Core lock
From Wikipedia, the free encyclopedia
Core lock is a condition that can occur in stalled jet engines on aircraft that are in flight. Core lock occurs due to insfficient airflow at low speed after the engine suffers a flameout, which causes differential cooling of the engine core. Due to the engine being made up of many different materials, both metal and non-metal, they cool at slightly different rates. On a standard internal combustion engine designed for land use this would not be enough of a change to be a problem. However, jet engines are precision built, and these changes in relative proportion are too great for them to cope with, causing them to seize up. Core lock conditions make it difficult for the pilot(s) to either attempt a windmill restart or an APU assisted restart of the engine.
[edit] Pinnacle Airlines Flight 3701
Core lock was one of the contributing causes to the Pinnacle Airlines Flight 3701 accident.
"...the pilots' failure to achieve and maintain the target airspeed in the double engine failure checklist, which caused the engine cores to stop rotating and resulted in the core lock engine condition. Contributing to this accident was 1) the engine core lock condition, which prevented at least one engine from being restarted, and 2) the airplane flight manuals that did not communicate to pilots the importance of maintaining a minimum airspeed to keep the engine cores rotating..."
