When
Brent Regan and I were racing his Lancair IV Denver to Oshkosh (1996,
97 as I
recall), the descent profile was Mach limited initially starting at
27,000 feet
using a hard limit of Mach 0.58. This was chosen because the factory
aircraft was test flown to Mach 0.6 and we did not want to enter the
unknown. This Mach number (I had to compute it in those early days –
no Mach displays then) was held until the IAS built to Vne (274 knots
IAS) and
this IAS was held to the bottom of descent, all occurring at 90-100%
power. The
maximum cruise speed at 27,000 was about 320 knots TAS (corrected for
temperature and compressibility effects) and Mach 0.52. As I recall, it
only
required 200-300 feet per minute initial descent at the high power
setting to drive
the Mach number up to 0.58, so the descent started out very flat, and
the built
up as the air got thicker. I think we hit Vne at about 12-14,000 feet
and
the maximum descent rate near the bottom of descent was off scale on
the
VSI. It sounded quite different from cruise and caused the hair on the
back of the neck to stand up a bit particularly since much of the
descent was
in IMC.