Climb Speed - Almost Always Faster than Vy

[Bob - S50]

6 hours ago, Hank said:

They may be close down low, but certainly not up high. If I let my speed approach 100 mph above 8000 msl, climb approaches zero . . . Vy = 100 - 1/1000', so at 8000 msl, Vy = 92 mph.

As we climb and available excess power is reduced, even the flat part of the curve becomes more important.  The closer we get to the service ceiling the closer we have to be to Vy in order to keep climbing.

[Hank]

1 hour ago, Bob - S50 said:

As we climb and available excess power is reduced, even the flat part of the curve becomes more important.  The closer we get to the service ceiling the closer we have to be to Vy in order to keep climbing.

My ceiling isn't 8000 msl even on a hot summer day in the South!!!

[PT20J]

4 hours ago, Bob - S50 said:

As we climb and available excess power is reduced, even the flat part of the curve becomes more important.  The closer we get to the service ceiling the closer we have to be to Vy in order to keep climbing.

Remember Vy decreases with altitude and Vx increases. They meet at the absolute ceiling where that is the only speed that will maintain altitude. At high altitudes in a normally aspirated airplane, I usually split the difference between the sea level Vx and Vy and use that for best climb. It’s close enough. 
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