Tag Archives: Glenn L. Martin Company

3 July 1942

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Martin XPB2M-1 Mars, Bu. No. 1520. (Hans Groenhoff Photographic Collection, Smithsonian Institution National Air and Space Museum NASM-HGC-1059)

3 July 1942: Chief Test Pilot William Kenneth Ebel, Ph.D., Vice President of Engineering for the Glenn L. Martin Company, took the  Martin Model 170, s/n 877, for its first flight, lifting off from the waters of Chesapeake Bay. Dr. Ebel’s co-pilot was Ellis Dent Shannon, who would later become the chief test pilot for Convair.

Designated XPB2M-1 Mars, Bureau of Aeronautics serial number (“Bu. No.”) 1520, by the United States Navy, the flying boat was a prototype for a long-range patrol bomber. The first rivets had been driven for the airplane’s keel 22 August 1940, and the Mars was launched 8 November 1941. During a test in December 1941, the prototype had been damaged when a runaway propeller tore away from the No. 3 engine.

 

The Martin Mars prototype was launched 8 November 1941. (Charles M. Daniels Collection, San Diego Air & Space Museum Archives, Catalog #: 15_001975)

The U.S. Navy’s experiences early in World War II led it to adopt the Consolidated B-24 Liberator as its long range bomber (PB4Y-1 and PB4Y-2 Privateer). The XPB2M-1 was converted to a transport configuration, the XPB2M-1R, in 1943. The Navy ordered twenty transport versions, designated JRM-1. By the end of the war, only six had been built and the remaining order was cancelled.

Martin Model 170 Mars (XPB2M-1 Bu. No. 1520) at the Glenn L. Martin Co. ramp, near Baltimore, Maryland, 13 May 1942 (United States Navy, National Naval Aviation Museum, NMNA 1985.0481.003)

The Martin XPB2M-1 was a large, four-engine flying boat, operated by a crew of 11 persons. It was  118 feet, 9 inches (36.195 meters) long with a wing span of 200 feet, 0 inches (60.96 meters), and height of 37 feet, 4 inches (11.379 meters). The hull had a maximum width (“beam”) of 13 feet, 6 inches (4.115 meters). The total wing area was 3,683 square feet (342.2 square meters). The flying boat had an empty weight 75,573 pounds (34,279 kilograms), and gross weight of 140,000 pounds (63,503 kilograms).

The XPB2M-1 prototype was powered by four air-cooled, supercharged, 3,347.66-cubic-inch-displacement Wright R-3350-4 engines with a compression ratio of 6.85:1. Burning 100-octane aviation gasoline, these engines had a normal power rating of 1,700 horsepower at 2,300 r.p.m., and 2,000 horsepower at 2,400 r.p.m., at Sea Level for Takeoff. They drove three-bladed 16 foot, 6 inch (5.029 meters) diameter Curtiss Electric constant-speed propellers through a 16:7 gear reduction. The R3350-4 was 5 feet, 11.5 inches (1.816 meters) long, 4 feet, 7.12 inches (1.400 meters) in diameter, and weighed 2,450 pounds (1,111 kilograms).

The prototype Mars had a maximum speed of 221 miles per hour (356 kilometers per hour) at 4,500 feet (1,372 meters). It took 27.1 minutes to climb to 10,000 feet (,048 meters), and its service ceiling was 14,600 feet (4,450 meters). The flying boat’s fuel capacity was 10,410 gallons (39,406 liters), with 664 gallons (2,514 liters) of lubricating oil. This gave it a maximum range of 4,945 statute miles (7,958 kilometers)at 135 miles per hour (217 kilometers per hour). The maximum endurance was 37.1 hours at 131 miles per hour (211 kilometers per hour).

In the patrol bomber configuration, the XPB2M-1 could carry bombs or torpedoes. It was armed with machine guns for defense.

The XPB2M-1 was assigned to VR-8 at NAS Patuxent River, 27 Nov 1943, and later transferred to VR-2 at NAS Alameda. It was withdrawn from service in March 1945, and beached at Alameda. In April 1945 it was returned to Martin Co. for JRM-1 crew training. The prototype served as a maintenance trainer until 1949. It was then broken up.

The airplane once flew from PAX in the United States to Natal, Brazil, a distance of 4,375 miles (7,041 kilometers), while carrying a payload of 13,000 pounds (5,897 kilograms).

JRM: 0 -lift over drag coefficient 0.0233, max lift over drag 16.4

Martin Mars taxi test (Charles M. Daniels Collection, San Diego Air & Space Museum Archives, Catalog #: 15_001976)
Martin Model 170 in flight. (Charles M. Daniels Collection, San Diego Air & Space Museum Archives, Catalog #: 15_001977)

Not So Graceful

     It was not so graceful as it was towed from the Martin plant into the misty bay by small auxiliary craft.

     Through the mists from following craft it looked like as large gray whale.

     It was moved slowly by the power boats down Dark Head Creek from the plant and into the channel of the bay, 15 miles north of the mouth of the Patapsco River.

     At the controls was William K. Ebel, chief test pilot and vice-president in charge of engineering at the Martin Company.

Maneuvered Slowly

     He maneuvered the Mars slowly. When the towing boats cast off and while fireboats stood by, he started each engine separately.

     It was at this point last December, during a water test, that the No. 3 propeller tore away.

     No such mishap occurred yesterday. As the motors warmed, Ebel took the flying boat in half circles, first right, then left.

     Then he “gunned” her and the Mars sailed through the water down the bay to meet boats carrying naval officials, executives of the Martin Company and Washington officials.

Twenty-Man Crew

     With the twenty-man crew headed by Pilot Ebel, Co-Pilot Ellis E. Shannon, Capt. Harold Gray of Pan American Airways and Flight Engineer Benjamin Zelubowski, the ship warmed up for thirty minutes.

     Brig. Gen. James H. Doolittle sat with Glenn L. Martin in the observer’s boat.

     Out of the sky came a not-so-small navy amphibian plane. It paced the huge flying boat down the Chesapeake and hung over its right wing as the four largest propellers in the world lifted the ship from the water.

     Together, the two planes disappeared toward the southwest. Within thirty minutes the Mars was back. It “bumped” easily four times and sat down just as easily in the water.

Martin Jubilant

     Within a few minutes it was off again. This time it met the water evenly as it landed, then was immediately taken off again.

     Its manufacturer, Glenn L. Martin, was jubilant over the flying boat’s maiden performance.

—The Sun, Baltimore, Maryland, Vol. 211, No. 42, Saturday, 4 July 1942, Page 18, Columns 3 and 4, and continued on Page 4, Column 6

Martin XPB2M-1 Mars with a 1941 Piper J3C-65 Cub, NC40743. (Hans Groenhoff Photographic Collection, Smithsonian Institution National Air and Space Museum NASM-HGC-1073)

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

One 1 October 1918, Ebel was enlisted as a private in the Student Army Training Corps (SATC). He was trained at Heidelberg College, Tiffin, Ohio. With the end of the War, Private Ebel was discharged 20 Dec 1918.

Ebel continued his education at Heidelberg, graduating with a Bachelor of Arts (B.A.) degree in 1921, and in 1923, he completed a Bachelor of Science in Mechanical Engineering (B.S.M.E.) at the Case School of Applied Science, Cleveland, Ohio.

Also in 1921, Ken Ebel joined the 104th Observation Squadron, Maryland National Guard, based at Baltimore. He was assigned as an aviation cadet from 11 September 1923 to 3 June 1924. He was trained as a pilot at the National Guard Primary Flying School.

On 12 January 1925, William K. Ebel was commissioned as a second lieutenant, Air Service, Officers Reserve Corps. He was promoted to first lieutenant, Air Corps, 21 December 1926. He continued to serve with the Maryland National Guard

Also in 1926, Lieutenant Ebel began his career as an engineer and test pilot for the Glenn L. Martin Company.

Effective 15 February 1929, Ebel’s reserve officer’s commission was converted to first lieutenant, Air Corps.

On 21 October 1929, William Kenneth Ebel married Miss Florence E. Sherck at Seneca, Ohio. The would have two children.

Ebel was promoted to captain, Air Corps, 5 January 1935.

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)

On 25 November 1940, Ken Abel made the first flight of the Martin B-26 Marauder twin-engine medium bomber.

Ebel earned a doctorate degree in engineering (Ph.D.) from Case.

After the War, Ebel left Martin. In 1948, he became the director of the airplane division Curtiss Wright Corporation at Columbus, Ohio. In 1950 he was appointed vice president of engineering for Canadair Ltd., a Canadian aircraft manufacturer owned by the General Dynamics Corporation. After serving as a consultant for General Dynamics in Washington, D.C., Ken Ebel retired.

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

Walter Kenneth Ebel died at the Greater Baltimore Medical Center, Baltimnore, 12 July 1972.

© 2019, Bryan R. Swopes

19 May 1949

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Martin JRM-3 Mars, Bu.No. 76822, Marshall Mars. (U.S. Navy)
Martin JRM-3 Mars, Bu. No. 76822, Marshall Mars. (U.S. Navy)

19 May 1949: Martin JRM-3 Mars, Marshall Mars, United States Navy Bureau of Aeronautics serial number (Bu. No.) 76822 flew from the Alameda Naval Air Station on the east shore of San Francisco Bay, to San Diego Bay, a distance of approximately 450 miles (725 kilometers). On board, in addition to the flight crew of 7, were 301 passengers.

Martin JRM-3 Marshall Mars with its passengers. (NOAA)

The Associated Press wire service reported the story:

NAVY’S BIG FLYING BOAT MARSHALL MARS CARRIES 301 PERSONS

SAN FRANCISCO, May 19—(AP)—The Navy’s big flying boat Marshall Mars carried a record load of 301 passengers—plus seven crewmen—on a flight to San Diego today.

It had never carried more than 269 passengers before.

The 1:52 p.m. takeoff, from the naval air station at Alameda, across the bay, was uneventful.

Today’s passengers are personnel of Air Group 5, Alameda Naval Air Station, who are being transferred to San Diego. Mattresses on the floor were provided for men unable to find seats.

—Wilmington Morning Star, Friday, 20 May 1949, Page 1, Column 4.

Four Martin JRM-3 Mars flying boats in formation. (U.S. Navy)
Four Martin JRM-3 Mars flying boats in formation. In the foreground is Philippine Mars, Bu. No. 76820. The second airplane is Marianas Mars, Bu. No. 76821. (U.S. Navy)

The Martin JRM Mars was a large four-engine flying boat transport built by the Glenn L. Martin Company for the U. S. Navy. Only five 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.

The Martin JRM-3 Mars had a normal crew of 4, with accommodations for a relief crew. It was designed to carry 133 combat troops or 32,000 pounds (14,515 kilograms) of cargo. It was 120 feet, 3 inches (36.652 meters) long with a wingspan of 200 feet (60.960 meters) and height of 38 feet, 5 inches (11.709 meters). The flying boat had an empty weight of 80,701 pounds (36,605.4 kilograms). The maximum takeoff weight (MTOW) was 165,000 pounds (74,842.7 kilograms).

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 of the flying boats. . . .”

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 0.375:1 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 135 knots (155 miles per hour/250 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 miles per hour/7,019 kilometers) at 135 knots.

On 5 April 1950, Marshall Mars had an engine fire and made an emergency landing off Diamond Head, Hawaii. The crew was rescued but the airplane exploded and sank. The wreck was discovered on the sea floor in August 2004.

The remaining airplanes were later converted to fire fighting airplanes in Canada. Only two remain.

Martin JRM-3 Mars Bu. No. 76822, Marshall Mires, burning off Diamond Head, Oahu, Hawaiian Islands, 5 April 1950. (U.S. Navy)
Martin JRM-3 Mars, Bu. No. 76822, Marshall Mars, burning off Diamond Head, Oahu, Territory of the Hawaiian Islands, 5 April 1950. (U.S. Navy)

© 2020, Bryan R. Swopes

3 May 1949

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Viking 1 launch (Chicago Tribune)
Viking 1 launch (AP Wirephoto/Baltimore Sun)

3 May 1949: at 9:14 a.m., Mountain Daylight Saving Time (15:14 UTC), the Viking 1 rocket was launched from the White Sands Proving Grounds in southern New Mexico. The rocket carried a 460 pound (210 kilogram) instrumentation payload.

This was the first launch of a U.S.-designed and -built rocket capable of carrying a payload to space.¹

Viking 1 surrounded by the service gantry. The rocket is angled to the north by 3°. (Drew Ex Machina)

Although the planned engine run time was 65 seconds, Viking 1’s engine shut down after 54.5 seconds. At that time, the rocket had reached a speed of 2,350 miles per hour (3,780 kilometers per hour). After the engine shut down, Viking 1 continued to climb on a ballistic trajectory to an altitude of 50 miles (81 kilometers). As it fell back to Earth, 291 seconds after launch, the rocket broke up and was scattered across many miles of the Proving Grounds.

Viking 1 was a single-stage liquid-fueled rocket. It was built by the Glenn L. Martin Company for the Naval Research Laboratory. It was constructed primarily of aluminum. The skin was rolled into a cylinder and welded. It was 47 feet, 7.5 inches (14.516 meters) long, 2 feet, 8 inches (0.813 meters) in diameter, with a fin span of 9 feet, 2.5 inches (2.807 meters). Each fin had an area of 15 square feet (1.39 square meters). The rocket had a gross weight of 10,824 pounds (4,910 kilograms).

A Reaction Motors XLR10-RM-2 rocket engine. (Reddit)

Viking 1 was powered by a Reaction Motors Inc. XLR10-RM-2 engine. It’s propellant was a mixture of ethanol and water, mixed at a ratio of 95:5. The oxidizer was liquid oxygen. The engine produced 20,800 pounds of thrust (92.523 kilonewtons) at Sea Level, and 24,800 pounds (110.316 kilonewtons) in vacuum. Fuel was fed to the engine by a turbopump driven by high-pressure hydrogen peroxide steam. Turning at 10,000 r.p.m., the turbopump provided propellant at a rate of 110 pounds (50 kilograms) per second.

Static test firing of the Viking 1 rocket engine. (Drew Ex Machina)

The engine was mounted on gymbals which were controlled by gyroscopes. By rapidly angling the engine exhaust away from the rocket’s centerline, the engine was able to stabilize the rocket. A British Pathé news film (available on YouTube) showing the launch of Viking 2 illustrates this:

¹ “Space” is defined as being above the von Kármán Line, the boundary between the Earth’s atmosphrere and outer space, at an altitude of 100 kilometers (62.14 miles)

© 2023, Bryan R. Swopes

28 April 1937

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Pan American Airways' Martin M-130, China Clipper, at Macau, 1937.
Pan American Airways’ Martin M-130, China Clipper, at Macau, 1937.

28 April 1937: The first transpacific flight by a commercial passenger airliner is completed when Pan American Airways’ Martin M-130, China Clipper, arrived at Hong Kong. The flight had departed San Francisco Bay, California, on 21 April with 7 revenue passengers and then proceeded across the Pacific Ocean by way of Hawaii, Midway Island, Wake Island, Guam, Manila, Macau, and finally Hong Kong. The Reuters news agency briefly reported the event:

AIR LINK AROUND WORLD FORGED.

China Clipper Lands At Hong Kong.

Hong Kong, April 28.

The Pan-American Airways flying boat China Clipper landed at 11:55 this morning from Manila and Macao. This links the Pan-American and Imperial Airways, completing the commercial air link round the world. —Reuter.

—The Straits Times, 28 April 1937, Page 1, Column 4.

Pan American Airways’ China Clipper, a Martin M-130, NC14716, over Oakland, California. (Clyde Herwood Sunderland/Library of Congress 94509042)

The Oakland Tribune reported:

AIR CLIPPER SPANS SEAS TO HONGKONG

U.S. MAIL TO CHINA LANDED IN SIX DAYS

Plane Crew Feted at End Of Historic Hop From U.S. Via Philippines

     HONGKONG, April 28.—(AP)—A 30-year dream of ’round-the-world air service became reality today with the arrival of the Hongkong Clipper from Manila on the first regular flight between the two cities.

     The clipper, bridging the last 700-mile gap in the America-Asia service, placed the final link in an airplane chain whereby it is possible to encircle the world in less than a month, using scheduled commercial planes.

     The craft brought 2500 pounds of American cargo, including 100,000 letters and newspapers from the United States only six days old. The papers left Alameda, Calif., last Thursday aboard China Clipper, being transferred to the Hongkong Clipper at Manila. ¹

     A large crowd welcomed the clipper at Kaitak Airport. Included were Acting Governor N. L. Smith and representatives of all of the colony’s government and commercial activities.

     The clippers’ pilot, A. E. Laporte, and crew were escorted to a dais at the hangar, where the acting governor gave a speech of welcome.

     The plane, on its return flight on Thursday, is expected to carry 2500 pounds of cargo, including 40,000 letters.

     At a reception for the fliers, the acting governor said:

      “We are celebrating the welding of the last link in world air communication. The lessening of the physical gaps is the surest way of ending misunderstandings which have occurred between nations in the past.

“Hongkong offers congratulations, welcomes this American transpacific air service and hopes it will be another bond in the chain of goodwill.”

     Laporte said the Manila-Hongkong flight was “uneventful,” despite poor weather conditions necessitating intermittent blind flying.

—Oakland Tribune, Vol. CXXVI, No. 118, Wednesday, 28 April 1937, Page 1, Column 3

The 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 first flew on 20 December 1934, and 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.

Martin M-130 China Clipper, NC14716, at Honolulu, Ohau, Hawaiian Islands. (Unattributed)
Martin M-130 China Clipper, NC14716, at Honolulu, Oahu, Hawaiian Islands. (Unattributed)

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. Its maximum takeoff weight was 52,252 pounds (23,701 kilograms).

The flying boat was powered by four air-cooled, supercharged, 1,829.389-cubic-inch displacement (29.978 liters) Pratt & Whitney Twin Wasp S2A5-G engines. These were two-row, 14-cylinder radial engines with a compression ratio of 6.7:1. The S2A5-G was rated at 830 horsepower at 2,400 r.p.m., and 950 horsepower at 2,550 r.p.m. for takeoff, burning 87-octane gasoline. They drove three-bladed Hamilton Standard Hydromatic constant-speed propellers through a 3:2 gear reduction. The engine was 3 feet, 11.88 inches (1.216 meters) in diameter and 4 feet, 8.75 inches (1.441 meters) long. It weighed 1,235 pounds (560 kilograms).

The airplane had a maximum speed of 180 miles per hour (290 kilometers per hour), and a cruise speed of 130 miles per hour (209 kilometers per hour). The service ceiling was 10,000 feet (3,048 meters) and its range was 3,200 miles (5,150 kilometers).

Martin M-130, NC14716, China Clipper, moored at some distant exotic locale.
Martin M-130, NC14716, China Clipper, moored at some distant exotic locale. (Unattributed)

¹ There may be confusion as to which airplane was flown from Manila to Hong Kong. Most newspapers identified it as China Clipper, while the Oakland Tribune called it Hongkong Clipper.

Pan American’s Hong Kong Clipper was a Sikorsky S-42, NC823M, which had entered service in December 1934. Many newspapers dated 28 April 1937 showed a photograph of NC832M arriving at Auckland, New Zealand, after a four-day, 7,000-mile survey flight from the United States.

Entering service in 1934, the airline had originally named the NC823M West Indies Clipper. This was changed to Pan American Clipper, and later, Hong Kong Clipper. The airplane crashed on takeoff and sank near Antilla, Cuba, 7 August 1944.

Pan American Airways System’s Sikorsky S-42, NC832M, over San Francisco Bay, 1935. (NASM SI-90-3001)

© 2020, Bryan R. Swopes

5 April 1950

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Martin JRM-3 Mars Bu. No. 76822, Marshall Mars, burning off Diamond Head, Oahu, Hawaiian Islands, 5 April 1950. (U.S. Navy)
Martin JRM-3 Mars Bu. No. 76822, Marshall Mars, burning off Diamond Head, Oahu, Hawaiian Islands, 5 April 1950. (U.S. Navy)

5 April 1950: 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. 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)
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)
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.)
A U.S. Navy Martin JRM Mars. (Glenn L. Martin Co.)

© 2019, Bryan R. Swopes