B737-700 displays flight characteristics consistent with an aft cg and excessive gross weight. Fligh...

Attributes
ACN	747096
Time
Date	200707
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 37000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zzz.artcc tower : iad.tower
Operator	common carrier : air carrier
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 250 flight time type : 5000
ASRS Report	747096
Events
Anomaly	aircraft equipment problem : less severe non adherence : published procedure other anomaly
Independent Detector	aircraft equipment other aircraft equipment : stall wing system other flight crewa
Resolutory Action	flight crew : exited adverse environment flight crew : overcame equipment problem flight crew : overrode automation
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Aircraft

Narrative:

Climbing out of FL370; aircraft flashed buffet alert while in VNAV mode; autoplt then disengaged; mach .63; as 220. Manually accelerated aircraft to normal climb. Aircraft would not accelerate in level flight at FL370 with N1 power. Initiated a descent to recover airspeed. Climbed normally to FL400. Upon reaching FL400; VNAV reengaged. Speed command was for .788; aircraft would not slow below .804. Reprogrammed to .76; aircraft slowed; reprogrammed to 'econ' and aircraft responded normally. Normal descent until beginning to slow for the approach. As we put out the flaps at 210K; aircraft began a slight porpoise motion and continued as we slowed to 170 and flaps 15 degrees. I disengaged the autoplt and hand flew the approach. The aircraft exhibited aft center of gravity tendencies with slow control response and a lag in response to vertical control inputs. Landed flaps 30 degrees uneventful. The first officer commented after landing and discussion about this that he thought the rotation was rapid and thinking back the aircraft actually rotated itself; but I kind of wrote it off to 'one of those things.' center of gravity was given to us as 24.7% and takeoff weight was 128000 pounds. Thinking back; center of gravity could have been a big factor in the aircraft not accelerating at 370. Better attentiveness to aircraft condition in the autoflt mode. Be more alert to loading conditions and be more suspect of things that sometimes are logged up to 'one of those things.'

Original NASA ASRS Text

Title: B737-700 DISPLAYS FLT CHARACTERISTICS CONSISTENT WITH AN AFT CG AND EXCESSIVE GROSS WEIGHT. FLT CREW ALSO SUSPECTS FAULTY FLT GUIDANCE SYS.

Narrative: CLBING OUT OF FL370; ACFT FLASHED BUFFET ALERT WHILE IN VNAV MODE; AUTOPLT THEN DISENGAGED; MACH .63; AS 220. MANUALLY ACCELERATED ACFT TO NORMAL CLB. ACFT WOULD NOT ACCELERATE IN LEVEL FLT AT FL370 WITH N1 PWR. INITIATED A DSCNT TO RECOVER AIRSPD. CLBED NORMALLY TO FL400. UPON REACHING FL400; VNAV REENGAGED. SPD COMMAND WAS FOR .788; ACFT WOULD NOT SLOW BELOW .804. REPROGRAMMED TO .76; ACFT SLOWED; REPROGRAMMED TO 'ECON' AND ACFT RESPONDED NORMALLY. NORMAL DSCNT UNTIL BEGINNING TO SLOW FOR THE APCH. AS WE PUT OUT THE FLAPS AT 210K; ACFT BEGAN A SLIGHT PORPOISE MOTION AND CONTINUED AS WE SLOWED TO 170 AND FLAPS 15 DEGS. I DISENGAGED THE AUTOPLT AND HAND FLEW THE APCH. THE ACFT EXHIBITED AFT CTR OF GRAVITY TENDENCIES WITH SLOW CTL RESPONSE AND A LAG IN RESPONSE TO VERT CTL INPUTS. LANDED FLAPS 30 DEGS UNEVENTFUL. THE FO COMMENTED AFTER LNDG AND DISCUSSION ABOUT THIS THAT HE THOUGHT THE ROTATION WAS RAPID AND THINKING BACK THE ACFT ACTUALLY ROTATED ITSELF; BUT I KIND OF WROTE IT OFF TO 'ONE OF THOSE THINGS.' CTR OF GRAVITY WAS GIVEN TO US AS 24.7% AND TKOF WT WAS 128000 LBS. THINKING BACK; CTR OF GRAVITY COULD HAVE BEEN A BIG FACTOR IN THE ACFT NOT ACCELERATING AT 370. BETTER ATTENTIVENESS TO ACFT CONDITION IN THE AUTOFLT MODE. BE MORE ALERT TO LOADING CONDITIONS AND BE MORE SUSPECT OF THINGS THAT SOMETIMES ARE LOGGED UP TO 'ONE OF THOSE THINGS.'

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

B737-700 displays flight characteristics consistent with an aft cg and excessive gross weight. Flight crew also suspects faulty flight guidance system.