Just flew into MCO (18R), and for some strange reason the ILS display (ID and course) in the upper left of the PFD was in yellow with a line through it, even though the correct frequency was tuned and the correct course was set.Had no trouble with the approach itself aside from that.

Actually you have to tune both NAV radios to the ILS freq to get rid of the strike-though and the yellow indication. Don't know how it works in real life though with regards to tuning one or two radios to get rid of the line.This from the BOEING OPSMNL:8<---1 Approach ReferenceDisplays the selected ILS identifier or frequency, approach front course, and ILS/DME distance.If the tuned ILS frequencies disagree, the frequency turns amber with an amber horizontal line through it.If the approach courses entered in the MCP disagree, the course turns amber with an amber horizontal line through it.8<---My highlighting seems to indicate that both radios has to be tuned.Hope it helps,

>Displays the selected ILS identifier or frequency, approach>front course, and ILS/DME distance.>If the tuned ILS frequencies disagree, the frequency>turns amber with an amber horizontal line through it.>If the approach courses entered in the MCP disagree, the>course turns amber with an amber horizontal line through it.>8<--->>My highlighting seems to indicate that both radios has to be>tuned.Big help - thanks! I'll see what happens next flight...

Hmm... always two radios? But how can I get the DME then if I example want to take it from airport VOR?

737 Operators Manual says:RW/APP CRS ERROR - U10.4 and later: During approach, MCP selected course does not match front course for the approach in the active flight planRW/APP TUNE DISAGREE - U10.4 and later: During apprroch, manual tuned approach frquency or channel does not match active flight plan.The RW/APP CRS ERROR message doesn't seem correct.Floyd

What do you mean "is does not seem correct"? What about it is incorrect? If you do not set the MCP CRS window in approach mode to the final appraoch course you will get this message. Works just like the real deal... [h4]Best Wishes,Randy J. Smithhttp://www.precisionmanuals.com/images/forum/betaimg.jpgAMD 64 3200+ | ASUS KV8 DELUXE | GFORCE 5700 ULTRA @535/1000 | WD SATA 80 GIG | 512 DDR 400 |

OK, I stand corrected. Floyd

In the downloadable tutorial by Fred Clausen (much thanks Fred) he adds a bit of trivia saying the second autopilot gets its height/heading information from the NAV 2 radio. Apparently this and arming the second autopilot is required for a full CAT III autoland. I suppose in the real work this is to protect against critical failure during approach.cheers, Nick

On a real CatIII approach the second autopilot uses the Nav2 radio for ILS guidance. A/P 1 uses HYD A for control surfaces, A/P 2 uses HUD B for control surfaces, so effectively the A/P's are using different control surfaces to fly the aircraft, (note this is greatly simplified so don't come back at me with Ops manual stuff... I get enough of that at work). If there is a significant error between either A/P control inputs then the A/P's will both drop out, this is called FAIL PASSIVE. This avoids crossed controls and all manner of other problems. The reason both drop out is that with only 2 A/P's there is no way to tell which is incorrect! If you have 3 A/P's like some Airbusses or the B747 etc then if you have one wrong a/p then the other 2 will realise which one is incorrect and drop it out continuing on the remaining 2 a/p's.Hope that helpsKris

"the second autopilot gets its height/heading information from the NAV 2 radio."I'd be very interested to know how NAV 2 supplies height information.Fred?Thanks.Cheers.Ian.

just ignore the amber strikeout...cheers

Sorry that was my misquote my apologies. Fred did not say that, in his tutorial it states, "...pitch and roll...". I assumes this means height/heading.cheers, Nick