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jmdriskell

Trouble with Grice SID Departing EGPH R24

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I don't know if this is where I should ask for help, but I'll try.

 

Flying PMDG 737-900 NGX departing EPGH on Rwy 24, trying to follow the GRICE3C SID.  The SID reads:

 

SID GRIC3C RNW 24 FIX OVERFLY UWNB AT OR ABOVE 640 HDG 038 INTERCEPT RADIAL 353 TO FIX TLA32 FIX OVERFLY TLA32 FIX OVERFLY TLA33 AT OR ABOVE 4000 TRK 303 INTERCEPT RADIAL 348 TO FIX TLA38 FIX TLA38 AT OR ABOVE 4500 FIX GRICE 6000

 

The SID Chart is here: http://www.globalvirtualair.com/charts/EGPH/grice%20sid.pdf

 

The departure requires a hard right after UWNB, then a left onto the TLA R353, the a left onto the TLA R348.  FMC is setup to fly this departure, takeoff is normal, Autopilot captures the route and plane starts the first hard right turn.  About now, everything seems to come unglued.  The Autopilot can't seem to follow the correct departure route.  I've tried to follow the exact route several times, but each time I wind up modifying the route and hand flying the departure until I can capture the remaining northbound course.

 

The route looks normal when I check it in MAP mode, but it sure turns into spaghetti when I try to follow it.

 

Any help or ideas will be appreciated (criticisms will also be accepted) :o)

 

Jim Driskell

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My opinion is that the old syntax we still use for the terminal procedures is getting tripped up at the "radial to fix..then, overfly same fix," in my experience the "radial to fix" is an implied overfly. Try this:

 

SID GRIC3C RNW 24 FIX OVERFLY UWNB AT OR ABOVE 640 HDG 038 INTERCEPT RADIAL 353 TO FIX TLA32 FIX OVERFLY TLA33 AT OR ABOVE 4000 TRK 303 INTERCEPT RADIAL 348 TO FIX TLA38 FIX TLA38 AT OR ABOVE 4500 FIX GRICE 6000

 

Then I'd test it and see if the radial to fix tla38 works, which I doubt. My second try would be

 

SID GRIC3C RNW 24 FIX OVERFLY UWNB AT OR ABOVE 640 HDG 038 INTERCEPT RADIAL 353 TO FIX TLA32 FIX OVERFLY TLA33 AT OR ABOVE 4000 TRK 303 INTERCEPT RADIAL 348 TO FIX TLA38  AT OR ABOVE 4500 FIX GRICE 6000

 

Basically, I am combining the radial to fix and overfly same fix. The syntax was built to handle these old non-GNSS procedures but there is a fine art to creating them that doesn't lend itself to the large batch jobs that Stephan at Navigraph performs....he does a great job but there is that 1% LOL.

 

See also an old guide "Making 737NG Procedures 5th.pdf" in the AVSIM library. It's the definitive guide to this old syntax.

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Search for this: "PMDG 737NG Terminal Procedures Tutorial 5th Edition"  for the file Dan references...

 

David Jones

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Dan,

 

I tried your second suggestion but got an error in the FMC "AT OR ABOVE, LN: 87."  Apparently it didn't like the first "AT OR ABOVE 640?"  So I modified the original entry as such:

 

Origional - SID GRIC3C RNW 24 FIX OVERFLY UWNB AT OR ABOVE 640 HDG 038 INTERCEPT RADIAL 353 TO FIX TLA32 FIX OVERFLY TLA32 FIX OVERFLY TLA33 AT OR ABOVE 4000 TRK 303
INTERCEPT RADIAL 348 TO FIX TLA38 FIX TLA38 AT OR ABOVE 4500 FIX GRICE 6000

New       - SID GRIC3C RNW 24 FIX OVERFLY UWNB AT OR ABOVE 640 HDG 038 INTERCEPT RADIAL 353 TO FIX TLA32 FIX OVERFLY TLA33 AT OR ABOVE 4000 TRK 303 INTERCEPT RADIAL 348 TO
FIX TLA38 FIX TLA38 AT OR ABOVE 4500 FIX GRICE 6000 (Deleted FIX OVERFLY TLA32).

 

Worked as advertised and the Autopilot followed the SID perfectly.  I think before the change, the flight tract circled at TLA32 because of the overfly entry.

 

Thanks for the help.  Now I'll read the pub!

 

Jim
 

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Thanks for the feedback Jim, good to know.  One of my complaints is that the TO FIX keywords imply OVERFLY, because this is not always the case. When coding a procedure and I want a fly by behavior I have to create the lat/lon for the intercept point and get rid of the INTERCEPT RADIAL....TO FIX construct.  Problem is that this has been around a long time and no one wants to recode old code that they would rather get rid of.

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