# RNAV 21 KFFA gives wrong guidance

Hi, I am flying the Alabeo C-177 using the stock GNS430 with Navigraph charts.

When I fly the RNAV 21 into KFFA the GPS guidance from YELUS (IAF/IF) wants to send me to UHAWO (FAF) on a 176 TRK instead of a 148 TRK as per the chart. It looks like the 148 degree segment (1600/9.3nm) to the FAF is just missing from the approach.

This happens when I start the approach from OCSIP.

Here is the Aerograph/NACO chart:

Any idea on why?

Looking at the “Custom Data/GNS430/navdata/Proc/KFFA.txt” I see:

``````APPTR,R21,21,ALGTR
IF,ALGTR,35.933353,-76.065986, ,0.0,0.0,0,0,0,0,0,0,0,0
TF,YELUS,36.199858,-75.814258,0, ,0.0,0.0,0.0,0.0,2,2200,0,0,0,0,0,1
HF,YELUS,36.199858,-75.814258,2, ,0.0,0.0,148.0,04,0,0,0,0,0,0,1,0,0

APPTR,R21,21,OCSIP
IF,OCSIP,36.137486,-76.004292, ,0.0,0.0,0,0,0,0,0,0,1,0
TF,YELUS,36.199858,-75.814258,0, ,0.0,0.0,0.0,0.0,2,2200,0,0,0,0,1,0

APPTR,R21,21,RBX
IF,RBX,35.920497,-75.696933, ,0.0,0.0,0,0,0,0,0,0,0,0
TF,YELUS,36.199858,-75.814258,0, ,0.0,0.0,0.0,0.0,2,2200,0,0,0,0,0,1
HF,YELUS,36.199858,-75.814258,2, ,0.0,0.0,148.0,04,0,0,0,0,0,0,1,0,0
``````

I believe the problem is the OCSIP APPTR (approach transition?) is missing a third line to turn to a 148 degree TRK like the other two transitions.

Hi,
the procedure is coded correctly. When you look on the charts, you see that the OCSIP transition has “NoPT”, which means “no procedure turn”. Therefore the the HF-leg is not necessary. The track goes (without any course information) from OCSIP to VELUS - the final approach part goes from YELUS to UHAWO

Here the complete coding:
The first two lines are the transition (Type A): OCSIP → YELUS
From line 3 on you see the final approach: YELUS → UHAWO → OYOCE
you see also, that the course 176 starts between UHAWO and OYOCE, according the charts.

``````APPCH:010,A,R21,OCSIP,OCSIP,K7,E,A,E  A, ,   ,IF, , , , , ,      ,    ,    ,    ,    , ,     ,     ,18000, ,   ,    ,   , , , , , ,A,J,S;
APPCH:020,A,R21,OCSIP,YELUS,K7,P,C,EE B, ,   ,TF, , , , , ,      ,    ,    ,    ,    ,+,02200,     ,     , ,   ,    ,   , , , , , ,A,J,S;
APPCH:010,R,R21, ,YELUS,K7,P,C,E  I, ,   ,IF, , , , , ,      ,    ,    ,    ,    ,+,02200,     ,18000, ,   ,    ,   , , , , , ,A,J,S;
APPCH:020,R,R21, ,UHAWO,K7,P,C,E  F, ,   ,TF, , , , , ,      ,    ,    ,1480,0093,+,01600,     ,     , ,   ,    ,   ,RW21,K7,P,G, ,A,J,S;
PRDAT:A,        LP, ,          ,A,      LNAV, ,   , ,   , ,   , ,   ,J,S;
APPCH:030,R,R21, ,OYOCE,K7,P,C,EY M, ,   ,TF, , , , , ,      ,    ,    ,1760,0032, ,00307,     ,     , ,   ,-375,   , , , , , ,A,J,S;
APPCH:040,R,R21, , , , , ,  M , ,   ,CA, , , , , ,      ,    ,    ,1760,    ,+,00412,     ,     , ,   ,    ,   , , , , , ,A,J,S;
APPCH:050,R,R21, ,OCSIP,K7,E,A,EY  ,R,   ,DF, , , , , ,      ,    ,    ,    ,    ,+,03000,     ,     , ,   ,    ,   , , , , , ,A,J,S;
APPCH:060,R,R21, ,OCSIP,K7,E,A,EE H,R,   ,HM, , , , , ,      ,    ,    ,3180,0040, ,     ,     ,     , ,   ,    ,   , , , , , ,A,J,S;
``````

So the coding is correct so far. Possible it´s an issue with the GNS430 but I don´t see any issue in the coding, sorry.

Cheers,
Richard

It could be. I do see the GNS430 briefly show 148 TRK to UHAWO from approaching YELUS after OCSIP. But then it will immediately change it to 176 after passing YELUS.

Looks like a GNS430 issue, yes …

Cheers,
Richard

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