<< >> NASA ASRS Report 580550, May 2003

A B737-300 in cruise at FL330 made an emergency descent to FL180 due to cabin altitude climbing to 11000 ft. Caused by #2 engine bleed trip.

Attributes
ACN	580550
Time
Date	200305
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : hnn.vortac
State Reference	WV
Altitude	msl bound lower : 20000 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid.artcc
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 169 flight time total : 15081 flight time type : 6012
ASRS Report	580550
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical other anomaly other other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : cabin altitude indicator other flight crewa other flight crewb
Resolutory Action	aircraft : equipment problem dissipated flight crew : returned to assigned altitude flight crew : overcame equipment problem
Consequence	other
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Aircraft

Narrative:

Bleed trip on #2 engine forced rapid descent to FL180 as cabin altitude climbed above 10000 ft to approximately 11000 ft. ATC provided a clearance initially to FL270, then FL180 while a conflicting aircraft below FL180. By the time the aircraft had reached FL200, the bleed trip had been reset, cabin was back under 10000 ft and ATC was advised by flight crew that no further descent was necessary below FL180 at that time. Pressurization system operated normally for remainder of flight. Uneventful landing.

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Original NASA ASRS Text

Title: A B737-300 IN CRUISE AT FL330 MADE AN EMER DSCNT TO FL180 DUE TO CABIN ALT CLBING TO 11000 FT. CAUSED BY #2 ENG BLEED TRIP.

Narrative: BLEED TRIP ON #2 ENG FORCED RAPID DSCNT TO FL180 AS CABIN ALT CLBED ABOVE 10000 FT TO APPROX 11000 FT. ATC PROVIDED A CLRNC INITIALLY TO FL270, THEN FL180 WHILE A CONFLICTING ACFT BELOW FL180. BY THE TIME THE ACFT HAD REACHED FL200, THE BLEED TRIP HAD BEEN RESET, CABIN WAS BACK UNDER 10000 FT AND ATC WAS ADVISED BY FLT CREW THAT NO FURTHER DSCNT WAS NECESSARY BELOW FL180 AT THAT TIME. PRESSURIZATION SYS OPERATED NORMALLY FOR REMAINDER OF FLT. UNEVENTFUL LNDG.

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.