Narrative:

Aircraft was brought to the wash rack for a wash. The vital areas; or what is called for on paperwork; was covered. The altimeter was covered with proper covering. The altimeter on the pilot side was covered with a covering not up to specifications. The covering spring; or oval shaped ring; was missing from the covering for a long time. All of the existing coverings are damaged in some form or another. There was a visible walk around of airplane; but no oval shaped object was discovered. The long use of inferior material has caused some awareness and the replacing of inferior equipment will prevent this from happening again.callback conversation with reporter revealed the following information: the reporter stated the probe covers are installed on the pitot static probes and are held on with a spring located in the end of the probe that locks the cover on the probe. The covers are worn and some springs are missing but the covers are still used; so a spring missing would not be noticed. The reporter stated the covers are just worn out and need replacement. Reportedly; in this event; the cover was removed and the spring remained on the probe; covering the static ports. The airplane took off and came back right away and the spring was discovered.supplemental information from acn 690434 revealed the following information: during the flight; airspeed/altitude difference was noted by the captain between his instruments and the first officer's. The first officer's instruments concurred with the stand-by instruments.

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Original NASA ASRS Text

Title: UNDETECTED PROBE COVER SPRING WAS LEFT ON ACFT AFTER WASHING. ACFT FORCED TO RETURN BECAUSE OF INSTRUMENTATION ANOMALIES.

Narrative: ACFT WAS BROUGHT TO THE WASH RACK FOR A WASH. THE VITAL AREAS; OR WHAT IS CALLED FOR ON PAPERWORK; WAS COVERED. THE ALTIMETER WAS COVERED WITH PROPER COVERING. THE ALTIMETER ON THE PLT SIDE WAS COVERED WITH A COVERING NOT UP TO SPECS. THE COVERING SPRING; OR OVAL SHAPED RING; WAS MISSING FROM THE COVERING FOR A LONG TIME. ALL OF THE EXISTING COVERINGS ARE DAMAGED IN SOME FORM OR ANOTHER. THERE WAS A VISIBLE WALK AROUND OF AIRPLANE; BUT NO OVAL SHAPED OBJECT WAS DISCOVERED. THE LONG USE OF INFERIOR MATERIAL HAS CAUSED SOME AWARENESS AND THE REPLACING OF INFERIOR EQUIP WILL PREVENT THIS FROM HAPPENING AGAIN.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE PROBE COVERS ARE INSTALLED ON THE PITOT STATIC PROBES AND ARE HELD ON WITH A SPRING LOCATED IN THE END OF THE PROBE THAT LOCKS THE COVER ON THE PROBE. THE COVERS ARE WORN AND SOME SPRINGS ARE MISSING BUT THE COVERS ARE STILL USED; SO A SPRING MISSING WOULD NOT BE NOTICED. THE RPTR STATED THE COVERS ARE JUST WORN OUT AND NEED REPLACEMENT. REPORTEDLY; IN THIS EVENT; THE COVER WAS REMOVED AND THE SPRING REMAINED ON THE PROBE; COVERING THE STATIC PORTS. THE AIRPLANE TOOK OFF AND CAME BACK RIGHT AWAY AND THE SPRING WAS DISCOVERED.SUPPLEMENTAL INFO FROM ACN 690434 REVEALED THE FOLLOWING INFO: DURING THE FLT; AIRSPD/ALT DIFFERENCE WAS NOTED BY THE CAPT BETWEEN HIS INSTRUMENTS AND THE FO'S. THE FO'S INSTRUMENTS CONCURRED WITH THE STAND-BY INSTRUMENTS.

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.