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RNAV (GNSS)

Old 11th Dec 2014, 20:53
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OK465

LPV (Localiser performance with Vertical guidance) Boeing aircraft are not equipped to utilise LPV minimums.

But i take your point
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Old 12th Dec 2014, 01:44
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The FAA and Transport Canada recognize only the LPV approach as a "precision" approach.

LNAV and LNAV/VNAV are considered "non precision" approaches.

Any approach (LNAV and LNAV/VNAV) that shows its minimum as a MDA minimum must not be flown below that minimum in the event of a missed approach (usually) and that is the reason for some operations adding an increase of 50 feet to that MDA to make it a DA.
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Old 12th Dec 2014, 01:46
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@ OK465...

That's because they added 77 feet to change it to a DA.
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Old 12th Dec 2014, 03:09
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The FAA and Transport Canada recognize only the LPV approach as a "precision" approach.

LNAV and LNAV/VNAV are considered "non precision" approaches.
No, an LPV is not considered a precision approach.

LPV and LNAV/VNAV are considered Approach with Vertical Guidance (APV). APV minima depict DA(H).

LNAV is considered a Non-Precision approach (NPA). NPA minima depict MDA(H).

One does not "add" anything to an LPV or LNAV/VNAV procedure to "change it" into a DA. The DA is determined by obstruction clearance standards.

For definitions, ref: AIM 5-4-5, FAA Order 8260.3B, Transport Canada AC 700-023, and ICAO Annex 10.

Or see some discussion earlier in the thread.

Last edited by peekay4; 12th Dec 2014 at 03:19.
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Old 12th Dec 2014, 03:58
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Guess some of the procedures described here are company procedures.

If it is a LNAV/VNAV RNP (BARO VNAV) it must be flown in VNAV and for the 737NG VOR update must be switched off and vertical RNP must be changed from 400' to 125'.
That is the procedure we use for RNP AR approaches, but for normal LNAV/VNAV RNAV procedures we simply press APProach and go, there is no need for any other switching. On the bus we use a fully managed approach for normal RNAV LNAV/VNAV approaches, however in my opinion the implementation of "fully managed" is better on the boeing than on the bus.

LNAV minima will be higher than LNAV/VNAV minima
Again, that depends. Especially to which temperature that LNAV/VNAV minimum can be used. If too low a temperature is chosen the minimum can be substantially higher than the bare LNAV minimum.
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Old 12th Dec 2014, 04:42
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@ peekay4...

My mistake, I did not proof read my comment and you are correct about not adding the 50 feet to the LNAV/VNAV approach. I meant to say all other non precision approaches can be flown to a DA instead of MDA by adding 50 feet if your company is entitled to.

However I would have agreed with you on the LPV "non precision" approach status until a few days ago.

I'm just back from a recurrent training and the instructors at the training facility told us that the FAA just changed the status of the LPV approach (I assume this change happened not too long ago) and without giving us more specifics, that the LPV approach is now considered a "precision approach".

We were told the same thing in the sim by the sim instructor and our check pilot also alluded that he read something lately about LPVs from TC. His comment was that it was in the final stages of being approved by TC as a precision approach... Just passing on what I was told in class and in the sim a few days ago.

Also the aircraft manufacturer of the aircraft I fly as now changed the autopilot limitation to allow us to fly down to 80 feet on a LPV approach just like a CAT I or II approach. All other types of approaches are still restricted to 320 feet AGL with the AP engaged (which in itself means nothing on how it relates to LPV approach status).

Last edited by Jet Jockey A4; 12th Dec 2014 at 13:47.
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Old 12th Dec 2014, 14:04
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I'm just back from a recurrent training and the instructors at the training facility told us that the FAA just changed and I guess that means not too long ago and without giving us more specifics, that the LPV approach is now considered a "precision approach".
Yes, and no. As of November (last month) the ICAO reclassification scheme went into effect and will eventually be fully incorporated by member states.

The new scheme introduces two types of approach methods (2D and 3D), two types of approach minima (Type 1 and Type 2), in addition to redefining three types of approach procedures (NPA, APV, and PA).

1. Approach methods:

2D: without vertical guidance, flown to an MDA(H)
3D: with vertical guidance, flown to a DA(H)

2. Approach minima:

Type A: minimums 250 ft (75m) or greater
Type B: minimums below 250ft (75m), and further divided into CAT I, II and III

3. Approach procedures:

Non-Precision (NPA): an instrument procedure (IAP) designed for 2D Type A
Approach with Vertical Guidance (APV): an IAP designed for 3D Type A
Precision Approach (PA): an IAP designed for 3D Type B

You can see even in the "new world" there is still a differentiation between APV and PA approach procedures, although they are both considered 3D procedures.

The beauty of all the above is I haven't had to specify any kind of equipment (ground & airborne) are required to fly an approach. The new classification better aligns with the Performance Based Navigation (PBN) concept.

With the new classification, in the future we can better "mix and match" what equipment can be used with which approach procedures (so back to the original question asked in this thread).

So how will existing LPV approaches fit into the new classification? Depends on the particular approach procedure. Many LPV approaches do meet the criteria for a Precision Approach procedure (e.g., at KAPA Rwy 35R), but other LPV approaches only meet the APV criteria (e.g., at KRIL Rwy 26).

Last edited by peekay4; 12th Dec 2014 at 15:17.
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Old 12th Dec 2014, 14:29
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Well I guess we just better start making pop corn and see how all of this will play out!

Why can't they just keep it simple?
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Old 12th Dec 2014, 15:16
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2D: without lateral guidance
Haha, thanks for catching that. Fixed.

Life may end up being simpler with the new classification -- in the future. It's just that we're in transition now, so things seem complex since we have to live with the old and the new.

E.g., today we have so many types of approach procedures because they are based on the equipment required (NDB, Lctr, VOR, VOR/DME, ILS, LOC, MLS, GPS, GLS, RNP, etc., etc.) This situation will only get worse as new technologies come online.

In the future, we may end up with just three standardized approach procedures (NPA, APV, PA). That's it. Most aircraft will have GPS/RNAV and most airports will have at least one 3D approach.

From a pilot's perspective, all we care about if we're going to fly 2D or 3D. The FMS can automagically select the most appropriate approach technology & calculate the relevant minimums based on equipment available.

Simple. Maybe? Depends on how the transition goes, I guess.
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Old 14th Dec 2014, 08:26
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200' ROC, 50' momentary descent.....until they get over that, you are stuck.
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Old 14th Dec 2014, 17:46
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peekay4:

Most aircraft will have GPS/RNAV and most airports will have at least one 3D approach.
If it were only so. But look at all the LP approaches in FAA-dom now, and they are being added quite rapidly.
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Old 14th Dec 2014, 21:06
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Yeah.

In 2010, ICAO resolution A37-11 set the goal that all instrument runway ends world-wide shall have APV (3D) approach procedures by 2016, with 70% to be completed by this year. Under some exceptions, straight-in 2D LNAV approaches may be substituted.

While this lofty goal will be hard to reach, the transition to RNAV/GNSS/PBN as the primary method for approaches seem inevitable.

Here's the 2012 snapshot of the progress towards that goal, with a number of member states already achieving much, from the ICAO database:

State (% PBN Runways completed, 2012)

Finland -- 96%
United States -- 94%
New Zealand -- 94%
Kenya -- 93%
Australia -- 91%

Austria -- 79%
Canada -- 75%
Egypt -- 71%

Brazil -- 62%
Germany -- 54%
Czech Republic -- 53%
Chile -- 52%

Costa Rica -- 40%
France -- 38%
Denmark -- 37%
Norway -- 36%
Switzerland -- 35%
Singapore -- 33%

Netherlands -- 26%
Thailand -- 24%
Japan -- 23%
Indonesia -- 21%
Russian Federation -- 20%
United Kingdom -- 19%
Spain -- 14%

China -- 9%
Ecuador -- 9%
Italy -- 8%
Sweden -- 5%
Turkey -- 3%

Mexico -- 2%
India -- 1%
Belgium -- 0%
Greece -- 0%
Ireland -- 0%
Israel -- 0%

(*) A number of small states with few instrument runways are either at 100% or 0% completion.
(**) These are 2012 numbers (latest in the published database), many states have made considerable progress since.
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Old 15th Dec 2014, 00:51
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While this lofty goal will be hard to reach, the transition to RNAV/GNSS/PBN as the primary method for approaches seem inevitable.
No doubt about it for IFR airports. (That leaves a whole lot of VFR airports without anything.)

And, the GNSS/GPS/RNAV IAP may be nothing more than LNAV to circling minimums and perhaps at a 90 degree angle to the runway. (example KEMT).

Make no mistake, the FAA didn't pay for WASS unless they wanted LPV to "every runway end." But, that was the high-level movers and shakers. Not those who faced with the hard realities of terrain and close-in runway environment.

Further, ILS at the principal U.S. airline airports will remain primary. As well as in the lofty ICAO world.
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Old 15th Dec 2014, 02:10
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Further, ILS at the principal U.S. airline airports will remain primary. As well as in the lofty ICAO world.
Well the intent (both FAA and ICAO) is to eventually replace the majority of ILS installations with WAAS or GBAS approaches (i.e., LPV and GLS). GLS CAT I is already operational in the US, and the FAA is currently testing GLS CAT III prototypes. (Only about 100 of the 1,200 ILS systems in the US are CAT II/III).

The FAA had planned to start phasing out some ILS installations by 2015, however the timing may be under review.

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.
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Old 15th Dec 2014, 14:00
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Well the intent (both FAA and ICAO) is to eventually replace the majority of ILS installations with WAAS or GBAS approaches (i.e., LPV and GLS). GLS CAT I is already operational in the US, and the FAA is currently testing GLS CAT III prototypes. (Only about 100 of the 1,200 ILS systems in the US are CAT II/III).
Politics and economics always trump the FAA. GLS is slowly progressing because one airline is willing to dabble with it.

But, think if you were a fleet manager at say, DAL or AAL, where Boeing wants a million dollars per airplane in your 150 bird fleet to change out your FMS and related gear to give you WAAS/LAAS and GLS auto-land capability. I don't know the exact count of CAT III ILS's but your number sounds correct. Those 100, or so, CAT III systems are at airports that get weather on a frequent enough basis that fail-active autoland is essential.

I those CAT III ILS's will be around for a lot of years.

As to VORs, the FAA is already pruning them, but rather slowly. They agreed with ICAO to not decommission any VORs that are the end point of oceanic routes. Also, few, if any, in the intermountain west.

If the politics of existing avionics hadn't driven the equipage of RNP AR, that system would transition from LNAV/VNAV to GLS and much lower minimums than we see today with RNP AR.
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Old 15th Dec 2014, 16:39
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But, think if you were a fleet manager at say, DAL or AAL, where Boeing wants a million dollars per airplane in your 150 bird fleet to change out your FMS and related gear to give you WAAS/LAAS and GLS auto-land capability.
Well, DAL just performed their first GLS approach into Houston a couple of weeks ago (December 1). They already have 34 GLS-capable B737s, out of a total of 112 GLS-capable B737s on order. According to the FAA, DAL is also considering GLS for 45 A321 future deliveries.

AAL will have GLS on all of their B787s on order (GLS is a standard feature on new 787s).

From an economics perspective, these new technologies will allow more fuel-efficient operations at higher traffic densities.

Not to mention, the FAA currently spends $100 million each year for ILS maintenance. It would be a big win if this number can be cut in half through decommissioning. Maybe keep one ILS per airport for backup (as opposed to one per runway end), in addition to the CAT II/III ones.
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Old 15th Dec 2014, 17:09
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I do expect to see CAT III ILS around for quite a long time. Regulatory progress is extremely slow. We have done GLS autoland trials five years ago with excellent results, however there is no apparent movement to allow lower than CAT I minima in europe. Even though we have been certified for operational use of GLS since 2009 there was only one airport in my country with an operational GLS until a few months ago, when FRA introduced the second GLS station and GLS approaches to all landing runways.

Getting approval was helped by the fact that boeing essentialy offered us GLS free of charge on all 737s since 2006. Sadly a retrofit on our A320 fleet would cost around a quarter million per aircraft which makes it economically unfeasible. Since we are now phasing out the 737 in favor of A320s we will lose our GLS capability. If we (or our on this site unmentionable major shareholder) orders new Airbii it might be included.
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Old 15th Dec 2014, 17:12
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AAL will have GLS on all of their B787s on order (GLS is a standard feature on new 787s).
Didn't take Boeing very long.
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Old 16th Dec 2014, 15:31
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Don't worry...

FAA FY2015 budget: $15 billion.

DoD FY2015 budget: $560 billion. Cost of satellite upgrades amortized over service life: $366 million per year.

I think the DoD can afford it.

As a comparison the FAA spends ~ $220 million a year to maintain "legacy" navaids (VOR, NDB, ILS, etc.).
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Old 17th Dec 2014, 09:05
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GBAS appears to be a no cost option on both A and B.The benefits are immense, cost is low, I cannot understand why it is not on every ac and installed at virtually every airport.
Something just doesn't make sense here.
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