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vonmar

Missed approach turn direction

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PMDG737NGX (FSX) missed approach turn direction question.

Example from PAJN airport. The approach plate LDA X RWY 8 says to turn Right on a missed approach.


Navigraph Airac 1507:
APPROACH LDAX08 FIX LYNNS AT OR ABOVE 5600 FIX BARLO AT OR ABOVE 3700 FIX CGLNB 1347 RNW 08 HDG 310 INTERCEPT RADIAL 251 TO FIX BARLO FIX OVERFLY BARLO FIX SSR AT OR ABOVE 5600 HOLD AT FIX SSR RIGHT TURN INBOUNDCOURSE 347 LEGTIME 1

Should a right turn be in the procedure (mountains on the left)?

***

I checked KJFK approach and it shows a missed approach Left turn direction as part of the procedure.

APPROACH ILS13L FIX TELEX AT OR ABOVE 1800 FIX CAXUN 1500 RNW 13L TRK 135 UNTIL 600 TURN LEFT DIRECT FIX DPK AT OR ABOVE 4000 HOLD AT FIX DPK LEFT TURN INBOUNDCOURSE 258 LEGTIME 1
 

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Should a right turn be in the procedure (mountains on the left)?

 

Navigraph question. They're the ones who write that data.

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Navigraph question. They're the ones who write that data.

For the missed approach the approach chart says:

Immediate climbing right turn to 5600 on heading 310 and on CGL NDB Brg 251 to intercept SSR VORTAC R-027 direct SSR VORTAC or EEF NDB and hold.

 

 

A Navigraph post reply said (http://www.navigraph.com/forum/viewtopic.php?f=30&t=2643):

 

"The command language that PMDG uses is missing some vital elements. One of these elements is the ability to specify a turn direction - the syntax does not include commands like "RIGHT TURN" or "LEFT TURN" and consequently the aircraft will turn directly to a given heading using the shortest distance which in this case results in a left turn. You can fake it with a series of intermediate directions if you like, but you would be better off simply manually turning to the right to, say, 140 degrees and then letting the FMC have command."

 

LDA%20X%20RWY8_zpsb9uubtpp.jpg

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I am not surprised, I see this come up about once every blue moon.  The TURN RIGHT DIRECT FIX syntax is in the old syntax PMDG uses but it doesn't exactly work in this case because you need a fix to turn to where there is none. What we need is TURN RIGHT TO HDG 310.... yup. I've dealt with this problem in the past (I forget the locations but mountains were involved) by putting a pseudo waypoint at where I want to join the NDB bearing then turn right direct to that... the rest is routine.  I think in this case I would put the pseudo waypoint at the intersection of CGL Brg-251 and SSR R-027, which would be really easy with a geo calculator.

 

The correct answer is the old syntax that PMDG uses needs a little custom work, true, but more importantly you have to fly the missed approach as published not as the FMC dictates.  Always true.

 

This goes before my time around these products, but I believe the navdata syntax adopted by PMDG was already in use by the community.  I'm pretty sure PMDG did not create it.  I keep hoping for a better solution but that's not going to happen for a long time and we get to play with what we have.

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Dan,

 

Thanks for the answer and the background information on turn direction usage in PMDG ... much appreciated.

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Typically on a missed procedure with the terminology "immediate turn", the turn is handflown anyway. So you can crank a right turn and then couple back up to LNAV once you're on the 310 heading.

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My question was just about when Turn direction is used is used in PMDG procedures.

Dan answered that.

 

BTW, aircraft do fly this go around procedure without a problem.

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