<< >> NASA ASRS Report 249585, August 1993

A misset cabin altitude control is cause for precautionary descent to lower altitude where error is discovered by flight crew.

Attributes
ACN	249585
Time
Date	199308
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : den
State Reference	CO
Altitude	msl bound lower : 41000 msl bound upper : 43000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zdv
Operator	common carrier : air taxi
Make Model Name	Light Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 147 flight time total : 6300 flight time type : 618
ASRS Report	249585
Person 2
Affiliation	company : air taxi
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	non adherence : published procedure other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : exited adverse environment flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

After being level at FL410 for approximately 1 hour, we requested and were granted a climb to FL450. Upon passing FL430 the cabin altitude reached 11000 ft and a precautionary descent was made to FL250. Upon reaching FL250 it was noted that the pressurization controller had been set for 11000 ft. Upon resetting the controller to 8000 ft and observing normal indications, a climb was made to FL410 and the flight proceeded normally. This situation could have been prevented if both pilots double-checked the pressurization controller any time an adjustment is made to it.

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Original NASA ASRS Text

Title: A MISSET CABIN ALT CTL IS CAUSE FOR PRECAUTIONARY DSCNT TO LOWER ALT WHERE ERROR IS DISCOVERED BY FLC.

Narrative: AFTER BEING LEVEL AT FL410 FOR APPROX 1 HR, WE REQUESTED AND WERE GRANTED A CLB TO FL450. UPON PASSING FL430 THE CABIN ALT REACHED 11000 FT AND A PRECAUTIONARY DSCNT WAS MADE TO FL250. UPON REACHING FL250 IT WAS NOTED THAT THE PRESSURIZATION CTLR HAD BEEN SET FOR 11000 FT. UPON RESETTING THE CTLR TO 8000 FT AND OBSERVING NORMAL INDICATIONS, A CLB WAS MADE TO FL410 AND THE FLT PROCEEDED NORMALLY. THIS SIT COULD HAVE BEEN PREVENTED IF BOTH PLTS DOUBLE-CHKED THE PRESSURIZATION CTLR ANY TIME AN ADJUSTMENT IS MADE TO IT.

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.