The Bell OH-58D Kiowa is a single-engine, single-rotor, military helicopter used for observation, utility, and direct fire support. It is a variant of the OH-58 Kiowa. The OH-58D was the result of the Army Helicopter Improvement Program (AHIP). An upgraded transmission and engine gave the aircraft the power it needed for nap-of-the-earth flight profiles, and a four-bladed main rotor made it much quieter than the two-bladed OH-58C. The OH-58D introduced the distinctive Mast-Mounted Sight (MMS) above the rotor system, and a mixed glass cockpit, with traditional instruments identified as “standby” for emergency use.