DME arc

[bigjuicyspider]

My arcs tend to be sloppy, and I want to nail down a better method. The last couple days, I've been all about polishing up on my flying, and this is part of that exercise.

Let's say I'm flying towards the VOR. I turn tangent to the inbound radial at the appropriate time, say 1% of my ground speed. At this point, I change the OBS to say, plus 5, and then turn 5 degrees when the needle passes the center, and keep doing that until I come around to the final approach course. Is this the correct, or should I literally calculate a rate or turn so that I'm flying a continous arc? Or both? How far am I allowed to deviate outside the arc? A mile, half mile?

I could probably benefit from some advice and some quick rules of thumb about the best way to do this with the most precision.

[CAPFlyer]

I usually use 10 degree increments as that's what I was taught, but your method is correct for using a VOR/HSI only. The better way is to have an RMI and just keep the needle on your wingtip +/- the wind correction.

[seaniam81]

Spider, Check out this link http://www.navfltsm.addr.com/index.htm there's a nice section on how to fly a DME Arc. Works like a charm.

[pilottj]

I was taught Cap's 10 degree method too. If you have traditional DME...not GPS...use the groundspeed readout as a measuring tool. If you keep it at 0kts, you will stay on track of the required DME, and you can make your adjustments accordingly with it. The HSI presents an easier 'picture' of it, but for more of a challange, i would recommend doing it with a Heading indicator/CDI.

As for when to turn on to the Arc, I was taught to take the groundspeed, remove the last digit, divide by 2 and subtract/add(depending going to or from the VOR) the 10ths version of that value from the DME arc distance. example....going away from the VOR with GS=120kts....12/2=6...change to .6 then 15-.6=14.4...so at 14.4 start a 100 degree standard rate turn on to the Arc and you should be fine.

Cheers
TJ

[bigjuicyspider]

As for when to turn on to the Arc, I was taught to take the groundspeed, remove the last digit, divide by 2 and subtract/add(depending going to or from the VOR) the 10ths version of that value from the DME arc distance. example....going away from the VOR with GS=120kts....12/2=6...change to .6 then 15-.6=14.4...so at 14.4 start a 100 degree standard rate turn on to the Arc and you should be fine.

So .5% of your TAS, right? Yeah, I've been using that rule-of-thumb, but I think I must be slow on the turn or something, because I'm cutting into the arc more than I would like. I saw somewhere, where some people are using 1% of the TAS too. I guess that is why they call it a rule of thumb.

Embarrased to say, but the last time I flew an arc on raw data in the sim, I became so fixating on maintaining my arc that I actually missed the turn to final and flew right past the localizer. Not only that, since I wasn't tuned in to the localizer, it took me a stupidly long time to realize it. Stupid.

[pilottj]

lol yeah I was taught to use the groundspeed readout from the DME because if you have a tailwind, the groundspeed readout will reflect that difference, and you will want to start your turn a little earlier.

Say 120kts TAS with 20kt tailwind outbound from the VOR, will give you a groundspeed of 140kts...14/2=7. So for the 15 Dme arc you would turn at 14.3...vs 14.4 with 120kts groundspeed. .1 DME doesnt make much difference really, especially in slow GA planes but for faster birds, you can blow through 1nm in a hurry lol.

[Zuballos]

Spider, Check out this link http://www.navfltsm.addr.com/index.htm there's a nice section on how to fly a DME Arc. Works like a charm.

Good link. It really works smoothly.

[Swedenhausen]

Spider, Check out this link http://www.navfltsm.addr.com/index.htm there's a nice section on how to fly a DME Arc. Works like a charm.

Good link. It really works smoothly.

LNAV works really nicely, too...