Academic journal article Air Power History

Ferret: Evolution of a Design Concept

Academic journal article Air Power History

Ferret: Evolution of a Design Concept

Article excerpt

The United States Army Air Forces (USAAF) came into its own in the Second World War, refining airpower doctrine and growing a global strategic air force. Out of this war emerged the blueprint for how the soon-to-be United States Air Force (USAF) would conduct itself for the ensuing 40 odd years of the Cold War. Critical to this fight was the murky world of signals intelligence (SIGINT) and its two components--electronic intelligence (ELINT) and communications intelligence (COMINT). USAAF work in this field set the stage for Strategic Air Command's Cold War reconnaissance campaign around the perimeter of the Soviet Union. Key to the success of SIGINT in the Second World War was the ability to develop, modify and produce specialized aircraft for this critical airborne mission. The aircraft that these intrepid airmen created were referred to as ferrets.

The Beginnings

By mid 1942 the tide of the Second World War was slowly turning in favor of the Allies. Nazi Germany was stalled outside of Stalingrad and turned back from Egypt at El Alamein while the U.S. Navy inflicted a stunning defeat on the Imperial Japanese Navy at Midway. In October of that year, the USAAF flew its first ELINT mission utilizing a modified Boeing B-17E bomber assigned to the 11th Bombardment Group. Spurred by the discovery of an Imperial Japanese Navy radar by U.S. forces liberating Guadalcanal, the purpose of this new mission was to identify any Japanese radars still operating in the Solomon Islands. Engineers from the Naval Research Laboratory operated a hand-built XARD radar receiver aboard the bomber for a limited number of missions, none of which picked up any Japanese signals. (1) This initial lack of success, however, did not deter the USAAF as they continued to push ahead in their quest to intercept radar signals.

To develop radio and radar receivers, initially the USAAF relied upon the Army Signal Corps. Long since tasked with the development of Army radios and radar systems, the Signal Corps had the expertise and facilities such as the Aircraft Radio Laboratory at Wright Field, Ohio to support such an endeavor. The Office of the Chief Signal Officer in Washington coordinated with the Air Staff to ensure that these airborne receivers were developed to meet the USAAF's specific requirements. (2)

Airborne SIGINT receivers provided many benefits over their terrestrial brethren. From their operating altitude, they had better reception of enemy signals and were not as affected by terrain. They could also operate closer to enemy signals, a great benefit in the Pacific where broad expanses of water often intervened between front lines. Finally, due to the fact that they were on a moving platform, geo-location of the enemy signal was faster due to the fact that multiple 'cuts' or lines of bearing could be taken in a relatively short period of time. Airborne receiver design was basically the same as their terrestrial peers, though consideration had to be made for lightness in construction as well as hardening the design to account for the jarring of aircraft operations.

One month after the unproductive effort in the Southwest Pacific, an Eleventh Air Force photo reconnaissance mission in the Aleutians revealed a probable Japanese radar installation on the island of Kiska. The race was on once again. A collaborative effort between the Air Staff in Washington and the Aircraft Radio Laboratory in Ohio resulted in a formal requirement approved by USAAF Chief of Staff General Henry "Hap" Arnold. This project, code-named "Ferret", called for the Aircraft Radio Laboratory to team with the Naval Research Laboratory in outfitting a new Consolidated B-24D Liberator bomber with a suite of military and commercial radio receivers for the ELINT mission. The modified B-24, named Ferret I (AAF Serial 4123941--see Table 1), deployed to Adak, Alaska in February 1943. After weeks of weather delays, Ferret I flew its first operational mission over the Aleutians on March 6. …

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