FROM: THE BOEING COMPANY
21-Sep-2005 16:44:36 US PACIFIC TIME
PRODUCT TYPE: Airplane
PRODUCT LINE: 737
PRODUCT: 737-400
ATA: 0230-00
PART NUMBER:
REFERENCES:
/A/ SR 1-111721075 Dated 10 Aug 2005
/B/ 737-300/400/500/600/700/800/900 Flight Crew Training Manual (FCTM), Page 8.30 , Situations Beyond the Scope of Non-Normal Checklists, Flight Path Control Dated 31 October 2004
SUBJECT: 737-400 PH-BTC Runway Excursion during Landing, Barcelona, Spain - 28 November 2004
Final Final Final Final
The Spanish Civil Aviation Accident and Incident Investigation Commission (CIAIAC) has investigated the subject accident with assistance from the Dutch Transportation Safety Board (TSB), the U.S. National Transportation Safety Board (NTSB), the Operator and Boeing. The CIAIAC has published their final report, which can be accessed on the following web site:
http://www.fomento.es/NR/rdonlyres/0..._070_A_ENG.pdf
The following is an extract from the report:
Quote
3.2. Causes
It is considered that the accident probably happened because during the takeoff a bird strike broke one of the cables of the nose wheel steering system of the aircraft and jammed the other, which made that the nose wheels were rotated to the left during landing, causing a veering to the left that could not be arrested by full rudder deflection as the aircraft decelerated. The subsequent application of brakes and other actions by the crew could not avoid that the aircraft went outside the runway surface.
The damages to the aircraft were increased by the condition of the runway strip due to the airport construction works.
Contributing to the breaking of the cable was the fact that it was severely worn locally. The wear could be traced back to the incorrect application of grease to the cable system during maintenance. Despite the training and experience of the flight crew, they were unable to quickly recognize the possible cause of the deviation of the aircraft and to keep the aircraft on the runway.
End quote
On page 73 of the report, there are two recommendations addressed to Boeing. These recommendations are repeated below with Boeing's responses.
Quote
Recommendation 20/05: It is recommended to The Boeing Company that a service information letter or similar document is sent to all the operators of Boeing 737 aircraft to make flight crews and maintenance personnel aware of the hazardous effects that a bird impact in the area of the NLG could have in the nose wheel steering system, and that precautionary measures should be taken in this case. This letter should also highlight the importance to strictly follow the instructions of document 737-FTD-32-03008 in order to avoid the wear of the NWS cables.
End quote
Boeing Response: Boeing has addressed the above recommendation in the following manner. The reference a) message was released to all 737 operators following the subject event. A copy of this message can be obtained from your local Boeing Field Service Representative or the Airline Support Manager(s) assigned to your airline.
Quote
Recommendation 21/05: It is recommended to The Boeing Company that supplementary training instructions are provided to operators of Boeing 737 to allow flight crews to quickly identify a possible NWS malfunction during landing and to advise them of the expected performance of the aircraft and of the measures that should be taken to avoid losing directional control at high speeds.
Endquote
Boeing Response: Boeing has addressed the above recommendation in the following manner. As detailed in the reference a) message, 737 operators were advised that bird strikes such as the one in the subject event can potentially damage and/or displace Nose Wheel Steering (NWS) cables, thus affecting the landing roll. After an event affecting NWS, the nose wheel may be deflected. The amount of deflection and its effect on directional control of the airplane on the ground depend on the nature of the failure. Similar exposure to un-commanded NWS deflection exists on other Boeing models. Therefore, operators are directed to the following guidance in heritage Boeing Flight Crew Training Manuals (FCTM), similar to the Reference b):
Situations Beyond the Scope of Non-Normal Checklists
"Aggressive differential braking and/or use of asymmetrical reverse thrust, in addition to other control inputs, may be required to maintain directional control."
Boeing believes this general guidance is the only sound instruction and training advice that can be provided to crews to accommodate demanding situations that require the use of various controls to prevent drift and possible runway excursion. These situations include but are not limited to blown tires, collapsed main landing gear, strong crosswinds on dry runways, thrust reverser anomalies, icy patches on runways, seized brakes and nose wheel steering anomalies including jammed steering metering valves and the kind associated with the subject accident.
R. S. Breuhaus, Chief Engineer, Air Safety Investigation BOEING