# NTSB CHI08IA065: Boeing 737-2H4, N733TW, Lincoln, NE, January 8, 2008 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: January 8, 2008, 17:45 local (23:45 UTC) - Place: Lincoln, NE - Coordinates: 40.851387, -96.765274 - Nearby events: https://openairdocs.org/map.md?lat=40.8514&lon=-96.7653&mi=10 - Phase of flight: [Taxi](https://openairdocs.org/ntsb-phases/250) (OpenAirDocs' grouping) - Defining event: [Taxi-from runway: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: No injuries - Injuries: 38 uninjured - Status: Completed, report July 30, 2008 - Report: Approved by Office Director - Parties: Federal Aviation Administration - NTSB case key (mKey): 67416 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI08IA065 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/67416/pdf - Page: https://openairdocs.org/ntsb/CHI08IA065 ## 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. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Hydraulic power system](https://openairdocs.org/ntsb-findings/01022900): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Boeing 737-2H4, 1 case](https://openairdocs.org/ntsb-findings/01022900/cases.md?model=138448C), [All aircraft, 22 cases](https://openairdocs.org/ntsb-findings/01022900/cases.md) - [Terrain: wet/muddy terrain](https://openairdocs.org/ntsb-findings/03021035): Environmental issues › Physical environment · Not specified; cases with it: [Boeing 737-2H4, 1 case](https://openairdocs.org/ntsb-findings/03021035/cases.md?model=138448C), [All aircraft, 110 cases](https://openairdocs.org/ntsb-findings/03021035/cases.md) - [Action: incorrect action performance](https://openairdocs.org/ntsb-findings/02041015): Personnel issues › Action/decision · Maintenance personnel (probable cause); cases with it: [Boeing 737-2H4, 1 case](https://openairdocs.org/ntsb-findings/02041015/cases.md?model=138448C), [All aircraft, 1,386 cases](https://openairdocs.org/ntsb-findings/02041015/cases.md) - [Terrain: snowy/icy terrain](https://openairdocs.org/ntsb-findings/03021030): Environmental issues › Physical environment · Not specified; cases with it: [Boeing 737-2H4, 1 case](https://openairdocs.org/ntsb-findings/03021030/cases.md?model=138448C), [All aircraft, 77 cases](https://openairdocs.org/ntsb-findings/03021030/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Taxi-from runway: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Boeing 737-2H4, 1 case](https://openairdocs.org/ntsb-events/330/sequence.md?model=138448C), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) - [Taxi-from runway: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Boeing 737-2H4, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=138448C), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis 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. ## Factual narrative On January 8, 2008, about 1745 central standard time, N733TW, a Boeing 737-2H4, operated by Ameristar Air Cargo, Inc., sustained no damage when it lost directional control and exited the taxiway while taxiing from landing at the Lincoln Airport (LNK), near Lincoln, Nebraska. The non-scheduled domestic passenger flight was operating under 14 CFR Part 121. The airline transport rated pilot and co-pilot, 4 flight attendants, 1 jump seat occupant, and 31 passengers were uninjured after deplaning via the airplane's airstairs. Visual meteorological conditions prevailed at the time of the accident. The flight originated about 1559 from the Austin-Bergstrom International Airport, near Austin, Texas, and was destined for LNK. The operator reported that on January 6, 2008, the airplane was 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 one was removed and reinstalled. That maintenance was checked for leaks and the airplane was returned to service. 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. The captain, in part, stated: At about 12 miles from the airport with runway 36 insight and the airspeed at 210 knots started extending the flaps on schedule. When lowering the gear we performed the Before Landing Checklist and observed all systems normal upon completing the checklist and the flaps at 30 degrees. I landed on runway 36 in Lincoln, NE (LNK) with all systems normal and exited taxiway Juliet to the right per tower instructions. As I exited runway 36 I then stowed the speed brakes and called for the after landing checklist. ... While taxiing to parking ... the Master Caution "HYD" Light illuminated followed by an immediate loss of System "B" Hydraulics. I immediately started trying to get the airplane stopped and observed no braking and no response to tiller movement for nose wheel steering. I then tried to deploy the thrust reversers and couldn't get the [thrust reverser]'s to deploy. Within a few seconds after the loss of System B, we observed that a total loss of System "A" Hydraulics had occurred as well. In this very short time period the airplane started a slight turn to the left. I was applying the right rudder with no response in the steering. I then asked for assistance from [the] First Officer ... with the right rudder. The [a]irplane exited the taxiway to the left into the mud and snow. After coordinating with fire and rescue, I made the decision to use the aircraft stairs to deplane the passengers. Examination of the swivel valves after the incident revealed that both valves were not installed as depicted in the maintenance manual. ## Aircraft - Registration: [N733TW](https://openairdocs.org/deregistered/N733TW-2014-06-03), registration cancelled 2014-06-03, S/N 22732, built 1982 (OpenAirDocs) - Reported make and model: Boeing 737-2H4 - Registry model: [Boeing 737-2H4](https://openairdocs.org/model/boeing-737-2h4) (registry code 138448C) (OpenAirDocs) - Registry engine: [Pratt & Whitney JT8D-17 series](https://openairdocs.org/engine/pratt-whitney-jt8d-17-series) (registry code 52049, turbo-jet) (OpenAirDocs) - Category: Airplane - Serial number: 22732 - Airframe hours: 71959 - Engines: Pratt & Whitney JT8D-17 turbo fan; Pratt & Whitney JT8D-17 turbo fan - Damage: No damage - Flight: Part 121 - Operator: Ameristar Air Cargo, Inc. - Registered owner: Sierra American Corp - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, November 1, 2007 - Departed: AUS, AUSTIN, TX - Destination: Lincoln, NE - Flight plan: IFR - Airport: LNK, Lincoln Muni, runway 36, 12,901 × 200 ft, concrete ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; injuries: none; flight engineer, commercial, airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, unknown; seat: left; flight hours: 15,000 as pilot in command - Co-pilot; injuries: none; airline transport; airplane ratings: multi-engine land; medical: class 1, unknown; seat: right; flight hours: 3,380 in this make and model, 15,000 as pilot in command ## Weather - Conditions: Visual (VMC), Night - Wind: 280° at 6 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 37 °F, dew point 23 °F - Altimeter: 30.05 inHg - Observed at: LNK ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Incident 20080108000219I](https://openairdocs.org/incident/20080108000219I), Jan 8, 2008: Boeing 7372H4, Lincoln, NE, No damage. (-23) N733TW, B-737-2H4, operated by ameristar charters as flight AJI9262, departed the ramp area while taxiing to the terminal. Following an uneventful… From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.