Aircraft Overview
| Aircraft | Beechcraft King Air |
| Also Known As | King Air 90 / 200 / 250 / 350 / 360 |
| Type | Twin-Engine Turboprop |
| Engine | 2× Pratt & Whitney PT6A (various: -21 on C90, -42 on 200, -52 on 250, -60A on 350/360) |
| Electrical System | 28V DC |
GPU Requirements
The King Air family has been in continuous production since 1964, making it the most successful turboprop in business aviation history. All variants use 28V DC electrical systems with starter-generators driven by PT6A engines. The King Air uses a five-bus electrical system (on 300/350/360 models) or a three-bus system (on 90/200/250 models) with left and right generator buses plus a triple-fed bus. Starting current varies by model: the C90’s PT6A-21 draws approximately 1,200–1,500A peak, while the 350’s PT6A-60A — producing 1,050 shp — can pull 1,800–2,200A. The PT6A is renowned for reliable starting, but older aircraft with high-time starter-generators draw progressively more current as the brushes and windings age. FBOs serving King Air traffic should stock a 2,000A+ GPU to cover all variants with margin.
| Specification | Requirement |
|---|---|
| Starting Voltage | 28V DC |
| Peak Amps Required | 1,200–1,500A (C90) / 1,500–1,800A (200/250) / 1,800–2,200A (350/360) |
| Continuous Draw | 80–120A (C90) / 100–140A (200/250) / 120–160A (350/360) |
| Battery Chemistry | Lithium preferred for portable ops / NiCd cart for FBO use |
| Recommended Unit Weight | Under 50 lbs for portable / wheeled cart for high-volume FBO |
| Electrical System | Five-bus system (300/350/360) / Three-bus system (90/200/250) |
Our Recommendation
Primary pick: Red Box RB75A or Start Pac Portable 2000
The King Air’s PT6A engines are forgiving starters, but the airframe’s extensive electrical system — de-icing boots, pressurization, bleed air, and modern avionics — benefits from a GPU with strong continuous output. The RB75A delivers 2,400A peak for starting and 200A continuous for ground maintenance, covering all King Air variants from the C90 to the 360.
Alternative: Powervamp Coolspool 480 or Tronair 17-28/2000
Cold Weather & Special Operations
PT6A engines include built-in ITT limits during start that protect the hot section. In extreme cold (-25°C and below), the primary challenge is oil viscosity, not electrical power. Pratt & Whitney recommends engine pre-heat below -18°C. Use a combustion or electric pre-heater in conjunction with a standard GPU rather than relying on GPU brute force. The King Air 350’s larger PT6A-60A is somewhat more cold-sensitive than the smaller -21 or -42 variants due to its higher compression ratio.
Related Guides
For a broader comparison of GPU manufacturers, see our Best Aircraft GPU 2026 review. For battery chemistry decisions, our Lead Acid vs Lithium analysis breaks down total cost of ownership. The GPU Sizing Guide covers voltage, amperage, and duty cycle calculations for any aircraft.
Product Categories
- Battery Start Units — portable starting power
- Continuous Power Supplies — sustained avionics power
- Combination GPU — start + continuous in one unit
- Frequency Converters — 400Hz AC power
- Aircraft Tugs — ground movement equipment
Frequently Asked Questions
Which King Air model draws the most starting power?
The King Air 360 (and its predecessor, the 350) with the PT6A-60A engine has the highest starting draw in the family at approximately 2,000–2,200A peak. A GPU rated above 2,200A peak covers every King Air variant from the C90 to the 360.
Is a portable GPU sufficient for King Air operations?
For owner-operator and occasional field use, yes — a lithium unit in the 2,000A range handles the job. High-volume FBOs and Part 135 charter operators typically use wheeled carts or mains-connected units for faster turnaround and zero recharge downtime between aircraft.
Do I need to close the bus ties before applying external power?
On the King Air 350 and later five-bus models, the bus tie relay engages automatically when external power is applied, connecting both left and right buses. On earlier three-bus models (90/200/250 series), consult your specific POH — procedures vary by year and variant.
What GPU do King Air charter operators use?
Part 135 King Air operators most commonly use the Red Box RB75A for line operations and ITW GSE 2400 series for base maintenance. The RB75A’s combination of portability and output makes it the standard for King Air ramp operations across the charter industry.
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