Hi All, Sorry if this has been discussed, if so maybe you can link me to the topic. In the PMDG 737 products and Level-D 767, on the MCP is a button for FL CHG. What and how is this used? I have used the ALT dial for changing altitude before in conjunction with the VNAV button or used V/S to control altitude and rate, so I am curious when the FL CHG button should be used. I also noticed on some MCP's a CWS button, when is this typically used? I have been successfully flying the PMDG for awhile without using these buttons, hence my curiosity...Thanks for any guidance!SteveDell P4 2.51 Gig RAMnvidia 2600PMDG 737'sPMDG Beech 1900Level-D 767Ultimate Traffic

FL CH This mode (Flight Level Change) is purely an Autopilot mode. It has no input from the FMC and is based on an internal computation by the Autopilot Flight Control Computer. It's computation is based solely on the actual altitude of the aircraft compared with the altitude set in the altitude window of the Mode Control Panel. If those altitudes are the same, FL CH will not engage. If, however, they are different, the difference is assessed and a rate of climb or descent is commanded to correct the discrepancy in a time period of two minutes. For example, if the aircraft is at 6,000' and the MCP is set to 12,000' the difference is 6,000' and to correct that discrepancy in two minutes, a rate of climb of 3,000' fpm would be commanded. In actual fact, the control law for this is VERY COARSE and, therefore, it is very rare for this to actually happen - it would, of course, be quite impossible for the aircraft to attain the rate of climb required to go from (for instance) 6,000

Oustanding Johan.I asked the same question a while ago, and didn't get a reply like that!I didn't start the thread, but appreciated your response anyway.CheersTim

Thanks Johan! Your explaination is very informative and just what I was looking for. I appreciate your time in explaining it.Steve