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vonmar

PMDG737-600 problem entering a hold

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PMDG737-600 problem entering a hold (screenshots).

Current Navigraph navdata AIRAC cycle    : 1613
APPROACHES
APPROACH ILS09 FIX SARGS AT OR ABOVE 2000 FIX GATTO 2000 RNW 09 HDG 095 INTERCEPT RADIAL 120 TO FIX PGY FIX OVERFLY PGY AT OR ABOVE 5000 TURN RIGHT DIRECT FIX CAPUS HOLD AT FIX CAPUS RIGHT TURN INBOUNDCOURSE 088 LEGTIME 1
 TRANSITION MZB FIX MZB FIX GATTO AT OR ABOVE 2800 FIX PI001 AT OR ABOVE 2000 SPEED 210 FIX OVERFLY PI002 AT OR ABOVE 2000 SPEED 210 FIX PI003 AT OR ABOVE 2000 SPEED 210



KSAN, rwy09 ILS missed.

LNAV route to holding fix CAPUS looks ok on ND but 737 never entered the holding pattern.
At the holding fix (CAPUS) the aircraft turned right, flew away from the fix about 3nm and started doing clockwise circles ...


1-KSAN-CAPUS-next_zpsfsy23n4i.jpg

2-KSAN-MissedFix_zpsgdjwwt4j.jpg
 

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Vaughn, did you press Hold on the FMC?

 

Doug Pelton

 

Doug,

Happy holidays ..thanks for the reply.

 

Just wondering why you asked if I had pressed the Hold key on the CDU/FMC?

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After the PMDG737-600 failed to enter the HOLD I took a few screenshots (thinking maybe they would give a clue as to what went wrong) before setting up for another approach / diversion.

The aircraft got lost .. doing circles .... I pulled up the CDU Hold page to verify the data against the Navigraph data .. and Exit the hold procedure.


6-KSAN-Lost-HOLD_zpst560pfr6.jpg

3-KSAN-CDU-HOL-Data_zpsv0marhcw.jpg
 

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as far  i can make  out  is  that you  got  088/r   turn  instead  of  left  turn  so the aircraft  is  turning  right  to enter  the hold

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as far  i can make  out  is  that you  got  088/r   turn  instead  of  left  turn  so the aircraft  is  turning  right  to enter  the hold

 

Pete,

Thanks for the reply and Happy Holidays.

 

I am on LNAV to the missed approach  holding fix.

 

After I reach the fix am I supposed to get e.g., an LNAV parallel or teardrop entry to the KSAN holding pattern?

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In reviewing the screenshots I noticed that the missed approach HOLD is drawn off about 90 degrees for the next (same) ILS landing retry.

7-KSAN-Exit-HOLD_zpsyko46a1r.jpg
 

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Did a video to show the hold entry (better than just screenshots):

 


 

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I can only answer this from a pilot/operator's perspective, not a software engineer or developer. I'm also suggesting a technique instead of a procedure.

 

There are three types of hold entries: direct, parallel and teardrop. In your case the FMC appears to have gotten confused (it can happen IRL) and you ended up on the "non-protected" side of the hold. The racetrack pattern not only depicts the hold course to follow but also the side the radial that you are protected from other traffic and terrain. In your video I would have moved to HDG mode and assisted the airplane in 1) remaining on the protected side, and 2) flying the holding pattern as published.

 

Another contributing factor is the holding pattern charted is only 1 minute legs - traditionally when flying a jet I would request 5 mile legs to prevent the airplane from constantly in a turn chasing it's way to the holding fix. To change that simply enter "5" in LSK L5 and the holding pattern will adjust to 5 mile legs. That will be much easier to control.

 

I hope I made some sense here - I have had this happen in the real aircraft and it really is a factor of speed/weather/radius of turn. I always say that instead of sitting there wondering where the airplane is going, tell it where to go. In this case HDG mode to keep it on track is what I would recommend. Once back on the course you can engage LNAV if desired.

 

Blue Side Up,

 

Matt Velure

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Matt,

Thanks for the reply.

My question was just about the PMDG737 entering the holding pattern.


Note: For this hold I just left the default values per the Navigraph Navdata (DIRECT FIX CAPUS HOLD AT FIX CAPUS RIGHT TURN INBOUNDCOURSE 088 LEGTIME 1).
 

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My question was just about the PMDG737 entering the holding pattern.

 

Hi Vaughan- I suppose what I was saying in my post is that I've seen this exact thing happen in a Lear Jet, Saab 340, EMB-120, 737, you get the drift. I do not think it's a problem related to the software coding, but how a high performance airplane deals with holding patterns with only one minute legs. I threw my $0.02 since I've experienced this on dark and stormy nights before.

 

Of course, I've never been wrong....... ;)

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Hi Vaughan- I suppose what I was saying in my post is that I've seen this exact thing happen in a Lear Jet, Saab 340, EMB-120, 737, you get the drift. I do not think it's a problem related to the software coding, but how a high performance airplane deals with holding patterns with only one minute legs. I threw my $0.02 since I've experienced this on dark and stormy nights before.

 

Of course, I've never been wrong....... ;)

Matt,

 

I understand what you mean.

I am only PP-ASEL.

But, been flying Sim props/jets for many years.

If I run into a problem like this ... no problem recovering.

 

My question was just about the PMDG737 getting into this hold ... parallel / teardrop // whatever is supposed to happen at this hold from KSAN ILS09.

 

Edit:

Navigraph holds / leg time or distance are generally either 1 minute or 4nm ...

 

 

I also double checked the 737 FCOM.

 

Holding

The FMC computes holding patterns with constant radius turns based on current

winds and FMC commanded airspeed. The pattern size is limited to FAA or ICAO

protected airspace. In LNAV, the AFDS tracks the holding pattern using up to a 30

degree bank angle. Strong winds or airspeed in excess of FAA or ICAO entry

speeds may result in the airplane flying outside the protected airspace.

With LNAV active before sequencing the holding fix, holding pattern entries are

determined by the following:

• the angle between the flight plan leg into the holding fix and the holding

inbound course determines the entry method used (parallel, teardrop or

direct entry)

• the airplane flies the initial outbound leg for a specified time (1.0 minute

at or below 14,000 feet and 1.5 minutes above 14,000 feet)

• teardrop entries use an FMC calculated offset angle designed to intercept

the outbound leg at the point where the inbound turn begins

• parallel and teardrop entries may cause the airplane to fly beyond the

displayed holding pattern; however, the airplane remains in protected

FAA or ICAO limits.

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Did a couple more tests this morning with FSX and P3D.
New short route KNKX KSAN
Rebooted PC between all test flight.
Saved both the flights (FSX/P3D) during departure.

First tests, original full route (not a saved flight).
While enroute (FSX/P3D) I diverted to the hold.
All ok entering the hold, teardrop, pattern and exit (screenshot).


Resbooted PC, started (FSX/P3D) and loaded the saved flight.
While enroute I diverted to the hold.

Bad hold entry .. flew circles (FSX and P3D) (screenshot).

So, what i found so far:
LNAV, VNAV and HOLDS on full routes all ok but the HOLD is failing on saved flights (FSX and P3D)?

1-PMDG-737-600-FSX-GOOD-HOLD_zps8dahth1e

2-pmdg737-600-FSX-saved-flight-bad-hold_
 

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Saved (P3D) flight KPHX, at TOD, into KLAX, SEAVU2, ILS24L.

While on approach to ILS24L, JULLI.
Diverted to hold at RAFFS / HOLD.
I did a video (if it is needed).


At RAFFS, LNAV did a right turn and flew circles.

All saved flights so far (FSX and P3D) are not allowing proper hold entry (e.g., teardrop/direct) and are failing the LNAV holding pattern.

I wonder if this problem is only with the PMDG737 or could it also be in the PMDG777 and 747-400?


PMDG737-600-savedflt-bad-hold-P3D-1a_zps

PMDG737-600-savedflt-bad-hold-P3D-1b_zps
 

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I submitted a PMDG-737 support ticket on this problem of later reloading a saved flight (which had FMC/CDU ILS APPR and hold) not flying the holding pattern.
My PC: PMDG737NGX VERSION v1.10.6461 (FSX/P3D) / Win7-64.


I got a reply confirming it is a problem with the PMDG737 and may also be a problem with the PMDG777 (747?).
I was given a work a round (for PMDG737 for FSX and P3D) until the problem can be fixed in a future PMDG737 update.



Note:
I also asked a couple follow up questions and got replies:

1. Pilots doing long hauls and e.g. saving their flight enroute (in case of OOM's/crashes on approach) are not aware that a later go-around / hold will fail when they reloaded their saved flight.
Adding this problem/work a round solution to the PMDG Knowledge-base would be good for pilots searching HOLD problems before creating a support ticket.

The reply was that they will try to work up a Knowledge base article on the issue in the next few weeks as they are trying to wrap up the 747-400 V3 at this point .

**

2. Does this problem exist in other PMDG aircraft (I have not purchased yet) ...e.g., MD11, 747 , 777 ?
It is believed to exist on the PMDG777 but has not been confirmed yet.

Maybe one of you 777 drivers could check it out?



Recap problem work around:

Create a full route flight: SID, route, STAR, arrival ILS approach loaded (with a hold in FMC/CDU as part of the approach selected) into FMC/CDU and fly it.
Note: Flying a normal approach / go around / holding pattern will be ok.
During the flight (e.g., nearing TOD) save the flight for later use.
Or e.g., sometime during the approach legs I (FMC/CDU) line select the Holding fix LNAV will fly to the hold fix, enter the holding pattern and fly the hold properly.



Next day fly the saved flight.
Go around .. LNAV will fly to the holding fix but never enter the hold. Aircraft will fly CW circles.
Another test: If sometime during the approach legs I (FMC/CDU) line select the Holding fix LNAV will fly to the hold fix, then turn right, do clockwise turns, never entering the hold.


The work a round :
After loading a saved flight delete the hold and then enter it again.


 

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