Page:CAB Accident Report, American Airlines Flight 383.pdf/18

– 17 – However, it was also determined that the high lift/drag ration obtained in the 727 with full flaps extended requires the use of a comparatively higher percentage of thrust output than other models, in order to maintain desired landing speeds and rates of descent. At idle thrust and 40 degrees of flap the Boing 727 descent flightpath at the minimum approach speed was about two degrees steeper than the average descent paths for the other models in the full flap landing configuration. It is recognized that the approach speed is lower for the B-727 than the other models with full flaps and idle power and that steeper descent paths in this configuration should, therefore, be expected. It was also found that the 727, with its hydraulically powered flight control system, has lighter control forces and is more responsive to control input than the other models.

Another aspect of this phase of the investigation was a survey conducted among pilots of the Allied Pilots Association (APA) and the Air Line Pilots Association (ALPA) who represent most of the U. S. Air Carrier pilots involved in day-to-day operation of the Boeing 727. It was thought that these associations, more than perhaps any other one organization, would be aware of any hazardous or undesirable features and unusual or marginal performance/flight characteristics relating to actual line operations in the B-727. The results of this poll revealed that the pilots were generally pleased with the flight characteristics and features of the 727 and that they had experienced no major difficulties in the operation of this aircraft. Similarly, the report of an ALPA evaluating committee, relating to the design and flight characteristics of the B-727, geared primarily to the "line pilot" viewpoint, was made available to the Board for examination. A review of this report revealed a favorable evaluation of the B-727 by the committee with one of the conclusions being that the aircraft constituted a major advance in aircraft design which would significantly enhance air carrier operations. This report also noted that high descent rate characteristics with the flaps in 40-degree position required the use of a greater percentage of thrust to maintain desired speeds and recommended against steep approaches with high descent rates.

The National Aeronautics and Space Agency (NASA) was requested to review their Boeing 727 VGH data for any evidence of unusual operating practices or occurrences. Their review of the VGH records indicated that high descent rates close to the ground and non-stabilized close-in approaches occur at a somewhat higher frequency in B-727 operations than in operations involving other jet transports. The frequency of occurrence varied from airline to airline.

Another facet of this part of the investigation was a review of the Boeing 727 flight crew training programs as conducted by the major air carriers utilizing this type aircraft. Because the several major 727 accidents which were reviewed occurred during the descent or landing position of the flight the examination of the various training programs was concentrated on the descent, approach, landing, and landing abort flight regimes. It was found that the standards and procedures used in establishing the criteria for the 727 training programs were essentially the same as those utilized in developing the 707/720 training programs and were in compliance with FAA requirements. In general, it was noted that the average pilot transition time and training failure rate in the Boeing 727 were approximately the same, or perhaps slightly less than those in the Boeing 707/720 aircraft. It was also found that there was no specific maneuver, required or incorporated, in the