If we're doing an ILS approach, then Yes!

Every ILS, autoland or not, the airplane does the exact same until you hit the disconnect button. Afterall, it doesn't know if/when you're going to disconnect.

Boeing airplanes have two different buttons to hit to commence the approach, and which button you hit depends on what kind of approach you're doing. If you're doing an ILS approach (autoland or not) you hit the APProach switch. That connects the autopilot and/or Flight Director to the LOC and GS. If you're doing a RNAV approach, you hit the LNAV button, which does NOT connect the AP/FD to the LOC/GS

I beg to differ, newer boeings do it all with the APProach button.

Irrelevant. Airbus does it all with the approach button as well (for those who beg to differ), but in the case of ILS it tracks the beam, in the case of NPA (except LOC) it goes to FINAL APP (LNAV/VNAV). And in that case monitoring of raw data for non RNAV approaches (navaid and baro altitude) is mandatory (still waiting for the countries where it's not).
Again all this is irrelevant. The interviewer' s question still makes no sense.

:ugh:

I beg to differ, engfireleft, if the approach is on a ground-based navaid (for the pendants: VOR, VOR/DME, TACAN, NDB, that is non-LOC) it is an FMS approach flying an overlay. The approach is drawn to TERPS, PANS-OPS standards for the terrestrial navaid, not to RNAV or RNP standards. There is no specified RNP because it is a conventional approach flown on the FMS. the crew must be trained appropriately, the database current and used. The Canadian-built and trained business aircraft is flown and trained thusly.




A bit of history and explanation. If you don't want to read it skip right to the end.

When regulators first realized GPS could be used to fly an approach they invented "GPS" approaches. There were very few of them around however so as a quick, cheap and easy means of getting more of them out there they created "overlay" approaches. These used existing NPA approaches and effectively bolted an RNAV procedure over top. The design criteria was as for a conventional approach as well as the minimums. We were just permitted to use the RNAV capability of the aircraft to fly it. These types of approaches are disappearing as proper standalone RNAV approaches are built to replace them.

The naming convention for RNAV approaches used to be all over the map. RNAV approaches are all called "RNAV" now because under the Performance Based Navigation (PBN) concept it is recognized that any system that meets the performance requirement of the approach is acceptable. That's why GPS approaches are disappearing. Some may specify GNSS as a requirement but the type of approach is still titled "RNAV". Even further some approaches require specific additional RNP values and you will see (RNP) in the title. These approaches require special authorization, or "AR".

On generic RNAV approaches you may see up to three separately named minima boxes, (LNAV), (LNAV/VNAV) and (LPV). These are not just different minima for the same approach. They are in fact three separate types of approach each with their own design criteria.

LNAV is much like existing NPA's in that they have a stepdown obstacle clearance criteria. They can still be flown using VNAV, but only down to 0 degrees C, because below that the correct clearance may not be maintained. (Exception is with temperature compensating FMS systems).

LNAV/VNAV must be flown using a constant descent and VNAV because it is a sloping obstacle clearance criteria that is certified down to a temperature clearly stated on the chart. Below that temperature the LNAV/VNAV approach may not be flown, unless you have a temperature compensating FMS.

LPV approaches are also sloping, but can be flown at any temperature. That's because they require WAAS (or soon dual frequency GPS receivers) and provide vertical as well as lateral positioning guidance, unlike LNAV and LNAV/VNAV which use BARO-VNAV.

In all of these approaches the procedure must be pulled from the database and not modified in any way from the FAF to the threshold, unless you do not use VNAV then the altitude at the FAF may be modified. The waypoints, tracks, distances and altitudes must also be verified from the plate.

Overlay approaches are RNAV approaches even though the term RNAV does not appear in the title. They are flown using the FMS as the sole reference just like standalone RNAV approaches, and are therefore subject to the same restrictions and operating procedures. The aircraft must be certified, and the crew must be properly trained and certified to conduct RNAV approaches as well.

@ engfireleft

I would make just one correction, there are NO RNAV approaches beyond the FAF in the PBN concept. The approaches are either RNP APRCH or RNP AR APRCH.

The lowest value for RNAV is RNAV1

All of which is irrelevant to the original question, for which the correct answer is still that there are NO rnp requirements for ILS, VOR or NDB approaches.

Many people on this thread have answered the wrong question i.e. On specific equipment under specific regulations what methods of flying NPAs are certified?

For those who have chosen to answer that question I would ask, at what value EPU or ANP will your equipment alert you of error on A) an ILS b) a VOR and c) an NDB approach?

"I would make just one correction, there are NO RNAV approaches beyond the FAF in the PBN concept. The approaches are either RNP APRCH or RNP AR APRCH.

The lowest value for RNAV is RNAV1"

Thank you sir. I just re-read that portion of the PBN manual and stand corrected. Hopefully this is the final version of the naming convention.

Regarding RNAV 1, interestingly the ADS-B due for implementation in the United States beginning in 2013 and mandatory by 2020 has a navigation accuracy requirement of 0.05 nm. The bar gets raised (or lowered) yet again.

a) no RNP, automatic alert is based on scale deflection, but i never talked about precision approaches anyway (APV/GLS/MLS/ILS/PAR).
b) 0.3 (no need to monitor the nav source on which this approach is build)
c) 0.3 (no need to monitor the nav source on which this approach is build).

The ICAO PBN definitions allow still for a lot of different ways to implement them and most of it is not yet fully implemented in many countries.

Suppose for some reason you don't have your 0.3. (Airbus 320 FCOM 1.22.20 p.8 says 0.3 for GPS, 0.5 for other cases)
You can still do VOR and NDB approach, can't you? Even in NAV mode with positive accuracy check and raw data monitoring (FCOM 3.03.19 p.6). As far as I know every airplane has still needles...

So what is the answer to the original question:

"what is the RNP value required for an ILS, VOR and a NDB approach? "

Answer: RNP is irrelevant. :mad:

Engfireleft

If I go into the database, activate a VOR/DME approach to our home drome, what kind of approach am I flying, if I arm LNAV/VNAV and fly it with FMS data displayed? I would offer that it is a VOR/DME overlay. The approach was designed to TERPS NPA standards, it is flown with a CDA to a MDA.

The approach has no specified RNP value, it was not designed to RNP or PBN standards, it is not termed RNAV or RNP, it is not charted as such. Yes, this is certified, it is trained this way, we are checked flying ground-based approaches this way.


Any thoughts?

GF

FE Hoppy:

I would disagree with that. :=:)

1. RNAV IAPs that are not RNP AR APRCH, are nonetheless performance based, as implied in the ICAO title you state, RNP APRCH. In other words both types of approaches you cite are performance based, except in some cases the RNP AR APRCH missed approach is not performance based.

2. All approaches that are designed to be used with LNAV or LNAV/VNAV are RNAV procedures, whether at RNP 1.0 or RNP 0.1. The degree of monitoring and alerting are a different matter.

Aristoclis, surely answer would be if approcah is flown using conventional navigation then no RNP value is required, if flown using FMS as primary source then required values are XXX.. Not simply " it is irrelevant" it is definately "relevant" from what even you say

galaxy flyer,

Are you authorized to fly this specific approach you describe without displaying any VOR/DME information in addition to the FMS data? Are you authorized to fly this approach even if the radioaid is u/s?

If you are displaying VOR/DME info for monitoring then you are flying a perfectly normal VOR/DME approach, which happens to be executed by the FMS data base and crosschecked with the radioaid and baro alt as the primary means of navigation.

Stratobus,

Well, then again interviewer should make question more specific, stating clearly that he is referring to NPAs without radioaid referrence. But again the ILS thing makes the answer to his question deffinetely: "irrelevant". Sorry.

"Not simply " it is irrelevant" it is definately "relevant" from what even you say"

I said that above 0.3 or 0.5 respectively you will have "Accuracy Low", in other airplanes the approach light on the CDU will not come on. Despite that if you have a positive accuracy (radionavaid croschecking accuracy better than 1n.m.) you can still stay in NAV and monitor radionavaid. How did you come to that conclusion that even from what I say RNP is relevant?

No mate, you're out of date. PBN is formalised and has replaced the previous RNP standards.

http://pbnwbt.ecacnav.com/pbn_packag...t3_pg1_rgt.gif

FE Hoppy:

Did I say differently? What I said was that all RNP is RNAV and all RNAV is PBN, except for some RNP AR missed approach procedures (single string only), which can miss to a VOR, NDB, or just simply fly a heading. This presumes a failure of the GPS (GNSS) system, which is a mandatory part of RNP AR procedure design.

From the current U.S. AIM:

a. General. RNP is RNAV with on-board navigation monitoring and alerting, RNP is also a statement of navigation performance necessary for operation within a defined airspace. A critical component of RNP is the ability of the aircraft navigation system to monitor its achieved navigation performance, and to identify for the pilot whether the operational requirement is, or is not being met during an operation. This on-board performance monitoring and alerting capability therefore allows a lessened reliance on air traffic control intervention (via radar monitoring, automatic dependent surveillance (ADS), multilateration, communications), and/or route separation to achieve the overall safety of the operation. RNP capability of the aircraft is a major component in determining the separation criteria to ensure that the overall containment of the operation is met.

The RNP capability of an aircraft will vary depending upon the aircraft equipment and the navigation infrastructure. For example, an aircraft may be equipped and certified for RNP 1.0, but may not be capable of RNP 1.0 operations due to limited navaid coverage.

b. RNP Operations.

1. RNP Levels. An RNP “level” or “type” is applicable to a selected airspace, route, or procedure. As defined in the Pilot/Controller Glossary, the RNP Level or Type is a value typically expressed as a distance in nautical miles from the intended centerline of a procedure, route, or path. RNP applications also account for potential errors at some multiple of RNP level (e.g., twice the RNP level).

(a) Standard RNP Levels. U.S. standard values supporting typical RNP airspace are as specified in TBL 1-2-1 below. Other RNP levels as identified by ICAO, other states and the FAA may also be used.

(b) Application of Standard RNP Levels. U.S. standard levels of RNP typically used for various routes and procedures supporting RNAV operations may be based on use of a specific navigational system or sensor such as GPS, or on multi-sensor RNAV systems having suitable performance.

(c) Depiction of Standard RNP Levels. The applicable RNP level will be depicted on affected charts and procedures.

Aristoclis

In FAA, display of the underlying navaid is NOT required, all done on FMS data. If display is not required, no need for the navaid to be on the air, either. It is still a VOR/DME approach flown with an overlay. The FMS must show APP, indicating the RAIM is good and scaling is appropriate. This is according to AFM, manufacturer and training establishment.

Aterpster. Any inputs on flying overlay approaches?

GF

GF:

Quote:

---

Aterpster

---

In the U.S. Joe Aviator can only fly them with his TSO 129 or 145/146 navigator if the chart says "VOR/NDB or GPS." Unless the IAP says that, the procedure will not be in his database as an LNAV IAP; rather an advisory IAP with no approach mode.

The high-end FMS stuff is much more varied and complex. There is overlay without it being authorized on the VOR/NDB chart. That becomes a matter of OEM, state, and aviation authority authorization.

Suffice it to say, some biz jets (which is what I work with these days) can fly a VOR or NDB IAP without "..or GPS" in the title. And, so long as the RNP value is met for LNAV overlay, that seems to me to be better than flying the raw data.

I believe others here have said most of the modern air carrier birds have the same ability, provided all the authorizations are there.

I am always learning. :)

When I flew the 767 before GPS, we used LNAV for VOR or NDB, but with the PNF monitoring raw data.

Aterpster

Thanks, that is my experience, Global Express and Challenger 605. We have th have APP or GPS APPR showing to pass the FAF. The Rockwell Collins system has a VGP function for APPR with VNAV, then the path acts like a glide slope with the altitude selector set for missed approach altitude.

GF

If I go into the database, activate a VOR/DME approach to our home drome, what kind of approach am I flying, if I arm LNAV/VNAV and fly it with FMS data displayed? I would offer that it is a VOR/DME overlay. The approach was designed to TERPS NPA standards, it is flown with a CDA to a MDA.

The approach has no specified RNP value, it was not designed to RNP or PBN standards, it is not termed RNAV or RNP, it is not charted as such. Yes, this is certified, it is trained this way, we are checked flying ground-based approaches this way.


Any thoughts?

It doesn't matter which type of approach you activate in your FMS, what matters is what you are using as a primary reference. If you are flying an NDB or VOR approach then you must have the radio tuned and displayed as your primary reference. It then doesn't matter what is in your FMS, in fact your FMS could blow up in your face and you are still able to fly the approach.

If you are using the FMS as your sole reference it doesn't matter what the approach is called in the box. It could be called the moon7 approach, but if you are using the FMS as the primary reference then you must comply with the same procedures as an RNAV approach. Why? because you are using the FMS as a reference.

Why do you think they have all those procedural and certification requirements for RNAV approaches, but wouldn't have them for an overlay when you are using the same reference?

You either fly a VOR approach, or you fly an overlay approach. They use the same profile, they use the same approach plate, but the biggest difference you seem to be missing is that they use entirely different references. Using the VOR has its requirements, and using FMS has different requirements that are the same for standalone RNAV approaches.

engfireleft

As I said, that is NOT true. One, with FAA approval, can do so with the proper equipment. There is no requirement on a Global or Challenger (ProLine 4 or 21) to tune, display or monitor the underlaying navaid. Obviously, you must have and use a current database, have the crew training, and have the correct annunciations. There is no RNP associated with the underlying approach, so no need for a specified RNP. We just need to have APPR annunciation, indicating proper RAIM calculations and, at least, 1 nm scaling.

With 2,000 hours in these types, I understand what navigation sources are being used or not. It is a matter of regulatory approval. Here is the relevant part of AC 90-94

It is OBE, but does apply for systems approved under it.


GF

this conversation is getting interesting!http://images.ibsrv.net/ibsrv/res/sr...ies/thumbs.gif

I'm curious which Boeings you're referring to. I'm on the 777 now, and have flown the 757/767 previously. The approaches are flown in these airplanes just as I described (below)

...Boeing airplanes have two different buttons to hit to commence the approach, and which button you hit depends on what kind of approach you're doing. If you're doing an ILS approach (autoland or not) you hit the APProach switch. That connects the autopilot and/or Flight Director to the LOC and GS. If you're doing a RNAV approach, you hit the LNAV button, which does NOT connect the AP/FD to the LOC/GS