The ghostly cry of a Vickers Viscount overhead at about 5000 feet is a sound I haven't heard in thirty years or more, but it's one I'm not likely to forget. Living close to Leeds Bradford Airport all my life, I became accustomed to hearing it as the aircraft of British Airways and British Midland pounded the hold, waiting for the visibility to improve! Similarly, that same aircraft on final approach had a distinctive operatic calling card that you could hear and identify from miles away. The HS748 had a quieter but not hugely different sound on final. Other Dart-powered aircraft sounded totally different.