 The one shown in the photo is over 31 inches (1.2 m) in diameter, and rotates up to 3800 rotations per minute (RPM).Fan disks must withstand the centrifugal force of the attached fan blades.Because of their size and weight, a failed fan disk can severely damage an aircraft, as happened with United Airlines Flight 232 in 1989.While operating there is increased aerodynamic loading on the fan disk while the fan blade tips are traveling faster than sound.