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RNAV (GNSS)

Old 17th Dec 2014, 21:24
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I believe the FAA is still committed to decommission the vast majority of VORs by 2020. A huge number of existing ILS procedures must be revised as a result. I wouldn't be surprised if many of the ILS procedures will be retired along with the VORs.
I have sat thru at least four of the MON presentations, the most recent one was this October. They do not plan to eliminate the vast majority of VOR's, at best it will be less than 50% and the Western third of the country, Alaska, and Hawaii will be untouched. There are also several VOR systems that will remain in place because of international agreements. I have asked the question regarding ILS and these systems are not in the plan for removal, but there are changes going to be needed to support them, including using GPS for joining the ILS and installing DME to replace fixes that were once done using locators and VOR radials. A good example is my airport. The ILS was split into two procedures, one which requires GPS and the other which requires DME. The DME is newly installed. See ILS or LOC Y RWY 2 and the Z variation at KUZA.

As part of the MON, the FAA will provide at least one "safe" ILS procedure without any dependency on DME, GPS, or Radar wihtin 100 NM of any place in the NAS where the MON is removing VOR's.

Finally, removing VOR's is going to be a long process and undoubtedly get very political before it is over. Loss of ground based Navaids for approaches will generate a lot of squealing.
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Old 17th Dec 2014, 22:44
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As part of the MON, the FAA will provide at least one "safe" ILS procedure without any dependency on DME, GPS, or Radar wihtin 100 NM of any place in the NAS where the MON is removing VOR's.
Actually I believe the intent is to have a non-GPS approach within 100 NM. This includes not only ILS approaches but also LOC and yes even VOR approaches.

Anyway, think of of VOR MON as "Phase I" in the overall VOR decommissioning process.

MON will reduce the number of VORs by up to 50%, as mentioned. The timing keeps on slipping, but let's say this is completed by 2030 for discussion's sake.

But what happens after MON? VOR decommissioning won't stop!

MON is a required "stepping stone" because we need to provide backup to GPS/GNSS in case of a global or local outage (e.g., interference, jamming, etc.) But MON cannot meet "NextGen" level of performance required for PBN, so the FAA, partners & industry are working on an alternative navigation system (APNT: "Alternate Position, Navigation, Timing").

APNT will likely based on a network of DMEs. That is, improving the tech behind today's DME/DME/IRU RNAV, so even if all GPS signals are lost, enroute RNAV can still be maintained to PBN requirements (e.g., RNP 0.3).

For this to happen, the existing DME network has to be enhanced to provide better accuracy and/or augmented with "pseudo-satellite" signals from ground-based transmitters (GBTs). Think of GPS signals sent via ground antennas instead of from space.

(That is why we never hear of DME decommissioning -- the FAA has big plans for them).

The idea is to have APNT up and running by the end of MON (in our discussion, 2030). Then Phase II can start: most of the remaining VORs, except few critical ones, can then be dismantled in favor of APNT.

(By the way the FAA is currently aiming to have APNT fully operational by 2025).
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Old 2nd Dec 2020, 17:42
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Originally Posted by peekay4 View Post
The point is to reduce minimums when safe practices allow it.

Examples:

1. FAA OpSpec C073 VNAV MDA as DA:

"The certificate holder is authorized to use minimum descent altitude (MDA) as a decision altitude (DA)/decision height (DH) with vertical navigation (VNAV) on a Nonprecision Approach (NPA)."

8900.183 - OpSpec/MSpec/LOA C073, Vertical Navigation (VNAV) Instrument Approach Procedure (IAP) Using Minimum Descent Altitude (MDA) as a Decision Altitude DA)/Decision Height (DH) ? Document Information

2. Transport Canada Special Exemption from 602.128(2)(b)

"The purpose of this exemption is to permit pilots-in-command of IFR aircraft operated by holders of an air operator certificate or a temporary private operator certificate to descend below the minimum descent altitude (MDA), when conducting a non-precision approach ... following a stabilized constant descent angle (SCDA) non-precision approach."

EXEMPTION FROM PARAGRAPH 602.128(2)(b) OF THE CANADIAN AVIATION REGULATIONS - Transport Canada

(SCDA is the Canadian term for CDFA).
Peekay, the link says the Transport Canada exemption was over in 2015. I tried to do a search with Transport Canada, to see if it was re issued but came up empty. Do you or anyone else have any further input on exemptions?

thanks,

Hawk
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Old 2nd Dec 2020, 18:20
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Originally Posted by hawk37 View Post
Peekay, the link says the Transport Canada exemption was over in 2015. I tried to do a search with Transport Canada, to see if it was re issued but came up empty. Do you or anyone else have any further input on exemptions?

thanks,

Hawk
This may help you...

I remember seeing the extension to this exemption several years back and I cannot recall at this time if it is on an annual basis that TC renews it.

However, I can definitely tell you it is still in force because it is part of our OPs Manual and SOPs and TC would have advised us if the exemption had ended.

FYI, this exemption is only good while operating in Canada.
Jet Jockey A4 is offline  
Old 3rd Dec 2020, 18:14
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Thanks Jet Jockey, I found the current Canadian exemption here

https://www2.tc.gc.ca/civilaviation/...cs/en/3278.htm

As you say, it appears to be re issued on an annual basis. Some initial and recurrent training required, ground school and in sim/aircraft, and most non prec approaches qualify.

For the USA operations it requires an Ops spec, M spec, or for Part 91 an LOA. C073 is the designation, info is here

https://fsims.faa.gov/PICResults.asp...egory=all~menu

And now navigate to Volume 3, Chapter 18, Section 5, Paragraph 3-871, sub-paragraph “OPSPEC/MSPEC/LOA C073.

Note that for US ops, VNAV to a dh vice an MDA is not necessarily permitted for all Non precision approaches, read the requirements closely

Hawk
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