Description
W. L. Maxson U.S. Navy Aircraft-Turret Structural Interrupter, Drawing 51537, 1953
Item Overview
This original W. L. Maxson structural interrupter was designed for a powered U.S. Navy aircraft gun turret. It was an electromechanical safety device that tracked the turret’s azimuth and the guns’ elevation.
The unit limited unsafe turret movement before the gun barrels could strike the fuselage or nearby aircraft structure. It is a turret-control component, not a complete turret, firearm, sight, or trigger control.
Identification and Features
- Item type: Electromechanical structural interrupter
- Manufacturer: W. L. Maxson Corporation
- Manufacturer location: Long Island City, New York
- Maxson drawing number: 51537
- Serial number: 700
- Stock number: R91-MAX-51537-1
- Contract number: NOa(S)-52-461
- Date packed: September 1953
- Azimuth input: Splined shaft
- Elevation input: Splined shaft
- Internal profile cams: D52400, D52401, D52402, and D52403
- Electrical connector: J901
- Calibration features: Timing pins
The NOa(S) contract prefix identified a Bureau of Aeronautics supply purchase. This confirms that the assembly was ordered for a U.S. naval-aviation application.
September 1953 is the packing date. It may not be the exact manufacturing date.
How the Structural Interrupter Worked
The splined AZIMUTH and ELEVATION inputs turned as the turret and guns moved. These inputs drove four shaped profile cams inside the assembly.
Each cam represented part of the aircraft’s safe turret-travel area. As the cam positions changed, followers operated electrical contacts. Signals passed through connector J901 to the turret-control system, which limited powered movement near the airframe.
The timing pins helped preserve the correct relationship between the shafts and cams during installation. This was important because the unit had to match the turret’s position and the aircraft’s clearance limits.
Structural Interrupter vs. Fire Interrupter
This component is a structural interrupter, not a fire interrupter.
A structural interrupter limits turret movement before the guns can hit part of the aircraft. A fire interrupter works through the trigger circuit and prevents the guns from firing when they point across the fuselage, tail, wing, or another protected area.
Period Navy instructions listed these as separate safety checks.
Historical Background
Powered aircraft gun turrets became highly advanced during World War II. Electric and hydraulic systems allowed heavy guns to move quickly in both elevation and azimuth. These systems also created a serious risk: the turret could move the barrels into the aircraft itself.
Mechanical stops protected some parts of the turret’s travel. More complex installations used cam-operated interrupters to follow the changing shape of the aircraft around the turret.
A 1944 U.S. Navy gunnery manual instructed crews to lower the guns and rotate the turret to confirm that the structural interrupter kept them from swinging into the fuselage. The next check tested the fire-interruption circuit with a test light, showing that the two systems served different purposes.
This Maxson assembly was packed in September 1953, during the early Cold War. Its Bureau of Aeronautics contract shows that the Navy was still buying and supporting powered aircraft-turret equipment during this period.
The markings provided do not identify the exact turret or aircraft model. Drawing 51537 or related installation records would be needed before assigning it to a specific aircraft.
Condition
This is an original military-surplus electromechanical assembly dating from the early 1950s. It may show finish wear, scratches, oxidation, hardened lubricant, aged seals, or other signs of storage.
Its electrical operation, internal contacts, cam timing, and original calibration have not been verified unless specifically stated on the product page. It is sold as a historical collectible and is not certified for operational aircraft use.
This listing is for the structural interrupter shown in the product pictures. The aircraft, turret, guns, wiring, test equipment, and other components are not included unless pictured or specifically stated.
Ideal For
- U.S. Navy aviation collections
- Powered aircraft-turret displays
- Early Cold War military collections
- W. L. Maxson equipment collections
- Electromechanical control-system studies
- Aircraft restoration reference displays
- Military museums and educational exhibits
Approx length 6", Approx width 5", Approx height 3", Approx weight 2.7 lbs.
Pictures are stock images of our inventory. Unless otherwise noted, you will not be receiving the exact item shown in the pictures. The pictures are representative of the item's general condition. The item you receive might be slightly better, or worse, condition than was shown in the pictures.
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