The primary source of AC power for the UH-60M is provided by which arrangement?

• A. Two DC Power Packs
• B. One 3-Phase 60 Hz Generator
• C. External Power Cart Only
• D. Two 3-Phase, 400 Hz, 115/200 Volt, Oil Cooled AC Generators

Answer: (D)

Primary AC power on the UH-60M comes from two engine-driven, three-phase 400 Hz AC generators that output 115/200 V AC. Having two generators provides redundancy and load sharing, so essential systems stay powered even if one generator isn’t available. The 400 Hz frequency is used in aircraft electrical systems because higher frequency allows smaller, lighter transformers and electrical components, which is important for helicopter design. The generators are oil-cooled to handle the heat from delivering substantial electrical power in a compact package.

The other options don’t serve as the main AC source: DC power packs supply DC power, not AC; an external power cart is a ground-supply option, not the aircraft’s primary onboard AC source; and a single 60 Hz generator would not match the aircraft’s designed electrical architecture.