Hello all,I have been playing with the FMC to get better at it and have noticed something that looks strange to me. I know it will end up being something simple, but....When I have a full fuel load of 161,671 lbs of fuel the approach flap speeds are 20-176 25-168 30-175. With a fuel load of 16,000 lbs the speeds are 20-139 25-134 30-130. The question is: why with a full load is flaps 25 at a lower speed than the other two?Are you all rolling on the floor laughing at me yet :)thanksSinbad

I think Flaps 25 gives better speed protection / goaround performance when carrying out an overweight landing. Not 100% certain.

Minimum manouevre speeds for each flap setting provide for 1.3g to onset of buffet, this allows for 40 degrees bank. Minimum speeds are all based on Vref30 plus an increment. Vref30 itself is just the speed at which you have your 1.3g at flaps 30. At all lowish weights the system works fine, however at high weights the speed needed to maintain the 1.3g margin increases at a greater rate at low flap setting (F0, F1) than it does at high flap settings (F25, F30). This means that Vref30+80 no longer provides 1.3g at Flaps Up. So overcome this they just 'fudge' the Vref30 figure, by making it artificially higher at higher weights. The result of this is that Vref30 becomes higher than Vref25. In practice this never matters, as at weights where Vref30 is greater than Vref25 you can never get slow enough to actually extend flaps 30, so any landing must be made with flaps 25 and Vref25, providing for the slowest possible landing speed. From memory the speed at which Vref30 becomes greater than Vref25 is 160000kg, which is some 15000kg above max landing weight.(Its late... I hope that wasnt too confusing)

Excellent Post HPSOV.How's the 744 conversion going?

Thanks for the detailed reasoning. I am still chewing on it though.:)Sinbad

Going well thanks!About halfway through the sims now, so 5 more to go including the check, then the line training. I do miss the 767, the 744 really is a step forward in automation. On the whole its very similar to the 767, but everything works a lot better and doesn't require as much mental effort!

Simple explanation...At high weights Vref30 is artificially increased so that the +20, +40, +60 and +80 speeds are fast enough. From a pilots point of view it makes no difference to the way in which you operate the aircraft, unless you are performing an overwight landing in an emergency, in which case you will use Vref25 and flaps25 for landing if that provides the lowest landing speed.

Glad to hear everything is going well.I bet you are already looking forward to all those Trips your going to get. LA, London, Frankfurt, Paris etc. ;)

Thank you, my jaws are hurting so I'll take the last reply and go with it. Thanks for the help.Sinbad

Sorry to butt in here. I

Haha, enjoy the 744! Let me tell you, the 737NG really is a major step BACK in automation from the 757/767. It's unbelievable what ancient 1960's technology is in that 'brand new' airplane! :)Iz

I haven't managed to install PS1 on my system yet, but have seen it often enough at friends houses. As a trainer it really does take the cake, where PIC is about 95% I think PS1 hits about 99%. Obviously doesn't have the visuals etc that PIC does (which I think adds to the fun value a lot), but makes up for it by being spot on in terms of systems and procedures.I always used to use PIC before each cyclic simulator, and I'll be sure to do the same with PS1 on the 744!

When you get arond to install it, make sure to check in to the forum at Aerowinx. There are a number of programmers there that are doing some great things including the possibility to "slave" MSFS to PS1. I.e. we use MSFS as a visual generator so to speak. Taking this combination online is a breeze. Well, a small amount of effort is needed initially but no more than going online with MSFS. One of the latest "breakthroughs" was a small traffic injector that now injects online traffic into the TCAS with TA/RA capabilities of PS1 (the RA is abviously not synched to the "opposing aircraft, lol), much like the great TCAS for PIC767.Anyway, thanks for your reply and good luck with your conversion and career!

I used PS1 to prepare for my interview and whilst on the -400. You can download mods that make it match OJA-R, OJS-U or VH-OEB, C and D (propbably even the ERs now)!

That actually sounds very handy! So far the training system hasn't acknowledged the ER's even exist ;-)And you know all the voice callouts by the PNF were done by a certain computer-keen 767 captain.