Common Themes

Organizational Lapses

The investigation revealed the organization had several breakdowns related to their maintenance practices:

  • Investigators believe the pitot tube covers were not installed during some period of the aircraft's non-flying down time. This allowed the suspected mud dauber wasp to build a nest inside the captain's pitot tube and essentially be the root cause of the accident.
  • The maintenance crew did not do the manufacturer-prescribed pitot static check that was required for an aircraft that was not flying for the amount of time this aircraft was down (20 days).

Human Error

The investigators determined that the crew made several critical errors during the course of this accident. These are described in chronological order below:

  • Contrary to standard operating procedures (SOP), the captain continued the takeoff, even though he discovered his airspeed indicator was not working prior to V1, the "decision speed." SOP dictates he should abort the takeoff prior to V1 for any significant aircraft problem.
  • Once airborne they were confused with the airspeed indications and did not perform basic diagnosis techniques to determine which airspeed source was correct. Review of the cockpit voice recorder indicated that they did seem to know that the standby airspeed indicator was accurate but they did not use that to fly by.
  • In their diagnosis of the airspeed problem and associated EICAS messages, they tried to reset circuit breakers (unknown which ones they were referring to) which is stricktly against the manufacurer's procedures. This just wasted time during the accident sequence.
  • Knowing they had some strange airspeed indications, they did not accomplish the "UNRELIABLE AIRSPEED" checklist. If they had, they may have been able to understand what airspeed was correct and use that, or have been directed to go to designated pitch and power settings for safe flight.
  • The captain did not react to the stall warning stick shaker. It was activated at the same time as they were getting overspeed indications and the crew were confused as to which was correct. They appeared to not understand that the stick shaker is activated by the AOA vanes and not by the airspeed. Had they responded to the stick shaker they may have been able to recover the aircraft or at least had more time to diagnose the situation.

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