B747-4 deciding flap selections

[Guest Barny]

Hi Guys can i clarify a few things i'm getting a little confused when i should be initiating my flap selections. when starting my descent i normally reduce to 290Kts and Flap 1+10then around 20nm DME reduce speed and select F10+10about 16DME again reducing to Flaps 20+10 gear down then on GS captureFlaps 30 VREF+5 plus a windspeed component e.g 10KtsI'm finding my timing or indeed the whole procedure for flaps im using may be flawed as i appear to pitch up for quite a while untilLOC/GS capture then final approach im now flying VHHH to EDDF IAF MTR im at CRZ ALT 340 IAS/Mach 344 i presume on my FMC prompt 'RESET MCP ALT' i can descend to FL100 resuce further to 250Kts below this FL then arrive at my Hold at 4000reducing to 220Kts Flap 1 if this is correct then how am i guided toslow further using flaps? to enter my FAF IAF i know my final VREF is selected from my FMC Init Ref Approach section.Please could anyone give me an insight into how YOU would make these choices and at what stage of the desecent, approach an landing. Many Thanks i'm probably doing this completely pear-shaped so any advice would be greatly appreciated ! Many Thanks Barny

[rsrandazzo 6,353]

Barney-You are giving this ol' girl WAY too much room to slow down! If you tried this in the real world- ATC would be asking you to "call on the landline" after you park. :-)If you go into the AOM that we have provided, you'll find quite a bit of information on how the approach profiles are flown, with what flap settings at what phases of flight. For example, you can see the "coupled ILS" on page 10-14.(Find your AOM by going to START/PROGRAMS/PMDG SIMULATIONS)Now- in the real world- you don't operate flaps based on distance. You operate them based upon need. Some theory to help you out:Flaps are useful in that they increase the lift capability of the wing at lower AoA, while simultaneously increasing drag in order to allow the airplane to descend a normal glidepath with the engines at a high enough RPM that immediate G/A thrust is available if it is needed.Now some practical tips:Your goal is to hit the be on speed FLAPS 20 about 2 miles before you'd expect to intercept the G/S. When you see the G/S start moving down toward you, and it is about 1.5 dots above- throw out the gear.When you have all of them down and locked, select your landing flap setting. (Don't increment to FLAPS 25 then FLAPS 30. Go IMMEDIATELY to the setting you will use to land.)At this point you should find yourself on speed, on G/S.Planning ahead:When you start slowing the airplane depends more in how fast you are going and what the approach looks like prior to glideslope intercept. If you have a long winding descending approach, get slowed early because the airplane doesn't like to Go Down and Slow Down at the same time. You get one or the other. The technique to use when slowing while on autothrottle is pretty simple: Select flaps, set speed. (say it three times!)In other words: When you want to begin slowing- get yourself down to a speed slightly above the green "up." Select FLAPS 1 and then set the speed bug on top of the "-1" marker. Not +5, not +10. Set it right on top of it.When you are ready to slow further, "Select Flaps, Set Speed" Select flaps 5 and set the bug directly on top of the "-5"Do this again for Flaps 10 and 20.A "perfect" method will have you going from flaps 5 to flaps 20 pretty quickly- as the airplane is not very efficient with all that drag out- so you don't want it until you NEED it.Flaps 1 is there to help you start slowing without getting too close to the stall buffet for that nice clean wing. Flaps 5 adds a bit of drag to help you slow.Flaps 10 and 20 are very draggy- but they do help with the lift. Flaps 25/30 are all about drag so you can go downhill with the gear down and the engines spooled up.Something to notice:Next time you fly an ILS, take a look at your power setting when you are fully configured for landing. It should be around 65-68% depending upon weight.Next time you fly an ILS- put yourself on a long localizer final approach, disconnect the A/T and set that power. Watch the speed decay- and add flaps as needed in order to keep in compliance with the flap bugs on the airspeed indicator.Notice how smoothly that works? You can set a single power setting- and forget it all the way to touchdown. That is what is known as "drag configuration." You are adding drag to help the airplane slow.Your GOAL: Set that power setting at the right moment so that you naturally reaach flaps 20 JUST as the G/S is starting to move. Then you select gear down and landing flaps as you start down the glideslope... and you never have to touch the power setting from the moment you started slowing until you are in the flare.now THAT is when you have the old girl mastered. ;-)Good luck!

[Headley 26]

Hello Robert,Thank you for this very informative explanation. Never tried it this way.Now this is why we are all eagerly waiting for the upcoming type rating lesson 5 :-hah Even the AoA training DVD is not so detailed!

[basa 0]

>>The technique to use when slowing while on autothrottle is>pretty simple: Select flaps, set speed. (say it three>times!)>Thanks a lot for this magisterial lesson captain !I've been doing it the wrong way (first the speed, then the flap) all the time. But I've found that if you place the speed bug just on top of the flap green mark, the aircraft tends to be somewhat over pitched, so I normally add 5 kts.

[Guest jbos]

FWIW, the docs (chapter 9: Flight technique) currently read:When selecting speeds independently ofATC instructions, selecting an MCP speedwhich is 10 knots higher than the flapmaneuvering speed bug will provide astable, efficient flight envelope with acomfortable margin for banking turns whichmay be required by ATC.Flaps Usage: To ensure a normal,stabilized approach, it is good technique tohave Flaps 5 selected by the time the initialapproach is commenced.Proper deployment technique is to set thenext flap setting as the airspeed passesthrough the next highest flap settingmaneuver speed. For example, selectingflaps 20 will be done as airspeed slowsthrough the flaps 10 maneuver speed. - Jason

[Guest Barny]

Execellent Robert thank you for such a thoughtful detailed yet user friendly explanation, my aproaches to date have been a bit of lesson in gliding, now that i can see correct pattern to adopt to get me nicely configured at speed on time for the final G/S approach my arrivals will have much greater realism and certainty i hope Could i ask one final thing, how soon before start of descent wouldyou begin slowing, say if i was going along a 340Kts would i wind speed down to say around 290Kts or, as you have said just take the speed down to just above the 'UP' Green marker, then as i get the (RESET MCP ALT) annunciation and descent at TOD at the speed just above the 'UP' indicator at Flaps 1 to commence the descentAlso, Robert when approaching your FAF what flap setting are you ideally wanting to be at? as i notice the AoA DVD really gives distance as the indicator rather than speed for flap selections. Thank So Much For The Great Support !! Barny