# NTSB MIA95IA194: Boeing 737-3B7, N396US, Charlotte, NC, August 5, 1995 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: August 5, 1995, 10:00 local (14:00 UTC) - Place: Charlotte, NC - Coordinates: 35.230491, -80.91072 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=35.2305&lon=-80.9107&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 83 uninjured - Status: Completed, report September 3, 1996 - Report: Approved by Office Director - NTSB case key (mKey): 37678 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MIA95IA194 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/37678/pdf - Page: https://openairdocs.org/ntsb/MIA95IA194 ## Probable cause IMPROPER INSTALLATION OF THE 'A' SYSTEM FLIGHT CONTROL COMPUTER BY COMPANY MAINTENANCE PERSONNEL, WHICH RESULTED IN PIN CONNECTOR(S) BEING PUSHED LOOSE AND SUBSEQUENT MALFUNCTION OF THE AUTOPILOT. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, descent - maintenance,installation - improper, company maintenance personnel (cause) - automatic flight control system (afcs) - loose part/bolt/nut/clamp/etc (cause) - autopilot/flight director - malfunction (cause) ## Analysis THE CAPTAIN REPORTED THAT DURING DESCENT THROUGH 12,000 FEET WITH THE 'A' SYSTEM AUTOPILOT ENGAGED AND WITH AN AIRSPEED OF 250 KNOTS, THERE WAS AN UNCOMMANDED ROLL TO THE LEFT. HE DISENGAGED THE AUTOPILOT AND ROLLED THE THE AIRPLANE TO WINGS LEVEL FLIGHT, THEN CONTINUED THE FLIGHT WITH THE AUTOPILOT OFF. POSTINCIDENT EXAMINATION OF THE AIRCRAFT REVEALED AN INTERMITTENT ELECTRICAL CONNECTION IN AN 'A' AUTOPILOT CIRCUIT, DUE TO PIN CONNECTOR(S) BEING PUSHED OUT OF PLACE ON THE FLIGHT CONTROL COMPUTER SHELF CONNECTOR. ONE OF THE PINS WAS IN THE AILERON POSITION SENSOR EXCITATION CIRCUIT. THE 'A' FLIGHT CONTROL COMPUTER HAD BEEN REMOVED AND REINSTALLED THE DAY BEFORE THE INCIDENT TO INSPECT THE RACK FOR FLUID CONTAMINATION. ## Factual narrative On August 5, 1995, about 1000 eastern daylight time, a Boeing 737-3B7, N396US, operated by USAir, Inc., as flight 7, a 14 CFR Part 121 domestic passenger flight from Albany, New York, to Charlotte, North Carolina, had an uncommanded roll to the left while descending to land at Charlotte. Visual meteorological conditions prevailed at the time and an instrument flight rules flight plan was filed. The aircraft was not damaged and the airline transport-rated pilot, first officer, 3 flight attendants, and 78 passengers were not injured. The flight originated from Albany, New York, on August 5, 1995, about 0833. The captain stated that during descent through 12,000 feet at 250 knots airspeed, the "A" autopilot system was on LNAV and level change. The aircraft shuttered and then rolled to the left to a 30-degree bank angle. He disengaged the autopilot and rolled the aircraft level. The flight was continued with the autopilot off. Postincident investigation revealed the "LO" side of the roll sensor excitation from the "A" autopilot system flight control computer (FCC) to the "A" aileron autopilot actuator LVDT and "A" airleron postion sensor was intermittently open due to a socket pushed out of the locked position in the connector. Intermittent contact of this socket with its pin in the connector could cause airplane roll oscillations. The "A" system FCC had been removed and reinstalled the day before the incident to inspect the connectors for contamination. See attached Boeing Commercial Airplane Company report. ## Aircraft - Registration: [N396US](https://openairdocs.org/deregistered/N396US-2006-04-27), registration cancelled 2006-04-27, S/N 23318, built 1986 (OpenAirDocs) - Reported make and model: Boeing 737-3B7 - Registry model: [Boeing 737-3B7](https://openairdocs.org/model/boeing-737-3b7) (registry code 138447F) (OpenAirDocs) - Registry engine: [Amateur-built UNKNOWN ENG](https://openairdocs.org/engine/amateur-built-unknown-eng) (registry code 99999) (OpenAirDocs) - Category: Airplane - Serial number: 23318 - Airframe hours: 27857 - Engines: GE CFM56-3 22000 lbs thrust turbo fan - Damage: No damage - Flight: Part 121 - Operator: Usair - Registered owner: Society National Bank - Airworthiness certificate: Standard, Transport - Last inspection: AAIP, August 5, 1995, 11 hours before - Departed: ALB, ALBANY, NY - Destination: CLT - Flight plan: IFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 40; airline transport, flight engineer, flight instructor; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 11,300 total, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 230° at 6 knots - Visibility: 7 statute miles - Lowest ceiling: 2,700 ft overcast - Temperature: 75 °F, dew point 72 °F - Altimeter: 30.00 inHg - Observed at: CLT, 40 nm away 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.