maybe if you consider that vmcA is only valid in the take-off configuration you would understand my post.
vmc is a term that is way too generic, every phase and configuration has its own vmc. For takeoff its called vmcA, for approach/landing/go-around its vmcL, on the ground vmcG.
And you could make up a whole bunch more for other regimes.
You have to compare the applicable vmc, to the stallspeed that applies to the configuration and flightphase the aircraft is in.
The most likely explanation for a VMCA below vs is that the aircraft has been lengthened and the tailfin kept the same size for commonality. For example the a318 has a latger tailfin then the other minibuses to compensate for the shorter fuselage (arm). But still it won't be more then a few knots.
In any case I doubt it because nowhere in flighttesting do I see statements where testpilots put the aircraft into a stall in order to determine VMCA.
But as I have said theoratically you could have a vmca of almost zero if your tailfin and rudder is infinitely big or the tail infinitely long.
BTW stallspeed doesn't change that much between configurations, from clean to the first configuration the change is massive, thereafter its effect is much smaller.
Last edited by 737Jock; 15th Apr 2014 at 12:14.