Aircraft Accident/Incident Report

Paraburdoo American Samoa
Tuesady, February 28, 2006 8:55 YST

NTSB Narrative Summary Released at Completion of Accident

On February 28, 2006, about 0855 western standard coordinated time, a Boeing 717-200, Australian registration VH-NXH, operated by National Jet, experienced erroneous airspeed indications and stick shaker activation while in cruise flight about 122 miles south of Paraburdoo, Western Australia. There were no injuries to 2 certificated pilots, 4 flight attendants, and 66 passengers. Night instrument meteorological conditions prevailed for the flight that departed from Paraburdoo, about 0000, destined for Perth. An instrument flight rules flight plan was filed for the scheduled domestic flight. According to an interim factual report issued by the Australian Transport Safety Bureau, the weather conditions for the flight were under the influence of a decaying tropical cyclone that had crossed the northwest coast of Western Australia earlier that day. Rain and heavy cloud conditions persisted through most of the region. The meteorological forecast indicated a temperature of -39 degrees Celsius at the airplane's planned cruise altitude. The flight crew had selected the engines anti-ice system "ON" during the climb. The autopilot was engaged and had captured the planned cruise altitude of FL340. The airspeed, body angle, and engine power settings were normal for that stage of flight and the airplane was accelerating normally to cruise speed. During that period, the flight crew detected that, over several seconds, the speed displayed on the primary flight display (PFD) for stick shaker activation (Vss) began converging towards the current indicated airspeed. The speed indicated for Vss appeared to overtake the amber caution foot associated with the flight management computer (FMC) calculated minimum operating speed (Vmin), which appeared to be remaining stationary, rather than moving in conjunction with the Vss indication. The stick shaker warning activated as Vss merged with the current airspeed and then continued to increase and merge with the maximum operating speed (Vmo/Mmo). The right edge of the airspeed tape gave the appearance of one continuous red chevron "zipper." Similar indications were observed on both pilots' PFDs. The flight crew reported that they did not receive any other cautions, alerts, or warnings on the airplane's engine and alert display. The flight crew recalled that, although the pitch limit indicator had turned red, indicating that the airplane was at or near a stalled condition, there was no "STALL" annunciation on the PFD, nor any aural "STALL STALL" warning or klaxon alert. The flight crew initiated an immediate on-track descent and advised air traffic services (ATS) of their requirement to change altitude. The stick pusher stall recovery system did not activate and the flight crew did not identify any secondary indications of an impeding stall, such as aerodynamic buffet or an abnormally high pitch attitude. Although the flight crew did not detect any evidence of airframe ice on the windscreen or windscreen wiper posts, they selected the airframe anti-ice "ON." They did not otherwise change the configuration of the airplane. The stick shaker continued to operate as the airplane was descending approximately 2,000 feet per minute. The flight crew recalled that the speed indicated on the PFD for Vss returned to normal as the airplane descended through FL290 and that the stick shaker warning ceased at that time. The flight crew leveled the airplane at FL280 with all of the airplane's controls and system indications "normal." Once the in-flight weather conditions improved, the airplane was returned to FL300, and the flight landed at Perth without further incident. The operator's maintenance engineers performed a built-in test equipment check following the airplane's arrival in Perth. The check confirmed that no faults had been recorded during the occurrence flight and the airplane was released for service. Subsequent flights were completed without incident. The airplane's flight data recorder (FDR) and the electronic recording media for the quick access recorder (QAR) were removed for analysis. Data was also recovered from the non-volatile memory of the airplane's flight control computers (FCC). The FDR data indicated that the output from each of the airplane's angle of attack (AoA) sensors became static (continuously indicating about 4 degrees AoA) passing FL287 on climb, at a total indicated air temperature (TAT) of -4 degrees Celsius. The stick shaker activated approximately 80 seconds after the airplane had reached FL340, as it was accelerating through a computed airspeed of 258 knots and at a TAT of -10 degrees Celsius. About 14 seconds later the recorded data indicated the commencement of a descent from FL340. The stick shaker indication continued for another 2 minutes 23 seconds, ceasing as the airplane passed FL288, at a computed airspeed of 308 knots and a TAT of approximately +7 degrees Celsius. Associated with the cessation of the stick shaker warning were the AoA sensors returning to normal operation. The QAR media was found to contain no recorded data. Examination of that file indicated that the recording media was incorrectly formatted for use in the QAR. The manufacturer of the airplane's FCC analyzed the contents of each computer's non-volatile memory. That analysis revealed no fault history data for the day of the incident. On March 3, 2006, an entry was made in the airplane's maintenance log, reporting the intermittent operation of the air data heat switch annunciator after the system was selected "OFF" following landing. An indicating globe was replaced and the switch tested serviceable before the airplane was returned to service. The airplane's AoA sensors and air data heat switch were subsequently removed from the airplane and dispatched for examination by the component manufacturers under the direct supervision of the U.S. National Transportation Safety Board (NTSB). The incident is under the jurisdiction of, and is being investigated by, the Australian Transport Safety Bureau. Further information can be obtained from: Australian Transport Safety Bureau 15 Mort Street, Braddon ACT 2612, Australia P.O. Box 967, Civic Square ACT 2608, Australia Phone +61 2 6230 4408 Fax +61 2 6274 6434 Web site www.atsb.gov.au

NTSB Probable Cause Narrative

Not Yet Reported

Event Information

Type of Event Incident
Event Date 2/28/2006
Event Day of the Week Tuesday
Time of Event 855
Event Time Zone Yukon Standard Time
Event City Paraburdoo
Event State --
Event Country AMERICAN SAMOA
Zipcode of the event site --
Event Date Year 2006
Event Date Month 2
MidAir Collision Indicator No
On Ground Collision occurred ? No
Event Location Latitude 263230S
Event Location Longitude 1170520E
Event Location Airport --
Event Location Nearest Airport ID --
Indicates whether the acc/inc occurred off or on an airport --
Distance from airport in statute miles --
Degrees magnetic from airport --
Airport Elevation --
Weather Briefing Completeness --
Investigator's weather source Pilot
Time of the weather observation
Direction of event from weather observation facility (degrees) --
Weather Observation Facility ID --
Elevation of weather observation facility --
Distance of event from weather observation facility (units?) --
Time Zone of the weather observation --
Lighting Conditions --
Lowest Ceiling Height --
Lowest Non-Ceiling Height --
Sky/Lowest/Cloud Conditions --
Sky Condition for Lowest Ceiling --
Visibility Runway Visual Range (Feet) --
Visibility Runway Visual Value (Statute Miles) --
Visibility (Statute Miles) --
Air Temperature at event time (in degrees celsius) --
Dew Point at event time (in degress fahrenheit) --
Wind Direction (degrees magnetic) --
Variable Wind Indicator --
Wind Speed (knots) --
Wind Velocity Indicator --
Wind Gust Indicator --
Wind Gust (knots) --
Altimeter Setting at event time (in. Hg) --
Density Altitude (feet) --
Intensity of Precipitation --
METAR weather report --
Event Highest Injury None
On Ground, Fatal Injuries --
On Ground, Minor Injuries --
On Ground, Serious Injuries --
Injury Total Fatal --
Injury Total Minor --
Injury Total None 72
Injury Total Serious --
Injury Total All --
Investigating Agency Foreign
NTSB Docket Number (internal use) --
NTSB Notification Source ATSB
NTSB Notification Date Mar 9 2006 12:00AM
NTSB Notification Time --
Fiche Number and/or location -used to find docket information --
Date of most recent change to record Aug 8 2006 1:02PM
User who most recently changed record MUZD
Basic weather conditions Instrument Meteorological Cond
FAA District Office --

Aircraft Involved

Aircraft #1

Aircraft Registration Number --
NTSB Number DCA06WA028
Missing Aircraft Indicator --
Federal Aviation Reg. Part Part 129: Foreign
Type of Flight Plan filed IFR
Flight plan Was Activated? Yes
Damage None
Aircraft Fire --
Aircraft Explosion --
Aircraft Manufacturer's Full Name Boeing
Aircraft Model 717-200
Aircraft Series Identifier --
Aircraft Serial Number --
Certified Max Gross Weight --
Aircraft Category Airplane
Aircraft Registration Class --
Aircraft is a homebuilt? No
Flight Crew Seats --
Cabin Crew Seats --
Passenger Seats --
Total number of seats on the aircraft --
Number of Engines --
Fixed gear or retractable gear Fixed
Aircraft, Type of Last Inspection --
Date of Last Inspection --
Airframe hours since last inspection --
Airframe Hours --
ELT Installed --
ELT Activated --
ELT Aided Location of Event Site --
ELT Type --
Aircraft Owner Name --
Aircraft Owner Street Address --
Aircraft Owner City --
Aircraft Owner State --
Aircraft Owner Country --
Aircraft Owner Zipcode --
Operator is an individual? --
Operator Name --
Operator Same as Owner? --
Operator Is Doing Business As --
Operator Address Same as Owner? --
Operator Street Address --
Operator City --
Operator State --
Operator Country --
Operator Zip code --
Operator Code --
Owner has at least one certificate None
Other Operator of large aircraft? --
Certified for Part 133 or 137 Operation --
Operator Certificate Number --
Indicates whether an air carrier operation was scheduled or not Scheduled
Indicates Domestic or International Flight Domestic
Operator carrying Pax/Cargo/Mail Passenger Only
Type of Flying (Per_Bus / Primary) --
Second Pilot on Board --
Departure Point Same as Event No
Departure Airport Code YPBO
Departure City Paraburdoo
Departure State --
Departure Country --
Departure Time 0
Departure Time Zone UTC
Destination Same as Local Flt --
Destination Airport Code YPER
Destination City Perth
Destination State --
Destination Country --
Specific Phase of Flight Cruise - normal
Report sent to ICAO? --
Evacuation occurred --
Date of most recent change to record Aug 8 2006 1:02PM
User who most recently changed record MUZD
Since inspection or accident --
Event Location Runway Number and Location --
Runway Length --
Runway Width --
Sight Seeing flight No
Air Medical Flight No
Medical Flight --