What Happened?

[kencnnrs 8]

While in my flight this evening, I had to be away from my computer near TOD, so I just set a lower altitude on MCP like I usually do and let VNAV take care of the descent for the few minutes I would be away. I have had to do this before and aircraft descended on its own with no issue and I'm sure I set everything properly as I always have... made sure VNAV was engaged, lower altitude set on MCP, flight directors and autothrottle on. Anybody know why the plane did'nt start descent at TOD? Should add that I was about 30nm away from TOD when I set lower altitude. I'm thinking I must have been too far back, but i'm not sure.

[IFR7700 228]

Have you been able to replicate this?

[NoahBryant 26]

I do this all the time and never experienced that problem. During some testing I did, I would set the lower altitude literally right after ToC and it worked fine.

[gman1986 14]

Just to be sure maybe you should turn on the pause at the top of descent option then when you come back you can start right at the beginning of the fun part.

[kencnnrs 8]

Haven't tried to recreate this yet, will this evening though and post back. I've also had the issue where it descended on its own, but stopped at like 25,700 and started to overspeed when I had MCP set to 4400 and no altitude restrictions. Also a time when I was not watching. I guess I have to eliminate the common denominator here and sit in and enjoy my aircraft like it was intended.More of a brunette man my self, Jason, but I would'nt kick a blonde out of bed for eating cookies.

[DaveCT2003 1,820]

I had this occur when I was in front of the computer, it just didn't descend. So I descended manually, but I couldn't select the SPEED button, so I had to switch the A/T off and control speed manually. I cycled the A/T, but still could not use MCP Speed. Then cycled the A/P, then the F/Ds Not sure where in the mix I regained MCP Speed control, but I did, and flew via the MCP after that. This happened twice after Hot Fix 4, but a restart of the computer cured it. It happened again, but another restart and it was gone again. Then I checked the FMC\Aircraft Failures, and maintenance failures were switched on (I had them off, but forgot that I'd reinstalled the Hot Fix and never switched them back off). I cleared the failures, and it's never happened again. Lesson learned... Dave writes long, meaningless posts (lol), or always check the failures when you're having some unexplainable problem with the aircraft (If that only worked in real life). Be well, and happy flying!

[kencnnrs 8]

Good call Dave, will have to double check that.

[DaveCT2003 1,820]

Not sure if that's the problem you're having, but I can tell you that I so embarrassed at myself that I think I actually blushed when I saw the failures.... I can be the dumbest person I know, and completely unaware of it most of the time!

[kencnnrs 8]

We can all be like that at times. Thats why I never present my issues as a PMDG issue. I always first assume I'm doing something wrong and go from there.

[DaveCT2003 1,820]

Roger that Ken! Birds of a feather, so to speak.