Helicopter flight controls blades collectively ("i.e.," all at the same time) and independent of their position. Therefore, if a collective input is made, all the blades change equally, and as a result, the helicopter increases or decreases its total lift derived from the rotor. In level flight this would cause a climb or descent, while with the helicopter pitched forward an increase in total lift would produce an acceleration together with a given amount of ascent. The collective pitch control in a Boeing CH-47 Chinook is called a "thrust control", but serves the same purpose, except that it controls two rotor systems, applying
San Francisco and Oakland Helicopter Airlines San Francisco and Oakland Helicopter Airlines San Francisco and Oakland Helicopter Airlines (also known as SFO Helicopter Airlines and SFO Helicopter) was a helicopter airline service offering scheduled passenger flights between San Francisco, Oakland, and other Bay Area cities. It was founded in 1961 but disappeared from the Official Airline Guide 15 years later before finally going out of business in 1986. San Francisco and Oakland Helicopter Airlines was one of the first helicopter airlines to operate without a federal subsidy and it was also the first to operate with only turbine engine helicopters. Since helicopter landing sites were scarce