Aircraft maintenance discrepancy eventually creates an unscheduled landing, aircraft damaged.

Attributes
ACN	252333
Time
Date	199309
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : den
State Reference	CO
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	ground : parked
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	other personnel other
Qualification	other other : other
ASRS Report	242333
Person 2
Affiliation	company : air carrier
Function	other personnel other
Qualification	other other : other
ASRS Report	252040
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa other other : unspecified
Resolutory Action	none taken : detected after the fact
Consequence	other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other
Situations
Publication	Unspecified

Narrative:

On evening of sep/xx/93 an medium large transport arrived den with PIREP of a loud noise and momentary vibration during flight. After landing, pilot also reported evidence of blue water leak and ice at forward lavatory service panel. Left engine was examined for damage. Very minor fan blade nicks (not consistent with ice ingestion) were noted and repaired, forward lavatory was leak checked in accordance with maintenance manual. No leaks were noted. On next revenue flight, the left engine ingested ice, presumably from forward lavatory service panel leak, and sustained massive damage. Flight was diverted to des moines where engine was replaced and lavatory leak repaired. Since no lavatory leakage was noted during normal leak check, I believe that lavatory tank valve failed during flight at differential pressure above 4 psi. Callback conversation with reporter revealed the following information: the aircraft, an medium large transport, was checked in accordance with the maintenance manual at the required 4 psi for leaks within the lavatory system. A follow-up on the aircraft maintenance history a few days later revealed that the aircraft was suffering from the same problem. At the air carrier maintenance base the check valve in the fill line was replaced, which corrected the problem. Apparently the liquid from the lavatory was siphoning back up through the faulty check valve in the fill line, thereby exhibiting the same symptoms as a primary leak. Supplemental information from acn 252040: forward lavatory was drained, svced and leak checked in accordance with maintenance manual. No leaks were noted at 4 pounds psi.

Original NASA ASRS Text

Title: ACFT MAINT DISCREPANCY EVENTUALLY CREATES AN UNSCHEDULED LNDG, ACFT DAMAGED.

Narrative: ON EVENING OF SEP/XX/93 AN MLG ARRIVED DEN WITH PIREP OF A LOUD NOISE AND MOMENTARY VIBRATION DURING FLT. AFTER LNDG, PLT ALSO RPTED EVIDENCE OF BLUE WATER LEAK AND ICE AT FORWARD LAVATORY SVC PANEL. L ENG WAS EXAMINED FOR DAMAGE. VERY MINOR FAN BLADE NICKS (NOT CONSISTENT WITH ICE INGESTION) WERE NOTED AND REPAIRED, FORWARD LAVATORY WAS LEAK CHKED IN ACCORDANCE WITH MAINT MANUAL. NO LEAKS WERE NOTED. ON NEXT REVENUE FLT, THE L ENG INGESTED ICE, PRESUMABLY FROM FORWARD LAVATORY SVC PANEL LEAK, AND SUSTAINED MASSIVE DAMAGE. FLT WAS DIVERTED TO DES MOINES WHERE ENG WAS REPLACED AND LAVATORY LEAK REPAIRED. SINCE NO LAVATORY LEAKAGE WAS NOTED DURING NORMAL LEAK CHK, I BELIEVE THAT LAVATORY TANK VALVE FAILED DURING FLT AT DIFFERENTIAL PRESSURE ABOVE 4 PSI. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE ACFT, AN MLG, WAS CHKED IN ACCORDANCE WITH THE MAINT MANUAL AT THE REQUIRED 4 PSI FOR LEAKS WITHIN THE LAVATORY SYS. A FOLLOW-UP ON THE ACFT MAINT HISTORY A FEW DAYS LATER REVEALED THAT THE ACFT WAS SUFFERING FROM THE SAME PROB. AT THE ACR MAINT BASE THE CHK VALVE IN THE FILL LINE WAS REPLACED, WHICH CORRECTED THE PROB. APPARENTLY THE LIQUID FROM THE LAVATORY WAS SIPHONING BACK UP THROUGH THE FAULTY CHK VALVE IN THE FILL LINE, THEREBY EXHIBITING THE SAME SYMPTOMS AS A PRIMARY LEAK. SUPPLEMENTAL INFO FROM ACN 252040: FORWARD LAVATORY WAS DRAINED, SVCED AND LEAK CHKED IN ACCORDANCE WITH MAINT MANUAL. NO LEAKS WERE NOTED AT 4 LBS PSI.

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.