Why can't I perform dual channel autolands?

[victorlima01 2]

htHi all, I have been having problems with autolands. When setting up the aircraft during descent for an autoland procedure in an ILS equipped airport, I proceed in the following way: I tune both nav radios to the ils freq, press the vor/loc button on the MCP and the aircraft faithfully captures the localizer. I then proceed with flap extensions speeding down to vref etc and when the Glideslope becomes alive I'm all set up and I press app on the MCP and then press the second autopilot command button (i.e if I were using CMD A for loc capture and descent I press CMD B as well for full autoland). The aircraft then flawlessly performs an autoland (better than my manual landings I might add). The problem is that I consistently get a yellow SINGLE CHANNEL message on the FMA when I press app and select the second autopilot. From what I know of the airplane that warning is inconsistent with a full autoland correct? If so, then how come the aircraft lands perfectly? Am I missing something to execute a dual channel autoland? BTW, what is the difference between the single channel and dual channel procedures?thanks for the help. Regards, Victor

[michal 44]

Yes, aircraft can auto-land in single channel but technically pilots should never do it (it would probably be a violation of some sort). With a single channel there is no redundancy. Dual or triple channel provides additional redundancy in case one of the channel fails. I hope someone else will help you with the rest.Michael J.WinXP-Home SP2,AMD64 3500+,Abit AV8,Radeon X800Pro,36GB Raptor,1GB PC3200,Audigy 2http://www.precisionmanuals.com/images/forum/747400.jpg

[Guest aarskringspier]

Does it stay as single channel until touchdown? Or does it do a self test, flash then display dual channel at arouind 2500 feet? It will always say single channel up to this point upon which it does sort of a self certification and then locks both channels to the ILSI could be wrong, Im still learning myself so if I am I blame it on the fact Im half retarded on my fathers side.

[CF104 0]

Actually the NG can't Autoland in single channel. Flare mode is only armed and available in Dual Channel.Some aircraft other than the NG can Autoland with one AP but only down to CatIIIa limits. CatIIIb/c require two or more autopilots.JohnBoeing 727/737 & Lockheed C-130/L-100 Mechanichttp://www.precisionmanuals.com/images/forum/ng_driver.jpg

[Guest jase439]

First, before doing anything I make sure BOTH NAV radios are tuned to the ILS frequency, before intercepting the localizer. I also set the CRS OBS to the appropriate inbound course. When I'm first capturing the localizer (generally above 2500' AGL), I'm running with a single autopilot. 1CH illuminates in the AFDS. After loc capture, I pick up the glideslope and follow it down to 1500' AGL - where the deviation cues flash yellow. After this point (but before 1000' AGL), I arm the second autopilot (you can't arm the second A/P before this point). This arms "Flare" mode and the 1CH annunciation is extinguished. Then its just a matter of letting autoland do its thing.Hope this helps.J

[Mats_J 2]

Victor,This is as it should be. The SINGLE CH annunciation should be there until 1500 feet where the CMD (dual channel) kicks in. You should also see FLARE armed on the FMA. Is this what you are seeing as well?HOpe it helps,

[clayton4115 56]

you want like this?:( http://forums.avsim.net/user_files/117805.gif