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RPRIEVER

Weird anomaly flying into KDCA

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Greetings all, I've noticed a strange problem flying the RNAV rwy 19 approach into KDCA. The first part of the approach is fine, but right before getting to the FONVI waypoint, the ND shows a big circle, and takes me on a 360 degree turn. (no, I havent entered a hold at SETOC in the FMC). This had happened 3x in a row. I've attached a few screenshots, perhaps someone has an idea what is going on. Many thanks. Also, here's the chart:http://flightaware.c...RNP)+RWY+19/pdf


Ron Priever

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Guest tonyf38

I'll see if I can recreate this..

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I've had this before. I've posted it once. I also shot a DME arc approach and it didn't work out so well either.
Ryan posted this yesterday !! "" Arcs are not in our navdata format - should be there when we do the new navdata format. ie you'll see "ARC L" and stuff like that on the LEGS page "" Fred.

Frederic Steiner.

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Guest tonyf38

I just tried the RNAV RWY 19, same thing, same error message.. That approach is tricky and better to fly it manually earlier.. Requires some creative banking.. I'm going to try it using just LNAV and lvl change/vs mode and see what happens..

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I wonder what's causing that loop to suddenly appear? It's really strange.


Ron Priever

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Guest tonyf38

Yeah Zach.. Something with the altitude and speed restrictions get goofed up in CDU.. That's a manual approach all the way anyway.. If you're going to use autopilot, better to use the Vor approach in there... Just using LNAV same thing, wants to make a right turn and circle.. Darn computers.. haha..

I wonder what's causing that loop to suddenly appear? It's really strange.
That loop appears when the speed restriction error pops up... Maybe Fred can chime in here cuz VNAV approaches are something I don't use..

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I'm going to install the latest Navigraph data (1109) tomorrow and retry the approach. If it still doesnt work I'll post something on their website. Probably a coding error on their part.


Ron Priever

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This topic carried over to Navigraph and in trying to find a resolution I discovered the following: The approach waypoints on the Jeppesen chart for KDCA RNAV19 are fly-by, the procedure calls for a left 'arc turn' after SETOC to FONVI, from FONVI a 'right arc' turn to JUBOL.The NGX makes the left turn direct to FONVI rather than in an 'arc' on a heading which carried forward would be to the right of JUBOL, the instruction for the right turn from FONVI to JUBOL leads to a 360deg circle as per the attached.rnav19.jpgThe current database uses 'LEFT/RIGHT TURN' commands and does not stipulate the 'ARC', that may not even be possible or an option within the ARINC format. A workaround is to remove the right turn statement after FONVI . As noted by Ian over at Navigraph this doesn't happen with the queen so it's probably a consequence of that improved turn prediction of the NGX. Maybe a resolution in the new PMDG nav-database format?

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