When we sit in our aircraft, we have in front of us 120 year old pressure displayed instruments.... we also have a display that gives our geometric altitude, and a synthetic view of the world in front, including terrain alerting and obstacles. Operating into an airfield that is 6,000' up and -30C makes it desirable to actually know what your physical separation from bad days are. In this event, the crew would have received an alert that they were landing in a paddock, outside of the passengers preferred arrival location, and they would see a FPV that was aiming 1nm short of the runway threshold, the display would show the threshold moving away from the FPV at an ever increasing rate until it gets rowdy.
Point is, our safety is predicated on a weak system of communications, mon dieu, and placing the fix at the same side that is already showing problems with task saturation and process maintenance seems to be less than optimal. The people with the vested interest in arrival at the correct place in space if not time are the drivers.
At cruise, the difference is a curiosity, geometric altitude is normally around 1500' higher than the FL, but it remains quite stable for periods dependent on the airmass, on an approach, the PA and geometric altitude converge, and at around 3000' PA there is normally not more than 20' error at ISA, but as per cold temp correction factors, there is considerable difference to the uncorrected PA altitude... If the corrections are correctly applied, or the G/S is a valid (geometric) track, then the FPA sits on the end of the runway. There is no cognitive load to looking at a happy map of the world in front, and this display is specifically not corrected to PA for the very reason that we want to see real world, not someones communicated information on the local airmass characteristics.
It happens to display on an iPad, it can display on an iPhone... Could it be added as a display to any aircraft? of course, but there is no current TSO standard that would be relevant to such a display, as we are firmly committed to the 18th century in technology.
