Serious incident Boeing 737-2H4 N733TW,
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ASN Wikibase Occurrence # 998
 
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Date:Tuesday 8 January 2008
Time:17:45 LT
Type:Silhouette image of generic B732 model; specific model in this crash may look slightly different    
Boeing 737-2H4
Owner/operator:Ameristar Jet Charter
Registration: N733TW
MSN: 22732/877
Total airframe hrs:71959 hours
Engine model:Pratt & Whitney JT8D-17
Fatalities:Fatalities: 0 / Occupants: 38
Aircraft damage: None
Category:Serious incident
Location:Lincoln Municipal Airport, NE (LNK/KLNK) -   United States of America
Phase: Taxi
Nature:Passenger - Non-Scheduled/charter/Air Taxi
Departure airport:Austin-Bergstrom International Airport, TX (AUS/KAUS)
Destination airport:Lincoln Municipal Airport, NE (LNK/KLNK)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
A Boeing 737-2H4, operated by Ameristar Jet Charter, sustained no damage when it lost directional control and exited the taxiway on taxiing from landing at the Lincoln Airport (LNK), Nebraska.

Two days before the incident flight, the airplane was placed in maintenance for a "[Left/Hand Main Landing Gear] swivel valve leaking." The corrective action was accomplished by one of the operator's mechanics. The mechanic reportedly removed both the swivel valves on the left main landing gear. The aft swivel valve was removed and replaced with a new valve. The forward valve was removed and reinstalled. That valve was checked for leaks and the airplane was returned to service prior to the incident flight. The airplane, on a non-scheduled domestic passenger flight, was taxiing after landing, exited the taxiway, and became stuck in snow and mud despite the pilot's attempts to maintain directional control. The captain reported a total loss of all hydraulic systems. The airplane's maintenance manual 32-41-61 contained a warning that stated, "WARNING: MAKE SURE THAT THE SWIVEL JOINT AND HYDRAULIC LINES ARE ORIENTED AS SHOWN ... . THE HYDRAULIC LINE TO THE BRAKE ASSEMBLY MUST BE CONNECTED TO THE SWIVEL HOUSING AND THE HYDRAULIC LINE FROM THE ANTI-SKID VALVE TO THE SWIVEL FITTING AS SHOWN ... . IF THE ASSEMBLY OF THE SWIVEL AND THE HYDRAULIC LINES ARE ROTATED 180 DEGREES, THE HYDRAULIC LINES CAN BE CONNECTED BUT THE SWIVEL WILL NOT OPERATE. THIS CAN CAUSE THE HYDRAULIC LINES TO BREAK DURING EXTENSION AND RETRACTION AND CAUSE THE BRAKES PRESSURE TO BE LOST." Examination of the swivel valves after the incident revealed that both valves were not installed as depicted in the maintenance manual.

Probable Cause: The improper installation of the swivel valve fittings by the operator's mechanic leading to the total loss of both hydraulic systems. Contributing to the incident were the swivel valves leaking and the total failure of the hydraulic system.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: CHI08IA065
Status: Investigation completed
Duration: 6 months
Download report: Final report

Sources:

NTSB CHI08IA065

Location

Revision history:

Date/timeContributorUpdates
25-Jan-2008 04:07 JINX Added
21-Dec-2016 19:13 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
21-Dec-2016 19:14 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
21-Dec-2016 19:16 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
21-Dec-2016 19:20 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]

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