rayngwt

A summary for all those who are confused by the lengthly discussion:WAAS(US)/ EGNOS(Europe)/ GAGAN(India)/ MSAS(japan) are all SBAS (space based augmentation systems), augmenting the GPS signals the acft receives. This makes it more accurate. IRS coasting is allowed on RNP-AR approaches depending on certification, of course FDE predictive checks ought to be done prior to operation.LPV minimums are approaches where the aerodrome has GBAS (ground augmentation) and the acft must be capable of receiving these signals transmitted via VHF to the unit onboard to define the non-linear ILS type guidance. Europe is already seeing quite a few in Switz, France etc.

Hi David,Ya, have read that page as well, but I still don't think the acft guarantees a constant angle to the next point, it might do a 'concave' though. Only the vertical path angle coded in the db, and only to the MAP or E/D (aka runway) will ensure a constant angle. Besides, NGx doesn't allow consecutive angles as opposed to arinc424 rules where multiple segment can be programmed. I guess that's just an industry FMS/ARINC harmonization issue.Tks

Hi,I find this subject interesting so I would just like to contribute what I read, although the topic is abt shud one press the APP on an Rnav.A couple of things: (one not related to another)1. I am not sure if Lnav/vnav will maintain the gradient as the acft is on idle thrust descent. It might 'dive/drive' if the wpt constraints are a little far apart. I wud rather use NGX new vertical path function while I 'monitor' the alt-constraints/dme, it is non-precision anyway.2. FMSs with multi-mode recvrs such as the rockwell collins GLU-925 are able to fly GLS. Qantas has been doing this since 2005 on trial with Oz's GBAS system. You select the coded GLS procedure and the 5 digit 'frequency' will correspond a runway GLS 4-letter code in the approach ref page, also in the PFD. A different model NAV panel is also required to enter the 5 digit 'freq'.3. I'm sure u will need GPS on such approaches as it wud hv been mentioned in the notes on the plate. However, if you are using a micro-IRS with a hybrid GPS (with many kalman filters algorithms), there is an available 'coasting time' when u loose GPS, for various RNP-AR such as RNP 0.3 ~25mins (most limiting) ... refer to Honeywell Laseref V product.Just found it useful to add to our knowledge.Ray

Yeah, I know, I hope I don't go below .. say I hit the altitude at all wpts prior and am not 'on top'.Looks like I keep confusing myself with Feelthere wilco data. Guess PMDG data does not contain GPA as per 'database' yet. The last wpt either Rwy or MAP always has a system-calculated angle to it, it does not come from the 'database' and as per mentioned in the FCOM manual, it keeps to the angle till the E/D. Thanks and sorry for confusing you guys. Great learning for me.

I guess when on Vnav pth without an angle, the flight path may actually descend below the stipulated 3deg prior to the FAF. I know that is not a CDFA as the FAF hasn't been reached, however that does not comply to the approach requirements as there may be obstacles below that an OIS (obstacle identification surface) was intended in the design. Basically, the main question was ... can the CDU have multiple angles after the FAF or before, as coded in the databse as shown below.When the procedure was loaded, only the last angle to the MAP was shown, that means the acft may Vnav pth (idle thrust descent) and not keep to the angle, which means it did not clear the obstacle protection surface. TrackCode, Waypoints, Country, Navaids.Ident, TurnDir, Course, Distance, Alt, VnavIF DME12 VT PUT 002500 TF DME07 VT PUT 001900 TF 43DME VT PUT 01047A 2.98 TF 24DME VT PUT MAP 2.98

Thanks for the inputs.There are approaches in mountainous areas where there is a gradient leg to the FAF then another gradient down to the E/D (TCH or MAP). The database is coded as such but am not sure if the real airplane can perform it in reality and also shown on the CDu as such. I don't have a pic here but if you have access to VLLB (LAos) new procedure in Nov for reference. In that app, its a 3deg down to the FAF then 3.46 down to the E/D. Not having a GPA will result in the airplane possibly going down below the glidepath although Vnav path is FMAed, however the airplane will still observe the Alt at the FAF but it already has violated the required gradient. Tks.

Hi Matt, Thanks, but i think that is possible, as in Arinc 424, the guidance for the FMS providers is to code the database in such a way. There are procedures where there are multiple GPAs prior to the FAF. And even after that, it should allow that too, of course they should be the same angle though.

Hi, I was flying a multiple segment final approach to VTSP Vordme Rwy 27, and I can see in the database in access that there are 2 segments prior to the MAP that have the GPA vertical angle. However, when the procedure is loaded, only one GPA to the E/D at the MAP is shown. When on VNAV PATH, the acft behaved as it should with only one GPA in that it only observes the last segment to the E/D. Naturally I was flying a constant descent procedure and I think the FMS should accept multiple GPAs. I did not meddle with the procedure after loading it. Any clues? ... thanksRaymond

Hi, I do not expect this feature to be in the NGX, but I would like to find out more about the details, equipment of such a package. If there be anyone who knows, please kindly share your knowledge. Many thanks,Raymond

The Y and Z suffixes are a 'rule of thumb' by ICAO. It just tells you there are differences between the procedures, either in terms of tracks or equipment needed. If there are more than one of the sames type proc down that runway, the procedure will have a Z then a Y then X and so on ...So, if u see a Y procedure but cannot find a Z procedure, then something shud be amiss.