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Fuel management and landing minimums - couple of questsions?

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Hi there allI have a few niggling questions regarding PMDG 747 I have acquired over the last few months. I was hoping some of you out there might have the knowledge to help me a little with them?1) On a long flight, e.g. WSSS/EGLL, the centre fuel pumps "ask" to be turned off when centre tank quantity is at 0.9 tonnes. The remaining fuel is then fed into the Main Tank 2 - which obviously makes its quantity 0.9 tonnes heavier. When it comes for Tank to Engine configuration, i often get an >XFEED CONFIG caution. This can be corrected easily enough - I was just wondering if this happens on the real 744, and if it does, do 744 pilots worry much about a 0.9 tonne difference/the >XFEED CONFIG warning?2) After a beautiful explanation a few months ago by Mr Kappert regarding landing minimums - I have a couple of further questions:- If I am cleared/flying an ILS CAT II approach for Heathrow's runway 27L with Autoland 3, am I allowed to disconnect the autopilot and fly the approach by hand using the ILS minima (decision height 60ft, MDA 140ft). Or must I use the MDA or some other minima? - To use the example of Captain Alan Carter in the VS 744 DVD, he is cleared for a visual approach for RWY 28L, decision height 200ft, MDA 210ft. Most of the approach is flown using APP mode and all three autopilots. Shortly before disconnect the autopilots, he calls "Man. land, 210". Does this mean he is to use the minimum descent altitude of 210ft if hand-flying the approach?- Is Mr. Carter allowed to let he autopilot fly the whole visual approach using ILS - and if he did - would he use the ILS DH of 200ft?Thanks for any light anyone can shed on these questions. Sorry about the long questions!Thanks again for any helpRudy

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Rudy;With Cat II/IIIa, IIIb and IIIc approaches both the airplane and aircrew require recurrent training and certification (not sure hou much you can train a 747, )Every 90 days for Cat II (30 for Cat III) you must perform a full autoland, I am unsure if this is an airline specific or regulator specific requirement - I BELIEVE it is a regulator requirement.Aircrew are generally trained on a rotating cycle with various recurrent sim and ground school every 6 and 12 months.MDA or minimum descent altitude is a term used for non precision approaches, its the altitude at which you must make a decision to go around or continue; the FAR says you can only continue if you can sufficently sight the runway environment but the airlines may and often do add some other restrictions in there.DH or decision height is exactly the same however it is a point on the glideslope, lets say its 200ft and at 0.8 DME, at 0.8 DME you should be at 200ft.As for use of the autopilots I'm not sure, the regulators and airlines both play a role here, maybe Jon, Steve or Rob can tell us.On the VS DVD I notice Alan mentions BOTH DH and MDA which is interesting as my Jeppesen plate for the ILS Rwy 28L at SFO shoes 213ft the DH BUT that is 200ft HAT with the airport elev being 13ft. Maybe someone with some more knowledge can clarify if this is what he meant.No matter if you are doing a coupled or manual landing you'll ALWAYS use the published DH for deciding to go around or continue, provided you descend that far.If you are cleared for and intend to fly the published ILS approach you will use DH.The airline sets specific rules regarding use of the autopilot for its aircraft and one airlines policy will invariably vary from the others, but the FAR defines a visual approach as one made using only visual references; there are a number of chartered visual approaches into San Francisco, which are great fun to fly. Jon should be able to answer this one with regard to VIR specific procedures.Hope this hslps!

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Hi Rudy,from the PMDG manual it states that if you are flying an CATII/III approach down to these approach minima, then an autoland has to be performed. This is due to the height of the cockpit and length of the 747's wheel base which would make it tricky to judge the flare precisely in such conditions as would be present if these category approaches were in use.So CATI you can hand-fly the approach, or disconnect the A/P at anytime and land manually.CATII/III coupled approach/autoland.Regards,Bjorn

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Hi there Ben an Bjorn Thanks so much for your helpful replies - things are now becoming clearer. I really appreciate the time you spent to answer these seemingly odd questions.You bring up an interesting thing relating to Captain Carter and the decision height/MDA. Hoepfully somebody will be able to shed a little light on it. Thanks for the detailed info!Bjorn - that's an interesting point you brought from the manual. I wonder if the manual means you have to autoland with CATII/III approaches when actual visiblity is low, or just whenever you do a CATII/III approach?Thanks again guys for your time and effort. I'll look up one of those visual approaches for SFO next time I fly there, Ben. Should be fun.CheersRudy

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The only reason the 747 (and others) have three autopilots is to add the required redundancy factor for Cat II/III approaches as required by the regulators.Any time you are doing a Cat II or III approach you must use the autopilot as required by the company and regulators; I am aware the FAA mandates redundancy in the autopilot system for a Cat II or III approach but I'm not sure where; I took a glance at the FAR while I'm writing this but I couldn't find anything.Maybe one of our sky drivers can be of some help :)So unless I am mistaken, which I may be: My dispatcher tells me that my 747 needs its 30 day autoland check (which my PMDG one probably does!) so when I get to my destination I'd brief and fly the Cat III approach to the selected runway as published using the applicable DH etc.I'm not sure what would happen if the runway I was assigned did not have at Cat III ILS, I guess you could request one that did but many major airports worldwide don't like you using non conforming runways.So I suppose you could forego the 30 day check and get something like "CATIIIC AUTOLAND CHECK OVERDUE, AIRCRAFT ONLY AUTH CAT II APPCH" or something on your dispatch paperwork until the test is performed.

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I've got Mike ray's book on the B747-400. He states that ALL landings in less than CAT I visibility are required to autoland. This is specific to the B744 (and the B767 for those who are interested) due to the height of the cockpit at the crossing of the threashold. (i.e. the cockpit is so high at threashold crossing, you might be in the goo, even thought the rest of the aircraft isn't!)

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I am new to both variants of the PMDG 747, and I too have noticed the fuel tank thingy. As i am only halfway through the manual, this might seem a little pre-emptive, but does anyone know why it goes to the one tank?Also what should be done to correct this? I either wait for the tank to run out (i think it goes to .2k) then switch it, or I turn the right side pumps off to civilise the unbalance. What should i be doing? is there a way to pump fuel from side to side?I'll keep plodding through the manual with this one, but for now any ideas?Alan M

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Possibly, the explanation for the feed to the #2 tank is because the APU normally uses that tank. If the APU is running after the aircraft has been refuelled (with equal amounts in each tank), the fuel in the #2 tank may be lower than the others. Centre Wing scavenging should help to correct this imbalance.On later series aircraft, there is no electric scavenge pump. The scavenging is done by jet pumps (which have no moving parts). Fuel is scavenged into both the #2 and #3 tanks. All these types of aircraft seem to have the APU fed by both #2 and #3 tanks. This seems to confirm my theory ;)Cheers.Q>

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