Is the NGX suppose to be pitched at a certain angle and not completely horizontal when you reach flight level and autopilot is turned on? I found that kind of weird. I'm taking off at 5 degrees flaps, trim is at ~ 6.0 and the plane maintains flight at around an angle of 5-10 degrees.

Cruize pitch or aoa should be 3-5 degrees in cruize if im not mistaken. Increasing IAS the pitch will decrease and vice-versa.

Edited January 21, 201214 yr by christos

almost every plane should have a slightly positiv aoa during cruize. thats how they were designed and what gives them the best cruise characteristics!

Thanks for the quick reply; are they just more aerodynamic at a ~5% positive pitch?

Did you check to see your max altitude in the FMC? If you are at optimum, you'll be a few degrees nose up..

Thanks for the quick reply; are they just more aerodynamic at a ~5% positive pitch?

Greater angle of attack of the wings, generates more lift. Lower angle of attack equates to less lift.The 737 needs to fly in the cruise at this attitude to generate enough lift to remain at that altitude and not sink.It's still debated believe it or not, but these are the four factors that generate lift. Expect disagreement.1. The positive angle of attack deflects air down, and for every action there's an equal and opposite reaction, so the aircraft moves up.Aircraft can fly quite happily upside down, with the wing camber at the bottom, demonsting the role angle of attack plays in regard to lift. Likewise, a model aircraft with no wing camber can fly quite happily [albeit with less lift] with a completely flat wing, as long as there's a positive angle of attack. 2. Air is a fluid, and all fluids cling to a smooth surface, so air clings to the top of the wing, follows the camber, and is thus directed down. Lift is generated for the same reason as the above, for every action there's an equal and opposite reaction.3. Due to the camber on top of the wing, a vortex forms on the trailing edge.This sucks air faster over the top of the wing, and faster moving air equates to lower air pressure. So the pressure is greater under the wing than on top, and lift is generated.4. Thrust! A brick will fly if you give it enough thrust.

Edited January 21, 201214 yr by martin-w

Some nose up, as mentioned, is normal.In fact, there's a 727 out there somewhere in an exec config with the bed at a negative 2 degree tilt, countering the normal pitch up at the aircraft at altitude to lessen the sensation of being tilted back.

1. The positive angle of attack deflects air down, and for every action there's an equal and opposite reaction, so the aircraft moves up.Aircraft can fly quite happily upside down, with the wing camber at the bottom, demonsting the role angle of attack plays in regard to lift. Likewise, a model aircraft with no wing camber can fly quite happily [albeit with less lift] with a completely flat wing, as long as there's a positive angle of attack.2. Air is a fluid, and all fluids cling to a smooth surface, so air clings to the top of the wing, follows the camber, and is thus directed down. Lift is generated for the same reason as the above, for every action there's an equal and opposite reaction.3. Due to the camber on top of the wing, a vortex forms on the trailing edge.This sucks air faster over the top of the wing, and faster moving air equates to lower air pressure. So the pressure is greater under the wing than on top, and lift is generated.4. Thrust! A brick will fly if you give it enough thrust.

LOL..that's the way I learned it too..no disagreement here

It is not so much that the air is deflected down but the camber of the wing forces the air going over the wing to go faster (because it is going farther) than the air over the bottom of the wing. This creates less pressure on the top of the wing than on the bottom. Thereby creating lift.Tom Hibben

It is not so much that the air is deflected down but the camber of the wing forces the air going over the wing to go faster (because it is going farther) than the air over the bottom of the wing. This creates less pressure on the top of the wing than on the bottom. Thereby creating lift.Tom Hibben

Apparently "they" are starting to rethink think this.

It is not so much that the air is deflected down but the camber of the wing forces the air going over the wing to go faster (because it is going farther) than the air over the bottom of the wing. This creates less pressure on the top of the wing than on the bottom. Thereby creating lift.Tom Hibben

You didn't read number 3. :Big Grin:Pressure differential is one factor.The question, is to what degree each factor plays a role.There was a very good documentary on this a few years ago, on the BBC Horizon program. It was highlighted how even NASA gets this wrong on occasion, but the maths still works so nobody is too fussed. It was pointed out by the scientist in question, that too much emphasis is placed on pressure differential.

Edited January 21, 201214 yr by martin-w

There was a very good documentary on this a few years ago, on the BBC Horizon program. It was highlighted how even NASA gets this wrong on occasion, but the maths still works so nobody is too fussed. It was pointed out by the scientist in question, that too much emphasis is placed on pressure differential.

NASA?!?!? Get something wrong?!?!? Surely you jest!There's a scorched mark on Mars from a NASA error, too. Oops.

Transport category aircraft are designed to cruise with a level passenger cabin floor, for comfort. It will vary slightly with gross weight,Cost Index and selected flight level. Longer range aircraft will have it slightly up and gradually leveled as fuel is burned. The angle of wing incidence takes care of that. In an average B737NG and typical load, pitch attitude should be 2-3 degrees nose up initially.

Edited January 21, 201214 yr by opherben

You didn't read number 3. :Big Grin:Pressure differential is one factor.The question, is to what degree each factor plays a role.There was a very good documentary on this a few years ago, on the BBC Horizon program. It was highlighted how even NASA gets this wrong on occasion, but the maths still works so nobody is too fussed. It was pointed out by the scientist in question, that too much emphasis is placed on pressure differential.

Hi Martin,At my age I tend to fall asleep after getting through #2. (grin)Camber also helps in keeping the air over the wing attached better, thereby holding off stall as you slow down.Tom Hibben

At my age I tend to fall asleep after getting through #2. (grin)

:( I know what you mean, I have an under-activee thyroid as an excuse too.But my family don't belive me when I use that excuse.