Rotorcraft 4 : Any heavier-than-air aircraft which derives its lift in flight from the reaction of the air on one or more rotors on substantially vertical axes
Ministry of Business, Innovation and Employment, Glossary of terms and acronyms, Wellington, New Zealand 2010. http://wwwsosh.govt.nz/resources/glossary-u.shtml, (Occupn Hlth and Sfty - Brit) {530}