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ArjenVdv

Touchdown attitude of the -900 NGX

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Hi,As most of you guys probably know, a while ago, before SP1, there were several complains about the touchdown attitude of the NGX. The nose was a little too low upon touchdown. Now after SP1 and SP1B, the -800NGX is perfect! But I haven't flown the -900 for a while, until today. I landed with 40/134, so my FAS was 139, which I perfectly maintained (no autothrottle), the landing was ILS hand flying also. But I noticed when on final approach, that the indicator on the ADI was around 0 degrees, even a little bit in the orange section of the artificial horizon. After I made a really nice landing, I watched the replay, and noticed that the aircraft's nose was even pointed down a little upon final approach, upon landing the aircraft landed pretty much flat. I guess PMDG forgot to tweak the touchdown attitude of the -900 ??? (Not sure and no offence btw). I would like to post a screenshot about this, but I"m not sure how to do this. I press Prt Scrn Sys Req on my keyboard, then paste it in Paint, then save it as a JPEG. But when I attach the file here, it doesn't show up, so how do I post screenshots?


Arjen Vandervelde

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The real life 900 does come in nearly flat - it's right. We're not doing this debate again guys - the 800 was off due to a typo in the one of the values in the air file, nothing more. We aren't guessing on the numbers here for this stuff.


Ryan Maziarz
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Nice video Burt, and i notice he was still crabbed. makes me feel better when I fail to de-crab.As for the 900's attitude, easy to check in the manuals.it should be one degree up i believe for the 900, which IIRC is what I see.

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Nice video Burt, and i notice he was still crabbed. makes me feel better when I fail to de-crab.As for the 900's attitude, easy to check in the manuals.it should be one degree up i believe for the 900, which IIRC is what I see.
I think that most airlines recommend not to decrab completely upon touchdown.Bert Van Bulck

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Thanks Bert.I have just read on the net actually, that not de-crabbing at all is an acceptable crosswind technique for the 737 NG.As long as it's within the cross wind limit.I guess i usually de-crab to a degree, to reduce the strain on the gear and tyres, but not completely. Nice to know I have it right.

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Thanks Bert.I have just read on the net actually, that not de-crabbing at all is an acceptable crosswind technique for the 737 NG.As long as it's within the cross wind limit.I guess i usually de-crab to a degree, to reduce the strain on the gear and tyres, but not completely. Nice to know I have it right.
The thing is, better decrab too late than too early! You can totally screw up your landing if you decrab to early (e.g. at 30 ft). I always decrab about 3 seconds prior to touchdown (e.g. 5 ft). But to stay on topic, my -900 lands flatter than the one in the video!

Arjen Vandervelde

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Best to check in the manuals Arjen. The manuals do state the pitch on approach. I believe for flaps 30.I recall deck angle on approach for the 900 is only about 0.9 degrees up. It's a long aircraft with an artificialy high VREF to avoid a tail strike. the deck angle should be lower than the 800When I land at flap 30, I see a definite pitch up on approach. Didn't notice exactly how much, about one degree I would guess.Flaps 40 does approach at zero pitch for me also.With the short field package, you are able to reduce the VREF though, which will increase pitch. The PMDG FMC doesn't calculate the reduction, but I usually land at VREF with the SFP rather than Vref+5. Although I suspect in reality the reduction with SFP should be lower.

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Best to check in the manuals Arjen. The manuals do state the pitch on approach. I believe for flaps 30.I recall deck angle on approach for the 900 is only about 0.9 degrees up. It's a long aircraft with an artificialy high VREF to avoid a tail strike. the deck angle should be lower than the 800When I land at flap 30, I see a definite pitch up on approach. Didn't notice exactly how much, about one degree I would guess.Flaps 40 does approach at zero pitch for me also.With the short field package, you are able to reduce the VREF though, which will increase pitch. The PMDG FMC doesn't calculate the reduction, but I usually land at VREF with the SFP rather than Vref+5. Although I suspect in reality the reduction with SFP should be lower.
The 900 comes with the SFP as standard, so the VRef given by the FMC should be correct.

Jordan Forrest

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The 900 comes with the SFP as standard, so the VRef given by the FMC should be correct.
The 900ER comes standard with SFP, but the normal -900 (as in the base package) isn't.

Regards,

 

Renzo Marcus

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My mistake, thanks. Whistle.gif
No prob, not everybody knows this, so just an extra reminder! :(

Regards,

 

Renzo Marcus

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Yep, it's just the ER with SFP as standard.It's a pity there aren't any VREF tables anywhere for the SFP.Would be better than guessing.

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After some experimentation with the 900, approaching at VREF - 4 provides the pitch normally associated with the SFP [2.5 up] as per the ER with SFP below. It results in a 2.5 pitch up on approach and a very nice landing.Flight Crew Traing Mnaual section 6.7.3 degree glideslope. Flap 40+5.-600 = 2 degrees up-700 = 2 degrees up-800 = 1.4/2.7 degrees up-900 = 0.9 degrees up-900ER = 2.5 degrees up3 degree glideslope. Flap 30+5.-600 = 3.7 degrees up-700 = 3.7 degrees up-800 = 2.4/3.6 degrees up-900 = 1.6 degrees up-900ER = 2.6 degrees upPMDG have the pitch pretty much correct it seems to me.

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