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[Guest Verran]

*Sighs* It appears I will have to bring all questions and queries to this form as PSS's FMC documentation is inadequate. Shocker. So I purchased this product yesterday and already I'm fed up. But let's try to work the problem, here. It's amazing, even how people I've never met in my life have managed to make me feel in a manner that only the people I work with do. Amazing. Back to the problem.I don't know what the deal is, but I departed RJAA this morning on the Sakura 7 departure for New York, and for some reason the VNAV wanted to keep me down at 640ft and 350+KIAS. So I disengaged it and began a manual climb. Leaving a few thousand, I reengaged it to give it another chance, and then she just stopped at 10000. I ripped through the FMS to find a solution, yet, my cruise altitudes were set for FL370.I'd appreciate ANY support someone can offer...

[Guest Verran]

Restarted flightsim, tried again, and here she sits, on V22 direct IXE (She didn't even fly the SID correctly), and for some reason the CDU Climb pages keeps bouncing between 280 and 250. And she's still sitting here at 10,000 twiddling her thumbs. Why is this so agitating? I'm a real, licensed, aviator. Shocker.

[Guest Verran]

I tried the RKSI thing. She still leveled off at 10. That was on the second try. First time she broke through the fog then figured the visibility was just too much for her I guess, and I found myself in the Pacific.

[Guest Verran]

Third time was not the charm. I rotated, engaged the autopilot master, LNAV, VNAV, and A/T, and she decided to stall herself this time.

[Guest Verran]

I must REALLY be bored, because I just fired up the jet and elected, for some reason, to give it another chance. Okay, fine. Now I don't know what the problem is, but I decided to test a theory. Every time I've flown, the altitude window in the autopilot panel has displayed 10,000. I set it to 8,000 this time, departed, and she leveled off at 8, WITH VNAV engaged! In no way shape or form was the autopilot told to maintain 8,000. What is going on here? Why wont the damned jet just do what I tell her to do!?

[Guest Verran]

*Sighs* So I set 37000 in the altitude window, pressed HOLD, then VNAV again, and apparently the system reset and she started climbing. Yay. Except, now, leaving FL280, she's gone nuts... again. I don't know if she forgot the definition of a fine touch or what, but the horizontal stabilizers aren't moving very subtly at all now. In fact they're going back and forth a couple degrees every second.EDIT: Okay. She just blew right past optimum altitude, and the 2000ft+ mark. Looks like she's making a beeline for 370. Alright guys I'm proud of you. So far she's done nothing your documentation in all it's infinite wisdom says she's supposed to be doing. Good work!Thanks for a wonderful airplane, guys, I can't trust her to do anything herself... V_V

[Guest Phoenix5]

Verran, (Is that your name I can't tell since you have not signed you posts as per the forum guidelines)From what I can read the problem is user error. If you have 10000 feet in the MCP window then it will level out at 10000, or 8000 if you change to that. Therefore if you dial in 37,000 feet the plane will climb to FL370. Copied from the manual: "...22. Altitude window. Displays selected altitude. When reaching this altitude in any pitch mode, the plane will level off. FLCH mode will start climb or descent towards this altitude when engaged..." In my infinite wisdom the plane is doing everything you ask of it, maybe you should try the tutorial flight...

[Guest Verran]

I'll get cracking on that signature... V_VRegardless of what's dialed in the MCP, neighter HOLD nor FLCH were engaged. Why then would the aircraft not fly according to altitudes prescribed in the VNAV pages? And I have seen no tutorial flight.Edit: To give you the benefit of the doubt I just checked my hard drive. No tutorial flight installed on my drive. Something you want to share, sir?

[SierraDelta 1,337]

>I'll get cracking on that signature... V_V>>Regardless of what's dialed in the MCP, neighter HOLD nor FLCH>were engaged. Why then would the aircraft not fly according>to altitudes prescribed in the VNAV pages? And I have seen no>tutorial flight.... no, but did you read the manual?Briefly - regardless of what vertical mode you're in, be it HOLD, FLCH, V/S, VNAV, the MCP value is king - period. As a "real, licensed, aviator" you should know.....Cheers,S

[Guest Verran]

*Rubs eyes and pinches the bridge of my nose* Okay so I f*ed up and I was an ####. Sorry... But... I'm reading through this and I still need someone to spell it out for me. How does this whole VNAV thing work? I get that it maintains the most economical cruise and climb, yet, how does this step climbing work? From what I'm understanding I have to monitor the system and manually direct the climb? That can't be right... or is it? Yeh I need someone to spell this out for me. I'm not smart enough right now.Thanks for the tutorial flight, SD

[Guest AlexMcB]

Hi Justin,Apologies if this is "teaching my Gran to suck eggs". But just to offer a little clarity on generic Boeing MCP and VNAV modes.The FMC builds the VNAV climb profile based on data that you have entered on the VNAV CLB page and of course the LEGS pages, the SID may have climb restraints at various points heading away from the Terminal area. Once you've "cleaned" up the aircraft, the target airspeed generally becomes 250 knots or lower if restricted by a SID speed constraint on the LEGS page. Of course, it's great to hear "No ATC Speed Restrictions" and these speed constraints can be deleted from the Legs (if in a SID e.g. 240/6000) and/or the VNAV Climb page (you may want to delete the generic 250/10000 restriction). Passing 10,000 feet, the target airspeed becomes either the climb speed set by the FMC or a manually selected climb speed if you've used the MCP. In respect of altitude; the VNAV climb segment lasts until reaching the FMC programmed cruise altitude (this should be the flight level that you are planning to fly at and can of course be changed if req'd). However, and this is where the MCP (Autopilot panel) on the glareshield comes into play and can be thought of as a safety catch to the FMC. Intermediate level-offs during climb will occur in two ways; reaching a LEGS waypoint altitude constraint (from a SID or even a specific ATC instruction that you've entered for conflicting or crossing traffic ahead), or reaching a MCP ALT set lower than the FMC cruise altitude.When a LEGS waypoint altitude constraint is encountered, the VNAV PTH mode is engaged for the level off. The aircraft remains level until the constraint is cancelled when you pass the constrained waypoint. The climb then continues towards the FMC cruise altitude (or next constraint whether in a SID or via the MCP). When encountering an MCP ALT set lower than the FMC cruise altitude, the ALT HOLD mode is engaged and speed control is transferred back to the MCP. To continue the climb in VNAV, the MCP ALT must be reset to a higher altitude and VNAV must be re-engaged by pressing the VNAV MCP button. On the flight deck this re-engagement is agreed between both pilots; the new altitude will be dialled into the MCP and verified "Set, Seen and Armed" prior to VNAV being pressed. In this way, the aircraft climbs to authorised levels with the full agreement of the crew.So in effect although trying to achieve CRUISE, the MCP set altitude acts as a "check" on the climb and therefore allows the aircraft to climb as directed by ATC in stages. Certainly looking at a trans-Atlantic departure from Heathrow, a flight can be a fair way up the U.K. heading say towards Glasgow and then Stornoway before reaching its intial cruise altitude due to congestion and conflicting traffic - it would be very unusual to have a non-stop climb to Cruise Altitude. Experienced it a few times though, once on departure from Nassau to London, straight up to Cruise which given the proximity of Florida traffic was a pleasant surprise. When the aircraft levels off at the FMC cruise altitude, the VNAV PTH mode is engaged and control over VNAV operations automatically switches to the Cruise page. When the FMC cruise altitude matches the MCP ALT, VNAV PTH mode takes priority. This is the reason that ALT HOLD mode does not engage in this situation. A change to cruise level in the FMC, or a step climb must be reflected in the MCP - the safety catch! It is a similar process in the descent; in theory the ideal descent path would be a low drag constant descent from FL400 to ILS capture at say 3500. In this example, the MCP Altitude would be reset to 3500 prior to the TOD and the aircraft would automatically descend at the correct time. In reality however, there will be waypoint (STAR) restraints, obstacle (MSA) clearance, ATC congestion and the need for separation and spacing.The initial VNAV descent is calculated from the TOD to the first waypoint altitude constraint on the LEGS page. This is calculated for IDLE thrust using the airspeed set in the VNAV DES page. Later descents are calculated as straight descents between LEGS page constraints at the selected speed and required thrust in VNAV PTH mode. To allow the aircraft to begin an automatic descent at TOD, the MCP ALT must be at a lower altitude. If the aircraft reaches the TOD and the altitude has not been reset, the aircraft enters ALT HOLD mode. To restore VNAV control over the descent, a lower altitude must be dialled-in and the VNAV button pressed. The descent airspeed set by the FMC is the economy airspeed based on the cost index entered on the PERF INIT page. The descent airspeed can be changed by manually entering a new airspeed on the descent page. The descent speed and altitude can also be changed by manually setting waypoint constraints on the LEGS page, e.g. Speedbird 279...230 knots and 10000 by Point Reyes. This will cause the descent profile to be recalculated.As S

[Guest Verran]

Oh wow... Hey thanks Alex. I'll put this new information to work in the morn. Looks like I owe a few people some apologies. *Chuckles*

[Guest AlexMcB]

You're very welcome...AlexEGCC / EGPH

[Guest Verran]

I do have one remaining question however. I'm about to go put that information you gave me to work, but one part of it rang familiar. Before when I set the MCP altitude to 370, with VNAV engaged she blew right past her optimum altitude. I think the ECON CRZ said the optimum was something down around the 290's and max was 310. Um. Confusion kicks in.And the sincerest of apologies to the PSS team. ... But the engines still need to be bigger. XD

[MarkRey 16]

Justin,VNAV has a lower IQ than you seem to think :) - the fmc computed opt, max alts are guides to you the pilot.YOU have to dial in that given 'opt' value and climb to it. If you dial in 370 when opt is 310 and you're in a climb, she WILL blow past 310 and try to obey your 370regards,MarkXPHomeSP2/FS9.1/3.2HT/1024mb/X700pro256