The Captain Sim 727 is the one CS product that I can't get to work correctly in Windows 8. I get no sounds (engine sounds are fine) and a few other problem (possibly including the same one you mention).
It flies well, but of the CS aircraft (I have them all), it is the one that I have the most problems with in FSX on Win8. :(

As far as I know, the 727 is not supported on Windows 8 at this time:

MINIMUM SYSTEM REQUIREMENTS:

   - 3.0 GHz CPU
   - 2 Gb of RAM
   - 128 Mb video card (DirectX 9 compatible)
   - 2.9 Gb of free space on the MSFS hard drive
   - Windows® XP SP2 or Vista SP1
   - MS Flight Simulator X + SP2 or Acceleration
   - Internet access (for installation/re-installation)

Please note, we do not support technical issues appeared on systems that do not conform to the minimum system requirements.

Going by the above, even Win7 isn't supported, but it works very well on Win7.