Airworthiness and Flight Characteristics Test. Part 2. YAH-64 Advanced Attack Helicopter

Abstract : The Airworthiness and Flight Characteristics (A&FC) Evaluation Part 2, of the prototype YAH-64 helicopter (S/N 77-23258) was conducted at Palomar Airport, Carlsbad, California (elevation 328 ft). A total of 12 flights were conducted between 8 December and 17 December 1981 and 14.3 productive hours were flown. Prior to this test significant design changes were incorporated in the flight control system, the digital automatic stabilization equipment (DASE) and the stabilator system to correct objectionable characteristics determined during the airworthiness qualification program. Significant improvements in handling qualities were noted since the previous evaluation. Uncommanded control inputs, caused by recentering of the SAS actuators, upon failure or disengagement of the DASE may cause a potentially hazardous situation. The instrument flight characteristics of the YAH-64 are satisfactory in smooth air but have yet to be evaluated in turbulent conditions. Manual programming of the stabilator in rearward flight did not significantly reduce objectional vibration at the pilot's station. Results of this test have shown that both previously reported deficiencies and 14 shortcomings have been corrected. One deficiency not previously observed, was identified: the possibility of a false indication of dual engine failure following a single engine failure. Two previously unreported shortcomings were also identified.