Hello Mates,

A little bit before the final, I press APP + CMD B to arm the ILS capture. I do it quickly especially for CMD B because I know that later CMB might be no more active.

In this case (screenshot below) I get SINGLE CH, but I should have AUTOLAND since the FMA annunciates 2 axes: VOR/LOC and G/S?

You should enable both autopilots to get autoland 3

after pressing APP + CMD A + CMDB, doesn't the ILS single ch switch to dual ch after it catches the gs and at 1100-1500 feet above ground? been a while since i flew it.

25 minutes ago, solito said:

You should enable both autopilots to get autoland 3

I pressed CMD A and CMD B and they illuminate so I have both autopilot?

4 minutes ago, Fromage_Flippant said:

after pressing APP + CMD A + CMDB, doesn't the ILS single ch switch to dual ch after it catches the gs and at 1100-1500 feet above ground? been a while since i flew it.

On the screenshot I was at 3 160 ft and just after that I went manual (FD). You might be right: the autoland may activate at a lower altitude.

1 minute ago, LRBS said:

Thanks, 1,2,3,4,5,6 conditions are met.

7 (altitude) is not met, that's why I think.

Thanks!

Yup. Regardless of whether you're using fail passive or fail operational, you won't see the final autoland mode displayed until the test is complete around 1200ft (LAND3 for fail operational, and FLARE armed for fail passive).

As long as the green lights in both CMD buttons are illuminated on the mode control panel, the airplane intends to autoland. Just press on and ensure you have the correct flight mode annunciations no later than around 1000ft.

Can we see the approach chart for the airport you were attempting to land at please?

4 hours ago, Maxis said:

Can we see the approach chart for the airport you were attempting to land at please?

It was in Switzerland I believe but I don't recall the exact approach, sorry.

Thanks to all, my question has been fully answered.

Edited Wednesday at 05:33 PM1 day by Simicro

I belive there is yet another nuance in the 737s - between fail passive and fail operational equipped aircraft, there'as also a difference in the way the aircraft tries to maintain the centerline (rollout) in an autoland, commanding rudder inputs, or the pilots have to promptly disengage the AP and AT right after touch down and continue to steer the aircfraft with rudder themselves...

´´´´´´

Edited Wednesday at 10:27 PM1 day by jcomm

Aye. It's why fail operational aircraft need to be equipped with the ISFD as well; that provides input for the 3rd axis of the autopilot. That's where the name comes from; if an autopilot channel fails you've still got two left, and the system has just degraded into two channel mode, so autoland is still "operational".

The thing about fail operational, though, is that there's no real operational "bang for your buck.". It buys you the same weather minima as a fail passive aircraft with the HGS. It's apparently cheaper to maintain a fail passive system plus the HGS, and you get the same low weather landing minima, and you also get all the other operational benefits of the HGS. It's why fail operational is not as common in 73s these days.

@Stearmandriver , thx for the great explanation !

I learned just now that some early 732's and operators did also have Paravisual displays for LVOs

I did know the 747's up to the 744 could be quipped with it, but never seen in in 737s...

15 hours ago, Simicro said:

It was in Switzerland I believe but I don't recall the exact approach, sorry.

I don't think it could have been Switzerland because the baro minima show 286 feet (and the altitude versus DME is also consistent with a roughly sea-level airport), while the lowest elevation in Switzerland is 633 feet.

I haven't been able to work out which airport this actually is though.

Found it: It's the ILS 09 at DAAG (Algiers, Algeria).

9 hours ago, weaklink said:

Found it: It's the ILS 09 at DAAG (Algiers, Algeria).

Yes correct 👍 I flew there indeed. I recall now!