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Guest tmetzinger

autoland question for real-world drivers

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At what point in an autoland do you disengage the autopilot? After touchdown, or after the aircraft is stopped or exiting the runway?Thanks in advance!

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Timothy,I'm not a r/w driver, but I can answer this one with certainty though.The autopilots should be disconnected IMMEDIATELY after touchdown. The autothrottle will disconnect automatically 2 seconds after touchdown.Hope this helps!Tero

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>Timothy,>>I'm not a r/w driver, but I can answer this one with certainty>though.>>The autopilots should be disconnected IMMEDIATELY after>touchdown. The autothrottle will disconnect automatically 2>seconds after touchdown.>>Hope this helps!>>Tero>Thanks! I'll adjust accordingly

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On the 744s they can be left On as long as you are on a CATIII approach. (Rollout + Flare Indications > 3 AP CMD ON)You then disconnect it when you whish to taxi, or whenever you feel like it unless you want to remain at the runway centerline ;)I don't know if it works like this on the NGs, though.Bruno Francescoli.

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>On the 744s they can be left On as long as you are on a>CATIII approach. (Rollout + Flare Indications > 3 AP CMD ON)>>You then disconnect it when you whish to taxi, or whenever you>feel like it unless you want to remain at the runway>centerline ;)>>I don't know if it works like this on the NGs, though.>>Bruno Francescoli.I don't either, so I hope a real driver chimes in soon!

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"On the 744s they can be left On as long as you are on a CATIII approach. (Rollout + Flare Indications > 3 AP CMD ON)"Hi, Bruno.I've been told that there is rollout function on the NG (i.e. no lateral guidance after touchdown). A newer, more sophisticated A/P system has been fitted to our latest NG's.... but I can't recall if rollout was an option on these or, if it was, whether it was active. I may have to re-read my Maintenance Memos ;-)).Cheers.Ian.

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Ian, we have the newer A/P systems on our 73Gs too but they are not yet CAT IIIb. I don't know if CAT IIIb has been installed on any 737NG in the world yet. Browsing through a recent Boeing AERO mag, they were still in development. It would require extensive modification to nosewheel and rudder, since the autopilot in current aircraft has absolutely no control over them, which is needs to have for rollout guidance.On 747-400, 757, 767 and 777s, you have CAT IIIb qualified autopilots, which provide rollout guidance through rudder and nosewheel steering. There, you can leave the autopilot on, until it comes to a full stop on the runway, if you like.On the 737 (CAT IIIa only), you MUST disengage the autopilot right after touchdown since it has no rollout guidance and may cause you problems, especially when doing an autoland during a crosswind (aircraft touching down with a crab angle).

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>Ian, we have the newer A/P systems on our 73Gs too but they>are not yet CAT IIIb. I don't know if CAT IIIb has been>installed on any 737NG in the world yet. Browsing through a>recent Boeing AERO mag, they were still in development. It>would require extensive modification to nosewheel and rudder,>since the autopilot in current aircraft has absolutely no>control over them, which is needs to have for rollout>guidance.>>On 747-400, 757, 767 and 777s, you have CAT IIIb qualified>autopilots, which provide rollout guidance through rudder and>nosewheel steering. There, you can leave the autopilot on,>until it comes to a full stop on the runway, if you like.>>On the 737 (CAT IIIa only), you MUST disengage the autopilot>right after touchdown since it has no rollout guidance and may>cause you problems, especially when doing an autoland during a>crosswind (aircraft touching down with a crab angle).Thanks, Iz, that was the authoritative answer I was looking for. The training and ops manual specified disconnection at touchdown, but didn't have any discussion of the IIIa/IIIb status of the airplane.

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Thanks, Iz.I confirmed today that our latest NG's also have the new Rockwell Collins Enhanced Digital Flight Control System (=A/P) with the "option" of Cat3b (not implemented). Seems a bit pointless installing a high tech computer without the necessary hardware, doesn't it???Cheers.Ian.

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You're welcome Ian and Timothy. Our systems have been upgraded to the newer MMR (multi-mode receivers) that are also capable of GLS and other curved precision approaches, though, I've never seen one of those approaches implemented yet. I think yours will have that capability too, with the new AFDS. We're just now starting to see more LNAV-VNAV approaches (making non-precision approaches such as an NDB approach, a total breeze), but I would sure like to see those curved precision approaches implemented.

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>Thanks, Iz.>I confirmed today that our latest NG's also have the new>Rockwell Collins Enhanced Digital Flight Control System (=A/P)>with the "option" of Cat3b (not implemented). Seems a bit>pointless installing a high tech computer without the>necessary hardware, doesn't it???>>Cheers.>Ian.Well, I guess if that RCEDFCS is common with other airplanes in the fleet, it may end up saving money on maintenance, even if you never upgrade the nose-end stuff for IIIb.

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I disconnect the auto-land function/autopilot at the middle marker, just after dropping the gear. Thats just me though. Josh

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I disconnect the auto-land function/autopilot at the middle marker, just after dropping the gear. Thats just me though. JoshDOUBLE POST, SORRY!

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Josh,This thread is about when autoland has to be done (ie. CATII and CATIII operations), and how autopilot should be properly disconnected after the autoland.Of course in CATI and visual operations one can disconnect the automatics when it feels right.Tero

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