DC10 crew experiences faulty pitot static instruments and returns to field.

Attributes
ACN	717651
Time
Date	200611
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : atl.airport
State Reference	GA
Altitude	msl single value : 35000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : ztl.artcc
Operator	common carrier : air carrier
Make Model Name	DC-10 30F
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	climbout : initial
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 21 flight time total : 14000 flight time type : 1843
ASRS Report	717651
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical altitude deviation : undershoot
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : landed as precaution
Consequence	other
Supplementary
Problem Areas	Company Aircraft
Primary Problem	Aircraft

Narrative:

Departed atl en route to zurich. First officer was PF and I (captain) was handling ATC communications and navigation. I first noticed a discrepancy between instruments while climbing through 5000 ft. I observed 240 KIAS while we normally climb at 250 KTS. I made no comment (mistake #1) thinking first officer was climbing at the 240 KT clean maneuvering speed. While accelerating above 10000 ft to 320 KTS the difference between captain and first officer airspds was obvious; discussed; and using standby instruments we verified captain's air data instruments (airspeed; vsi; altitude) faulty. Following checklist procedures we switched sources so that all air data instruments were driven by #2 (first officer's) air data computer. We arranged a return to atl with ATC; who queried us about our altitude. Controller saw us 2500 ft low until we switched transponder from #1 to #2 -- an action not on the faulty instruments checklist. We failed to think through the situation and consider this (mistake #2). We completed the return to atl without further incident. The problem was a loose static air line leading to the #1 air data computer.

Original NASA ASRS Text

Title: DC10 CREW EXPERIENCES FAULTY PITOT STATIC INSTS AND RETURNS TO FIELD.

Narrative: DEPARTED ATL ENRTE TO ZURICH. FO WAS PF AND I (CAPT) WAS HANDLING ATC COMS AND NAV. I FIRST NOTICED A DISCREPANCY BTWN INSTS WHILE CLBING THROUGH 5000 FT. I OBSERVED 240 KIAS WHILE WE NORMALLY CLB AT 250 KTS. I MADE NO COMMENT (MISTAKE #1) THINKING FO WAS CLBING AT THE 240 KT CLEAN MANEUVERING SPD. WHILE ACCELERATING ABOVE 10000 FT TO 320 KTS THE DIFFERENCE BTWN CAPT AND FO AIRSPDS WAS OBVIOUS; DISCUSSED; AND USING STANDBY INSTS WE VERIFIED CAPT'S AIR DATA INSTS (AIRSPD; VSI; ALT) FAULTY. FOLLOWING CHKLIST PROCS WE SWITCHED SOURCES SO THAT ALL AIR DATA INSTS WERE DRIVEN BY #2 (FO'S) AIR DATA COMPUTER. WE ARRANGED A RETURN TO ATL WITH ATC; WHO QUERIED US ABOUT OUR ALT. CTLR SAW US 2500 FT LOW UNTIL WE SWITCHED XPONDER FROM #1 TO #2 -- AN ACTION NOT ON THE FAULTY INSTS CHKLIST. WE FAILED TO THINK THROUGH THE SIT AND CONSIDER THIS (MISTAKE #2). WE COMPLETED THE RETURN TO ATL WITHOUT FURTHER INCIDENT. THE PROB WAS A LOOSE STATIC AIR LINE LEADING TO THE #1 AIR DATA COMPUTER.

Data retrieved from NASA's ASRS site as of January 2009 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.