Page:CAB Aircraft Accident Report, Northwest Airlines Flight 705.pdf/23

 Great strides have been made in the last two years, but the Board believes that still greater efforts are required to reduce this potential hazzard to a minimum If the Board were restricted to making a single recommendation on the problems associated with safe flight in turbulence, it would be to urge that a unified, cohesive federal program be formulated, with a high level board or commission assigned the responsibility for integrating and coordinating the research efforts of all government agencies presently working in this field, and for providing appropriate liaison with all pertinent private groups and industry organizations. The work currently underway within the Interdepartmental Committee for Meteorological Services could well form the nucleus for this broader program which should include not only the meteorological aspects of the problem, but also the operational, human factors, and aircraft design characteristic aspects. In this way, unnecessary duplication of effort can be avoided and research priorities can be established in the interest of conserving available research funds and personnel.

Pending the establishment of such a "Federal Turbulence Program," the Board believes that early FAA and industry attention should be directed to the following:

(1) Explore the possibility of increasing the horizontal stabilizer drive motor torque capacity so as to preclude motor stalling under anticipated conditions, taking proper care against structural damage in the case of a runaway of the more powerful motor.

(2) Consider modifying the elevator control force characteristics to eliminate any appreciable stick force lightening under all reasonable flight conditions inside and outside of the normal operational flight envelope.

(3) Evaluate the desirability of providing a "Turbulence Mode" feature on the autopilot wherein the stabilizer trim and Mach trim systems would be deactivated in this mode.

(4) Expedite the mandatory installation of improved attitude indicators which, by means of size, markings, lettering and/or color coding methods, would provide greater assistance to the pilot in maintaining attitude control even at high pitch and roll angles.

(5) Develop improved flight simulators that can more realistically duplicate aircraft motions and rough air penetrations, and require their use in initial and recurrent flight training programs.

(6) Seek further improvement in the utilization of airborne and surface radar to more safely navigate aircraft through areas of severe weather.

On May 27: 1954, shortly after the NASA longitudinal control force analysis report had been received and evaluated, the Board forwarded to the FAA a recommendation covering essentially the area of elevator control force lightening listed above. Specifically, it was recommended that (a) a spot check of the Boeing 720 fleet be conducted to determine if the cove gap and SAE tap tolerances