I always look with suspicion at performances charts. In my old club, we had two planes of the same type (don’t ask me which type, I won’t tell you). If you look at the published performances a cruise speed of 137 knots is listed. Our examples cruised much more sedately at 115 and 110, the older one being faster and having also a better climb rate (1,000 fpm versus 800).
Another interesting example: most sources agree in saying that the F4U Corsair was faster than the F6F Hellcat. It’s surprising, if you consider that both planes had the same engine and prop, a similar weight and wing area with the same airfoil. US Navy was puzzled, to say the least, and delivered a Corsair to Grumman, asking to make the Hellcat equally fast. Grumman test pilot discovered that the two types had exactly the same combat performances, and maintained formation at all altitudes with similar power settings, with only slight advantages and disadvantages changing sides with altitudes. The Corsair airspeed indicator, however, was constantly reading 18 mph faster than the Hellcat. The reason was traced down to an incorrectly positioned static port on the Hellcat’s fuselage. The fault was remedied, but the Hellcat speed remained listed as slower forever (and the F6F in PF is accordingly “porked”).
Who is telling this tale? Corky Meyer, Grumman test pilot who flew extensively both types (read in “Corky Meyer’s Flight Journal”, pages 68-69).
Is this fact hard enough to ask TD a fix? Perhaps yes, but I don’t feel it’s so important. What matters, in my opinion, is that published performances can vary for a lot of reasons (including different testing standards) and that a general consensus is hard to reach.
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