QNH when?
When would you expect an aircraft to set local QNH when cleared from FL200 to e.g 5000 ft? (Transitionlevel is 80 in this example)
I have discussed it with a pilot. He says that he will set local QNH when leaving FL200. I on the other hand, expect them to wait until passing T-level.
From DOC4444
12. Altimeter setting procedures
12.1 Expression of vertical position of aircraft
12.1.1
For flights in the vicinity of aerodromes the
vertical position of aircraft shall, except as provided for in 12.1.1.1 and 12.1.1.2, be expressed in terms of altitudes at or below the transition altitude and in terms of flight levels at or above the transition level. While passing through the transition layer, vertical position shall be expressed in terms of flight levels when ascending and in terms of altitudes when descending.
12.1.1.1
After approach clearance has been issued and
the descent to land is commenced, the vertical position of an aircraft above the transition level may be expressed by
reference to altitudes (QNH) provided that level flight above the transition altitude is not indicated or anticipated