Ground Power Units
When an aircraft cuts its engines at the gate, it relies entirely on ground support for electricity, cabin conditioning, and engine starting capabilities.
400 Hz Solid-State Converters
Unlike standard municipal grids (50/60Hz), commercial aviation utilizes a 400 Hz electrical system to reduce the weight of transformers and motors onboard.
Mobile Ground Power Units house diesel generators paired with alternators to supply 115V AC at 400Hz, or 28V DC for smaller regional aircraft. Proper phase synchronization is critical; an out-of-phase GPU connection can trigger severe avionics protection faults.
Air Start Units
Jet engines require massive volumes of high-pressure air to spin the turbine up to ignition speed. If an aircraft's APU (Auxiliary Power Unit) is inoperable, an ASU is deployed.
ASUs house industrial screw compressors driven by high-displacement diesel engines. They deliver air at 40-50 PSI at flow rates exceeding 250 ppm (pounds per minute) directly into the aircraft's pneumatic manifold.
Pre-Conditioned Air Units
To maintain cabin temperature without burning jet fuel via the APU, PCA units supply cooled or heated air directly into the aircraft's mixing manifold. These act as giant industrial HVAC systems mounted on trailers or beneath passenger boarding bridges.