Why Vy on the missed instead of Vx?

kath

kath

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Katherine
On a missed approach, you want to get up quickly to clear obstacles. Why, then, do you pitch for Vy and not Vx?

Just one of those random thoughts I had the other day....

--Kath
 
kath said:
On a missed approach, you want to get up quickly to clear obstacles. Why, then, do you pitch for Vy and not Vx?

Just one of those random thoughts I had the other day....

--Kath
Click to expand...

I think this would be somewhat dependent on the airport. At some airports, you actually have obstacles that need cleared... like mountains. There I use Vx. At others, like a lot of the ones around here, even if you go around from the ground the only obstacles may be a couple trees at the end, easily cleared. At those, I'll use Vy and get as much air under me as fast as I can.
 
kath said:
On a missed approach, you want to get up quickly to clear obstacles. Why, then, do you pitch for Vy and not Vx?
Click to expand...
On a missed approach, you are supposed to be at or above MDA/DH, which means that you should not have any obstacles immediately in your way to clear.

So generally speaking, Vy will get you higher faster than Vx (which gets you higher in a shorter distance) at a faster rate of travel. The higher and further you get away from the airport faster the sooner the controller can clear someone else for the approach and also the sooner you may get back on his scope (if you're at a more remote location).

If the missed requires a greater rate of climb, it will generally say so.
 
If obstacles or climb gradient are a factor, and Vy won't cut it, then yes, go for Vx. However, it is extremely rare for an aircraft to be unable to make those requirements at Vy off a missed approach. Maybe if you were in a nonturbo light GA plane at a high elevation airport on a hot day, but in that case, Vy and Vx have probably come close to merging anyway. That's why everyone teaches Vy initially for missed approaches -- it's almost certainly the best answer unless you're in most unusual conditions.
 
I know we IFR pilots are more precise that this, but perhaps it would give you more of a buffer between your stall speed and climb out speed?
 
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