DME Arc Techniques

[ppragman]

I know the so called standard technique for shooting a dme arc. Get the airplane at a tangent to the arc and every 10 degrees change heading 10 degrees, however, I heard someone tell me about using the ground speed function on the dme, and get the relative ground speed to zero, anyone heard of this? interesting...

[surreal1221]

Nope, never heard of it.

[MidlifeFlyer]

Nope, never heard of it being used. But it sorta makes technical sense. If you're not increasing or decreasing your distance from the DME, your GS =relative to the DME= would be zero. If you want to be =that= precise.

I don't really teach "turn 10, twist 10" either. I explain it since my student is bound to come across it but, even before I go go on, the student usually figures out that this s a lot more compleicated than it needs to be and that maintaining the target DME distance with small corrections (actually it is a bit like maintaining 0 GS) coupled with periodic twists of the OBS to maintain situational awareness is more than enough.

DME Arc - one of those maneuvers that, IMO, are much easier to fly than to explain.

[B767Driver]

Originally Posted by ppragman

I know the so called standard technique for shooting a dme arc. Get the airplane at a tangent to the arc and every 10 degrees change heading 10 degrees, however, I heard someone tell me about using the ground speed function on the dme, and get the relative ground speed to zero, anyone heard of this? interesting...

Yes, but not a very accurate way to fly the arc.

[BuickCFI]

i teach if you actually have a DME box (only like 5 of our 80+ planes do now) if you can get the DME to 12, and the GS to read 01 (it won't go to zero) then you will not be moving in or out on the arc.

turn 10, twist 10 is all for situational awareness

[Cessnaflyer]

Originally Posted by B767Driver

Yes, but not a very accurate way to fly the arc.

What? This seems like the most accurate way of flying the arc. If you are so close to the prescribed DME arc that there is little GS displayed then you are doing alot better then the 10 and 10 method.

[Poopsmith]

I would have to say that the "turn 10 twist 10" coupled with a DME from either a GPS or actual DME receiver provides the most situational awareness and accurate navigation. Using one technique with out the other may lead to problem, but this is just my opinion.

[surreal1221]

Originally Posted by Poopsmith

I would have to say that the "turn 10 twist 10" coupled with a DME from either a GPS or actual DME receiver provides the most situational awareness and accurate navigation. Using one technique with out the other may lead to problem, but this is just my opinion.

Yup. Couldn't agree more.

[Ophir]

The key to an Arc is workload. My first thought on the GS this is that would entice you to stare at that speed to see if it is changing. I think the key is flying a heading that makes sense. How you derive that heading has a bunch of options. The turn 10, twist 10 is how I used to teach it but I still think it is workload intense. The best way to do it is on autopilot

[Berkut]

Originally Posted by ppragman

I heard someone tell me about using the ground speed function on the dme, and get the relative ground speed to zero, anyone heard of this? interesting...

Yeah, kinda. I was taught the standard "turn 10 twist 10" technique, but also to use the ground speed indication on the DME to back it up.

[MidlifeFlyer]

Originally Posted by Poopsmith

I would have to say that the "turn 10 twist 10" coupled with a DME from either a GPS or actual DME receiver provides the most situational awareness and accurate navigation. Using one technique with out the other may lead to problem, but this is just my opinion.

So how does "turn 10 twist 10" provide more situational awareness than, say, "keep the DME within .5 miles and twist 20 or 30 or whatever number of degrees will help to keep =you= situationally aware"?

Frankly, "twist 10" always struck me as the IFR training equivalent of VFR checkpoints every 10 miles - a lot of extra work with zero extra benefit. Maybe a negative benefit since it seems to me it artificially increases the workload during one of th busiest phases of flight.

So, let's try to cubbyhole this one into a "turn 10 twist 10" framework:

http://naco.faa.gov/d-tpp/0712/05222VDTZ15.PDF

[BuickCFI]

Originally Posted by MidlifeFlyer

So how does "turn 10 twist 10" provide more situational awareness than, say, "keep the DME within .5 miles and twist 20 or 30 or whatever number of degrees will help to keep =you= situationally aware"?

Frankly, "twist 10" always struck me as the IFR training equivalent of VFR checkpoints every 10 miles - a lot of extra work with zero extra benefit. Maybe a negative benefit since it seems to me it artificially increases the workload during one of th busiest phases of flight.

So, let's try to cubbyhole this one into a "turn 10 twist 10" framework:

http://naco.faa.gov/d-tpp/0712/05222VDTZ15.PDF

yup, that is one that doesn't work very well trying to "10/10" unless you use 2 vors but that just increases the workload. personaly myself i would just put in the radials i need as i need them and use the DME to ensure i stay on the arc, i mean afterall once you are established it isn't too difficult to keep the number the same

[CamYZ125]

I've been teaching both methods for a while now. I like the 'DME only' method a bit better because you can use your nav/hsi for another use than just for the arc itself. However, I've noticed with my students that they have a bit more trouble 'staying on top of' the 'DME only' method. It will work fine until they get distracted with something, and once they really start to get off the arc things don't usually get better. The 'turn and twist' method seems to work better for most of them.

[minitour]

Originally Posted by MidlifeFlyer

Nope, never heard of it being used. But it sorta makes technical sense. If you're not increasing or decreasing your distance from the DME, your GS =relative to the DME= would be zero. If you want to be =that= precise.

I don't really teach "turn 10, twist 10" either. I explain it since my student is bound to come across it but, even before I go go on, the student usually figures out that this s a lot more compleicated than it needs to be and that maintaining the target DME distance with small corrections (actually it is a bit like maintaining 0 GS) coupled with periodic twists of the OBS to maintain situational awareness is more than enough.

DME Arc - one of those maneuvers that, IMO, are much easier to fly than to explain.

I agree. Unless I need to, I don't teach "turn 10, twist 10". I'd rather the student know where they are all the time and stay ahead of the plane. They can do that by knowing what radial they're on and where they're going. If they just know what side of the plane the navaid is going to be on prior to arcing, it's actually (for me and most students) easier than turn 10, twist 10.

...IMHO.

-mini

[B767Driver]

Originally Posted by Cessnaflyer

What? This seems like the most accurate way of flying the arc. If you are so close to the prescribed DME arc that there is little GS displayed then you are doing alot better then the 10 and 10 method.

However, you have no idea where you are on the arc. The objective is to fly the arcing course...not a speed.

What radial are you on? Where are you in respect to your lead radial or final approach course? Did you turn the proper way to get on the arc?

I believe there is a lot of benefit to updating the radial frequently in terms of situational awareness.

Flying the GS readout alone doesn't answer all of the questions I'd like to know.

[B767Driver]

Originally Posted by minitour

If they just know what side of the plane the receiver is going to be on prior to arcing,
-mini

What does this mean?

[minitour]

Originally Posted by B767Driver

What does this mean?

ugh...sorry about that. I meant "navaid". Doing too many things at once on the PDA.

-mini

[Cessnaflyer]

Originally Posted by B767Driver

However, you have no idea where you are on the arc. The objective is to fly the arcing course...not a speed.

What radial are you on? Where are you in respect to your lead radial or final approach course? Did you turn the proper way to get on the arc?

I believe there is a lot of benefit to updating the radial frequently in terms of situational awareness.

Flying the GS readout alone doesn't answer all of the questions I'd like to know.

Well I wasn't thinking of the person not updating their position on the arc. If they were only using the DME speed method and not tracking their progress along the arc then I say they deserve to hit the cumulus granite for not keeping situational awareness.

[milski]

Some nav radios have a mode where instead of the standby frequency they show the radial that you're on. I find it pretty handy for flying DME arcs since you can use the DME readout to stay on the arc and still easily cross check where on the arc you are without constantly twisting the OBS.

[CDVdriver]

I start out with a single needle indication on the HSI (G1000) and the "turn 10, twist 10".
No wind indication, no moving map, no nothing.
Once they get the hang of it I introduce the RMI function, now upon joining the arc set the HSI course needle to the inbound course and fly the arc on the RMI and DME.
Pretty much instant situational awareness and an accurate idea of what's going on.

The 10/10 method is one of the easiest to explain, not necessarily the most convenient to use in real life flying, but it is a method to reach the goal of understanding.

[butt]

The thing I hate about "turn 10 twist 10" is that it usually full deflects the needle, which I think can cause a bit of confusion at times. My method is to have the student twist the VOR so the needle is one or two dots deflected. That way they always know which radial they are on within a few degrees. Also, they can easily calculate which heading they need to hold by looking at the 3 o'clock or 9 o'clock position on the VOR dial.

On a HSI, I have them twist it so it mimics a RMI needle. I think a RMI is the easiest way to do a DME arc...

[BuickCFI]

Originally Posted by butt

The thing I hate about "turn 10 twist 10" is that it usually full deflects the needle, which I think can cause a bit of confusion at times. My method is to have the student twist the VOR so the needle is one or two dots deflected. That way they always know which radial they are on within a few degrees. Also, they can easily calculate which heading they need to hold by looking at the 3 o'clock or 9 o'clock position on the VOR dial.

On a HSI, I have them twist it so it mimics a RMI needle. I think a RMI is the easiest way to do a DME arc...

i have my students set the needle to full scale to the "inside" of the arc. then essentially we are flying from the current radial to the next 10* away, and as soon as it centers up again, turn 10 to full scale and then we know the next radial "we will fly too"

saves on some of the unnecessary workload. as they progress and understand more, if they keep doing the 10/10 thing, great. otherwise whatever.

[granlistillo]

My two cents.
Per the original question, yes that is how i do it.

Flying steam gauges, I never really stayed to the twist ten turn ten rule. I twisted only as necessary to keep the needle away from full scale deflection for SA, and looked at the groundspeed readout. If it was on the ARC and GS was less than 10 kts you were right where you need to be. My turn was based mostly on GS and yes I have seen GS "00", more than once. If you get it at zero and it starts to creep up, that is when it is time to turn a couple of degrees. If you twist ten turn ten you will fly towards the station and your gs will increase and decrease and usually you will be just inside the arc.

Arc-ing around was obviously much easier on the RMI. Just keep the needle within 5-10 degrees (depending on wind) of the wingline and you got it, it also gives 100% situational awareness. I love the G1000 with the combined HSI and RMI. You could twist your inbound or outbound course in the HSI and use the rmi needle until the hsi course comes alive, no need to twist anymore. When the head (or tail depending on course) gets with in 10 degrees they squeeze together until they line up.

[fish314]

For me, I teach the student to lead the turn on to the arc and to put the bearing pointer on the EHSI about 5 degress above the 90 degree index if he's on the arc. When the bearing pointer gets to 5 degrees below the 90 index, turn and do it again. For corrections, I teach him to keep the bearing pointer 5 degrees above the 90 index for each 1/2 mile inside the desired arc, or 10 degrees below the 90 index for each 1/2 outside the arc.

But if I didn't have an airplane with a bearing pointer, I obviously would have to teach something else. I've heard of the "turn 10, twist 10" technique, which seems like your only really good option if all you have is the OBS. If your DME receiver also has a groundspeed readout then maybe supplementing with making the groundspeed stay at zero would be good. The only down side that I see to the ground speed only is that there isn't any difference between the 20 knots TOWARDS the station display and 20 knots AWAY from the station display. So it will tell you that you aren't doing it correct, but it won't tell you which way to turn to fix it. You'd have to wait to see if the DME increased or decreased before you knew that you needed a left turn vs. a right turn.

[flyguy969]

I have not heard of this method. I did ask around and and a few CFI's have heard of it but all agreed its not the best or too acurate