737-800 Nose Pitch at Hight Altitude

Trying to learn how to fly the 737 and at 3000 ft on auto pilot the nose is pitching up 3-4 degrees. Is this normal? Looks kind of high when looking at to exterior view. I read it should pitch up a little.

Mike - When I first started flying the 737, I too wondered about the pitch up attitude. In cruise, it will be slightly nose up, sounds like 3-4* is not much to worry about. What I still get worried about, is the pitch up attitude you will see (exterior view) when approaching an airport at lower airspeeds with flaps deployed. The airspeed is appropriate and haven't had one stall on me yet! Seems like some of the jetliners do not pitch up as much on their approaches! Just my observation, maybe others will chime in and confirm my thoughts!

 

Rick

Yes, it's normal. What happens is that the air is much thinner up there at jet altitudes, which gives a lower IAS for a given actual speed through the air (TAS). But any aircraft responds related to air density, rather than to TAS, and you may have also noticed that you have much lower indicated airspeeds at those altitudes for a given TAS (or groundspeed in no-wind conditions, too).

 

An aircraft at slower IAS loses lift compared to a high IAS, thus it needs a greater Angle Of Attack (AOA) to generate the same lift at that lower IAS. Since the reduced IAS at high altitudes requires a higher AOA, the pitch attitude will be more nose up.

 

There is a lot more information available on Wikipedia under density altitude, indicated airspeed, and even Boing's explanation of angle of attack. There's lots more out there, too, but in essence, the increased angle of attack generates more lift, but it results an a higher pitch attitude.

Pitch up at cruise altitude is normal. I only have a few aircraft that look level in cruise flight.

What I still get worried about, is the pitch up attitude you will see (exterior view) when approaching an airport at lower airspeeds with flaps deployed. The airspeed is appropriate and haven't had one stall on me yet! Seems like some of the jetliners do not pitch up as much on their approaches!

 

That's correct. Different aircraft are designed with different behaviors and, for example, older (perhaps newer too) 737s don't pitch up nearly as much as a 707 or 767, in terms of apparent pitch attitude. Angle of incidence, angle of attack, airfoil design, flap design, and a number of other factors determine what a specific aircraft's pitch attitude will be under a given set of circumstances. You might also look at the C-172 (as only one example) with no flaps and with each additional 10º increment of flaps while maintaining a constant indicated airspeed. The pitch attitude changes with each flap change. Also, with no change in flap setting, the pitch attitude changes with each change in power setting, if you still maintain a constant IAS. A Bonanza, for example will change, too, but to a different degree.

 

People tend to think of the elevator as a pitch control, which to a degree is true. But more importantly it is actually an AOA (Angle Of Attack) control.

AS above.

 

http://www.b737mrg.net/downloads/b737mrg_powersettings_737-NG.pdf

 

 

And you do notice it in the real aircraft when on approach. As in the charts, it can be 5-6 degrees nose up at different stages.

Wow! You guys are awesome! For years I have only played with the light aircraft, war birds and military fighters. I bought the Saitek Switch Panel and Multi Panel and they really help me with the heavies. Before If I even got off the ground I didn't stay up very long and landing though still a little practice is in order like a lot of air disasters to low and to slow on the approach. But with your help I am learning!

AS above.

 

http://www.b737mrg.net/downloads/b737mrg_powersettings_737-NG.pdf

 

 

And you do notice it in the real aircraft when on approach. As in the charts, it can be 5-6 degrees nose up at different stages.

 

 

Awesome! I downloaded it for a cheat sheet.