2 mechanics installed a check valve backwards.

Attributes
ACN	253327
Time
Date	199310
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : elp
State Reference	TX
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	ground : preflight
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	other personnel other
Qualification	other other : other
ASRS Report	253327
Person 2
Affiliation	company : air carrier
Function	other personnel other
Qualification	other other : other
ASRS Report	253335
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	other flight crewa
Resolutory Action	other
Consequence	Other
Supplementary
Air Traffic Incident	other

Narrative:

On a routine service check of an medium large transport, mechanic found a hydraulic leak in right wheel well. Identing the leak was difficult in that a line had a pin hole which created a cloud of mist in the wheel well, making it extremely hard to see and breathe. Prior to identing the pin hole, the mechanic removed a check valve on the landing gear control valve to replace the o-ring, which appeared to be leaking (wet). He reinstalled the check valve and leak checked the area, which continued to create a mist. He proceeded to remove a hydraulic line to isolate the leak, replaced the rigid line with an interim flexible line and it leak checked good. The mechanic returned the aircraft to service. After the aircraft departed, the crew advised operations center via radio that the gear (all 3) failed to retract fully. The aircraft returned and landed without incident. Trouble-shooting the landing gear system revealed that the check valve previously removed had been re- installed backwards, limiting all 3 gear from fully retracting. The check valve was corrected and the aircraft gear worked properly. Supplemental information from acn 253335: the check valve in question is identical to a normal fitting and is not clearly marked. Due to conditions it would be very easy to install this valve backwards if not aware of it being a check valve.

Original NASA ASRS Text

Title: 2 MECHS INSTALLED A CHK VALVE BACKWARDS.

Narrative: ON A ROUTINE SVC CHK OF AN MLG, MECH FOUND A HYD LEAK IN R WHEEL WELL. IDENTING THE LEAK WAS DIFFICULT IN THAT A LINE HAD A PIN HOLE WHICH CREATED A CLOUD OF MIST IN THE WHEEL WELL, MAKING IT EXTREMELY HARD TO SEE AND BREATHE. PRIOR TO IDENTING THE PIN HOLE, THE MECH REMOVED A CHK VALVE ON THE LNDG GEAR CTL VALVE TO REPLACE THE O-RING, WHICH APPEARED TO BE LEAKING (WET). HE REINSTALLED THE CHK VALVE AND LEAK CHKED THE AREA, WHICH CONTINUED TO CREATE A MIST. HE PROCEEDED TO REMOVE A HYD LINE TO ISOLATE THE LEAK, REPLACED THE RIGID LINE WITH AN INTERIM FLEXIBLE LINE AND IT LEAK CHKED GOOD. THE MECH RETURNED THE ACFT TO SVC. AFTER THE ACFT DEPARTED, THE CREW ADVISED OPS CTR VIA RADIO THAT THE GEAR (ALL 3) FAILED TO RETRACT FULLY. THE ACFT RETURNED AND LANDED WITHOUT INCIDENT. TROUBLE-SHOOTING THE LNDG GEAR SYS REVEALED THAT THE CHK VALVE PREVIOUSLY REMOVED HAD BEEN RE- INSTALLED BACKWARDS, LIMITING ALL 3 GEAR FROM FULLY RETRACTING. THE CHK VALVE WAS CORRECTED AND THE ACFT GEAR WORKED PROPERLY. SUPPLEMENTAL INFO FROM ACN 253335: THE CHK VALVE IN QUESTION IS IDENTICAL TO A NORMAL FITTING AND IS NOT CLRLY MARKED. DUE TO CONDITIONS IT WOULD BE VERY EASY TO INSTALL THIS VALVE BACKWARDS IF NOT AWARE OF IT BEING A CHK VALVE.

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.