Comparison of Best Economy and Best Power Mixture Settings in the Purdue University Training Fleet Revisited

Best economy (lean of peak or LOP) operation of aircraft engines rather than best power (rich of peak or ROP) has been suggested as a means to reduce fuel consumption in light aircraft with modest speed reduction leading to reduced operating cost (increased miles per gallon), and to reduce cylinder head temperatures (CHTs) leading to improved engine longevity and reduced maintenance cost. A recent study by Chrisman (2011) using a limited number of data sets from aircraft in the Purdue University fleet of Cirrus SR20 training aircraft demonstrated statistically significant reduced fuel consumption and reduced CHT but no statistically definite speed reduction. This study confirms the earlier results for fuel consumption and CHTs using expanded data sets. It suggests that the failure to derive a statistically significant reduction in speed is a consequence of inherent experimental limitations rather than the lack of any reduction.