Thermal Management

The Problem

Cooling systems that work on a test stand in Europe routinely fail in a Gulf summer. Aircraft and UAV programs discover thermal problems late — after the airframe geometry is frozen, after the engine installation is committed, and after the cheap fixes are gone.

Thermal management is not a radiator selection problem. It is a systems problem that couples ambient conditions, heat-exchanger performance, installation aerodynamics, ducting losses, electrical loads and flight profile. Treating any one of these in isolation is how programs end up with an aircraft that overheats in a hover, in a climb, or on the ground before takeoff.

Rotax installation on the REAH flying-laboratory platform, used to develop thermal, propulsion and instrumentation workflows.

Typical Customer Questions

• Will coolant and oil temperatures stay within limits at 50 °C ambient?
• Is the radiator or oil cooler correctly sized — or oversized, paying a permanent drag and weight penalty?
• Does the installation actually deliver the pressure differential and mass flow the heat exchanger needs?
• Is hot-air recirculation or exhaust ingestion silently degrading performance?
• What is the validated hot-day operating envelope of this aircraft?

How We Work

We treat cooling as a system with a heat budget and an air-supply budget, and we close both with evidence:

1. Engineer. Define the thermal requirement — heat rejection across the operating envelope, worst-case ambient conditions, and the critical flight phases: usually ground idle, hover or climb, not cruise.
2. Simulate. Model the air path as a pressure-differential and mass-flow balance; apply CFD where installation effects dominate — recirculation, propeller-slipstream interaction, inlet spillage.
3. Build. Turn the analysis into hardware: ducts, cooler installations, brackets, instrumented components and test rigs.
4. Test. Validate with instrumented ground and flight testing under representative conditions, so simulated results become measured results.
5. Learn. Compare prediction with measurement, explain discrepancies and update the thermal and airflow models.
6. Transfer. Deliver the design rationale, correlated model, test method and acceptance evidence so the customer can sustain the capability.

Every result carries its evidence type: measured, simulated, calculated, assumed or supplier data.

Rotax Cooling Toolkit development interface for sizing coolant radiators, oil coolers and ducts. In development; engineering estimate only until calibrated against supplier and test data.

Tools and Methods

• 1D thermal and flow-network modelling for sizing and trade studies
• 3D CFD (OpenFOAM-based workflows) for installation aerodynamics
• Heat-exchanger performance modelling from supplier data and test correlation
• The Rotax Cooling Toolkit — our internal sizing tool for radiators, oil coolers and ducts
• Instrumentation planning for ground and flight thermal surveys
• Hot-climate operating-envelope analysis

Custom radiator CAD concept for Rotax-class installations, including thermostat and pressure/temperature instrumentation interfaces. Maturity: engineering concept.

Typical Deliverables

• Cooling-system requirements and heat-budget definition
• Radiator and oil-cooler sizing studies with stated assumptions
• Installation CFD analysis with pressure, flow and temperature fields
• Ducting and inlet/outlet design, from concept to prototype hardware
• Test plans, instrumentation specifications and test-data analysis
• A documented hot-day operating envelope

Evidence

REAH demonstrates its methodology through funded engineering work documented in Projects, including the Rotax Gyrocopter Cooling Demonstrator.

Boundaries and Limitations

• Every model defines its validity range; conclusions remain inside the supported conditions.
• Certification programmes receive structured engineering evidence for review by the responsible approval authority.
• Where supplier data is the only available source, results are labelled as such.