Looking for a guide or tutorial for RNAV, RNP and other approach types.
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With the Autopilot system having its V-NAV mode U/S (unserviceable), im looking for a guide or tutorial for conducting RNAV approaches. I am finding that without proper Vertical guidance on approach that the pilot workload is way too high in adverse weather conditions to keep looking at an approach plate/chart. (high gusting winds - causing speed fluctuations, vis down to minimums, etc).
any suggestions or work arounds would be aprecated.
Thanks in advance.
-Pete -
@Davidaa sorry but the statement that the 146 is not approved for RNP (RNAV) approaches seems to be incorrect.
The 146 and its crews here in Australia and elsewhere, regularly conducts these types off approaches down to minimums. Australia doesn't have ILS systems installed everywhere like in Europe or America, so the use of RNP non precession approaches is extremely common at most airports. That includes airports like YPAD (Adelaide international) or YSCB (Canberra international) where there is only a single approach with an ILS.
ide also note that in australia GNSS approaches used by smaller aircraft have their own approach plates that have different minimum requirements.
I refer you to two separate documents that could not exist of the 146 was not approved for these kinds of approaches.
1, This Australian Transport Safety Bureau (ATSB) report of a incident regarding a BAe 146 200 that was conducting an RNP approach:
https://www.atsb.gov.au/publications/investigation_reports/2024/report/ao-2023-004#aircraftdetails10
2, This Paper produced by the UK's CCA: CAA PAPER 2007/06 RNAV (GNSS) Non-Precision Approach –
Flight Trials Analysis Report. this paper lists the 146 as one of the aircraft sampled that used an RNAV approach.
https://www.caa.co.uk/publication/download/13505 -
RNAV and RNP are not the same! I think the 146 is capable of RNAV but not equipped for RNP. Please correct me if I am wrong.
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@Rhinozherous from the first link i included in my reply above:
" air traffic control cleared the flight to track to the waypoint SARUS. This waypoint was the initial approach fix for the required navigation performance (RNP) approach for runway 33 at Rockhampton and the tracking allowed the crew to proceed directly from the cruise and descent to a straight-in RNP approach"That is in fact one of the reasons why the 146 has a "VNAV" button on the autoflight panel. it is used primarily for providing vertical guidance on RNP approaches.
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So firstly I’d it a 146 or an RJ? Also the RNAV capability is largely defined by the FMS fitted to the aircraft and also depending on the certification standard the displays, eg glass cockpit. Certification standards may vary across the globe and dispensations may also apply. But as a general rule 146’s are not/were not capable of RNP approaches. There may be a few aircraft which have been upgraded to facilitate this.
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The appropriate procedure would be to divert to an alternate with suitable conditions. You're flying a '90s era (best case) bird without VNAV into highly adverse conditions on an approach you aren't remotely equipped for. Solo. I think that's usually the point where all the holes of the cheese line up and the sad music starts.
The procedure you can follow is to use the GPA table on the approach chart (or do your own calculations) and maintain GS and VS to achieve the GPA after the final descent fix. You would at least need a second set of eyes to monitor the approach under those conditions; i.e., have an eye on vertical and ground speed and check your heights at the documented distances to make corrections on the fly.
And to let out my facetious self: yes, the simulated 146 can fly RNP approaches. All that means is that your plane is sure enough of its lateral position in space at any given time, and so far I'm confident it always is as long as you're navigaing with the FMS. What the plane cannot do is fly an automated final approach, which isn't part of that. What you probably cannot do is maintain a glide path to the necessary standards.
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Bin Chicken.
The JF146 models don’t include a VNAV button as to do a RNP requires the correct type of FMS and database of airfield approaches. The early model UNS is not a normal FMS for the 146. Quite possibly the GNS XLS Enhanced may be required to do RNP.
Fitted ann upgraded FMS as part of an approved mod. Would also prompt the inclusion of a VNAV button.
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I have it on good authority that the Australian 146 aircraft of which your write are fitted with the Universal SCN 1001.X, and are now RNAV and RNP approved.
Quite different equipment from the UNS 1 series.
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@Driver-Airframes thanks! that makes sense.
Maybe it could be an idea for JF to filter out approach types that the A/C can not do in the FMC code or something. -
You are welcome Bin Chicken. It would be normal for aircraft in service to have the availability of approach options tailored to the particular aircraft’s equipment fit.
To be fair to JF, that is impossible with so many different aircraft types and equipment fits available.
It would be an idea that the limitations of FMS v aircraft type/equipment fit could be better publicised to users, but I afraid that requires knowledge of the real world of aircraft operation. I don’t think any blame should be made of the JF product - on the whole it’s all very realistic.
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I had been wanting to ask this question. I flew into KCHS on VATSIM in the 146 the other night. They were running the RNAV Z approach, and I had to make a quick and dirty modification to my equipment code (I ended up with /L, which in the US means advanced RNAV+RVSM), so the controller told me to expect it. I was using the UNS, and I was uncertain enough about the capabilities that I asked for the ILS instead.
In the US, we have RNAV(GPS) and RNAV(RNP) approaches. I'm certain that the RNP ones are right out, but assume we can use the GPS ones with LNAV only?
I definitely need to go update my VA's simbrief profile with a different ICAO equipment code selection to reflect the UNS-1 now instead of the 146s flying around /A.
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Hi jmarkows. That question opens a Pandora’s box!
The phraseology and naming of approach types for the equipment has changed several times during the past 25 or so years. It doesn’t help that the USA have their own designations and that the 146 did not use the UNS 1. Normal equipment fits used to be Trimble or GNS, GNS-X, GNS Enchanted. The Universal SCN 1001.X system raised the bar by introducing certification that improved the RNAV capabilities and introduced RNP capability AND Automatic Dependent Surveillance.
I have used versions of the UNS 1 on other aircraft. As with the GNS-X it was capable of what used to be termed BRNAV - that is point to point NAV using GPS input along airways, SID, STARS. The UNS I’s that I used was also capable of VNAV approach too, but there were limitations - but don’t ask me what they were - not quite ILS limits though.
But it’s not just about the FMS type as to what the aircraft is capable of. There is also the requirement for integration and certification with the aircraft type, pilot training, and company approval.
I would suggest that the equipment would be capable ‘in simworld’ of airways, SID, STARS and possibly lateral navigation such as an overlayed VOR/NDB/LLZ approach with vertical profile flown as a continuous descent approach (CDA) using V/S mode.
BTW, you mention RVSM in passing. I think only one 146 is operated as RVSM capable. The primary reason for this that the type (apart from the above mentioned aircraft) is certified for 30,000 (original aircraft delivered to Australia is 31,000). Getting there is a struggle at high weights and temperatures! Went there a few times for the tailwinds (pre RVSM days) and I don’t think we saw more than 210 kts IAS until descent… Oh happy days.
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@Driver-Airframes I did mention RVSM, yes; I realize it's not really RVSM compatible, I just needed a quick change to my equipment code on VATSIM. In the US anyway, it still uses the single FAA equipment code, so I threw a /L out there since my VA's Simbrief profile (and thus what I filed) is only /A, which is no RNAV at all, only traditional radio nav. I never used the CJ4 Mod FMS; it was nothing until the release of the UNS-1. Having had time to look into it more, a better fit in the US system would likely have been /I; Basic RNAV with a Mode C transponder, but not RVSM capable. /G would also be an option, as that's Advanced RNAV with a GNSS and Mode C, but I wasn't sure if that would imply the sort of vertical guidance that I know the UNS-1 does not have. You can do LPV approaches with an appropriately augmented GNS530, for instance, but not the UNS as far as I can tell.
As for the raw ICAO equipment codes, if I might pick your brain a bit, I currently have "SDFYZ" as the ICAO equipment types loaded into the profile. I believe for the UNS-1 I would only need to add G to the list? I also finally looked up the ATC PBN codes and they're all fouled up in my profile, as well. Pretty sure I'm advertising a radio-nav only plane capable of RNP-quality positioning 😂
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I’m sorry to say that although I worked in OPS it was back in the day of the telex machine, and airline pilots today are normally involved in filing their own flight plans - thank goodness!
I the FAA cheat is here: https://www.faa.gov/sites/faa.gov/files/FAA FPL Quick Reference Brochure (2022-09-15).pdf
I don’t think you need a ‘G’.
