When the aircraft are west of Chicago, the western US airspace has a grid pattern of blandly-named, unpronounceable navigation fixes to facilitate flexibility in NRP flight planning. These are referred to as High Altitude Redesign (HAR) fixes. Under NRP rules, airlines may file these HAR fixes to help them make the most out of a headwind or tailwind and/or to avoid thunderstorms or military training airspace. These flights are conducted with advanced GPS navigation, and none of these fixes require any ground based facilities. Some airlines use these fixes more than others. Many choose to fly coast to coast, clearly not in a straight line, under NRP rules, and use only ground based VORs the whole way, keeping the same zig-zagging routes that NextGen will supposedly solve by eliminating VOR navigation. Our current system appears to meet the needs of airlines attempting to save money by flying fuel efficient routes of their choice.
From an ATC standpoint, any aircraft with "NRP" in the remarks of their flight plan should not be given any shortcuts, unless requested by the pilot, and if we have to change their altitude or route due to other conflicting traffic, we are supposed to return that flight to its requested route and altitude as soon as possible.
So let us review a few flights that fly from Boston to San Fransisco in the mid-morning everyday.
Feb 14th
-----
UAL719 B757 (United)
Departed Boston at 8:20am.
Filed NRP over Sault St. Marie, then to Minneapolis, airways to Rock Springs, WY, and then Coaldale, NV for the arrival.
Time enroute, with some vectors by Oakland Center: 5:30
-----
AAL183 B757 (American)
Departed Boston at 8:26am, Six minutes behind United.
Filed NRP over Canada in a similar fashion as United, but only as far north as Green Bay. They used a few of the HAR fixes (KP87G, KP81A, KD66S, and KU54M) to connect Green Bay with Medicine Bow, WY and Myton, UT.
After getting a few vectors, as well, approaching SFO, they arrived 14 minutes after United for a total of 5:38.
-----
VRD351 A319 ("Redwood" Virgin America)
Departed Boston at 8:59am, 33 minutes after American.
They filed over Canada as well, but not quite as north as Green Bay. They used 6 HAR fixes to get to Delta, UT. They were also not vectored quite as much by Oakland Center, but given a few wild turns by the approach control.
Total time en-route: 5:40.
-----
JBU631 A320 (jetBlue)
Departed Boston at 9:46am, 47 minutes after the Virgin.
They joined the Canadian party as well, but instead of flying over Utah and approaching SFO from the east, they chose to stay north of everyone else, flying over Crazy Woman, WY (everyone loves that VOR for some reason) to Reno, NV and then joined the arrival from the north. They started south, and ended up north.
They received a big vector to final by approach, and still matched AAL183 with a time en-route of 5:38.
-----
For more perspective, lets look at UAL719 from the day before:
They filed over Syracuse and remained south, compared to the next day, until Utah. However, they either didn't request NRP rules, or they requested a shortcut, because they were cleared direct ONL (O'neill, NE) while climbing out over MHT, and then Cleveland Center gave them direct Coaldale, NV. They were given a brief vector over Nevada, but the most straight-in approach. Gotta love Saturday morning. Still, the flight took 5:45.
-----
Lesson: Using "old-fashioned" VOR navigation doesn't always hinder a flight and force the airlines to lose money. Flying direct routing doesn't always mean the fastest flight time using the least amount of fuel.
Thanks as always to Flightaware.com!
Till next time....
DM
10 comments:
Very insightful as usual - thanks for sharing this!
Ah, saturday morning, so that one probably didn't go south because the ATCAAs were active...
Dave
Actually Dave,
going direct ONL stays south of our ATCAAs, which were active alot that morning for some reason. It was all south compared to the GRB/SSM stuff they filed the next day.
The point was when they got direct to Nevada, it took longer.
DM
Times all look about the same and what we find from PHL to SFO. Wonder if airlines are finding lighter winds and thereby able to fly at the same speed but with reduced power, saving precious fuel.
There are a million variables. You've only accounted for a few.
Having the option of "free flight" will also never hinder a flight or waste money on a single isolated flight.
I know there are other unmentioned variables, including the financial state of an airline and how slow it flies to save gas.
My point is that "the current system is outdated because planes have to fly longer routes from VOR to VOR" isn't the problem. Our solution is also already in effect and not always used.
How can the system be designed so that EVERY company can fly how they want and not get in someone else's way?
Thanks for reading!
I was hoping for more from this blog post. As an airline dispatch that files NRP as often as possible, I was hoping to learn how that impacts your job as a controller.
There can be a million reason for a difference in en-route times. The B757 tends to cruise faster than the A320/319.
Most airlines don't dispatch with the quickest enroute time, instead they dispatch based on the cheapest route. There is a lot of facts that influence costs. Planning a slower burn to save fuel costs. Flights over Canada get charged overfly costs, while staying in US airspace is free. The fix cost of operating a plane an hour aka crew, maintenance, insurance, lease. The long the plane is in the air, the more it costs. Sometimes its cheaper to burn more fuel to fly faster because of that. Luckly we have computers that figure it all out for us.
"There can be a million reason for a difference in en-route times."
The direct-ness of it isn't generally the deciding factor. That is my only point.
From an ATC standpoint at ZBW, we don't shortcut NRP flights. Also, if airlines are flying northerly eastbound routes, the UCA sector will work ALOT more airplanes.
Other than that, that's it.
I was a controller at ZAU and ZMP, total 21 years on the boards. NRP means Not Really Pertinent. I would mention to pretty much everybody in my airspace that direct routing was available and whoever asked got as far as they wanted directly. This was my way of promoting Free Flight, helping the user, getting the A/C on their way and out of my sector. Some of those higher-ups in the FAA support this thinking. Some don't, especially those that want to think they still have a say about controlling A/C, albeit from a desk writing rules in a book.
The folks who did not give directs usually kept flights on the hiways in the sky and usually got tubed trying to give 1 plane a 4000' altitude change because EVERY plane was on the same friggen airway.
Having worked an arrival sector at ZAU I understand the need for lining up flights a good distance from the approach boundary. I recognize the need for following a rigid proceedure. Away from that, let 'em rip! I got paid good money and am now enjoying retired life because I could keep them apart, both rigidly lined up in congested space and flying direct away from the crowded spaces.
"How can the system be designed so that EVERY company can fly how they want and not get in someone else's way?"
Computer/Self separation and free flight.
You asked.
It'll cost us a trillion dollars to reduce delays by 0.5% and fuel burn by 1%... but it sounds so sexy!!! Especially when I can contract it out to my future employer! Plus I get to fire all those darn air traffic controllers. Just so long as the midairs are between airliners with the hoi polloi inside and not the biz jets that I fly, we're A-Okay!
Post a Comment