Aircraft & Parts For Sale FOR SALE !!! Pressure Cowl for 402  ready for immediate sale!! It's Here!!! Walter Conversion for the Air Tractor 502. & Soloy powered Bell 47 & Hiller 12 Helicopters Barrior Filter System!! See Helicopter page. Now taking orders for Walter Conversions for Air Tractor 401, 502 and S2R Thrush for fall 2009/ Spring 2010 production schedule. Also, taking orders for Pressure Cowl production schedule. We have customers looking for the following aircraft. Air Tractor AT 401 with run out radial S2R Thrush with high time run out radial.