(Image Source: Page 18 last link below. Click to enlarge)

Additional informtion on the "AZON guided bomb" with a couple of links to radio equipment actually used, courtesy of Richard Post (KB8TAD).

*The Azimuth “Smart” Bombs of World War II*
By Joseph Frantiska, Jr.

The AZON bomb consisted of the tail fin unit being bolted to a 1,000-pound general purpose bomb. The fins and collar on an assembled bomb made it too large for transporting in the standard racks and tended to limit the number of bombs that could be carried to four.

The American AZON Bomb:

The Allies’ guided bomb efforts started in April 1942, when the USAAF Materiel Command began the development of the azimuth-only (AZON) family of guided bombs. It was invented by Major Henry J. Rand and Thomas J. O’Donnell as the answer to the difficult problem of destroying the narrow wooden bridges that supported much of the Burma Railway. However, AZON was also used in the European Theater of Operations, as well as in the Pacific Theater.

The initial variant, designated Vertical Bomb-1 (VB-1), was based on a 1,000-pound bomb that was modified with a new tail unit. A later variant, the VB-2, was fitted to a 2,000-pound bomb. The tail unit consisted of a gyroscopic stabilization unit that prevented the bomb from spinning and weaving in unwanted directions as various corrections were made. Compressed air kept the gyros spinning during the time of the fall. The VB-1 also had a 600,000 candela flare for optical tracking, an octagonal shroud with control surfaces, and a radio command receiver. When a VB-1 was dropped, the bombardier could track it through his bombsight and use a joystick-type control to send corrective commands to the bomb. The AZON guidance system allowed only in-azimuth or lateral course corrections, and errors in range could not be corrected.

Due to its AZON guidance, the VB-1 was particularly suited to long and narrow targets like bridges or railways where range errors would be irrelevant. For normal targets, however, the VB-1 was actually not as good as unguided freefall bombs because a bomber could not break away immediately after dropping the bomb, and the accuracy was not effectively increased because of the lack of range control.

Elevators similar to preset trim tabs were attached to the collar on the control surfaces of aircraft. The elevators created a stabilizing effect on the falling bombs, allowing greater ease in altering the missile’s azimuth. Four braces were connected to the fins to support the aileron and rudder controls. The four braces were also the antenna for receiving the signal from the transmitter. The AZON transmitter antenna was located at the rear of the plane. The antenna was approximately three feet in length. One day a person who was not connected to the AZON group got curious about the antenna. He asked what the antenna was used for. A ground crewman, involved with the AZON equipment and mindful of the high degree of classification surrounding the project, answered, “It is a highly classified flak repellent gadget. It keeps the plane from getting hit.”

The bombardier’s joystick control was a BC-1156 pogo stick unit connected to a BC-1158 radio set that transmitted through the external antenna. Each aircraft had three antennae mounted beneath its tail section for control purposes. One transmitted a signal on 475 cycles for left deflection, one on 3,000 cycles for right deflection, and the third at 30-40 cycles to activate the smoke-generating system. All three frequencies were changed periodically to prevent jamming by enemy radio monitoring crews.

The AZON entered production in 1943, after earlier development by USAAF’s Air Technical Service Command. Azimuth-only bombs enabled pinpoint bombing of hard-to-hit targets such as bridges and railways.


*Pictures of the actual equipment* can be found here:
(See Page 18+, and/or Search on 'AZON' or 'RAZON' for description)