Helicopter Cooling, Air Cycle/Vapor Cycle Trade-Offs

Lift and flight capabilities of high performance helicopters are severely impaired when engine bleed air is extracted for the environmental cooling system. Current high fuel costs have necessitated fuel consumption efficiency improvement. Passenger helicopter owners have expressed need of improved ground cooling and pulldown performance. State-of-the-art cooling systems (air cycle machines and vapor cycle systems) are compared as to: (1) cooling performance, (2) installed shaft horsepower, (3) specific fuel consumption, (4) thermal diagrams, (5) psychrometrics, and (6) coefficient of performance.

These types are described by schematics, thermal diagrams and psychrometric plots. Since vapor cycle systems do not use engine bleed air, all helicopter performance is improved; flexibility of power source is also an advantage.