pub const FIGURE_3_BAND: [f64; 2];Expand description
Where Martin’s figure 3 separates wings that fluttered from wings that didn’t, as D/G_E,
that is (a/V_f)²: its shaded band runs from 0.25 to 0.31.
Measured on the scan of NACA TN 4197’s figure 3 (p. 19) rendered at 250 dpi: both log axes
calibrated on their tick marks (222.5 and 224.8 pixels a decade), the band’s edges traced in
69 columns from G_E = 0.05 to 10 × 10⁶ psi (0.34 to 69 GPa; the axis runs on to 20 × 10⁶ psi).
Its middle stays at D/G_E = 0.28 to 0.29 all along, and it is about 0.08 of a decade wide. Above it lie
mostly wings that fluttered or failed, and a few that didn’t; below it, wings that flew to at
least Mach 1.3 without known failure.