- February 2nd, 2011, 11:41 am
#44756
I was reading this about TTD on rollbacks
The speed of Top Thrill Dragster is controlled by a computer which regulates the speed of the launch in order to minimize forces as the train crests the hill. Occasionally, a train is not launched with enough speed to clear the crest. This typically happens in cool, wet or breezy weather, or when the wind is working against the train. In these conditions, the launch often does not provide the train with enough speed to climb over the hill, which causes the train to stop short of the apex, and roll back down the hill in reverse, hence the term "rollback". The launch track is equipped with retractable magnetic braking fins which are raised after the train is launched in order to slow a train that did not crest the hill.
Intamin's term for this occurrence is "short shot" rather than "rollback", but the term "rollback" is used almost exclusively in the parks that operate Accelerator Coasters, as well as in the coaster enthusiast community.
On very rare occasions a combination of the weight distribution of the train, the force of the launch, and the wind can stall a train on the top of the tower. This has happened on June 24, 2005,[2], October 25, 2008 and May 25, 2009.