wrote:

this leads me to a very simple question: on a standard day, without
any winds, what would be the optimal altitude for [cruise] speed in a
normally aspirated airplane? is this best altitude dependent on
aircraft to a first-order, or is it fairly constant across airplanes?

It varies from aircraft to aircraft; it's basically the point at which the
engine is putting out 100% rated power at full throttle. It tends to be
somewhere between 6,000' and 9,000'. From memory of the manuals, it's 6,500' for
a Cessna 150J and 8,600' for a Maule MX-7-160.

George Patterson
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