# NTSB MIA91IA022: Aerospatiale ATR-42-300, N972NA, San Juan, PR, November 6, 1990

- Type: NTSB incident investigation
- Classification: Incident · No injuries · Incident investigation · Final report
- Date: November 6, 1990, 15:16 local (19:16 UTC)
- Place: San Juan, PR
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 44 uninjured
- Status: Completed, report August 6, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 32765
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MIA91IA022
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/32765/pdf
- Page: https://openairdocs.org/ntsb/MIA91IA022

## Probable cause

THE IMPROPER USE OF AILERON TRIM AND THE IMPROPER PREPARATION FOR AUTO PILOT DISCONNECT BY THE FLIGHT CREW COMBINED WITH EXCESSIVE FORCES APPLIED BY THE AILERON TRIM SYSTEM RESULTING IN A DEPARTURE FROM CONTROLLED FLIGHT. CONTRIBUTING FACTORS TO THE INCIDENT WERE INADEQUATE AND MISLEADING AUTOPILOT WARNINGS, LACK OF CONSPICUITY OF THE AILERON TRIM INDICATOR, LACK OF FAA REGULATION GOVERNING CONTROL AUTHORITY IN MISTRIM CONDITIONS, AUTOPILOT SYSTEM MASKING OF MISTRIM CONDITIONS, AND THE LACK OF FAA REQUIREMENT FOR RECURRENT PILOT TRAINING IN AUTOPILOT USE.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Loss of control - in flight, climb - to cruise
  - autopilot - information insufficient, manufacturer (contributing factor)
  - acft/equip,inadequate design, manufacturer (contributing factor)
  - insufficient standards/requirements,aircraft, faa(organization) (contributing factor)
  - aileron trim - improper use of, pilot in command (cause)
  - aileron trim - excessive (cause)
  - acft/equip,inadequate handling/perf capabilities, manufacturer (contributing factor)
  - insufficient standards/requirements,aircraft, faa(organization) (contributing factor)
  - autopilot - exceeded (cause)
  - autopilot - inadvertent deactivation (cause)
  - directional control - not maintained, pilot in command (cause)
- Altitude deviation,uncontrolled, climb - to cruise

## Analysis

PLT STATED AUTOPILOT ENGAGED AT 1,000 FEET AFTER T/O. AILERON TRIM WAS USED AFTER AUTOPILOT ENGAGEMENT. FLT WAS GIVEN HEADING CHANGE TO RT. AUTOPILOT HDG BUG DID NOT TURN A CFT. HE DISCONNECTED THE AUTOPILOT AT 2,200 FT AND THE ACFT IMMEDIATELY ROLLED INTO A LEFT 60 DEGREE BANK AND BEGAN DESCENDING. HE THEN ACTIVATED AILERON TRIM TO THE RT AND ALONG WITH THE COPILOT ON THE CONTROLS THEY RECOVERED. POST CRASH EXAMINATION OF THE ACFT STRUCTURE, FLT CONTROLS, AND AUTOPILOT SYSTEM REVEALED NO EVIDENCE TO INDICATE PREINCIDENT FAILURE OR MALFUNCTION OF THESE. THE DFDR AND RADAR DATA INDICATED THE EVENT OCCURRED AT 3,300 FEET AND THAT FOR 45 SECONDS BEFORE THE EVENT OCCURRED THE AILERONS WERE DEFLECTED TO THE RT 2 TO 5 DEGREES. AFTER THE DESCENDING LEFT TURN BEGAN PLTS DID NOT REDUCE POWER FOR 60 SECONDS AND ACFT SPEED EXCEEDED 250 KNOT VNE SPEED. AFTER THE INCIDENT THE ACFT MFG RESTRICTED USE OF THE AILERON TRIM TO 1 DOT WITH AUTOPILOT ENGAGED, NOT THREE DOTS AS HAD BEEN PREVIOUSLY ALLOWED.

## Aircraft

- Registration: N972NA (not matched to a registry record)
- Reported make and model: AEROSPATIALE ATR-42-300 (ATR 42-300)
- Category: Airplane
- Serial number: 023
- Engines: P&W PW-120 2100 horsepower turbo prop
- Damage: No damage
- Flight: Part 121
- Operator: Executive Air Charter, Inc., doing business as American Eagle
- Registered owner: Executive Air Charter, Inc
- Airworthiness certificate: Standard, Transport
- Destination: STX, ST. CROIX
- Flight plan: IFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 40; commercial, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; seat: left; flight hours: 19,813 total, 1,641 in this make and model, 73 in the last 30 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 100° at 8 knots
- Visibility: 15 statute miles
- Lowest ceiling: 25,000 ft broken
- Temperature: 90 °F, dew point 73 °F
- Altimeter: 29.00 inHg
- Observed at: SJU, 5 nm away

## 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 19901106055109I](https://openairdocs.org/incident/19901106055109I), Nov 6, 1990: Aerosp ATR42300, San Juan, Puerto Rico. Pilot had problem with heading control after departure. Disengaged autopilot and aircraft went into turn. Returned.

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.

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