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Old 20th Aug 2017, 21:36
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Jack Carson
 
Join Date: Jul 2004
Location: Durham, NC USA
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If I dig deep into the bowels of my memory back, I recollect a conversation in the Sikorsky pilot’s office discussing the Vh/Vne limits of the S-76A. Initially the S-76A was certified with the Detroit Diesel Allison 250-C30 engines. At sea level the S-76A was capable of a Vh of 155 KIAS. This was also used as the Vne. There was no reason to push the aircraft to a faster Vne. At altitude, with the drop off in engine power the S-76A’s Vh was similarly reduced. This is evident on the cockpit Vne placards for the S-76A. There was no effort to push any faster than these published Vh limitations. As a result, the level flight performance of the S-76A at altitude was not competitive with competitors i.e. AS-365 of A-109. With the development of the S-76B/C/C+ there was no effort to recertify and increase the Vh or Vne at altitude with its higher power engines. I for one always wondered if there was an underlying structural or aerodynamic issue that restricted the growth in speed performance with the increase in installed power.
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