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In the subsequent discussions I didn't see any mention of the fact that
stall speed increases with altitude.
Brent,
Your analysis of stall speed vs density altitude is valid but it relates to
TRUE airspeed. The decrease in air density that causes the stall speed
increase causes a lower INDICATED airspeed at a given TRUE airspeed. Until
you get up to speeds where compressibility becomes a factor, an airplane in
a given configuration and at a given weight should stall at the same
INDICATED airspeed regardless of density altitude. Adding extra INDICATED
airspeed for a high density altitude take-of or landing is not necessary.
Having said that I know that during the landing flare or during take-off
rotation we're looking outside and the intuitive tendancy is to relate
airplane performance to GROUNDSPEED. Even in calm conditions the ground is
going to be passing by much faster at the hight density airport than we're
used to down low. Under high density conditions it would be good to remember
your stall speed analysis and be mentally ready to see a higher ground speed
out the windshield, but to try to approach or rotate at the same indicated
speeds.
Better still, fly a constant ANGLE OF ATTACK on your AOA gauge.
Bill Harrelson
harrelson@erols.com
LML website: http://www.olsusa.com/Users/Mkaye/maillist.html
LML Builders' Bookstore: http://www.buildersbooks.com/lancair
Please send your photos and drawings to marvkaye@olsusa.com.
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