The section on range in “Handbook for Naval Aviators” does a
good job comparing the various propulsion types with respect to achieving
maximum range. While discussing
propeller driven aircraft with reciprocating engines, it mentions that engine
operating limitations may actually drive achievable range. This is indeed the case given the speed at
best L/D for the 360, for example, is about 120 KIAS (weight dependent) and it
only requires about 50 hp at low altitudes.
At such low power and low altitude, engine efficiency is rather
poor. And as Gary mentioned, we tend to
place a relatively high value on speed.
We can extract a good compromise by flying at higher altitudes. As the indicated air speed reduces with
altitude, range continues to increase.
At WOT, reaching best L/D may still not be practical due to the very
high altitude required – unless we are really, really heavy, as in carrying an
extra 350 gallons of gas. Throttling
back on power or pulling back engine speed is an option. Since power has already reduced naturally at
altitude, less power reduction is needed.
One can also simply satisfy the need for speed and accept reduced range.
I superimposed fuel economy (fuel flow taken from a
carburetor with poor mixture distribution – about a 20% hit) and indicated air
speed on performance charts for the stated conditions. Peak economy occurs very near the 120 KIAS
mark. Further reductions in power or
increase in weight will pull this point to lower altitudes.
Given all this I tend to fly high so I can save gas and
still go fast.
Chris
Zavatson
N91CZ
360std
www.N91CZ.net
On Monday, December 16, 2013 6:45 AM, Mark Sletten <mwsletten@gmail.com> wrote:
Check
Aerodynamics for Naval Aviators. The figure on page 169 and the accompanying
text on page 170 will answer your question.
--Mark