Proceeding direct to a random intersection as /U

C

ClearedToTakeoff

Well-Known Member
I did all my instrument training as /G and could always just go direct to an intersection. Now as a CFII I have to teach in /U and /A all the time. How, other than triangulating position and estimating rough heading to the intersection, can you proceed to a random made up intersection?

I told my student to hold on the R-190 off one VOR south left turns based off an intersection off of R-100 from another VOR. Completely made up spot in space. We were northeast of the fix so a teardrop would be recommended. But by the time we got to the fix, a parallel was best.

Basically he flew to the R-190 and tracked southbound on that until the intersection than he proceeded to due the teardrop entry procedures. So how could he go direct to the intersection without intercepting one radial and tracking until the intersection?
 
Ahhhhh....

The old fix-to-fix!

ClearedToTakeoff said:
I did all my instrument training as /G and could always just go direct to an intersection. Now as a CFII I have to teach in /U and /A all the time. How, other than triangulating position and estimating rough heading to the intersection, can you proceed to a random made up intersection?
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That's the basics right there of how to do it. It's easy with an RMI and even easier with an HSI/RMI combo, but can also be pretty easily done with a standard HSI or OBS. The big thing is being able to visualize, in a plan view, where you are and where you want to go, then figure a rough initial heading from there. To refine that heading, you need to visualize the same "plan view" (God's eye view) of your position relative to the radial/distance you want to go to, versus where you are. Draw a line between where you are and where you want to go, then superimpose a parallel line towards the center of the HSI and read the heading it gives you.

For example. You're on the R-180 at 80 DME of a VOR, and want to go to the R-090 for 40 DME of the same VOR (draw it out). The rough heading is going to be something Northeastbound (say, 045, for instance). Looking at your HSI, set in the desired radial (090). Place yourself visually on the 180 (18) on the HSI and at the edge of the instrument....thus arbitrarily representing 80 DME. Then look at the CDI (set at 090) and pick a point halfway between the center of the instrument and the edge (nominally representing 40 DME, or halfway to the case that represents 80 DME). Draw an imaginary line between the two. Move that line towards the center of the instrument, and see where that imaginary line falls on a northeast heading to the new fix. It should fall on roughly 030 as your no-wind heading to from the 180/80 to the 090/40. From here, it's +/- heading estimations in order to account for any wind. Keep refining until you get to the new fix.

With an RMI, it's much easier because much of the work is already done for you. Since the RMI always points at the station (like an NMD), it's easier to visualize, and you just pick up a heading between the head of the bearing pointer and the radial where the desired fix is. Again, this is all for going from one fix to another of the same NAVAID. Going from one NAVAID fix to another fix on a different NAVAID will be a little more challenging, but the basics apply.
 
Ahhhhh...

The old fix-to-fix!

Before it gets started, here't the battle lines.

Yes! Mike describes a way to do it. Another is to simple pick a logical intercept where the DME gets smaller and smaller (a quasi arc). A third is to dead-reckon from where you are (you do have that E6b that you learned to use with one hand tied behind for back, don't you? ;)).

NO!Direct means direct. Point to point. Any way that doesn't use a navigational fix or waypoint and a method that takes you there as the destination is not going to meet the tolerance of what is considered "direct."

It's about traffic control (it might be about terrain), so if you don't have the equipment to dial in the destination and navigate that way, tell ATC and ask for a vector. Since going direct generally gets you a shortcut and ATC less work, a (radar) vector to your destination can take care of both. It can be as simple as

ATC: Proceed direct Denver
Pilot: Unable direct. Can you give me a vector?
ATC: Fly heading 232 direct Denver.

Got that handgeld GPS? You might even be abel to suggest the heading or track yourself.
 
Though I try to avoid it, you can ask for an initial steer if they send you to some random intersection that you are unfamiliar with and you need to dig it up in the charts or ask for clarification.
 
Nothing says you can't use a GPS, even a handheld non-IFR one. Mine goes for $10 on ebay...

The "old-fashioned" way would be to mark your position on a chart (noting the VOR intersections you are on), draw a line to the fix, then use your trusty plotter to figure the course. Mark a few waypoints, time to them, and adjust course as necessary.

With a VOR-only aircraft, this would be the primary method. You can use GPS to your heart's content to "supplement" the VORs.

This is why we had navigators before the introduction of Area Navigation/INS/GPS/RNAV.

BTW, if ATC gives you direct, they have you on radar. It isn't much work for them to give you a heading too. They just assume everyone has some type of area navigation these days though.
 
MidlifeFlyer said:
NO!Direct means direct. Point to point. Any way that doesn't use a navigational fix or waypoint and a method that takes you there as the destination is not going to meet the tolerance of what is considered "direct."
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And what is that tolerance? I would feel bad to have wasted all that time learing how to do a fix to fix and required to arrive at said fix within 2 or 3 miles on checkrides in the AF many years ago if it was something I would not ever be allowed to use...
 
Within 2 or 3 miles? That's pretty rough......unless we are talking SR-71 or something :p
 
///AMG said:
Within 2 or 3 miles? That's pretty rough......unless we are talking SR-71 or something :p
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:yeahthat:

Anyway, around here, any time you inquire about getting a vector back on course as cleared, the answer is always "cleared direct <insert airport>."
 
It's not rough at all when you consider the amount of distance you would be covering on an average fix to fix and compare to something like your average airway width. Still well within reason. Remember some folks still fly without that nifty little GPS, how accurate do you think VORs really are when you're flying them? Answer: not terribly much so at longer distances, especially when they're scalloping.
 
Rocketman99 said:
It's not rough at all when you consider the amount of distance you would be covering on an average fix to fix and compare to something like your average airway width. Still well within reason. Remember some folks still fly without that nifty little GPS, how accurate do you think VORs really are when you're flying them? Answer: not terribly much so at longer distances, especially when they're scalloping.
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I've only done TACAN PTP's (so some difference in terms of accuracy), but generally anything more than about 0.5-1.0 NM off has been considered sloppy on checkrides I've flown. We don't use GPS as primary nav anyway (at least legally) so intersections and PTP's are all old school method.
 
///AMG said:
I've only done TACAN PTP's (so some difference in terms of accuracy), but generally anything more than about 0.5-1.0 NM off has been considered sloppy on checkrides I've flown. We don't use GPS as primary nav anyway (at least legally) so intersections and PTP's are all old school method.
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PTPs rule. :)

They teaching the "pencil method" in the USN with the RMI?
 
MikeD said:
PTPs rule. :)

They teaching the "pencil method" in the USN with the RMI?
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We did pen/pencil method on the RMI in T-34's, and I still use pen method off the MFD HSI display in the T-45. Works great, even at 3 times the speed and altitude :) We have a really **itty GPS database with almost no intersections, so unless you want to manually input waypoint offsets (and risk fat fingering them or forgetting the mag var) everything has to be done the old fashioned way. You can get a pretty good estimate quickly using GPS plan line, but to gnat's ass it, we really need the trusty skilcraft and a TACAN.
 
B767Driver said:
The military teaches point to point navigation but it is not suitable for navigation in the NAS.
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Does the AIM say this anywhere?

There are plenty of intersection fixes used for missed approaches, with nothing but a heading given on the IAP to get there (no radial to follow). How is flying direct to a fix on an IAP, off-airway, any different? I'm sure we can all think of some examples of why you might need to figure a heading from somewhere other than the MAP. I guess my point is, why would these procedures be charted if it were not suitable for them to be performed?

Yes, most of these are probably VOR or TACAN approaches primarily used by the military, but they exist at civil airports too.
 
drunkenbeagle said:
Does the AIM say this anywhere?

There are plenty of intersection fixes used for missed approaches, with nothing but a heading given on the IAP to get there (no radial to follow). How is flying direct to a fix on an IAP, off-airway, any different? I'm sure we can all think of some examples of why you might need to figure a heading from somewhere other than the MAP. I guess my point is, why would these procedures be charted if it were not suitable for them to be performed?

Yes, most of these are probably VOR or TACAN approaches primarily used by the military, but they exist at civil airports too.
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There's a number of IAPs that have a DR leg associated with them, although these are usually very short mileage-wise in comparison to a classic fix-to-fix.

However, for accuracy purposes, I can get a fix-to-fix usually down to about 1 mile deviation without too much zigzagging across the sky and hit the fix dead on, merely due to doing a good number of them. Just something that takes practice, esp managing the wind corrections, and is something more used by military than by civilian.

The method I posted in Post #2 assumes no other crutches available. If there's ATC vector ability via radar, defintitely use it; obviously if you have some sort of area navigation then there'd be no true need for a "classic" FTF. If you're on your own with nothing else to help you, make it happen! :)
 
drunkenbeagle said:
Does the AIM say this anywhere?

There are plenty of intersection fixes used for missed approaches, with nothing but a heading given on the IAP to get there (no radial to follow). How is flying direct to a fix on an IAP, off-airway, any different? I'm sure we can all think of some examples of why you might need to figure a heading from somewhere other than the MAP. I guess my point is, why would these procedures be charted if it were not suitable for them to be performed?

.
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I believe these examples fit the definition of unpublished rnav routes found in the AIM. There may also be restrictions concerning Class 1 Navigation...but am not certain about that.
 
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