|
Salutti tutti
Jeff, surely you've seen one of these before? This
particular diagram comes from "Flying the Big Jets". Lighties have one also. In
times gone by for the purpose of design calculations a figure of 30fps was used,
nowadays the figure is 50 fps with allowances for gust onset and aeroplane
response. The top of the green arc of the ASI is the structural limit, get hit
by this hypothetical vertical gust at or below the top of the green arc and the
vertical acceleration ie G, is within the normal load limit of the aeroplane,
above the green arc and you're flirting with the ultimate load
limit.
If the figures given inadvertently by Brent Regan
for the IVP that clapped wings in a thunderey can be taken at
face value, the difference between the aircraft's flight path and
the ROD indicate the aircraft was in a downdraft of close
to 100fps ie 6,000 fpm. Read one of Macarthur Job's books "Air
Disaster", vols I, II, III, I can't remember which, and you'll find a write
up of a jet airliner flying in the lee of Mt Fuji that encountered a
gust later calculated by clever investigators at 140 fps (8,400fpm) which
removed the vertical stab and tail feathers.
I agree entirely with your comments about the
exercise of (better) pilot judgement, but as I'm sure you know many if
not most aircraft accidents are the result of a chain of sometimes
insignificant events that lead to the accident site. Break the chain and the
accident is prevented. Pilot judgement is a major factor in the chain but
undesirable aircraft characteristics and lack of pilot knowledge of these
characteristics are undoubtedly a factor also.
Chronological age equals my (European) shoe size,
all facts and figures are subject to correction....
...keep 'yer tips up.
ciao
Roberto d'Italia.
|