The Official Helicopter Blue Book® has been continuously published since 1979. During this time, HV$ has developed relationships with original equipment manufacturers (OEMs), overhaul facilities, brokers, finance and lease firms, and many operators that aid in our data collection. These relationships, in combination with the 2,500 appraisal HV$ performs annually allows HV$ to provide accurate current and historical resale data for more than 200 civilian helicopter models. Online access to The Official Helicopter Blue Book® includes specifications, current resale pricing, current and historical manufacturer pricing, Perspectives: A Resale History®, average resale trends, and component overhaul and retirement cycles for over 200 civilian helicopter models.