Originally Posted by Needles Crossed
Does this still explain the 50 knots+ increase in the low speed boundary that a B737 experiences between low and high levels? Considering such a big discrepancy, I feel that I am still missing something!
The split in stall speed isn't as big. I got some numbers today:
At 4,000ft, Vmin was 193, V Sticker Shaker was 160.
FL330 Vmin (bottom foot) was 235. V Sticker Shaker was 183.
So my sticker shaker speed went from 160 to 183.
The difference in the actual stall speeds would be even less.
As to why, I found this, which
seems to be plausible (could be a lie told to children!):
From here:
https://www.quora.com/Why-does-stall...tude-increases
Answer from Magnar Nordal, half way down the page:
The Mach number is important, because it defines how the air will flow around the leading edge of the wing, and especially how it will behave in front of the wing.
On the figure can you see that the airflow ahead of the wing is starting to split before it reaches the wing. At low Mach numbers is the distance from the point where the air starts to slip and to the wing’s leading edge relatively long.
At higher Mach numbers is the distance shorter. (At Mach 1.0 is the distance zero.) This results in a higher angle of attack, because the airflow has less time to split and flow around the leading edge of the wing. Indicated stall speed is therefore higher.
From here:
https://www.quora.com/Why-does-stall...tude-increases
Answer from Magnar Nordal, half way down the page.