Originally Posted by
Field In Sight
I don't know why we don't crosscheck the indicated altitude with the GPS altitude for non-ILS approaches.
It would guard against large incorrect pressure settings (which I have done before).
This wasn't mentioned as a mitigation in the CAA video, which was actually quite good I thought.
Originally Posted by
deltahotel
A lot of ac don’t have GPS altitude. Ours don’t, but when the Radalt comes live at 2500’ we do a Qnh cross check along with a ‘does that make sense with the BARO alt’ check.
The GPS altitude can be wildly inaccurate at times, errors of 300FT-500FT, check it out next time if your AC has it.
One thing I am confused by, the good captain explains that even if incorrect QNH is set, the height/distance reading still comes across as
correct. Surely it would appear incorrect if the wrong QNH was set, hence this is our first line of defense?