Talk:Active tip-clearance control

Introduction
This article could really benefit from a high-level introduction, and possibly a sentence along the lines of "during normal flight, the engine warms up and the turbine casing expands, creating a small (XYZ mm) gap between the casing and the tips of the spinning compressor blades. Air leaking around, past the edge of the blades without passing through them reduces engine and fuel efficiency.  One approach to reduce the gap is by cooling the turbine casing uses a stream of cold air.  This cool air can be supplied by taking it from the by-pass valve, as found on the EJ200 and FOO and BAR engines." Although this is only my guess and it would be preferable if such an improvement could be written by somebody familiar with the topic who can fill in the correct details! —Sladen (talk) 04:17, 24 October 2008 (UTC)