RNAV19 Approach into KDCA is Jacked in the FPL (Legs Listed Correctly/Drawn Wrong on MFD)

[DFWSupertrooper 137]

Since the 1.0.5 update, where RNAV19 into KDCA was specifically mentioned as an issue, the approach won't draw correctly in the MFD.  Repeated lines between A/C current position and KDCA overlap the actual route despite the FPL waypoints being listed correctly.  When Changing the approach to another, the duplicates fall off/reselecting adds the duplicates back in).

 

Also, the FPS drop that was resolved when entering waypoints into the FMS has indeed been fixed, but now occurs (on that approach) when you proceed into the PERF setup process.  When completed, the FPS drop stops and becomes normal again.

 

 

[JRBarrett 675]

On 6/4/2021 at 12:34 PM, DFWSupertrooper said:

Since the 1.0.5 update, where RNAV19 into KDCA was specifically mentioned as an issue, the approach won't draw correctly in the MFD.  Repeated lines between A/C current position and KDCA overlap the actual route despite the FPL waypoints being listed correctly.  When Changing the approach to another, the duplicates fall off/reselecting adds the duplicates back in).

 

Also, the FPS drop that was resolved when entering waypoints into the FMS has indeed been fixed, but now occurs (on that approach) when you proceed into the PERF setup process.  When completed, the FPS drop stops and becomes normal again.

 

 

Did it load or display correctly before the 1.0.5 update? I would be surprised if it did.

 

As I have explained before in other threads, neither the real nor simulated CRJ is compatible with any RNP/AR approach procedure using curved RF leg segments. This includes the RNP 19 approach at KDCA, both RNP approaches at KPSP, the RNP procedures at VQPR (Paro, Bhutan), and many many more. I mention these in particular, because it seems many CRJ customers are trying to load and fly these procedures and running into problems, which is to be expected.

 

If you set KDCA as a destination in the FMS of a real CRJ, you will only see three approaches listed for runway 19: The LDA-Y, the LDA-Z and the River Visual. No real CRJ is (or ever will be) capable of flying an RNP/AR approach such as the RNP 19. The River Visual comes closest to the path of the RNP, but that has to be hand-flown (visually), as the name implies.

 

These approaches appear in the FMS of the sim version only because both the Aerosoft NavDataPro and Navigraph databases include every approach for every airport  - including procedures the real CRJ is not capable of flying. If there was a reliable way (in the sim) to prevent RNP/AR approaches from appearing on the ARR page, (as is done on the real aircraft), it would have been done, but at the moment that is not possible because of the way the database is structured.

 

The sim FMS was designed using Rockwell Collins technical documents for the real FMS4200 installed in the real CRJ, and is programmed to handle all leg and waypoint types found in the FMS of the actual aircraft.
 

An RNP/AR approach contains unique waypoint and leg types specific to these procedures, and neither the real nor simulated FMS is capable of correctly interpreting and executing all of the navigational instructions contained in the database for an approach of this type. 
 

One leg type it cannot handle is an RNP-specific RF leg. “RF” stands for “Radius to Fix”. The FMS4200 can fly a basic RF leg, as long as it consists of a constant-radius turn about a single fix. This is definitely not the case with an RNP/AR approach.

If you look at the KDCA RNP 19 approach plate, you will see that every leg segment between GREYZ and FIROP is curved to precisely follow the path of the river. No r/w CRJ is remotely capable of doing that to the tight lateral tolerance required by RNP/AR , nor is the CRJ in the sim.

 

The reason that loading this type of approach in the sim causes things like duplicate waypoints, incorrect waypoint names, spurious multiple legs on the MFD etc, is because for all intents and purposes, most of the procedural data in the nav database for these procedures would be (to a greater or lesser degree) gibberish to the parsing routines in the FMS. Being based on the real CRJ FMS, It was not designed to correctly interpret all of the potential RNP procedural definitions in the nav data.

 

This is not a “bug”. The best real world example I can think of to illustrate the problem would be giving an individual detailed instructions on how to perform a task in Japanese.... when the person being instructed speaks only English.

 

The FMS in the sim does not “speak or understand” RNP/AR, and I don’t think that is going to change.

 

It is not only the FMS that disqualifies the real CRJ from RNP/AR. Any aircraft  that flies one of these procedures must be capable of calculating and displaying “actual navigational performance” at all times, which the real CRJ cannot do.
 

It requires an autopilot capable of using a continuously variable bank angle while turning, while the real CRJ autopilot can only use one of two fixed bank angles.

 

It requires a nav display capable of displaying the curved RF path between each waypoint, which the Proline 4 displays cannot do.

 

Finally, it requires a full coupled VNAV system capable of flying a specific vertical path to very close tolerances. The coupled VNAV option that is installed on some r/w CRJs does not have that ability.

 

Hans has made some coding changes to try to prevent RNP procedures from overtly locking up the sim if someone tries to load one, but AFAIK, that is probably the best that can be done.

 

If you have access to r/w approach charts, and you see it marked as “RNP” or “RNP/AR” or see the words “AUTHORIZATION REQUIRED” then proceed with caution and at your own risk.

 

The sim is unlikely to load or display or fly the procedure correctly. It could cause performance issues, it might (still) cause the sim to lock up. There is no easy or reliable “fix” for this.

 

 

[Dopster198 131]

This is such an excellent explanation, I think this post needs to be pinned 

[Matthew2312 95]

On 6/5/2021 at 6:41 PM, JRBarrett said:

Did it load or display correctly before the 1.0.5 update? I would be surprised if it did.

 

As I have explained before in other threads, neither the real nor simulated CRJ is compatible with any RNP/AR approach procedure using curved RF leg segments. This includes the RNP 19 approach at KDCA, both RNP approaches at KPSP, the RNP procedures at VQPR (Paro, Bhutan), and many many more. I mention these in particular, because it seems many CRJ customers are trying to load and fly these procedures and running into problems, which is to be expected.

 

If you set KDCA as a destination in the FMS of a real CRJ, you will only see three approaches listed for runway 19: The LDA-Y, the LDA-Z and the River Visual. No real CRJ is (or ever will be) capable of flying an RNP/AR approach such as the RNP 19. The River Visual comes closest to the path of the RNP, but that has to be hand-flown (visually), as the name implies.

 

These approaches appear in the FMS of the sim version only because both the Aerosoft NavDataPro and Navigraph databases include every approach for every airport  - including procedures the real CRJ is not capable of flying. If there was a reliable way (in the sim) to prevent RNP/AR approaches from appearing on the ARR page, (as is done on the real aircraft), it would have been done, but at the moment that is not possible because of the way the database is structured.

 

The sim FMS was designed using Rockwell Collins technical documents for the real FMS4200 installed in the real CRJ, and is programmed to handle all leg and waypoint types found in the FMS of the actual aircraft.
 

An RNP/AR approach contains unique waypoint and leg types specific to these procedures, and neither the real nor simulated FMS is capable of correctly interpreting and executing all of the navigational instructions contained in the database for an approach of this type. 
 

One leg type it cannot handle is an RNP-specific RF leg. “RF” stands for “Radius to Fix”. The FMS4200 can fly a basic RF leg, as long as it consists of a constant-radius turn about a single fix. This is definitely not the case with an RNP/AR approach.

If you look at the KDCA RNP 19 approach plate, you will see that every leg segment between GREYZ and FIROP is curved to precisely follow the path of the river. No r/w CRJ is remotely capable of doing that to the tight lateral tolerance required by RNP/AR , nor is the CRJ in the sim.

 

The reason that loading this type of approach in the sim causes things like duplicate waypoints, incorrect waypoint names, spurious multiple legs on the MFD etc, is because for all intents and purposes, most of the procedural data in the nav database for these procedures would be (to a greater or lesser degree) gibberish to the parsing routines in the FMS. Being based on the real CRJ FMS, It was not designed to correctly interpret all of the potential RNP procedural definitions in the nav data.

 

This is not a “bug”. The best real world example I can think of to illustrate the problem would be giving an individual detailed instructions on how to perform a task in Japanese.... when the person being instructed speaks only English.

 

The FMS in the sim does not “speak or understand” RNP/AR, and I don’t think that is going to change.

 

It is not only the FMS that disqualifies the real CRJ from RNP/AR. Any aircraft  that flies one of these procedures must be capable of calculating and displaying “actual navigational performance” at all times, which the real CRJ cannot do.
 

It requires an autopilot capable of using a continuously variable bank angle while turning, while the real CRJ autopilot can only use one of two fixed bank angles.

 

It requires a nav display capable of displaying the curved RF path between each waypoint, which the Proline 4 displays cannot do.

 

Finally, it requires a full coupled VNAV system capable of flying a specific vertical path to very close tolerances. The coupled VNAV option that is installed on some r/w CRJs does not have that ability.

 

Hans has made some coding changes to try to prevent RNP procedures from overtly locking up the sim if someone tries to load one, but AFAIK, that is probably the best that can be done.

 

If you have access to r/w approach charts, and you see it marked as “RNP” or “RNP/AR” or see the words “AUTHORIZATION REQUIRED” then proceed with caution and at your own risk.

 

The sim is unlikely to load or display or fly the procedure correctly. It could cause performance issues, it might (still) cause the sim to lock up. There is no easy or reliable “fix” for this.

 

 

He speaks the truth. We CRJ drivers are not “blessed” with the wonders (read cheating) of a cutting edge FMS. Nor are we gifted with an autopilot that can intercept a localizer with a crosswind correctly on the first attempt. I like to joke that George is drunk while he attempts to understand how one flys a localizer.