Fred Clausen v2 Tutorial Question (Related to T/D to KORD)

[Guest SkoalFyfan]

Ok,I've been trying to fly Fred Clausens tutorial now twice from KJFK to KORD. I have no problems navigation with the FMC and operating it. All is fine. My question though is with regards to the T/D and when to begin the descent and how the autopilot does it?The tutorial says to begin the descent when about 30 NM out from the PMP marker. At this point you set your MCP ALT to 5000 and then jump into the FMC and set the PAPPI intercept to be at 200 / 5000. You then hit the DES page on the FMC and begin EXECUTE the descent to begin.We are still at ~39000 ft when we begin out descent 30NM out from PMP.My problem is when I execute this the autopilot descends at such a SLOW RATE. If I were to let the autopilot completely descend itself it will still be at like ~22000 ft when crossing PAPPI. The second time I did this tutorial I could see again I was WAY off the marker as far as descent rate so I manually took the controls and increased my descent rate. There has to be a way to do this smoothly and correctly though? Am I beginning my descent way too late or am I just missing something? Anyone else had this problem?Thanks in advance!Paul

[Tabs 2,790]

Paul,Where is T/D in relation to the point you start your descent? If it's still ahead of you then the plane is entering DES NOW mode. This is designed to do a shallow descent up until the point where the plane intersects the vertical path - you'll then see VNAV PTH and get a normal rate of descent after that. The "right" way to decend at least from the FMC's perspective is to wait until you reach T/D - the plane will descend automatically at that point unless the MCP is inhibiting it.If you get into a situation on descent where the plane isn't doing what you want it to while under control of the automation, by all means go to one of the manual MCP modes like LVL CHG/FLCH or V/S. In real life these modes are used a lot more frequently than a fully automated descent is. ATC almost never clears you to descend exactly as the computer wants to due to traffic flow, weather, etc.

[Guest SkoalFyfan]

Ryan,Yes it goes into DES NOW mode as this is what the tutorial insists on. The tutorial thought talks about setting the FMC to ensure that we cross PAPPI @ 200 / 5000 and seems to imply the FMC will ensure the AP "gets this". Problem is though like I said. The plane remains in the shallow descent you described and I always end up arriving PAPPI @ ~22,000 ft when starting from 39...Nowhere does it seem to mention anything with regards to this...I guess I just need to familiarize myself more with the 737's AP system. You seem to say though if I were to wait it out and do nothing that the plane should descend automatically based on the T/D and arrive at the proper speed and altitude of the waypoints set in the FMC???Thanks!>Paul,>>Where is T/D in relation to the point you start your descent? >If it's still ahead of you then the plane is entering DES NOW>mode. This is designed to do a shallow descent up until the>point where the plane intersects the vertical path - you'll>then see VNAV PTH and get a normal rate of descent after that.> The "right" way to decend at least from the FMC's perspective>is to wait until you reach T/D - the plane will descend>automatically at that point unless the MCP is inhibiting it.>>If you get into a situation on descent where the plane isn't>doing what you want it to while under control of the>automation, by all means go to one of the manual MCP modes>like LVL CHG/FLCH or V/S. In real life these modes are used a>lot more frequently than a fully automated descent is. ATC>almost never clears you to descend exactly as the computer>wants to due to traffic flow, weather, etc.