Individually Owned: 150,657
Corporate Owned: 137,281
Aircraft Accident/Incident Report
Aliquippa, Pennsylvania 15001
Thursday, September 8, 1994 19:03 EDT
NTSB Narrative Summary Released at Completion of Accident
The airplane crashed while maneuvering to land at Pittsburgh International Airport. The airplane entered an uncontrolled descent and impacted terrain about 6 miles east of the airport. The airplane struck the ground at an angle of descent of about 80 degrees, in a slight roll to the left, and the airspeed was about 260 knots at impact. The investigation revealed that during the accident sequence, the airplane rudder deflected rapidly to the left and reached its left aerodynamic blowdown limit shortly thereafter. Examination of the rudder system revealed that it is possible, in the main rudder power control unit (PCU) of the airplane (as a result of some combination of tight clearances within the servo valve, thermal effects, particulate matter in the hydraulic fluid, or other unknown factors), the servo valve secondary slide could jam to the servo valve housing at a position offset from its neutral position without leaving any obvious physical evidence and that, combined with rudder pedal input, could have caused the rudder to move opposite to the direction commanded by a rudder pedal input. This condition of the PCU was also consistent with analysis of the cockpit voice recorder, computer simulation, and human performance data, including operational factors
NTSB Probable Cause Narrative
A loss of control of the airplane resulting from the movement of the rudder surface to its blowdown limit. The rudder surface most likely deflected in a direction opposite to that commanded by the pilots as a result of a jam of the main rudder power control unit servo valve secondary slide to the servo valve housing offset from its neutral position and overtravel of the primary slide.
Event Information
| Type of Event | Accident |
| Event Date | 9/8/1994 |
| Event Day of the Week | Thursday |
| Time of Event | 1903 |
| Event Time Zone | Eastern Daylight Time |
| Event City | ALIQUIPPA |
| Event State | PENNSYLVANIA |
| Event Country | -- |
| Zipcode of the event site | 15001 |
| Event Date Year | 1994 |
| Event Date Month | 9 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | -- |
| Event Location Longitude | -- |
| Event Location Airport | |
| Event Location Nearest Airport ID | |
| Indicates whether the acc/inc occurred off or on an airport | Off Airport/Airstrip |
| Distance from airport in statute miles | 6 |
| Degrees magnetic from airport | 320 |
| Airport Elevation | -- |
| Weather Briefing Completeness | Not pertinent |
| Investigator's weather source | Witness |
| Time of the weather observation | 0 |
| Direction of event from weather observation facility (degrees) | 0 |
| Weather Observation Facility ID | |
| Elevation of weather observation facility | 0 |
| Distance of event from weather observation facility (units?) | 0 |
| Time Zone of the weather observation | |
| Lighting Conditions | Day |
| Lowest Ceiling Height | 0 |
| Lowest Non-Ceiling Height | 8000 |
| Sky/Lowest/Cloud Conditions | Scattered |
| Sky Condition for Lowest Ceiling | Unknown |
| Visibility Runway Visual Range (Feet) | 0 |
| Visibility Runway Visual Value (Statute Miles) | 0 |
| Visibility (Statute Miles) | 15 |
| Air Temperature at event time (in degrees celsius) | 23 |
| Dew Point at event time (in degress fahrenheit) | 11 |
| Wind Direction (degrees magnetic) | 0 |
| Variable Wind Indicator | Variable |
| Wind Speed (knots) | 0 |
| Wind Velocity Indicator | Light and Variable |
| Wind Gust Indicator | Not Gusting |
| Wind Gust (knots) | 0 |
| Altimeter Setting at event time (in. Hg) | 30 |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | Unknown |
| METAR weather report | -- |
| Event Highest Injury | Fatal |
| On Ground, Fatal Injuries | 0 |
| On Ground, Minor Injuries | 0 |
| On Ground, Serious Injuries | 0 |
| Injury Total Fatal | 132 |
| Injury Total Minor | -- |
| Injury Total None | -- |
| Injury Total Serious | -- |
| Injury Total All | 132 |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 2066 |
| NTSB Notification Source | -- |
| NTSB Notification Date | Sep 8 1994 12:00AM |
| NTSB Notification Time | 1930 |
| Fiche Number and/or location -used to find docket information | IMAGE |
| Date of most recent change to record | Nov 26 2002 1:12PM |
| User who most recently changed record | NTSB\ZUZL |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N513AU |
| NTSB Number | DCA94MA076 |
| Missing Aircraft Indicator | N |
| Federal Aviation Reg. Part | Part 121: Air Carrier |
| Type of Flight Plan filed | IFR |
| Flight plan Was Activated? | -- |
| Damage | Destroyed |
| Aircraft Fire | Ground |
| Aircraft Explosion | Ground |
| Aircraft Manufacturer's Full Name | BOEING |
| Aircraft Model | B-737-300 |
| Aircraft Series Identifier | B-737-300 |
| Aircraft Serial Number | 24549 |
| Certified Max Gross Weight | 142500 |
| Aircraft Category | Airplane |
| Aircraft Registration Class | U.S. Registered/U.S. Soil |
| Aircraft is a homebuilt? | No |
| Flight Crew Seats | -- |
| Cabin Crew Seats | -- |
| Passenger Seats | -- |
| Total number of seats on the aircraft | 142 |
| Number of Engines | 2 |
| Fixed gear or retractable gear | Retractable |
| Aircraft, Type of Last Inspection | Continuous Airworthiness |
| Date of Last Inspection | Aug 8 1994 12:00AM |
| Airframe hours since last inspection | 274 |
| Airframe Hours | 23846 |
| ELT Installed | No |
| ELT Activated | Unknown |
| ELT Aided Location of Event Site | Unknown |
| ELT Type | -- |
| Aircraft Owner Name | USAIR |
| Aircraft Owner Street Address | 2345 CRYSTAL DRIVE |
| Aircraft Owner City | ARLINGTON |
| Aircraft Owner State | VA |
| Aircraft Owner Country | |
| Aircraft Owner Zipcode | 22227 |
| Operator is an individual? | -- |
| Operator Name | USAIR |
| Operator Same as Owner? | No |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | No |
| Operator Street Address | PITTSBURGH INT'L AIRPORT |
| Operator City | PITTSBURGH |
| Operator State | PA |
| Operator Country | |
| Operator Zip code | 15231 |
| Operator Code | AL |
| Owner has at least one certificate | Yes - certificate holder |
| Other Operator of large aircraft? | No |
| Certified for Part 133 or 137 Operation | Unknown |
| 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) | Unknown |
| Second Pilot on Board | Yes |
| Departure Point Same as Event | No |
| Departure Airport Code | ORD |
| Departure City | CHICAGO |
| Departure State | IL |
| Departure Country | |
| Departure Time | 1830 |
| Departure Time Zone | CDT |
| Destination Same as Local Flt | -- |
| Destination Airport Code | PIT |
| Destination City | PITTSBURG |
| Destination State | PA |
| Destination Country | |
| Specific Phase of Flight | Approach |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Jan 2 2001 10:30AM |
| User who most recently changed record | dbo |
| Since inspection or accident | -- |
| Event Location Runway Number and Location | 0 |
| Runway Length | -- |
| Runway Width | -- |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |