Two Minute Read, WWII

JB-17G – Flying Fortress turned Testbed

When it comes to aviation history, few aircraft have as significant a legacy as the Boeing B-17 Flying Fortress, a heavy bomber developed in the 1930s for the United States Army Air Corps (USAAC). Over the years, the B-17 went through a series of modifications and iterations, each designed to increase the aircraft’s combat effectiveness, survivability, and operational capabilities. One such variant is the JB-17G – a testament to the continuous innovation in aviation technology that characterized the era.

This essay explores the history, design, functionality, and overall significance of the JB-17G aircraft.

Historical Context

The B-17, a product of the Boeing Aircraft Company, was developed in response to the USAAC’s 1934 requirement for a multi-engined bomber to replace the Martin B-10.

B-17G Sally B banking towards the camera.
The B-17 was a workhorse and produced in huge numbers. Many were still left after the war and put to use elsewhere.

The B-17’s significance lies in its contributions to the U.S. campaigns in the Pacific and European theatres of World War II, where it demonstrated remarkable resilience and lethal bombing capability.

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The JB-17G is a variant of the B-17G, the most produced version of the Flying Fortress, with modifications that transformed it into a special testing platform.

The ‘JB’ prefix stands for “temporary special test,” indicating the aircraft’s unique role in the development and evaluation of new equipment and technology.

Design and Functionality

The basic design of the JB-17G remained largely similar to the standard B-17G. It had a wingspan of 103 feet 9 inches, a length of 74 feet 9 inches, and a height of 19 feet 1 inch.

Its four Wright R-1820-97 “Cyclone” turbosupercharged radial engines gave it the ability to maintain a top speed of 287 mph and a range of 2,000 miles. It had a service ceiling of 35,600 feet.

However, the JB-17G differed from the original B-17G due to its testing adaptations.

A JB-17G with its unusal nose configuration.
Front view of Boeing JB-17G. The aircraft is the B-17G-105-VE (S/N 44-85747), the test bed aircraft for the Allison T-56 turboprop.

Depending on the specific role for which it was being used, a JB-17G could be equipped with a variety of different testing apparatus, modifications, and instrumentation.

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This made it a flexible tool for the testing of aviation-related technology, whether it be new types of radar, aircraft engines, weapons systems, or other components.

Operational History

The JB-17G aircraft played a pivotal role as an experimental platform for aviation research and development. It was used to test everything from guided missile control systems to airborne life-saving apparatus.

The aircraft helped to develop and improve radar systems, electronic countermeasures, and a variety of weapons systems.

The block of an XT40 turboprop.
JB-17s were used to test new engines such as the XT40.

The discoveries made and the data gathered during these tests contributed to improvements in both military and civilian aviation.

After the war, several JB-17Gs continued their work in various capacities.

Some were used as drone control aircraft in the early days of unmanned flight, while others served as engine test beds for turbojet and turboprop designs.

The service life of these aircraft extended well into the 1950s and even 1960s, long past the operational use of the B-17 in active service.


In conclusion, the JB-17G stands as an emblem of innovation and experimentation within aviation history.

This special test version of the famous B-17 Flying Fortress reflects the relentless pursuit of technological advancement in the face of global conflict and beyond.

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It underscores the intertwined relationship between technology and warfare, and how the exigencies of combat often act as a catalyst for innovation.

Although not as widely recognized as its combat-oriented counterparts, the JB-17G plays an undeniably crucial role in the legacy of the B-17 and the broader sphere of aviation technology development.

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