With both radios tuned to ILS frequency, both flight directors on, gs on in fmc, vor/loc to app and then autopilot A and B armed the 737-900ER NGXu has TWICE failed to autoland, once not capturing g/s and overflying and just now at sydney airport stalling and falling into the water short of the runway. I am going for a third try now, could really use some help here

Note: the PFD is displaying SINGLE CH throughout the flight despite both fd being on, both crs set to runway heading and both nav radios being set to ILS freq

Update just failed a third time, went drastically below G/s and had to take over throttle control to save it. Same setup, really not sure what's going on with the SINGLE CH and throttle specifically

Fourth time. All good right up until about altitude 400ft. Autothrottle tried to go around again. All seemed fine beforehand. Any help appreciated

Have you used Makerunways and is your MagDec up to date?

not  sure  about  this  i remembered  awhile  back  there  is  a certain  rwy  that  wrong  with the  ils  and  everyone  had  issues,  see  above post  as well,  using  the  stock  sydney  airport  or  fstampa?  what  rwy  your  using  so  can  give  it  a try myself  to  check, or  you  can  try  a  different  rwy  your  self  see if  you get  the same  issues

Edited April 14, 20206 yr by pete_auau

3 minutes ago, pete_auau said:

not  sure  about  this  i remembered  awhile  back  there  is  a certain  rwy  that  wrong  with the  ils  and  everyone  had  issues,  see  above post  as well,  using  the  stock  sydney  airport  or  fstampa?  what  rwy  your  using  so  can  give  it  a try myself  to  check, or  you  can  try  a  different  rwy  your  self  see if  you get  the same  issues

Using runway 34L flytampa. Once I did a full set up, SID and then STAR, then i got sick of a 30m flight for one f***ing landing so I just would set up pos init and then slew out 10/15nm and about 3000ft and go from there. Just had a successful although it was very glitchy with the CMDB toggle 

if i remember well autoland capability is only when u use full flaps. did u ?

Make sure you are fully configured for landing at SOSIJ. That means flaps down ,gear down and on speed. 800/900 if you are trying to slow the aircraft it will NOT descend and you will miss your approach and lose auto land. If you dial back the speed the aircraft will remain level till the speed drops off.  

Remember you can go down or slow down but not both.

I have the same problems with my 737 800 NGXu. My last flights have been ok ,until the landing. I experience the same stange behavior as you describe of autopilot and autothrottle, and some times the plane crashes, sometimes I manage to land manually, but one of the problems is that the speed is very difficult to reduse under 160 knots on final. I always use Active Sky for weather when I fly, so I wander if the beavior is connected to the last update of AS, because I had no problems autoland the aircraft some weeks ago.

Tor Arild Danielsen

Again the 800/900 series does not like to slow down. The 747 and 777 lose speed quickly when you cut power the 800/900s don't. If you drop the nose to get on glideslope you will pick up speed. This is how the RL aircraft works confirmed by the 737 pilots on the test team. You really have to plan ahead for approach in this bird.

If you get to a decel point the aircraft will STAY level regardless of the descent profile till it burns off speed. Then it will descend again. So plan your decel poins way out. If you are descending and you try to slow down the aircraft will level off to slow down.

Depending on the approach you are flying starting your descent at the TOD point is really critical. If you blow by the initial TOD the whole thing becomes a problem from there.

The autoland problem, seems not have to do with the way we fly the descend. On the PMDG 737NGXu forum, I found a solution. Search for the thread  NO AUTOLAND NO LAND3. The reason for the problems is a conflict between PaneState files in Prepar3dv4..... PMDG\ PMDG737NGXu\ PanelState folder. Deleting the files in this folder was the solution for me. 

Tor Arild Danielsen