Classic Theory Meets Digital Computer; Status Quo Emerges Unscathed

A 45-year-old essay about 'Carson Speed' became a point of reference for the wonkier class of pilot.

Peter Garrison

Wednesday, May 07, 2025 at 08:30 AM ET

Verified

Edited By:

Travis Tingle

It turns out that the 'Carson Speed' is a very blunt instrument. [Adobe Stock]

Key Takeaways:

B.H. Carson's paper introduced "Carson Speed," a theoretical optimum speed (best L/D speed multiplied by 1.32) for small aircraft, aiming to maximize time saved for the least excess fuel consumption.
Carson's original theory did not account for real-world factors like improved engine efficiency and propeller design at higher power settings, which impact actual fuel efficiency.
Simulations demonstrate that the "Real Carson Speed" (maximizing the product of speed and miles per gallon) is higher than the theoretical Carson Speed for common aircraft due to these engine and propeller efficiencies.
Ultimately, the "Carson Speed" metric is a "blunt instrument," implying that flying at typical higher cruise power settings results in only a minor penalty to overall efficiency.

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The late B.H. Carson’s AIAA paper on “Fuel Efficiency of Small Aircraft” emerged unsought, like a dinosaur bone poking out of eroded Wyoming topsoil, from the scree of papers on my desk.

First published 45 years ago, Carson’s essay became a point of reference for the wonkier class of pilot, to whose vocabulary it contributed a couple of novel phrases: “Carson Speed” and “the least wasteful way of wasting.”