j t:
I don't have any problems with cutting down the trapezoid a bit .. with two caveats -
(a) how do we ensure the higher manipulative standard to ensure accurate tracking in the initial OEI phase ?
Plenty of sim studies to show that the reality doesn't match the desire, even with generally high standard of manipulation crews.
Well, with the modern birds that you see populating the fleet, there are a fair number with triple IRUs, dual GPS sensors, dual (or triple) FMSes, and dual auto-flight. These are the type of aircraft than can (and are often certified for RNP AR values of 0.11 if not 0.10.).
RNP AR requires 2 X the RNP value, but for OEI purposes it could be 1 X RNP. The trapezoid would splay from the DER to the 1 X RNP value. The OEI flight path would be database driven and would have RF legs (limited to 15 degrees of bank, or less) for any track changes.
That would be the real magic from today's high-end technology.