DME Arc Techniques

ppragman

ppragman

FLIPY FLAPS!
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...
 
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.
 
ppragman said:
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...
Click to expand...

Yes, but not a very accurate way to fly the arc.
 
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
 
B767Driver said:
Yes, but not a very accurate way to fly the arc.
Click to expand...

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.
 
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.
 
Poopsmith said:
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.
Click to expand...

Yup. Couldn't agree more.
 
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 ;)
 
ppragman said:
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...
Click to expand...
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.
 
Poopsmith said:
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.
Click to expand...
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
 
MidlifeFlyer said:
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
Click to expand...
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
 
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.
 
MidlifeFlyer said:
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.
Click to expand...

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
 
Cessnaflyer said:
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.
Click to expand...

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 said:
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.
Click to expand...

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.
 
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.
 
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.
 
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