Preparing your GPU for winter
Winter exposes every weak link in a Ground Power Unit (GPU). Fuel can wax, oils thicken, batteries lose punch, cables turn stiff, and even solid-state electronics suffer from condensation and temperature shocks. This guide walks you through a practical, engineering-minded winterization approach for diesel and solid-state 400 Hz / 28 V units, written in human language, with just enough structure to stay usable on the ramp.
Fuel & the Diesel System: staying ahead of waxing
Diesel fuel changes character in the cold. As temperatures fall, paraffin molecules start forming crystals; first the fuel clouds, then filters and lines clog, and a perfectly healthy engine starves. The cure begins weeks before the first freeze: switch to a winter-grade fuel (per your local spec) or dose an approved cold-flow improver before the cold hits. If fuel has already gelled, recovery is slower and riskier than prevention. Make water your enemy too: drain tanks and separators, tiny water pockets turn to ice, expanding into blockages right when you need the unit most.
Think of the diesel circuit as a chain: tank, pickup, lift pump, filters, high-pressure stage, and return. In winter, any weak link fails first. Replace filters at the season change, verify heater jackets or line warmers if fitted, and test the priming system. Accept a small trade-off: some winter blends have slightly lower energy content, so a modest fuel consumption increase is normal. The target is not theoretical efficiency, it’s reliable delivery of clean fuel under load.
Oils, Cooling & Cold Starts: shortening the painful first minutes
Thick oil resists motion. In sub-zero conditions, the starter works harder, batteries sag, and the engine may puff white smoke as combustion struggles. Your best ally is the correct winter-grade oil approved by the engine OEM. Match viscosity to your minimum ambient, too thick and you fight the crank; too thin and you compromise hydrodynamic film once hot. Check coolant protection as a system: concentration, freeze point, cap integrity, thermostat action, any block or intake air heater. If the unit has a grid heater or glow-assist, verify pre-heat timing and control signals. Five minutes with a meter today saves a 5 AM no-start tomorrow.
Don’t neglect the basics while chasing sensors: belt tension, intake leaks, clean air filtration, and known-good grounds. Cold magnifies voltage drops and minor restrictions. A short shakedown run in cool weather-start, stabilize, light load, often reveals what a warm-day inspection hides.
Batteries: chemistry versus temperature
As temperature falls, available battery capacity drops-sharply for lead-acid. A battery that was “fine” in October can be an anchor in January. Go into winter with a full state of charge and low internal resistance. Clean the posts, treat corrosion, and torque clamps properly. For flooded cells, verify electrolyte levels with distilled water only. If the GPU sleeps outdoors in harsh climates, consider wraps or heater pads, or plan for a maintenance charger when idle. On solid-state units, remember that low control-voltage equals weak fans and erratic logic-your power electronics are only as reliable as their housekeeping supply.
Cables & Connectors: flexibility, not fractures
Power leaves the GPU through materials that hate the cold. PVC jackets stiffen; micro-cracks invite moisture; connectors seize. Choose and maintain low-temperature rated 400 Hz and 28 V assemblies that stay flexible below freezing, inspect jackets for nicks, and keep strain-relief hardware intact. Store cables off bare ice where possible, coil without sharp bends, and avoid dragging across frozen edges. For aircraft plugs, confirm latch operation, seal condition, thermal sensors (if present), and contact cleanliness. A pretty waveform at the inverter is meaningless if the last meter to the aircraft is compromised.
Routing matters. Clean paths reduce trip hazards and connector shock loads. Pair mobile GPUs with reels or guided extenders to keep runs tidy and voltage drop predictable, especially on longer leads in cold, where resistance and stiffness both work against you.
Solid-state GPUs: electronics versus winter
No diesel doesn’t mean no winter prep. Static GPUs depend on fans, sensors, and tightly controlled power modules. Cold air is dry until it isn’t; condensation forms during temperature swings, and fine frost on filters strangles airflow. Before the season, clean and replace filters as needed, free the fans, verify temperature and humidity sensors, and run a realistic load test. Watch the numbers: voltage stability, frequency accuracy, and trip thresholds. If the enclosure has heaters or anti-condensation elements, confirm they energize at the right setpoints. Seals and cable glands deserve the same scrutiny you’d give to any critical electrical enclosure.
Tie this to data. If your units support telemetry, review historical load profiles and fault codes to spot marginal behaviour before it becomes a winter failure. Digital eyes turn cold weather from guesswork into maintenance planning.
Daily Winter Practices: discipline wins
Once the frost arrives, reliability is a habit. Begin shifts with a quick visual: leaks, levels, cable condition, ice around wheels and plugs. Drain separators if needed, confirm battery charge, and do a short warm-up at low or no load before you connect a real aircraft. Keep cable paths clear and dry; cover idle units; log any odd sounds, sluggish cranking, or unstable readings. Small patterns become big failures in the cold, and yesterday’s notes are tomorrow’s fix.
- Warm-up gently, then apply load; avoid immediate full-load hits on a cold engine or inverter.
- Don’t idle a diesel GPU for long with zero load-glazing and carbon build-up shorten life.
- Store accessories (plugs, caps, short leads) in a dry compartment to prevent freeze-bonding.
Why Prepare Early: the economics of zero surprises
Winter prep is not a checklist – it’s insurance. In low temperatures, modest inefficiencies snowball into lost turns, AOG delays, and reputational damage. Switch fuels before the freeze, change filters on schedule, validate heaters and batteries, and run load tests while you still have daylight and spares on hand. Airports and handlers who treat winterization as an autumn project see fewer late-night heroics and longer equipment life. That’s real money.
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