Page:CAB Aircraft Accident Report, American Airlines Flight 320.pdf/7

 At the impact the landing gear was extended, the flaps were in approximately the approach position, and the right landing light was retracted. The left landing light was not recovered.

The Board has conducted an investigation of the crash injury aspects of this accident, the results of which will be the subject of a subsequent Board report.

The comparatively lengthy submersion in the East River resulted in corrosion and contamination throughout the engines, propellers, and accessories. Nevertheless, accurate determination of the condition of the parts and components prior to impact was readily accomplished.

Surviving crew members testified that all powerplants were functioning normally until the moment of impact. Detailed examination of the engines and propellers following disassembly confirmed this testimony. Engine and propeller oil systems were free of significant contaminants. There was no preimpact damage, foreign object damage, or evidence of over-temperature. Examination of detailed parts, including bearings, accessory drives, oil pumps, and components of the reduction gear assemblies, did not show any to have failed during engine operation.

Propeller blade angles were relatively uniform and averaged approximately 36 degrees. This blade angle when related to power is consistent with power readings obtained from the recovered aircraft instruments, and the crew's testimony concerning horsepower being used during the approach.

All recovered instrument and instrument system components had been submerged in salt water for periods of time ranging from about ninety-four hours to twelve days. They were corroded, and many suffered from impact damage. All were inoperative with the following exceptions: The captain's horizon direction indicator, the two directional gyros, the autopilot control panel, the two static selectors, the three-axis trim indicator, the two fluxgate transmitters, and the clock on the captain's instrument panel, which was still operating at time of recovery.

The two instantaneous vertical speed indicator instrument cashings were still attached to their respective panels and relatively intact, but the instrument mechanisms were missing and were not recovered. Only one instrument face was recovered.

The altimeters installed on the instrument panels of N 6101A were Kollsman, type A-38586-10-001, pressure drum type, having a range of from minus 2,000 feet to 50,000 feet altitude. The heart of this altimeter consists of two matched diaphragms which, in response to changes in atmospheric pressure, expand and contract. This expansion and contraction is transmitted to a pointer by means of a linkage and gear system. The pointer makes one revolution for each 1,000 feet of altitude change, and two concentric drums measure the number of turns of the pointer and accordingly indicate the 1,000-foot flight levels. Provision is made for barometric setting to correlate altitude indication with the prevailing atmospheric pressure in a manner similar to that employed in conventional three-pointer altimeters except that the numerical values of the setting appear in reverse order.