737-900 Rotate Performance

[Guest mcbootus]

Hi chaps,I have mostly been flying the -800 since the release and I do love this plane very much, and recently i have started flying the -900, but I noticed something a bit strange.When you rotate the -900 the elevator performance seems to be exagerated, a slight input results in massive nose up. I believe I have set the trim correctly to 4.6 iso 4.9 , but still the -900 has a much greater rotate movement than the -800.Am I doing something wrong or does the -900 elevator have more deflection for a given input, or maybe the flight model needs a bit of tweaking?Many thanks in advance, as usual! :)mcbootus

[Guest mcbootus]

Oh!Or maybe im setting the trim incorrectly! Do you have to do a bit of guesswork with the trim as the increments seem to be summarized, so 4.9 is infact 5.0 twice clicked down, and 4.6 is 4.5 once clicked up?It sounds confusing but certain trim inputs arent shown on the trim gauge.Thanks again.mcbootus

[Guest nandrzej]

I know the tail on the 900 is further from the wheels, but your post seems to indicate a bigger difference than this would suggest. What about cargo placement?Nick

[Guest mcbootus]

Hi Nick,Good call, I forgot to mention the load settings of course!I have the following load settings for the -900 aircraft:900_SINGLE: Passengers - Max (189)Forward - 5553 Aft - 5348ZFW - 139501900_MIXED:Passengers - Max (177)Forward - 6562Aft - 5602ZFW - 138604Fuel load - Approx 30-40% on both configurations.To be honest I guestimated these load settings, some advice would be greatly appreciated. My -800 is set up similarly, fully loaded passengers and then as much cargo as I can get in, and 30-40% fuel.Thanks.mcbootus

[Guest nandrzej]

I had a fly with your load in the 900. I see what you mean, it fair rockets off the runway. It feels faster than my 600 ;-)the FMC had CG at 26.7% (unsure if this is used?) and trim at 4.6, with V2 at 151 for a flaps 15 takeoffI remember an earlier post saying the FMC was using interpolation to obtain speed results, something to do with zeros being used in the data. Remember all the posts about the 900 bouncing, it could be the same issue but for takeoff and the speed is a bit high, try rotating 5-10 knots earlier and see if it feels the same as the 800. Remember to hold at 8 degrees until you lift off, you will strike the tail at 9 degrees if you over rotate.really I am clutching at straws, sounds plausible though.I am not sure if the temp patch addressed this, are you runnning it and would any of the PMDG team care to comment re FMC speeds.

[Mats_J 2]

One thing to note here boys.You are taking off with flaps 15 in the -900 while usually flaps 1 is used on the -600/700. That creates quite some extra lift. To me the 15 flaps seems a bit of an overkill. 10 should be enough, even if I could be way off here. ;-)Cheers,

[Guest nandrzej]

Yeah fair comment, 15 was probably overkill, It is a legitimate setting for the 900 at that weight though. I should try with a lesser flaps setting for true comparison.My comments about V2 speed is a bit off I think. I RTFM and in 01_Takeoff_Performance_737_678900_V14 page 1-20 and the V2 speed is bang on, scratch that idea. My apologies to all.cheers, Nick

[Guest Balrog]

Flaps 5 for departure should be quite sufficient, If I`m lightly loaded I`ll even use flaps 1, at least on the 6 and 7. Don`t think that the 9 would need more than 5.Work at an airport where I see more 6, 7 and 8 departures every day than I care to remember, never seen any go with more than 5. Neither as a PAX, whenever seated behind the wings have I seen more than 5.Cheers,Kjell.