DEVELOPMENT OF THE S-76B PT6B-36B ENGINE ACCELERATION SCHEDULE/

The effectiveness of the digitally controlled acceleration schedule fo r the Pratt & Whitney, Canada PT6B-36B turboshaft engine (as installed in the Sikorsky S-76B helicopter) has been significantly improved thr ough the use of innovative improvements in flight test methodology. Th ese innovations have allowed the test team to optimize the engine acce leration schedule in order to maximize the response capability of the engine while retaining adequate installed surge margin, These innovati ons included (1) the replacement of the production engine control micr oprocessor with a programmable unit which provided the capability for immediate, on-site adjustment of flight critical software, (2) in-flig ht adjustment of critical control path gains and schedules in order to facilitate design optimization, and (3) the use of dissimilar engine software in the twin FADEC channels to preserve aircraft safety during test operations. Test results indicated that an optimum balance betwe en engine responsiveness and mandated surge margin had been achieved f or all flight and engine operating conditions without resorting to cos tly engine re-design.