Originally Posted by
b1lanc
scrape marks of the left engine start 4500 feet down the runway, the right engine scrape marks begin 5500 feet down the runway. About 6000-7000 feet past the runway threshold the scrape marks end."
120kts, about 140mph, about 210 ft sec.
(ft/sec ~= 44/30 * mph, or about times 1.5)
Consistent with 8 secs at zero ft from ADSB mentioned recently.