Airline flight path

Mrs. Plant flew to Long Island today. Watching on a website, I noticed that Southwest flew from Baltimore West out to sea, north east and then north to Long Island. Why didn’t they fly in a straight line East North East from Baltimore to Mac Arthur?

East, dammit. :rolleyes:
East from Baltimore, over Delaware, North East grazing New Jersey and then over the sea for a good while, then North for Long Island.

Northeast Corridor security? Flight path overcrowding? The pilot was scouting fishing locations? I’m betting the first two, or something similar.

I would imagine that most questions about “why’d they route that airline flight that way?” could be answered by some combination of:

(1) understanding “great circle routing” (http://en.wikipedia.org/wiki/Great_circle).

(2) being aware of restricted airspace regions (various military-only corridors and/or you-can’t-fly-over-Camp David corridors);

(3) air traffic control considerations (which include not having everyone vectoring in on the same single “most efficient” line at the same time – i.e., building in “planned inefficiency” from lazy indirect loops, rather than possibly-much-worse "unplanned inefficiency from having to have every plane circle the field twenty times at peak hours; air traffic considerations also include whether particular weather patterns/winds favor/allow/require a particular runway approach/approaches).

Commercial aircraft are flown on airways which are the airborn equivalent of highways. They don’t always go direct, mainly to facilitate separation from other aircraft. Aircraft may also divert to avoid weather, particularly thunderstorms.

Looking at her ticket information, they were ten minutes early.

I just read something about this. It turns out airplanes fly from beacon to beacon. They could save billions in fuel costs by flying straight lines using GPS but they’re not set up to do so, and the process of making it possible would cost a lot of money.

I was under the impression planes were allowed to GPS navigate now. If not that’s kind of silly.

Regarding beacon “highways”:


And regarding GPS systems: http://blog.wired.com/cars/2008/04/gps-navigation.html and http://www.usatoday.com/tech/news/techinnovations/2008-10-09-nextgen-gps-airlines_N.htm

The air traffic patterns to/from Long Island are particularly convoluted. The planes have to bypass the congested airspace around JFK, La Guardia, and Newark airports.

Ed

Airplanes nowadays have very accurate GPS systems. It’s the ATC structure that’s not prepared to have aircraft flying direct vice airways.

I don’t have the jet routes in front of me, but most likely the indirect routing was because of them. Factor in some vectors so they can get clear of the mess of airways/approach traffic coming into JFK, and active runway at MaCarthur to the west or northwest (requiring an approach from the east), and that’d result in what you saw.

Thanks!

CP

Those stories aren’t about GPS navigation, aircraft have been using GPS for navigating for ages (15 years maybe? as long as I’ve been flying anyway), they’re about using GPS derived information to provide air traffic controllers and other pilots with position information on other aircraft, which would then allow for more efficient routing. Australia has been using a version of this called ADS-B for a year or so to make up for its large areas that have no radar coverage.

GPS actually has a big flaw compared to ground based navigation aids, it doesn’t easily provide the user with advice that it’s not working. Ground based navaids such as NDBs and VORs have a morse code ident signal that is an audible indication that the station is transmitting. There are methods to determine if a GPS satellite is faulty, but they are far more complicated from a programming perspective than the simple system used by ground based aids.

Most IFR aircraft are equipped for navigation with GPS both enroute and throughout an instrument approach, however commercial aircraft with flight management systems (FMS, also FMC for flight management computer) will use a best computed position derived from GPS, AND ground based aids.

So the problem is not that aircraft aren’t using GPS, it’s that the airways structure in some countries such as the US are still based on old ground based routes. You still need those beacon - beacon routes for non GPS aircraft and for those times that GPS is not available.

I Follow Road?

Instrument Flight Rules, i.e., being able to fly in the clouds or without seeing the horizon/ground.

Operative word being “rules”. IFR aircraft follow a particular set of rules designed to maintain safety in all weather conditions. You can be IFR and not have a cloud in the sky.

It’s a joke from an ancient Reader’s Digest. :slight_smile:
Sorry, I thought it was more well known.

I recognised the joke but assumed genuine confusion with the joke being coincidence.

Variation, I Follow Rail.

To clarify, I didn’t think you actually thought it might mean “I Follow Roads,” but that you might be using the joke to get more info on IFR.

Yeah, I also thought he may not be kidding, and I didn’t want to even venture into why someone would be IFR in VMC if they didn’t know what IFR even was…