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Old 15th Aug 2015, 20:05
  #69 (permalink)  
7478ti
 
Join Date: Sep 2011
Location: Mercer Island WA
Posts: 139
Which RNP .1???

Sir, ...You say your RJ is "Capable of RNP .1". But Which RNP .1??? Straight-in??? It isn't adequate to just have some measure of accuracy under normal conditions, to fly some limited brief LNAV "straight-in" segment and claim RNP.1 capability. Instead, you need to be able to fly ALL the LEG TYPE combinations needed at RNP .1 (which there is NO evidence yet that any RJ can meet), ...meeting both the lateral and vertical RNP requirement based constraints, including for speeds, and later RTAs.

Further, this discussion isn't esoteric.

In fact, it is a core issue and key to any successful and economic and capable future evolution of the entire global ATS system. Unless these RNP based trajectories can be appropriately flown 3D and later 4D, with relevant speed and eventually RTA, NET, and NLT constraints, using many if not most procedures with LNAV and VNAV RNP based RF legs at low RNP, then there is no hope of economically and successfully solving NextGen or SESAR.

This is the fundamental reason why RJs are now causing such enormous pain in the entire present ATS system, and for ANSP ATS system evolution globally. Because no known RJs so far can safely, reliably, and with redundancy fly these kinds of accurate RNP based procedures, and especially not with evolving RTA elements. That is why coordinating mutually exclusive efficient RNP based flight paths into, and out of places like KSEA, KSFO, KORD, and KMDY, and KLAX, and KDFW, and KLGA and KJFK and KEWR is so terribly (and unnecessarily) difficult.

Bottom line is that no known RJs can yet do this. AT performance inherently relate to lateral and vertical profiles, and that interaction matters. And until RJs can do Real RNP at the needed low values, then successfully and economically solving and evolving ATS, at any affordable cost to users, and with the needed capacity increases, and ability to address WX deviation flexibility, is virtually hopeless.

As to "lights out", ...understanding why all this matters, may be key to your future operator and employment survival, let alone safety, ...in particular for those who may be following this thread, and who are not already retired...

Q.E.D.
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