DME arcs

[DC8 Flyer]

You also ask whether a Distance Measuring Equipment (DME) arc initial approach segment can be substituted for a published IAF along any portion of the published arc. A DME arc cannot be substituted for a published IAF along a portion of the published arc. If a feeder route to an IAF is part of the published approach procedure, it is considered a mandatory part of the approach.

Ok, maybe it's me, but that whole paragraph is either poorly written, or I have had way too much Mexican food this weekend. I get the meat and potatoes of it, no intercepting an arc anywhere but the beginning. But the feeder route reference throws me off. A little enlightenment maybe?

http://www.naco.faa.gov/d-tpp/0602/05187VG17R.PDF

There are no feeder routes to the arc. How is one supposed to get to the beginning, assuming no GPS or RNAV unit (I know one in the same). You could fly to the VOR and then fly outbound on either the 071 or 269 radial, but what's the point? If you do that just go outbound on the 003 radial (which is a feeder route to blits). I do know that there is a victor airway that runs through the NE section of the arc on about the 020 radial or so. Other than the Avbug's letter, why not, if you are inbound on that victor, simply intercept the arc and fly the approach from there. I know I know, because the Admin said so, I get that, but operationaly it makes no sense.

Now, that letter was written in 1994, a bit before GPS was making a big showing, especially in the instrument approach world. Every GPS unit, even FMS units, have the ability to "move" the arc. Bendix units will redefine the IAF to be the point on the published arc that your current ground track will take you to. It will only do that if you are on a ground track that will intercept the arc on a published portion. Garmin units simply activate the whole arc (make it magenta). What I don't get, is if you are not allowed to intercept the arc anywhere but at the published IAF, why do these FAA IFR/APPROACH approved units have that function built in and have instructions on how to do it. I realize that is in no way the FAAs way of telling us pilots that we can intercept arcs anywhere, but it is a curious "thing".

I realize ATC can vector us to an arc, and maybe that is what the function is for in these GPS units. Anywho, off to find more Mexican food....

 

[avbug]

Arc's aren't just used for approaches.

Arc's may also be part of a feeder route.

 

[DC8 Flyer]

Arc's aren't just used for approaches.

Arc's may also be part of a feeder route.

I gues I have never seen that (doesnt mean it doesnt exist, just never seen it) I have seen an approach that is one continuous arc to the runway.

I am wondering if the person that wrote this letter misunderstood what was being asked, although I am not privy to the actual question. It would seem that if the FAA didn't want pilots intercepting arcs anywhere but the IAF on the arc there would be an easier way to answer the question. Or maybe I just have too simple of a mind.

Do you have any examples of an arc being part of a feeder route, that would be interesting to see. Also, any opinion on the GPS units being able to move the arc?

 

[CloudyIFR]

So AVbug what you're telling me is that in the case of the HLN plate if I want to get on the arc and I'm coming from the East then I'll have to make a 180 degree turn and the end of the arc and that would be legal to do?

Thus if you like burning up time and fuel if coming from the East then the arc is worthless.

Thanks for everyone's input.
CloudyIFR

PS By the way, the USAF TERPS allow you to enter wherever you like as far as I can interpret. I was never a USAF pilot, only an avionics tech, now retired and living the dream!

 

[Blackjet]

PS By the way, the USAF TERPS allow you to enter wherever you like as far as I can interpret. I was never a USAF pilot, only an avionics tech, now retired and living the dream!

Unless otherwise stated or given instructions from the controller, the ARC may be intercepted from anywhere. At a distance = to 1 to 2% of your groundspeed (150KIAS = 1.5-3.00NM), turn 90% and intercept the ARC. If you have an RMI, just turn 90 degrees and keep the needle pointed 90 degrees to your direction of travel. If you are getting blown towards the fix the ARC is based off of, put in some correction and if you are getting blown away from that fix, once again, put in correction. It really is just that simple. DME ARCs happen to be a great place to use the A/P in HEADING mode.

 

[A Squared]

There are no feeder routes to the arc. How is one supposed to get to the beginning, assuming no GPS or RNAV unit (I know one in the same).

On the airways. To OTEJE via V191 from the Thief River Falls VOR and the OTAXY on V430 from Devils Lake VOR

 

[CloudyIFR]

What if you're coming down V171 from ROX VOR and 30 miles out you go direct to OTEJE, can you make the approx. 150 degree right turn to the arc?

I just don't see why that if you're at the MEA of 2,900' you just can't stay on the airway to the VOR and intercept the arc. Yep, you'll be 400' high but if you can easily lose that altitude. Also, isn't it safer and more likely to stay within the protected airspace of the arc making a 90 degree turn onto the arc versus 150 degrees? All depends on the gruondspeed.

Also, if ATC says, cleared for the approach via 12DME arc they will not expect you to go to OTEJE, they'll expect you to go to the VOR till joining the arc there.

Seems there's a disconnect from the Chief Counsel, the FAA, the USAF and pilot's in general.

Thanks for the nice discussion and staying on topic.

Me

 

[nosehair]

Seems there's a disconnect from the Chief Counsel, the FAA, the USAF and pilot's in general.

Thank you for acknowleding that fact. The Chief Counsel got there by not answering operational questions. He's a lawyer. He/They know how to legalspeak; they answer a question about a rule/procedure, and they answer with the exact same words in that rule/procedure. They are not gonna tell you that you can cut a corner, no matter how safe and practical it is.

They (the FAA) are not gonna come after you either. They can only come after you for violation of a regulation. Find the regulation that you can be violated with and you will have your answer.

 

[81Horse]

Okay, I'm going to own up to my lurid distant past: I once was an air traffic controller, and once upon a time I worked in a NON-radar approach control tower. Back in the day, DME arcs were used all the time at such places for the very reason we've been discussing: no PT's. (Arc transitions can be time-consuming, though.)

I can tell you it was common to allow arc intercepts inside the IAF; even an off-airways intercept can be positively positioned by asking the pilot to report the radial he's crossing on the arc.

Once established on the arc, inside the IAF, you are on a published segment of the approach. As a controller, I'd have been flabbergasted if a pilot had asked to return to the charted IAF on the arc and make a 180. I mean, WTF, over??

I don't know what planet that FAA opinion-writer flies over (if he's a pilot at all), but it's not Earth.

Somewhat off-topic: when a radar is finally installed in a non-radar terminal area, it turns for some time before it's commissioned for ATC use. You should see what pilot nav really looks like sometimes -- it would scare the hell out of you. Holding pattern entries? Hahahahahahaha ...

 

[avbug]

It may not be earth they're flying over, but it's on earth that the FAA Chief Legal Counsel will oppose you during the appeal process following enforcement action...and the legal interpretation is the teeth to do so. Disconnect or not.

Reality, vs. not.

Lots of pilots live with their heads in the clouds under the blissful assumption that the Administrator has better things to do than violate them for what they consider trivial humdrum. I can tell you from personal experience that is definitely not the case. For many inspectors, it's their entire purpose for being.

I know an inspector who violated a pilot for this very thing; failing to fly the full proceedure. He happened to be at KJAC when he saw the pilot do it and then proceeded to approach the pilot on the ground after he landed. Busted. (It wasn't an arc).

Did he violate six airmen, or was it just five? He honestly doesn't know, himself. But you gotta ask yourself one question. Do you feel lucky, punk? Well, do ya?