KLN 89 "Direct To" - Is it updated continuously?

D

DCR

Pre-Flight
Joined
Jun 14, 2023
Messages
80
Display Name
Display name:
rudy
Quick question:

Let's say I enter direct to KLAX in my KLN89 and it calculates desired track 270°.

Next, I get distracted and notice I've been flying 285° for idk 5 or 10 minutes.

Does the GPS update my desired track so that it's always pointed at the next waypoint or do I need to recalculate by clicking through "direct to" again?

Follow up Q if you're still reading: do most other GPS function the same as KLN or does this feature vary between models?

Thanks
 
DCR said:
Does the GPS update my desired track so that it's always pointed at the next waypoint or do I need to recalculate by clicking through "direct to" again?
Click to expand...
Neither. Your GPS plots a course once. Please don't click "direct to" again every time you get off course. That is called homing and is incredibly poor technique.
 
As @dmspilot said, when you punch Direct (in every GPS-based unit I've used from Garmin, Avidyne, Dynon, as well as the dozen or so EFBs I've looked at), it creates a course. If you go off course, whether because of inattention, vectors from ATC, or diversion for weather or sightseeing, you need to hit Direct again to create a new course if you want to go Direct from your present position rather than reintercept the existing course.
 
  • Like
Reactions: DCR
Exact answer to your question is a "direct to" does a course from where you are when you press the button to the waypoint. If you fly off course and hit it again, it will repeat the process. What it won't do is get you back to the original course line. The problem with that is there might be an obstruction, airspace etc between your new position and the waypoint you are going to. That is consistent between GPS models.
@dmspilot point is you should have the situational awareness to return to your course vs just re-hitting "direct to" when you get off course. In many situations, it's not a big deal, but if there is a big honking tv antenna, or a restricted airspace near your course, you could be putting it in your path.
 
dmspilot said:
Neither. Your GPS plots a course once. Please don't click "direct to" again every time you get off course. That is called homing and is incredibly poor technique.
Click to expand...
Agreed, but with a caveat. Let's say you're flying direct from a controlled airport (let's say a reasonably busy Class C for argument) to another airport. When you initially enter the flight plan (or "direct to") course in your GPS prior to take-off, you get a fancy magenta line directly from one airport to another. After take-off, you receive the ATC instruction to "turn on course". In this instance, it *would* be appropriate to hit "direct-to" again, and fly direct from your current location. If you don't, and try to veer back over to your original magenta line, you may be doing something that ATC doesn't expect, especially if it's a fairly significant correction.
 
midlifeflyer said:
when you punch Direct (in every GPS-based unit I've used from Garmin, Avidyne, Dynon, as well as the dozen or so EFBs I've looked at), it creates a course. If you go off course, whether because of inattention, vectors from ATC, or diversion for weather or sightseeing, you need to hit Direct again to create a new course if you want to go Direct from your present position rather than reintercept the existing course.
Click to expand...

Thanks that is exactly what I was hoping to find out. Thanks!
 
Hang 4 said:
In many situations, it's not a big deal, but if there is a big honking tv antenna, or a restricted airspace near your course, you could be putting it in your path.
Click to expand...

Not quite following your logic here. How did I know my first "direct-to" wasn't going to put me on course with that TFR or big antenna to begin with?
 
Nice pic that explains the various terms used while navigating…
4d7825b4590378c6d28559a5e4a90a66.gif

The red “course” line is what GPS’s call “DTK” (desired track)


Sent from my iPhone using Tapatalk
 
Matthew said:
Why would you select a Direct To unless you knew you were on a safe course?
Click to expand...

Gotchya - so if I've gone off course I need to re-verify my new course is safe / legal.

I thought for some reason Hang was saying the GPS checked my first DTO for obstacles.
 
midlifeflyer said:
not whether you should or shouldn't do certain things with it.
Click to expand...

Very rare to get an actual answer to your question without added unsolicited advice.

Then again this is the "training" forum, and I do appreciate the technique tips in this case.
 
DCR said:
I thought for some reason Hang was saying the GPS checked my first DTO for obstacles.
Click to expand...
Nope, just the opposite, that's on you. I was presuming you had checked the original course, that's kind of the point in navigating. GPS will happily fly you into a mountain.
 
AvNavCom said:
Agreed, but with a caveat. Let's say you're flying direct from a controlled airport (let's say a reasonably busy Class C for argument) to another airport. When you initially enter the flight plan (or "direct to") course in your GPS prior to take-off, you get a fancy magenta line directly from one airport to another. After take-off, you receive the ATC instruction to "turn on course". In this instance, it *would* be appropriate to hit "direct-to" again, and fly direct from your current location. If you don't, and try to veer back over to your original magenta line, you may be doing something that ATC doesn't expect, especially if it's a fairly significant correction.
Click to expand...

Yes and no. While I agree this is an acceptable use of re-directing, I don't agree that intercepting your original course is a problem as long as the intercept angle is reasonable. It's not like we all got our E6Bs and plotters out when this happened before GPS. More generally, one re-direct per leg is usually okay.

I understand where OP is coming from. It was always weird that GPS makers invented a new term for something we already had a name for. And worse is the new name doesn't completely make sense.
 
dmspilot said:
It was always weird that GPS makers invented a new term for something we already had a name for. And worse is the new name doesn't completely make sense.
Click to expand...

I guess the full name should be "direct [from THIS SPECIFIC LOCATION] to [enter destination]"

edit: Actually, that still could be ambiguous. I like the way Hang said it:

direct
Hang 4 said:
from where you are when you press the button
Click to expand...
to
Hang 4 said:
the waypoint
Click to expand...
 
Last edited:
DCR said:
Then again this is the "training" forum, and I do appreciate the technique tips in this case.
Click to expand...
Yeah, but you can get a lot of tips that sound like one size fits all when it's actually more situational-dependent. So, for example, you got a pretty strict "don't recalculate." Then, @AvNavCom gave you excellent example of where you would recalculate.
AvNavCom said:
Agreed, but with a caveat. Let's say you're flying direct from a controlled airport (let's say a reasonably busy Class C for argument) to another airport.
Click to expand...
I can picture that one where you get a vector away from your course to keep you out of the path of departing or arriving traffic. Then you get a "resume own navigation" and instead of tapping the D→ button to your next waypoint, you turn back into the path they were trying to keep you out of.
 
DCR said:
Gotchya - so if I've gone off course I need to re-verify my new course is safe / legal.

I thought for some reason Hang was saying the GPS checked my first DTO for obstacles.
Click to expand...
This is where having a paper chart is nice. Lay it out on a table, draw a straight line from where you are (origin airport) to where you are going (destination airport). Check for obstacles, airspace, terrain, elevation, whatever along that line. If you select Direct To in your GPS on the ground at the hold short line or run up area, you’ll pretty much get the same line in magenta (your pencil line will be from the middle of the airport and the magenta line will be from wherever you are at that moment). You’ll be slightly off that line after takeoff until you turn back on course. But if you are tooling along, fat, dumb, and happy and do Direct To again that line gets redrawn from your present position and it’s up to you to pay attention to how you decide to follow it.
 
midlifeflyer said:
I can picture that one where you get a vector away from your course to keep you out of the path of departing or arriving traffic. Then you get a "resume own navigation" and instead of tapping the D→ button to your next waypoint, you turn back into the path they were trying to keep you out of.
Click to expand...
The guys on the Opposing Bases podcast really drove this home to me. They would depart someone from the airport via vectors and then give them "on course", expecting that the aircraft would head for the next fix/airport direct from that position. In some cases, I guess people have made fairly significant left/right heading deviations from what ATC expected for the purposes of recapturing that original magenta line, sometimes to the point of infringing on approach/departure paths. I try to keep that in mind, although happily at HEF I usually get an "on course" immediately after take-off, so that's easy enough.
 
DCR said:
I guess the full name should be "direct [from THIS SPECIFIC LOCATION] to [enter destination]"
Click to expand...
I was actually referring to DTK, when they could have just called it CRS.
 
Also note that even in the absence of wind, except in certain degenerate cases the course MUST change. A straight line between two points doesn't have constant bearing to north along it's entire length.
 
midlifeflyer said:
Probably because someone though comparing a “Track” with a “Desired Track” was more intuitive than comparing a “Track” with a “Course.”
Click to expand...
And someone else foretold the ATC de facto standard verbiage, "What is your on-course heading?"
 
iamtheari said:
And someone else foretold the ATC de facto standard verbiage, "What is your on-course heading?"
Click to expand...
That one is so common it really should be in the 7110 or PCG. OTOH, other than "to where?" it's kinda just English if you don't over think it. Aside from that, I bet more people have trouble with figuring out what the heading is than understanding what is being asked.
 
A minor point -

Most modern GPSes that I've used (so, 430 onwards, I don't remember enough about using the GNC-300XL to talk about it any more, and I've barely used any of the KLN series), don't actually plot straight from present position to the destination when you do a direct, if you're moving (i.e. in the air). Rather, they plot what the direct course WILL be once you've completed the turn to that course. So, they account for turn radius, and as far as I know they calculate based on a standard rate turn. This is highly preferable, because otherwise every time you'd do a direct while flying, you'll already have flown through the course and have to come back to it.

At work I fly with the Collins Pro Line 21 FMS, and it has a feature of the "direct" that I really like, that I don't know if I've seen on the typical Garmin/Avidyne GPSes and G1000s, etc., although I haven't specifically tried it either. When you start entering a direct-to, but before pressing the Execute button, it plots the line to intercept as kind of a "draft" line, but keeps updating it as you fly. Once you press EXEC it then fixes it in place and it's what you turn to. I've used this to great advantage for things like deviating around weather (if displayed on the MFD) or making my way around a restricted area or something like that. Does anybody know if the Garmin/etc GPS units do something similar before you press the "enter" or "activate" buttons?
 
You must log in or register to reply here.
Back
Top