The Riddle of Takeoff Distance

Not all performance calculations are as specific as we think.

Peter Garrison

Thursday, November 19, 2020 at 04:08 PM ET

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For the historic flight, takeoff distance was merely an educated guess. American Stock Archive

Key Takeaways:

Charles Lindbergh made a critical decision to optimize his *Spirit of St. Louis* propeller for cruise efficiency rather than maximum takeoff thrust, causing him significant anxiety about clearing the runway during his heavily loaded transatlantic flight.
Accurately predicting takeoff distance was a major challenge in early aviation, with Lindbergh's experience highlighting the unreliability of calculations and prevalent misconceptions about factors like static thrust.
Later research, like Edwin Hartman's 1936 study, clarified that sustained acceleration and propeller efficiency in the later stages of takeoff are more critical than initial thrust, and modern computational methods now confirm Lindbergh's "guess" was ultimately successful.

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In Spring 1927, while Spirit of St. Louis was being built by Ryan Airline Company in San Diego, Charles Lindbergh corresponded with the Standard Steel Propeller Company of Pittsburgh regarding the best pitch setting for its ground-adjustable propeller blades.

The aluminum-alloy blades were off-the-shelf items, using a Clark Y airfoil and a twist distribution suitable for Ryan’s mail planes, upon which the design of Spirit was based. The Clark Y was a profile commonly used for propeller blades, not because it had any special aerodynamic advantage but because its flat bottom made fabricating blades and measuring their pitch angles easier.