DH8-100 flight crew experienced problems with breathing and discovered cabin altitude warning had fa...

Attributes
ACN	321193
Time
Date	199511
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ahn
State Reference	GA
Altitude	msl bound lower : 10000 msl bound upper : 17400
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : lga
Operator	common carrier : air carrier
Make Model Name	Dash 8-100
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	climbout : intermediate altitude
Route In Use	enroute airway : ztl
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 250 flight time total : 14000 flight time type : 3000
ASRS Report	321193
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 260 flight time total : 8500 flight time type : 2950
ASRS Report	321307
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : declared emergency flight crew : overcame equipment problem other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

While climbing to our assigned altitude of FL180, both crew members noted an apparent loss of cabin pressurization. Began descent to 14000 ft while captain began emergency checklist. After cycling all pressurization controls we regained control of cabin altitude. Maximum cabin altitude approximately 11500 ft. 'Cabin pressurization' emergency caption light failed to light at 10000 ft as designed. Cabin pressure began to descend normally to normal altitude. Several sick passenger reported by flight attendant. Descended to 10000 ft as per emergency procedures and continued to destination. Callback conversation with reporter revealed the following information: reporter captain states that the problem is that there is no cockpit procedure to test the function of the cabin pressurization emergency warning system, and he is uncertain about maintenance checks. (Cabin controller problems, only, are checked by a built-in test function which causes a fault light to go out when a test is satisfactory.) the possible cause of the pressure loss was a forward outflow valve that was stuck in an open position. The captain remembers checking the cabin altitude during the climb checklist at 2500 ft, and randomly, at 6000 ft. There were no abnormal indications. Captain states that a less experienced crew or a longer delay in the failure to recognize the loss of pressurization, would have led to a flight out over the gulf. Captain has reported this problem to the company, and no action taken, so far. Since this incident, the reporter checked another DH8-100 while on a ferry flight, and again, the emergency caption light did not illuminate at the 10000 ft cabin altitude. He has checked with other pilots and guesses that 50 percent of the fleet cabin pressure emergency caption lights will not check out. The checklists used by the flcs are supplied by dehavilland and modified by the company. The reporter believes that flight crew cabin altitude warning checks are nonexistent. Supplemental information from acn 321307: both crew members went on oxygen. First indication of problem was shortness of oxygen and problems breathing.

Original NASA ASRS Text

Title: DH8-100 FLC EXPERIENCED PROBS WITH BREATHING AND DISCOVERED CABIN ALT WARNING HAD FAILED TO ILLUMINATE, AS DESIGNED. ACFT WAS DSNDED TO A SAFE ALT, EMER CHKLIST ITEMS WERE COMPLETED, AND FLT CONTINUED TO DEST.

Narrative: WHILE CLBING TO OUR ASSIGNED ALT OF FL180, BOTH CREW MEMBERS NOTED AN APPARENT LOSS OF CABIN PRESSURIZATION. BEGAN DSCNT TO 14000 FT WHILE CAPT BEGAN EMER CHKLIST. AFTER CYCLING ALL PRESSURIZATION CTLS WE REGAINED CTL OF CABIN ALT. MAX CABIN ALT APPROX 11500 FT. 'CABIN PRESSURIZATION' EMER CAPTION LIGHT FAILED TO LIGHT AT 10000 FT AS DESIGNED. CABIN PRESSURE BEGAN TO DSND NORMALLY TO NORMAL ALT. SEVERAL SICK PAX RPTED BY FLT ATTENDANT. DSNDED TO 10000 FT AS PER EMER PROCS AND CONTINUED TO DEST. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR CAPT STATES THAT THE PROB IS THAT THERE IS NO COCKPIT PROC TO TEST THE FUNCTION OF THE CABIN PRESSURIZATION EMER WARNING SYS, AND HE IS UNCERTAIN ABOUT MAINT CHKS. (CABIN CTLR PROBS, ONLY, ARE CHKED BY A BUILT-IN TEST FUNCTION WHICH CAUSES A FAULT LIGHT TO GO OUT WHEN A TEST IS SATISFACTORY.) THE POSSIBLE CAUSE OF THE PRESSURE LOSS WAS A FORWARD OUTFLOW VALVE THAT WAS STUCK IN AN OPEN POS. THE CAPT REMEMBERS CHKING THE CABIN ALT DURING THE CLB CHKLIST AT 2500 FT, AND RANDOMLY, AT 6000 FT. THERE WERE NO ABNORMAL INDICATIONS. CAPT STATES THAT A LESS EXPERIENCED CREW OR A LONGER DELAY IN THE FAILURE TO RECOGNIZE THE LOSS OF PRESSURIZATION, WOULD HAVE LED TO A FLT OUT OVER THE GULF. CAPT HAS RPTED THIS PROB TO THE COMPANY, AND NO ACTION TAKEN, SO FAR. SINCE THIS INCIDENT, THE RPTR CHKED ANOTHER DH8-100 WHILE ON A FERRY FLT, AND AGAIN, THE EMER CAPTION LIGHT DID NOT ILLUMINATE AT THE 10000 FT CABIN ALT. HE HAS CHKED WITH OTHER PLTS AND GUESSES THAT 50 PERCENT OF THE FLEET CABIN PRESSURE EMER CAPTION LIGHTS WILL NOT CHK OUT. THE CHKLISTS USED BY THE FLCS ARE SUPPLIED BY DEHAVILLAND AND MODIFIED BY THE COMPANY. THE RPTR BELIEVES THAT FLC CABIN ALT WARNING CHKS ARE NONEXISTENT. SUPPLEMENTAL INFO FROM ACN 321307: BOTH CREW MEMBERS WENT ON OXYGEN. FIRST INDICATION OF PROB WAS SHORTNESS OF OXYGEN AND PROBS BREATHING.

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.

DH8-100 flight crew experienced problems with breathing and discovered cabin altitude warning had failed to illuminate, as designed. Aircraft was descended to a safe altitude, emergency checklist items were completed, and flight continued to destination.