AVweb is reporting that the FAA has issued its final rule on the controversial airworthiness directive that will require the replacement of cylinders on 6,200 high-displacement Continental engines. The AD, which takes effect Sept. 15, scraps thousands of aftermarket cylinders made by ECi.

According to the AVweb report, the AD caused a storm of protest from owners, engine shops and manufacturers and prompted a long consultation process by the FAA. Even the NTSB opposed the scope and breadth of the AD. In the end, after several modifications, the FAA determined that the 6,200 engines will need all their cylinders replaced at a total cost of $88.5 million for U.S. owners, or about $11,520 per engine.