From Introduction to Aircraft Flight Mechanics: Performance, Static Stability, Dynamic Stability, and Classical Feedback Control

7.5 Cooper Harper Ratings

All of the previous discussion on dynamic stability guidelines may imply that good aircraft handling qualities are simply a matter of satisfying published criteria on parameters such as natural frequency, damping ratio, and time constant for each of the dynamic modes. Nothing could be further from the truth. The criteria discussed provides a starting point for designers and a tool for flight testers to evolve the handling qualities of an aircraft. A vital contribution to this evolution is pilot comments obtained from simulations and test flying of the aircraft. A structured rating scale for aircraft handling qualities was developed by NASA in the late 1960s called the Cooper Harper rating scale. This rating scale applies to specific pilot-in-the-loop tasks such as air-to- air tracking, formation flying, and approach. It does not apply to open-loop aircraft characteristics such as yaw response to a gust. An important part of using the Cooper Harper rating scale is careful definition of the evaluation task and performance standards for that task. Figure 7.28 presents the Cooper Harper rating scale.

Figure 7.28: Cooper-Harper rating scale.

The Cooper Harper rating scale is a decision tree for pilots to rate a specific mission task. The pilot begins the decision process at the lower left corner. Aircraft controllability, pilot compensation (workload), and task performance are key factors in the pilot's evaluation. A Cooper Harper rating of "one" is the highest or best and a rating of "ten" is the worst, indicating the aircraft cannot be controlled during a portion of...

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