I got the Huey last week during the sale and noticed the same thing. The FPS in DCS A10C and Black Shark 2 were in the 35~40 range during missions, but in the Huey it is averaging 17 FPS in the free flight mission. It is still smooth though, not jerky.
My specs are as follows:
AMD Phenom 1075T 6 cores @ 3GHZ (turbo to 3.5ghz)
6 GB DDR 3 RAM
AMD HD 5870 1 GB graphics card with latest CAT drivers.
Dell HD 22 inch monitor 1920 x 1080 res @ 60Hz.
Windows 7 64 Bit.
TrackIR 4
Saitek X52 Pro
CH rudder pedals
Before, my in game graphics settings were set to default high, and then I turned off heat blur and water to low, MSAA to 2X and TSAA off. Now, I turned down the graphics settings to default medium, but still no change.