The MD Helicopters MD 500 series is an American family of light utility civilian and military helicopters. The MD 500 was developed from the Hughes 500, a civilian version of the US Army's OH-6A Cayuse. The series currently includes the MD 500E, MD 520N, and MD 530F. The US military AH-6 Little Bird is based on the MD-500 series. The series of helicopters is also used by several police departments in the United States.
The MD-520N is an improvement of the MD-500 series, utilizing a NOTAR (no-tail-rotor) design, which reduces noise considerably, and eliminates the collision risk of exposed rear rotor blades.