Return land mandated by air carrier large transport being unable to pressurize.

Attributes
ACN	343447
Time
Date	199607
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : bos
State Reference	MA
Altitude	msl bound lower : 5000 msl bound upper : 5000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : bos
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	climbout : initial cruise other other
Route In Use	departure other departure sid : sid
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 150
ASRS Report	343447
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

During the departure from boston logan airport it was determined that the aircraft would not pressurize. The aircraft was over maximum landing weight and the runways at logan field were wet so we elected to dump 12000 pounds of fuel to get the aircraft within allowable landing weight. The fuel was dumped heading 90 degrees at approximately 15-20 NM and stayed between those DME's in a box pattern. Dumping started at XA12Z and ended at XA20Z. An uneventful landing was then made at bos.

Original NASA ASRS Text

Title: RETURN LAND MANDATED BY ACR LGT BEING UNABLE TO PRESSURIZE.

Narrative: DURING THE DEP FROM BOSTON LOGAN ARPT IT WAS DETERMINED THAT THE ACFT WOULD NOT PRESSURIZE. THE ACFT WAS OVER MAX LNDG WT AND THE RWYS AT LOGAN FIELD WERE WET SO WE ELECTED TO DUMP 12000 LBS OF FUEL TO GET THE ACFT WITHIN ALLOWABLE LNDG WT. THE FUEL WAS DUMPED HDG 90 DEGS AT APPROX 15-20 NM AND STAYED BTWN THOSE DME'S IN A BOX PATTERN. DUMPING STARTED AT XA12Z AND ENDED AT XA20Z. AN UNEVENTFUL LNDG WAS THEN MADE AT BOS.

Data retrieved from NASA's ASRS site as of July 2007 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.