IFR Chart question
 

So my roommate got asked a question by his instructor. He didn't know the answer so he's supposed to look it up. I figure APCforums had a wealth of knowledge we can use.

Q:
On IFR en-route charts there are mileage break points. Sometimes instead of these there are jagged lines. The kinds that are used on graphs so the markers don't have to start at zero. What are these points called and what is their purpose?

Without seeing it, I believe that you're speaking of a "Change over Point" where you switch from one navaid to another while enroute between VORs on the airway.

The introduction section of the Jepp Charts, or the legend on the actual NOS (or whatever they call them now) should have the answer.

I'd have to agree, if it looks like an _|-, except the mid-one is supposed to be up top, that's a changeover point.

Unusable route?

http://www.cgaux.info/g_pcx/missions...fr_symbols.pdf

Page 4 left side.

The change over symbol is on page 5 of slice's link. Left hand side, 3rd down.

Not the break point
 

we know what the break-points are. My roommate got asked about something that we assume works similarly to a break-point. It looks like /\/\/ and can be found along V-airways.

I vote unuseable route. I'm not sure why they would chart an unuseable route in the first place, but that's just me. If someone can point to one somewhere, maybe seeing it in context will help.

Unusable... not guaranteed radio navigation reception? Are you supposed to just fly the heading until you pick up the VOR again?

It's definitely an unusable route segment. It's defined on the gov't charts...dunno if Jepps has it, never used theirs. Not quite sure of the meaning though, never given any thought to that since I got my IR...and honestly, never seen it since. Doesn't really sound logical...why print a segment that isn't usable.

Now, most likely if u got : /\/\/\/\/\/\/\ (unusable route) there should be somewhere near something like this: o-o-o-o-o-o-o-o-o-o-o

Basically u will get an alternate routing, depicted by the symbol shown on my previous post. For example, check Dupont (DQO) VOR just south of philly.

They are printed because they are just "segments" of a specific V route that r out of service.....maybe tempo. maybe for good....maybe just MX on the station...or conflicting signals.....who knows!:eek:

thank you
 

thanks all for responding.

If it's two jagged edges on the break in the line, it does not mean that the airway is "unuseable" - if this were so, they'd remove! What it means is that
there is a gap in VOR (or other radionavigation aid) reception- at one point, you'll lose the VOR you're flying away from without having picked up the one you're flying to.

What do you do? Stay above the MEA, not the MRA or OROCA or MOROCA and maintain the heading which was keeping you on course until you pick up positive navigational coverage (meaning the needle is alive and indicating correctly) from the next navaid.

Try this PDF.

http://aviationfanatics.com/images/s...fr_symbols.pdf

In fact, the website has several good PDFs regarding IFR and VFR charts.

http://aviationfanatics.com/content/view/22/1/