DVA1767
Captain, B727-200
Joined on July 02 2004
Century Club
Online Century Club
Midwestern United States
107 legs, 156.8 hours
104 legs,
153.2 hours online 6 legs,
12.1 hours event 501 legs, 763.5 hours total
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Posted onPost created on
September 10 2004 05:30 ET by Michael Carter
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This is the W&B date from the config file for the B722:
[WEIGHT_AND_BALANCE]
max_gross_weight=184800
empty_weight=119315
reference_datum_position=0.000, 0.000, 0.000
empty_weight_CG_position=-4.143, 0.000, 0.000
max_number_of_stations=50
station_load.0=0.000000,0.000000,0.000000,0.000000
; Moments of Inertia
empty_weight_pitch_MOI=3373651
empty_weight_roll_MOI=664554
empty_weight_yaw_MOI=3980724
empty_weight_coupled_MOI=0
I have a couple of questions about this information.
1.) Does the CG position change when fuel is loaded or burned?
2.) Why are the reference datum positions all zero?
3.) Why are all of the station load positions zero?
My observations indicate that it makes no difference how much fuel is loaded or where it's loaded, or burned; the same amount of "UP" trim is used for take-off settings every time. The trim setting is at about 1.75 units nose up which would indicate the CG is well more than 42" aft of the datum plane.
I believe this is out of the W&B limitations for the B722, though I don't have a graph for that, only a list of recommended trim and flap settings based on computed CG point aft of the datum. The B722 is tail-heavy to begin with and a CG that far aft would result in an uncontrollable pitch-up at rotation leading to stall.
42" aft of the datum is as high as it goes on my chart, and that is a trim setting of 2.5 regardless of flap setting.
I'm not complaining about the flight characteristics of the model. On the contrary, at the trim setting I use for take-off it will pitch-up and climb at 1800fpm hands-off by itself with no adjustment needed until after 10,000MSL.
I guess my question boils down to whether the CG is fixed and unchangeable and if it's too far aft. Not having flown a B722 I wouldn't know whether the flight model is accurate or not.
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DVA043
Senior Captain, MD-11
OLP
Joined on June 10 2001
Event Half Century Club
Online Double Century Club
50 State Club
DVA Twenty-Year Anniversary
Everett 1500 Club
Bi-Millennium Club
Four Million Mile Club
"Col. Panic" Marietta, GA
2,241 legs, 8,967.3 hours
240 legs,
553.9 hours online 1,899 legs,
7,760.4 hours ACARS 75 legs,
196.3 hours event 2,277 legs, 9,102.2 hours total 91 legs dispatched, 66.4
hours
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Posted onPost created on
September 10 2004 17:26 ET by Luke Kolin
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DVA1767
Captain, B727-200
Joined on July 02 2004
Century Club
Online Century Club
Midwestern United States
107 legs, 156.8 hours
104 legs,
153.2 hours online 6 legs,
12.1 hours event 501 legs, 763.5 hours total
|
Posted onPost created on
September 10 2004 18:39 ET by Michael Carter
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