Profile?

[Guest meekal]

Hi,Does Profile have to be re-engaged at TOD? Somethimes she just keeps going...........Meekal

[Jeffrey L. Whitaker 0]

Meekal,No. Provided you have set the appropriate altitude/speed constraints in your FMC the PROF mode will do the rest. Ensure you have reset the MCP altitude prior to the TOD.JW

[Guest PPSFA]

Occasionaly I have had that problem, my solution is to set the appropiate lower altitude before the TOD, then hit the PROF button again. The annunciator will light its armed, end of problem

[Guest meekal]

Occasionaly I have had that problem, my solution is to set the appropiate lower altitude before the TOD, then hit the PROF button again. The annunciator will light its armed, end of problem

Of course I set the lower alt. before TOD. But Jay says he hits it again. That was my question. I would imagine one does not have to because once you set the lower alt. it says Prof to XXX, while you are Holding YYY), and one assumes it is armed. It should descend at the TOD.I guess it is random thing by the sound of it. I had a roughly similar problem with FMS speed. It refused to engage (go blank) so I had to twiddle it myself. The HDG and VS were blanked.Meekal

[Guest D17S]

Watch the colors above the altitude tape. Both the mode and the altitude must be magenta (Magenta = FMC controlled. White = MCP. controlled. If the altitude or mode is white, you'll just sail by TOD). As you spool down the MCP alt window, the window's setting will appear in white above the magenta mode and alt. It will flash just before you nose over into the descent.Save a flight 10 miles before TOD and play with stuff. There are numerous ways undo a perfectly good, FMC'd TOD, but always a way to get back. There's a lot going on there.

[Guest meekal]

Watch the colors above the altitude tape. Both the mode and the altitude must be magenta (Magenta = FMC controlled. White = MCP. controlled. If the altitude or mode is white, you'll just sail by TOD). As you spool down the MCP alt window, the window's setting will appear in white above the magenta mode and alt. It will flash just before you nose over into the descent.Save a flight 10 miles before TOD and play with stuff. There are numerous ways undo a perfectly good, FMC'd TOD, but always a way to get back. There's a lot going on there.

Thanks for the advice. I think I am doing all the right things and watching all the right annunciations. When it flashes, I know it is going to descend on cue.Maybe just to be doubly sure, it is prudent to hit Profile once more.Meekal

[Jeffrey L. Whitaker 0]

Meekal,Hitting the PROF button at TOD certainly won't hurt anything. Still, there is no need. Provided you have setup the systems correctly the autoflight system will manage your descent. I realize that seemingly simple tasks like setting the MCP altitude might come across a bit elementary. However, in the absence of a software bug or anomaly, the failure of this sircraft to begin descent at TOD must be the result of incorrect programing. Another common problem is the failure to input your correct cruise altitude in the FMC. For instance, if you program the FMC for a cruise altitude of FL360 but set the altitude window at FL340, you will experience problems with the system management of your vertical flight plan. JW

[Guest meekal]

Meekal,Hitting the PROF button at TOD certainly won't hurt anything. Still, there is no need. Provided you have setup the systems correctly the autoflight system will manage your descent. I realize that seemingly simple tasks like setting the MCP altitude might come across a bit elementary. However, in the absence of a software bug or anomaly, the failure of this sircraft to begin descent at TOD must be the result of incorrect programing. Another common problem is the failure to input your correct cruise altitude in the FMC. For instance, if you program the FMC for a cruise altitude of FL360 but set the altitude window at FL340, you will experience problems with the system management of your vertical flight plan. JW

JW, Apreciate the important points you have made. I do everything according to procedures. Never have my cruise FL contradict the FMC, as you suspect, or make other "programming" errors. It may be a bug but it an intermittent once since it does not happen everytime.On a slightly separate issue, today I had both the FMS speed and the Nav drop off, for no reason and she started turning away from the track. I re-engaged them. Then the FMC speed would not re-engage so I manipulated the speed manually.None of these anamolies are catastrophic. I was curious if others were experiencing the same thing. The moral I derive from all this is to be even more attentive to what is going on. Even in real life, too much blind faith in the automatics, sitting there fat, dumb and happy, has caused many a problem, some with unfortunate results. Meekal

Meekal,Hitting the PROF button at TOD certainly won't hurt anything. Still, there is no need. Provided you have setup the systems correctly the autoflight system will manage your descent. I realize that seemingly simple tasks like setting the MCP altitude might come across a bit elementary. However, in the absence of a software bug or anomaly, the failure of this sircraft to begin descent at TOD must be the result of incorrect programing. Another common problem is the failure to input your correct cruise altitude in the FMC. For instance, if you program the FMC for a cruise altitude of FL360 but set the altitude window at FL340, you will experience problems with the system management of your vertical flight plan. JW

JW, Apreciate the important points you have made. I do everything according to procedures. Never have my cruise FL contradict the FMC, as you suspect, or make other "programming" errors. It may be a bug but it an intermittent once since it does not happen everytime.On a slightly separate issue, today I had both the FMS speed and the Nav drop off, for no reason and she started turning away from the track. I re-engaged them. Then the FMC speed would not re-engage so I manipulated the speed manually.None of these anamolies are catastrophic. I was curious if others were experiencing the same thing. The moral I derive from all this is to be even more attentive to what is going on. Even in real life, too much blind faith in the automatics, sitting there fat, dumb and happy, has caused many a problem, some with unfortunate results. Meekal