Alt Sel Not Holding Altitude

The last couple of flights I've had a problem with selected altitude not holding once achieved. Yesterday (short 'hop' from Yeovilton to Exeter) I entered custom waypoints and preset 4000 in ALT SEL. On climbout, and achieving 4000 (with the audible 1000 to go 'bong') the altitude began to decay. I had moved condition levers to 900 and retarded throttles to maintain 240kts but airspeed started creeping up. Dreadful admission, but that was what alerted me to the slow descent. Any ideas, anyone?

Andrew Gold


  • It would be best to show a video of what you are possibly doing incorrectly

  • Sorry kroswynd, but I don't know how to create/save/show video from FSX. This problem is intermittent, but only in the MJ Dash. I've just done this same flight and it happened again. I'm only using the captain side FMC - not x-filling - but the NAV source is correctly selected. Is that an issue? This time I was at the first flight plan selected/entered altitude (with 'bong') and preparing to climb to the next preset (ALTSEL) altitude when the a/c began to descend. Still have AP and LNAV engaged. It's a mystery to me as my other (most used) model is the PMDG 737 and it has never behaved this way.


  • If no video, then please have a photo showing the situation and the active flight modes in the PFD. I ask for a precaution, but the autopilot was also on?

Sign In or Register to comment.