Failed autoland on PMDG 737NGX at KSNA ILS19R, rapid descent just prior to reaching runway

[weekend_pilot 0]

I have flown the flightpath from KOAK to KSNA on the PMDG 737NGX prior without any issues using the autoland on ILS 19R.  However recently I have been having problems with the autoland functionality. In my case just prior to reaching the runway, the aircraft will rapidly descend and my display goes from "Land 3" to "no autoland/apch warn".  I found a similiar problem described here http://forum.avsim.net/topic/441447-autoland-disaster/.

 

I am trying to ascertain if this is a FSX bug or am I doing something wrong that I must be forgetting from the past successful landings.  Below is some information on my setup:

 

[Procedures]

* FSX

* PMDG 737-700 NGX

* AIRAC 1407

 

I am flying from KOAK to KSNA during my descent into the Los Angeles region, I perform the following:

 

* Set both nav radios to KSNA ILS 19R frequency

* Set the HGS runway elevation to 54 and runway length to 5701 I got these values from the IFR plate for 19R

* I set both course headings for the Captain and FO to 194

* I have set a 30 degree approach in the FMC

 

As I approach SNAKE (int) I am at an altitude of around 3600, when I am turning to align with the runway I press the VOR/LOC button once I am facing the airport I press the APP to lock on to the glidescope, shortly after this I press CMD B and both channels are active. I then set the MCP speed to the flaps 30 which is somwhere between 133-135.

 

During this time I am extending my flaps at the correct interval when I get to flaps 15 I drop my gear, as I get close to the runway everything is great speed is good and I am at flaps 30. However just prior to reaching the runwayr, the plane will descend quickly and "no autoland" will be displayed. It should be noted that it is not stalling as it appears the autopilot is adjuting power and dropping the nose to get lower.  If i continue on that course it will drop the plane a few 300-400 feet in front of the runway.  To work around this I simply shutdown autopilot all together and take the aircraft in myself, but I have in the past used the autoland feature on ILS 19R without issue.

 

[system Info]

It should be noted that I do have a dated system, on average I may only get between 8-12 fps when in these approaches so while frustrating, that could be contributing to the issues.  FSX is CPU bound too, so any interrupts will cause every so slight pauses which could be contributing to the issue too. However I was able to complete these approaches using the same system in the past. My installation though has been redone.

 

Is there anything specific about 19R that I should know about, that maybe is a bug in FSX?  Is it possible that the system itself could be contributing to the problems as well?  Thanks again for any help and advice.

 

Best Regards,

[Captain Kevin 586]

You might want to redownload and reinstall AIRAC 1407, I thought I read somewhere that there was a glitch with it that they needed to provide an update for, I'm not sure if that would have anything to do with it.

[weekend_pilot 0]

Thanks Kevin, I will give that a try. I will post back with results.

 

I am not a real pilot so it is highly likely I am doing something wrong too. Thank you again for your response, very much appreciated.

[Kerlix 99]

Could this be caused by wake turbulence pushing the A/P into a situation it's not able to deal with?

[77west 139]

Could this be caused by wake turbulence pushing the A/P into a situation it's not able to deal with?

 

I would not expect anything going into SNA to cause a 737 wake issues, unless you were closely following a 757. Certainly no real heavies there.

[weekend_pilot 0]

My traffic settings are minimal and I am not trailing anyone. Also I was unaware that FSX could even simulate wake turbulence.

 

From a high level standpoint do the ILS procedures I am following look ok, or is KSNA ILS 19R a more complicated approach in FSX?

 

Thanks again!

[Captain Kevin 586]

I would not expect anything going into SNA to cause a 737 wake issues, unless you were closely following a 757. Certainly no real heavies there.

 

My traffic settings are minimal and I am not trailing anyone. Also I was unaware that FSX could even simulate wake turbulence.

 

From a high level standpoint do the ILS procedures I am following look ok, or is KSNA ILS 19R a more complicated approach in FSX?

 

Thanks again!

From a realism standpoint, you shouldn't have a wake turbulence issue, I don't think, but if you're using a third-party weather engine, I forget which one it was, but there was one that simulated wake turbulence rather unrealistically from what I understood. I personally don't have it, so I can't comment on it.

[weekend_pilot 0]

I retested the flight by resetting all of my settings in FSX.  It turns out everything landed without any problems. The same procedures set me right on the runway, so I believe it was probably a configuration issue.

 

* I reset all graphic settings to default

* Restored original fsx.cfg

 

To further test this and rule out it being my system, I fired up REX to add some load. The same result, the ILS landing was successful at KSNA.  So in my case I do feel it had something to do with the FSX configuration causing the initial issue.  Thanks again to everyone that responded.