SKS777FLYER -
"I will SWAG (scientific wild-ass guess) of converting JAC's 6,300' runway length to a sea level equivalent. I would equate it to a 7,300' sea level airport. (Note that is significantly longer than the 5701 feet at KSNA. I don't recall any AA overuns at KSNA in the decades AA has flown there.)"
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I think you have your math backwards. It's not the same as a 7,300' runway, it would be the same as a 5,500' S.L. airport.
Isn't TAS affected 2% per thousand feet? If correct, and you could apply the same percentage to the field length, JAC at S.L. would be approx. 5500', or nearly the same as SNA.
SNA has rain for degraded braking action vs. JAC's snow impact.