B737-500 aircraft was taken OTS after a dent was discovered that exceeded allowable tolerances.

Attributes
ACN	603075
Time
Date	200312
Day	Sat
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : den.airport
State Reference	CO
Altitude	agl single value : 0
Environment
Light	Night
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737-500
Operating Under FAR Part	Part 121
Flight Phase	ground : parked
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 120 flight time total : 12500 flight time type : 82
ASRS Report	603075
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 210 flight time total : 3500 flight time type : 600
ASRS Report	603266
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	other other : 3
Resolutory Action	none taken : detected after the fact other
Consequence	other other other
Supplementary
Problem Areas	Company Aircraft Flight Crew Human Performance
Primary Problem	Ambiguous

Narrative:

Captain completed preflight walkaround at approximately XA25. At approximately XB00, ramp service contacted captain by headset that pushback was being delayed due to ramp service having discovered a dent in the bottom of the APU exhaust shroud during their inspection and that a mechanic was coming to inspect. After approximately 1 hour delay, pilot crew was advised that dent exceeded allowable tolerances and that flight would be changed to another aircraft. After jetway was in place and passenger deplaned, both captain and first officer examined the discovered dent. It was approximately 6 inches long, 6 inches across, and 1 inch deep (in a cross shape) and had flecks of yellow paint imbedded in the horizontal cross portion. View of this could not be discerned during the course of the normal walkaround (even with flashlight), but required standing directly under the APU exhaust tail tip and looking straight up. Supplemental information from acn 603266: the captain stated to myself and the pushback crew that he had not seen any damage during his walkaround. Maintenance was notified, inspected the dent, and determined that said dent exceeded tolerances.

Original NASA ASRS Text

Title: B737-500 ACFT WAS TAKEN OTS AFTER A DENT WAS DISCOVERED THAT EXCEEDED ALLOWABLE TOLERANCES.

Narrative: CAPT COMPLETED PREFLT WALKAROUND AT APPROX XA25. AT APPROX XB00, RAMP SVC CONTACTED CAPT BY HEADSET THAT PUSHBACK WAS BEING DELAYED DUE TO RAMP SVC HAVING DISCOVERED A DENT IN THE BOTTOM OF THE APU EXHAUST SHROUD DURING THEIR INSPECTION AND THAT A MECH WAS COMING TO INSPECT. AFTER APPROX 1 HR DELAY, PLT CREW WAS ADVISED THAT DENT EXCEEDED ALLOWABLE TOLERANCES AND THAT FLT WOULD BE CHANGED TO ANOTHER ACFT. AFTER JETWAY WAS IN PLACE AND PAX DEPLANED, BOTH CAPT AND FO EXAMINED THE DISCOVERED DENT. IT WAS APPROX 6 INCHES LONG, 6 INCHES ACROSS, AND 1 INCH DEEP (IN A CROSS SHAPE) AND HAD FLECKS OF YELLOW PAINT IMBEDDED IN THE HORIZ CROSS PORTION. VIEW OF THIS COULD NOT BE DISCERNED DURING THE COURSE OF THE NORMAL WALKAROUND (EVEN WITH FLASHLIGHT), BUT REQUIRED STANDING DIRECTLY UNDER THE APU EXHAUST TAIL TIP AND LOOKING STRAIGHT UP. SUPPLEMENTAL INFO FROM ACN 603266: THE CAPT STATED TO MYSELF AND THE PUSHBACK CREW THAT HE HAD NOT SEEN ANY DAMAGE DURING HIS WALKAROUND. MAINT WAS NOTIFIED, INSPECTED THE DENT, AND DETERMINED THAT SAID DENT EXCEEDED TOLERANCES.

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.