Aerospatiale ATR-42-300 N972NA

Summary

On 6 November 1990 at about 19:16 local time, a Aerospatiale ATR-42-300 registered N972NA, operated by Executive Air Charter, Inc., was involved in an incident near San Juan. 44 people were on board and nobody was injured. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

6 November 1990 at 19:16

Classification

Incident

Location

San Juan

Coordinates

Not recorded

Aircraft

Aerospatiale ATR-42-300

Registration

N972NA

Category

Airplane

Engines

2

Operator

Executive Air Charter, Inc.

Operating rule

Part 121: Air Carrier

Purpose of flight

Unknown

Phase of flight

Not recorded

Route

Unknown → St. Croix

Aircraft damage

Not recorded

Weather

VMC

Light

Day

NTSB number

MIA91IA022

Nobody was injured.

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.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

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.

Quoted verbatim from the NTSB record.