[QUOTE] If you have had the chance to see any jet
QRH performance page indicating Vref speeds for
different flap settings, you will notice that no
correction is provided for altitude. Vref is
determined from 1.3 Vso and the absence of any
altitude correction implies that INDICATED
stall speed is not affected by altitude. For every AOA there is a corresponding IAS. In
addition, the coefficient of Lift does not vary with altitude for the same IAS. Since we as
pilots have only the IAS Indicator, Stick Shaker and maybe the AOA sensor, the calculation
of TAS Stall speed is not critical. However, you should know that TAS Stall speed will vary
with altitude. [\quote]
Sorry, but you cannot derive information about the
aerodynamic behaviour of an aircraft from the
QRH. The aerodynamics determines what goes in the
QRH, but you can't go backwards, and you
certainly should not generalise from a QRH to the
underlying theory.
Stall speed is quite definitely affected by
altitude - whether IAS, CAS, EAS or TAS. The Mach
number effect is real, and is presented in the
stall speed charts of our aircraft (we quote
stall speeds for SL and 15,000ft)
If a single Vref has been chosen this is because
the plane is likely only certificated for
landings at low altitudes, and the variation in
stall speed is small. The Vref will have been
then defined by the highest stall speed in the
altitude band. It *could* have been defined as a
function of altitude, but it was probably only a
knot or so variation so the manufacturer decide
to swallow the effect in the interest of
simplifying the charts.