Pitch drop-back

{{Short description|Aerodynamic phenomena}}

Pitch drop-back is the phenomena by which an aircraft which is perturbed in flight path angle from its trim position by a step input exhibits an output which is indicative of a second order system.{{cite web|url=http://www.ifac-papersonline.net/Detailed/38674.html |title=Longitudinal stability and control of large tilt-rotor aircraft |publisher=IFAC-PapersOnLine |date=2008-10-17 |accessdate=2010-10-05}}

A pilot who actuates an elevator input may find that the aircraft then "droops" or "drops back" to a position further toward the start position. The phenomenon is particularly marked in tilt-rotor aircraft.{{cite web|last=Mark Voskuijl|first=Daniel J. Walker|title=Active Control of Flight Path and Critical Loads in Tilt-Rotor Aircraft|url=http://www.liv.ac.uk/~djwalker/ahs2007djw.pdf|publisher=Engineering Department: University of Liverpool|accessdate=5 October 2010}} Pitch drop-back may be controlled using a Stability Augmentation System or Stability Control and Augmentation System.{{cite web|url=http://www.flightlab.liv.ac.uk/publications/erf_paper23_final.pdf |title=Measuring Simulation Fidelity through an Adaptive Pilot Model |date= |accessdate=2010-10-05}}