Greek Symbols α Angle of attack, rad δ Control device deflection, rad θ Pitch angle, rad φ Roll angle, rad Roman Symbols x Distance from starting position, m F Force, N n Load factor, g q Pitch rate (θ), rads −1 k Spring, N rad −1 t Time, s V Velocity, ms −1

to initiate your request. See also AIAA Rights and Permissions www.aiaa.org/randp. *Ph.D. Student, Control and Simulation, Kluyverweg 1; d.vanbaelen@ tudelft.nl. Student Member AIAA.

Several modern aircraft use a passive control manipulator: a spring-damper system that generates command signals to the flight control computers in combination with a flight envelope protection system that limits pilot inputs when approaching the aircraft limits. This research project aims to increase pilot awareness of this protection system through the use of force feedback on the control device, that is, haptics. This paper describes in detail how the haptic feedback works and when it triggers; another paper will discuss the results of an experimental evaluation. With the current haptic design, pilots can get five cues: first, a discrete force cue when approaching the limits; second, an increased spring coefficient for control deflections that bring the aircraft closer to its limits; third, a stick shaker for low velocities; fourth, if a low-velocity condition requires an input, the stick is moved forward to the desired control input; and finally, the stick follows the automatic Airbus "pitch-up" command during an overspeed condition. This novel system is expected to help pilots correctly assess the situation and decide upon the right control action. It will be evaluated in two scenarios close to the flight envelope limits: a windshear and an icing event. Nomenclature a = acceleration, m∕s 2 C L = lift coefficient D = drag, N F = force, N g = gravitational acceleration, m∕s 2 K = gain k = spring, N∕rad L = lift, N m = mass, kg n = load factor, g q = pitch rate, rad∕s S = surface, m 2 T = thrust, N t = time, s V = velocity, m∕s W = weight, N α = angle of attack, rad β = sideslip angle, rad γ = flight path angle, rad δ = control device deflection, rad θ = pitch angle, rad ρ = density, kg∕m 3 φ = roll angle, rad Subscripts br = breakout max = maximum value min = minimum value nom = nominal value np = neutral point prot = protected region value

This paper describes the design and evaluation of a visual display in supplementing haptic feedback on the side stick as a way to communicate flight envelope boundaries to pilots. The design adds indications for the limits in airspeed, load factor, angle of attack and angle of bank to a standard Airbus primary flight display (PFD). The indications not only show the limits of the flight envelope, but also indicate magnitude and direction of the haptic cues. Fifteen professional Airbus pilots and one Airbus sim instructor participated in an experiment in the SIMONA Research Simulator at Delft University of Technology. Several approaches in three different scenarios were flown in alternate law with the old and new PFD, while haptic feedback was always enabled. Objective results do not show clear improvements with the new display, although the time spent outside the flight envelope is slightly reduced. Subjective results indicate a preference, however, for the new display and an increased understanding of the haptic feedback. Further research is recommended to focus on improving the design by removing unused indications and setting up an experiment with a bank scenario that allows the use of operational bank limits rather than artificially reduced limits.

Perspective flight-path displays are a viable alternative for the aircraft primary flight display, but increases the pilot head-down time. A haptic interface is developed to counter this effect and increase the task-sharing performance during approach. An experiment (n=12) was conducted to test the effects of the haptic design on primary task performance with a tunnel-in-the-sky display, in a low and high workload condition. To investigate the effects of the haptic interface on the headdown time, a secondary task was presented on the simulator outside visual, in the form of bucket-shaped figures, requiring participants to indicate the direction of the one divergent figure. Secondary task performance was measured by success rate, average time to answer correctly and-by means of eye-tracker measurements-head-up time and number of gaze switches. Pilots also provided a subjective measure of their mental effort after each run. Results show that haptic feedback significantly increases both primary and secondary task performance of the pilots, especially when the primary task is more challenging. Workload ratings are significantly lower, and head-up time increases with haptic feedback.