Question about GNSS MEA

[ARFlyer]

While flight planning to WV and studying for my II checkride, I came across something I haven't seen before.

Does the Blue MEA mean I can fly @5900' with a current 430 GPS ?

V519 Between BLF and BKW.

The route looks like the followed

9000
5900G R-193 UNUSABLE
*5900 BELOW 9000
-V519-------------------------193 [BKW]

 

[poadeleted20]

That is exactly what it means -- if you have an IFR-legal GPS with at least enroute certification, and that is what you are using to navigate, your MEA on that segment is 5900.

 

[azure]

I'd be interested to know the answer too. My understanding is yes, the MOCA is 5900 but the MEA for VOR-based nav is higher to ensure adequate VOR signal reception (the BKL radial defining the airway being unusable below 9000, as noted on the chart). I don't see any reason you couldn't use the G-MEA, though I suspect you would have to be sole source equipped to legally do it.

 

[poadeleted20]

I'd be interested to know the answer too. My understanding is yes, the MOCA is 5900 but the MEA for VOR-based nav is higher to ensure adequate VOR signal reception (the BKL radial defining the airway being unusable below 9000, as noted on the chart).

Concur.

I don't see any reason you couldn't use the G-MEA, though I suspect you would have to be sole source equipped to legally do it.

No, you would not, but with a non-sole source c129 GPS, you'd still need a working VOR aboard even if you weren't using it. Same as going direct to an intersection or flying a GPS-based approach.

 

[azure]

Concur.
No, you would not, but with a non-sole source c129 GPS, you'd still need a working VOR aboard even if you weren't using it. Same as going direct to an intersection or flying a GPS-based approach.

Understand, but what good is that VOR going to do you if you lose RAIM on the airway at 5900? The radial you're on is unusable at that altitude. If you then lose comms, you have no way of following 91.185.

I agree, this seems to be much the same as accepting a clearance direct to an intersection with only C-129 certification. It's legal but seems like it shouldn't be without some backup capable of navigating the cleared route.

 

[poadeleted20]

Understand, but what good is that VOR going to do you if you lose RAIM on the airway at 5900? The radial you're on is unusable at that altitude. If you then lose comms, you have no way of following 91.185.

Sure you do -- you fly at the highest of the three (MEA, Expected, Assigned), just as 91.185 says to do. On the leg under discussion, let's say last assigned was 7000 with no expected higher, so you were at 7000 as the "highest of the three" with GPS working. If the GPS quits, the MEA just changes from 5900 to 9000, so the "highest of the three" is now 9000, and you would commence a climb to 9000. In that regard, this would be no different than any other MEA change on an airway during lost comm.

I agree, this seems to be much the same as accepting a clearance direct to an intersection with only C-129 certification. It's legal but seems like it shouldn't be without some backup capable of navigating the cleared route.

The FAA does not require a backup GPS in order to fly GPS routes any more than they require a second VOR to fly a VOR airway/approach (other than those approaches where dual VOR is specifically required for lower stepdown mins), and after 20 years of GPS operations, I don't see any indication that this is a significant issue.

 

[azure]

Sure you do -- you fly at the highest of the three (MEA, Expected, Assigned), just as 91.185 says to do. On the leg under discussion, let's say last assigned was 7000 with no expected higher, so you were at 7000 as the "highest of the three" with GPS working. If the GPS quits, the MEA just changes from 5900 to 9000, so the "highest of the three" is now 9000, and you would commence a climb to 9000. In that regard, this would be no different than any other MEA change on an airway during lost comm.

Okay, I guess that makes sense. Here you can quickly reacquire course guidance, you just have to climb to receive it.

The FAA does not require a backup GPS in order to fly GPS routes any more than they require a second VOR to fly a VOR airway/approach (other than those approaches where dual VOR is specifically required for lower stepdown mins), and after 20 years of GPS operations, I don't see any indication that this is a significant issue.

I didn't say anything about a backup GPS. Without sole source GPS, your backup is ground based nav, a VOR receiver or an ADF. My point was, if you're cleared direct to an intersection with a C-129 GPS and you lose RAIM, how do you fly your clearance if you go lost comms?

Seems like the FAA is only concerned with recovery from single point failures, so the answer is, you are assumed to be able to inform ATC and get a new clearance (direct to a VOR or whatever) you can fly with your ground-based nav backup.

 

[poadeleted20]

Okay, I guess that makes sense. Here you can quickly reacquire course guidance, you just have to climb to receive it.

Yup.

I didn't say anything about a backup GPS. Without sole source GPS, your backup is ground based nav, a VOR receiver or an ADF. My point was, if you're cleared direct to an intersection with a C-129 GPS and you lose RAIM, how do you fly your clearance if you go lost comms?

As I said, it's the same as if if you had only one VOR for nav, and you lost both comm and that one VOR at the same time -- simultaneous multiple failures are beyond the scope of the rules.

Seems like the FAA is only concerned with recovery from single point failures,...

Exactly.

...so the answer is, you are assumed to be able to inform ATC and get a new clearance (direct to a VOR or whatever) you can fly with your ground-based nav backup.

You got it.

 

[ARFlyer]

That is exactly what it means -- if you have an IFR-legal GPS with at least enroute certification, and that is what you are using to navigate, your MEA on that segment is 5900.

Thanks!