CASE STUDY: Fan Heater (Demist)

Overview

Demisting is one of the simplest-sounding jobs a heater does and one of the easiest to get wrong once an airframe has more than one panel to clear. This case study covers a fan heater solution developed for an eVTOL aircraft with two separate windscreen zones, where the challenge wasn't generating heat, but distributing it evenly enough that neither panel was left under-cleared.

Customer Challenge

The customer required an effective demisting solution for both the 'A' panel and the 'B' panel on an eVTOL aircraft, ensuring clear visibility and operational safety under varying environmental conditions.

As electric and hybrid-electric aircraft move toward more glazed cockpit area split across multiple panel zones, demist performance becomes harder to guarantee: airflow tuned to clear one panel efficiently can starve another, and any heat lost between the heater outlet and the glass reduces how quickly condensation clears in the cold, humid conditions typical of low-altitude eVTOL operation.

Our Solution

We collaborated closely with the customer to determine the optimal placement of the fan heater within the airframe, ensuring minimal temperature loss from the supply air between the heater outlet and the panel surface. Beyond placement, we provided expert guidance on the design of the air distribution system itself informing duct routing and outlet geometry to achieve a uniform demist airflow across all window panels simultaneously, rather than treating each panel as an isolated zone.

The fan heater at the centre of this solution draws on our standard duct-type heater range 150W to 6kW output paired with one of our own axial or mixed flow fans. These are the same building blocks we use across cockpit heating, windscreen defog, and remote bay heating applications, configurable for 28VDC brushless or single/three-phase 400Hz supply depending on the platform's electrical architecture.

The result was uniform demist coverage across both panel zones without compromising cabin supply air temperature, delivered within the tight volume and weight constraints typical of eVTOL airframes.

Technical Highlights

• Dual-panel ('A' and 'B') demist coverage
• Optimised fan heater placement to minimise duct heat loss
• Custom-designed air distribution system
• Configurable for 28VDC brushless or 400Hz supply
• Drawn from the 150W - 6kW duct heater range