Alternate with GPS

[schwed]

I've been trying to understand how to legally use a GPS approach at an alternate airport. I understand I can't use a GPS approach both on my filed and alternate airports and that the GPS approach must have WAAS / RAIM monitoring capability. I fly a WAAS equipped cirrus so the equipment isn't an issue.
The part I can't figure out is what it means when it says that the approach must be monitored. Does that mean it must be a towered airport?

So here's a RW flight where this became an issue:
I was flying IMC from KLOM (non-towered) to KLNS (ILS approach) and I was required to file an alternate. I thought of using KLOM as my alternate where I could do a GPS-LPV approach. I ended up using a nearby towered airport with an ILS approach as the alternate since I wasn't sure I could legally file for KLOM.

Any input on this?


Thanks!

Dan

[Kyle.Sanders]

I understand I can't use a GPS approach both on my filed and alternate airports

Where does it say you can't?

[schwed]

From the FAA Policy change effective 4/04/2013. Not sure if there's something newer than this (I've attahced the file as a PDF):

Policy Change for GPS Users
The current alternate airport planning policy allows Technical Standard
Order (TSO)-C129() and TSO-C196() equipped users (GPS users) to
plan for GPS-based instrument approach procedures (IAP) at their
destination but not at their alternate airport.
The FAA has updated this policy to allow an option to flight plan for use
of a GPS-based IAP at either the destination or the alternate airport, but
not at both locations. At the alternate airport, pilots may plan for
applicable alternate airport weather minimums using:
1. Lateral navigation (LNAV) or circling minimum descent altitude
(MDA);
2. LNAV/vertical navigation (LNAV/VNAV) decision altitude (DA) if
equipped with and using approved barometric vertical navigation (baro-
VNAV);
3. RNP 0.3 DA on an RNAV (RNP) IAP if specifically authorized with
approved baro-VNAV equipment.
To take advantage of this option, GPS users must:
1. have navigation systems with fault detection and exclusion (FDE)
capability.
2. perform a preflight Receiver Autonomous Integrity Monitoring
(RAIM) prediction for the approach integrity at the airport where the
GPS-based 3. have prop IeArP k wnoilwl bleed fgloew ann.d any required training and/or approval to
conduct a GPS-based IAP.
4. ensure that the conventional approach (at destination or alternate)
can be flown without reliance on GPS.
The FAA based this policy change on research that demonstrated a
satisfactorily low probability of a missed approach or diversion and an
even more remote probability concerning loss of navigation

[HRutila]

The newest information regarding the policy change has been incorporated into the AIM. I have quoted the relevant sections below. The key factor is whether your GPS has WAAS capabilities or not.

For non-WAAS GPS receivers, this is the pertinent section.

1-1-17. Global Positioning System (GPS)
...
5. GPS Instrument Approach Procedures
...
(c) For flight planning purposes, TSO-C129() and TSO-C196()−equipped users (GPS users) whose navigation systems have fault detection and exclusion (FDE) capability, who perform a preflight RAIM prediction for the approach integrity at the airport where the RNAV (GPS) approach will be flown, and have proper knowledge and any required training and/or approval to conduct a GPS-based IAP, may file based on a GPS−based IAP at either the destination or the alternate airport, but not at both locations. At the alternate airport, pilots may plan for:

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

(2) LNAV/vertical navigation (LNAV/VNAV) DA, if equipped with and using approved barometric vertical navigation (baro-VNAV) equipment;

(3) RNP 0.3 DA on an RNAV (RNP) IAP, if they are specifically authorized users using approved baro-VNAV equipment and the pilot has verified required navigation performance (RNP) availability through an approved prediction program.

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

For WAAS-capable GPS receivers, the following section applies:

1-1-18. Wide Area Augmentation Systems (WAAS)
...
c. General Requirements

1. WAAS avionics must be certified in accordance with Technical Standard Order (TSO) TSO−C145(), Airborne Navigation Sensors Using the (GPS) Augmented by the Wide Area Augmentation System (WAAS); or TSO−C146(), Stand−Alone Airborne Navigation Equipment Using the Global Positioning System (GPS) Augmented by the Wide Area Augmentation System (WAAS), and installed in accordance with Advisory Circular (AC) 20−138(), Airworthiness Approval of Positioning and Navigation Systems.
...
9. Unlike TSO−C129 avionics, which were certified as a supplement to other means of navigation, WAAS avionics are evaluated without reliance on other navigation systems. As such, installation of WAAS avionics does not require the
aircraft to have other equipment appropriate to the route to be flown. (See paragraph 1−1−17d for more information on equipment requirements.)

(a) 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 non−precision weather requirements must be used for planning. Upon arrival at an alternate, when the WAAS navigation system indicates that LNAV/VNAV or LPV service is available, then vertical guidance may be used to complete the approach using the displayed level of service. The FAA has begun removing the NA (Alternate Minimums Not Authorized) symbol from select RNAV (GPS) and GPS approach procedures so they may be used by approach approved WAAS receivers at alternate airports. Some approach procedures will still require the NA for other reasons, such as no weather reporting, so it cannot be removed from all procedures. Since every procedure must be individually evaluated, removal of the NA from RNAV (GPS) and GPS procedures will take some time.

NOTE−
Properly trained and approved, as required, TSO-C145() and TSO-C146() equipped users (WAAS users) with and using approved baro-VNAV equipment may plan for LNAV/VNAV DA at an alternate airport. Specifically authorized WAAS users with and using approved baro-VNAV equipment may also plan for RNP 0.3 DA at the alternate airport as long as the pilot has verified RNP availability through an approved prediction program.

More information about WAAS is available in the same section under a. General. Its benefits in terms of alternate airport selection are often not even mentioned when people talk about upgrading to WAAS, but this is certainly a great benefit.

Hat tip to my colleagues at the AOPA Forums for providing some source material for this answer. It is not exactly the easiest stuff to find.

[HRutila]

The part I can't figure out is what it means when it says that the approach must be monitored. Does that mean it must be a towered airport?

The term "monitoring" refers to an autonomous process where navaid equipment sends an error alert to someone, usually located at an ATC facility, if there is something wrong with the navaid. The one I've witnessed sounded a very distinctive chirping noise.

FAA Order 8260.19 Flight Procedures and Airspace

2-4-5. Monitoring of navigation facilities.

a. Monitors. It is FAA policy to provide a monitoring system for all electronic navigation facilities used in support of instrument flight procedures. Internal monitoring is provided at the facility through the use of executive monitoring equipment that causes a facility shutdown when performance deteriorates below established tolerances. A remote status indicator may also be provided through the use of a signal-sampling receiver, microwave link, or telephone circuit. VOR, VORTAC, and ILS facilities as well as new NDBs and marker beacons installed by the FAA, are provided with an internal monitoring feature. Older FAA NDBs and some non-Federal NDBs do not have the internal feature and monitoring is accomplished by other means.

b. Monitoring categories. Navigational facilities are classified in accordance with the manner in which they are monitored.

(1) Category 1. Internal monitoring plus a status indicator installed at control point.
Reverts to a temporary category 3 status when the control point is unmanned/monitoring not
available.

(2) Category 2. Internal monitoring with status indicator at control point inoperative, but pilot reports indicate the facility is operating normally. This is a temporary situation that requires no procedural action.

(3) Category 3. Internal monitoring only.

(4) Category 4. Internal monitor not installed. Remote status indicator provided at control point. This category is applicable only to nondirectional beacons.

Interestingly, there is another order which suggests some monitoring may be done by sheriffs' departments. I am not aware of any areas of the country where this is occurring, but it suggests not all monitoring is done by ATC.

Order 7900.2C Reporting of Navigational Aids...to the National Flight Data Center

C. Form Sections

I. Submissions
...

• (14) Remotely Monitored. Indicate if the ILS and associated components are remotely monitored and if so, select the name of the monitoring facility (e.g., ATCT, MOCC, Airport Operations, sheriff’s department, etc.). Enter the hours and days of operation for the ILS if remote monitoring is not full time. If remotely monitored for 24 hours, enter 24 in this field.

When a navaid's monitoring is not available, a NOTAM such as "RWY 10 ILS UNMON" will appear in the NOTAMs for the affected airport. If there is an ATIS available at the airport, the ATIS should also read this NOTAM. This happened to be the case at Lafayette (LAF), where I fly, late this past week.

[schwed]

HRutila, Thanks! This is exactly what I was looking for!