Microlight flyers are protesting about a tightening of rules they say could ground them or force them to pay thousands to replace perfectly good engines. The Civil Aviation Authority has toughened up on a rule that determines when a common type of engine needs overhauling, complicating annual safety checks. Pilots say that inspectors have begun refusing to approve planes with engines that are beyond a certain age or running time. South Canterbury pilot and microlight inspector Russell Brodie says the change means he faces being grounded in a few months.