Page:CAB Accident Report, American Airlines Flight 383.pdf/19

– 18 – air carrier training programs for demonstrating high-sink rate close to the ground. However, all of the air carrier training and operations manuals reviewed stressed that high sink rates in this flight regime should be avoided.

2. ANALYSIS AND CONCLUSIONS

2.1 Analysis

The investigation of this accident disclosed no evidence of any failure or malfunction of the aircraft, its system or components. All applicable aids to navigation, and runway/approach lighting aids were operating satisfactorily during the approach and at the time of the accident. The aircraft and crew were properly certificated and the flight was properly dispatched. All communications during the approach were considered to be normal and revealed nothing to suggest any aircraft or flight crew distress. The last radio transmission, five seconds before impact, indicated that the crew was unaware that they had descended to an altitude below the level of the airport.

After an exhaustive review and evaluation of the available evidence, the Board has become convinced that the cause of the accident is directly related to the manner in which the crew operated the flight and indirectly related to certain specific factors that may have influenced or affected the crew during the landing approach.

On of the factors which undoubtably influenced the conduct of this flight was the weather situation which existed in the Cincinnati area and the specific conditions which were encountered by N1996 during the approach. Based on USWB and witness observations during this time it was reliably ascertained that a line of rain showers and thunderstorms, oriented east-northeast/west-southwest, was moving into the area from the northwest at a speed of 25 knots. Cloud to cloud lightning was reported in the vicinity of the thunderstorms. The surface visibility at the airport was diminishing rapidly due to the precipitation associated with this line. Recorded values showed that between 1902 and 1903 (just after the time of the accident) visibility on runway 18 dropped from between 5-7 miles to 1-1/8 miles, then increased almost immediately to better than two miles. Cloud coverage in the area consisted of an overcast in the process of lowering from approximately 4,000 feet a.f.l. to 2,500 feet a.f.l. with broken clouds based near 1,500 feet a.f.l. A few fracto-stratus or "scud" clouds were located below these layers to the northeast of the field along the Ohio River with light precipitation occurring in this area. Based on surface visibility values it is believed that inflight visibility in the rain showers would have been two miles or less depending on the intensity of the precipitation. Inflight visibility to the east and northeast of the field, along the downwind landing leg, would have been in excess of seven miles.

No inflight turbulence was reported in the area nor was there any significant turbulence indicated on the flight recorder readout. The wind shear of .06 knots per hundred feet and the component headwind change of five knots per minute during the last minute of flight would have had a negligible effect on the flightpath of the aircraft and are not considered to have had any bearing on the cause of this accident.

The weather briefing received by the crew prior to departure from LaGuardia is considered to have been adequate and representative of the conditions existing in the area at the time of their arrival.