Narrative:
Embraer 120 N33701 was pulled into the Continental Express hangar at Houston around 21:30 for scheduled maintenance which included removal and replacement of both left and right hand horizontal stabilizer deice boots. The second shift mechanics started working on the right hand deice boot. Although planned for the third shift, the 47 screws from the top of the left leading edge assembly for the horizontal stabilizer were already removed by the second shift. The third shift mechanics finished the replacement of the right hand deice boot but did not have time to replace the left hand boot as well.
The first flight was a 07:00 scheduled flight from Houston to Laredo.
Flight 2574 departed Laredo for the return leg to Houston at 09:09. The cruise portion of the flight was uneventful and at 10:03 the aircraft was descending through 11800 feet to 9000 feet when the air loads caused the left horizontal stabilizer leading edge to bend downward and separate. A sudden severe nose down pitchover occurred and the wings stalled negatively. A negative g of 3.5 was recorded by the FDR. Eyewitnesses reported a bright flash and saw the aircraft breaking up while descending in a flat left spin until impact.
PROBABLE CAUSE: "The failure of Continental Express maintenance and inspection personnel to adhere to proper maintenance and quality assurance procedures for the airplane's horizontal stabilizer deice boots that led to the sudden in-flight loss of the partially secured left horizontal stabilizer leading edge and the immediate severe nose-down pitchover and breakup of the airplane. Contributing to the cause of the accident was the failure of the Continental Express management to ensure compliance with the approved maintenance procedures, and the failure of FAA surveillance to detect and verify compliance with approved procedures."
NTSB board member John K. Lauber filed a dissenting statement on the investigation report, believing the probable cause should read as follows:
"1) The failure of Continental Express management to establish a corporate culture which encouraged and enforced adherence to approved maintenance and quality assurance procedures, and 2) the consequent string of failures by Continental Express maintenance and inspection personnel to follow approved procedures for the replacement of the horizontal stabilizer deice boots. Contributing to the accident was the inadequate surveillance by the FAA of the Continental Express maintenance and quality assurance programs."
Wing failure
Loss of control
» Air Safety Week 4 January 1993 (p. 4)
» Flight International 18-24 September 91
» ICAO Adrep Summary 1/95
» NTSB/AAR-92/04
accident date: 11-09-1991
type: Embraer EMB-120RT Brasilia
registration: N33701
| Status: | Accident investigation report completed and information captured |
| Date: | Wednesday 11 September 1991 |
| Time: | 10:03 |
| Type: |  Embraer EMB-120RT Brasilia |
| Operated by: | Britt Airways |
| On behalf of: | Continental Express |
| Registration: | N33701 |
| MSN: | 120077 |
| First flight: | 1987 |
| Total airframe hrs: | 7229 |
| Cycles: | 10009 |
| Engines: | 2 Pratt & Whitney Canada PW123 |
| Crew: | Fatalities: 3 / Occupants: 3 |
| Passengers: | Fatalities: 11 / Occupants: 11 |
| Total: | Fatalities: 14 / Occupants: 14 |
| Aircraft damage: | Destroyed |
| Aircraft fate: | Written off (damaged beyond repair) |
| Location: | Eagle Lake, TX ( United States of America)
|
| Phase: | En route (ENR) |
| Nature: | Domestic Scheduled Passenger |
| Departure airport: | Laredo International Airport, TX (LRD/KLRD), United States of America |
| Houston-Intercontinental Airport, TX (IAH/KIAH), United States of America | |
| Flightnumber: | 2574 |
Embraer 120 N33701 was pulled into the Continental Express hangar at Houston around 21:30 for scheduled maintenance which included removal and replacement of both left and right hand horizontal stabilizer deice boots. The second shift mechanics started working on the right hand deice boot. Although planned for the third shift, the 47 screws from the top of the left leading edge assembly for the horizontal stabilizer were already removed by the second shift. The third shift mechanics finished the replacement of the right hand deice boot but did not have time to replace the left hand boot as well.
The first flight was a 07:00 scheduled flight from Houston to Laredo.
Flight 2574 departed Laredo for the return leg to Houston at 09:09. The cruise portion of the flight was uneventful and at 10:03 the aircraft was descending through 11800 feet to 9000 feet when the air loads caused the left horizontal stabilizer leading edge to bend downward and separate. A sudden severe nose down pitchover occurred and the wings stalled negatively. A negative g of 3.5 was recorded by the FDR. Eyewitnesses reported a bright flash and saw the aircraft breaking up while descending in a flat left spin until impact.
Probable Cause:
PROBABLE CAUSE: "The failure of Continental Express maintenance and inspection personnel to adhere to proper maintenance and quality assurance procedures for the airplane's horizontal stabilizer deice boots that led to the sudden in-flight loss of the partially secured left horizontal stabilizer leading edge and the immediate severe nose-down pitchover and breakup of the airplane. Contributing to the cause of the accident was the failure of the Continental Express management to ensure compliance with the approved maintenance procedures, and the failure of FAA surveillance to detect and verify compliance with approved procedures."
NTSB board member John K. Lauber filed a dissenting statement on the investigation report, believing the probable cause should read as follows:
"1) The failure of Continental Express management to establish a corporate culture which encouraged and enforced adherence to approved maintenance and quality assurance procedures, and 2) the consequent string of failures by Continental Express maintenance and inspection personnel to follow approved procedures for the replacement of the horizontal stabilizer deice boots. Contributing to the accident was the inadequate surveillance by the FAA of the Continental Express maintenance and quality assurance programs."
Accident investigation:
 |
|
Classification:
Wing failure
Loss of control
Sources:
» NTSB Safety Recommendations A-92-79 and -80» Air Safety Week 4 January 1993 (p. 4)
» Flight International 18-24 September 91
» ICAO Adrep Summary 1/95
» NTSB/AAR-92/04
Follow-up / safety actions
NTSB issued 4 Safety Recommendations
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Photos
accident date: 11-09-1991
type: Embraer EMB-120RT Brasilia
registration: N33701
Map
This map shows the airport of departure and the intended destination of the flight. The line between the airports does not display the exact flight path.
Distance from Laredo International Airport, TX to Houston-Intercontinental Airport, TX as the crow flies is 482 km (301 miles).
Accident location: Exact; as reported in the official accident report.
Distance from Laredo International Airport, TX to Houston-Intercontinental Airport, TX as the crow flies is 482 km (301 miles).
Accident location: Exact; as reported in the official accident report.
This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.
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Embraer EMB-120
- 357 built
- 5th loss
- 5th fatal accident
- 3rd worst accident (at the time)
- 8th worst accident (currently)
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