Filing Alternate airport on IFR flight plan when using WAAS – HELP!

[John777]

I was going through the AIM in Chapter 1 to study about the suitable RNAV equipments and WAAS to understand the alternate airport selection when flying IFR flight.

I have listed the questions as below, and I would appreciate your comments, references and interpretations on what is correct according to FAR/AIM.

Some explanations were really vague and there were grey areas where two or more information were overlapping each other.



1)So, our school is thankfully equipped with WAAS/GPS and hope it is TSO-C145, or 146 certified. Now, when filing an alternate aiport, what I understand from the text in the AIM is that, we can shoot both GPS or file based upon GPS approaches at both destination and alternate airport?

2) If not WAAS equipped or TSO-129, 196 certified, then alternate airport must have an available instrument approach procedure that does not require the use of GPS. For example, shooting GPS or substituting with DME or VOR?

Also, in this case, can we shoot GPS approach at destination and shoot conventional approach at alternate? is this what text means?

3) Under AIM1-2-3(d)(1) states that for flight planning purposes, TSO-C129, 196 equipped aircraft, may only file alternate based on a GPS based IAP at either the destination or the alternate airport.

Does this mean that we are not using the standard weather minimums 800-2, 600-2 at destination and it must be greater than minimums for published LNAV or circling MDA or LNAV/VNAV DA?

What does either destination or the alternate airport mean? Aren't we caring only filing alternate airport?

4) Under AIM1-2-3 (d)(3) states that this restriction does not apply to TSO-145, 146(my school). So, we can shoot both GPS approaches at both destination and alternate airports using just 800-2(GPS approaches are non precision?!) and whenever wx at destination is below 1-2-3 rule, just file the alternate anyway?

5) Under AIM1-1-18(d)(1)(b) , aircraft using TSO-C129 or 196 must have operational alternate means of navigation and active monitoring of alternate navigation(let us say VOR ro NDB) is not required if the GPS receiver uses RAIM monitoring.

From the information above, can I fly IFR XC with TSO-145 or 146 (WAAS) without monitoring alternate means of navigation and do not have to monitor VOR or ADF ?

6)In continuance from previous question, under AIM1-1-18(e)(2)(a), it states that GPS/WAAS receiver(TSO-145, 146 certified), though not required, operators should consider retaining backup navigation equipment in their aircraft to guard against potential outages. From the classic memory GRABCARD, we need to have equipment for radio navigation and communication, and if we are flying Victor airways with GPS/WAAS, can we still fly without the VOR receiver and DME?

 

[tsts4]

1. What it means is your destination and alternate don't have to have any approaches other than GPS to meet alternate filing requirements. However, you actually fly whatever approach makes sense to the approach minimums once you are in the air. Alternate filing is all about insuring you have planned for adequate fuel to account for conditions being worse that what you flight planned for.

2. Sort of. For alternate filing purposes, with a TSO-C129 box one of the airports must have something other than a GPS approach (eg ILS, LOC, VOR, or NDB and you have to be appropriately equipped). Again, once you are in the air you can shoot whatever approach either airport has to that approach's minimums--you are not locked into a specific approach.

3. Ok, so if you have a non-WAAS box and the 1-2-3 rule dictates you file an alternate, then one of the airports (doesn't matter which) must have something other than a GPS approach and the weather mins for that approach most be either 600-2 if it's precision or 800-2 is it's non-precision. For the GPS approach at the alternate, you have to flight plan expecting to fly either the LNAV or circling minima and apply the non-precision weather mins of 800-2. IOW, if the approach has vertical guidance mins (eg LPV) which are much lower than the LNAV mins you can't use those in your alternate selection although you can fly the lower mins when the time comes. The reason that it says "either" destination or alternate is again this is a flight planning drill-- with a non-WAAS box the FAA just wants to make sure you have anticipated not being able to land at your destination because the weather is worse than forecast and have the fuel load to shoot an approach go missed and divert. Once you are in the air ATC doesn't care what you filed as your alternate.

4. For alternate filing purposes, and only filing purposes, you'd use 800-2 for the alternate selection and flight plan with no better then the LNAV or circling minima. Again you would fly the actual minima the GPS allows which for an LPV approach, if available, could be as low as 200-1/2.

5. Yes. However, the actual ref that speaks to WAAS TSO-C145/6 enroute operation is para 1-1-18.e.2.(a)

6. Yes.

Please note that a given airport 's approaches might have different alternate minimums than the standard 600-2 or 800-2 or certain approaches can be NA for use as an alternate altogether. This all plays into the alternate selection process.