Collaboration Addresses AFSOC Need for Functional Spotting Charge

As part of an effort to produce a functional spotting charge for Air Force Special Operations Command training purposes, AFRL turned to leftover World War II inventories, modifying the armor piercing rounds—here being fired from an AC-130 gunship—remaining from that era.

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Collaboration Addresses AFSOC Need for Functional Spotting Charge

Published Nov. 13, 2009
By Shelly Rich
Munitions

EGLIN AIR FORCE BASE, Florida -- Air Force Special Operations Command turned to Air Force Research Laboratory for assistance in finding a more affordable and efficient training round with an observable impact assessment capability. Faced with a dwindling ammunition inventory but reluctant to consume expensive high explosive incendiary wartime ammunition for training purposes--specifically, for 40 mm Bofors cannon training aboard AC-130 gunships--AFSOC resorted to using armor piercing rounds left over from World War II production inventories in order to meet stringent training requirements. Unfortunately, this particular armor piercing round leaves little or no impact signature when fired, rendering spot-on target impact assessment and aim corrections virtually impossible.

AFRL researchers quickly addressed this warfighter need, teaming with AFSOC Headquarters, the 780th Test Squadron, and the US Air Force Non-Nuclear Munitions Safety Board to develop and test a functional spotting charge by modifying the existing WWII armor piercing round. This modification provides AFSOC an immediate accuracy-assessment capability at a reduced cost, while saving the use of precious wartime assets. With an estimated 350,000 armor piercing rounds in inventory and available for modification, a potential net savings of $100 million is feasible.

The first of many tests performed purposefully evaluated the mechanical functionality of the modified round without the incendiary mix. In 2 short weeks, the researchers had produced the necessary drawings, performed the appropriate tests, and generated a solution. Their solution involved a functional "flyer plate," a design that subsequently confirmed impact-driven excitation of the incendiary mix. Once excited, the mix instantaneously produces a 2 ft fireball easily seen with sensors or the naked eye. This type of impact signature enables immediate battle damage assessment and quick-turnaround error correction. Following ground validation, the modified armor piercing round took to the skies for its final test, with researchers aboard an AC-130 gunship employing the spotting charge in an operational environment. Using a combination of unaided vision, night vision goggles, and aircraft sensors, aircrew and ground observers witnessed outstanding charge functionality during flight testing, with 29 out of 30 modified armor piercing rounds functioning at impact. The newly modified round accordingly received immediate NNMSB approval.