Not at all confusing.
GA requirements OEI dictate Vac
Vref has to not only respect margin above stall but cannot be lower than V landing climb so if your jet struggles to make the appropriate climb with gear and flaps down the solution is to use a higher Vref speed.
Here is the bit from CS25:
Landing climb: all-enginesoperating
In the landing configuration, the steady gradient of
climb may not be less than 3·2%, with –
(a) The engines at the power or thrust that is
available 8 seconds after initiation of movement of
the power or thrust controls from the minimum flight
idle to the go-around power or thrust setting (see
AMC 25.119(a)); and
(b) A climb speed which is –
(1) Not less than –
(i) 1·08 VSR for aeroplanes with
four engines on which the application of
power results in a significant reduction in
stall speed; or
(ii) 1·13 VSR for all other
aeroplanes;
(2) Not less than VMCL; and
(3) Not greater than VREF.
Last edited by FE Hoppy; 20th January 2009 at 17:41.
Reason: addition of reference