Tuesday, April 22, 2008

Messin' with Mr. T

If there was any doubt in your mind that this is the most obscure aviation blog around, this post should put the issue to rest once and for all. After my last post that included some information about T-routes, I got curious about the routes that have been proposed for the San Francisco and Sacramento areas. A little searching uncovered Federal Aviation Administration 14 CFR Part 71 Docket No. FAA-2008-0037; Airspace Docket No. 07-AWP-6, Proposed Establishment of Low Altitude Area Navigation Routes (T-Routes); Sacramento and San Francisco, CA.

A couple of things about this Notice of Proposed Rulemaking. First, the public comment period has expired so it seems doubtful that there will be any further public input. If you feel left out, keep in mind that most pilots to whom I've spoken hadn't heard of these proposed T-routes either. Another fascinating aspect of this proposal is that I could find no depiction of the routes, just the waypoints that define the routes and their Lat/Long coordinates.

Using a Mac-based mapping program and a San Francisco Sectional raster map that I purchased and downloaded from NACO, I entered the waypoints and created some maps of these routes. I couldn't find any reference to the proposed minimum en route altitudes for these routes, which would be really good to know about since the smaller aircraft that will probably use these routes tend to be susceptible to airframe icing.


Here's T-257, which routes you from the Big Sur VORTAC to the Point Reyes VORTAC. I'd previously thought the waypoint SUTRO was just west of the ADIZ (Air Defense Identification Zone) and that the route was quite a distance from the shore which would entail more risk for single-engine aircraft. However an astute reader pointed out an error in the lat/long that as specified in the NPR. This route is very close to a direct route between Point Reyes and Big Sur.

Here's T-259, which gets you between the SAC VORTAC and the San Jose VOR. This route looks pretty good to me, but again I have no idea what the MEA is for this proposed route.

Here's T-261, which could be handy for getting from Half Moon Bay to points east, across the SFO and Oakland arrivals. Again, no MEA seems to be available.

Here's T-263 which gets you from SUNOL to the Scaggs Island VORTAC and points northwest and vice versa. This route is basically the radar vectored route you get when you are arriving into Oakland or Hayward on an IFR flight plan from the northwest. When the Bay Area is on the Southeast Plan, this route might allow you to get on top of the arrivals to Oakland and SFO, rather than being sent to the northeast side of Mt. Diablo and then up the Carquinez Strait. Keep in mind that all of this is pure conjecture at this point.

This all seem reminicent of the NPR for the Leemore MOA that was recently created, a process that was only slightly more publicized. Of course the difference is that these T-routes will provide something that the average pilot might use rather than defining airspace that pilots should avoid.


Eric said...

Great content on T-routes so far, John - this is interesting stuff with amazing potential.

Interesting side-question: the new blue GPS MEAs listed on existing Victor airways (5000G on V27 between AST and DANES, for example) are described in the legend as "GPS/WAAS MEA". T-routes, on the other hand, are simply "Low Altitude RNAV Route GNSS Required".

As I understand it, any current IFR enroute GPS will allow you to fly a T-route, but the only place G MEAs are labeled seems to be the legend, which suggests WAAS is required. The pairing of "GPS/WAAS" instead of "GPS or WAAS" makes me think that it's much like the "VOR/DME" concept, but there doesn't seem to be any additional information anywhere but the Low Enroute Chart.


Dave - PP ASEL IA and geek said...

Looks like the docket is off by a degree of latitude on SUTRO. AirNav and the FAA-NACO ATA-100 data list SUTRO at 37-42-43.350N, versus 36[deg]42'43'' N in FAA-2008-0037. The fix is also described by SFO287r10, or where V199 (/V25/V150) intersects the 10-mile ring of SFO's Bravo, which makes it easy to pick out on the sectional/TAC...and only about two miles offshore (and about 4 mi. from Mt. Sutro). A much better route for single-engine than what the docket describes. Less than half a mile longer than direct BSR-PYE. Check it out on a site like flyagogo.net or skyvector.com.

John said...


Thanks for pointing out that error. I've added the corrected image.

John said...


I started crafting a response, but it's long enough to be a post of its own. So I'll do that in a day or so.