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.

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

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.

Modern aircraft use a variety of fly-by-wire control devices and combine these with a flight envelope protection system to limit pilot control inputs when approaching the aircraft limits. The current research project aims to increase pilot awareness of such a protection system through the use of force feedback on the control device, i.e., haptics. This paper describes a new iteration of a design with the specific aim to warn the pilot when approaching a limit and provide a clear direction of suggested control input. This is achieved by using vibrations asymmetric in both amplitude, i.e. the mean of the signal is non-zero, and time, i.e. a cue which has a rise time different from the fall time. An evaluation is performed where 24 active PPL/LAPL pilots flew a challenging vertical profile and encountered a windshear. The pilots are divided in two groups: one group performing four flights with haptic feedback, followed by four without, the other groups has a reversed order. Although acceptance ratings slightly improved when providing haptic feedback, the other metrics are unchanged when switching between haptic feedback conditions, due to a large training effect during the first four runs. The results do show that enabling the haptic feedback does seem to improve the learning rate over the first runs, and no after effects are present when feedback is removed. As such, next to the fact that most pilots indicated that they expect an improved safety, this experiment shows a potential training benefit of haptic feedback. Nomenclature Symbols b Damping, Nms/rad I Amplitude of the discrete tick, Nm k Spring, N/rad m Mass, kg n Load factor, g q Pitch rate (θ), rad/s V Velocity, m/s α Angle of attack, rad δ Control device deflection, rad θ Pitch angle, rad φ Bank angle, rad

Modern aircraft can be equipped with a flight envelope protection system: automation which modifies pilot control inputs to ensure that the aircraft remains within the allowable limits. Overruling the pilot inputs may lead to mode confusion, even when visual or auditory feedback is provided to alert pilots. We advocate using active control devices to make the flight envelope protection system tangible to the pilot. This paper presents the main findings of an evaluation of three haptic feedback designs for flight envelope protection. The first concept used both force feedback and vibro-tactile alerts, producing promising, yet inconclusive, results. The second concept used asymmetric vibrations to give directional alerting cues, which did not result in improved performance on initial use, but which did yield improved learning rate for the task. The third system employed force feedback to physically guide the pilot away from flight envelope limits, which yielded safety improvements from the first use, but created dependence: pilot performance degraded immediately after the force feedback was removed. From this, we advise to use asymmetric vibrations during training for flight envelope excursions, to leverage active control interfaces for providing force feedback during operation, and reevaluate a combination of both to combine their advantages for single-pilot operations.

Objective We tested whether a procedure in a hexapod simulator can cause incorrect assumptions of the bank angle (i.e., the “leans”) in airline pilots as well as incorrect interpretations of the attitude indicator (AI). Background The effect of the leans on interpretation errors has previously been demonstrated in nonpilots. In-flight, incorrect assumptions can arise due to misleading roll cues (spatial disorientation). Method Pilots ( n = 18) performed 36 runs, in which they were asked to roll to wings level using only the AI. They received roll cues before the AI was shown, which matched with the AI bank angle direction in most runs, but which were toward the opposite direction in a leans-opposite condition (four runs). In a baseline condition (four runs), they received no roll cues. To test whether pilots responded to the AI, the AI sometimes showed wings level following roll cues in a leans-level condition (four runs). Results Overall, pilots made significantly more errors in the leans-opposite (19.4%) compared to the baseline (6.9%) or leans-level condition (0.0%). There was a pronounced learning effect in the leans-opposite condition, as 38.9% of pilots made an error in the first exposure to this condition. Experience (i.e., flight hours) had no significant effects. Conclusion The leans procedure was effective in inducing AI misinterpretations and control input errors in pilots. Application The procedure can be used in spatial disorientation demonstrations. The results underline the importance of unambiguous displays that should be able to quickly correct incorrect assumptions due to spatial disorientation.