What is "rotorfest"

Rotorfest is an all- helicopter airshow held by the American Helicopter Museum. Rotorfest is billed by the museum as the World's Largest All-Helicopter Airshow. The Airshow takes place at the Brandywine Airport in West Chester, Pennsylvania. Aircraft static displays were located on the north side of the airport around the American Helicopter Museum. The first Rotorfest was in 1996.