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Originally Posted by LN-KRF
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En del interessant å lese om været, her var det mye facts og lite spekulasjoner. Så ble jeg gjort oppmerksom på en av kommentarene av en annen.
(Min utheving)
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FAR 25.341 which governs the (U.S.) certification of commercial airliners specifies gust encounters per the following: (5) (i) At the airplane design speed VC: Positive and negative gusts with reference gust velocities of 56.0 ft/sec EAS must be considered at sea level. The reference gust velocity may be reduced linearly from 56.0 ft/sec EAS at sea level to 44.0 ft/sec EAS at 15000 feet. The reference gust velocity may be further reduced linearly from 44.0 ft/sec EAS at 15000 feet to 26.0 ft/sec EAS at 50000 feet. While I have not checked, EASA (the European regulatory agency) probably has an identical requirement. And though we do not know which gust condition is critical, whether a 44 fps gust at 15,000 ft or at the knee in the 20,000 to 30,000 ft range where the airplane's redline shifts from a knot limit to a Mach limit and the dynamic pressure is the greatest or at the maximum cruise altitude, the maximum tested vertical gust is 44 fps or less. In practice, the airframe would be tested to loads 50% higher than the maximum expected. To take a SWAG, the energy level in a 54 fps gust would be roughly 150% of a 44 fps gust. And reading from your weather analysis of AF447, the flight very well may have encountered a gust exceding 54 fps (37 mph).
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26 ft/sec = 1560 ft/min = 8 m/s
44 ft/sec = 2640 ft/min = 13 m/s
54 ft/sec = 3240 ft/min = 16 m/s
26 ft/sec er overraskende lite med tanke på hvilke krefter som er i sving i slike værsystemer. Siden dette endrer seg lineært betyr det jo også at det er bedre å fly lavere når det er dårlig vær, da flyet tåler mer enn på makshøyde.
Relatert - B52 som fikk ristet av halen i turbulens:
http://www.talkingproud.us/HistoryB52NoTail.html
Nå er dette for mange års siden, men artikkelen illustrerer hvilke enorme krefter man kan treffe på.