dme arc

[RUDAS]

whoever invented the good old dme arc approach procedure,and why not just give aircraft vectors instead of making the pilots perform this tricky procedure? any atc's who know the answer?
:confused:

[Timothy]

RUDAS

Procedures are generally used only when vectors are not available (except for training purposes obviously).

Vectors are generally not available either because of equipment failure, staff shortages or just because there is no radar available at the field in question.

I think DME arcs are mainly used when you need to reposition the aircraft laterally where a straight in is obstructed (whether by terrain or other procedures) and also where the levels available over the airfield for aircraft to position outbound are limited.

An example would be the DME arc at Biggin. Aircraft cannot be positioned straight in because of LCY (& LHR?) traffic, and manouevring over the BIG to go outbound would interfere both with SIDs and missed approaches, because of the base of controlled airspace.

Timothy

[055166k]

Don't assume that Radar is always available. If you would prefer an alternative procedure then ask ATC if that is possible.

[Concrete]

In 6 years at my previous unit, I only over saw the DME arcs used at the request of the pilot. I would only have considered using them in a non-radar environment, as it would be quicker than flying a procedure from the overhead. They just got in the way and it took longer to get the aircraft on the ground when the radar was working. It could be quite amusing watching someone fly one by hand, though.

[Invictus]

An arc approach is just another means to position to final, like a procedural (non radar) approach from the overhead.

As correctly stated above, the origin is from Airfields without Radar Equipment or as an alternative to a radar vectored approach.

I (until recently) worked at a field that had overhead approaches and an ARC/ILS approach.

The arc is particularly usefull when it is designed to cater for traffic from a particular direction. That is to say it saves the distance of going overhead the facility and then doing procedure turns then going outbound etc...

Just my opinions of course


Invictus

[10 DME ARC]

Aaahh my name sake!

Well having experienced this from both ends I think its great for a non radar airfield and I also think it’s a very easy procedure to fly. As already said it allows a semi direct feed in to the procedure, ILS, NDB or VOR. It also builds in procedural separation for the controller to check i.e. “established on arc east bound passing the 160 radial”, this can be used against say departures when approved.

Its also the little man’s centre fix, cuts out all the join and procedure from the beacon.
:)

[Late Landing]

We use the DME Arc fairly regularly to facilatate arrival / departure procedural separations. It certainly makes life a lot easier from the ATC perspective. I have also used it to position an aircraft so I can sight it and then provide a visual based separation.
One question I have is can a DME Arc be joined from the inside? We have fairly high terrain some 15 - 20 nm to the north but published altitudes on the Arc do not reflect this, presumably because an aircraft joining would normally be inbound towards the VOR before turning onto the Arc (thus clear of the terrain). I have found nothing that specifically precludes the inside joining procedure but wonder whether the published Arc altitudes have been calculated to allow for an inside join and the relevant navigation tolerances applicable. Anyone have any ideas?

[Micky]

Hello
As I gather you can enter a DME Arc from either side, there for in or outbond of the VOR you are flying the arc. From sim flying (nether done it in real life...) I gather that you are flying on a certain radial in or out bound and at a certain DME distance, deepending on a/c speed you turn 90 deg. (e.g for a 9 DME Arc turn starts at 8.5 DME(outbound) or 9.5 DME(inbound))and turn the OBS 10deg. Then each time the CDI reaches the middel turn 10 tune 10. . . until LOC/GS estaplished. For WCA just watch what the DME does and applie an apropriat messure.
I found it quit fun to "fly"....
Would like to do it once for real...does anybodyknow a DME Arc app. some where in Germany or Holland/Belgium???
Was at Biggin once butwe got straight in for the ILS...:}
Hope that peace of advice helps...would be grate ful for a hint...

Thanks Micky

[terrain safe]

DME arcs are useful at airfields where the night call out staff are not atcos but afisos. They can let aircraft route directly inbound to the airfield and make an IFR approach without having to route via the overhead. This is especially useful when the said aircraft is an air ambulance or suchlike.

[tiggur]

Can an AFISO legally clear an aircraft for an IFR instrument approach?:confused:

[055166k]

No, I don't believe so. The idea as I understand it is that pertinent traffic information is given to enable the pilot to make an informed decision as to his course of action....and that the pilot will broadcast his intention/position not only for the benefit of the AFISO but also for the general information of other traffic.

[Max Angle]

We use the arc at EDI sometimes late at night when the radar is off and a few destinations abroad feature them as well, Alicante for instance. All I can say is thank god for moving maps and all the other clever electronic kit, trying to fly one on old fashioned instruments used to make my brain hurt!.

[Timothy]

trying to fly one on old fashioned instruments used to make my brain hurt!.There has also been a discussion about DME arc on the Flyer Forums (http://forums.flyer.co.uk/viewtopic.php?t=4533&postdays=0&postorder=asc&start=30) where people have also been saying they are difficult.

I don't know if I am missing a trick here, or if I could finally make my fortune by teaching DME arcs, but I honestly don't understand what is so difficult about them. I am not showing off, or being arrogant, I just can't see the problem.

The one I know best is Biggin. You turn at ALKIN at rate one, at the correct DME, and you end up on the arc +/- .3 mile depending on wind. If the number on the DME exceeds 7 you turn left a bit, if it is less you fly straight a bit (or, if it gets to be a big error, you might even turn right.)

You treat it exactly the same as the ILS or a VOR radial. As you get close the desired arc you reduce the correction and, well, just go on like that until you reach the radial that indicates the turn onto the ILS (or VOR inbound).

Maybe someone could tell me why this is so difficult? As I say, I am not bragging or willy waving, I just don't see what is so difficult. Please explain it to me.

Timothy

[jack-oh]

Inverness use arc procedures all the time. However due to wake turbulence and IFR separation they can only give out the procedure to 1 ac at a time and then must wait 7mins before they can give it out again, unless they are visual with the first ac. When it gets busy, the first ac is given the arc the remainder are given overhead procedures holding at the beacon at safe levels until the first ac is down. This slows everything up to a snails pace. Equally due to high terrain in the area the procedure for CAT C ac is flown at 14dme turning inbound on the approach radial and then descending at the FAF, at about 11nm. In good weather Inverness, invariably give an overhead procedure hoping the ac will become visual. In marginal weather, most of the pilots on the arc cut the corners in an attempt to become visual. Only in poor weather do they ever stick to the procedures like glue.

[BN2A]

DME arc's are still in regular use in LEAL, LEPA, LEMH, LEIB, amongst others...
Not a problem at all, but notice how they're all LE##.....
Any answers to that one??

:)

[Capt Nomad]

One of the easiest IFR procedures to fly of the lot.
DME arc procedures are very popular in Australia, due to lots of non-radar controlled airspace.
The arc procedure can be just as quick or quicker as a sector entry depending on what diection you are coming from.

[reynoldsno1]

DME arcs are essentially intial approach segments. They tend to save airspace. The obstacle assessment areas are 5NM either side of track. Radius should not be less than 7NM. There is no "joining" procedure as such. Like any procedure, the more you fly them, the easier they tend to get...