A few misconceptions are rearing their ugly heads again. Lets make sure our
postings are correct. If in doubt, don't post it. Others will take it as
truth and you'll hinder their education.
L/D does not degrade at high altitude due to flying at a higher speed and
"floater" sailplanes do as well as "glass slippers" in high altitude wave
conditions. Max L/D is a function of flying at the best L/D angle of attack,
which equates to a given IAS (not TAS). At 25,000 your TAS will be a lot
higher, but your stall speed, min sink speed, and max L/D speed will still be
at the same IAS speeds as at lower altitudes (keep in mind that these are
really AOA's you are trying to reference). Your stall IAS is the same at
25,000' as at 500'. You don't need to fly faster at high altitudes. Vne
(redline) will come down at higher altitudes since this is usually a flutter
speed and is based on TAS. So Vne, referenced on your IAS indicator, will be
lower at higher altitudes. In jets, the limit will be critical Mach number at
high altitudes that forms the top of the "coffin corner".
Ben Clerx
Ex USAF, now B-777and Extra 300
(and also Discus and ASW-28 competition sailplanes)
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