In general, testing will involve operating at the predicted worst cases conditions for nacelle or engine bay ventilation and cooling. Worst cases can be identified using a combination of experience, judgement and the results of modelling and simulation.
Tests would normally take place on the hottest practical test day to allow extrapolation to the specified MHD (Max Hot Day). Minimum acceptable ambient temperature for testing should be agreed in advance. If extrapolation is required, the engine configuration may need to be adjusted. For example, it may be necessary to force open any coolers or ejectors that typically open/close with oil temperature to recreate the configuration that would exist if temperatures were that of a MHD. If ground tests are being used to de-risk flight tests then any weight-on-wheels logics used in scheduling of ejectors, etc., may need to be overridden. Similarly, a pre-test on a cooler day will help to de-risk instrumentation and understand general system performance before exposing the system to extreme environmental conditions or deploying the aircraft to a hot location.
The following parameters must be considered during the preparation and execution of a cooling and ventilation test campaign.