§29.173 Static longitudinal stability

(a) The longitudinal control must be designed so t hat a rearward m ovement of t he control is necessary to obtain an airs peed less th an th e trim speed, and a forward m ovement of t he control is necessary to obtain an airs peed more than the trim speed. (b) Throughout the full range of altitude for which certification is req uested, with th e th rottle and col lective pi tch hel d const ant duri ng t he manoeuvres specified in CS 29.175(a) through (d), the slope of the cont rol posi tion versus ai rspeed curve must be positive Ho wever, in limited flight conditions or m odes of operat ion det ermined by the Agency to be accepta ble, the slope of the control posi tion versus ai rspeed curve m ay be neutral or negat ive i f t he rotorcraft possesses flight ch aracteristics th at allo w th e p ilot to maintain airspeed wi thin ±9 km /h (±5 knot s) of the desi red t rim ai rspeed wi thout exceptional piloting skill or alertness.