Hartzell Preheat

Effective preheating distributes heat across multiple areas rather than concentrating it in one location. Multi-point systems warm the aircraft's metal components, oil system, and surrounding structures to create a more uniform temperature throughout the system. This reduces cold-start stress and improves reliability.

Moisture is naturally present inside aircraft systems, particularly within oil. If only the oil is heated while surrounding components remain cold, water vapor can condense on cooler metal surfaces and lead to corrosion. Proper preheat systems warm the aircraft structure above the oil line and maintain temperatures above the dew point to prevent condensation from forming.

Cycling a preheat system on and off can allow the aircraft to repeatedly pass through the dew point, increasing the potential for condensation inside critical components. Systems designed for continuous operation should generally remain plugged in during cold weather rather than being repeatedly turned on and off.

Thermostat-controlled outlets or switches can unintentionally cycle a preheat system on and off as temperatures fluctuate. This repeated heating and cooling can increase condensation risk and reduce the effectiveness of preheating. Continuous, stable heat is generally preferred for maintaining proper temperature throughout the aircraft.

Cold-soaked aircraft require time for heat to distribute evenly through the system. Multi-point preheat systems typically deliver most of their heating benefit within the first few hours and reach full heat soak after several hours depending on conditions.

Effective preconditioning can extend beyond the propulsion system to include accessories, gearboxes, hydraulics, batteries, avionics, and cabin areas. Warming these components improves reliability, reduces maintenance costs, and helps ensure the aircraft is ready for safe operation in cold climates.

Remote activation systems such as SwitcheOn allow operators to turn on their preheat system from anywhere using a cellular connection. This ensures the aircraft is warmed and ready before arrival while reducing energy usage and eliminating the need to drive to the hangar hours before the flight.

Always follow the aircraft flight manual (AFM/POH) and manufacturer service guidance regarding preheating procedures and temperature thresholds.

Even when temperatures are not low enough to require preheating under manufacturer guidance, preheating can still reduce startup wear and improve reliability. In cool weather conditions, warming the aircraft before startup helps ensure proper lubrication, smoother starts, and reduced mechanical stress on critical components.