Boom Length : The straight line distance form the centerline of boom foot pin to centerline of boom point load hoist sheave pin, measured along the longitudinal axis of the boom. (Spec 2C)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}