Part Number 300SG121Q is a DC Starter Generator manufactured or catalogued by Aircraft Parts Corp. (Skurka). In some cases a proprietary airframe or engine manufacturer's part number may be assigned to identify the same unit that was manufactured by the component OEM. These rotable components generally apply to light turbine powered fixed wing aircraft and helicopters. Mechanically driven by the engine or APU with a dual purpose, the start function provides motorized torque to start the engine, then transitions to generator mode generally providing 28 VDC power with a 150-400 Amp continuous load range. These units are air-cooled and most weigh between 20 to 50 lbs, depending on specific part number. Most units are produced according to the FAA minimum performance standard specified in FAA TSO-C56a/b. The starter generator interface with aircraft is usually via QAD kit, to facilitate quick and efficient field replacement. The QAD kit or 'Quick-Attach-Detach' kit generally includes a mounting adapter plate or bell housing, with a matching ring clamp. When starter generator is removed for aftermarket MRO service, the starter generator only is usually removed - with the QAD mount remaining attached to the aircraft. The starter generator with QAD kit assembly configuration is usually purchased by the airframe manufacturer for new production installation before the aircraft enters the aftermarket. All part numbers should be verified as having qualified FAA approved installation certification and specific make/model eligibility for the intended use.