hey faq:
"The term ‘Rollback’ is used to describe a particular uncommanded thrust reduction on the Lycoming ALF-502R engine. It manifests itself as a slow reduction in the high pressure spool speed (N1) associated with an increasing Turbine Gas Temperature (TGT) and a failure of the engine to respond to the pilot thrust lever. Following considerable research and analysis complemented by flight tests conducted by the airframe and engine manufacturers, the cause of roll-back was determined to be due to the build up of ice on the engine core super charger exit guide vanes in very specific meteorological conditions. The build up of ice on the guide vanes progressively ‘chokes’ the engine core. A modification (30437A) was devised to improve the anti-icing efficiency and is in the process of fleet embodiment. In the interim, following a study of the pattern of roll-back occurrences, an operational limitation was introduced for aircraft with unmodified ALF 502R engines by the issue of a Temporary Revision to the Aircraft Flight Manual (AFM)."
make any sense!?!?!?
