B737 flight crew reports pneumatic duct pressure dropping below 10 psi at start of descent. Pressurization becomes an issue until the outflow valve is manually closed.

Home

Browse by month

Random

Latest

About

Contact

Attributes
ACN	810292
Time
Date	200811
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : den.airport
State Reference	CO
Altitude	msl single value : 36000
Environment
Flight Conditions	VMC
Aircraft 1
Controlling Facilities	artcc : zdv.artcc tower : ord.tower
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	descent : vacating altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 30 flight time total : 7000 flight time type : 1300
ASRS Report	810292
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 210 flight time total : 11000 flight time type : 6000
ASRS Report	810290
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	aircraft equipment other aircraft equipment : cabin rate ind other flight crewa
Resolutory Action	controller : issued new clearance flight crew : overcame equipment problem
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

At the top of descent; at FL360; both throttles retarded to idle. At that point; the duct pressure on both engines fell to less than 10 psi; on both engines. The cabin altitude started to rise. The pressurization panel was first placed in standby; which had no corrective action. The cabin did exceed 10000 ft. The QRH for intermittent cabin altitude warning horn was called for and run. The pressurization panel was then placed in manual AC; and the outflow was closed and cabin altitude control was regained at about 10500 ft. All the while; the plane was being descended to an asked for given clearance of 10000 ft. Cabin altitude in manual AC was controled to about 5200 ft; in preparation for landing. Cabin pressure was controled the rest of the flight; which was about 25 more mins. Uneventful approach and landing was made by the captain.

Original NASA ASRS Text

Title: B737 FLIGHT CREW REPORTS PNEUMATIC DUCT PRESSURE DROPPING BELOW 10 PSI AT START OF DESCENT. PRESSURIZATION BECOMES AN ISSUE UNTIL THE OUTFLOW VALVE IS MANUALLY CLOSED.

Narrative: AT THE TOP OF DSCNT; AT FL360; BOTH THROTTLES RETARDED TO IDLE. AT THAT POINT; THE DUCT PRESSURE ON BOTH ENGS FELL TO LESS THAN 10 PSI; ON BOTH ENGS. THE CABIN ALT STARTED TO RISE. THE PRESSURIZATION PANEL WAS FIRST PLACED IN STANDBY; WHICH HAD NO CORRECTIVE ACTION. THE CABIN DID EXCEED 10000 FT. THE QRH FOR INTERMITTENT CABIN ALT WARNING HORN WAS CALLED FOR AND RUN. THE PRESSURIZATION PANEL WAS THEN PLACED IN MANUAL AC; AND THE OUTFLOW WAS CLOSED AND CABIN ALT CTL WAS REGAINED AT ABOUT 10500 FT. ALL THE WHILE; THE PLANE WAS BEING DSNDED TO AN ASKED FOR GIVEN CLRNC OF 10000 FT. CABIN ALT IN MANUAL AC WAS CTLED TO ABOUT 5200 FT; IN PREPARATION FOR LNDG. CABIN PRESSURE WAS CTLED THE REST OF THE FLT; WHICH WAS ABOUT 25 MORE MINS. UNEVENTFUL APCH AND LNDG WAS MADE BY THE CAPT.

Data retrieved from NASA's ASRS site as of May 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.