Narrative:

During postflt walkaround; noticed a chafed hydraulic line in right wheel well. Damage was from a grease zerk contacting tubing when gear was retracted. Installed a temporary repair by removing damaged section and replacing with a 12 inch long hose and unions per chapter 20. I cut the outboard end of the tube too long and when I unscrewed the b-nut from the union to shorten it; the threads appeared to gall; it would not loosen or tighten. The outboard line was cut to the correct length and a new union; sleeve and b-nut was installed and tightened. The inboard connection appeared to tighten correctly. The gear was pinned and a dummy retraction was accomplished as a leak/pressure check with no problems noted. The temporary repair was put on the open items list (oil) with replacement scheduled in a week. The inboard connection failed at the first gear retraction after takeoff; all 'a' system hydraulic fluid was lost. Aircraft returned to airport after declaring an emergency. The inboard connection failed because the sleeve had not set into the tube deeply enough to hold the pressure. The inboard union and b-nut were stainless steel; the outboard union was stainless and the b-nut was steel. The second outboard union installation seemed to tighten up further than the all stainless inboard union. My assumption is that the all stainless inboard fitting was galling and giving a false sense of tightening. This type of repair is a fairly regular event and I have not had one fail before. While the pressure to get the airplane airworthy during an unexpected hydraulic line repair did not influence me to rush the work; the routine nature these repairs had acquired may have led me to expect success without doublechking on small irregularities.

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Original NASA ASRS Text

Title: A B727-200 DECLARED AN EMER AFTER GEAR RETRACTION DUE TO LOSS OF 'A' SYS PRESSURE AND QUANTITY. CAUSED BY FAILURE OF AN INTERIM HYD LINE REPAIR.

Narrative: DURING POSTFLT WALKAROUND; NOTICED A CHAFED HYD LINE IN R WHEEL WELL. DAMAGE WAS FROM A GREASE ZERK CONTACTING TUBING WHEN GEAR WAS RETRACTED. INSTALLED A TEMPORARY REPAIR BY REMOVING DAMAGED SECTION AND REPLACING WITH A 12 INCH LONG HOSE AND UNIONS PER CHAPTER 20. I CUT THE OUTBOARD END OF THE TUBE TOO LONG AND WHEN I UNSCREWED THE B-NUT FROM THE UNION TO SHORTEN IT; THE THREADS APPEARED TO GALL; IT WOULD NOT LOOSEN OR TIGHTEN. THE OUTBOARD LINE WAS CUT TO THE CORRECT LENGTH AND A NEW UNION; SLEEVE AND B-NUT WAS INSTALLED AND TIGHTENED. THE INBOARD CONNECTION APPEARED TO TIGHTEN CORRECTLY. THE GEAR WAS PINNED AND A DUMMY RETRACTION WAS ACCOMPLISHED AS A LEAK/PRESSURE CHK WITH NO PROBS NOTED. THE TEMPORARY REPAIR WAS PUT ON THE OPEN ITEMS LIST (OIL) WITH REPLACEMENT SCHEDULED IN A WK. THE INBOARD CONNECTION FAILED AT THE FIRST GEAR RETRACTION AFTER TKOF; ALL 'A' SYS HYD FLUID WAS LOST. ACFT RETURNED TO ARPT AFTER DECLARING AN EMER. THE INBOARD CONNECTION FAILED BECAUSE THE SLEEVE HAD NOT SET INTO THE TUBE DEEPLY ENOUGH TO HOLD THE PRESSURE. THE INBOARD UNION AND B-NUT WERE STAINLESS STEEL; THE OUTBOARD UNION WAS STAINLESS AND THE B-NUT WAS STEEL. THE SECOND OUTBOARD UNION INSTALLATION SEEMED TO TIGHTEN UP FURTHER THAN THE ALL STAINLESS INBOARD UNION. MY ASSUMPTION IS THAT THE ALL STAINLESS INBOARD FITTING WAS GALLING AND GIVING A FALSE SENSE OF TIGHTENING. THIS TYPE OF REPAIR IS A FAIRLY REGULAR EVENT AND I HAVE NOT HAD ONE FAIL BEFORE. WHILE THE PRESSURE TO GET THE AIRPLANE AIRWORTHY DURING AN UNEXPECTED HYD LINE REPAIR DID NOT INFLUENCE ME TO RUSH THE WORK; THE ROUTINE NATURE THESE REPAIRS HAD ACQUIRED MAY HAVE LED ME TO EXPECT SUCCESS WITHOUT DOUBLECHKING ON SMALL IRREGULARITIES.

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.