GPS for IFR enroute

Murdoughnut

Murdoughnut

Well sized member
Ok, so I'm trying to get clarification on some things before my IR checkride...

My 172 has a Garmin 300xl which is approved for IFR use (equip code G). I know that this qualifies me to fly GPS and GPS overlay approaches, but what does it allow me to do enroute?

I guess what I'm asking is, do I still have to follow airways that are supported by VORs as a backup, or could I say, file a route that includes direct nav between intersections not on the same airway?

Also, if I'm being vectored, ATC can send me direct to a fix or intersection, correct? I mean, I dont' need to be able to get there via traditional nav means - I can just hit direct-to and follow the GPS there, right?

Thanks for the help - I started learning the IR stuff in a non-IFR equipped a/c, and I'm trying to fill in the gaps.
 
Re: IFR for enroute

Murdoughnut said:
My 172 has a Garmin 300xl which is approved for IFR use (equip code G). I know that this qualifies me to fly GPS and GPS overlay approaches, but what does it allow me to do enroute?
Click to expand...

Everything!

I guess what I'm asking is, do I still have to follow airways that are supported by VORs as a backup, or could I say, file a route that includes direct nav between intersections not on the same airway?
Click to expand...

You could go direct between two airports! If you file this at busy places you might not get it but I've never been denied direct to. You can file any route and with any interesctions you want. You could even do this before you had a GPS. Oh and VORs as a backup is only for flight planning and then you use them if your GPS fails.

Also, if I'm being vectored, ATC can send me direct to a fix or intersection, correct? I mean, I dont' need to be able to get there via traditional nav means - I can just hit direct-to and follow the GPS there, right?
Click to expand...

Yes you can just put in the Fix and press direct to. You could still use VORs and a chart to back everything up if you had a NAV2 if you wanted to but you don't have to or need to.
 
Re: IFR for enroute

Murdoughnut said:
Also, if I'm being vectored, ATC can send me direct to a fix or intersection, correct? I mean, I dont' need to be able to get there via traditional nav means - I can just hit direct-to and follow the GPS there, right?
Click to expand...

oktex88 said:
Yes you can just put in the Fix and press direct to. You should still use VORs and a chart to back everything up if you had a NAV2 just in case the GPS, either the card, reciever or box, fails.
Click to expand...

:)
 
Re: IFR for enroute

For your checkride, you will most likely need to do VOR navigation, and holds, but use the GPS to the max extent possible in conjunction with both.
 
Re: IFR for enroute

Thanks guys! Just wanted to make sure I had my bases covered when the oral questions start rolling in. :)
 
Re: IFR for enroute

If you haven't already, review GPS operation basics, RAIM, and RNP requirements. It's a required oral evaluation on your instrument checkride. The AIM and instrument flying handbook are two good resources for this.
 
Re: IFR for enroute

Read AIM Chapter 1-1-19-d-1-b:

(b) Aircraft using GPS navigation equipment under IFR must be equipped with an approved and operational alternate means of navigation appropriate to the flight. Active monitoring of alternative navigation equipment is not required if the GPS receiver uses RAIM for integrity monitoring. Active monitoring of an alternate means of navigation is required when the RAIM capability of the GPS equipment is lost.

2. GPS domestic en route and terminal IFR operations can be conducted as soon as proper avionics systems are installed, provided all general requirements are met. The avionics necessary to receive all of the ground-based facilities appropriate for the route to the destination airport and any required alternate airport must be installed and operational. Ground-based facilities necessary for these routes must also be operational.

Basically go ahead and use it for whatever you want. If you need to do an approach, must use the required instrument for that approach, not just a GPS overlay. Also, if traveling along airways or off route, must have a secondary means available to navigate that route or divert. In theory, dead reckoning is a valid method, so keep using those nav logs!
 
Re: IFR for enroute

Also, you might want to be aware of the difference in alternate requirements between GPS units certified under TSO-C129A and WAAS units under TSO-C146A (or TSO-C145A,).

Basically, you need to have an alternate means of navigation to complete the flight with the non-WAAS GPS. Not so for WAAS.

Here's a few links for your enjoyment:

AIM CH.1 (near the end of the chapter explains this and more!!) -- http://www.faa.gov/airports_airtraffic/air_traffic/publications/ATpubs/AIM/Chap1/aim0101.html

http://rgl.faa.gov/Regulatory_and_G...0cd9c6acf8ba186256dc700717e0f/$FILE/C129a.pdf

http://rgl.faa.gov/Regulatory_and_G...399d32ee5750a86256dad00643d48/$FILE/C146a.pdf

-A.S.
 
Re: IFR for enroute

oktex88 said:
Yes you can just put in the Fix and press direct to. You could still use VORs and a chart to back everything up if you had a NAV2 if you wanted to but you don't have to or need to.
Click to expand...

Be careful when doing this, it is NOT the same as flying an airway. If you're assigned an airway, then that's what you need to fly. If you're going to do this in lieu of tuning in a VOR, make sure that the GPS unit has the ability to select a specific course to/from the direct to fix. I have had to do this before when a VORTAC (not my radio, the VORTAC itself) failed while I was tracking a radial. I had my instructor with me at the time, and he told me to make sure that the GPS was providing the same course as if I were tracking the VOR itself. Garmin units have the OBS function on them that allows you to do just that.

Of course, one way to get around that issue is to program your flight plan into the GPS, which should put you on the same courses as if you were flying VOR to VOR using radio navigation.
 
Re: IFR for enroute

I just realized that the title of this thread was supposed to be GPS for IFR enroute ... my bad.
 
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