The photo shows the transmit facility near Moscow, Maine. After much R&D by the Air Force at its Hanscom, Rome, and Cambridge facilities, the OTH-B system had progressed to the Developmental Testing and Evaluation stage by 1979, for which the ERS was “to address the technical feasibility objective.” It also explored any possible environmental and personnel effects. However, Air Force scientists had noted that some RF waves would reflect off the atmosphere, down beyond the horizon, and back, overcoming the LOS limitation. Like all radars, strategic warning radar systems were limited in their range for detecting incoming aircraft and ICBMs by line-of-site (LOS). Low-power radio frequency (RF) transmission of the Continental US (CONUS) Over-the-Horizon Backscatter (OTH-B) Experimental Radar System (ERS) commenced. The Air Force’s version, coming after the other services, used a turboshaft engine in place of the original rotary piston engine. Its unique twin main rotors were synchronized and enmeshed, which enabled it to dispense with a tail rotor and gave it excel-lent hovering characteristics. Variants of this helicopter were used by the Navy, Marines, and Air Force primarily for personnel search & rescue in Vietnam, as well as firefighting and base-rescue du-ties around the world. It was designed by one of the German engineers brought to the US under Project Paperclip after WWII. The first flight of the Kaman K-600-3, the prototype for the Air Force’s HH- 43B Huskie helicopter. In this edition of Heritage Hangar, you'll learn about old and new airplanes and tidbits of what happened this week many years ago. By Air Force Life Cycle Management Center History Office