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Flying a SID with a Discontinuity

Posted: Wed Jan 03, 2018 12:15 am
by highflyer737
Hi,

What is the proper way to fly a SID with a discontinuity, e.g. that includes a vectored leg, using the programed FMS flight plan and the NAV mode? For example, the LOUPE4 departure from KSJC involves flying a specific heading until directed by ATC to turn back to the SJC VOR.
Loading this SID into the FMS (from current Navigraph data—1713) produces the following Legs in the ACTIVE FLT PLAN screen:

RW30L KSJC
(301-deg 1.4 NM)
DE30L
(306-deg 6892 NM)
*INT01
FLY 123-deg OR
AS ASSIGNED
>>DISCONTINUITY<<
SJC
(342-deg 14.6 NM)
BMRNG
...

A ~180-deg. turn is required at 1.8 nm from the SJC VOR. The FMS has a 6892 nm leg here so the turn never happens. Can this be changed manually? If so, how? Currently I fly this leg by hand or using the heading hold mode, and delete waypoints in the FMS to force it to capture the right track after returning to SJC.

Second, how to handle the discontinuity? I assume that if the FMS made the turn at 1.8 nm I could simply return to SJC by selecting the SJC leg when cleared to do so. (This is what I do in other aircraft I own ... but maybe there’s a better/more correct way to do it.) Is this the correct way to fly these sorts of procedures—how are they handled in the real world?

Thanks in advance,

Dave

FSX Boxed, Win7, Thrustmaster T16000, FMS V3.02.11
ActiveSky16, Pro-ATC X, UT Live, UTX, and GEX

Re: Flying a SID with a Discontinuity

Posted: Wed Jan 03, 2018 7:50 am
by WarpD
Give me the complete flight plan you used please.

Re: Flying a SID with a Discontinuity

Posted: Wed Jan 03, 2018 12:22 pm
by highflyer737
The complete flight plan is:

RW30L KSJC
301-deg 1.4NM
DE30L
306-deg 6892NM
*INT01
FLY 123-deg OR
AS ASSIGNED
>>DISCONTINUITY<<
SJC
342-deg 14.6NM
BMRNG
007-deg 53.3NM
ORRCA
037-deg 84.3NM
KTRK

In flight I later (usually somewhere just before or just after ORRCA) assign the SIGNA.RNAV11 approach so it becomes:

...
ORRCA
024-deg 68.9NM
SIGNA
036-deg F17.0NM
LEKYI
036-deg 0.0NM
LEKYI H
346-deg 0.0NM
LEKYI
134-deg 6.0NM
FAMPU
126-deg 3.0NM
SUYYO
126-deg F 5.6NM
MARDR
106-deg 0.8 NM
RW11


Thanks,

Dave

Re: Flying a SID with a Discontinuity

Posted: Wed Jan 03, 2018 2:39 pm
by WarpD
Ok, I have reviewed the DP's source data and compared it to what Navigraph has in it and it appears that Navigraph's data has it coded incorrectly.

It should be:
1 - Fly heading 306 until above altitude 462.
2 - Fly heading 306 until 1.8nm DME from SJC VOR
3 - Right turn heading 123 until vectored.
4 - Direct to SJC.
5 - Fly great circle course to BMRNG

Note there is no DE20L (dunno where that came from for Navigraph). Now, the INT01 entry has issues, clearly (6892nm??) but there's still an odd coding setup. At any rate, I will see if I can see anything in this... but no promises.

Re: Flying a SID with a Discontinuity

Posted: Wed Jan 03, 2018 7:41 pm
by WarpD
Ok... I've looked at the way the FMS loads the Navigraph leg data and the DE30L/DE30R legs are part of the problem. Only part. It causes some iffy math that may or may not happen if the correct type of legs were defined.

On a side note... you would never see a 750 fly to KTRK... the runway is the minimum length under ideal conditions. Also, your flight plan has no actual waypoints outside of the procedures. The real FMS never liked that because it couldn't save the flight plan. Flight plans only save the enroute waypoints and no procedures. Since your flight plan has no enroute waypoints and only contains procedures... the FMS in the real aircraft may or may not get 'upset'. It didn't always behave. LOL

Re: Flying a SID with a Discontinuity

Posted: Thu Jan 04, 2018 5:20 pm
by highflyer737
Thanks for the super fast responses and for getting to the bottom of this?

So how would pilots handle this in the real world? It’s fairly routine at KSJC for Departure to route aircraft off the SIDs for more direct routes as traffic permits. When I try to leave the preprogrammed route to fly a heading for a while I cannot get the FMS to “catch up” again. Is it possible to skip legs if required to do so?

Thanks,

Dave

Re: Flying a SID with a Discontinuity

Posted: Sun Jan 07, 2018 10:06 pm
by WarpD
You would DIR TO the leg you want to go active.