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Airways Or Direct Routes?

Sun May 15, 2005 1:53 pm

I was just wondering... recently i was flying on United and listening to the ATC on Channel 9; i was flying from FRA to SFO and about 300 miles from our destination the controller gave us an amandment to our flight plan. He said cleared direct Point Reyes VOR via golden gate 4 arrival. Now I know by looking at the charts there was no straight line between where we were and Point Reyes VOR. My question is do airliners HAVE to follow airways or are they allowed to fly in a straight line abandoning published airways or are they restricted only to airways. And what exactly does the controller mean when he says "cleared direct to..." Thanks for any info!
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RE: Airways Or Direct Routes?

Sun May 15, 2005 2:23 pm

If the aircraft is equipped to navigate direct to a waypoint (essentially, if it has wither a certified RNAV or GPS system), they can be assigned a direct routing to most any defined waypoint.

So, in your instance, even if the aircraft was beyond the service volume of the VORTAC, they could still punch up Direct To PYE on their GPS and fly it, regardless of whether it was on an airway or not.

This is allowable much more frequently because of greater radar coverage, as well as better nav systems, essentially, GPS.

Even better to come with ADS/B which will allow apprpriately-equipped aircraft to report their positions to tracking stations even where no radar coverage is available.
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RE: Airways Or Direct Routes?

Sun May 15, 2005 5:05 pm

What you have is the collision of the regulations with the "real world".

Since the FAA doesn't have "free flight" yet, all flight plans in the domestic US have to be on airways or between navaids. There is a 260NM reception limitation. However, in the real world, it's not uncommon to get cleared direct to a fix several hundred miles away. Even if you don't have FMS/INS/RNAV, you can just get a vector and it will be extremely accurate.

One note of caution, just because you're cleared direct, doesn't mean it's quicker. Most computer flight planning systems now use a minimum time track. I have flown out of the east coast only to get cleared direct to an arrival fix in the west. Once it's in the FMS, it's actually a longer enroute time, shorter distance but more headwinds.

Finally, "cleared direct" means exactly what it says. You go direct to that point with no intermediate points.
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RE: Airways Or Direct Routes?

Sun May 15, 2005 9:41 pm

I discovered this when I was multi-time building. I'd file a flight plan from Dallas to Little Rock at 8000ft in a Seminole using Victor Airways. All I had was VOR/DME, no GPS or RNAV capability. Center would tell us, "Cleared direct Little Rock" as soon as we took off and were clear of the terminal airspace... Well Little Rock was still over 150miles away and I definitely wasn't getting the VOR.

I told center, "Unable direct Little Rock." Center came back with, "Fly 060, direct Little Rock when able." So we flew 060, then about 70 miles later we picked up Little Rock and went direct to Little Rock VOR.

This happened all the time, no matter where I was flying, even though we did all the flight planning on airways, as soon as we took off we were given vector and direct when able.
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RE: Airways Or Direct Routes?

Sun May 15, 2005 10:15 pm

Keeping it very simple. Yes. Flight crews can 'cut the corners', but only with the permission of ATC...and sometimes if its busy, ATC will say no. By saying..."cleared direct.." ATC is saying, "yes, go ahead and do it"

[Edited 2005-05-15 15:17:01]
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RE: Airways Or Direct Routes?

Mon May 16, 2005 12:12 am

You also have to remember that "directs" are very rarely given outside radar coverage. Very hard to pinpoint aircraft location when they're flying offtrack without radar assistance.

That's why it is possible when you've taken off from New York, to have a direct just outside of the STAR area in Los Angeles. Very few places have complete radar coverage like the US. Europe and Japan are pretty much the only places where entire countries do have radar coverage, and therefore directs in those locales are quite common.
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RE: Airways Or Direct Routes?

Mon May 16, 2005 12:18 am

i understand now. thanks everybody for the wealth of information! happy flying.
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RE: Airways Or Direct Routes?

Mon May 16, 2005 1:53 am

You don't need to be within range of the VOR to go direct. In 30 seconds you can bust out a sectional and get a heading from your course to the new VOR.. or at least a rough idea... then when it comes in range you follow the needle! Last night I was flying to Plymouth, MI via DJB, SKY, and CRL. ATC gave me direct SKY right off my home airport, over 50 miles, but I took it and picked up the VOR about 10 minutes later, right off the nose.
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RE: Airways Or Direct Routes?

Mon May 16, 2005 3:25 am

Flight plans don't need to be filed 100% via airways, provided the aircraft is equipped with FMS, but it is good practice to do so.

Take for example BHM to DEN. I could file it via airways and such, but it wouldn't be very efficient, so I would plan on point to point and the arrival.


This is valid flight plan, since I have included a point within each center.

If the airports don't have any SID's or STAR's, that's no problem, becuase I can just file by just including a VOR or fix in each center's airspace.
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RE: Airways Or Direct Routes?

Sun May 22, 2005 7:17 am

Usually we dont say "Cleared Direct Ellwood City" (as in Ellwood City VOR or any VOR for that matter unless we know beyond a doubt that with a cessna 152 at that altititude you could recieve the navaid. We usually use the phrase "When Able, proceed direct Ellwood City". The pilot always has the ability to say unable, then we are forced to give Radar Vectors (RV's) granted it is in a Radar environment. And regarding flight plans, alot of flight plans are via VOR-VOR without a published airway. From an ATC perspective (im not a center guy so I cant say 100% for the centers) I know we like to see within 4 miles or so of the "centerline" of the route direct to the next VOR. (same width as a federal airway). Anywho hope this helps a bit.

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RE: Airways Or Direct Routes?

Sun May 22, 2005 9:01 am

In your case, destined for SFO, it sounds like for flow control your arrival runway was switched. Coming from the east, you likely would have flight planned for the Modesto arrival to SFO, for runway 28R. As things back up, and flow control is better metered, some aircraft are switched to 28L.

To arrive north of the airport and fly a left hand pattern from the west side, you would be rerouted on the Golden Gate arrival, of which Point Reyes is one of the waypoints. (A VOR in this case).
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RE: Airways Or Direct Routes?

Tue May 24, 2005 2:54 am

LongHauler, European arrivals often use the Golden Gate 4 since their route places them north of the Bay Area. The Modesto 2 arrival is most often used for arrivals from the east from U.S. cities like NY and DC. Golden Gate 4 arrivals often use 28R as well with a downwind over the bay and a right base leg for the 28's.
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RE: Airways Or Direct Routes?

Tue May 24, 2005 8:25 am

Yes, he was surely already on that arrival-- they just cleared him direct to PYE instead of via Mendocino, or some such.

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