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
Boeing Chinook (UK variants) those used by the British armed forces, were grounded due to cracking discovered in the landing gear of a British helicopter during routine inspection. In May 2000, several Chinook helicopters airlifted British and European Union citizens out of Freetown in Sierra Leone in an evacuation due to regional instability. In September 2000 Chinooks were being used to evacuate casualties from fighting in Freetown to RFA "Sir Percivale", a support ship docked there. In July 2006, 3 Chinook helicopters of No. 27 Squadron deployed to RAF Akrotiri in Cyprus to evacuate British citizens from Lebanon; the squadron also flew the EU