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 introduced "Carson Speed," calculated as 1.32 times an aircraft's best lift-to-drag (L/D) speed, to identify the cruising speed that provides the greatest time savings for the least excess fuel.
The original Carson Speed model was refined by the author to a "Real Carson Speed" by incorporating real-world engine specific fuel consumption and propeller efficiency, which are often overlooked but significant.
Simulations demonstrate that the "Real Carson Speed" (maximizing speed * miles per gallon) is typically higher than the theoretical Carson Speed, but the efficiency curve around this optimum is relatively flat, meaning typical cruising speeds (60-75% power) are already quite efficient.

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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.”