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wipeout01

Help with VOR/DME arcs without RMI. Do we have any tutorial or how to?

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Hi,
As far as I know the Bonanza A36 from Carenado don't have a RMI - Route Magnetic Indicator in the cockpit... and many times when I am departing from an Airport, I need to tackle a VOR/DME arc.
Many of the tutorials I find to proceed with a VOR/DME arc, requiere a RMI instrument, and I think I don't have any inside the Bonanza A36, so I am wondering if do we have any videotutorial or tutorial available showing me how to follow a VOR/DME arc without RMI?
Cheers

 

bonanza36cockpit_zpspzkzov4y.jpg

 

I don't see any RMI ?

 

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Well you need DME for sure....  I can't recall if there is DME on the default carenado bonanza?

 

Basically you center the CDI needle if you're traveling outbound on some radial, and about 1 mile before your arc (so at 14 miles if the arc is a 15 dme arc), you turn 90 degrees left or right (depending on the direction of the arc) off your current heading, then you twist the OBS knob 10 degrees..  the twist part just helps you understand where you are on the arc....  once the CDI centers again you turn 10 degrees, and twist the OBS knob 10 deg again.... and so on.

 

edit:  if you don't have DME you could use Direct To a VORTAC and see the distance readout on that.  It's actually easier with DME though because the DME gives you trends to see if you're going going away or getting closer (sort of) to the station as you arc.

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Hi... no I have a friend that is pilot and told me that there is a method to follow an arc without RMI. I'm very sure about that.

VORTAC is for military purposes, I'll use a normal VOR/DME...

I need to follow an arc with the Bonanza so I don't have RMI and I will follow normal VOR arcs ???

Any idea about how to do this step by step?

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Lol

 

Sir I'm telling you you need DME, I didn't mention anything about RMI. The way I described to you is for use without an RMI... It's for use with your HSI (the center compass instrument in your bonanza)

 

VORTAC isn't just for military , it is a VOR/DME combined with tacan

 

PS I'm a pilot and air traffic controller

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I am assuming, since I don't see a dedicated DME receiver in that airplane, that either of those GNS 530's will display distance numerically to or from a VOR/DME or VORTAC.

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Hi ryanbatcund

 

Read fast and confused DME with RMI. My fault, absolutely, I've read your message wrong (fast I'd say), yes, you said DME and not RMI. Sorry, yes I know what a DME is of course.

 

By the way, I am not flying an airplane right now, so please, just call me buddy, and not sir. ;)

 

Let's go back to the VOR/DME arc.

Ok. I have my HSI.. and the CDI to select radials... ok

 

Let's see if I understood this. So as you said (for a departure VOR/DME arc):

 

- If I had a VOR/DME arc of 15 nm...

- 1 mile before (14 nm) turn 90 degrees left or right according the direction of the arc.

- Then I twist the OBS knob 10 degrees...

- CDI arrow consequently will be broken...  and it will start to align...

- One again I twist the OBS knob 10 degrees... the CDI line will be broken and will start to align again (we are inside the arc and we are maintaining the arc)... we repeat this process all the time to maintain the arc...

- As long I am twisting the knob... I also control my actual heading...

 

BUT...

 

I don't know very well how to get out from the ARC?

 

I have a radial of course that will show a straight line toward an airway... so... I am bit confused about how would I know I am 1 mile before... from the radial that gets me out from the arc? I know what a DME is and I know how to use it... but I am a bit confused about how may I depart from the arc...

 

mmmmmm

 

I just try to picture the instruments on my mind... so I'm twisting the knob... and let's imagine I have to depart from the arc in the radial 325...

How do I know I am one mile before of that radial, to start the 90 degrees turn... before reaching the 325 radial, to get align with it?

 

 

PS (jalbino59) Bonanza A36 don't have a dedicated DME, but it has a nearest page, where you can control all the distances from all the nearest VOR... so it is like if it was having a lot of DMEs equipment controlling all the closer VOR.

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Are you trying to fly a particular procedure? If so which airport and which procedure?  

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How do I know I am one mile before of that radial, to start the 90 degrees turn... before reaching the 325 radial, to get align with it?

The simplest way that I know of is to tune your nav radio to the desired VOR, set the radial you want and watch the needle - as it approaches center start your turn to course - adjust as necessary. Obviously WHEN you start your turn will depend on your groundspeed and wind but you should only need small corrections.

 

 

Vic

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I just try to picture the instruments on my mind... so I'm twisting the knob... and let's imagine I have to depart from the arc in the radial 325...

How do I know I am one mile before of that radial, to start the 90 degrees turn... before reaching the 325 radial, to get align with it?

 

 

 

Without DME (Distance Measuring Equipment), OR a GPS, you wouldn't know.  

 

Basic VOR navigation tutorial video

 

Excellent youtube tutorial on DME ARCs

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Hi,

As far as I know the Bonanza A36 from Carenado don't have a RMI - Route Magnetic Indicator in the cockpit... and many times when I am departing from an Airport, I need to tackle a VOR/DME arc.

Many of the tutorials I find to proceed with a VOR/DME arc, requiere a RMI instrument, and I think I don't have any inside the Bonanza A36, so I am wondering if do we have any videotutorial or tutorial available showing me how to follow a VOR/DME arc without RMI?

Cheers

 

 

I don't see any RMI ?

Dunno... Would this help?

 

I only used the GTN750 For reference.

 

 

Chas

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LOL...

 

You need DME to fly a DME Arc. The final course is your goal course. You set the radial to your initial waypoint intercept, and increase or decrease your course in 10* increments until reaching your desired final course. You need to stay within the required DME for this to work as well. 

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There's going to be a certain amount of imprecision when just using a VOR and DME (subbing GPS distance measuring is also completely legal). Don't expect yourself to fly some perfect half oval. On the checkride the DPE is looking for you to stay within 1 mile of the given distance.


Without DME (Distance Measuring Equipment), OR a GPS, you wouldn't know.  

 

Basic VOR navigation tutorial video

 

Excellent youtube tutorial on DME ARCs

 

He's asking about being a certain distance from arriving at a specific radial, not the DME fix from the station itself.

The simple answer is that depending on how far from the station he is, once the needle comes alive, the offset of it will give him the distance he is currently from the radial that he has set with the OBS.

 

The dots represents 200ft per nautical mile from the station. So in his case, on a 15nm DME arc (if he's actually 15nm from the station), each dot represents about half a nautical mile from the center of the given radial. So if he wants to turn onto the 325 radial off the arc (as per the example in his question) then starting the turn at a 2 dot deflection will give him a mile of lead time.

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I don't know very well how to get out from the ARC?

 

I have a radial of course that will show a straight line toward an airway... so... I am bit confused about how would I know I am 1 mile before... from the radial that gets me out from the arc? I know what a DME is and I know how to use it... but I am a bit confused about how may I depart from the arc...

 

Let see if I can help you with this:

 

Let's imagine you need to leave the arc via de 350° radial.  And that you are flying the Bonanza A36.

 

So, what you have to do is to start turning off the arc when you are, say 5 radials before de 350 radial.  It would be the 345 or 355 radial.. depending on the side of the turns.  

 

So. select with the OBS the 345 or 355 radial (that is 5 radials before the desired radial of your aiway), when the CDI centers, it is time to turn off the arc.  This applies to small and slow aircraft.  For faster planes, 10 radials would do the job.  I know there is a math calculation to know exactley how many radials you have to anticipate to leave an arc... but 10 radials in a king (what I fly on FS) is enough

 

I hope to be clear and have answered your question.

 

PD.  When you join the DME arc, is not necessarly 1nm before. Let's put an example of a 10 DME arc.  

It is the 1% of your Ground Speed what tells the distance you have to anticipate..  

 

**Let's say that you fly a plane that climbs a 100 GS...1% of 100 knots= 1 nm.. this is.  At 9nm you have to start to turn right or left 90°

**but... if your plane flies at 180 knots... 1% of 180 kt = 1.8 nm.  In this case, at 8.2nm you have to start to turn right or left 90°

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Hi NickATC thanks for the message.

First thing, I tell everyone what I know how to do.

I know how to tune a VOR frequency in the NAV radio, I know how to select a radial with the OBS, I know what is the CDI and what means when the arrow is completed or broken, I know what is FROM / TO indication in the HSI when selecting a VOR radial.

I know all this, so we can avoid videos to teach me about how to fly with a VOR, I already know that.

I need to focus in the arc.

My problem actually is about holding the arch. I cannot hold the arc, instead doing the whole arch, I do a kind of spiral and I am getting away from the arch.

I am posting a detailed view of the ARCH I want to follow, Formentera, Spain.

 

arcofuerteventura_zps3yiklps6.jpg

 

What you see there are two marks, indicating the entrance to the two archs you find in that departure.

I want to follow de MAPED1R departure, so I go for the first arch.

 

What I do is...

Before I take off, I tune the Fuerteventura VOR in my NAV1 radio

I see in the chart, I must start the arch in the radial 217... so I select the radial 217 with the OBS knob to know when I am crossing it.

The CDI line, broke...

I take off with the runway heading, 190

When I am 5.0 miles away from the Fuerteventura VOR, I turn right 90º... so I put my heading 280...

Then I want until I intercept the radial 217 of the Fuerteventura VOR

At that time, the CDI line centers and it's complete.

I check out my DME, and bingo, I am exactly at 7.0 nautical miles.

The arch must be hold in 7.0 nautical miles... so at this point, everything is fine (I guess?)

My problem start right now.

I want to maintain all the arch at 7.0 nm... and my problem is I cannot

I start the arch at 7.0 nm... but at the end of the arch... I am at 12 nm !!!

So I cannot hold the arch... I am departing, and departing, and departing, so I am not doing an arch... I am doing an spiral...

 

What do I do to maintain the arch?

Okay... when I am intercepting the radial 217... my CDI line centers and it is completed. I see the DME and it is 7.0 nm

The arch must be maintained at 7.0 nm all the arc.

Okay...

At that time...

I move the OBS knob in 10 degrees... and the HDG in 10 degrees...

Then... I wait the CDI line centers... and again I do the same... I move the OBS knob in 10 degrees... and the HDG in 10 degrees....

Then... I wait the CDI line centers... and again I do the same... and so on...

This is what I do to hold the arch...

 

However I start the arch in 7.0 nm... and I end the arch at 12 nm !!!

So I am doing something wrong...

 

I think that the only way you can see what I am doing wrong, is taking a look about how I am flying the arch... and...

I DID A VIDEO ;)

 

Here it is:

 

In the video you can see the arch, and I explain step by step what I do exactly...

If you take a look to the video, you would see my error.

 

I really need help with this... because I don't know... I am unable to maintain the same distance in the whole arch...

 

Please could you take a look to the video and tell me what am I doing wrong and how may I correct this?

Chers

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You are way overcomplicating it. 

You don't have to keep resetting the OBS and you will not have course guidance with the CDI while flying the arc with just a regular VOR. When flying an arch, you know your starting position. You have a general mental picture of the arch. That's all you need except your DME fix. 

When you start on the arch, watch your DME (via GPS with the navaid set if you have no DME). If you start to go from 7 to 7.5, turn into the arc more. If you start going from 7 to 6.5, shallow out your bank some. Make your changes small so it doesn't get away from you. You are literally picturing and flying the arc based on how quickly you move from or away from the 7nm fix. 

 

The only guidance you have or need to maintain the arc is your range from the navaid. That's it. Because of this you will naturally have to correct a lot and may snake your way along the arc. That's ok and totally normal. The point is to remain within 1nm of the centerline of the arc. Not be perfect.

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I did what you said, and don't work.

Knowing your distance to the VOR station with the DME is not enough. You must also be perpendicular to the path... if not, you wouldn't get an arch, you would get a Mexican taco. Really, a Mexican taco.

You would get other geometrical shape and not an arch.

OBS and HDG are compulsory as far as I know.

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I did what you said, and don't work.

Knowing your distance to the VOR station with the DME is not enough. You must also be perpendicular to the path... if not, you wouldn't get an arch, you would get a Mexican taco. Really, a Mexican taco.

You would get other geometrical shape and not an arch.

OBS and HDG are compulsory as far as I know.

 

I'm an IFR-rated pilot and I honestly don't see what the confusion is. What do you mean it "doesn't work?" You can't turn left or right to correct your arc when the DME drifts from 7nm? What other directional input are you expecting?

 

I'll explain it again:

 

Off the entry radial to the arc that's defined on the chart, turn 90 degrees off that entry radial once you reach your given DME fix for the arc (start your turn earlier so you roll out right at 7nm, how early is totally dependent on speed). That's how you get perpendicular to the radials for the arc.

 

You will almost certainly come in too shallow or too sharply. Correct as needed. If you are too sharp into the arc (say you see 6.2nm after rollout), continue flying 90 degrees off the entry radial until you get back to 7nm. If you are too wide, fly 110 degrees or so off the entry radial until you get back to 7nm. Now that you are on the arc manage a slight bank to keep your DME around 7nm. If it starts to climb slightly, add a few more degrees of bank. If it starts to drop slightly, shallow out. There's no exact science needed here.

 

If you want to get fancier, use the 10/10 method. After turning 90 degrees off the entry radial, twist to the next radial that's 10 degrees higher. So a 260 entry radial would mean the next radial you set is 270 and turn 10 degrees from your present heading. You will then intersect the next radial at 90 degrees. Once you do, dial in the 280 radial, turn 10 degrees, and repeat. So on and so forth.

 

If you could visualize how that works, you are not flying a perfect arc. You are really making steps along the arc but within a legal distance. Same thing if you just watch the DME and correct without the 10/10 method. You will not fly it perfectly nor are you expected to. The tolerances are 1nm from the center of the arc. So between 6-8nm in your example is legal.

 

You seem to be expecting to fly it at 7nm, perfectly, with a beautiful continuous bank that forms a perfect arc. That ain't gonna happen with just a single VOR. Arcs require continual correction and they absolutely can be flown with just a VOR and DME.

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Great input Bonchie!

 

Cheers to all who are learning DME Arcs.

 

Chas

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Agreed - great explanation Bonchie.

 

@wipeout1 - in a perfect world with no wind or external forces acting on the a/c you could probably set up the proper turn rate that would maintain the 7nm DME arc with no additional input.

 

Add in wind direction, turbulence, controller jitter etc - it is not going to happen. I think, in over 40 years of flying I can only recall once when I traversed the DME arc as if I was riding a wave - pure luck on my part.

 

So, unless I misunderstand your comment - "it don't work" applies to your current ability to fly the A/C rather than have it fly you.

 

It's a great thing to learn and it takes practice, practice, practice.

 

Vic

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Bonchie nailed it.  I'm a navigation instructor, maybe my tips can give you another look at the same topic:

 

I always teach the DME arc by following 3 single steps.

 

1.  Anticipate

2.  What's the first radial to 'cut'

3.  Heading to attack the first radial.

 

I'll explain one by one.

 

1. Anticipate.  I explained it in my post, but in your video you didnt' apply it.  You turned 5nm from VOR, but your speed was 120 kts.  That's why when you flew heading 280, you were just 6nm from the VOR... you turned too early.  

 

I'll explain again:  Anticipate 1% of your GS.  As you were taking off we will assume that your KIAS and GS are the same.  They are not... but they are very close.

 

Your climb speed was 120 kts ... so 1% would be 1.2.  This, converted to nm, would be to anticipate 1.2 nm before the arc....   sooooooo:

 

 7 dme

-1.2     

  5.8 nm  This is your first number.  Fly runway heading, and when 5.8nm from VOR, turn right (for the arc you want)... to what heading??'   that's step 3... hold your horses  :wink:

 

2.  What's the first radial to 'cut'?  This radial is not stated on the charts.  I've never seen a chart that states the first radial to 'cut'... so you have to infer it.  Is it difficult??  no... 

 

You said you were flying runway heading of 190... so, you would be leaving via the 190 radial... not exact, but can give you an idea.  So... if you were leaving via the 190° radial, what is your next radial??  as the arc you want to do is clockwise, the radials will increase.  Your next radial will be 200°.  And that is your second number**.  You have to cut the 200 radial... and the heading???

 

3.  Heading.  THIS IS THE REASON YOU ARE EVERYTIME FARTHER FROM THE VOR, PAY ATTENTION HERE!!!

As explained before, you have to attack every radial selected with 90°.  So, as your arc is clockwise, you have to add 90° to the radial that is selected... no the current heading you are flying!

 

Your error was that you selected the radial 217°, but you flew heading 280°.   Error!!!! :excl:    217°+90°= 307°... you were making a big error of almost 30°... that's too much!

 

Back to my explanation:  as the first radial to attack is 200° (see step 2), the first heading is:  200°+90°= 290°... and that is your third number.  Fly heading 290°

 

So... let's put all together, like if we were doing the briefing of this chart:

 

Take off, fly runway heading of 190°, when 5.8nm from VOR, turn right heading 290° until you 'cut' the 200° radial.**

Once you cut the 200° radial, you are doing this perfectly.... add 10° to the radials, and 10° to the heading:  next would be 210° radial and 300° heading... and so on.  Double check the heading adding 90 to the radial selected.   Try this with wind calm until you can make the arc perfectly... until you master the technique.

 

But not always you have wind calm... so bonchie explained this better that I can do, so if your distance is increasing, put your nose where the VOR is:  do not add 10° of heading, but 15°... or 20°.  No rule here, just an educated guess.  This depends on the wind component and intensity.

If your distance is decreasing, do not add 10° to the heading, but 5°.  No rule here, just an educated gues... blah blah blah.  you know what I'm talking here.

 

Try my numbers... and fly the same procedure.  Record a new video, and let us know your results.

 

How cow!!  a very long explanation... sorry for that!   :smile:

 

 

** The first radial can also be 210° + 90° = 300° heading to attack the 210° radial.

In case you need, PM me and we can have a skype session and I can see what you are doing and correct you... I'm sure this works best than reading, practicing, making mistakes, post, wait, reading... etc. LOL

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Don't apologize for a long explanation Nick! I'll bet between you and Bonchie he gets it worked out.

 

Another great explanation!

 

Thank you both.

 

Vic

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Just FYI, the 217° radial is neither the first radial to cut nor is where the 7dme arc begins... it is the radial in which the 56 dme arc begins... As I stated in my previous post, the first radial to cut is not described in the chart.

 

WTH!!   56dme arc!!???   :fool:  :nea:  :mad: 

 

'Tower, I request to fly direct to... '   :dance:  LOL

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Sorry for my delayed reply. I've been away almost 20 days, so I am coming back and reading the forum right now.

I am flying archs right now... so I will try to reply everyone.

 

I'm an IFR-rated pilot and I honestly don't see what the confusion is. What do you mean it "doesn't work?" You can't turn left or right to correct your arc when the DME drifts from 7nm? What other directional input are you expecting?

 

I am expecting a directional input that allow me to present an arch so beautiful in its path... that can win a drawing contest. I imagine my airplane is a pencil, and I am expecting to win this drawing contest even if I have strong wind. Sorry I be so contundent in my reply, but that is indeed my problem. I think I know how to fly an arch... however my problem is this exactly.

 

What worry me about flying archs is that I feel I am a bad pilot if I fly a legal arch, inside its limits, but not beautiful, squiggly for example. If I present a squiggly arch I think I am not doing the things well, even if the FAA tells me I was flying inside the rules.

 

How an squiggly path that remember an arch can be considered truly an arch?

Those things are the one that confuse me.

 

You will almost certainly come in too shallow or too sharply. Correct as needed. If you are too sharp into the arc (say you see 6.2nm after rollout), continue flying 90 degrees off the entry radial until you get back to 7nm. If you are too wide, fly 110 degrees or so off the entry radial until you get back to 7nm. Now that you are on the arc manage a slight bank to keep your DME around 7nm. If it starts to climb slightly, add a few more degrees of bank. If it starts to drop slightly, shallow out. There's no exact science needed here.

 

If you want to get fancier, use the 10/10 method. After turning 90 degrees off the entry radial, twist to the next radial that's 10 degrees higher. So a 260 entry radial would mean the next radial you set is 270 and turn 10 degrees from your present heading. You will then intersect the next radial at 90 degrees. Once you do, dial in the 280 radial, turn 10 degrees, and repeat. So on and so forth.

If you could visualize how that works, you are not flying a perfect arc. You are really making steps along the arc but within a legal distance. Same thing if you just watch the DME and correct without the 10/10 method. You will not fly it perfectly nor are you expected to. The tolerances are 1nm from the center of the arc. So between 6-8nm in your example is legal.

 

You seem to be expecting to fly it at 7nm, perfectly, with a beautiful continuous bank that forms a perfect arc. That ain't gonna happen with just a single VOR. Arcs require continual correction and they absolutely can be flown with just a VOR and DME.

 

Sadly not in Spain :( we have norms more restrictive than the FAA. Here, as far as I know it is only 0.5 nautical miles on each side of the arc. I did not find a document that can confirm this, and I am trying to find it, but I have a friend, that is pilot in a low cost, and also flight instructor in Spain and told me 0.5 on each side. I have other friend private pilot and told me also 0.5 nm for Spain. I know in the US is 1 nm (lucky you), it is clearly indicated in the FAA document FAA-S-8081-4E, but as far as I know two persons told me already in Spain this is 0.5 on each side.

 

My problems start and end with the beauty of the path.

With wind I cannot get a perfect arch and not always I can fly with the same progression 10/10... sometimes winds change to fast I need to use 5/10 or 10/15...

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Don't stop trying for "perfection" but also don't beat yourself up if you don't achieve it. The majority of your arcs should be legal and a few may even be perfect but you will NEVER achieve your "beautiful painting" every time. There are too many variables. Under normal wind conditions you should be able to maintain 0.5 if you follow the instructions posted by Bonchie & NickATC. there is no other way - you must stay AHEAD of the aircraft, meaning you have to recognize the wind effect and anticipate your heading changes to maintain your arc - if you wait until the needle moves - it's too late - you are then trying to catch up.

 

 

Vic

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First, sorry for the extension of my reply. However I want to explain step by step how I am flying archs and the problems I am facing. I was practicing archs 20 days more or less. Yes, I've corrected the anticipation problem. My fault, I am sorry. :wink:

 

Hi vgbaron

 

Don't stop trying for "perfection" but also don't beat yourself up if you don't achieve it. The majority of your arcs should be legal and a few may even be perfect but you will NEVER achieve your "beautiful painting" every time. There are too many variables. Under normal wind conditions you should be able to maintain 0.5 if you follow the instructions posted by Bonchie & NickATC. there is no other way - you must stay AHEAD of the aircraft, meaning you have to recognize the wind effect and anticipate your heading changes to maintain your arc - if you wait until the needle moves - it's too late - you are then trying to catch up.
Vic

 

I am more relaxed now, after reading this, I was kinda obsessed with a perfection flying archs. I was trying to fly archs with winds so strong as 45 MPH (72 KM/H) and is impossible with winds so strong flying a perfect arch. I am explaining anyway in this post how I am flying the archs.

I am able now to maintain archs with wind calm, absolutely perfect with a beautiful path, however when we have wind... I can hold the arch but it is not so beautiful. Reading you gives me more confidance.

 

Hi NickATC

 

Bonchie nailed it.  I'm a navigation instructor, maybe my tips can give you another look at the same topic:

 

 

Lucky we have you in the forum NickATC, willing to help everyone with so much knowledge.

First my apologies for my delayed reply. I was away almost 20 days, I am back now reading everything. However I was not loosing time, I was practicing the archs all the time.

 

I am now able to fly archs with a beautiful path, hower with wind calm.

When I start to have 17 knots of wind... I am able to fly the arch, but I cannot maintain a path extremely beautiful. When I mean extremely beautiful, I mean a path done with a compass. Perfect and exact. I am able to do that with wind calm, but know when I have 17 knots of wind.

With wind I fly, let's say eliptical archs. They are archs, they are inside the legal limits, but they are not 100% perfect.

 

THE ERROR OF THE ANTICIPATION.

I've corrected that. Yes.

SInce the video I posted I corrected this. Yes, absolutely.

The chart don't tell you, you must turn to enter in the arch at 5.0 nm from the VOR/DME.

 

The chart tells you, in that moment is when you can start to turn, but according the anticipation you must calculate. And for that we need a formula: 0.5% GS (that is the zero point five percent of the Ground Speed).

So, if I have to maintain an arch of 7.0 nm... the first thing I must do is having a constant speed.

Then, I must calculate the anticipation to the arch.

 

EXAMPLE ABOUT HOW TO ANTICIPATE AN ARCH:

  1. Let's say we will fly with 120 knots.
  2. It is important trying to hold this speed.
  3. We apply the formula to our speed, the 0.5 % of the speed we are flying to calculate the anticipation to the arch.
  4. Then 120 knots x 0.5 / 100 = 0.6 nautical miles of anticipation to the arch, to this speed, 120 knots.
  5. If the arch I have to follow is 7.0 nm... and I need to anticipate 0.6 nautical miles to it, we deduce that quantity to the arch.
  6. 7.0 nm - 0.6 nm = 6.4 nm
  7. I must start my turn to 6.4 nm because I am flying to 120 knots.

 

IN A PRACTICAL WAY: There are sometimes that you will enter at 6.3 and it works perfectly the same, because your fingers are not always so smart to do this in the right moment like a computer... but it works well too.

 

I've been flying archs almost one month... so I explain right now how I was flying them.

 

Let's forget for the moment the departure from the arch, ok? Most important thing right now, to hold the arc. ;)

 

Lucky people in the US have a permisive FAA that allow 1 nm of legal limit on each side of the arch.

Unlucky people in Spain have more restrictive authorities that only allow 0.5 nm on each side of the arch.

 

So I assume as correct only 0.5 nm on each side of the arch, ok? Because I will be flying in my area.

 

Yes, NickATC as you said the key is being perpendicular to the path, to hold the arch.

That is your heading must add a 90º degrees difference to your entrance radial.

However... sometimes this is not easy to achive... there is wind... you are distracted, you are taking a look to other instruments...

Anyway, the first enemy here is the wind...

With wind I am not always able to be perpendicular to the arch, so I am not always able to have a perfect path with a difference of 90º between the radial and the aircraft's heading.

 

HOW I AM FLYING VOR/DME ARCHS WITHOUT RMI (ONLY HSI):

 

As a rule:

  • When DME show us more nautical miles than the arch, for example, we must follow an arch of 7.0 nm and our DME is showing us 7.2 nm (we are departing from the arch) in that case, to correct, I use more OBS and more HDG.

For example: I set my OBS to 10 and my HDG to 10 or my OBS to 10 and my HDG to 15.

  • When DME show us less nautical miles than the arch, for example, we must follow an arch of 7.0 nm and our DME is showing us 6.8 nm (we are nearing to the arch) in that case, to correct, I use less OBS and less HDG.

For example: I set my OBS to 5 and my HDG to 5 or my OBS to 5 and my HDG to 3.

 

I always divide the arch in segments of 5 or 10, so I always use 5 or 10 for the OBS.

In the case of HDG, I can change that quantity for other values as 1... 3... 5... 10... 15... or even 20 as much.

 

As for my experience.
Kinds of archs we can fly, according the quality of their paths.


Perfect arch with perfect path.

  • Is more easy to get achieved with wind calm.
  • When the OBS is the same as the HDG adding degrees (if we have an arch to the right side, clockwise) or
  • When the OBS is the same as the HDG deducing degrees (if the arch is to the left side, anticlockwise)...
  • In this case, the path is perfect. You will achieve a beautiful perfect circular arch.
  • So... we need always the OBS and the HDG in the same progression. That is 5 / 5 or 10 / 10 when we hold the arch... and if we maintain always this progression, the arch will have a beautiful circular path.

 

Elliptical arch. Regular path, but not perfect.

  • When the OBS and the HDG are not equal adding degrees (if our arch is to the right side, clockwise) or...
  • When the OBS and the HDG are not equal deducing degrees (if our arch is the the left side, anticlockwise)...
  • We will achive an elliptical arch, regular, but not perfect.

For example:
If OBS and HDG goes in different progression... OBS 5 / HDG 3... OBS 10 / HDG 15... OBS 5 / HDG 1... OBS 10 / HDG 20... and we maintain different progression of the OBS and the HDG during the arch, we will get an elliptical arch, with regular path but not perfect. It will looks like an ellipse, but a perfect, circular arch.

 

Squiggly arch.
Usually I get this arch in strong wind conditions. 45 MP/H (72 KM/H). Those conditions are close to a strong tropical thunderstorm or close to a hurricane (Isidore Hurricane, 2002, showed winds of 45 MPH)

  • The arch is always divied in segments of 5 or 10 radials with the OBS.
  • The HDG will always add degrees or deduce degrees, to maintain the path of the arch.
  • If our arch is to the left side, we will deduce degrees in the HDG to maintain the arch (anticlockwise)
  • If our arch is to the right side, we will add degrees in the HDG to maintain the arch (clockwise).

However, in strong wind conditions... we will have suddent gusts of wind that will push our aircraft toward or away the station (VOR).
In fact, when we enter the arch, the wind will push as in a certain direction, when we be in the middle of the arch, the wind will push us in a different direction, and also, when we be close to end our arch... the wind will push us in a different direction. Because our heading is changing, the angle the wind is pushing us, change also.

 

When the wind push us hard... is complicated to hold the arch.

More complicated is in this case doing a nice arch and not a "potato" (sorry for the expression, I prefer to use plain words).

What I am doing to maintain the arch in strong wind conditions is:

  • Dividing the arch in 5 radials or 10 radials.
  • Moving the HDG to the right side (add degrees) or to the left side (dedude degrees) to my heading.

When you do this, for sure you will get an squiggly arch.

Talking mathematically, if we have a clockwise arch, your HDG will have to add always degrees to your heading, to follow the progression of the arch. If you are painting an arch to the right side with your hand, it must move to the right side, adding degrees to draw a circular path.

If something external affect you, be the wind hitting your hand or someone kicking your drawing table... then... your hand (aircraft) will have to correct this moving from left to right or right to left, to try to draw a circular path.
 

When I am facing strong wind conditions, I move the HDG knob to the left side or right side, deducing degrees or adding degrees to my actual heading, because the only I have in mind is to hold the arch inside the legal limits.

 

However... in this case, the path will be squiggly.

 

I think I have a problem with that. My mind cannot assume I can present as perfect a squiggly arch... when weather conditions are so strong... that wind is pushing me in all directions.

 

I would love to read your comments please.

Cheers

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