GPS Alternates

Chief Captain

Chief Captain

Well-Known Member
Seeking some clarification here guys. Under the FAA's new policy disseminated via general NOTAM, we can plan on a GPS approach at either the destination OR the alternate airport, but not both. It goes on to further say that WAAS users that have baro-VNAV can plan on using VNAV minimums at the alternate.

What if I have WAAS, but no baro-VNAV? Am I correct in thinking that my alternate must be based on LNAV mins?

Do I need WAAS to take advantage of the new rule, or does it apply to non-WAAS units as well?

Thanks
 
Chief Captain said:
Seeking some clarification here guys. Under the FAA's new policy disseminated via general NOTAM, we can plan on a GPS approach at either the destination OR the alternate airport, but not both. It goes on to further say that WAAS users that have baro-VNAV can plan on using VNAV minimums at the alternate.

What if I have WAAS, but no baro-VNAV? Am I correct in thinking that my alternate must be based on LNAV mins?

Do I need WAAS to take advantage of the new rule, or does it apply to non-WAAS units as well?

Thanks
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135? If so should be in your ops specs.
 
My understanding is (and this applies to 135 and 121 as well... once they update their opspecs) is that you can file to an airport with ONLY a GPS approach as long as you have an alternate that has a ground based approach. OR you can list an alternate that ONLY has a GPS approach as long as your destination airport has a land based approach.

Additionally, if you a baro compensated VNAV and WAAS you can use the VNAV mins for listing the alternate.

So, I'd guess if you don't have the baro compensation in place then you have to use the LNAV mins when checking the alternate.
 
BobDDuck said:
My understanding is (and this applies to 135 and 121 as well... once they update their opspecs) is that you can file to an airport with ONLY a GPS approach as long as you have an alternate that has a ground based approach. OR you can list an alternate that ONLY has a GPS approach as long as your destination airport has a land based approach.

Additionally, if you a baro compensated VNAV and WAAS you can use the VNAV mins for listing the alternate.

So, I'd guess if you don't have the baro compensation in place then you have to use the LNAV mins when checking the alternate.
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That doesn't sound quite right from what I remember but IFR 135 ops specs are completely new to me so I'll have to double check when I get to the office tomorrow. I want to say C384 is the relevant one?
 
I don't think so. C384 is what allows you to shoot an RNAV (RNP) vs. just an RNAV (GPS) using "curved" route segments.
 
Under part 91 if you have WAAS you can plan a destination with only a GPS approach, and an alternate with only a GPS approach, but your alternate has to meet non-precision weather minima (800 and 2) in order to be filed. No WAAS = your alternate must have a different type of approach OR have weather that allows for a descent from the MDA in visual conditions.
 
BobDDuck said:
I don't think so. C384 is what allows you to shoot an RNAV (RNP) vs. just an RNAV (GPS) using "curved" route segments.
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Looks like you're right. I told you this stuff was all new to me. I'll look at what we have at work tomorrow and get back.
 
thevideographer said:
Under part 91 if you have WAAS you can plan a destination with only a GPS approach, and an alternate with only a GPS approach, but your alternate has to meet non-precision weather minima (800 and 2) in order to be filed. No WAAS = your alternate must have a different type of approach OR have weather that allows for a descent from the MDA in visual conditions.
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That sounds in line with what we have in our ops specs for dual C145 WAAS aircraft.
 
thevideographer said:
Under part 91 if you have WAAS you can plan a destination with only a GPS approach, and an alternate with only a GPS approach, but your alternate has to meet non-precision weather minima (800 and 2) in order to be filed. No WAAS = your alternate must have a different type of approach OR have weather that allows for a descent from the MDA in visual conditions.
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I remember hearing that before? Do you have a reference for that?
 
OK, so I've looked into it a bit more. Here's what 1-1-18 (g)(1) says


1. For flight planning purposes said:
GPS based IAP at either the destination or the alternate airport, but not at both locations.[/B] At the alternate airport, pilots may plan for applicable alternate airport weather minimums using:

(a)  Lateral navigation (LNAV) or circling minimum descent altitude (MDA);

.........

2. If the above conditions cannot be met, any required alternate airport must have an approved instrument approach procedure other than GPS that is anticipated to be operational and available at the estimated time of arrival, and which the aircraft is equipped to fly.
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1-1-19(c)(a) says

[B said:
(a) [/B]Pilots with WAAS receivers may flight plan to use any instrument approach procedure authorized for use with their WAAS avionics as the planned approach at a required alternate, with the following restrictions. When using WAAS at an alternate airport, flight planning must be based on flying the RNAV (GPS) LNAV or circling minima line, or minima on a GPS approach procedure, or conventional approach procedure with “or GPS” in the title. Code of Federal Regulation (CFR) Part 91 nonprecision weather requirements must be used for planning.
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The way I read it, chapter 19 doesn't say we can plan for 2 GPS approaches if we have WAAS. Instead it's just reiterating that at the alternate airport, we can only plan based on LNAV minima.

Here's may understanding. Please correct me if I'm wrong.

1. You can plan for a GPS app at the destination OR the alternate, not both.

2. If the alternate airport has the GPS approach, we must plan using LNAV minima.


What say you all?
 
Chief Captain said:
1. You can plan for a GPS app at the destination OR the alternate, not both.

2. If the alternate airport has the GPS approach, we must plan using LNAV minima.


What say you all?
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Note that 1-1-18 has this stipulation: "This restriction does not apply to RNAV systems using TSO-C145/-C146 WAAS equipment. For further WAAS guidance see AIM 1-1-19."


Therefore, your first assertion isn't quite correct. WAAS equipment provides two additional ranging sources in addition to augmentation... thanks to this, the FAA has removed the requirement to have a conventional approach available at an alternate.
 
Hmmm. I see. 1-2-3 (d) has the same quote. I wish they'd just come out and say what they want instead of having us reference three different sections to try and piece it together.
 
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