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Guest georg

Two issues: TO thrust mode stays selected / transition altitude on descend

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Guest georg

Hello,I've done some intensive flying the last two days (400F) and so far I have encountered two issues which confuse me. May be my mistake, but cannot find the solution myself.1) On preflight I select the approrpiate Thrust Limit mode in the FMC and I usually choose one of the available de-rates instead of entering the temperature. After take-off the CLB or CLB2 mode, as previously selected, used to kick in after I selected flaps 5 I think, but yesterday on two of my last flights the TO mode stayed on and there was no way I could change it myself despite all the efforts made. When reaching cruise altitude, the TO mode changed to CRZ and then the FMC switched into the "airborne" thrust limit mode where I can select G/A, CON, CRZ, CLB, CLB1 and CLB2. Any idea what caused such problem? Isn't there any way on the 747 to forcefully select a thrust limit mode like on the 767 (buttons by the upper EICAS)?2) Inserting the transition altitude on CLB page during preflight works just fine and all the entries on the LEGS page have appropriate altitudes shown as FLs according to the chosen trans alt. However, after getting airborne and later when descending, the transition altitude or actually trans level this time, changes automatically to 18000 feet and I think there is no place for changing it. Other FMCs have usually kept the altitude which was selected on the CLB page, but this seems to be resetting it automatically. Is this a normal behaviour?Thank you very much!

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Guest georg

Thanks for that! But what about the first one, anyone?

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Georg,The transition to CLB mode should take place at the thrust reduction point specified on the TAKEOFF REF PAGE. This is usually Flaps 5, but can be set to an altitude as well.

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"This is usually Flaps 5, but can be set to an altitude as well."More specifically, a height (barometrically calculated) above the airfield.Georg... Did you arm VNAV prior to TO? This might help ;)Cheers.Q>

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>To your second question: Have a look to VNAV DES FORECAST.>There you can fill in the transition altitude.Just to clarify:Climb - use TA, transition altitude (VNAV CLB)Descend - use TL, transition level (VNAV DES)

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Guest georg

I know TA and TL, just didn't know where TL can be entered in the FMC. Thanks for all the help. At least yesterday the CLB mode worked so I hope it will next time as well. I am used to switching LNAV on after having retracted the flaps (767 procedures), but I am not sure if this is correct for 747. Should I enable it earlier?

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