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Various catapult systems have been utilized throughout the years to harness and control the power necessary to launch aircraft, and Naval Air Station Patuxent River has been home to all the major catapult systems including steam, hydraulic and even experimental electric.

A Mysterious Catapult

Early 1942 concept drawings for Pax River show a catapult barge was anchored in the Patuxent River and, while this barge-mounted catapult may have never been used, there is evidence on an early facility map that a Sea Plane catapult was constructed at the east entrance to the East Seaplane Basin, near the U.S. Naval Test Pilot School. While nothing is known of this catapult, it may have used gunpowder to launch the seaplanes.

In addition to the installation’s current TC-7 steam catapult facility, there are also three abandoned catapult facilities here, all located in underground buildings below the airfield. The four surviving catapults here have been determined eligible for the National Register of Historic Places.

The Abandoned


Built between 1944 and 1953 and totaling some 35,000 sq. ft., a visit to these dark, dank concrete caverns is not soon forgotten.

One enters through huge trap doors in the airfield concrete and proceeds down narrow stairs into blackness. Flashlight beams are able to illuminate only small portions of the massive equipment — once alive with movement and sound — now rusting in eerie silence. The shafts of light, reflecting off pools of standing water, reveal debris-strewn corridors and doorways flanking the huge machine room spaces.

The Mark IVB — the first landplane catapult (building 108) — was completed in 1944 along Echo taxiway in the middle of the airfield. It was a hydraulic-pneumatic system which used hydraulic pumps and compressed air-powered piston equipment to transmit the acceleration force to the aircraft by means of a system of cables and pulleys. This system could launch an 18,000 pound aircraft at 90 mph in 97 feet and be recharged in 33 seconds.

Painted on the wall is a list of 15 different 1940s and 1950s era aircraft launched from this catapult along with the length of the cable bridles required for each type. Some of the cable bridles are still hanging on the wall.

The facility was abandoned in the 1950s, but major parts of the huge catapult engine remain in the 36-by-72 foot engine room. Lower levels of the facility are inaccessible, having been flooded for many years.

In the early 1950s, construction began on a new, more powerful hydraulic-pneumatic catapult, the Model H Mark 8. Completed around 1952, this is the largest underground catapult facility (building 159) and is located at the end of Runway 14-32, near TPS. Installed in World War II-era Essex class carriers, this catapult represented the upper limit of hydro-pneumatic design and was capable of launching a 15,000 lb. plane at 120 mph or a 62,500-lb. plane at 70 mph. The design posed an explosion danger and the loss of more than 100 men in 1954 aboard USS Bennington (CVA 20), due to a hydraulic catapult explosion, helped mark the end of hydraulic catapults.

Today’s Catapult

By the early 1950s, the British had developed successful catapults using steam and Pax River installed one of the U.S. Navy’s first in 1954 — TC-7. Steam offered a safer, more powerful alternative to hydraulic catapults and, with the assistance of Pax River test personnel, steam catapults were recommended to be deployed to the fleet in 1955. Although TC-7 is showing its age, it is still one of the most valuable resources in the Pax River aircraft test arsenal and is carefully tended by the TC-7 crew.

The Experiment

One of the most interesting catapults at Pax River was the experimental “Electropult” built by Westinghouse. Constructed in 1946, it is located between Echo Taxiway and Runway 14-32 along what looks like a parallel taxiway but is, in fact, the long catapult runway.

Powered by an 1,100 hp Pratt & Whitney radial engine, cooled with air ducted from the surface, this converted aircraft engine powered a DC electric generator which powered a DC motor which spun up a 24 ton flywheel to 1,700 rpm. When the plane was ready to be launched, the energy stored in the spinning flywheel was engaged to an AC electric generator which powered the long linear motor that was the 1,400 foot long catapult track. The front wheel of the plane was placed on a sled, which was the primary core of the motor, and a bridle was attached to the aircraft main landing gear.

An article on page 81 in the November 1946 issue of Popular Science magazine explains how the system worked and there is a historic film clip of a B-25 Mitchell bomber launch, which can be viewed at The film and the photos in the article were probably taken at Pax River.

Launching a land-based bomber like the B-25, by catapult, is not something we think about today, but back then, James H. Doolittle’s daring 1942 B-25 raid on the Japanese home islands from the carrier USS Hornet (CV 8) was probably still fresh in everyone’s mind.

Only two of these electro-magnetic catapults were ever built — the other believed to have been at Mustin Field, formerly the Naval Aircraft Factory, in Philadelphia. Unfortunately, the underground chambers of Pax’s electric catapult are usually filled with 6 to 10 feet of standing water. The chambers were drained in 2011 and revealed this experimental catapult is still completely intact, albeit in bad condition.

The “electropult” was not successful, probably because the technology had not caught up with the concept. It was an idea ahead of its time.

Today’s newest Electro Magnetic Aircraft Launch System, commonly referred to as EMALS, located at Naval Air Station Lakehurst, N.J., is being installed in the new carrier USS Gerald R. Ford (CVN 78), and appears to be the successful execution of an old idea which was tested at Pax River nearly 70 years ago.

There are plans in the works to demolish all three abandoned catapult facilities in the not too distant future. However, before they’re demoed, select artifacts from each catapult will be removed for preservation.