ROTORCRAFT PITCH-ROLL DECOUPLING REQUIREMENTS FROM A ROLL TRACKING MANEUVER

A research investigation has been conducted on the effects of pitch-du e-to-roll and roll-due-to-pitch cross coupling on helicopter handling qualities while performing a forward flight (60 knots) roll axis track ing tack, Conducted under tile US/German Memorandum of Understanding ( MOU) for Cooperative Research in Helicopter Aeromechanics, this study involved complementary use of a NASA-Ames ground-based simulation and two in-flight simulations using DLR's variable-stability BO 105. The r esults show that for a roll tracking task, the current time-domain pit ch-roll cross coupling criteria does discriminate against unacceptable coupling from basic control, rate, and combined control-rate coupling , However, this criteria formal, does not discriminate against washed- out coupling which can occur in helicopters with feedback control syst ems, In addition, the data suggest a tightening in the ADS-33 Level 1- 2 boundary, and the four second window specified for obtaining complia nce data may not be suited for highly agile helicopters. A newly propo sed frequency-domain criteria offers more comprehensive coverage that shows consistency for all types of coupling investigated. An additiona l benefit is that the required frequency-domain data can be obtained f rom the bandwidth tests and analysis, thus reducing compliance flight time by eliminating specific pitch-roll coupling tests.