographical errors]:
03/26/1956
Bill Feather El Paso Times
A sleek jet bomber, carrying a full load of fuel, crashed while attempting a take-off at International Airport Sunday morning, killing the flight engineer and seriously injuring the pilot.
The XB-51, the only one of its type in existence, smashed through the fence at the end of the southwest runway and then began to disintegrate, spreading wreckage along a 250-yard trail.
Only the tail section of the three-engine bomber was left intact.
Name of the dead man, a 28-year-old staff sergeant was withheld pending notification of next of kin.
Flying the aircraft was Maj. James O. Rudolph, 36, one of the top test pilots in the Air Force.
He suffered severe burns and was taken Sunday afternoon in an emergency flight to Brooke Army Hospital in San Antonio.
The XB-51, based at Edwards Air Force Base in Muroc, Calif., was being flown to Eglin Air Force Base, Florida, where it was to be used in the filming of a Warner Brothers movie, “Toward the Unknown.”
Identification of the aircraft was confused for a short time after the crash.
A piece of wreckage with the notation “Gilbert XF-120” was found nearby.
HAD REFUELED
Air Force spokesmen explained that the XF designation had been painted on the plane for use in the movie.
The airplane had been refueled at International Airport and started its takeoff at 10:30 a.m.
Witnesses said the plane got about three feet above the ground and suddenly settled. The tail dragged first and then the rest of the airplane settled, running at high speed.
It ripped through a barbed wire fence at the end of the runway, raced across Airport Road and then began to go to pieces.
After crashing, it burned and several explosions threatened firemen, rescuers and spectators who crowded around the flaming aircraft.
First person to the scene of the crash was Eddie C. Wilkerson, 1106 Del Monte Drive, tennis coach at Austin High School.
“I was just turning into the road to the airport when the plane was taking off. I don’t believe it ever got airborne.
“I looked back and saw a big ball of smoke, so I just wheeled my car around.”
Wilkerson said that when he arrived, the major was lying on the ground about 15 feet from the burning wreckage.
“His clothes were burning so I started tearing them off.”
Other witnesses to the crash arrived and helped Wilkerson move the major to a safer place, away from the intense heat of the flaming aircraft.
Capt. John D. Chandler, a doctor at the Biggs Hospital, was at the airport when the crash occurred and he was one of the first persons at the scene. He administered aid to the injured man until an ambulance arrived. Later Capt. Chandler flew to San Antonio with Maj. Rudolph.
A fire truck from International Airport was rushed to the scene almost as soon as the plane stopped its forward motion.
Sunday drivers were attracted to the scene by the tower of smoke and the heavy traffic delayed the arrival of fire trucks from Biggs Air Force Base.
The plane was one of two XB-51s built by Martin Aircraft Co. and was completed in 1953.
The first one crashed at Muroc, Calif., in 1952.
Air Force spokesmen said the aircraft was comparable to the B-47, which was accepted instead of the XB-51 for use in the Air Force.
Its three jet engines one in each wing and on in the fuselage, were capable of driving the craft at tremendous speeds. The aircraft had broken the sound barrier, spokesmen said.
Its sleek lines gave it the appearance of a fighter rather than a medium bomber.
Normally, the airplane carried a crew of three.
Recently it had been used in assisting the Army in missile and anti-aircraft development at Aberdeen Proving Ground, Md.
A board of officers was investigation the crash and two Air Force colonels arrived at Biggs Air Force Base from Muroc Sunday afternoon.
Military police from Ft. Bliss and Air Police patrolled the area about the crash Sunday afternoon, keeping away the curious.
James Otto Rudolph was born at Marion, Ohio, 8 February 1920, the first of two children of of Frank Otto Rudolph, a German immigrant who was employed as a secretary for the YMCA, and Helen Claire Shafer Rudolph.
Following two years of college, Rudolph enlisted as an Aviation Cadet, U.S. Army Air Corps, at Detroit, Michigan, 17 March 1941. He was 6 feet, 1inch (1.854 meters) tall and weighed 175 pounds (79.4 kilograms). He was commissioned as a Second Lieutenant, Air Reserve, 31 October 1941,and was promoted to First Lieutenant, Army of the United States (Air Corps), 5 August 1942. He was again promoted, to Captain, 15 June 1943. Following the end of World War II, Rudolph was promoted to the rank of Major, 19 September 1946. He remained in the Air Force, but with military needs shrinking, he reverted to the rank of First Lieutenant, with date of rank, 7 December 1944.
James Rudolph married Clara D. in 194–
Major Rudolph graduated from the U.S. Air Force Experimental Flight Test Pilot School, Class 54-A, 2 July 1954. As a test pilot at Edwards Air Force Base, Rudolph was a project pilot in the FICON program in which Republic RF-84K Thunderflash reconnaissance planes were carried by modified Convair RB-36D bombers.
During his military career, Major Rudolph had been awarded the Air Medal with three oak leaf clusters (four awards).
After the crash on 25 March 1956, Major Rudolph was taken to Brooke Army Hospital, Fort Sam Houston, Texas, suffering from 2nd and 3rd degree burns over 38% of his body. He contracted septicemia and died there, 16 April 1956. He is buried at Arlington National Cemetery.
Wilbur Robert Savage was born 19 July 1927 at Dawsonville, Georgia. He was the son of Newton McKinley Savage and May Belle Carney Savage. He married to Ida Pedroza Aceves in 1948. They would have three children.
Staff Sergeant Savage’s remains were interred at Mountain View Cemetery, San Bernardino, California.
The first Martin XB-51, 46-585, in flight. (U.S. Air Force)
The Glenn L. Martin Co. XB-51 was a prototype jet-powered ground attack bomber. It was an unusual design for its time. The airplane had mid-mounted, variable-incidence swept wing, a T-tail and tandem landing gear with a configuration similar to that used on the Boeing B-47 Stratojet (and which had been tested using a Martin B-26 Marauder medium bomber.)
The XB-51 was operated by a pilot in a single-place cockpit with a bubble canopy, and a navigator station inside the fuselage, below and behind the pilot. The prototype was 85 feet, 1 inch (25.933 meters) long with a wingspan of 53 feet, 1 inch (16.180 meters) and overall height of 17 feet, 4 inches (5.283 meters). The total wing area was 548.0 square feet (50.9 square meters). The airplane had an empty weight of 30,906 pounds (14,019 kilograms) and a maximum overload takeoff weight of 62,452 pounds (28,328 kilograms).
The wings of the XB-51 were swept aft to 35° and had 6° anhedral. The wings’ angle of incidence (the relation of the chord to the fuselage longitudinal axis) could be adjusted to increase lift for takeoff and landing. They had 2° negative twist and were equipped with leading edge slats for improved low speed performance. Instead of ailerons, the XB-51 used spoilers.
Lloyd Nolan (“General Bill Banner”) and William Holden (“Major Lincoln Bond”) with the “Gilbert XF-120” in the 1956 Hollywood movie, “Toward the Unknown.” (Toluca Productions via Turner Classic Movies)
Power was supplied by three General Electric J47-GE-13 turbojet engines, with two located in nacelles outboard of the forward fuselage on 45° pylons, and a third installed in the tail with its intake on top of the fuselage. The J47-GE-13 was an axial-flow turbojet with a 12-stage compressor and single stage turbine. It had a normal power rating of 4,320 pounds of thrust (19.216 kilonewtons) at 7,370 r.p.m.; military power, 5,200 pounds (23.131 kilonewtons) at 7,950 r.p.m. (30-minute limit); and maximum power rating of 6,000 pounds(26.689 kilonewtons) at 7,950 r.p.m., with water/alcohol injection (5-minute limit). The engine was 12 feet, 0.0 inches (3.658 meters) long, 3 feet, 3.0 inches (0.991 meters) in diameter and weighed 2,525 pounds (1,145 kilograms). A Rocket Assisted Takeoff (RATO) system was also installed.
The XB-51 had a maximum speed of 560 knots (644 miles per hour/1,037 kilometers per hour) at Sea Level—0.85 Mach. The service ceiling was 39,400 feet (12,009 meters) and the maximum ferry range was 1,255 nautical miles (1,444 statute miles/2,324 kilometers).
Armament was planned for a maximum bomb load of 10,400 pounds (4,717 kilograms) carried internally in a rotary bomb bay, and eight M39 20 mm revolving autocannon mounted in the nose with 160 rounds of ammunition per gun. 5-inch High Velocity Aerial Rockets (HVAR) could be carried under the wings or in the bomb bay.
Martin XB-51 46-685 during engine start and ground run-up. (U.S. Air Force)
Lieutenant Byron Quinby Jones, Aviation Section, Signal Corps, United States Army. (San Diego Air and Space Museum Archive)
15 January 1915: At San Diego, California, Lieutenant Byron Quinby Jones, Aviation Section, Signal Corps, United States Army, set a flight endurance record of 8 hours, 53 minutes, flying a Glenn L. Martin Company Martin T Army Tractor. The flight consumed 30 gallons (114 liters) of gasoline. Lieutenant Jones estimated that he had sufficient fuel remaining for another two hours in the air, but approaching darkness forced him to land.
For this and other flights at San Diego, Lieutenant Jones was awarded the Mackay Trophy.
Martin T Army Tractor. (U.S. Air Force)Clarence H. Mackay
The Mackay Army Aviation Cup was established in 1911 by Clarence Hungerford Mackay, Chairman of the Board of Directors of the Postal Telegraph and Cable Corporation. Now known as the Mackay Trophy, it is awarded yearly for “the most meritorious flight of the year” by U.S. Air Force personnel.
Lieutenant Jones was the sixth aviator to be awarded the trophy. The trophy is kept at the Smithsonian Institution National Air and Space Museum. It was appraised in the 1960s at a value of $65,000, though it was also estimated that it would cost $650,000 to duplicate it.
The Mackay Trophy. (NASM)Lieutenant Byron Quinby Jones, 14th Cavalry Regiment, United States Army
Byron Quinby Jones was born at Henrietta, New York, 9 April 1888. He was one of four children of Samuel Titus Jones and Sarah Minerva Quinby Jones. He attended School 24 and East High School, Rochester, New York.
Jones entered the United States Military Academy, West Point, New York, 15 June 1907, and graduated 12 June 1912 with a bachelor of science degree. He was commissioned as a second lieutenant in the 14th Cavalry Regiment, United States Army.
Lieutenant Jones volunteered for pilot training and was sent to the Signal Corps Aviation School at North Field, San Diego, California. After earning a rating as one of the earliest U.S. military pilots and serving for a year with an active squadron, Jones was promoted to the rank of first lieutenant, Aviation Section, Signal Corps, 23 November 1914. He was then sent to the Massachusetts Institute of Technology (MIT) for the very first post-graduate course in aeronautical engineering.
In addition to he endurance records, “B.Q.” Jones was also the first Army pilot to perform a loop, an intentional stall and recovery, and a “tail spin.”
During World War I, Jones rose to the temporary rank of lieutenant colonel.
Jones married Mrs. Evelyn Clark Chadwick (née Evelyn Kennerly Clark, grand daughter of William Clark, co-leader with Meriwether Lewis of the 1804–1806 Lewis and Clark Expedition), 4 June 1917.
For the next twenty-four years, Jones steadily rose in rank and was an important figure in Army aviation. Assigned to the newly established Air Service, Jones was promoted to the rank of major, 1 July 1920, and lieutenant colonel, 1 August 1935.
In 1939, because of a disagreement with senior Air Corps officers over military aviation doctrine, Lieutenant Colonel Jones requested a return to the Cavalry. He was promoted to the rank of colonel, Army of the United States, 16 November 1940, and colonel, United States Army, 1 February 1942.
Byron Jones graduated from the Army Industrial College in 1926, Command and General Staff School, 1927, and the Army War College, 1929.
Colonel Byron Q. Jones, United States Army
Colonel Jones was a leader in forming a mechanized cavalry and combined arms service. During World War II, he served in the Guadalcanal Campaign, and the staff of General Douglas MacArthur in Australia. He then held several assignments within the continental United States. He was hospitalized for lengthy periods several times, and finally was discharged from the Army, 31 January 1944.
Colonel Byron Quinby Jones, United States Army (Retired), died at Walter Reed Army Hospital, 30 March 1959, at the age of 70 years. His remains were interred at the Arlington National Cemetery.
Martin T Army Tractor in flight at San Diego. (San Diego Air and Space Museum Archive)
The Martin T was a two-place, single-engine biplane ordered as a trainer for the Signal Corps. Three were built and given serial numbers S.C.31–33. The airplane was a tractor configuration, with an engine and propeller at the front of the fuselage, rather than behind in a pusher configuration. The Martin T also had a wheeled tricycle undercarriage. Both of these features were relatively new and would become standard.
“This photograph of the Clipper, aloft at the mouth of the Middle River, was taken from another plane by Robert F. Kniesche, Sun staff photographer.” (The Sun (Baltimore), Vol. 196–D, Friday 21 December 1934, Page 30, Columns 3–5 )
20 December 1934: William K. (“Ken”) Ebel lifted off from Middle River, Maryland, taking the Martin M-130 “Clipper” for its first flight. The M-130 was airborne for approximately 1 hours. Flying at 1,200 feet (366 meters), it reached 160 miles per hour (257 kilometers per hour).
Three-view illustration of the Martin M-130. (Flight, The Aircraft Engineer & Airships, Vol. XXVII, No. 1361, 24 January 1935, Page 99)
NC14716, named China Clipper, was the first of three Martin M-130 four-engine flying boats built for Pan American Airways. It 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 was operated by a flight crew of 6 to 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. NASM SI-89-1216-A. Full image at: https://airandspace.si.edu/multimedia-gallery/7135hjpg)
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).
Martin M-130 under construction, 24 May 1934. (SFO Museum)
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).
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).
A Martin M-130, X14714, undergoing ground testing at the Glenn L. Martin Co. plant at Middle River, Maryland, 30 November 1934. (Lockheed Martin)Martin M-130 X14714, 30 November 1934. (SFO Museum)
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.)
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 boar
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.
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.
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 the 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.
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.
