Stuart Grant wrote:

This will take about half an
hour. My economy cruise will be max 22.5" MP or WOT and 2200 RPM. Any
advantage to reducing the RPM to 2000 or lower during the long
descent? Does it save gas?

A 200 rpm reduction will save you 2 gallons per hour in the 470. So you
will save 1 gallon.



Is it better to reduce MP and leave RPM at
2200?

Every two inch reduction in MP also saves you 2 gallons per hour.


I know the prop acts like a brake a high RPM-fine pitch. Is low
RPM and coarse pitch-more like feathering when you are going downhill?


In my 182 I always fly balls to the wall on a cross country. WOT minus
a little to tickle the needle and 2450 RPM. When it comes time to
descend I do not touch power and just roll in a turn of trim, that gets
me 500 fpm down and an extra 15-20 knots. I will reduce MP as necessary
to stay at the top of the green, but you don't have to that living out
here in the west where 26" is all there is anyways.