Blade inspection method

Blade inspection method is a system to detect cracks in the main rotor blades. The method involved pressurizing the interior cavity of the rotor blades. If a crack is present, pressure is lost and a red indicator on the rotor blade root end was tripped. Later, the BIM system was connected to a cockpit display. BIM allowed only flawed rotor blades to be swapped out. This method has been used on Sikorsky's S-61 series and some later helicopter models.