An Evaluation of Anti-Icing Test Results for the AH-64D Apache Block III Engine Nose Gearbox Fairing

The development of the AH-64D Apache Block III Engine Nose Gearbox (ENGB) fairing anti-ice system included several test programs to support the design and qualification of components. The results of the functional anti-ice qualification testing in the NASA Glenn Icing Research Tunnel (IRT) and system level performance demonstration in the Goodrich Icing Wind Tunnel (IWT) were evaluated. General anti-ice performance trends observed in the full-scale IRT testing were repeated during the system level demonstration in the IWT that included hardware and flow simulation differences. However, the antiice performance achieved in the IWT needs to be evaluated with caution since full-scale effects were not modeled. The engine inlet flow simulation impacted ENGB fairing anti-ice performance only when runback onto the aft fairings was present. The tunnel walls in the IWT appeared to influence the ice accretion behavior on the fairing leg sections due to greater acceleration. Additionally, higher test speeds in the IWT could not be achieved, therefore scaling of icing parameters were required to simulate conditions from the IRT. The results compared favorably between the tests indicating successful application of scaling methods. Spray cloud differences were observed for non anti-ice conditions, attributed to wall effects and differences in the included hardware and flow simulations in the IWT.