SID ARNAS 3A Wrong Turn

[thasos 21]

After TO from LGTS RW34 ARNAS3A, at MKR 10 the plane should do a left turn to intercept MKR VOR at R084. But instead it did a right turn to intercept MKR VOR at R804.

[thasos 21]

same with ARNAS3B ... wrong turn

 

 

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[thasos 21]

so, can someone confirm here that this is something which is beeing looked at? Or if some kind of limitation? Its not only those two SID's its happening often that a wrong turn is beeing initiated.

[JRBarrett 675]

6 hours ago, thasos said:

so, can someone confirm here that this is something which is beeing looked at? Or if some kind of limitation? Its not only those two SID's its happening often that a wrong turn is beeing initiated.

I looked at the coding of the ARNAS 3B procedure (from runway 16), in the nav database file. I looked at both the supplied NavDataPro database that came supplied with the CRJ (based on Lufthansa LIDO), and Navigraph (based on Jeppesen), and neither contains a specific turn direction at the first waypoint, which is the MKR 163 radial at 10 miles DME. Based on that, I assume that left to its own devices, if the  autopilot remains in NAV mode, the aircraft will turn in the shortest direction to fly direct to the next waypoint MKR, which in the case of the ARNAS 3B would be a left turn, rather than right.
 

This is a question that only a pilot who is familiar with how this departure is displayed and flown in a real CRJ could answer for sure, but it is possible that even the real aircraft cannot fly the initial part of this procedure fully in NAV mode. The SID instructions simply say to fly direct to MKR/163/10, then to turn RIGHT at that waypoint to take up a direct course to MKR.

 

This is not marked as being an RNAV SID on the r/w departure chart, which also points to the possibility than an FMS cannot fly this entire procedure automatically.

 

Most likely, the pilot would have to do the turn manually in HDG select mode, until on an intercept heading to MKR, and could then do a DIR INTC to MKR, and re-engage NAV mode.

 

This is not a bug in the sim CRJ FMS - there is simply no turn direction coded for this SID in either the NavDataPro or Navigraph databases.

 

Later, I will try this departure in the Zibo 737 in X-Plane to see how it would handle it.

[Danny875 4]

What about this one? 
The aircraft tracked outbound from the VOR then initiated a left turn to 187 THEN turned left to intercept the localiser instead of turning right to 007 first.

 

[gorrack 5]

Clarification,

From RWY16 is ARNAS 3B - Intercept MKR R163 to D10.0 MKR, turn RIGHT to MKR VOR, turn RIGHT, intercept MKR R084 to ARNAS.

Happened also to me turning LEFT (Nav mode) and the SID states RIGHT.

I guess that this may not be coded to the database. 

I am quite curious, following.

 

[JRBarrett 675]

55 minutes ago, gorrack said:

Clarification,

From RWY16 is ARNAS 3B - Intercept MKR R163 to D10.0 MKR, turn RIGHT to MKR VOR, turn RIGHT, intercept MKR R084 to ARNAS.

Happened also to me turning LEFT (Nav mode) and the SID states RIGHT.

I guess that this may not be coded to the database. 

I am quite curious, following.

 

Thanks, I corrected my reference to the ARNAS 3B.

 

The turn definitely does not appear to be coded in the CRJ Nav database. Whether that is accurate to the real airplane is something I don’t know.

 

The right turn is included in the procedure for the Zibo 737, and present in the database - but that aircraft emulates a different FMS entirely. Both the XP Zibo database, and the CRJ database both come from Navigraph on my system, and both from the same cycle.