Page:CAB Accident Report, American Airlines Flight 383.pdf/26

– 25 – period of time. As indicated earlier in the factual portion of the report the B-727 flight characteristics were not a factor in the cause of this accident. Moreover, the pilot groups have indicated that in general the Boeing 727 is a reliable, versatile, and highly responsive aircraft and that no major difficulties are being experienced in actual line operations.

Yet, the Board's investigation did uncover certain aspects of operational practices in the Boeing 727 that warrant industry attention in the interest of preventing future accidents. It was noted in the NASA-VGH studies that close-in, high descent-rate, unstabilized approached are being conducted more often in the 727 than in any of the other jet transports studied. Why this is true is not evident from the preliminary review and any realistic evaluation will have to await a final NASA report on this matter. However, from an analytical viewpoint it can be seen that the principal application of this aircraft has been geared to a short/medium haul of "up-down" type operation as compared to the longer range (time-at-cruise) type operation of the older and larger jet transports. It may be that the very nature of this (short range) operation is engendering deviations from the hitherto standard jet operating principles. Also, consideration must be given to the fact that the 727 does have highly responsive and versatile flight characteristics and that these favorable characteristics may be misleading to the pilot, or are presenting the impression that greater liberties may be taken with the aircraft in normal operating situations, especially in the approach/landing regimes. It should be stressed that because of the high drag characteristics of the aircraft in the 40-degree flap configuration, high descent rates and airspeed reduction, in response to decreased thrust, can develop more rapidly than in the less sophisticated models and that this flight regime should be avoided close to the ground. It was noted that most of the 727 operators have included in their flight manuals information concerning the avoidance of high descent rates during the landing approach and also, that the FAA has instituted a requirement for the demonstration of a low altitude high descent rate maneuver as part of the air carrier training programs.

The Board does not know which of the above described factors ("up-down" type operation, sophisticated-responsive aircraft) is causing the results indicated in the NASA-VGH studies, or if some combination of these factors is involved. However, the Board believes it is of sufficient importance to warrant a thorough review by industry to resolve this matter.

2.2 Conclusions

The entire investigation and in particular the specific examination of the Boeing 727 flight performance and characteristics revealed no design deficiencies or unsatisfactory operating characteristics. Furthermore, the latter review of the aircraft design aspects uncovered no factors that would have had a significant effect on the events leading up to the accident.

It is concluded that the 20-minute delay incurred by the flight in departing LaGuardia, combined with the forecast and inflight observations of thunderstorm activity in the Cincinnati area, prompted the crew to conduct the flight in a manner so as to greatly expedite their arrival at the Cincinnati Airport. Once in the Cincinnati area there can be no doubt that the crew was aware of the rapidly deteriorating weather situation both through visual observations and radio communications with the tower as they proceeded on the downwind and base legs. In view