Delta Air Lines Flight 1141

Introduction

On August 31, 1998, Delta Air Lines Flight 1141 crashed shortly after taking off from Dallas-Fort Worth International Airport. Out of the 108 people on board (101 passengers 7 crewmembers), 14 were killed (12 passengers and 2 crewmembers), 26 were seriously injured (21 passengers and 5 crewmembers), and 68 suffered minor or no injuries.

Delta Air Lines Flight 1141 was a regular scheduled domestic passenger flight between Dallas-Forth Worth International Airport, Texas, and Salt Lake City International Airport, Utah. It operated a Boeing 727-232, a mid size, narrow body, three engine jet airliner, registered as N473DA.

At 0830hrs CDT (central daylight time), flight 1141 was cleared to taxi and the push back began. At 0859hrs, flight 1141 was cleared for take-off. Shortly after, at 0901hrs, flight 1141 struck the ground.

Procedural_Indiscipline.jpg

Flight 1141 Cockpit Voice Recorder

Investigation

Investigation carried out by the National Transportation Safety Board (NTSB) determined two causes of the accident:

1. Wing flaps and slats were not configured properly for take-off.
2. The take-off warning system was not functioning properly as it failed to alert the crew that the aircraft was not in take-off configuration with take-off power set.

With the flaps and slats in the incorrect position for take-off, it resulted in a loss of lift. This led to a high angle of attack of the wing after take-off, which eventually disrupted airflow over the wing, causing an engine surge and also activating the stall warning stick shaker. By applying full power and lowering the nose below the stick shaker angle of attack, the aircraft could have recovered. However, evidence indicates that call for full power was heard 0.6 seconds before the impact. Despite the stick shaker warning going on, the pilot did not immediately recover from it.

The aircraft collided with the instrument landing system (ILS) localiser antenna at approximately 1000ft from the end of the runway and finally came to halt 3200ft from the end of the runway. It was only airborne for 22 seconds.

Human factors

1. Sterile Cockpit – A rule set by the FAA where there cannot be any conversations unless flight related, normally below 10,000ft. From the cockpit voice recorder of flight 1141, it shows that the pilots and a flight attendant were having casual conversations during this period, which might have distracted the pilot from the checks.

2. Cockpit discipline – The pilots did not adhere to the sterile cockpit rule and as a Captain, he failed to enforce it when required.

3. Complacency – The first officer failed to move and visually check that the flaps are in the take-off setting of 15 degrees, and failure of the Captain to check and ensure.

4. Situational awareness and decision making – The time between the stick shaker warning and Captain calling out “Full power” was 19 seconds, which might suggest that there was poor situational awareness and decision making.

References
NTSB (Sep 26, 1989). Aircraft Accident Report. Retrieved on Sep 6, 2012, from http://www.airdisaster.com/reports/ntsb/AAR89-04.pdf.
Wikipedia (Sep 2, 2012). Delta Air Lines Flight 1141. Retrieved on Sep 6, 2012, from http://en.wikipedia.org/wiki/Delta_Air_Lines_Flight_1141.
Elistmania (n.d.).15 Air disaster near misses. Retrieved on Sep 6, 2012, from http://www.elistmania.com/still/15_air_disaster_near_misses/
Youtube (Nov 29, 2010). Cockpit Voice Recorder - Delta Flight 1141 - CLEARER AUDIO. Retrieved on Sep 6, 2012 from http://www.youtube.com/watch?v=6gNklQRE6OQ.


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