From: firstname.lastname@example.org (JVRusso) Organization: America Online, Inc. (1-800-827-6364) Date: 22 Mar 95 02:34:21 References: 1
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As I work in the field of testing jet engines, I have shut down engines (both on purpose and in emergencies) from full power a number of times. It is true that due to thermal effects the rotor and static hardware due cool at different rates. Most times as soon as the high rotor stops turning it locks up and can not be turned for several hours. BUT, that is not due to blades touching shrouds, it id due to knife edge seals under the blade root rubbing against their seal lands. There are much tighter clearances in the seals, especially in commercial enignes, which have larger clearances, and rely on active clearance control to reduce the clearances in-flight. I have never seen any long term damage as a result of "hot shutdowns". The worst that happens is that you have to wait a few hours to borescope since you can't rotate the high rotor. We try to prevent that in a test stand by getting on starter motors as soon as N2 gets to sub-idle speeds during spool down. Hope that helped!