SID / STAR & RNAV SID / STAR difference - choosing a correct equipment suffix

[Ivan Tahlin]

Hello everyone,

 

I have gathered some time flying on VATSIM over the last year (approximately 60 hours), however, I still consider myself a newbie. For some time there has been one issue bothering me, and I am hardly able to find an answer for it online. It is the difference between "normal" SID / STAR procedures provided within the charts and the RNAV SID / STAR procedures, choosing the correct equipment suffix for the aircraft I fly with, in order to let the controller know if I am able to proceed via FMC or I need vectors, and eventually how to know which procedure to use. I will show a real example beneath, to easily elaborate what is interesting me the most.

 

I mostly fly Aerosoft's A320 / A321 Extended (not the Profesional version which has complete SID / STAR support) Steam Version on FSX. My most recent VATSIM flight plan was from LDDU to ULLI. Now here is where my confusion begins. LDDU within its charts has listed two types of SID and STAR procedures: just SID / STAR and RNAV SID / STAR. I am able to enter only "normal" SID / STAR procedures into my Aerosoft's A320 FMC, but I am not, however, able to choose any of the RNAV procedures listed within the charts. Arriving into ULLI, I saw that according to its charts, it is only possible to initiate approach via RNAV STAR procedures and that if the aircraft does not have GNSS equipment on board, it needs to request vectoring from ATC, or in case of high traffic density might even be denied to enter the controlled airspace... That wasn't the issue as there was no active ATC at the time so I flew in manually under UNICOM. In my FMC I was able to enter STAR procedures that are even not on the charts anymore, assuming that my FMC has old AIRAC cycle data installed, as even the numbers of SIDs & STARs are mismatching, and the last waypoint of my flight plan, also beginning of the STAR didn't exist, and I had to enter it manually by coordinates. I am mostly interested into what is the correct equipment suffix according to VATSIM's table below for my aircraft so that the controller will know I need vectoring to final when arriving into an airport that has only RNAV procedures listed within its charts.

 

According to my newbie understanding, my Aerosoft A320X should be able to keep RVSM during flight and it does have Transponder with Mode C (please correct me if I am wrong). Now, does the aircraft's ability to execute only normal SID / STAR procedures, but not RNAV SID / STAR procedures mean it DOES have RNAV, but DOESN'T have GNSS - in that case, correct suffix would be Z, or it DOESN'T have any of these - in which case the correct suffix would be W or am I perhaps understanding this completely wrong and it is another equipment that I have onboard? Will the controller even recognize this himself, or do I have to request vectoring when contacting him? 

 

Secondly, as mentioned above, I am however able to enter non-existing waypoints into my FMC, meaning that technically, I could manually enter designated STAR's waypoints by coordinates into my FMC with all the corresponding altitude and speed restrictions. However, as taught by VATSIM's training, since I mostly fly in Europe, I should choose the correct landing RWY and arrival route or STAR just before initiating descend (before descent preparation checklist, as it requests reviewing landing data). This "manual STAR entry" is time-consuming, and could mean that by the time I enter it completely, active landing runway may have already changed, and then I can't just click another STAR within my FMC as I could if I would have had RNAV GNSS onboard, but have to instead enter everything again, as some airports, like the above mentioned ULLI, have different RNAV STARs for different runways. Could this manual RNAV SID / STAR entry be feasible and doable, or should I just ask for vectoring with a risk of being denied entry into controlled airspace and be told to turn around?

 

Thank you all for your time and understanding reading and reviewing my question, and please correct me if I am wrong somewhere in understanding this topic. I appreciate any help you could provide me. Thanks a lot once again, and have a nice day 😀

[Nils Dornbusch]

So first of all all modern airliners are rnav and gps equipped. So I don't know what is happening in your addon. Conventional sids/stars are only used like 727s or small old GA planes. 

Also you should choose the correct equipment type but not every controller will look at it. If you have a modern aircraft you will always get the rnav sids/stars assigned. But of course you can always say that you are unable and that you request vectors. That's happening to guys with old nav data as well. 

Edited July 24, 2020 at 07:44 PM by Nils Dornbusch

[Ivan Tahlin]

44 minutes ago, Nils Dornbusch said:

So first of all all modern airliners are rnav and gps equipped. So I don't know what is happening in your addon. Conventional sids/stars are only used like 727s or small old GA planes. 

Also you should choose the correct equipment type but not every controller will look at it. If you have a modern aircraft you will always get the rnav sids/stars assigned. But of course you can always say that you are unable and that you request vectors. That's happening to guys with old nav data as well. 

After some resarch I can see that you were right indeed, it is the problem with the addon as I am running AIRAC cycle 1511 all the way from October 2015 😂 Apparently I just have to upate via NavDataPro or Navigraph 😃 Thank you for your help though 😉

[Tobias Dammers]

RNAV means that your navigation equipment can follow arbitrary flight paths with sufficient accuracy. The navigation information for this can be based on a variety of sources: GPS/GNSS, classic ground station based area navigation (which is where the term "RNAV" comes from), etc.; it is generally augmented with inertial navigation equipment for faster responses and better precision. RNAV procedures are mainly defined as sequences of waypoints, each given as a lat/lon pair.

Traditional, non-RNAV, procedures, by contrast, assume navigation equipment that can only perform limited navigation based on ground stations (NDB, VOR, DME), and defines the flight path based on headings to or from a station, radials, and DME readings. Enroute, non-RNAV aircraft can fly VOR-to-VOR, or on airways that follow VOR radials (in the latter case, you fly on one radial until intercepting another, and the interception point is your waypoint).

For VATSIM purposes, two things are important:

• Whether you are able to fly published procedures at all (which requires having the published information available, and being able to fly the procedures correctly, by whichever means); if you cannot do that, put "NO SID/STAR" in your remarks and/or request vectors.
• Whether your aircraft is RNAV-equipped; if it's not, then ATC should assign you non-RNAV procedures only (and you are required to reject RNAV procedures when offered); if only RNAV procedures are available for the situation at hand, you will have to fly by vectors. Non-RNAV aircraft also cannot fly airways that can't be navigated without RNAV.

IRL, procedures may have additional requirements, e.g.:

• "FMS mandatory", usually because the procedure is so complex and/or time critical that flying it without the aid of an FMS would lead to unacceptably high workload, or human errors would quickly lead to unsafe situations.
• "DME required", on non-RNAV procedures, means that DME equipment is necessary to correctly fly the procedure (e.g. because it involves a DME arc, or because you have to turn to a heading at a specific DME reading).
• "GPS/GNSS required" may apply in areas where insufficient ground station coverage is available to make traditional RNAV possible.

RVSM, then, is completely unrelated to SIDs and STARs; it only matters above FL290. In non-RVSM airspace, separation above FL290 is 2000 ft, so only uneven flight levels are used. In RVSM airspace, however, a vertical separation of 1000 ft is maintained above FL290. In order to safely do this, aircraft need to be specially certified for RVSM; practically all modern airliners are, and on vatsim, it's a non-issue (unless you want to willingly simulate the restrictions that come with flying a non-RVSM-certified aircraft into RVSM airspace, which means you cannot climb beyond FL290 there). RVSM has nothing to do with lateral navigation equipment, it's mainly about altimeter precision and autopilot capabilities.

Anyway, if you're flying a modern airliner, then your navigation equipment is invariably "RNAV, GNSS, RVSM". If you can't fly (all) SIDs / STARs as published, add "NO SID/STAR" to your remarks - your aircraft is still RNAV certified, and you can still use RNAV for your enroute waypoints.

[Ivan Tahlin]

On 7/25/2020 at 7:12 PM, Tobias Dammers said:

RNAV means that your navigation equipment can follow arbitrary flight paths with sufficient accuracy. The navigation information for this can be based on a variety of sources: GPS/GNSS, classic ground station based area navigation (which is where the term "RNAV" comes from), etc.; it is generally augmented with inertial navigation equipment for faster responses and better precision. RNAV procedures are mainly defined as sequences of waypoints, each given as a lat/lon pair.

Traditional, non-RNAV, procedures, by contrast, assume navigation equipment that can only perform limited navigation based on ground stations (NDB, VOR, DME), and defines the flight path based on headings to or from a station, radials, and DME readings. Enroute, non-RNAV aircraft can fly VOR-to-VOR, or on airways that follow VOR radials (in the latter case, you fly on one radial until intercepting another, and the interception point is your waypoint).

For VATSIM purposes, two things are important:

• Whether you are able to fly published procedures at all (which requires having the published information available, and being able to fly the procedures correctly, by whichever means); if you cannot do that, put "NO SID/STAR" in your remarks and/or request vectors.
• Whether your aircraft is RNAV-equipped; if it's not, then ATC should assign you non-RNAV procedures only (and you are required to reject RNAV procedures when offered); if only RNAV procedures are available for the situation at hand, you will have to fly by vectors. Non-RNAV aircraft also cannot fly airways that can't be navigated without RNAV.

IRL, procedures may have additional requirements, e.g.:

• "FMS mandatory", usually because the procedure is so complex and/or time critical that flying it without the aid of an FMS would lead to unacceptably high workload, or human errors would quickly lead to unsafe situations.
• "DME required", on non-RNAV procedures, means that DME equipment is necessary to correctly fly the procedure (e.g. because it involves a DME arc, or because you have to turn to a heading at a specific DME reading).
• "GPS/GNSS required" may apply in areas where insufficient ground station coverage is available to make traditional RNAV possible.

RVSM, then, is completely unrelated to SIDs and STARs; it only matters above FL290. In non-RVSM airspace, separation above FL290 is 2000 ft, so only uneven flight levels are used. In RVSM airspace, however, a vertical separation of 1000 ft is maintained above FL290. In order to safely do this, aircraft need to be specially certified for RVSM; practically all modern airliners are, and on vatsim, it's a non-issue (unless you want to willingly simulate the restrictions that come with flying a non-RVSM-certified aircraft into RVSM airspace, which means you cannot climb beyond FL290 there). RVSM has nothing to do with lateral navigation equipment, it's mainly about altimeter precision and autopilot capabilities.

Anyway, if you're flying a modern airliner, then your navigation equipment is invariably "RNAV, GNSS, RVSM". If you can't fly (all) SIDs / STARs as published, add "NO SID/STAR" to your remarks - your aircraft is still RNAV certified, and you can still use RNAV for your enroute waypoints.

Thank you a lot for your detailed explanation regarding my question and my problem, now many things are much clearer to me 🙂 As mentioned in my answer above, I have troubleshot the problem myself and it was actually the fact that I was running a prehistoric AIRAC cycle 1511 which came preinstalled out of the box with the addon aircraft I am using, and I didn't even bother checking that as I thought it would have come with the newest data already integrated upon purchase and installation. Updating to the newest AIRAC cycle, I was able to select and fly RNAV procedures listed within the charts with no problem. Thank you though for your answer and time, I was really confused about why I was not able to select these procedures and thought it was the problem with an aircraft or equipment I had onboard 😓