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.@en

Previous research showed that haptic feedback, in the form of asymmetric vibrations, can be used to provide directional cues to the operator in a laboratory setting. Nevertheless, it is unclear how these vibrations should be designed for pilots controlling their aircraft using a side-stick. This paper aims to determine the magnitude and shape for which vibrations can still be perceived as directional cues, for one fixed frequency based on literature. The threshold magnitude of two forcing function shapes (triangular and saw tooth) was determined for both pulling and pushing cues in a just-noticeable-difference experiment. Participants were asked to report the direction at varying input magnitudes while exerting different offset force levels on the stick at different positions. Results confirmed all hypotheses: They indicated a lower perception threshold for the asymmetric saw tooth shaped vibration compared to a triangular shaped; higher offset force decreased the threshold in the opposite direction; and stick position had no effect on the obtained thresholds. Based on the experiment we advise to use saw tooth vibrations with an amplitude higher than 0.094 Nm. @en

Haptic cues on the side stick are a promising method to reduce loss of control in-flight incidents. They can be intuitively interpreted and provide immediate support, leading to a shared control system. However, haptic interfaces are limited in providing information, and the reason for cues may not always be clear to pilots. This study presents the results of the conceptual development of visual display symbology that supports haptic feedback on the side stick in communicating flight envelope boundaries to pilots. Novel indications for the limits of airspeed, load factor, angle of attack, and angle of bank, which for the first time simultaneously indicate magnitude and direction of the haptic cues, were integrated in an Airbus primary flight display. The symbology was tested in a pilot-in-the-loop experiment with professional Airbus pilots (N=16) flying several approaches in alternate law with haptic feedback. Objective results do not show clear improvements, 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 improve the interface design, remove unused indications, and test a bank scenario using current operational bank limits.@en

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.@en

Improving the safety level of aviation is vital to prevent serious accidents. One key area where improvements can be made is the prevention of loss of control occurrences, by preventing the aircraft state to pass beyond the limits from which no recovery is possible. Such improvements can focus on improved monitoring of the main flight parameters and active automationmodes. The limits of an aircraft are typically expressed in terms of a flight envelope which represents the allowable region of load factor versus velocity. Modern day aircraft can support pilots in monitoring themain flight parameters by employing a flight envelope protection system: the inputs of the pilots are routed to the flight control computers which can impose limits on those inputs. In doing so, the computers are protecting the aircraft state fromleaving the flight envelope. When the control device is linked to the control surfaces, for example using cables and pulleys, any limit imposed by the flight control computer can be felt by the pilot. With the advent of fly-by-wire control devices, the mechanical link is replaced by an electrical connection, resulting in the loss of this information using the sense of touch. This haptic information was initially not included as it requires active control devices which had issues regarding the size, power and stability requirements. The lack of such haptic information on the flight envelope protection system might have been a contributing factor in some accidents. Nowadays active control devices do meet the requirements in terms of size, power and stability, and offer the possibility to re-introduce haptic feedback in fly-by-wire control systems. Therefore, this thesis looked at adding haptic feedback to the control device of a modern aircraft to increase pilot awareness of the flight envelope protection system...@en

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. @en

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.@en

Ground-based demonstration of spatial disorientation (SD) has been recommended for military as well as commercial pilot training. Although the leans illusion is the most common form of SD, no data exist yet of an effective ground-based leans procedure for a hexapod simulator. In this paper we describe the development of such a procedure and its tuning with nine subjects. The procedure was then used in an experiment with 18 airline pilots, which is described elsewhere. The final procedure started with a prepositioning phase, during which the simulator platform was slowly tilted to a 3.5° prepositioning roll angle, while the pilot performed a distraction task and the instruments and outside visuals indicated level flight. Next followed an adaptation phase, during which the pilot's vestibular system adapted to the new angle, the outside visibility degraded to zero and the instruments were covered. Then the platform was moved back to level, above the perceptual threshold, after which the instruments were shown again. The pilot was then tasked to roll back to level. The addition of the motion cues caused an increase in roll reversal errors by a factor of 3 in airline pilots. The procedure can be implemented in a scenario for demonstrating the leans in a cost-effective simulator. @en

Current Airbus aircraft use a fly-by-wire control device: a passive spring-damper system which generates, without any force feedback, an electrical signal to the flight control computer. Additionally, a hard flight envelope protection system is used which can limit the inputs of the pilot when approaching the edges of the flight envelope. To increase the situation awareness of the pilot, this research aims to provide intuitive information on the flight envelope through haptics, force feedback trough the control device, integrated in the existing Airbus control laws. The goal of this paper is to describe when and how haptics is used in this design. The pilot can get five cues of the flight envelope: when approaching the flight envelope a discrete force cue is given. Next, control inputs which move the aircraft closer to the flight envelope are indicated with an increased spring coefficient. Moving too close to the lower velocity limit activates a stick shaker: a vibration force on the stick. If a stick neutral position is not sufficient to return to the safe flight envelope, the stick is moved forward to the desired control input. Finally, following the automatic Airbus pitch up command during an overspeed condition, the stick is moved back to follow this command. This new system is expected to help identifying the situation and choosing a possible mitigation technique which is evaluated for two scenarios: when the aircraft is moving to the flight envelope, i.e. a windshear, or when the flight envelope moves towards the aircraft. @en

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. A previous design used asymmetric vibrations to cue the pilot on the flight envelope. The evaluation showed no improvement in metrics at the first emergency encounter, yet did show a potential training benefit. Therefore, a new haptic feedback concept was designed with the specific aim to guide the pilot when approaching a limit and provide support from the first time use. This paper evaluates these haptic feedback designs with 36 active PPL/LAPL pilots who flew a challenging vertical profile and encountered a windshear in a fixed-base simulator. The pilots were divided in three groups who received either cueing, guidance, or no haptic feedback. It was hypothesized that: (i) cueing haptic feedback provides a faster learning rate compared to no-haptics, and (ii) guidance haptic feedback results in best performance from the first run yet worse metrics when no feedback is provided. Comparing the results of the cueing and no-haptic feedback groups confirmed the first hypothesis. Results also showed that the guidance haptic feedback resulted in improved metrics at the first run, and the worsening of metrics when no longer provided.@en

Modern fly-by-wire aircraft use flight envelope protection systems, whose actions are not always clear to pilots. To promote situation awareness, proximity to the limits of the flight envelope can be communicated using haptic feedback, by providing forces through the control device. Such a system was developed and this paper reports on the evaluation experiment. Professional pilots were invited to fly an Airbus A320 model in the Delft University of Technology Simona research simulator. A windshear and an icing scenario were flown using a full and degraded control law, with and without the haptic feedback system. The objective results show that the haptic feedback system does not lead to significant improvements in either performance or safety metrics, but also does not interfere with nominal pilot tasks. In the debriefing questionnaire, however, pilots expressed a clear preference for the haptic system. Recommendations for future research include the addition of visual support to complement the haptic cues, and the redesign of the scenarios to allow pilots more freedom in control. @en

The use of haptic feedback as a tool for skill training has shown benefits for the formation ofmotor-memory and support for certain temporal tasks. Therefore, this research focuses on the development of a haptic aid for supporting the training of the challenging manual flare maneuver in initial pilot training. The haptic aid, which consisted of three “off-target” haptic modes each meant to clarify a typical mistake in flare execution, was designed based on instructor actions during real flight training. The High Roundout (HR) mode was designed to better train flare timing. This haptic mode implemented an increase in pitch-up stick stiffness when still above the desired flare altitude. The Late Roundout (LR) and Ballooning (BA) modes used repeated pulses on the stick – in pitch-up and pitch-down directions, respectively – to alert trainees when they flared too late (or not at all) or when overly large pitch-up inputs that would lead to regaining altitude were given. To test the haptic aid, a quasi-transfer-of-training experiment with 16 novices was performed in a full-motion research simulator. A baseline group and a group receiving haptic feedback were compared and in the haptics group the haptic aid was used during the training phase of the experiment, but disabled in the evaluation phase. A second-stage evaluation, with an untrained landing scenario, was used to verify the generalizability of the skills. The obtained data indicates no improved learning effect regarding flare trajectory. It was found that due to the difficulty of the task, strategies based on linking the cues to desired discrete touchdown performance were formed. The usage of the HR mode, however, resulted in more consistent initiation of the flare which was retained after transfer. The second-stage evaluation also did not show worsening of flare performance, suggesting generalizability of the skills with the haptic aid. @en

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.@en

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.@en