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Pilot Proficiency Technicalities

The Riddle of Takeoff Distance

Not all performance calculations are as specific as we think.

Peter Garrison
Verified
For the historic flight, takeoff distance was merely an educated guess. American Stock Archive
Gemini Sparkle

Key Takeaways:

  • Charles Lindbergh opted for a propeller pitch optimized for cruise efficiency over takeoff thrust for his transatlantic flight, leading to a highly stressful and uncertain maximum-weight takeoff due to the critical decision.
  • Accurately predicting takeoff distance was notoriously difficult in Lindbergh's era, as analytical methods were often unreliable and failed to capture the complexities of real-world conditions.
  • Later research, particularly Edwin Hartman's 1936 NACA study, debunked common misconceptions, demonstrating that sustained acceleration and propeller efficiency at higher speeds are more critical than initial static thrust or acceleration.
  • Despite the significant unknowns and limited scientific tools of his time, Lindbergh's intuitive judgment regarding his propeller choice and takeoff execution proved successful, a challenge that modern computing can now precisely calculate.
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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.

Peter Garrison

Peter Garrison taught himself to use a slide rule and tin snips, built an airplane in his backyard, and flew it to Japan. He began contributing to FLYING in 1968, and he continues to share his columns, ""Technicalities"" and ""Aftermath,"" with FLYING readers.

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