The IFR chart lightning bolt confusion

The IFR chart lightning bolt confusion

Postby Medtner » Sat Dec 16, 2017 11:55 am

Hi,

I'm a new PilotEdge-user (flying the Cessna N245LG around Palm Springs), and I'm working my way through the excellent VFR and IFR seminars by Keith Smith on PilotEdge's YouTube channel.
They are incredibly useful, and even though I fly mostly VFR it is useful to know what goes on in the airspaces around me.

I have one question that I haven't been able to resolve, and which hasn't been conclusively answered in the seminars:

What are the lightning bolts in IFR charts in general?
I've learned from the seminars that the bolt in the vertical profile on approach charts is telling us that this is the FoF and that this is the place to intercept the glideslope (and verify DME/secondary radial, as well as correct altitude reading on the altimeter). That much is very clear and useful.

Keith have said repeatedly in the seminars that he thinks the other lightning bolts, littered around sids/stars, and approach charts (excepting he vertical profile), are to signify that those points are not to scale. This doesn't quite make sense:
- The Approach charts are to scale - they include terrain and as such must be to scale. Otherwise the terrain is uselessly cluttering the chart.
- Approach charts also don't have a disclaimer about the scale.
- SIDS/STARS, however, seems to consistently have the disclaimer that they are not to scale. Why, after having that disclaimer have a special symbol for those points?

I tried to search for a chart legend that specifies this, but found nothing.

Writing this post to ask you about this question I looked up various charts to get my point through. Doing so I spotted a pattern, and have perhaps answered my own question:
I found that on SIDS/STARS the lightning bolts seem to be there to point the name and other info (coordinates (when not RNAV) and altitudes and such) to an intersecion. The bolt is there only when the info can't be put right next to the intersection because of lack of space on the chart.

Examples:

The TANDY FOUR arrival
http://155.178.201.160/d-tpp/1713/00236TANDY.PDF

Look at the SADDE intersection. No bolt needed - there is sufficient room to place the text right next to it.
Next, MERMA. Crowded chart - the need to put the text further out. You could argue that there would be room for it, but there charts have very consistent visuals: The name, coordinates, and other info has this general pattern (with exceptions):
Name................XXXXX
Coordinates.......xxxxxxxxx
Coordinates......xxxxxxxxxxx
Other info......XXXXXXXXXXXXXX

(disregard the dots - they are there only because the forum here doesn't recognize spaces)

This, I feel, necessitates moving the "box of info" out a little, and thus the lightning bolt is used. If they put the text closer some of it would have to be staggered to fit it all. It is all very consistent and clever. We take this for granted, but this attention to detail makes these charts readable, as opposed to useless.

Moving on:
TANDY has a bolt again for the same reasons.
PAROL does too.

However:
ALBAS doesn't need it - room enough.

And so forth. On the lower left the chart already says that it isn't to scale (although all these charts seem to try to be as scaled as possible for clarity, I guess).


The KAYOH SEVEN arrival:
http://155.178.201.160/d-tpp/1713/00236KAYOH.PDF

Consistently, the intersections are all pointed out with a lighning bolt. None have a single line - all are jagged. The exception is the BANDS intersection, which has room enough to put the name and coordinates right next to it. And again, the chart is marked "not to scale", although it is, broadly speaking.

Another, subtler, point is that if the lightning bolts were to signify "not to scale" they would have to be for a leg, not a point. A point cannot be to any scale, it just 'is'. The leg can however be pointed out as being out of scale. But all these relevant charts are "not to scale", and I can't se how for example BANDS intersection could be in any way "in scale" because of its lack of lighning bolt.

The same goes for approach charts. There is a consistent pattern that the more busy the chart is with intersections and lots of text-info, the more lightning bolts you will see. The RNAV charts are almost free of them - simply because they don't have to list coordinates and all kinds of other info. I looked through several RNAV-charts for LAX and found that they generally have room enough to put the name right next to the intersection/fix, but a few were cluttered enough to warrant a lightning bolt a place or two.

The symbol that Keith refers to, I'm confident is the one on the first plate of symbols, bottom left. These two "squiggles" are marking "distance not to scale".
https://www.flightsimbooks.com/flightsi ... Legend.php
This symbol is used on the infamous ILS or LOC RWY 19R for John Wayne in the very lectures I talked about, on the leg between POMONA VOR to SAGER INT (which was my point previously about a leg being not to scale, but a point can't be either/or):
http://training.pilotedge.net/object/io ... 68359.html

My conclusion is that the lightning bolts are simply pointers to the intersections on SIDS/STARS, and that they have nothing to do with scaling. Maybe they are jagged to not be visually confused with the many radials and legs?

This turned to a bit of a rant-ish sort of text, but it stems from attention to detail. The makers of these charts have done an inhumanly good job at being consistent and clear. It tickles my brain to read charts that are well put together.

Hope this is as useful to the readers as it was to me - I've answered my own question it seems.
Unless someone knows more? I'd be happy to be proven wrong - I'm in this for the learning.

Erik Aasland,
Nerding geek from Norway :-P
Medtner
 
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Location: Arendal, Norway. Home airports: ENCN and ENGK.

Re: The IFR chart lightning bolt confusion

Postby HRutila » Thu Dec 28, 2017 11:13 pm

A "lightning bolt," or "zig-zags" centered amid an airway or a route indicates that the airway or route is not drawn to scale. A lightning bolt on the profile view of an instrument approach procedure (IAP) indicates a precision final approach fix (PFAF). A lightning bolt in the plan view of a SID or STAR is simply directing the reader to the name of the waypoint, which has been displaced away from the actual depiction of the waypoint symbol for purposes of clarity.
Harold Rutila
COMM-MEL/CFII
HRutila
 
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Re: The IFR chart lightning bolt confusion

Postby BrianATL » Thu Apr 04, 2019 3:19 pm

I think it's best to refer to the 'not to scale' as a zig-zag (two parallel zig-zags), which is different from the lightning bolts. The plan view of the approach chart, the one Keith used for his IFR webinars on the approach phase, KSNA, has 'lightning bolts' and a 'zig-zag. The zig-zag at Pomona (which by the way is no longer depicted on the chart) is a 'not to scale'. The lightning bolts on the plan view identifying the fixes along the approach are the same as for the SID or STAR, which is directing the reader to the name of the waypoint which has been displaced, as you said in your post. Keith said that all were 'not to scale' but that is incorrect, because the actual approach on the plan view IS to scale. And of course the lightning bolt on the profile view is the FAF as you said also.
BrianATL
 
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