DME arc
- Thread starter FOD
- Start date
Easy. 60 to 1 rule. Granted, this is for higher performance aircraft, but it doesn't hurt to know. For radial to arc interceptions, you take your indicated mach (or miles per minute), and subtract 2 to get your turn radius. So, if I'm inbound at 300 knots penetration speed at 40 DME to intercept the 25 DME arc. I know that at 300 kts (5 miles per minute or .5 IMN), 5 minus 2 gives me a 3 mile lead necessary to make the turn to the arc without overshooting. So while inbound, I need to make my turn at 28 DME in order to roll out on or very near the 25 DME arc.
For a Cessna, generally 1 or 0.5 miles prior suffices. In the same aircraft, for a vector to an arc (ie not a 90 degree intercept), the same general distances will work too. For the higher performance equipment, subtracting roughly 1 mile for each 30 degrees not needed, will suffice.
For a Cessna, generally 1 or 0.5 miles prior suffices. In the same aircraft, for a vector to an arc (ie not a 90 degree intercept), the same general distances will work too. For the higher performance equipment, subtracting roughly 1 mile for each 30 degrees not needed, will suffice.
MidlifeFlyer
Well-Known Member
[ QUOTE ]
Any rule of thumb for leading a DME arc? and does anybody teach vectors to an arc? if so, how are you teaching to lead from a vector?
[/ QUOTE ]General rule of thumb for the lead is 1/2 mile for speeds up to 150 KTS, which will cover most GA instrument trainers.
The vectors I seen have usually still involved a 90 intercept, just somewhere other than an IAF. Other than that, if faced with somehting different, it would depend on the intercept angle. At worst, staying with the 90 would gat you in prettg good position for a correction. But that's just thinking out loud.
Any rule of thumb for leading a DME arc? and does anybody teach vectors to an arc? if so, how are you teaching to lead from a vector?
[/ QUOTE ]General rule of thumb for the lead is 1/2 mile for speeds up to 150 KTS, which will cover most GA instrument trainers.
The vectors I seen have usually still involved a 90 intercept, just somewhere other than an IAF. Other than that, if faced with somehting different, it would depend on the intercept angle. At worst, staying with the 90 would gat you in prettg good position for a correction. But that's just thinking out loud.
Yeah I have always just used .5 and like you guys stated it works good for slow airspeeds. I was just curious to see if there was something else out there that would work. MikeD's method seems to work, however im not that quick with mental math (yeah i know i need to invest in that book).
I have one more question that i asked before, but didnt get the answer i was looking for. When making up DME arcs for students, what is the appropriate phraseology as far as the direction of turn is concerned?
For example: Say we we're flying outbound on the 090 radial and I wanted to arc to the right to track inbound 330 radial.
Would this be an arc to the west? an arc to the south/west? something else?
I have one more question that i asked before, but didnt get the answer i was looking for. When making up DME arcs for students, what is the appropriate phraseology as far as the direction of turn is concerned?
For example: Say we we're flying outbound on the 090 radial and I wanted to arc to the right to track inbound 330 radial.
Would this be an arc to the west? an arc to the south/west? something else?
[ QUOTE ]
Yeah I have always just used .5 and like you guys stated it works good for slow airspeeds. I was just curious to see if there was something else out there that would work. MikeD's method seems to work, however im not that quick with mental math (yeah i know i need to invest in that book).
[/ QUOTE ]
My method is primarily for higher performance aircraft, but as midlife stated, below 150 knots 0.5 lead is the general rule.
[ QUOTE ]
I have one more question that i asked before, but didnt get the answer i was looking for. When making up DME arcs for students, what is the appropriate phraseology as far as the direction of turn is concerned?
For example: Say we we're flying outbound on the 090 radial and I wanted to arc to the right to track inbound 330 radial.
Would this be an arc to the west? an arc to the south/west? something else?
[/ QUOTE ]
090 to come inbound on the 330 is quite an arc distance. I would think "intercept the 20 DME arc, arc south", might be appropriate in realtion to the initial turn from the 090 radial.
Yeah I have always just used .5 and like you guys stated it works good for slow airspeeds. I was just curious to see if there was something else out there that would work. MikeD's method seems to work, however im not that quick with mental math (yeah i know i need to invest in that book).
[/ QUOTE ]
My method is primarily for higher performance aircraft, but as midlife stated, below 150 knots 0.5 lead is the general rule.
[ QUOTE ]
I have one more question that i asked before, but didnt get the answer i was looking for. When making up DME arcs for students, what is the appropriate phraseology as far as the direction of turn is concerned?
For example: Say we we're flying outbound on the 090 radial and I wanted to arc to the right to track inbound 330 radial.
Would this be an arc to the west? an arc to the south/west? something else?
[/ QUOTE ]
090 to come inbound on the 330 is quite an arc distance. I would think "intercept the 20 DME arc, arc south", might be appropriate in realtion to the initial turn from the 090 radial.
MidlifeFlyer
Well-Known Member
[ QUOTE ]
Yeah I have always just used .5 and like you guys stated it works good for slow airspeeds. I was just curious to see if there was something else out there that would work. MikeD's method seems to work, however im not that quick with mental math (yeah i know i need to invest in that book).
[/ QUOTE ]You don't need to be that good in math. It would be rare that you'd have to calculate it on the fly. Just one of the numbers you pre-calculate for the airplane, like knowing the power/configuration settings that will give you predicted performance. True, to do it "exactly" you're really talking about groundspeed, but a 30-kt tailwind will have less net effect on your calculations at 300 KTS than at 90.
[ QUOTE ]
I have one more question that i asked before, but didnt get the answer i was looking for. When making up DME arcs for students, what is the appropriate phraseology as far as the direction of turn is concerned?
For example: Say we we're flying outbound on the 090 radial and I wanted to arc to the right to track inbound 330 radial.
Would this be an arc to the west? an arc to the south/west? something else?
[/ QUOTE ]I think it's really about describing where the arc is rather than how to enter it. Might as well use ATC-standard for this, which is the same as Mike's suggestion. From the ATC Handbook para 2-5-2
==============================
b. Arcs about VOR-DME/VORTAC/TACAN/MLS NAVAIDs. State the distance in miles from the NAVAID followed by the words "mile arc," the direction from the NAVAID in terms of the eight principal points of the compass, the word "of," and the name of the NAVAID.
EXAMPLE-
"Two Zero mile arc southwest of O'Hare Runway Two Seven Left M-L-S."
==============================
Once the pilot understands and can visualize where the arc is in relation to where she is, it's really no different than a charted arc. Of course, the visualization part can cause the same consternation so many of us have with uncharted holds.
Yeah I have always just used .5 and like you guys stated it works good for slow airspeeds. I was just curious to see if there was something else out there that would work. MikeD's method seems to work, however im not that quick with mental math (yeah i know i need to invest in that book).
[/ QUOTE ]You don't need to be that good in math. It would be rare that you'd have to calculate it on the fly. Just one of the numbers you pre-calculate for the airplane, like knowing the power/configuration settings that will give you predicted performance. True, to do it "exactly" you're really talking about groundspeed, but a 30-kt tailwind will have less net effect on your calculations at 300 KTS than at 90.
[ QUOTE ]
I have one more question that i asked before, but didnt get the answer i was looking for. When making up DME arcs for students, what is the appropriate phraseology as far as the direction of turn is concerned?
For example: Say we we're flying outbound on the 090 radial and I wanted to arc to the right to track inbound 330 radial.
Would this be an arc to the west? an arc to the south/west? something else?
[/ QUOTE ]I think it's really about describing where the arc is rather than how to enter it. Might as well use ATC-standard for this, which is the same as Mike's suggestion. From the ATC Handbook para 2-5-2
==============================
b. Arcs about VOR-DME/VORTAC/TACAN/MLS NAVAIDs. State the distance in miles from the NAVAID followed by the words "mile arc," the direction from the NAVAID in terms of the eight principal points of the compass, the word "of," and the name of the NAVAID.
EXAMPLE-
"Two Zero mile arc southwest of O'Hare Runway Two Seven Left M-L-S."
==============================
Once the pilot understands and can visualize where the arc is in relation to where she is, it's really no different than a charted arc. Of course, the visualization part can cause the same consternation so many of us have with uncharted holds.
[ QUOTE ]
You don't need to be that good in math. It would be rare that you'd have to calculate it on the fly. Just one of the numbers you pre-calculate for the airplane, like knowing the power/configuration settings that will give you predicted performance. True, to do it "exactly" you're really talking about groundspeed, but a 30-kt tailwind will have less net effect on your calculations at 300 KTS than at 90.
[/ QUOTE ]
Agreed. Once the basic calculations are known, they're simply applied wherever necessary. For example, the 3 mile turn radius (or 0.5 for lighter aircraft), can be applied inflight, or in preflight planning/study of the plate. Same with arc to radial calculations. For example, say you want to fly the 20 DME arc and turn inbound on the 090 degree radial from the south. 60 to 1 rule says arc distance divided into 60, multiplied by the turn radius of the aircraft (for my case, again, 3), equals the lead radial. So 20 divided into 60 equals 3. 3 times 3 equals 9, or 9 radials of lead on a 20 DME arc. So crossing the 099 (or 100 radial rounded up), start the left turn to intercept the 090 radial inbound. Again, this formula can conceivably be applied to a light aircraft, but isn't necessarily very practical, since most of the calculations already come out to the CDI coming alive anyway, whereas for faster aircraft, the idea is a lead radial, since when the CDI comes alive, you're already too late. But again, as Midlife said, once the basic calculations are known, the need for the mental math while airborne isn't really needed.
[ QUOTE ]
I think it's really about describing where the arc is rather than how to enter it. Might as well use ATC-standard for this, which is the same as Mike's suggestion. From the ATC Handbook para 2-5-2
==============================
b. Arcs about VOR-DME/VORTAC/TACAN/MLS NAVAIDs. State the distance in miles from the NAVAID followed by the words "mile arc," the direction from the NAVAID in terms of the eight principal points of the compass, the word "of," and the name of the NAVAID.
EXAMPLE-
"Two Zero mile arc southwest of O'Hare Runway Two Seven Left M-L-S."
==============================
Once the pilot understands and can visualize where the arc is in relation to where she is, it's really no different than a charted arc. Of course, the visualization part can cause the same consternation so many of us have with uncharted holds.
[/ QUOTE ]
That's good to read. I was taking a guess on my answer. I'd forgotten about the 8 cardinal points for reference vice 4 cardinal points that I was thinking. Re-learn something every day!
You don't need to be that good in math. It would be rare that you'd have to calculate it on the fly. Just one of the numbers you pre-calculate for the airplane, like knowing the power/configuration settings that will give you predicted performance. True, to do it "exactly" you're really talking about groundspeed, but a 30-kt tailwind will have less net effect on your calculations at 300 KTS than at 90.
[/ QUOTE ]
Agreed. Once the basic calculations are known, they're simply applied wherever necessary. For example, the 3 mile turn radius (or 0.5 for lighter aircraft), can be applied inflight, or in preflight planning/study of the plate. Same with arc to radial calculations. For example, say you want to fly the 20 DME arc and turn inbound on the 090 degree radial from the south. 60 to 1 rule says arc distance divided into 60, multiplied by the turn radius of the aircraft (for my case, again, 3), equals the lead radial. So 20 divided into 60 equals 3. 3 times 3 equals 9, or 9 radials of lead on a 20 DME arc. So crossing the 099 (or 100 radial rounded up), start the left turn to intercept the 090 radial inbound. Again, this formula can conceivably be applied to a light aircraft, but isn't necessarily very practical, since most of the calculations already come out to the CDI coming alive anyway, whereas for faster aircraft, the idea is a lead radial, since when the CDI comes alive, you're already too late. But again, as Midlife said, once the basic calculations are known, the need for the mental math while airborne isn't really needed.
[ QUOTE ]
I think it's really about describing where the arc is rather than how to enter it. Might as well use ATC-standard for this, which is the same as Mike's suggestion. From the ATC Handbook para 2-5-2
==============================
b. Arcs about VOR-DME/VORTAC/TACAN/MLS NAVAIDs. State the distance in miles from the NAVAID followed by the words "mile arc," the direction from the NAVAID in terms of the eight principal points of the compass, the word "of," and the name of the NAVAID.
EXAMPLE-
"Two Zero mile arc southwest of O'Hare Runway Two Seven Left M-L-S."
==============================
Once the pilot understands and can visualize where the arc is in relation to where she is, it's really no different than a charted arc. Of course, the visualization part can cause the same consternation so many of us have with uncharted holds.
[/ QUOTE ]
That's good to read. I was taking a guess on my answer. I'd forgotten about the 8 cardinal points for reference vice 4 cardinal points that I was thinking. Re-learn something every day!
averyrm
Well-Known Member
Also, when teaching the arc: I learned the Turn 10 twist 10 stuff during my initial training but was tought by a DE a much better way. If the number starts getting bigger, turn towards the navaid, if it gets smaller, hold heading or turn slightly away. Much easier for everyone.
[ QUOTE ]
Also, when teaching the arc: I learned the Turn 10 twist 10 stuff during my initial training but was tought by a DE a much better way. If the number starts getting bigger, turn towards the navaid, if it gets smaller, hold heading or turn slightly away. Much easier for everyone.
[/ QUOTE ]
Hadn't heard that one, but if it works, all the better. There's iterations of the 10 for 10, 20 for 20, etc, ie- many techniques that get you to the same end. Pick the one that is the easiest to understand, and keeps your workload down. And it seems you have.
Also, when teaching the arc: I learned the Turn 10 twist 10 stuff during my initial training but was tought by a DE a much better way. If the number starts getting bigger, turn towards the navaid, if it gets smaller, hold heading or turn slightly away. Much easier for everyone.
[/ QUOTE ]
Hadn't heard that one, but if it works, all the better. There's iterations of the 10 for 10, 20 for 20, etc, ie- many techniques that get you to the same end. Pick the one that is the easiest to understand, and keeps your workload down. And it seems you have.
MidlifeFlyer
Well-Known Member
[ QUOTE ]
Also, when teaching the arc: I learned the Turn 10 twist 10 stuff during my initial training but was tought by a DE a much better way. If the number starts getting bigger, turn towards the navaid, if it gets smaller, hold heading or turn slightly away. Much easier for everyone.
[/ QUOTE ]Makes sense. Think about it. You're trying to maintain, say 23 on the DME. Why blindly make 10° turns toward the VOR based on an artificial counting of degrees along the arc when the DME tells you exactly how far away you are. I never really understood the "Turn 10" part of the process. It might be that the DME are is easier to fly than to explain, so the explanations can get a bit cumbersome.
I think the "Twist 10" makes a lot of sense for situational awareness of your position =along= the arc rather than your distance from the VOR. Even then, there's no reason it =has to be= 10°. I like the first one to be 10° so I know whether I've turned the wrong way on the entry sooner rather than later
, but other than that, situational awareness is really the name of the game.
Check out the DME arc for the VOR/DME 15 approach into Martin State. Imagine the increased workload in adding "Turn 10, Twist 10" to the other twists you =have= to do along the arc.
http://naco.faa.gov/d-tpp/0506/05222VDTZ15.PDF
Also, when teaching the arc: I learned the Turn 10 twist 10 stuff during my initial training but was tought by a DE a much better way. If the number starts getting bigger, turn towards the navaid, if it gets smaller, hold heading or turn slightly away. Much easier for everyone.
[/ QUOTE ]Makes sense. Think about it. You're trying to maintain, say 23 on the DME. Why blindly make 10° turns toward the VOR based on an artificial counting of degrees along the arc when the DME tells you exactly how far away you are. I never really understood the "Turn 10" part of the process. It might be that the DME are is easier to fly than to explain, so the explanations can get a bit cumbersome.
I think the "Twist 10" makes a lot of sense for situational awareness of your position =along= the arc rather than your distance from the VOR. Even then, there's no reason it =has to be= 10°. I like the first one to be 10° so I know whether I've turned the wrong way on the entry sooner rather than later
Check out the DME arc for the VOR/DME 15 approach into Martin State. Imagine the increased workload in adding "Turn 10, Twist 10" to the other twists you =have= to do along the arc.
http://naco.faa.gov/d-tpp/0506/05222VDTZ15.PDF
mtsu_av8er
Well-Known Member
[ QUOTE ]
Check out the DME arc for the VOR/DME 15 approach into Martin State. Imagine the increased workload in adding "Turn 10, Twist 10" to the other twists you =have= to do along the arc.
http://naco.faa.gov/d-tpp/0506/05222VDTZ15.PDF
[/ QUOTE ]
I love that approach . . .
Check out the DME arc for the VOR/DME 15 approach into Martin State. Imagine the increased workload in adding "Turn 10, Twist 10" to the other twists you =have= to do along the arc.
http://naco.faa.gov/d-tpp/0506/05222VDTZ15.PDF
[/ QUOTE ]
I love that approach . . .
BrianNC
Well-Known Member
[ QUOTE ]
Some people teach constant bank angle in order to maintain the arc, somewhat a more precise variation of the "bigger/smaller" principle. Again, if it works, cool.
[/ QUOTE ]
Interesting. Never heard that one. You mean actually keeping a bank and more or less exactly flying the arc?
Some people teach constant bank angle in order to maintain the arc, somewhat a more precise variation of the "bigger/smaller" principle. Again, if it works, cool.
[/ QUOTE ]
Interesting. Never heard that one. You mean actually keeping a bank and more or less exactly flying the arc?
[ QUOTE ]
[ QUOTE ]
Some people teach constant bank angle in order to maintain the arc, somewhat a more precise variation of the "bigger/smaller" principle. Again, if it works, cool.
[/ QUOTE ]
Interesting. Never heard that one. You mean actually keeping a bank and more or less exactly flying the arc?
[/ QUOTE ]
Correct. It can be done. What makes it easy to do is having an HSI that also has an RMI function, that is, a bearing pointer that constantly points to the VOR. Some HSIs have them, some don't (ours do). With that, all you have to do crosscheck your DME, and if outside the arc, keep the bearing pointer above the 90 degree point (off the wing), if inside the arc, keep the pointer below the 90 degree point to correct. Once on the arc, keep the pointer at the 90 degree point and fly the constant bank turn, and you'll stay on. The other good thing about the RMI pointer is that you have instant SA on where you are at any given time on the arc without having to turn/twist to follow progress, and have a good visual depiction of when the Lead Radial is coming up.
[ QUOTE ]
Some people teach constant bank angle in order to maintain the arc, somewhat a more precise variation of the "bigger/smaller" principle. Again, if it works, cool.
[/ QUOTE ]
Interesting. Never heard that one. You mean actually keeping a bank and more or less exactly flying the arc?
[/ QUOTE ]
Correct. It can be done. What makes it easy to do is having an HSI that also has an RMI function, that is, a bearing pointer that constantly points to the VOR. Some HSIs have them, some don't (ours do). With that, all you have to do crosscheck your DME, and if outside the arc, keep the bearing pointer above the 90 degree point (off the wing), if inside the arc, keep the pointer below the 90 degree point to correct. Once on the arc, keep the pointer at the 90 degree point and fly the constant bank turn, and you'll stay on. The other good thing about the RMI pointer is that you have instant SA on where you are at any given time on the arc without having to turn/twist to follow progress, and have a good visual depiction of when the Lead Radial is coming up.
BrianNC
Well-Known Member
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Some people teach constant bank angle in order to maintain the arc, somewhat a more precise variation of the "bigger/smaller" principle. Again, if it works, cool.
[/ QUOTE ]
Interesting. Never heard that one. You mean actually keeping a bank and more or less exactly flying the arc?
[/ QUOTE ]
Correct. It can be done. What makes it easy to do is having an HSI that also has an RMI function, that is, a bearing pointer that constantly points to the VOR. Some HSIs have them, some don't (ours do). With that, all you have to do crosscheck your DME, and if outside the arc, keep the bearing pointer above the 90 degree point (off the wing), if inside the arc, keep the pointer below the 90 degree point to correct. Once on the arc, keep the pointer at the 90 degree point and fly the constant bank turn, and you'll stay on. The other good thing about the RMI pointer is that you have instant SA on where you are at any given time on the arc without having to turn/twist to follow progress, and have a good visual depiction of when the Lead Radial is coming up.
[/ QUOTE ]
Pretty neat.
[ QUOTE ]
[ QUOTE ]
Some people teach constant bank angle in order to maintain the arc, somewhat a more precise variation of the "bigger/smaller" principle. Again, if it works, cool.
[/ QUOTE ]
Interesting. Never heard that one. You mean actually keeping a bank and more or less exactly flying the arc?
[/ QUOTE ]
Correct. It can be done. What makes it easy to do is having an HSI that also has an RMI function, that is, a bearing pointer that constantly points to the VOR. Some HSIs have them, some don't (ours do). With that, all you have to do crosscheck your DME, and if outside the arc, keep the bearing pointer above the 90 degree point (off the wing), if inside the arc, keep the pointer below the 90 degree point to correct. Once on the arc, keep the pointer at the 90 degree point and fly the constant bank turn, and you'll stay on. The other good thing about the RMI pointer is that you have instant SA on where you are at any given time on the arc without having to turn/twist to follow progress, and have a good visual depiction of when the Lead Radial is coming up.
[/ QUOTE ]
Pretty neat.
kellwolf
Piece of Trash
Flew a sim session with an RMI the other day, and it was the first time I'd flown with one. Dude, it makes DME arcs AND NDB approaches a snap. Also, the KLN 94 (and I think the Garmin 430) will make flying a DME arc easier if you load it into the approach. Technically, you can only use the GPS for DME distance info and not course guidance, but I don't see how that's any less legal than a "constant bank angle" technique.
[ QUOTE ]
Flew a sim session with an RMI the other day, and it was the first time I'd flown with one. Dude, it makes DME arcs AND NDB approaches a snap.
[/ QUOTE ]
RMIs haven't been common in aircraft for a long time now, which I can't understand why, since it's such a useful instrument. But panel's are only so big, and unfortunately, the RMI has been outmoded as a stand-alone instrument. Unless they're combined with an HSI, you'll see few aircraft carrying them these days it seems.
Flew a sim session with an RMI the other day, and it was the first time I'd flown with one. Dude, it makes DME arcs AND NDB approaches a snap.
[/ QUOTE ]
RMIs haven't been common in aircraft for a long time now, which I can't understand why, since it's such a useful instrument. But panel's are only so big, and unfortunately, the RMI has been outmoded as a stand-alone instrument. Unless they're combined with an HSI, you'll see few aircraft carrying them these days it seems.
BrettInLJ
Well-Known Member
[ QUOTE ]
[ QUOTE ]
Flew a sim session with an RMI the other day, and it was the first time I'd flown with one. Dude, it makes DME arcs AND NDB approaches a snap.
[/ QUOTE ]
RMIs haven't been common in aircraft for a long time now, which I can't understand why, since it's such a useful instrument. But panel's are only so big, and unfortunately, the RMI has been outmoded as a stand-alone instrument. Unless they're combined with an HSI, you'll see few aircraft carrying them these days it seems.
[/ QUOTE ]
I just wish I could have an HSI!
[ QUOTE ]
Flew a sim session with an RMI the other day, and it was the first time I'd flown with one. Dude, it makes DME arcs AND NDB approaches a snap.
[/ QUOTE ]
RMIs haven't been common in aircraft for a long time now, which I can't understand why, since it's such a useful instrument. But panel's are only so big, and unfortunately, the RMI has been outmoded as a stand-alone instrument. Unless they're combined with an HSI, you'll see few aircraft carrying them these days it seems.
[/ QUOTE ]
I just wish I could have an HSI!
MidlifeFlyer
Well-Known Member
[ QUOTE ]
I just wish I could have an HSI!
[/ QUOTE ]They show up in some unexpected places. I was going up for some local night currency work so I chose the cheapest 172N in the school. I hadn't flown that particular N-Number in a while. I opened the door and did a double-take when I found a Garmin 430 with an HSI.
I just wish I could have an HSI!
[/ QUOTE ]They show up in some unexpected places. I was going up for some local night currency work so I chose the cheapest 172N in the school. I hadn't flown that particular N-Number in a while. I opened the door and did a double-take when I found a Garmin 430 with an HSI.