PPRuNe Forums - View Single Post - Your turbulence experience in different aircraft
Old 26th December 2006 | 11:12
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blackmail
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Joined: May 2003
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From: france
turbulence

hi everyone,
turbulence perception for you & the aircraft, has to do with wingloading, wing elasticy & speed.
in technical terms a vertical & also to a lesser extend a horizontal gust, increases/decreases your g loading, depending if the gust is positive(+) or negative(-).
n = 1 + (xi).delta n
n = 1 and is your loadfactor when flying straight & level, unaccelerating in smooth air. also your apparent weight (Wapp= nW) equals your real weight, because n = 1.
now comes the gust & for simplification, let's only consider a positive(+) vertical gust. loadfactor & weight go up by (xi).delta n; stall speed increases also by square root of total load factor n.
xi = greek letter & is the elasticy/damping factor & depends on the wing design & structure and engine location. note that pictures of latest aircraft designs, b787 & a350, have very pronounced upwards curved wings. normal figure = circa 0.8, so 20% of the gust intensity is already absorped by the aircraft stucture.
delta n is directly proportionnal to the gust intensity(in kts or ft/sec) & aircraft speed(kts) & INdirectly proportionnal to the wingloading [= aircraft apparent weight (Wapp) ]versus wing surface(S).
so, a jumbojet, with high elasticy wings & high wingloading, flying at the right turbulence penetration speed(Vb), is less prone to turbulence than your favourite cessna150, eg. i remember jack waddell, chief project pilot for the b747, after a test flight & when asked about turbulence, saying, "WHAT turbulence?"
kind regards, fasten your seatbelts & merry x-mas,
bm

Last edited by blackmail; 26th December 2006 at 11:23.
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