GPS Direct to fix, homing vs track

Rheo

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Rheo
Last week I was flying home IFR and toward the end of the flight was cleared direct to destination. I dutifully hit direct on the GPS and turned to join that course, no big deal. As I got closer, increasing crosswinds and turbulence (my path took me closer and closer to mountains) meant I had to continually increase my correction angle to center up the CDI and rejoin the leg. So my question is this: in this case, is it ok to just recompute a direct course (homing, essentially), or am I expected to rejoin the original course from the point where I was cleared direct? Does a GPS Direct have the same 4nm lateral width like an airway? If I'd gotten way off, I can see needing to rejoin but this was like maybe 1/4 needle deflection at most. This was in Approach airspace, if it matters.
 
Welcome to POA!

I don't really understand why you went off course. You were cleared to destination and hit Direct, resulting in a course line that was reflected on your CDI/HSI. Keep it centered. If you need a 30 degree correction reference heading, so be it. If the winds are too strong for you to maintain a course, consider a diversion, especially if it's forcing you into inhospitable terrain.

If you insist on your homing solution, I'd still be contacting ATC to let them know what's going on and have a conversation about what to do, especially in TRACON airspace where your continually going off course can cause a separation problem for them.
 
Your statements don't compute. If you were headed direct to, you shouldn't have been drifting. what leg were you rejoining? If you were direct to, there's no leg to rejoin you're on the leg. What your saying just doesn't make sense to me.
 
I understand your situation and conditions. Your were cleared a direct course from your current position to the destination. Direct is direct, not let the winds aloft push you off course and recompute a new course from random positions.

In addition to the CDI, you can compare the desired track and actual track on the GPS to quickly determine the correct wind correction angle.
 
To clarify, I wasn't really off-course in any appreciable way, just having to make increasing crosswind corrections, and the FlightAware track shows the usual mild scalloping that goes along with that. I wasn't anywhere near truly inhospitable terrain, but this was in the Front Range of the Rockies and the effects persist a long way downwind. I did mention to the controller I was having some difficulty holding altitude (+/- 100 feet) due to turbulence and only got a "Roger" in response. It was a quiet trip, radio-wise.

The question was more just idle speculation: in radar airspace, where a controller could give me a specific heading if operationally necessary, how much leeway does a "direct" routing give you? As long as one is always pointed toward the destination, is it an issue? It's kind of tempting to want to reach up and press D-> and have the needle magically recenter when fighting the wind.
 
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It's like this?
You drift a little off course and develop some cross-track error and then you want to fly direct from a new point rather than flying back to your original path?
Is the question essentially how much XTE can you develop before there is an issue?

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Rejoin the course that was input when you initially entered direct to the WPT. If VFR, hitting direct from current position is fine, but not while on an IFR plan.
 
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If you get cleared direct,when you keep adjusting,the controller will probably ask you if your still flying direct.
 
It's like this?
You drift a little off course and develop some cross-track error and then you want to fly direct from a new point rather than flying back to your original path?
Is the question essentially how much XTE can you develop before there is an issue?
Yeah, this was exactly my question. And I totally understand that it's probably a "what you can get away with" thing. 5 miles? No way. Half mile... maybe? And distance to fix probably affects things too.

Regarding flying GPS track, a G5 etc. to make that easier would be nice. I've been in the situation around here with varying winds where I'll get an assigned heading, and a minute later, 10 left or whatever, and a minute later, another change. It's too bad controllers can't just assign a ground track.
 
It's kind of tempting to want to reach up and press D-> and have the needle magically recenter when fighting the wind.
Don't do it. It's terrible form and if you make it a habit you will fly an arc to your destination. Do it frequently enough and you'll never get there at all.

Learn how to fly straight. Are you using your DG? Does your GPS show desired and actual track? Get on course, fly the heading that makes them equal, hold the heading, and check your GPS every couple of minutes. It's not difficult, but staring at the moving map will give poor results.
 
Hmmm. Intercepting and tracking courses derived from a NAVAID is fundamental to IFR flight. So much so it's one of the required currency tasks per 61.57. Continuously hitting the direct to button is not tracking. Some additional practice applying a wind correction angle and keeping the CDI centered might be helpful.
 
…Learn how to fly straight….

giphy.gif


Yeah. That.
 
To be clear: I flew this on course, correcting for wind as needed, using my DG to hold heading(s). This was just a 'what if?' question given the "cleared direct" (that I rarely get) and the winds/turbulence that day. Certainly not looking to pick up a bad habit or bust regs!
 
This seems to be a simple problem with a simple solution.

Direct = direct. Fly directly to your destination. Use the required WCA to maintain your course. If the winds are pushing you off-course, make a bigger correction and fly the plane. Don't let the plane fly you.

That's it.

If for some reason you find yourself off-course (using proper inputs, you shouldn't, unless the winds are dangerously strong) and wish to go direct from present position, good form would call for bringing ATC into that discussion, admitting you're off-course, and requesting a new direct-to from present position. But it would be best to simply fly direct in the first place. If you're having a hard time with that, it may represent a good reason to get some additional training.
 
To clarify, I wasn't really off-course in any appreciable way, just having to make increasing crosswind corrections, and the FlightAware track shows the usual mild scalloping that goes along with that. I wasn't anywhere near truly inhospitable terrain, but this was in the Front Range of the Rockies and the effects persist a long way downwind. I did mention to the controller I was having some difficulty holding altitude (+/- 100 feet) due to turbulence and only got a "Roger" in response. It was a quiet trip, radio-wise.

The question was more just idle speculation: in radar airspace, where a controller could give me a specific heading if operationally necessary, how much leeway does a "direct" routing give you? As long as one is always pointed toward the destination, is it an issue? It's kind of tempting to want to reach up and press D-> and have the needle magically recenter when fighting the wind.
+/-100 is no big deal. But, “Roger” doesn’t give you a clearance to bust altitudes. Ask for a block altitude if you need it.
 
but this was in the Front Range of the Rockies and the effects persist a long way downwind
I flew the Front Ranger (based as APA) for 20 years. Doesn’t matter. You have a course to fly. Fly it. If you can’t because you can’t handle it, divert.
 
Direct is direct. ATC is expecting you to fly from where you were issued direct to your destination, and ATC may direct traffic where they don't expect you to be. If you get too far from the expected course, ATC is going to ask you where you are going so they can keep everyone apart. You use whatever wind correction angle is required to stay on course. If it's 20 degrees, it's 20 degrees. If you want to be routed more downwind from mountain turbulence, just ask for a diversion to where you want to be.
 
Last week I was flying home IFR and toward the end of the flight was cleared direct to destination. I dutifully hit direct on the GPS and turned to join that course, no big deal. As I got closer, increasing crosswinds and turbulence (my path took me closer and closer to mountains) meant I had to continually increase my correction angle to center up the CDI and rejoin the leg. So my question is this: in this case, is it ok to just recompute a direct course (homing, essentially), or am I expected to rejoin the original course from the point where I was cleared direct? Does a GPS Direct have the same 4nm lateral width like an airway? If I'd gotten way off, I can see needing to rejoin but this was like maybe 1/4 needle deflection at most. This was in Approach airspace, if it matters.
Short answer, given longer already, is no. You are to TRK directly to the waypoint. The HDG you need to stay on that track is for you to figure out. An HSI makes it much easier. So you need to rejoin the original line; sounds like you were about a mile left or right of course.

If the destination needed an approach, and the controller who cleared you direct was in the destination's airspace, that's a good time to ask for direct to an IAF unless asked for or told to expect VTF.
 
Last week I was flying home IFR and toward the end of the flight was cleared direct to destination. I dutifully hit direct on the GPS and turned to join that course, no big deal. As I got closer, increasing crosswinds and turbulence (my path took me closer and closer to mountains) meant I had to continually increase my correction angle to center up the CDI and rejoin the leg. So my question is this: in this case, is it ok to just recompute a direct course (homing, essentially), or am I expected to rejoin the original course from the point where I was cleared direct? Does a GPS Direct have the same 4nm lateral width like an airway? If I'd gotten way off, I can see needing to rejoin but this was like maybe 1/4 needle deflection at most. This was in Approach airspace, if it matters.
They cleared you direct to destination from a point you were at at that time. That is what they expect you to do. If the wind is pushin’ you around a little, get back on what you were cleared to do.

EDIT: I read on and there is a consensus answer to this. Don’t twist to get centered, fly to get centered.
 
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I think this is a great question. Something I've wondered about before too, in a theoretical camfire discussion kind of way.....

I find a lot of this discussion to be a little ...well pendantic

I'd be very curious for a controller or three to chime in with their comments...and from different perspectives...en route vs terminal, etc...
Do they enter such things into the computer and it plots a course line? Does that line get passed on to controllers in the following sectors?

Just thinking about it logically
I think that it's clear what folks have said here that direct means direct. In theory, when you're cleared direct from point A to point B that this line, or really path of some width has been determined to be clear for you...traffic conflicts, terrain, obstacles, airspace issues, etc...

So my assumption is that yes, in the short distances say for example in the terminal area, that's probably a fairly narrow path you're cleared for and it's expected..... of course...absolutely.
but do they have enough memory bandwidth to really keep track if you've drifted off course a couple hundred yards? maybe 1/4 mile off ok maybe.... 5 miles off, alarm bells go off, or whatever...They're continuing overwatch anyway, and even if you stay on course if conditions change they'll amend.
Regardless, clearly that line is the intended clearance and that's the path they want you on.

Now take that same scenario put in the context of en route. Say I'm in Florida and I depart for a destination say in Kentucky.... and I'm cleared direct to some IAP up there. Of course it's expected to follow that line....but realistically they probably aren't going to remember with precision, I'd think they are just expecting you in that general direction... in this case once I'm way up into North GA and I'm off course 6 miles, does anyone really even know?
not good...true enough
theory says I should correct and get back onto the intended original course ASAP. Yes, Absolutely
But real world?
 
If you're vfr and given a direct to xxx, if you've let the CDI drift off center, it's your choice whether to intercept the original track or just hit direct to again and do a better job keeping it centered. I don't believe ATC projects a couirseline for your aircraft from the point you're given a "direct to" instruction so unless you're grossly off course to that point, they don't care. They are separating aircraft by looking at their scope and seeing conflicts and dealing with them as they come up. ATC is not responsible for separating vfr traffic from IFR traffic, they do it as their workload permits but you pilots are the ones responsible for separation when VFR. ATC is only 100% responsible for separating IFR traffic from other IFR traffic. Just my opinion so I'd like to hear from a controller.
 
I think this is a great question. Something I've wondered about before too, in a theoretical camfire discussion kind of way.....

I find a lot of this discussion to be a little ...well pendantic

I'd be very curious for a controller or three to chime in with their comments...and from different perspectives...en route vs terminal, etc...
Do they enter such things into the computer and it plots a course line? Does that line get passed on to controllers in the following sectors?

Just thinking about it logically
I think that it's clear what folks have said here that direct means direct. In theory, when you're cleared direct from point A to point B that this line, or really path of some width has been determined to be clear for you...traffic conflicts, terrain, obstacles, airspace issues, etc...

So my assumption is that yes, in the short distances say for example in the terminal area, that's probably a fairly narrow path you're cleared for and it's expected..... of course...absolutely.
but do they have enough memory bandwidth to really keep track if you've drifted off course a couple hundred yards? maybe 1/4 mile off ok maybe.... 5 miles off, alarm bells go off, or whatever...They're continuing overwatch anyway, and even if you stay on course if conditions change they'll amend.
Regardless, clearly that line is the intended clearance and that's the path they want you on.

Now take that same scenario put in the context of en route. Say I'm in Florida and I depart for a destination say in Kentucky.... and I'm cleared direct to some IAP up there. Of course it's expected to follow that line....but realistically they probably aren't going to remember with precision, I'd think they are just expecting you in that general direction... in this case once I'm way up into North GA and I'm off course 6 miles, does anyone really even know?
not good...true enough
theory says I should correct and get back onto the intended original course ASAP. Yes, Absolutely
But real world?
You may be right about the "who cares?" in an enroute environment with no other traffic around but, at least from my perspective, the pedantry has two points:
1. You don't know whether you are affecting other traffic or not.​
2. It's sloppy airmanship. And like a lot of other things, what you do becomes habitual. It becomes your SOP. Don't care about holding a course. When it's most important - busy airspace, lots of traffic, lots of communications - you won't be able to do it. We are what we practie.​

It's similar to landing on the runway centerline. Pilots who don't come up will all sorts of good "reasons." But the bottom line, as a pilot/CFI friend of mine once said, "The reason pilots don't land on the centerline is because they can't"

Or, if you prefer Star Trek, "“It was far easier for you, as civilized men, to behave like barbarians than it was for them, as barbarians, to behave like civilized men.”"
 
I think this is a great question. Something I've wondered about before too, in a theoretical camfire discussion kind of way.....

I find a lot of this discussion to be a little ...well pendantic

I'd be very curious for a controller or three to chime in with their comments...and from different perspectives...en route vs terminal, etc...
Do they enter such things into the computer and it plots a course line? Does that line get passed on to controllers in the following sectors?

Just thinking about it logically
I think that it's clear what folks have said here that direct means direct. In theory, when you're cleared direct from point A to point B that this line, or really path of some width has been determined to be clear for you...traffic conflicts, terrain, obstacles, airspace issues, etc...

So my assumption is that yes, in the short distances say for example in the terminal area, that's probably a fairly narrow path you're cleared for and it's expected..... of course...absolutely.
but do they have enough memory bandwidth to really keep track if you've drifted off course a couple hundred yards? maybe 1/4 mile off ok maybe.... 5 miles off, alarm bells go off, or whatever...They're continuing overwatch anyway, and even if you stay on course if conditions change they'll amend.
Regardless, clearly that line is the intended clearance and that's the path they want you on.

Now take that same scenario put in the context of en route. Say I'm in Florida and I depart for a destination say in Kentucky.... and I'm cleared direct to some IAP up there. Of course it's expected to follow that line....but realistically they probably aren't going to remember with precision, I'd think they are just expecting you in that general direction... in this case once I'm way up into North GA and I'm off course 6 miles, does anyone really even know?
not good...true enough
theory says I should correct and get back onto the intended original course ASAP. Yes, Absolutely
But real world?
“…Do they enter such things into the computer and it plots a course line? Does that line get passed on to controllers in the following sectors…” Some Radars had the ability to throw up a course line. Probably almost all nowadays. You wouldn’t leave it on the scope, just do it to get a picture of where the planes going to go when given Direct. It wouldn’t transfer to another controllers scope. The new guy can throw one up on his scope if he needs a look.

You’ve got a pretty good summary of how distance affects things. How critical it’s going to be depends on a lot of things. How busy is it? Is the Controller running things kind tight because he has lotsa planes and not a whole lot of airspace. Adjacent airspace can come into play. Controller may throw up the line, see that it will clear adjacent Sectors and give you Direct. Then you start drifting. Now he’s gotta do something. Vector you away and when he can give Direct again hope you don’t mess it up again. Or can point you out to the Controller in that Sector. Both of these take time.
 
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I don't find this discussion pedantic at all.

There's really no more accurate or applicable answer than to say, "real world, attempt to fly your clearance as precisely as possible, all the time, and if you find yourself off-course, point it out to the controller and work out a solution."

The idea that "it doesn't matter," or "no one cares or is watching, etc." just doesn't compute. The NAS is ATC and pilots working together. You have a job, so does ATC. Do your job to your highest level of ability and if you find yourself falling short, a) correct the issue, b) let ATC know if you're making an adjustment they weren't expecting, and c) seek out training to improve these shortcomings in the future.
 
In a low traffic environment, it may not matter if you are 20 degrees off-course for traffic separation on a direct-to clearance. I'm sure ATC doesn't plot a course line after your direct-to clearance, but ATC does know where you are heading. If you are 20 degrees off course, eventually ATC will notice you are not flying toward where you are supposed to be, and you may get an inquiry. If you wander like this from an airway while IFR, it's not so good. Ultimately, this is just basic airmanship.
 
There is no +/- 4nm flying IFR. That is the width of an airway, and the controlled airspace associated with it. It does not mean that an IFR flight can fly anywhere within that 8nm-wide path.

14 CFR § 91.181 Course to be flown.

Unless otherwise authorized by ATC, no person may operate an aircraft within controlled airspace under IFR except as follows:

(a) On an ATS route, along the centerline of that airway.

(b) On any other route, along the direct course between the navigational aids or fixes defining that route. However, this section does not prohibit maneuvering the aircraft to pass well clear of other air traffic or the maneuvering of the aircraft in VFR conditions to clear the intended flight path both before and during climb or descent.
 
Direct (assuming you're not on a PBN procedure) is not a laser beam in the sky. Can modern aircraft's nav equipment make it seem that way? Yes. If you're in a radar environment and the controller needs you to fly something for separation, he/she should assign a radar vector. Should you turn 90 degrees because you're 1.2 miles off of the original track? No, but using a little fudge factor in your heading probably will never be noticed by the controller. As for the route display, ERAM will provide one for the center controller. It's not uncommon for somebody to be 2-3 miles off of "our" route centerline. Much more than that and the controller will probably ask.
 
There is no +/- 4nm flying IFR. That is the width of an airway, and the controlled airspace associated with it. It does not mean that an IFR flight can fly anywhere within that 8nm-wide path.

14 CFR § 91.181 Course to be flown.

Unless otherwise authorized by ATC, no person may operate an aircraft within controlled airspace under IFR except as follows:

(a) On an ATS route, along the centerline of that airway.

(b) On any other route, along the direct course between the navigational aids or fixes defining that route. However, this section does not prohibit maneuvering the aircraft to pass well clear of other air traffic or the maneuvering of the aircraft in VFR conditions to clear the intended flight path both before and during climb or descent.
Good citation
 
When a pilot comes off an airport and controllers say "Proceed Direct to FIXXX", it's another thing to keep an eye on and monitor if a pilot starts flying Southeast bound for a fix that is due south.

You should go direct the fix from wherever you are, not fly towards the Magenta line you laid down while you were doing a runup.

Again, I'm not sure if this is a regulatory thing that's required, or if it's "Don't scare your controller" type stuff.

Just my two cents. Subject to change. And also not the opinion of any agency, administration, or anyone that matters much.
 
When a pilot comes off an airport and controllers say "Proceed Direct to FIXXX", it's another thing to keep an eye on and monitor if a pilot starts flying Southeast bound for a fix that is due south.

You should go direct the fix from wherever you are, not fly towards the Magenta line you laid down while you were doing a runup.

Again, I'm not sure if this is a regulatory thing that's required, or if it's "Don't scare your controller" type stuff.

Just my two cents. Subject to change. And also not the opinion of any agency, administration, or anyone that matters much.
This is actually a topic that was brought up this the week on Opposing Bases. It's apparently happening with more regularity. The issue is ATC is expecting a pilot do X as part of their overall airspace management plan which is dynamic and predicated on everyone doing their part in a timely fashion. When they do Y without coordination it can lead to separation errors and potentially a collision.
 
You should go direct the fix from wherever you are, not fly towards the Magenta line you laid down while you were doing a runup.

Again, I'm not sure if this is a regulatory thing that's required, or if it's "Don't scare your controller" type stuff.
14 CFR 91.181 -
(b) On any other route, along the direct course between the navigational aids or fixes defining that route. ...

P/CG -
DIRECT− Straight line flight between two navigational aids, fixes, points, or any combination thereof
 
To clarify, I wasn't really off-course in any appreciable way, just having to make increasing crosswind corrections, and the FlightAware track shows the usual mild scalloping that goes along with that. I wasn't anywhere near truly inhospitable terrain, but this was in the Front Range of the Rockies and the effects persist a long way downwind. I did mention to the controller I was having some difficulty holding altitude (+/- 100 feet) due to turbulence and only got a "Roger" in response. It was a quiet trip, radio-wise.

The question was more just idle speculation: in radar airspace, where a controller could give me a specific heading if operationally necessary, how much leeway does a "direct" routing give you? As long as one is always pointed toward the destination, is it an issue? It's kind of tempting to want to reach up and press D-> and have the needle magically recenter when fighting the wind.

Direct to vs fly a heading are two entirely different things. Cleared direct means you are flying whatever heading is necessary to maintain the computed direct course (magenta line) from the present position to the fix provided in the cleared to instruction. In GPS speak, push direct to and fly whatever heading is required for the needle to be centered and verify DTK=TRK.

When ATC give you a fly heading instruction, you are flying that heading without any wind correction; your ground track will drift based on the wind. In this instance, bug the heading and fly it. TRK will deviate from DTK, but that’s irrelevant to the instruction.
 
14 CFR 91.181 -
(b) On any other route, along the direct course between the navigational aids or fixes defining that route. ...

P/CG -
DIRECT− Straight line flight between two navigational aids, fixes, points, or any combination thereof
That's kinda where I figured the disconnect was. A "point" is either a point on your flight plan, or the place you currently are, depending on what you have in your head. Is there a definition that sums all this up? I can't think of anything off hand...which isn't saying much, really.

I think my phraseology of "proceed present position direct FIXXX" might be more right than wrong these days, in light of the ambiguity of the rules, or the ambiguity of the consensus of the rules. Is that the best way to say it? Another weird situation we've got here.

It's been a good, and civil, discussion though. So hopefully we'll be able to muck through all this together.
 
That's kinda where I figured the disconnect was. A "point" is either a point on your flight plan, or the place you currently are, depending on what you have in your head. Is there a definition that sums all this up? I can't think of anything off hand...which isn't saying much, really.

I think my phraseology of "proceed present position direct FIXXX" might be more right than wrong these days, in light of the ambiguity of the rules, or the ambiguity of the consensus of the rules. Is that the best way to say it? Another weird situation we've got here.

It's been a good, and civil, discussion though. So hopefully we'll be able to muck through all this together.
Where’s the ambiguity?
 
That's kinda where I figured the disconnect was. A "point" is either a point on your flight plan, or the place you currently are, depending on what you have in your head.
"Cleared direct [waypoint]" is the clearance. How can that phraseology mean direct from anywhere other than your present position?
 
That's kinda where I figured the disconnect was. A "point" is either a point on your flight plan, or the place you currently are, depending on what you have in your head. Is there a definition that sums all this up? I can't think of anything off hand...which isn't saying much, really.

I think my phraseology of "proceed present position direct FIXXX" might be more right than wrong these days, in light of the ambiguity of the rules, or the ambiguity of the consensus of the rules. Is that the best way to say it? Another weird situation we've got here.

It's been a good, and civil, discussion though. So hopefully we'll be able to muck through all this together.

This is possibly among the least ambiguous regulations and ATC phraseology we have in aviation. There should be absolutely no confusion on this matter.
 
How about a slightly different situation in the same vein: you're flying from FIXXA to FIXXB and vectored off course for a bit for weather, traffic, whatever. Then the controller comes back with just "resume own navigation". Do you rejoin your original course or go direct from present position to FIXXB? In the ancient world of VORs you'd probably need to rejoin a known radial to get back on course but in the modern GPS world it could always be a direct-to.
 
How about a slightly different situation in the same vein: you're flying from FIXXA to FIXXB and vectored off course for a bit for weather, traffic, whatever. Then the controller comes back with just "resume own navigation". Do you rejoin your original course or go direct from present position to FIXXB? In the ancient world of VORs you'd probably need to rejoin a known radial to get back on course but in the modern GPS world it could always be a direct-to.
That's poor technique on the part of the controller. I would suggest asking, "Do you want me to go direct FIXXB?"
 
How about a slightly different situation in the same vein: you're flying from FIXXA to FIXXB and vectored off course for a bit for weather, traffic, whatever. Then the controller comes back with just "resume own navigation". Do you rejoin your original course or go direct from present position to FIXXB? In the ancient world of VORs you'd probably need to rejoin a known radial to get back on course but in the modern GPS world it could always be a direct-to.
Just going direct FIXXB would be the easiest. Communicate to the Controller that is what you will do. FWIW, the Controller is supposed to tell you what to expect next when they initiate the vector, but they don’t always do what they are supposed to. If they don’t, ask. Like ‘heading ###, what can I expect next.’
 
How about a slightly different situation in the same vein: you're flying from FIXXA to FIXXB and vectored off course for a bit for weather, traffic, whatever. Then the controller comes back with just "resume own navigation". Do you rejoin your original course or go direct from present position to FIXXB? In the ancient world of VORs you'd probably need to rejoin a known radial to get back on course but in the modern GPS world it could always be a direct-to.
He's not going to say "resume own navigation".

When you request the deviation, he'll say, "[left/right] deviations approved, direct [FIXXB] when able (and advise)"
 
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