A publication of the National Air Traffic Controllers Association
Issue link: http://natca.uberflip.com/i/961329
In addition to discussions specifically about the previous Nav WG recommendations, there were numerous comments made regarding issues that were not specifically technical but were relevant to the implementation of instrument approach procedures, whether RN AV to join and ILS procedure or any other form of instrument approach procedure. These are noted below: Operational Benefit Benefits are the foundational driver for implementation of new procedures or procedural concepts. All NextGen programs are predicat ed on this paradigm. Benefits will vary by stakeholder. There will be tradeoffs in order to facilitate implementation as well as near term and longer - - ‐ term benefit returns. Traditional benefits such as reduction of block time, distance flown, predictable paths, fuel savings, and airport access, among others, play a role in the implementation of new procedural concepts. The Action Team discussed benefits that could drive the implementation of RNP to ILS procedures as well as RNAV procedures. Path constructi on using Radius to Fix (RF) legs and Track to Fix (TF) legs were discussed at length. The tasking to the VNAV AT requested the group discuss the potential benefits of an "extended final". Within the context of the Nav WG RNP to xLS operational and design recommendation there were two significant findings. First, the recommendation for design or these procedures includes an intermediate segment which is shallower than the final segment and long enough to assure glideslope capture from below on above ISA tem perature days. When aligned with the final segment, this can increase track miles by one to two miles. In designs where an RF is used for the turn to final this intermediate can be wrapped along the RF, allowing the RF to end at the FAF and not extending t he ground track. In TF overlay designs meant to accommodate earlier RJs the intermediate shallow segment cannot follow the TF turns because they are variable depending on system flying them. Second, in earlier RJ (ERJ ‐ 145 HW, CRJ ‐ 200 Rockwell) systems tr ansitioning from RNAV guidance to ILS (or LPV) guidance is a manual four step process. The Nav WG testing found that aligning the shallow intermediate with the final combined with no less than a 5 NM final allowed this transition to happen smoothly with no undue cockpit workload being added; hence those two limits are recommended when both RF and TF only aircraft are to use the procedures. The team also recommended that the intermediate be allowed to follow the RF for RF only procedures, and that finals as shorter than 5 NM not be precluded by the design criteria. The Regional operators in the meeting concurred with these recommendations, stating that their current training would support such a transition to final since they currently train to establish on the final approach course prior to making the mode transitions (this is also a limitation of some systems which require "winds level" to make the mode transition). The alignment of the temperature compensating segment with the final approach course taken alone implies longer track miles, hence a non ‐ benefit. But taken in proper context, if the procedure enables the proper level of aircraft participation with the addition of "TF only" capable aircraft, then ther e may be a greater benefit that would supersede the track mile increase, such as predictable flight paths, connectivity directly from a STAR all the way to the runway, etc. Variables such as mix of aircraft capabilities, individual airport characteristics, and benefit analysis will determine the most advantageous