Page:CAB Aircraft Accident Report, American Airlines Flight 320.pdf/14

 In rejecting the possibility of dual and simultaneous altimeter error the Board must, as a consequence, reject portions of the testimony of one or both flight crew members. Considering that the flight crew members received physical injuries and that they were also under great emotional stress, such questioning of their testimony has a rational basis. Under such circumstances, the Board has frequently found that the recollection, particularly of events immediately preceding an accident, is very difficult and often erroneous. Furthermore, we are mindful of the natural human tendency to assume conformance with standard operating procedures to fill in the voids or hazy areas of one's memory. On the basis of other evident before us, the Board is compelled to reject this testimony to the extent that it would require dual and simultaneous failure of the altimeters on the order of a 500-foot lag.

The possibility of a single altimeter failure obviously avoids most of the stumbling blocks which compelled the Board to abandon further consideration of a double altimeter failure. The absence of need for the acceptance of compounded mathematical probabilities of such extremely low order of itself facilities this judgment. However, if we assume failure of First Officer Hlavacek's altimeter only, we are met with so many operational imponderables as to make rationalization impossible. So far as this accident is concerned, any single altimeter failure must have involved the captain's altimeter since it is clear that the captain was at the controls of the aircraft during the approach. The Board cannot conclude, however, that a single altimeter failure occurred.

Although First Officer Hlavacek had testified concerning his observation of altimeter indications down to an altitude of 600 feet, he had no recollection of a lower altitude indication. It was his impression that the impact occurred shortly following his 600-foot observation; however, the Board believes that his subsequent judgment of the this time interval may be incorrect. While approaching an altitude of 500 feet it would have been expected that, in addition to monitoring the instrument panel, Mr. Hlavacek would be scanning the approach area for lights and handling radio communications. Considering the sparseness of lights on the approach over the East River, there could well have been greater concentration or attention than is usual since it is always difficult at night to judge attitude and altitude over the water. While the aircraft was in instrument conditions, it is also not at all unlikely that the copilot was giving careful attention to the captain's efforts to maintain the localizer path, especially in view of the apparent difficulties being experienced by the captain in maintaining a precise course. Although preoccupation with this or any of the several elements of a new cockpit environment could reasonably explain the failure of Mr. Hlavacek to follow the procedure required in the Operations Manual with respect to monitoring and calling out altitude and airspeed below 600 feet, the Board believes it more likely that he was anticipating breaking out beneath the overcast and, thereafter, having seen lights on the ground or water, was focusing particularly on visual identification of the airport and was no longer monitoring the flight instruments.

At and prior to reaching 600 feet, the flight crew members are clear as to their testimony of cross-checking altimeters. If any portion of the testimony of the flight crew members is to be regarded as sufficiently reliable for the purpose of