The oil allows to lubricate and cool down several gearbox components that are fundamental for lift and forward flight of helicopters. The heat exchanger is the component designed to reduce the temperature of coolant fluid (oil) to preserve the functionality of helicopter gearbox components. In particular, the plate and fin heat exchanger enables rapid reduction of oil temperature by air cooling by leveraging its large heat exchange area. This type of heat exchanger are the most used in helicopter design thank to their compactness and simplicity allow to maximize thermal exchange with a lightweight configuration. However, a model to predict and characterize the performance of plate and fin heat exchanger is up to now not complete available and validated.