Ok, here is a screenshot: I just enabled APP (after intercepting LOC) and after that I pressed Cmd B. As you can see this automatically disabled Cmd A... I had to wait until I could enter Vref (and GS was intercepted by then) before I could enable BOTH AP's! http://fsfiles.org/flightsimshots/images/2112011_9_4_15_45_20_169_.jpg (Post a link due to the size.)

Just saw your picture. You are still in VNAV mode, the G/S is only armed. Also at 16 miles 226 kts is pretty fast. Come out of VNAV to Alt Hold then press the second autopilot. Steve Aull

I know I was still in VNAV and that G/S was armed... er... I don't see what this has to do with Cmd B disabling Cmd A after turning on APP...? I also know 226 is pretty fast, but I let the FMC calculate everything and landing always goes perfectly well. The tutorial nor anyone else said you have to go to Alt Hold in order to enable the second AP: it's just that Fred said you should be able to turn on the 2nd ap after turning on APP, period, but that just doesn't work: turning on the 2nd AP turns off the 1st one until I am able to enter Vref into the MCP... Mind you, I don't have any problems with anything! I can land perfectly fine: if Fred hadn't said there is something wrong because I can't enable the 2nd AP after turning on APP, I wouldn't have posted that screenshot at all.

The reason you are having to wait till after the glideslope is intercepted is the system uses only one autopilot in LNAV or VNAV. Once on the glideslope and VNAV light (FMA) is out then you can use 2 autopilots. If you want both autopilots armed before then you'll have to be out of VNAV. If both localizer and glideslope pointers are pink then you can have both autopilots. If you notice since you are in VNAV Alt the glideslope pointer is white. Just because the APP button is lit up on MCP does not mean APP mode is armed. Always rely on what the FMA on the PFD is showing. If ALT hold mode was selected in your situation the G/S pointer would turn pink. Then you may arm the opposite autopilot before G/S interception. Nothing says you can't do it your way...Just food for thought. Steve Aull

At this stage in the APP another reason to be out of VNAV is that sometimes VNAV will stay in command way to long and the G/S will arm late in the situation. In the real world (ATC) environment more than likely you would have been assigned an alt prior to beginning of the APP and also a speed limit for spacing. While all this can be accomplished with VNAV you end up spending more time programing FMC and using ALT intervention. Once you are on your final alt assignment it is just easier to go to ALT hold and start dialing your required speed in the speed window. Steve Aull

Ok, cool, thanks for the information! I understand it now. But this means Fred's remark that you should be able to enable the 2nd AP after turning on APP no matter what, was a bit er... misleading... Anyway, I now know how it works and why it works like that, which is always great, of course. Thanks again!

Ok, cool, thanks for the information! I understand it now. But this means Fred's remark that you should be able to enable the 2nd AP after turning on APP no matter what, was a bit er... misleading... Anyway, I now know how it works and why it works like that, which is always great, of course. Thanks again!

Sory if was misleading but it is the proper way to do it !! In the Pic I notice that you are now too low for glideslope capture and that is why VNAV is still controlling the pitch.You have " nissed " the glideslope so the second autopilot cannot engage !! I also noticed that the FO's FD is the MASTER (MA green light)This should not be a problem provide it works properly in the NGX.It might be safer to always turn on the Captains Flight Director first.

Sory if was misleading but it is the proper way to do it !! In the Pic I notice that you are now too low for glideslope capture and that is why VNAV is still controlling the pitch.You have " nissed " the glideslope so the second autopilot cannot engage !! I also noticed that the FO's FD is the MASTER (MA green light)This should not be a problem provide it works properly in the NGX.It might be safer to always turn on the Captains Flight Director first.

Ok, got it. In this case VNAV will stay on until I 'reach' the glideslope, which is quite late because I am too low... and hence I can only enable the 2nd AP quite late. About the FO's FD being the master: that's due to enabling Cmd B. I usually use Cmd A and then the Captain's FD is master, but when I enable Cmd B (too soon), Cmd A simply is turned off and CMd B and hance the FO's FD is taking care of things. When I click Cmd A at that moment, Cmd B will be turned off and the Captain's FD is master again. Anyway, I see I have to come in a bit slower and higher too in order to do things more properly!

They have a lot to learn yet Fred !!

You're so right...

I have the same problem and can not figure it out.I'm on short finale GS is captured, im VR+5 and when I hit CMD2 it comes on for 2 sec and shuts off and get no retard arm or flare arm.Tried several things and still not working. Got it at one point switching from CMD1 to CMD2 and back and forth. Anyways hop there is a fix or some one can come up with the right way to arm auto land cuz its getting frustrating.

I have the same problem about the CMD A and CMD B ( both VHF NAV receivers must be tuned to the ILS frequency and both autopilots must be selected in CMD prior to 800 feet RA). it works for me to engage both CMD.

this last comment work for me thanks

In a real world situation here in the USA, with atc giving you speed assignments and vectors to intercept the LOC, it's Alt Hold and Hdg Sel, VOR/LOC / APP, then cmd B. Simple and you get the same outcome..

After running several flight tests based on all the theories put forth in this post, here is what I found out. Seems that three provisions have to be satisfied in the simulation. One, the localizer has to be active. Two, the GS has to be active. And three, you have to have selected either flaps 30 or flaps 40. THEN both CMD lights will remain on. I usually intercept the localizer well before I reach the FAF or OM and in RW I used to maintain 170K til the marker. So if I do that with the simulation, it will not allow me to keep both CMD active until after I have configured for final approach with approach flaps set. On another issue, it was stated that LAND 2 would be displayed if ISFD were reset during approach but I could not make that happen. I have never seen an instance where LAND 2 was actually displayed but it is often so in the FCOM. I can only imagine that it is a fallback display if a failure has occured prior to 500 agl since I am using Fail OP settings (?) Has anyone actually flown an approach where LAND 2 was being displayed? FCOM shows it displayed with only one CMD activated since a CAT II can be flown with only 1 AP on the real NG.

After running several flight tests based on all the theories put forth in this post, here is what I found out. Seems that three provisions have to be satisfied in the simulation. One, the localizer has to be active. Two, the GS has to be active. And three, you have to have selected either flaps 30 or flaps 40. THEN both CMD lights will remain on. I usually intercept the localizer well before I reach the FAF or OM and in RW I used to maintain 170K til the marker. So if I do that with the simulation, it will not allow me to keep both CMD active until after I have configured for final approach with approach flaps set. On another issue, it was stated that LAND 2 would be displayed if ISFD were reset during approach but I could not make that happen. I have never seen an instance where LAND 2 was actually displayed but it is often so in the FCOM. I can only imagine that it is a fallback display if a failure has occured prior to 500 agl since I am using Fail OP settings (?) Has anyone actually flown an approach where LAND 2 was being displayed? FCOM shows it displayed with only one CMD activated since a CAT II can be flown with only 1 AP on the real NG.

Hi ! You will see Land 2 if you set the ISFD to fail in the failures section of the CDU.A full autoland with Rollout & Flare is possible. As regard the flaps 30 or 40 setting, that has nothing to so with being able to select both autopilots.You need to be on an intercept for the localizer and not too high for the glideslope.

Hi Fred! What I explained was what I found when testing the simulation. Naturally you have to be on an intercept and at an altitude below the GS! I didn't mention those requirements because I assumed we all were doing that! But what I am relating is what the simulation is requiring. I agree with you that in the RW that is probably as it should be. With the other PMDG simulation (B744) that I have that in fact is the case and also with the Level D, and the Super 80, but the NGX will just not sustain the second CMD active until I select flaps 30 or flaps 40. From what you say this is obviously something that departs from reality.