Pilot Discussion With a Global Perspective
By Jan Naslund 812053
#522224 Hi,

I am wondering about which flightplan equipment code i should choose when fining a flightplan on Vatsim.
https://www.vatsim.net/pilot-resource-c ... pment-code

I know that RVSM only applies from FL290 up to FL410 and when i fly a Boeing 737 or other high flying aicraft i usually choose letter L (RVSM, GNSS, Transponder with mode C). These aircraft usually have LNAV and VNAV capability and i can accept an RNP approach for example and also a SID/STAR with vertical limits.

I am a bit confused about what letter to choose when i fly a low flying aircraft and aircraft that has LNAV but does not have VNAV guidance capability. I of course can not accept an RNP approach but i can follow an RNAV SID/STAR and handle the vertical navigation manually. Does this mean i am RNAV capable in the Vatsim equipment code table?

Also, what is the difference between RNAV and GNSS capability in the Vatssim equipment code table?

I want to know because there are approaches denominated RNAV(GNSS) and they seem to have different minima depending on if the approach is flown using VNAV or only LNAV (Manual vertical navigation) so iam suspecting that:
RNAV is only really LNAV? and GNSS is LNAV and VNAV (Vertical navigation)?

Also, is there a difference in equipment code letter selection if i am receiving vertical guidance for an approach (ILS for example) or if i can program the aircrafts avionic system to perform the approach?

Best Rgs / Jan
By Simon Kelsey 810049
#522241 Hi Jan,

First things first:

GNSS stands for Global Navigation Satellite System and is simply the generic term for satellite-based navigation systems (GPS is the 'brand name' of a specific system -- the US Navstar Global Positioning System -- this was the first such system, but since then there have been other developments such as the EU's Galileo, Russia's GLONASS, China's BeiDou as well as other regional systems, so there was a need to move to a generic term that encompasses all such systems).

RNAV stands for Area Navigation and refers to the ability of the aircraft to navigate from point to point independent of ground-based navigation beacons (i.e. VOR/NDB). There are many such systems which provide this capability, but in general most rely on some form of inertial system, and/or GPS. Most aircraft built since about the mid-90s are equipped with GPS receivers which feed in to the Flight Management System, but some (and particularly pre-90s built aircraft) are only equipped with IRS/INS. For example, some early A320s, 767s and 747-400s were not GPS equipped.

All of this is independent of your aircraft's approach capability.

So the question is - is the aircraft you are flying equipped with GPS (in which case in practical terms on VATSIM you will either be using /L or /G) or not, in which case you will either be /Z or /I.

For example, something like an old 767 with no GPS would be B763/Z (as it is RNAV capable, but not using GNSS) whereas a more recent B747-400 with GPS would be /L.

If your aircraft is not RVSM certified (which is only going to be a) old/vintage aircraft or b) aircraft which have a ceiling below FL290 anyway then the same logic applies -- again, something like a C172 might be /A (strictly speaking, it can only be /G if the GPS is fully integrated in the aircraft equipment, such as a G1000 type installation: handhelds don't count).

Moving on to your question about approaches...

The title of an instrument approach procedure normally tells you the equipment required to fly that procedure (e.g. VOR/DME, ILS etc etc). In this case, RNAV(GNSS) means you must have both RNAV capability and be GNSS equipped -- unless there is a note on the chart which says that some other form of sensor is permissible (usually an FMS with DME/DME position updating capability which allows those slightly older non-GPS equipped 767s etc to fly such approaches).

When it comes to the minima, LNAV/VNAV requires you to have an approach-certified Baro-VNAV system. If you don't have this, you can only fly to the LNAV minima. Another situation where you might only be able to fly to the LNAV minima is if the temperature is below the limit stated on the chart: if this is the case you cannot use the LNAV/VNAV minima and must instead manually temperature-correct the step-down altitudes and fly only to the LNAV minima (although, confusingly, there is nothing stopping you using VNAV as an autopilot mode).

In any event, there is no difference in your equipment suffix. I'm not sure how the FAA handle it, but in ICAO land your approach capability is noted in the flight plan remarks field under the PBN field which allows entry of codes for each phase of flight; for example, PBN/A1B1D1O1S2 -- A1 means RNAV10 capable (an Oceanic specification) B1 means RNAV5 enroute capability, D1 means RNAV1 terminal capability (i.e. able to fly RNAV1 SIDs and STARs), O1 means RNP1 (subtly different to RNAV1) and S2 means RNP approach with Baro-VNAV (i.e. LNAV/VNAV minima). Note that this does not mean RNP AR approaches -- which are T1 (with RF capability) and T2 (without RF capability). https://www.icao.int/safety/FITS/Docume ... 010_18.pdf provides full details.

Hope that helps!
By Andreas Fuchs 810809
#522250 To make it short, if you are flying around with a current model like a B737NG, A320-family, B747-400, B777 etc.. then you should be able to follow PBN procedures with sufficient accuracy. That would be /L .
By Don Desfosse 1035677
#522252
Jan Naslund 812053 wrote:I am a bit confused about what letter to choose when i fly a low flying aircraft and aircraft that has LNAV but does not have VNAV guidance capability. I of course can not accept an RNP approach but i can follow an RNAV SID/STAR and handle the vertical navigation manually. Does this mean i am RNAV capable in the Vatsim equipment code table?

The advice you've gotten is very good. As an example to help answer your question, above, say you were flying a King Air, Baron, Skyhawk etc., with the default GNS530 (and of course assuming Transponder with Mode C), you'd file /G.
By Matthew Kosmoski 891361
#522258
Magnus Meese 997444 wrote:Except, of course, King Airs can be RVSM equipped and thus file /L.

(Technically correct, the most annoying type of correct)

And on VATSIM, we assume all aircraft are RVSM capable since we don't have the ability to certify airframes or crew ;-)
By Don Desfosse 1035677
#522266
Magnus Meese 997444 wrote:Except, of course, King Airs can be RVSM equipped and thus file /L.
(Technically correct, the most annoying type of correct)


Good point; hadn't considered that --- none of the King Airs I used to fly were, and hadn't considered they could be.

Matthew Kosmoski 891361 wrote:And on VATSIM, we assume all aircraft are RVSM capable since we don't have the ability to certify airframes or crew ;-)


:)
By Magnus Meese 997444
#522282
Matthew Kosmoski 891361 wrote:And on VATSIM, we assume all aircraft are RVSM capable since we don't have the ability to certify airframes or crew ;-)

There are people flying gliders on VATSIM, gliders can reach altitudes at and above RVSM altitudes if riding on mountain waves. Considering this, all gliders should file RVSM-codes on VATSIM, QED. :D
By Jan Naslund 812053
#522312 Thanks Simon and everyone else for contributing.

I found that on some charts that are called RNAV(GNSS) or RNAV(GPS) used in the US i think, there are different minima for LNAV only or full VNAV capablilty so the RNAV approach can be flown without VNAV capability but as Simon said, you have to adjust minima for temperature.

The codes Simon refers to are different from the ones i was thinking about that are stated here: https://www.vatsim.net/pilot-resource-c ... pment-code

Ther are other codes that people put in the comments section to indicate their navigation capability. Found this list:

Other reasons for special handling by ATS shall be denoted under the designator RMK/. PBN/ Indication of RNAV and/or RNP capabilities. Include as many of the descriptors below, as apply to the flight, up to a maximum of 8 entries, i.e. a total of not more than 16 characters.
A1 RNAV 10 (RNP 10)
B1 RNAV 5 all permitted sensors
B2 RNAV 5 GNSS
B3 RNAV 5 DME/DME
B4 RNAV 5 VOR/DME
B5 RNAV 5 INS or IRS
B6 RNAV 5 LORANC
C1 RNAV 2 all permitted sensors
C2 RNAV 2 GNSS
C3 RNAV 2 DME/DME
C4 RNAV 2 DME/DME/IRU
D1 RNAV 1 all permitted sensors
D2 RNAV 1 GNSS
D3 RNAV 1 DME/DME
D4 RNAV 1 DME/DME/IRU
RNP SPECIFICATIONS
L1 RNP 4
O1 Basic RNP 1 all permitted sensors
O2 Basic RNP 1 GNSS
O3 Basic RNP 1 DME/DME
O4 Basic RNP 1 DME/DME/IRU
S1 RNP APCH
S2 RNP APCH with BARO-VNAV
T1 RNP AR APCH with RF (special authorization required)
T2 RNP AR APCH without RF (special authorization required)


So maybe for the aircraft below i should file No RVSM, RNAV, No GNSS, Transponder with mode C (Letter I) and then state in the comments my real capability. It's quite confusing!

Only problem is that i am not sure what the ddifference between GNSS and RNAV actually is. Is GNSS that i have vertival nav capability as well or is it something else entirely?

One low level aircraft i am flying is the Piper Arrow with altitude holding autopilot coupled to a Garmin 530. Climbs and descents have to be done manually. It has a DME. With the Garmin 530 i can fly RNAV routes and i can fly an RNAV SID's and STAR's but i would have to control climbs and descents manually. What letter should i choose?

Another aircraft i fly is the Pilatus PC-12. It can reach FL300. It also has a Garmin 530 (same as in the Piper) but it also has a more advanced autopilot where i can set the climb/descent rate or the climb/descent IAS. Very nice! It also has a DME.
If i file FL280 or below for a flight, which letter should i choose?
If i file FL290 or FL300 for a flight, which letter should i choose? (RVSM starts at FL290)

Best Regards / Jan
By Simon Kelsey 810049
#522317 Jan,

As I said:

All of this is independent of your aircraft's approach capability.


All enroute RNAV specifications are 2D only. Therefore it doesn't matter whether you have VNAV or otherwise capability, the question is whether the equipment you have fitted (which strictly speaking to qualify must be part of the aircraft's permanent avionics fit; if you can couple the autopilot to it this should qualify) is capable of meeting enroute RNAV specifications (i.e. BRNAV). The FAA equipment code is a very blunt instrument; the ICAO standard allows for finer specification, plus the PBN/ and NAV/ remarks to define precisely what the aircraft is capable of.

With the Garmin 530 i can fly RNAV routes and i can fly an RNAV SID's and STAR's but i would have to control climbs and descents manually. What letter should i choose?


If you can fly RNAV routes then you are RNAV capable.

The GNS 530 is GPS-driven, so you are RNAV capable with GNSS capability.

Are you RVSM capable? In an Arrow, I doubt it -- the basic requirements being:

Two independent altitude measurement systems;
An altitude alerting system;
An automatic altitude control system; and
A secondary surveillance radar (SSR) transponder with altitude reporting system that can be connected to the altitude measurement system in use for altitude keeping.
(IR-OPS SPA.RVSM.110, EU-OPS 1.872)


So the answer is /G.

Another aircraft i fly is the Pilatus PC-12. It can reach FL300. It also has a Garmin 530 (same as in the Piper) but it also has a more advanced autopilot where i can set the climb/descent rate or the climb/descent IAS. Very nice! It also has a DME.
If i file FL280 or below for a flight, which letter should i choose?
If i file FL290 or FL300 for a flight, which letter should i choose? (RVSM starts at FL290)


It doesn't matter what altitude you file, the code refers to the installed equipment. An A320 would still be RVSM capable whether you choose to fly it at FL350 or VFR at 2000 ft.

The PC-12 may be RVSM capable; some brief research suggests that newer models are certified, whereas older models had an equipment upgrade option that enabled it. If your model is so equipped, then the answer is /G and you are effectively limited to max FL290 as you are simply not permitted in RVSM airspace unless you are RVSM certified. If your model is so equipped, then /L is appropriate.

From a practical point of view, ask yourself:

- Can I accept a direct to a non-conventional waypoint?
- Can I fly an RNAV SID or STAR?

If the answer is yes, then you should file an RNAV equipment code. The only remaining question is whether the aircraft is RVSM certified, which with the GA-type aircraft you are flying is often going to depend upon the actual equipment fitted to that particular aircraft and therefore some more individual research will be required compared to obviously RVSM capable types like airliners or obviously non-RVSM capable aircraft such as Cessna spamcans. As a general rule, I would expect any modern high-performance GA type with an advertised service ceiling above FL290 to be RVSM capable.
By Andreas Fuchs 810809
#522319 Hi Jan,

this entire topic of PBN is complex, because there are so many different types of it.

Basically, all charts SHOULD be labelled RNP RWY xy, but chart manufacturers have a grace-period until December 2022 when they will have to comply. Whether you read RNAV(GNSS) or RNAV(GPS) or RNP: it is all the same!

From now on I will use the term "RNP approach" only, but you have to be aware of the previous paragraph regarding the chart naming conventions.


RNP approach LNAV
Your plane will follow the horizontal portion of this RNP approach only based on FMS/GPS-data, there is NO vertical guidance. Instead you will have to use a conventional vertical mode such as "VS" or "PATH" (if available) to follow the vertical profile of the approach. As a consequence you can only use the minimum depicted as "LNAV". You may want to add 50ft to the LNAV-minimum to account for height loss in case of a go-around to avoid undershooting the official LNAV-minimum. Many operators, including mine, do this.


RNP approach LNAV/VNAV | APV (Baro)
Your plane will follow the horizontal portion of this RNP approach based on FMS/GPS-data, but it also provides vertical guidance. You have to use VNAV or a similar vertical mode (possibly called "VGP") on your type of aircraft to follow the vertical profile of the approach. Use the minimum depicted as "LNAV/VNAV". You do NOT have to add 50ft, since the minimum will already cater for an altitude loss during missed approach.
Since the vertical channel of this type of approach is based on barometric data, it will be affected by low temperatures and approach charts will depict the minimum temperature that it can used at. Temperatures well below ISA-values require a correction of the minimum and of the final approach altitude.
Should the temperature is below the limit, you can fall back to RNP approach LNAV and you will be responsible to follow the correct vertical profile with a conventional vertical mode (VS or PATH).

This type of approach is also called APV: APproach with Vertical Guidance and since it uses a barometric vertical channel the complete name is APV (Baro) approach.


RNP APCH LP
RNP approach with Localizer Performance.
Its increased accuracy comes from the fact that it has additional equipment called SBAS, Space Based Augmentation System: ground based satellite receivers compare their known positions with the measured GPS-position, calculate the difference and send this error signal via a geostationary satellite to aircraft. This enables them to produce a very accurate GPS-position.

This approach will provide you with precise horizontal guidance from your FMS/GPS, but NO vertical guidance.
Instead you will have to use a conventional vertical mode such as "VS" or "PATH" (if available) to follow the vertical profile of the approach. You may want to add 50ft to the LP-minimum to account for height loss in case of a go-around to avoid undershooting the official LP-minimum. Many operators, including mine, do this.


RNP APCH LPV
RNP approach, Localizer Performance with Vertical guidance.
This approach also requires an SBAS to be installed. This approach will provide you with precise horizontal guidance from your FMS/GPS and vertical guidance. Its vertical channel does NOT use barometric data, but GPS-data - it is therefore a "geometric approach" and does not suffer from temperature-errors and its vertical channel based on GPS is more precise than a barometric one.
Consequently you do NOT need to add 50ft to the depicted minimum.


RNP (AR) APCH
These approaches are a development from RNP APCH. They provide a high level of navigational performance (accuracy 0.3 to 0.1 NM) and will allow curved approaches to be flown to low minimums.
To use them, specific authorization from the authorities is required. On charts they should be labelled as RNP RWY xy (AR), but older charts can show them as "RNAV (RNP) Rwy xy".


RNP GBAS
GBAS stands for Ground Based Augmentation System. Basically, a GBAS consists of ground based GPS receivers in the vicinity of airports that will compare their known position to the measured GPS-position, calculate an error-value and transmit it directly to aircraft by means of an VHF-signal. Officially the range of this signal assured up to 23 NM from the transmitter.
Due to its high accuracy, RNP GBAS approaches can be flown down to CAT I minima (eventually also CAT II and III), enabling pilots to perform true precision approaches.
RNP GBAS approaches can also be called GBAS Landing Systems: GLS.


That was a lot, wasn't it?
By Simon Kelsey 810049
#522321
Jan Naslund 812053 wrote:Only problem is that i am not sure what the ddifference between GNSS and RNAV actually is. Is GNSS that i have vertival nav capability as well or is it something else entirely?


No, as I tried to explain above -- in simple terms GNSS simply = GPS.

GPS is a brand name (Hoover). GNSS is a generic term (vacuum cleaner). Official documents are replacing the brand term 'GPS' with the generic term 'GNSS' simply because there is now more than one type of satellite based navigation system in operation. GPS is one particular system run by the US Government, but with many other nations now having the capability to put satellites in to orbit there are now other 'competing' systems run by other states (e.g. Russia, the EU, China etc).

GNSS/GPS = one of several ways for the aeroplane to know where it is without reference to ground-based navaids.
RNAV = the capability through a suitable navigation system to route direct from point to point without reference to ground-based navaids.

In other words, GNSS/GPS just tells you where you are. To make use of that, however, you need a system which can compute a path to a different position and navigate the aeroplane along it. However, such a system does not necessarily need a GPS input specifically to know where the aeroplane is in the first place: that position could just as easily be provided by, for example, an inertial reference system which, after being told by the pilot precisely where it is to start with is subsequently able to work out the aircraft's position internally without any external reference at all. Using an IRS-based position calculation alone, however, is less accurate than a system that uses input from a GNSS, and therefore such aircraft are unable to achieve the level of accuracy needed to fly certain procedures, hence the different equipment code.

Does that make sense?
By Lindsey Wiebe 1101951
#522373 Wow! A lot of great information in this thread! Definitely worth a sticky for training. Some people may not care about this level of detail but as you learn more and more you may get curious, or (like me) are a RL pilot you know the basics already. But these little details are a little confusing and you'd like to know them for sure instead of "kind of" know them. :wink: