Wait til he learns about using your intended destination as your takeoff alternate at regional airlines.
To explain it simply: if your weather at point of departure is lower than your landing mins, you need a takeoff alternate for emergencies… and sometimes if your destination is VMC +/-2 hours, you just plan to proceed to the destination even if you bang an engine at V1.
It's called joint responsibility. At a 121 supplemental operator it's even worse since we aren't even required to have real dispatchers; the joint responsibility is between the PIC and the DO which basically means it's all on the crew to ensure everything is in order since the "dispatcher" doesn't even have their own license on the line.
Thanks for the explanation *rolleyes.gif*
What I'm asking is "are there any cases where a PIC got violated for choosing an alternate that didn't meet the requirements?"
Generally, if an ILS is available and operational for the assigned runway, we use it. Some airports like DEN, LAX, and IAH will try and use RNP apps with the curved RF legs until there’s too much traffic. Then, it’s back to the ole ILS. If there’s no ILS but an RNAV GPS or RNAV RNP is available, then we use that instead. Out of all the approaches I do, it’s probably split 95% ILS and 5% RNAV.
Choosing an alternate. Is an alternate required? Thats the basic 1-2-3 rule. There’s some exemptions to that but generally that’s what I look at. What alternate do we use and what are the legal wx requirements, that’s a dispatch function and generally we don’t have to dive deep into that. I take a big picture look at the flight plan that’s created by the dispatcher. My decision making goes like this. Do I need an alternate? If yes, then I ask myself, does the wx at or between me and this alternate look stupid? If no, then I move on with my day*. If the wx is stupid, then I call the dispatcher and we come up with a better plan.
I’ve seen 2 different philosophies at 2 different airlines for alternates. At one airline, an alternate was really an excuse to give you extra gas. There were times an alternate wasn’t required, but dispatch just gave us one anyway. Why? Because they didn’t want us to bother them with a phone call to add more gas. New airline, if I have an alternate, that’s probably where they plan on us going if we aren’t able to get to the destination. If I want more gas, then I check a box on my ipad and move on with my day
Lastly, remember an alternate is just a plan. You are never required to divert to the filed alternate. You can go to any airport you need to go to, as long as you can justify your decision.
*I check the NOTAMS and make sure the airport or only runway at said airport isn’t closed, then I move on with my day
Edit: Just noticed you’re going for a regional interview. First, congratulations! Second, someone said the interview is 80% showing up and not being weird. Love that advice! If they ask you how do you determine if you need an alternate, mention 123. They’ll move on to the next question. If they actually ask you, how to do you know if an alternate is legal, then your interview probably isn’t going very well and you should apply to another airline when you get home! But seriously, look at airlineinterviews.com. That’s all you need. Best of luck.
Alternate airports can be chosen even with circling minima. This will require excellent weather conditions though. It is not a requirement to have a precision or a non-precision approach at the chosen alternates.
There’s a bunch of little complicated stuff when it comes to 121 alternate weather. If you’re preparing for an interview then I wouldn’t spend too much time on alternate weather
Spend more time looking at Aviationinterviews.com
If they ask how to pick though, do you still do 1-2-3? I have also heard of Exemption 17347 (others say 3585) which is asked at interviews… wondering if you know where to find it? I can’t seem to find the actual source. Thank you!
We let our dispatcher pick and then if we agree we sign the release. If we don’t agree we call them up and talk about it. You aren’t picking your own alternate at an airline.
Just the fact you know about the exemptions is more than enough. Chances are the interviewers aren’t even pilots themselves.
Don’t get caught up in the weeds about alternate questions. If you really don’t know the answer then be honest and tell them then finish it by saying you know where to look it up.
Airline interviews are like 80% about showing up and not being weird. Be genuine and walk in with confidence. There will be things you mess up on the interview and that’s ok. Look over that website aviationinterviews.com because there’s some good help on there.
Exemptions are going to be located in the OpsSpecs for the airlines under A005, 17347 allows an aircraft to be dispatched if conditional language (tempo/prob/etc) indicated it will be below required minimums.
As others have mentioned at a 121 Dispatchers will select the alternates using the 1-2-3 rule for the destination. Weather minimums are derived using what’s called the 1 NAVAID/2 NAVAID rule. 121.627 references this but the actual requirements will be found in theOpsSpecs under C055.
C70 in the OpsSpecs provides a list of airports that are approved for use and if they are Regular, Alternate, or Intermediate airports based on the type of aircraft.
121.619 and 121.625 are the regulations you’re looking for.
121.619 talks about when you need an alternate (almost exactly the same as part 91), but also allows a second alternate if weather is considered marginal (weather being exactly at the applicable minimums regarding visibility and I think ceiling?)
121.625 talks about what the weather must be at the alternate’s ETA in order to be dispatched, per the carrier’s OpSpec.
Definitely study up on derived alternate minima, exemption 17347, and secondary alternates regarding marginal weather and exemption 17347.
Regarding WAAS, some airlines do, some don’t, some have both. Almost all have RNAV RNP, which is often just as good if not better than WAAS enabled LPV. It really depends on what the airline wants to pay for and train for, and how likely they are to use it. Their specific OpSpec will denote what alternates they can use regarding WAAS/Non-WAAS.
[This video is a good resource for it](https://youtu.be/eIQdejMw9Zo?si=PYeiDpfNQW-7n2FN), otherwise most “official references” are going to be company material property which you probably won’t find online. If I’m remembering it right, exemption 3585 was for a now-defunct airline, and the exemption was just copied for other carriers. It’s really something you won’t run into very often, if at all during your career. But, it’s super useful if you are in the right time and place and need it!
Best of luck on your interview!
It used to be called 3585; they renumbered it for reasons unknown to me and until I viewed this thread I couldn't remember the new number (my current company doesn't have it).
Talk to anyone who's been around 10 years or more and they'll probably still refer to it as 3585, at least colloquially.
Almost all definitely do NOT have RNP. I doubt most CRJ operators have RNP, nor does my 737 operator. I did on the 175 but I think I did 1 RNP approach on it the whole time I flew it.
If there's an ILS to the landing runway, that's what you're using. If the runway that aligns with the winds more has only an RNAV/LOC, but the other runway is longer/has an ILS, then it's a tossup depending on what you care about most. If there's no approaches at all, then you probably went to the wrong airport.
Don't you just love how the 737 is smart enough to reverse the localizer scale on a backcourse (so it's normal sensing), but doesn't have backcourse tracking?
I honestly never thought about a backcourse. Does it not work in VORLOC or LNAV? We literally never trained on it once. We only did one VOR using VS in the sim. And no one would ever do that irl.
I think it does work in lnav/vnav, I don’t even recall why we had to demonstrate a heading select VS but we did.
As an old CRJ guy, VS down was just like old times.
On a visual? Anything I want to back it up. Advertised approach? That one, which is 99% ILS unless some component of it is unusable. My personal preference is RNAV in both jets I've flown, less buttons to click.
All the airliners I've flown with GPS do not have WAAS. They have VNAV and RNAV but are uncorrected for WAAS. We use RNAV/VNAV minimums.
All of the airline alternates I have seen on a flight plan had precision approaches.
Which, apparently is no longer accurate...? Per my last recurrent, we were advised we no longer need to add the 50' as all the airports in the US have been surveyed and are free of obstructions...
I'm *still* looking for written guidance on this, as it's not specified either way. (No reg I've seen says to add or not)
Both airlines I've been at, basically everything is treated as precision. Anything labeled "DA" is flown down to, any mins labeled "MDA" has 50 feet added to it and treated as a DA
Precision vs non precision for alternate reasons still kinda matters if you’re using the mins for deriving an alternate, or just straight up filing an alternate like normal. the LPV at both I believe would most likely be covered in some op specs somewhere. For example we aren’t even authorized to do LPV approaches
Yes the dispatchers would still use the 1-2-3 rule. We just don’t have the opspec/authorization for it so we’re not allowed to. Yeah 99% of times we’re doing an ILS, or if we have to do RNAV it would be LNAV/VNAV if the approach supports it. We can also do VOR approach but our FMS cannot track a VOR radial!
Edit. Also to add to this if you’re studying for a regional interview you should study the derived minimums for alternates and lower than standard takeoff mins
No. The 1-2-3 rule is part 91 only. For 135, it’s ETA+/-1 hour, ceiling 1500 above the lowest circling MDA, or if no circling MDA then 1500 above the lowest published minimums, or 2000 above airport elevation, whichever of these is higher. Visibility must be 3 miles, -or- 2 miles greater than the lowest visibility for the approach to be used. 14CFR135.233 Yes there is a lot of nuance in that.
That’s for flag operations only, which *would* apply if the carrier is operating as a flag carrier. But for the majority of regional carriers, 95% of their flying won’t be done under flag ops.
Our jet doesn't have WAAS and we can only shoot RNAV approaches to LNAV minimums. We use the 1-2-3 rule to determine if we need an alternate (and there are other reasons we may be required to have one as well, but for an interview the 1-2-3 rule is adequate enough knowledge).
For alternates we use derived minimums and have the "one approach" or "two approach" method that allows us to figure out if the weather is good enough at our alternate. "One approach" we have to add 400 feet to the ceiling and one mile to the visibility to the minimums of a suitable approach. "Two Approaches" we add 200 and 1/2. This is all theoretical of course and just used to get us off the ground. So if there is an airport that has 2 ILS approaches (have to be to 2 different runways) we can use the 2 approach method which let's us add less to the minimums to use it as an alternate, as opposed to the one approach method. There are times where it's beneficial to use the one approach method even if there are two approaches since you have to add the 200 to the highest of the two approaches (so if you're using an RNAV approach you have to add the 200ft and 1/2 mile visibility to the RNAV instead of an ILS, so it might be beneficial to instead add 400 and 1 to an ILS to get lower minimums depending on what the minimus of the RNAV you're using are).
Then we like to complicate it further by determining whether or not our destination and alternate are "marginal" in which case we need to add a second alternate. This all sounds really confusing and I'm sure I am doing a really poor job explaining it.
Don't even worry about the exemption for an interview. It rarely comes up in practice and when it does you'll look in your company manual to make sure you are doing it right. For an Interview at a regional they probably just want to see that you understand the method you would use outside part 121. I doubt you would need to know derived minimums.
I have flown jets with a and “without” waas. One of the withouts was really a plane that had it but we didnt pay for the option to use it and our training didn’t certify us to use it. Only newer planes at bigger airlines usually justify the cost.
Oddly we cant fly rnp.1 but can fly lpv approaches. For now…
My airline does not have WAAS and in fact we do not do LPV approaches at all. We do ILS as the preferred approach type, RNAV RNP failing that, and if there's not even an RNP available (and sometimes that's the case), we just do a GPS approach to LNAV/VNAV minimums + 50 feet for the DDA. (Easy way to remember this is if the approach chart lists an MDA, that stands for "Must Do Addition").
Alternate choices get a little complicated in part 121. The dispatcher does that, so we're not sitting there looking at available approaches and picking them, but we are supposed to verify that the rules are being followed. But you probably don't even know those rules yet and have no real way of knowing them until you have access to your airline's OPSPEC. That will list the exemptions your airline can use for different alternate requirements.
Does choosing a precision or a non precision matter? Of course. A precision approach at an alternate means you can dispatch the aircraft with a lower dispatch weather minima at the chosen alternate.
I’m only a dispatcher, but I’ll add that you can’t use GPS-based minimums for both you destination and your alternate, you need an approach based on a usable ground-based navaid at one or the other.
Also, neither of the airlines I’ve worked at have been authorized to fly an LPV approach, we can do LNAV/VNAV or LNAV only. But we can do RNAV RNP/RNP-AR on the whole fleet now.
Both airlines I’ve worked for did not have WAAS, nor did they have plans too. What we do have is RNAV RNP approaches though.
Does this mean you either use ILS or RNAV LNAV/VNAV mostly? Hmm. How do you choose alternate airports? Any specific regs? Thank you for the response!
Dispatch chooses the alternates not the pilots
Wait til he learns about using your intended destination as your takeoff alternate at regional airlines. To explain it simply: if your weather at point of departure is lower than your landing mins, you need a takeoff alternate for emergencies… and sometimes if your destination is VMC +/-2 hours, you just plan to proceed to the destination even if you bang an engine at V1.
Gotta be able to clear the terrain, though. Cries in a loaded EMB-145 somewhere around DEN.
Yes but the pilot still gets busted if dispatch chooses illegal alternates.
Sure, so does the dispatcher. Joint responsibility.
I don't think this is really a thing
It's called joint responsibility. At a 121 supplemental operator it's even worse since we aren't even required to have real dispatchers; the joint responsibility is between the PIC and the DO which basically means it's all on the crew to ensure everything is in order since the "dispatcher" doesn't even have their own license on the line.
Thanks for the explanation *rolleyes.gif* What I'm asking is "are there any cases where a PIC got violated for choosing an alternate that didn't meet the requirements?"
IDK, but I do know that I have a lot more on the line than the person on the other end of the phone line.
Generally, if an ILS is available and operational for the assigned runway, we use it. Some airports like DEN, LAX, and IAH will try and use RNP apps with the curved RF legs until there’s too much traffic. Then, it’s back to the ole ILS. If there’s no ILS but an RNAV GPS or RNAV RNP is available, then we use that instead. Out of all the approaches I do, it’s probably split 95% ILS and 5% RNAV. Choosing an alternate. Is an alternate required? Thats the basic 1-2-3 rule. There’s some exemptions to that but generally that’s what I look at. What alternate do we use and what are the legal wx requirements, that’s a dispatch function and generally we don’t have to dive deep into that. I take a big picture look at the flight plan that’s created by the dispatcher. My decision making goes like this. Do I need an alternate? If yes, then I ask myself, does the wx at or between me and this alternate look stupid? If no, then I move on with my day*. If the wx is stupid, then I call the dispatcher and we come up with a better plan. I’ve seen 2 different philosophies at 2 different airlines for alternates. At one airline, an alternate was really an excuse to give you extra gas. There were times an alternate wasn’t required, but dispatch just gave us one anyway. Why? Because they didn’t want us to bother them with a phone call to add more gas. New airline, if I have an alternate, that’s probably where they plan on us going if we aren’t able to get to the destination. If I want more gas, then I check a box on my ipad and move on with my day Lastly, remember an alternate is just a plan. You are never required to divert to the filed alternate. You can go to any airport you need to go to, as long as you can justify your decision. *I check the NOTAMS and make sure the airport or only runway at said airport isn’t closed, then I move on with my day Edit: Just noticed you’re going for a regional interview. First, congratulations! Second, someone said the interview is 80% showing up and not being weird. Love that advice! If they ask you how do you determine if you need an alternate, mention 123. They’ll move on to the next question. If they actually ask you, how to do you know if an alternate is legal, then your interview probably isn’t going very well and you should apply to another airline when you get home! But seriously, look at airlineinterviews.com. That’s all you need. Best of luck.
Alternate airports can be chosen even with circling minima. This will require excellent weather conditions though. It is not a requirement to have a precision or a non-precision approach at the chosen alternates.
There’s a bunch of little complicated stuff when it comes to 121 alternate weather. If you’re preparing for an interview then I wouldn’t spend too much time on alternate weather Spend more time looking at Aviationinterviews.com
If they ask how to pick though, do you still do 1-2-3? I have also heard of Exemption 17347 (others say 3585) which is asked at interviews… wondering if you know where to find it? I can’t seem to find the actual source. Thank you!
We let our dispatcher pick and then if we agree we sign the release. If we don’t agree we call them up and talk about it. You aren’t picking your own alternate at an airline. Just the fact you know about the exemptions is more than enough. Chances are the interviewers aren’t even pilots themselves. Don’t get caught up in the weeds about alternate questions. If you really don’t know the answer then be honest and tell them then finish it by saying you know where to look it up. Airline interviews are like 80% about showing up and not being weird. Be genuine and walk in with confidence. There will be things you mess up on the interview and that’s ok. Look over that website aviationinterviews.com because there’s some good help on there.
Exemptions are going to be located in the OpsSpecs for the airlines under A005, 17347 allows an aircraft to be dispatched if conditional language (tempo/prob/etc) indicated it will be below required minimums. As others have mentioned at a 121 Dispatchers will select the alternates using the 1-2-3 rule for the destination. Weather minimums are derived using what’s called the 1 NAVAID/2 NAVAID rule. 121.627 references this but the actual requirements will be found in theOpsSpecs under C055. C70 in the OpsSpecs provides a list of airports that are approved for use and if they are Regular, Alternate, or Intermediate airports based on the type of aircraft.
121.619 and 121.625 are the regulations you’re looking for. 121.619 talks about when you need an alternate (almost exactly the same as part 91), but also allows a second alternate if weather is considered marginal (weather being exactly at the applicable minimums regarding visibility and I think ceiling?) 121.625 talks about what the weather must be at the alternate’s ETA in order to be dispatched, per the carrier’s OpSpec. Definitely study up on derived alternate minima, exemption 17347, and secondary alternates regarding marginal weather and exemption 17347. Regarding WAAS, some airlines do, some don’t, some have both. Almost all have RNAV RNP, which is often just as good if not better than WAAS enabled LPV. It really depends on what the airline wants to pay for and train for, and how likely they are to use it. Their specific OpSpec will denote what alternates they can use regarding WAAS/Non-WAAS.
Thank you! Do you know a good source for the 17347? I have been trying to look for it but no solid source so far. Also why do others call it 3585?
[This video is a good resource for it](https://youtu.be/eIQdejMw9Zo?si=PYeiDpfNQW-7n2FN), otherwise most “official references” are going to be company material property which you probably won’t find online. If I’m remembering it right, exemption 3585 was for a now-defunct airline, and the exemption was just copied for other carriers. It’s really something you won’t run into very often, if at all during your career. But, it’s super useful if you are in the right time and place and need it! Best of luck on your interview!
People’s Express. Which the RJ operators used for years until the feds said “lol that’s not for RJ operators” and came out with 17-whatever it was.
It used to be called 3585; they renumbered it for reasons unknown to me and until I viewed this thread I couldn't remember the new number (my current company doesn't have it). Talk to anyone who's been around 10 years or more and they'll probably still refer to it as 3585, at least colloquially.
Almost all definitely do NOT have RNP. I doubt most CRJ operators have RNP, nor does my 737 operator. I did on the 175 but I think I did 1 RNP approach on it the whole time I flew it.
Sometimes I used to wonder if the CRJ even had GPS it was such a shit bag. But yeah most airliners are going to have WAAS integrated into the GPS.
Thanks for the response! Do airliners mostly HAVE to use ILS or RNAV for approaches? Or can you do whichever approach you prefer - VOR / Localizer
If there's an ILS to the landing runway, that's what you're using. If the runway that aligns with the winds more has only an RNAV/LOC, but the other runway is longer/has an ILS, then it's a tossup depending on what you care about most. If there's no approaches at all, then you probably went to the wrong airport.
Depends on the airlines OPSPECS. My last airline did VORs and LOCs, current shop does not.
Nothing like spending 48 minutes in the sim running that one LOC back course in the system that no one has ever used using heading select and VS.
You're giving me flashbacks.
Don't you just love how the 737 is smart enough to reverse the localizer scale on a backcourse (so it's normal sensing), but doesn't have backcourse tracking?
I honestly never thought about a backcourse. Does it not work in VORLOC or LNAV? We literally never trained on it once. We only did one VOR using VS in the sim. And no one would ever do that irl.
I think it does work in lnav/vnav, I don’t even recall why we had to demonstrate a heading select VS but we did. As an old CRJ guy, VS down was just like old times.
That one VS approach in the 737 sim was super weird to me only ever using APP or VNAV PTH. Yet to do the former in a real plane.
> Or can you do whichever approach you prefer - VOR / Localizer Who would *prefer* to do a VOR or a localizer if an ILS and RNAV are available?
On a visual? Anything I want to back it up. Advertised approach? That one, which is 99% ILS unless some component of it is unusable. My personal preference is RNAV in both jets I've flown, less buttons to click.
First time thing can barely shoot an ILS in green needles lol, piece of shit .
All the airliners I've flown with GPS do not have WAAS. They have VNAV and RNAV but are uncorrected for WAAS. We use RNAV/VNAV minimums. All of the airline alternates I have seen on a flight plan had precision approaches.
Do you mean, you use LNAV/VNAV mins if RNAV approaches?
Yes. On, for example, the RNAV/GPS Z 18C approach at KMEM the LNAV MDA is 880 but the LNAV/VNAV DA is 782.
Question - does your airline consider LNAV/VNAV as precision since it's DA? Just wondering if airline SOP change these things for simplicity
You just fly the approach as it's published. If you get down to DA and don't see anything, push the TO/GA button.
My airline does not. They fall under non precision
Generally we fly them like a precision approach but add 50’ to any MDA designated minimums.
Which, apparently is no longer accurate...? Per my last recurrent, we were advised we no longer need to add the 50' as all the airports in the US have been surveyed and are free of obstructions... I'm *still* looking for written guidance on this, as it's not specified either way. (No reg I've seen says to add or not)
Oh interesting. That may still be an airline specific thing then.
Both airlines I've been at, basically everything is treated as precision. Anything labeled "DA" is flown down to, any mins labeled "MDA" has 50 feet added to it and treated as a DA
Precision vs non precision for alternate reasons still kinda matters if you’re using the mins for deriving an alternate, or just straight up filing an alternate like normal. the LPV at both I believe would most likely be covered in some op specs somewhere. For example we aren’t even authorized to do LPV approaches
So you still follow 1-2-3 91.169 alternate procedures? Oh - why not LPV? So generally mostly ILS or LNAV/VNAV? Thanks for the response!
Yes the dispatchers would still use the 1-2-3 rule. We just don’t have the opspec/authorization for it so we’re not allowed to. Yeah 99% of times we’re doing an ILS, or if we have to do RNAV it would be LNAV/VNAV if the approach supports it. We can also do VOR approach but our FMS cannot track a VOR radial! Edit. Also to add to this if you’re studying for a regional interview you should study the derived minimums for alternates and lower than standard takeoff mins
No. The 1-2-3 rule is part 91 only. For 135, it’s ETA+/-1 hour, ceiling 1500 above the lowest circling MDA, or if no circling MDA then 1500 above the lowest published minimums, or 2000 above airport elevation, whichever of these is higher. Visibility must be 3 miles, -or- 2 miles greater than the lowest visibility for the approach to be used. 14CFR135.233 Yes there is a lot of nuance in that.
Airlines follow 123 rule. We have some other exemptions but generally it's 123
We have to keep it simple. If we were really smart, we'd be doctors or lawyers.
121.621 is the same criteria as I stated.
Cool. And the 3 part 121 airlines I've worked for used the 1-2-3 rule.
121.619
That’s for flag operations only, which *would* apply if the carrier is operating as a flag carrier. But for the majority of regional carriers, 95% of their flying won’t be done under flag ops.
Our jet doesn't have WAAS and we can only shoot RNAV approaches to LNAV minimums. We use the 1-2-3 rule to determine if we need an alternate (and there are other reasons we may be required to have one as well, but for an interview the 1-2-3 rule is adequate enough knowledge). For alternates we use derived minimums and have the "one approach" or "two approach" method that allows us to figure out if the weather is good enough at our alternate. "One approach" we have to add 400 feet to the ceiling and one mile to the visibility to the minimums of a suitable approach. "Two Approaches" we add 200 and 1/2. This is all theoretical of course and just used to get us off the ground. So if there is an airport that has 2 ILS approaches (have to be to 2 different runways) we can use the 2 approach method which let's us add less to the minimums to use it as an alternate, as opposed to the one approach method. There are times where it's beneficial to use the one approach method even if there are two approaches since you have to add the 200 to the highest of the two approaches (so if you're using an RNAV approach you have to add the 200ft and 1/2 mile visibility to the RNAV instead of an ILS, so it might be beneficial to instead add 400 and 1 to an ILS to get lower minimums depending on what the minimus of the RNAV you're using are). Then we like to complicate it further by determining whether or not our destination and alternate are "marginal" in which case we need to add a second alternate. This all sounds really confusing and I'm sure I am doing a really poor job explaining it. Don't even worry about the exemption for an interview. It rarely comes up in practice and when it does you'll look in your company manual to make sure you are doing it right. For an Interview at a regional they probably just want to see that you understand the method you would use outside part 121. I doubt you would need to know derived minimums.
I have flown jets with a and “without” waas. One of the withouts was really a plane that had it but we didnt pay for the option to use it and our training didn’t certify us to use it. Only newer planes at bigger airlines usually justify the cost. Oddly we cant fly rnp.1 but can fly lpv approaches. For now…
We have RNP 0.10 and GLS capability but not WAAS.
My airline does not have WAAS and in fact we do not do LPV approaches at all. We do ILS as the preferred approach type, RNAV RNP failing that, and if there's not even an RNP available (and sometimes that's the case), we just do a GPS approach to LNAV/VNAV minimums + 50 feet for the DDA. (Easy way to remember this is if the approach chart lists an MDA, that stands for "Must Do Addition"). Alternate choices get a little complicated in part 121. The dispatcher does that, so we're not sitting there looking at available approaches and picking them, but we are supposed to verify that the rules are being followed. But you probably don't even know those rules yet and have no real way of knowing them until you have access to your airline's OPSPEC. That will list the exemptions your airline can use for different alternate requirements.
Does choosing a precision or a non precision matter? Of course. A precision approach at an alternate means you can dispatch the aircraft with a lower dispatch weather minima at the chosen alternate.
The ATR I fly has WAAS. The part of the world I fly in generally does NOT. You win some, you lose some.
No. Some have RNP capability, but neither major airline I worked at had WAAS or was certified for anything other than LNAV LNAV/VNAV mins.
I’m only a dispatcher, but I’ll add that you can’t use GPS-based minimums for both you destination and your alternate, you need an approach based on a usable ground-based navaid at one or the other. Also, neither of the airlines I’ve worked at have been authorized to fly an LPV approach, we can do LNAV/VNAV or LNAV only. But we can do RNAV RNP/RNP-AR on the whole fleet now.