A DHC8-400's air conditioning packs tripped because of a duct overheat at FL240. After declaring an ...

Narrative:

During cruise at FL240; we got a cabin duct hot caution light. We ran the checklist and nothing happened - light did not extinguish. The gauge was showing in the green. The captain cycled the packs off to see if that would reset it but nothing happened. Then we got a flt comp pack hot caution light. We ran that checklist and nothing changed. We saw our cabin altitude slowly increasing so we donned our O2 masks and started down. We got the cabin press warning light at this time. When we got a hold of ATC we declared an emergency. We initially got 16;000 and then eventually all the way down to 8;000ft. We finished the emergency descent checklist and the pressurization fail checklist in the descent. At 8;000; we talked to maintenance and cycled the packs to the off again and immediately both caution lights went out. After that the pressurization started working again. After talking to dispatch and maintenance; we all felt comfortable with proceeding to our destination. We climbed up to 16;000 and treated the remainder of the flight as normal. During this event; cabin altitude never got above 13;000. We placed several calls to the flight attendant inquiring about the passengers and their well being. We received confirmation that everyone was ok every time.

Original NASA ASRS Text

Title: A DHC8-400's air conditioning Packs tripped because of a duct overheat at FL240. After declaring an emergency and descending to 8;000' the packs were reset and normal operation resumed. The aircraft continued to its planned destination at 16;000'.

Narrative: During cruise at FL240; we got a Cabin Duct Hot Caution Light. We ran the checklist and nothing happened - light did not extinguish. The gauge was showing in the green. The Captain cycled the packs off to see if that would reset it but nothing happened. Then we got a Flt Comp Pack Hot Caution Light. We ran that checklist and nothing changed. We saw our Cabin Altitude slowly increasing so we donned our O2 masks and started down. We got the Cabin Press Warning Light at this time. When we got a hold of ATC we declared an emergency. We initially got 16;000 and then eventually all the way down to 8;000ft. We finished the Emergency Descent Checklist and the Pressurization Fail Checklist in the descent. At 8;000; we talked to maintenance and cycled the packs to the OFF again and immediately both caution lights went out. After that the pressurization started working again. After talking to dispatch and maintenance; we all felt comfortable with proceeding to our destination. We climbed up to 16;000 and treated the remainder of the flight as normal. During this event; Cabin Altitude never got above 13;000. We placed several calls to the Flight Attendant inquiring about the passengers and their well being. We received confirmation that everyone was OK every time.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	846219
Time
Date	200907
Local Time Of Day	1201-1800
Aircraft 1
Make Model Name	Dash 8-400
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Air Conditioning and Pressurization Pack
Person 1
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Commercial
Events
Anomaly	Aircraft Equipment Problem Critical

A DHC8-400's air conditioning packs tripped because of a duct overheat at FL240. After declaring an emergency and descending to 8;000' the packs were reset and normal operation resumed. The aircraft continued to its planned destination at 16;000'.