Handling Qualities Evaluation of a Variable Stability Navion Airplane (N66UT) using Frequency Domain Test Techniques

General aviation small aircraft handling quality certification has predominately been accomplished using traditional time-domain test techniques. This thesis investigates the handling quality characteristics of the variable stability Navion airplane, tail number N66UT, using frequency-domain test techniques. N66UT is configured with conventional flight controls at the copilot's station and a fly-by-wire set of flight controls at the pilot's station. Time delays between the fly-by-wire and conventional flight controls were determined to be minimal. Evaluation of handling qualities of the aircraft were compared to the fixed wing flying qualities speci fied in M IL-HDBK- 1 797. Analysis of flight test was conducted using Comprehensive Identification from Frequency Responses (CIFER) program developed at NASA Ames Research Center, Moffett Field, California.

Frequency-domain system-identification methods are well suited to aircraft flight­ control and handling-qualities analysis since many current design specifications, design and analysis techniques, and acceptance flight-test techniques are based in the frequency domain. The response characteristics of the Navion N66UT were stable for the longitudinal, lateral and rudder control inputs. The handling quality parameters met or exceeded proposed Level 1, Category C requirements, and Level 2, Category A requirements for fixed-wing military aircraft. The fly-by-wire system closely mirrored conventional control behavior well beyond bandwidth frequency. Time delay differences between conventional and FBW systems ranged from very near 0 to 9.5 ms. Throttle response data results were inconclusive. Further flight-testing is required.