more 747 autoland questions

[pkofman 4]

New Questions on thie same thread,Some other questionsOne the way down i usually place the alt value lower ( 0 ) than the calculated alt in the fms BEFORE the TOD circle . In this way the plane follows the vnav for alt-fix values, Does anyone else do this?Any other methods to ensure the plane follows the vnav path on the way down to the intial approach fix.. Sometimes when atc give you a restriction you need to go to the fms and insert the alt and lsk it, The fms will recalc.the v-path, would you then hit vnav or use the flc and enter the fmc , What is everyones preference.also, another little glitch. Several times, on autoland I am lined up and I push Loc then App,, but the A/P trips and goes off,, that has me baffled ,,Seems to come out of nowhere.??ThoughtsPetercf-mzz ACA-10

[cowpatz 243]

I am not sure I fully understand your question so please forgive me if I do not provide you with the solution you seek.The normal way of conducting a descent in VNAV is to place the altitude selector on the MCP down to your cleared level/altitude prior to or at TOD. If you do not set it lower the aircraft will stay at cruise altitude with VNAV ALT indicated as the pitch mode. To get down from here you need to wind down the MCP altitude and press the same button. There are several ways to descend this aircraft. If VNAV is working then use that and enter any spped alt restrictions/ requirements as appropriate. Just remember each time you do that the descent path is recalculated and you may need to intervene to ensure that the aircraft gets back on VNAV path. If you are getting a lot of hdgs and speed control given to you by ATC then you may find FLCH a better mode. All you have to do here is set the alt and the speed on the MCP and it will do it. You can fine tune it with thrust when HOLD is annunciated if it is descending too quickly and going below profile.My personal preference is to start off in VNAV and then as I get closer in, and consequently get more headings and speed control, I use FLCH. When I am manoeuvering to line up on the LOC and GS I use VERT SPD as I can fine tune the ROD more finely.As for the AP problem on your autoland I will need more information to assist in determining why you are experiencing the disconnect issue. CheersSteve

[pkofman 4]

thanksI tried setting my mcp alt to 0 on the last flight and the vnav worked like a charm, I line up at the intial approach fix and dialed in the loc. freqno problem it autolanded but I had to amend the alt restriction twice on the way in, it all worked out but i think you are correct in that sometimes it is tough to call the exact technique while being vectored all over the place by atc..thanksI have not had the a/p disconnect happen again. however tonight the lnav would not light up or engage and so i had to go to pmdg menu andpush the reset failure button. no idea how that happened.??thanks peter

[cowpatz 243]

As a rule you should never set the MCP alt to 0 ft. Have a look at your charts and select the next approriate altitude and set that (if you are not using ATC clearances). You should always be thinking of terrain and using the MCP alt as your safety net. Below 10,000ft restrict your use of the FMC. You should be looking outside for traffic. There are other AP modes to use that do not require a head down position. When you are on the GS the MCP altitude will not be captured (or else an autoland might prove difficult). Set this to the Missed approach altitude so that in the event of a GA you have an altitude already there.Happy flying.Cheers Steve

[pkofman 4]

>As a rule you should never set the MCP alt to 0 ft. Have a>look at your charts and select the next approriate altitude>and set that (if you are not using ATC clearances). You should>always be thinking of terrain and using the MCP alt as your>safety net. Below 10,000ft restrict your use of the FMC. You>should be looking outside for traffic. There are other AP>modes to use that do not require a head down position. When>you are on the GS the MCP altitude will not be captured (or>else an autoland might prove difficult). Set this to the>Missed approach altitude so that in the event of a GA you have>an altitude already there.>Happy flying.>Cheers Stevethanks and i agree, but are you saying that if you set the mcp lat to "0" then it wont be captured by the gs. It actually did capture it on approach last night, perfectly, but I agree that more prudent is to insert the missed appraoch alt to keep it safe and ready in the event of trouble.Further I suppose you are recommending an alt lower then the fms alt at the next give fix. thanksPeter

[markadeane 272]

Hi Peter,You will have picked up on this from Steve already, but just in case:Once you have established yourself on the localiser you should find yourself level at 2,500 feet or so with 2,500 in the MCP window, you should be about 10 miles out on approach, give or take a bit. The glideslope indicator should show you as being below the GS.If you now arm the APP mode, you will see GS annunciate in white at the top of your PFD, it is now armed. As you intercept the glideslope (ie the GS indicator starts to move down the scale to the middle) that mode will become active, and the nose will lower to follow the glideslope. At that point, you can set the Missed App Alt in the MCP alt window and it won't affect the aircraft's flight path, as the aircraft is paying attnetion to the ILS for vertical guidance, not the ALT hold function. This also serves as a useful reminder to the crew of what altitude they have to climb to in the event of a go around or missed approach.Setting the MCP alt to 0 simply gives you more to worry about if you have to execute a go around.For those that haven't explored the handling of the 747 in a go around, I'd HIGHLY recommend it, you learn a lot about your machine by taking it 'off-road' at times. :-)

[crvm 0]

No, you can do what you are doing but in RL but this would not be what you set it too. I believe the 0 setting can be used for some type of VNAV override to the ground but not to sure about the whys and what ifs. As Steve stated, you only set to what you are cleared to and even after this you will be placing the missed approach altitude in case of a go-around - not 0. But again, it is logically possible in the sim.. Best,Randy J. Smith

[pkofman 4]

thanks for all of the advice guys, we shall see how thing progress and report back..regards Peter

[Qavion 19]

"Once you have established yourself on the localiser you should find yourself level at 2,500 feet or so with 2,500 in the MCP window,"Only if your airport is at sea level ;)Cheers.Q>