A recurring question about the proposed BRGHT departure is whether it asks anything unusual of aircraft or of the airspace. It does not. The FAA publishes the standard by which all area-navigation (RNAV/RNP) instrument flight procedures in the United States are designed: FAA Order 8260.58D, "United States Standard for Performance Based Navigation (PBN) Instrument Procedure Design" (current edition; it superseded 8260.58C dated 09/15/2022). The order is public and downloadable from the FAA website.
This note walks through the specific design criteria a procedure like BRGHT must satisfy, and shows — using the order's own numbers — that BRGHT sits comfortably within them. The point is narrow and honest: BRGHT is a designable, standards-compliant procedure, not an exotic request. It is not a claim that any particular ground track is already obstacle-clear (see LIMITATIONS below).
For departure legs, Order 8260.58D (paragraph 1-2-5.c(1)4) specifies the design vertical path as the higher of:
Separately, the standard (minimum) climb gradient for obstacle clearance is 200 ft/NM (paragraph 1-3-1.g(2)).
WHAT THIS MEANS FOR BRGHT: the FAA designs departures on the assumption that aircraft climb at least 500 ft/NM below 10,000 feet. Recorded BWI departures in this corridor climb at a median of roughly 1,920 feet per minute; at a typical climb ground speed near 200 knots, that is on the order of 575 ft/NM — above the design gradient the standard itself uses. BRGHT's altitude at the turn is therefore consistent with both the published design assumption and observed practice. (Climb rates and altitudes are drawn from recorded track data; see the interactive climb explainer on this site.)
For a PBN departure, the standard navigation specification is RNAV 1, which carries a Cross-Track Tolerance (XTT) of 1.00 NM (Table 1-2-1). The design assumes aircraft remain within that tolerance of the published centerline; the obstacle evaluation area is built as a primary area 2 x XTT either side of course, with a secondary area 1 x XTT beyond that (paragraph 1-2-5.b(2)).
WHAT THIS MEANS FOR BRGHT: a modern RNAV departure is a tightly held, repeatable ground track by design — which is exactly the concentration observed in the measured arrival streams at this airport. BRGHT relies on nothing more than the standard RNAV 1 performance already in routine use.
The order constructs turns from bank angle, ground speed, tailwind, and the assumed altitude at the turn (paragraphs 1-2-5.c and 1-2-5.d; formulas 1-2-9 and 1-2-10). The bank angles are specified by altitude band:
WHAT THIS MEANS FOR BRGHT: turn geometry is a function of altitude at the turn. A turn deferred to a higher altitude — the essence of the BRGHT proposal — is handled squarely within the standard's ordinary turn construction. It is not an exception or a waiver case.
This is the criterion most directly relevant to the community's concern. Paragraph 1-2-5.c(1) requires that the altitude used for turn construction be the HIGHEST anticipated altitude at the turn fix, and states plainly:
"Use of the highest anticipated altitude is required even when obstacle clearance is assured for flyability, path repeatability, and airspace/route separation."
WHAT THIS MEANS FOR BRGHT: the FAA's own design process assumes aircraft turn at the high end of their achievable altitude. That is consistent with what recorded departures actually do in this corridor, and it is consistent with the BRGHT premise — complete the climb before the turn. A procedure that turns aircraft low, while they are still climbing hard, is the departure from this assumption; deferring the turn moves the procedure toward it.
Table 1-2-2 gives the indicated airspeeds (KIAS) used in the design math. For a departure below 10,000 ft MSL: CAT A 110, CAT B 150, CAT C 240, CAT D 265, CAT E 310. These are the FAA's own assumed speeds; any analysis of BRGHT's turn radius or climb-to-turn distance can cite them rather than an outside assumption.
Taken together, the criteria say that BRGHT is buildable to standard: a tightly held RNAV 1 track (Section 2), climbing at or above the design gradient (Section 1), turning at an altitude the standard already assumes to be high (Sections 3 and 4), at the standard's own design speeds (Section 5). None of this requires special authorization or performance beyond what BWI departures already demonstrate.
FAA Order 8260.58D, "United States Standard for Performance Based Navigation (PBN) Instrument Procedure Design." U.S. Department of Transportation, Federal Aviation Administration. Available from the FAA website. Related orders referenced within it: 8260.3 (TERPS), 8260.19 (Flight Procedures and Airspace), and 8260.46 (Departure Procedures Program).
This is independent community research. It is not affiliated with or endorsed by the FAA. — TrueNoise.org