FMC and AP questions

[Orlaam 306]

How can I enter a speed and altitude constraint? For example, I just flew from KPHX to KABQ. The RW (3) at KABQ is about 5300 feet. I tried enroute to enter slower speeds and altitudes into the FMC's RTE page, but it said INVALID ENTRY. For autoland it probably would've been fine I guess, but I disengage about 10 miles for a visual hand fly. Also, during this flight I tried to let A/T slow the plane down by selecting speed on the MCP and lowering to 180. It didn't slow down, so I had to just disengage A/T. By the way, it was still in LNAV descending. Obviously this won't work like this? How does the real world do it without compromising it's descent?Chris

[Guest ba747heavy]

>How can I enter a speed and altitude constraint? On the LEGS Page, enter SPD/ALT and then LSK on the right side to the waypoint you want to have that constraint. If you only want a speed constraint, enter SPD/, conversly for an alt constraint you enter /ALT>Also, during this flight I tried to let A/T slow the plane>down by selecting speed on the MCP and lowering to 180. It>didn't slow down, so I had to just disengage A/T. By the way,>it was still in LNAV descending. Obviously this won't work>like this? How does the real world do it without compromising>it's descent?That sounds correct. If you are on a descent path with any ALT constraints in it, the FMC will switch to VNAV PATH descent, and the active A/T mode will go to 'ARM', which means you are in control of the throttle. The FMC, and as a result the autopilot, are only interested in keeping on the VNAV profile when descending on a VNAV PTH descent.However, with a descent path with no ALT constraints, the FMC descends with regards to speeds.

[crvm 0]

You do not input MODifications of the active route from the RTE page, you need to do that on the LEGS page. LNAV does not control PITCH MODE (VNAV, V/S, LVL CH and CWS P), it is a ROLL MODE just like HDG SEL or CWS R. So what mode were you descending in? Anyway, If you are coming in with excess energy (FAST) you will need to use the SPEEDBRAKES and if you really need to slow more the GEAR (Within the proper operation range of course). I think you might have been high on the path but you did not give any details so hard to tell. Best to get established on a 3 degree path to the runway, use the deviation bar on the ND to look at where you are on the path (One way). This is somewhat complex and needs time to fully understand how to make the bird do what you want it to do and knowing it's limitations etc. MCP SPD works great, take a screenshot next time, it speaks loads of information ;)[h4]Best Wishes,Randy J. Smithhttp://www.precisionmanuals.com/images/betaimg.jpg

[Orlaam 306]

I'll try and explain. As far as the constraint page, I was on the LEGS page, I mistyped. It said 240/5355, and I typed 130/5355, but it wouldn't take the changes when I pressed LSK 6 on the right next to the waypoint. I've done it before on other FMCs.As far as the SPD thing. I was in LNAV-VNAV and letting the plane descend into it's approach. The PFD said ARM | LNAV | VNAV PTH I'm not positive about the last indicator, whatever it defaults to in descent. When I got a few miles out I was going about 240 KIAS and wanted to slow it down by selecting SPEED and turning it down to 180 KIAS. The FD and A/T are still on, as is CMD A. When I selected SPEED it lit up, however turning the dial didn't even effect the engines. I thought the light that extinguished when I pushed SPEED was the VNAV (one on the left side). I decided to just disconnect the A/T and drop the throttle manually, so I could select my flaps and start my final. One other thing, I forgot to arm the speedbrake (new CH yoke and pedals had me sidetracked). I did do everything else right though (Autobrake, Gear, Flaps 30, Vref, No AP for manual landing, ect...).Not arming the speedbrake resulting in the speedbrake deploying anyhow and lighting up the armed indicator. That's how I knew I forgot and looked from spot view.All this is in 2002. I'll try and get some screens tomorrow if need be. Love the new plane though!Going to bed, thanks for the help. Back tomorrow!!!Chris

[744pilot 0]

As already sad before.You need to enter the SPD/ALT constraint by SPD/If you enter the hole format. (180/5355 or something)its not necesary.Just enter the SPD with /Thats all.Let me know how it works.Ramon.

[Orlaam 306]

I tried this as well. It wouldn't just take the speed with 180/I will try some other things, but it didn't work on 2 flights during CRZ.Chris