Can someone please explain the correct way of flying a DME arc procedure in the 737? What would be the correct sequence of events: i.e. speed, heading changes etc? Stephen

Around the ARC Flap 5. Use the AFDS and AP in HDG and ALT HLD or VS. A good practice is to also create a ring around the VOR/DME using the fix page to give a graphical representation on the ND if you do not have the DME ARC in the FMC Database.It is an easy procedure,Rgds,

If the arc isn't in the database, a way to fake it is to create fix/radial/distance waypoints every 5 degrees or so. You'll end up remaining within the protected space of the arc that way.for exampleBAL115/10BAL120/10BAL125/10BAL130/10BAL135/10defines a portion of a 10 mile arc around the BAL vor.As with everything else, operators will vary on if this is allowed and what sort of raw data must be monitored.using the FIX page is an excellent way to put a ring around a waypoint.

Thanks GuysOk, to be sure, confirm the arc is not flown at a constant turn? I would assume the arc is flown at a constant rate turn, but from the above I understand it is a matter of turning, level out, turning, level out until the arc is completed, right? I am trying to fly a procedure but are getting closer than the DME permitted and when I shallow the turn, I get further away, thus moving outside the protected areas. Is there is general rule in the IFR world to fly a arc procedure by conventional means (needles) and not ufing the FMC to create the arc? Stephen

>further away, thus moving outside the protected areas. Is>there is general rule in the IFR world to fly a arc procedure>by conventional means (needles) and not ufing the FMC to>create the arc? Sure!By using the RMI.IF you are closing on the DME, the needle will climb, if you are going farther the needle will dive.By keeping the needle at 90

Hi Stephen,I can't speak for flying a B73NG, however for instrument rating training using a C172, one flies heading changes of 10 degrees on crossing radial at 10 degree spacings. For the C172, lead the initial turn by 0.5 nm (this will certainly be different in the NG !! :) ).I see you reference a constant turn rate on an arc. A faster moving a/c like the NG may have a chance at succeeding with this method, but trying it in a slow 172 would be impossible (low turn rate required would be impossible to achieve consistently). I'm referring here to a 15DME arc, as I fly in the full ILS34 approach at KGXY.Bruce.

Genst,Even in the B737 we fly a turn a little, straight a bit, turn a little. A comntinuous turn would have to be at about 4 or 5 degrees of bank for a 15nm DME ARC at 220kts.Someone earlier got close though to the common technique. The tolerance is +- 1nm I think and so we fly until we are about .5 nm outside the arc then turn about 20 degrees towards the station and fly straight until we cross the arc and are then about 5.nm inside it. We effectively fly the arc as a series of tangents.A good technique, if there is an azimuth aid co-located with the DME, is to keep the needle pointed just in front of the wing {= a relative bearing of 85degrees) until getting about .5nm inside the arc then turn away from the station until the needle is about 5 degrees behind the wing point {= a relative bearing of 95degrees)Hope this helps,

Hi Brad,Sounds just like the 172 in an arc! (as I had referred to). The PTS standards here are +/- 1nm in an arc, but that's more designed to see how one handles wind correction.I'm from Greymouth, NZ. Now living near Denver, CO. Christchurch sure is a nice place. :) Like your web page. Do you fly the NG trans-Tasman? Bruce.

Gidday Bruce,As you rightly say there is very little difference btw aeroplanes, after all, no matter what you fly, you just fly the seat. Beacuse there are a few hundred people behind you means they just come along for the ride and end up in the same place you do :-outtaYep I fly trans Tasman and from Aussie out to the Pacific Islands.CHC is surely the nicest city I have ever come across to live in. NZ is warm, friendly and open and I am afraid my home city {Brissy} is getting worse all the time with congestion and people losing touch with reality.. ie no time for being people any more, just rush rush rush. As a famous man once said: "And the hurrying people daunt me, and their pallid faces haunt meAs they shoulder one another in their rush and nervous haste,With their eager eyes and greedy, and their stunted forms and weedy,For townsfolk have no time to grow, they have no time to waste. "A.B Patterson.Rgds,

You're so right on the values of life, Brad.I'm sitting my IR check-ride on Saturday 11/6, and am currently in the oral study on all the weather theory, weather charts, forecasts, etc. Yuk! 2 years study and flying to get the required XC experience and training, hopefully all over this weekend! The IR is a tough one.I guess we've taken this way off topic, other than to tell the original poster that a 172 behaves just as a 73NG does in a DME arc :)Bruce.

Bruce, Let us know how it goes on the 6th. It's a tough one but as so many did before you will get through it!Michael

Thanks Michael!I will never forget back in May of this year, about to board a MidWest Express MD-80 out of KMWE. I got talking to the flight crew and was invited "up front" until dispatch, just prior to push-back. When I mentioned the IR that I was studying for (and then had just started flight training), both the Captain and FO agreed it was the hardest task they had ever accomplished (obviously a long time ago now for them). I'm ready to be done with it :)And that's born out by the original question in this post; DME arcs are hard to get right, especially with no automatics :)Thanks again for your good wishes. Now back to the low level sig prog charts :)Bruce.

Dear Tim and BradThanks for the guidance. Tried it over the weekend, but without luck.I did what Tim recommended, building fixes every 5deg apart, but the track does not "pass through" the fixes, the track goes outside the the fixes, thus flying a larger arc than anticipated.How do I build an arc in the FIX page of the 600/700, cause it keeps on telling me "NOT IN DATABASE"??? I did build my fixes in the LEGS page. I searched the net for some tutorials on DME arc procedures and guess what? They are all different, not a single tutorial explain more or less the same technique. One says fly the needle so that the VOR needle is 90deg to the track, to avoid it going up or down. Another tutorial recommends flying level, turing, level, turing etc.. So, at this point in time I'm confused as camelion on a color crayon box. I fly at 220kts then commence the turn (in this case) to the right in order to fly the 11 DME arc to a holding fix on the final approach track. The fixes I did built takes the aircraft further than the 11 DME track, although the fixes are nicely arranged in an arc shape, but the track not. I also tried the needle at 90deg scenario, but that does not work, because the needle is not yet 90deg to my track, and then I'm as close as 9 DME to the VOR, oops!!. I know I'm doing something wrong, finger problems perhaps, but can't trace the problem.Stephen

Hi Stephen,The DME ARC isn't difficult to fly, you just need to be well ahead of the aircraft and maintain good SA.It may be time I did an online tutorial on this subject. Here is a scenario:Please use Jepps plate 13-2 for NZWN.This is the same port as used in my Geezer Guide.We will of course have the AFDS doing all the work, AP A in CMD, LVL CHG and HDG SELWe are tracking 090 inbound to the NZWN VOR/DME on 112.3 (WN) for a 15nm DME ARC to the VOR onto Rwy 34. First I suggest you have the aeroplane decelerated to Flap 5 speed which is the correct initial approach speed for the 737. Given a level flight deceleration rate of about 5kts/nm at Flight Idle thrust and that we are maintaining 250kts at 3000' and want to be at say 180kts before we turn onto the ARC then we need to start winding the speed back at about 250-180=70 divided by 5 = 14nm BEFORE we get to the ARC. So we would expect that at 29DME we reduce speed. IRL I would plan to be decelerating and descending at the same time to hit my Flap5 speed as I reach my turn on point for greater efficiency but we will keep it simple for now.Hang on a sec! If we were to just fly directly at the NAVAID and then turn right through 90 degrees at 15DME we will of course end up well inside that ARC when we roll out of our turn, Blind Freddy could see that ;) . Of course you could always use the Fighter Pilot Option: fly to 15.01DME, roll 90 degrees of bank and PULL! but that would probably mean tea and biscuits with the Chief Pilot and I doubt you would be invited to sit down ;)So we need to have a think about our radius of turn at 180kts. For SIM purposes I suggest you just fly towards the DME at 180kts, note your DME and turn through 90 degrees of HDG change and again note your DME. This will give you a good idea of how much lead distance you need to start a turn and roll out abeam the NAVAID.For the technically inclined:One formula for Turn Radius is: TR = TAS Squared/3.782*G*TanAoB. So at a TAS of 180 this gives a TR of 3994' at 1G for a 25 degree bank turn (note we aren't actually at 25 degrees bank or doing 1G but it gives you a rough idea) Having typed all that you can now forget it. I start my turn on at about 2nm early. Always close enough for me :DSo 15DME + 14NM for decel and a further 2nm for turn-on lets start our decel at 31nm.. Wasn

--------------------------------------------------------------------------------This is copied from our flight school by Geoff Butler:A Circling Approach is normally made, when the executed Instrument Approach Procedure serves another runway, other than the Landing runway. This normally means decision height and visibility is much more stringent. You must not depart from the procedure unless you have the runway in sight. If you do lose sight of the airport, then you will have to carry out the missed approach procedure immediately. Some of the approaches to airfields are on DME Arc distances from the VOR . This lecture is about teaching you how to do a circling approach using a VOR/DME Arc IE vectoring yourself round an arc onto a final approach course at 16 miles out all the way round until intercepting the inbound radial. The inbound course for this exercise back to the VOR will be the 195 radial on a heading of 015 .Pick any VOR of your choice, position yourself overhead and fly outbound on the 085 radial to the VOR 15 DME. You will then need to turn 100 degrees to the right heading 185. The reason you turn one mile away is because the aircraft will still push you out to 16 DME in the turn . Likewise if you coming from another VOR towards this VOR you would start your 100 degree left turn at 17 miles Now rotate the OBS needle on your VOR instrument until it centres with a TO sign showing. Keep Adjusting the OBS to keep the needle in the centre. Each time you have done ten degrees on the OBS indication ,turn your aircraft right ten degrees and reset the needle to the centre . Repeat the procedure each time you have done 10 degrees until you get round to the required heading to fly inbound to the VOR . In this case it is 015, then turn right and fly back in to the VOR. When you are happy doing it to the right, try doing it to the left.RULE OF THUMB Your heading until intercepting should always be 100 degrees more than the radial shown at the bottom of the instrument.If the DME read out is more than 16 DME , add another couple of degrees onto it to the right say 13 degrees instead of 10 degrees next time to correct it. If the DME readout is less then turn a few degrees to the left IE 7 degrees instead of 10 degrees. This is normally caused by wind drift . On the last 10 degrees of interception you will need to set the VOR OBS to 015 ready for the inbound leg. This time keep the needle centred, then fly inbound to the VOR allowing for Drift.