Michael Harper, the Non-Executive Chairman of BBA Aviation, is to step down from the board next year, the aviation services and aftermarket support group announced on Wednesday.He will be replaced by Sir Nigel Rudd, currently the Non-Executive Chairman of Heathrow Airport Holdings and the outgoing Chairman of tech company Invensys. Rudd will join the board in December and is expected to take over from Harper at the annual general meeting in May 2014.Harper, who joined the board in 2005 and became Chairman in 2007, oversaw the demerger of BBA Group in 2006 through which the firm became an aviation-focused firm, splitting off from the material technology division now known as Fiberweb.BC