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Is WAAS Required

GrinchF16

Well Known Member
I understand that WAAS is required for vertical guidance on an RNAV approach (LPV) but is WAAS required for point to point navigation in the NAS? For example, if equipped with a non-WAAS GNS430, am I required to have VOR capability to back up the GPS on a Low Airway? Bottom Line - Can I have an IFR airplane with only a GNS430 (non-WAAS) as my sole navigation source?
 
I think you are asking the wrong questions.

1. What would you use for navigation in IMC if you lose contact with the GPS satellite? (I.e. GPS jamming)

2. What’s the required equipment to proceed to your alternative if you go missed approach for a gps navigator with and without waas?

I think you’ll find that the 430 meets minimal requirements, but then do you want to fly in that state? You’ll need an another navigation source if your alternative is IFR with a non-WAAS 430.. A VOR/ILS would solve that issue. You may want a VOR as a backup to GPS if you get into a situation when GPS may not be available. It’s all about risk management and how much risk do you want to take on.
 
Minimum navigation equipment is a non-WAAS (TSO-C129, TSO-C196) as long as you preflight RAIM; the alternate airport can use the non-WASS as long as you flight plan to the LNAV or circling minimums.
 
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No Expert!

OK, I'm NO EXPERT at this...

I believe that a non-WAAS GPS allows you to identify any intersections that are in the database and hence fly intersection to intersection. Further you can use the GPS in place of a DME (I'm pretty sure on this one).

FAR 91.205 d 2 says you need navigation equipment appropriate for the route to be flown. So nothing said about redundancy (but I sure recommend some).

For an example approach look at KCRQ GPS-Y. With VNAV or LPV you can fly to lower minimums (528' / 202 AGL with LPV). With LNAV only you are limited to 1000' MSL. Flying a LOC approach (no GS) you are similarly limited to 1000' minimum. Can you fly it with non-WAAS? I think so. Is it useful? Well at that airport, rarely. As of right now (8:15 p.m.) KCRQ is right at 1000' OVC.

Happy to get myself corrected!
 
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It depends on the capability of the navigator but in your example, if only a 430 is properly installed, It is adequate to use as the sole source of navigation. (Edit: see RAIM requirements Sam posted also)

However, the way I read the regs, if an alternate required, alternate weather must permit a VMC decent to landing from MEA. A non-waas GPS may be used as the sole source but both destination and alternate can't be based solely off GPS approaches, so if you're using a GPS approach at the destination then it has to be VFR at alternate and weather must permit a decent in VMC from MEA.
 
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It depends on the capability of the navigator but in your example, if only a 430 is properly installed, It is adequate to use as the sole source of navigation. (Edit: see RAIM requirements Sam posted also)

However, the way I read the regs, if an alternate required, alternate weather must permit a VMC decent to landing from MEA. A non-waas GPS may be used as the sole source but both destination and alternate can't be based off GPS approach, so if you're using a GPS approach at the destination then it has to be VFR at alternate and weather must permit a decent in VMC from MEA.

I have a WAAS GPS as the sole source. I do not have a panel ILS/VOR at all. I do carry a backup Yaesu FTA 750L, that is connected to an external antenna and is for emergencies only, and I practice ILS using it. It's not pretty but it mitigates the risk. There were several factors that made me comfortable with this, one of them being I have an AP that is as capable the airplane I fly professionally

Tom
Please point me to the specific reg that requires a VMC descent to the alternate. This is interesting, parsing the finer points of IFR operations. :)

Sam
 
I understand that WAAS is required for vertical guidance on an RNAV approach (LPV) but is WAAS required for point to point navigation in the NAS? For example, if equipped with a non-WAAS GNS430, am I required to have VOR capability to back up the GPS on a Low Airway? Bottom Line - Can I have an IFR airplane with only a GNS430 (non-WAAS) as my sole navigation source?

For flying under IFR with a TSO129 (non WAAS) GPS, you must:
1. Have an alternate means of navigation on board, which pretty much means VOR.
2. In addition, the aircraft and either the destination airport or the alternate airport must be capable of executing a non gps approach.

So: 1. Is waas required for navigation enroute? No. But…..
2. Are you required to hav VOR capability to back up the gps? Yes.
3. Can you have an IFR airplane with only a non-WAAS 430? Yes, since you have both a gps and a VOR. If you asked about a non-WAAS 420 (no vor) the answer would be NO.
 
Tom
Please point me to the specific reg that requires a VMC descent to the alternate. This is interesting, parsing the finer points of IFR operations. :)

Sam

Let me try and find an actual reference...but it's essentially the same as filing a destination or alternate airport without an instrument approach. I believe the wording says if your destination only has a GPS approach you have to be able to conduct another type of approach at your alternate. If the alternate has a GPS only, then the weather forecast needs to allow a visual approach...a descent in VMC from MEA to landing.

However, this is only for planning. Once you're in the air, you can shoot the GPS at the alternate if you needed it. If the FAA came a knocking you just need to show that you planned accordingly.

My first post was a little confusing with the tangent on my install (edited). Also, I didn't mean to say the alternate required weather for visual approach. This is only required if the destination and alternate only have a GPS approach...if either has an ILS or VOR you most certainly could plan without limits with the 430.
 
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For flying under IFR with a TSO129 (non WAAS) GPS, you must:
1. Have an alternate means of navigation on board, which pretty much means VOR.
2. In addition, the aircraft and either the destination airport or the alternate airport must be capable of executing a non gps approach.

So: 1. Is waas required for navigation enroute? No. But…..
2. Are you required to hav VOR capability to back up the gps? Yes.
3. Can you have an IFR airplane with only a non-WAAS 430? Yes, since you have both a gps and a VOR. If you asked about a non-WAAS 420 (no vor) the answer would be NO.

Personally I have VOR (KX155) with my 400 WAAS, so I have an alternate means of navigation... but I'm curious - where actually is the reg that requires this?
 
Tom
Please point me to the specific reg that requires a VMC descent to the alternate. This is interesting, parsing the finer points of IFR operations. :)

Sam

Found it...I was beginning to doubt my CFII knowledge. Of course it wouldn't be the first time I'm wrong.

FAR 91.169(c)(2)
 
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Personally I have VOR (KX155) with my 400 WAAS, so I have an alternate means of navigation... but I'm curious - where actually is the reg that requires this?

Since you have a TSO 145/146 (WAAS) gps, no alternate means of navigation are required. For those with a non-WAAS, TSO 129 gps, the TSO itself requires alternate means of navigation. The requirements are summarized in the AIM.
 
Since you have a TSO 145/146 (WAAS) gps, no alternate means of navigation are required. For those with a non-WAAS, TSO 129 gps, the TSO itself requires alternate means of navigation. The requirements are summarized in the AIM.

Just to add, the OP was asking about a 430. That device has both a 129 GPS AND a built in alternate navigation source -VLOC.
 
You guys are awesome

What a great discussion. Fully answered my questions. Interesting that one container that has GPS and LOC can meet the requirements. I guess the issue is a global GPS issue vice an equipment failure. Thanks again guys!
 
What a great discussion. Fully answered my questions. Interesting that one container that has GPS and LOC can meet the requirements. I guess the issue is a global GPS issue vice an equipment failure. Thanks again guys!

Further interesting that this doesn’t meet the legal requirements in Canada; they demand separate boxes. And I think a ‘global’ GPS issue is very unlikely. More likely is deliberate, or not deliberate, local interference; maybe sometimes bad satellite geometry.
 
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