B-2A accident investigation board

Flying Safety, August, 2003

* Seventh, specialization within the B-2A maintenance career field led to compartmentalization, which led to complacency regarding the dangerous practices of other specialties.

* Eighth, for expediency, and by interpretation, a proper Technical Order Validation and Verification process may have been omitted regarding this method for adjusting the main landing gear sensors using cockpit indications.

* Ninth, there was undue pressure from maintenance supervision to perform maintenance on aircraft components or systems that were operating within T.O. tolerance.

STATEMENT OF OPINION

Under 10 U.S.C. 2254(d), any opinion of the accident investigators as to the cause of, or the factors contributing to, the accident set forth in the accident investigation report may not be considered as evidence in any civil or criminal proceeding arising from an aircraft accident, nor may such information be considered an admission of liability of the United States or by any person referred to in those conclusions or statements.

1. OPINION SUMMARY:

By clear and convincing evidence, I have determined that the cause of this accident was the result of a maintenance technician removing a landing gear safety pin, followed by pushing up a main landing gear lock-link assembly into a retractable and unsafe condition. The landing gear then collapsed as a result of the aircraft's weight. In addition, I have determined by substantial evidence that four factors contributed to the accident.

* First, inadequate training of the maintenance technicians involved contributed to the accident.

* Second, MMT 1, 2 and 3 failed to exercise sound judgment.

* Third, the relevant section of technical order job guide (the implied basis for the training they received and actions they performed) did not direct a step-by-step or sequential method for performing the gear sensor adjustment and may have contributed to this mishap.

* Fourth, apart from MMT2, the maintenance team working on the aircraft was not fully aware of what MMT1 was going to do. The entire team, including MMT1, was unaware of the dangerous nature of MMT1's actions.

This precluded the other maintenance team members from having the opportunity to prevent the mishap.

2. DISCUSSION OF THE OPINION

a. Summary of the Investigation

The investigation was conducted over a three-week period. Nine witnesses and two supervisors were interviewed. Three maintenance technicians directly under the aircraft corroborated the testimony by the mishap maintenance technician at the time of the collapse. A material and technical order expert examined the aircraft's left main landing gear and center-of-gravity. He found no pre-existing conditions that may have contributed to the mishap. Weather, toxicology, and lifestyle were ruled out as possibilities.

b. Causal Factors

1. The mishap maintenance technician removed the left main landing gear safety pin.

2. The mishap maintenance technician then pushed the left main landing gear lock-link assembly into a retractable and unsafe condition.