The engine installations had to allow development of variable-geometry intake systems.
In both engine installations, cylinder heads are exposed for cooling.
Three sub-models of each variant were planned, different only in the engine installation.
The engine installation was particularly neat for a radial.
These modifications were the same standard as the D-3801 series, making them identical with the exception of the engine installation.
The engine installation was modified, and a second tailplane added to the top of the fin.
The engine installation on production models was to be slightly further forward than on the prototype.
While reliability increased, this engine installation also created more drag than the M-15 had, and performance decreased accordingly.
It uses the same engine installation as the LS8-st.
The airframe was completed in 1994 and engine installation commenced.
