To bleed or not to bleed
Its a long time ago but my recall is that the Viscount, ah Dart, had compressors,leland type, which were engine driven and avoided engine bleed air but I suppose they might have been susceptible to contamination from whatever lubrication the compressors used, cant rember so maybe there was a problem after all
Having flown 737 and F100 following with interest whateverthe subject was
I know Mr Hoyt, good bloke