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I would like to ask which of these options is correct:

VMCL is the minimum control speed for:

A) approach in go-around configuration
B) approach in landing configuration
C) go-around in approach configuration
D) go-around in landing configuration

I would choose B but my friends disagree due to Certification Standards CS25.19 Minimum Control Speed stating that:

VMCL must be established with -
(6) Go-around power or thrust setting on the operating engine(s).

However that doesn’t mean that my VMCL is the speed that I use for go-around, right? It just says that to establish my VMCL, I need to use go-around power as a reference.

Therefore I think that VMCL is basically just the minimum control speed during an approach in landing configuration.

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3 Answers 3

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I would go with B as well. Minimum Control Speed - Landing is for the critical case where you are in the least favourable possible configuration on approach, gear down, full flap, trimmed at approach speed, C.G. at least favourable location, etc etc, then have one engine fail and the other is put to full power. VMCL is the speed at or above which control can be maintained at that instant maximum asymmetric trust is applied, before the airplane can accelerate or the configuration can be changed. Go around speed in the approach configuration will be faster than VMCL. VMCL is the edge of the cliff.

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I think it should be

D) go-around in landing configuration.

This would have higher thrust at same speeds and configuration as B) (single engine go-around is at final approach speed without acceleration) and would thus be the more critical case. The minimum control speeds really only come into play at high thrust settings, and I read the multiple choice options to imply thrust settings (otherwise there wouldn’t be a difference between B and D).

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    $\begingroup$ There is an interesting semantic issue here. It's a pretty diabolical question. Imagine trying to parse that question if English was your second language. Anyway, doesn't D imply that the only time you have to respect VMCL is at the time a go around is initiated? My thinking is the limitation applies at all times you are in a landing configuration, ie gear down full flaps, for the possibility of full asymmetric power being applied for any reason. It doesn't only apply once the full asymmetric power is applied; it's the defense against losing control if that occurs. $\endgroup$
    – John K
    Commented Jul 22, 2018 at 20:44
  • $\begingroup$ @JohnK I agree. If I recall correctly, the only large aircraft I know where VMCL is actually a defining limit speed are the 777-200LR/F variants (short fuselage, ginormous engines). VMCL considerations keep VREF high for light weights, so - yes, the limit is inherently considered throughout approach, landing and go-around phase due to target speeds being based on VREF, but the critical point which defines the magnitude of VMCL is at the point where go-around thrust is set on n-1 engines (the nth one being dead) with the aircraft in landing configuration at final approach speed. $\endgroup$
    – Cpt Reynolds
    Commented Jul 22, 2018 at 21:21
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D) CAAS ATPL accepted Go around speed in landing Configuration.

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