While climbing through about 17;000 ft; a B737-700's cabin altitude warning horn sounded so an emerg...

Attributes
ACN	1011165
Time
Date	201205
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737-500
Operating Under FAR Part	Part 121
Flight Phase	Climb
Component
Aircraft Component	Pressurization System
Person 1
Function	First Officer Pilot Not Flying
Experience	Flight Crew Last 90 Days 603
Person 2
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 419 Flight Crew Type 18000
Events
Anomaly	Aircraft Equipment Problem Critical

Narrative:

Departed runway 21 flight uneventful through 10;000 ft and associated climb check. Shortly thereafter; ARTCC turned us on our route eastbound. ARTCC then reported loss of transponder and was receiving only a primary target. While troubleshooting this; captain (pilot flying) stated LNAV and VNAV modes of the FMC would not arm. Very shortly thereafter; passing 17;000 ft the cabin altitude warning activated. After complying with the critical action items; confirmed cabin altitude at 10;000 ft and climbing; but pressurization systems were set normally. Pilot flying began immediate descent to lower altitude while I worked to coordinate with ARTCC for a return to the departure airport; while also running checklist for loss of cabin pressure. Cabin altitude topped out at approximately 12;500 ft. We returned uneventfully.

Original NASA ASRS Text

Title: While climbing through about 17;000 FT; a B737-700's Cabin Altitude Warning horn sounded so an emergency was declared and the flight returned to the departure airport.

Narrative: Departed Runway 21 flight uneventful through 10;000 FT and associated Climb check. Shortly thereafter; ARTCC turned us on our route eastbound. ARTCC then reported loss of transponder and was receiving only a primary target. While troubleshooting this; Captain (pilot flying) stated LNAV and VNAV modes of the FMC would not arm. Very shortly thereafter; passing 17;000 FT the Cabin Altitude Warning activated. After complying with the Critical Action Items; confirmed cabin altitude at 10;000 FT and climbing; but pressurization systems were set normally. Pilot flying began immediate descent to lower altitude while I worked to coordinate with ARTCC for a return to the departure airport; while also running checklist for loss of cabin pressure. Cabin altitude topped out at approximately 12;500 FT. We returned uneventfully.

Data retrieved from NASA's ASRS site as of July 2013 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.

While climbing through about 17;000 ft; a B737-700's cabin altitude warning horn sounded so an emergency was declared and the flight returned to the departure airport.