1 Introduction

Until now, most airliners deflect the flaps and slats in fixed steps. During the approach, the slats/flaps are extended after the maximal allowable speed for the next higher slat/flap setting is undershoot. During aircraft design, typically four or five fixed settings are defined based on the needed performance for take-off and landing. Commonly the slats/flaps are fully extended to achieve a very large lift coefficient for landing. The resulting significant increase in induced drag is accepted during the approach. For take-off, where drag should be minimal, three or more settings between the clean configuration and the landing configuration allow compromises between large lift coefficients and a minimum increase of drag coefficient. The Airbus A350 uses small flap deflections (\(<4^\circ\)) for drag reduction during cruise flight to vary the wing’s camber [1]. The Boeing 787 features a similar variable camber function for cruise [2]. The variable camber is used to reduce fuel consumption during cruise flight and gust load alleviation. The McDonnell Douglas MD-11 has a system called Dial-A-Flap that allows the selection of intermediate flap positions degree-wise for take-off [3]. Dial-a-Flap allows for an optimal payload concerning the actual conditions (runway length, air density, temperature). None of these functions is available for landing and none of them is able to move the slats/flaps to all possible detents automatically. In an earlier project at the department, a function was developed for automatic slat/flap configurations during approach, but only the fixed positions as they can be chosen by the pilot in current airliner are available for this function called Auto-SFS [4, 5]. Auto-SFS showed benefits in fuel consumption and workload reduction for the pilots during the approach.

Intelligent wing technologies are being developed and evaluated in the INTELWI research project. The project focuses on new sensor, control and actuator technology for wings and brings them together in an overall design. In the project, TU Berlin is investigating a function for automatic continuous flap operation [6]. With this function, the flap setting is automatically and continuously adjusted based on airspeed, aircraft mass and flight path altitude, without the need for direct action by the pilot. It consists of two control laws, which differ in the possible deceleration rates, between which the pilot can choose via a switch in the cockpit. One control law is based on the minimum sink rate and the other one is based on the optimal glide path angle. In addition, the pilot is informed when exactly the landing gear must be extended at the latest to achieve a stabilised approach at 1000 ft with the current flap control law. On one side, it is possible to reach a modest reduction in fuel consumption, while on the other side, the workload for the pilot is not increased, but considerably softened due to the additional automation compared to a current standard approach. To increase pilot acceptance of the automatic continuous flap function, the evaluation of the function and further development needs to be based on pilot comments.

Flight simulator tests are the final tests prior to flight tests. Handling qualities evaluation is carried out via pilot rating according to a pilot rating scale, and is, therefore, dependent on pilot’s comments. In this paper, we describe the flight simulator campaign to test and evaluate the control function for automatic and continuous deflection of flaps during the approach phase. Focus is given to workload and how it is influenced by energy management and the display design. The procedure is based on former flight simulator studies with the automatic thrust control nxControl [7].

Research mainly takes place at universities and research institutions, without the involvement of manufacturers or end-users. It is only at a late stage of development that problems in the implementation or assumptions that have led to a new idea become apparent. In principle, it is a good thing in research to think and try out problems free of strategic considerations and previous restrictions. On the other hand, the view from practice enables research to take into account problems that have not been considered so far.

The study has been accomplished with experienced airline pilots, and patterns and comments/ratings have been collected. Overall, the evaluation of the flight simulator campaign with airline pilots is based on the answers of the participating pilots on the basis of short interviews using previously defined questionnaires. In addition, the evaluation is based on protocols that were written down during the test. An evaluation of the flight parameter logs was published at AIAA Scitech 2023 [8].

2 The automatic continuously moving slats and flaps system

Deflection of flaps is a measure to change (increase) the camber of portions of the wing and thereby to increase the maximum lift coefficient, permitting the aircraft to decelerate and land at a low speed. Different configurations of flaps have different optimal points in terms of the corresponding operational airspeeds for (a) lowest sink rate and (b) best glide ratio (or highest aerodynamic efficiency), which are also a function of weight. Depending on the profile of the airspeed during the descent in the approach phase, the corresponding flaps configuration can be calculated for that speed to be the optimal speed for cases (b) or (a). Since normally the aerodynamic databanks are known for a number of stepwise flap configurations, linear interpolation among them for a continuous flap deflection can be applied. A detailed description of the Automatic Continuously Moving Slats and Flaps System (ACMSFS) function and the relevant flight mechanics is published in [6, 9]. In the following, the two developed flap control functions are shortly described in terms of energy management as well as the solution for the display design when these functions are active and the pilot possible interactions with respect to the actual position of flaps.

2.1 Energy management functions

The control law of the ACMSFS, which is based on the speed of the lowest sink rate, is called Paero,min in research papers as the name refers to the minimal aerodynamic power loss. For the study with the airline pilots, it is shown in the display as Drag Normal to represent the main effect during operations. This control law is activated by default, as it offers the greatest savings potential in terms of fuel consumption [9]. The second control law is based on the speed of the best glide (green dot speed) and is accordingly abbreviated VGD.Footnote 1 In the cockpit display this control law is shown as Extra Drag, as the flaps extend earlier, a greater deceleration is achieved. The VGD control law is recommended when there is a higher energy level in the approach, than the one necessary for landing, such as tailwind or higher approach speeds. In those cases, the pilot needs to decelerate the aircraft and therefore an increased drag is necessary. In addition to the flap regulation laws, there is also a recommendation for the extension of the landing gear as a new function of the ACMSFS. The landing gear recommendation takes into account the possible deceleration rates of the continuous flap system and marks the latest possible time for gear deployment to achieve a stabilised approach. The landing gear recommendation is calculated based on a standard approach without the use of air brakes or the reduction of the glide path angle, therefore, these drag-increasing elements remain as an operational margin for the pilots when they use them. For the study, the deceleration management, which includes the options to activate the change of the flap control law, to extend the landing gear early, or to use the air brakes, has been left as a pilot’s decision.

2.2 Display design

The standard implementation of the flap display is in the Electronic Centralized Aircraft Monitoring (ECAM) in the centre console of the cockpit. The flap display includes position indications of the flaps which are only valid for a stepwise movement of the slats and flaps (cf. Fig 1a). Therefore, parts of the display have been adapted. Firstly, the display of the fixed configuration levels has been changed to a percentage display and refers to the proportion of the total deflection angle (cf. Fig. 1b). In addition to the percentage display, a trend arrow is inserted to indicate whether the flaps are currently extending or retracting. The length of the trend arrow indicates the extension speed of the flaps. In addition, above the flap animation, it is indicated that the continuous flap function is active (CMSFS). The S and F in the same line indicate, where in the animation below the slat and flap position are shown and remained unchanged. Below the actual flap display, the display of the current control law (NormalDrag or ExtraDrag, as explained in Sect. 2.1) has been added. Additionally, the colour of the flap animation was changed to magenta, as magenta is the standard colour in the cockpit design for controlled functions.

Fig. 1
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Original ECAM display (a) and adjustments for continuous flap indications (b) implemented in SEPHIR flight simulator

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Fig. 2
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PFD display for gear deployment recommendation implemented in SEPHIR flight simulator

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Furthermore, the Primary Flight Display (PFD) was adapted. Since there is no more F- or S-Speed (mark in the PFD speed scale indicating a further flap deflection is advisable for the pilot), this display in the speed band of the PFD has been removed. Instead, when retracted, the airspeed at which the flaps begin to extend is displayed with an “E” (cf. Fig. 3) and when the flaps are fully extended, the airspeed at which the flaps begin to retract is marked with an “R” (not visible in Fig. 3). For energy management and to achieve a stabilised approach at 1000 ft, the PFD will display “Gear” in amber in the Flight Mode Annunciator (FMA) area to alert the pilot to the greater rate of deceleration required to achieve the stabilisation objective (cf. Fig. 2). This is achieved by lowering the gear by the pilot. The calculations are published in [8].

Fig. 3
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PFD speed scale with flap extension begin indication “E”

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3 Evaluation study

The ACMSFS function has been developed in cooperation with airline pilots and is to be evaluated extensively in this study by previously uninvolved pilots. To not only receive individual suggestions for improvement but to be able to carry out a numerical evaluation, the number of test participants was set at ten. The pilots’ flight experience ranged from 2, 000 to 27, 000 flight hours. Six of the pilots were captains and four were first officers. Table 1 summarises the flight experience and previous as well as current aircraft type ratings of the participating pilots. As the SEPHIR simulator is equipped with sidesticks all invited pilots had an active Airbus rating. The number of pilots and the limitation to pilots with Airbus ratings is according to the suggestions of Wilson and Riley for significant results [10].

Table 1 Flight experience of the participating airline pilots (Captain: CPT, First Officer: FO)
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The tests were carried out on the fixed-base flight simulator SEPHIR (Simulator for Educational Projects and Highly Innovative Research) of the Chair of Flight Mechanics, Flight Control and Aeroelasticity at the TU Berlin (cockpit view: Fig. 4). The flight simulator is equipped with a collimated visual system, which gives the pilot the feeling of distance. The flight simulator displays are integrated tablet PCs to enable different displays for different research projects. The Flight Control Unit (FCU) and some levers of the center panel are original aircraft parts. The thrust lever for both engines were linked. Therefore, thrust commands changed the thrust on both engines in the same manner. The flight simulation model corresponds to a typical short- and medium-haul airliner. It is a standard nonlinear, six-degree-of-freedom model and simulates in real time [11].

Fig. 4
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Cockpit view of the flight simulator SEPHIR at TU Berlin

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3.1 Approach procedures and simulation cases

The test series consisted of two different approach procedures, each of which was flown with three different masses and centre of gravity positions (CG). All approaches took place on runway 26R of Berlin Tegel EDDT, as this environment is available in the flight simulator.

The first approach scenario is a straight-in approach from a distance of 20 NM. The approach starts at an altitude of 2500 ft (airport elevation 122 ft) and an airspeed of 220 kt. Various waypoints are shown to the pilots on the navigation display. At a distance of 16 NM from the runway, the waypoint WPA is reached and the pilot decides with which control law of the ACMSFS the approach will be accomplished. The decision is based on the energy level of the current flight condition (altitude and airspeed) and the pilot’s experience (see Fig. 5, WPA).

The Decel waypoint marks the point where the airspeed is reduced to 170 kt. During the approach, the airspeeds are commanded by the pilots at the FCU and controlled by the Automatic Thrust (ATHR). The airspeed is kept constant until the waypoint VAPP. From the VAPP waypoint, the approach speed \(V_{APP}\) is commanded. The GSI waypoint marks the entry onto the glide path and serves as an orientation for the pilots. The flight path is controlled manually by the pilots using the sidestick during the whole approach. The speeds are regulated by the ATHR to achieve high accuracy and consistency between pilots. The approaches are flown without wind and visibility restrictions to minimize interpretation variables. Standard ISA conditions are applied. This approach is flown with different centre of gravity positions and weights. Table 2 summarizes the four approaches of the first simulation block. All tests are conducted with the ACMSFS active, as a comparison between the standard slat/flap movement and the new ACMSFS system has already been evaluated in [12]. All tests have always been conducted in the same order because the approach with a very light aircraft without training on the capabilities of ACMSFS is not possible. Additionally, at the end of the first simulation block, an approach is simulated in turbulent conditions with headwind and cloud base in 1000 ft. The introduction of turbulence and headwind serves to mask a failure case test. As soon as the flaps are 50% extended, the flaps of the right-wing lock in this position. All other flaps can reach their fully extended position so that there is an asymmetry in the flap positions between left and right wing. The pilots should perform the fourth approach without a go-around to investigate how the failure condition of the asymmetric flap setting affects the continuous flap system, the new cockpit displays and the flight behaviour.

The second approach scenario is a trombone approach, as flown at London Heathrow, for example. The approach is 30 NM long and the aircraft initiates at 7000 ft with 180 kt. At the Descent waypoint, a continuous descent approach begins with a descent rate of 1000 ft/min. At the FAP the transition to the glide slope takes place, this should be flown without level-off. The lateral flight path is flown using the autopilot navigation controller to minimise deviations in the approaches. The vertical flight profile is flown by the pilots using the sidestick or the vertical descent rate during the whole approach phase. Three approaches are made with this setting. Two of them with Maximum Landing Mass (MLM) and two different CG positions (forward: fwd; middle: mid) and one with Operational Empty Mass (OEM) plus two tons of fuel and aft CG position. The chosen conditions respect the critical combinations of CG position and masses. As with the first approach scenario, the flights take place in ISA standard conditions without wind and clouds. Finally, a manual approach takes place to increase the pilots’ workload. For this approach, the cloud base is at Minimum Decision Altitude (MDA). Table 3 summarises all approaches and conditions of the second simulation block (Fig. 6).

Fig. 5
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Vertical flight path of the straight-in approach

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Fig. 6
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Lateral flight path of the trombone approach

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Table 2 Simulation cases and conditions for the straight-in approach
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Table 3 Simulation cases and conditions for the trombone approach
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3.2 Questionnaire

The evaluation in this paper is based on the information provided by the pilots who answered the same questionnaire after each test flight (cf. A). In addition to the questions during the trials, a debriefing with more general questions was held at the end (cf. B). The answers from the debriefing are also included in the evaluation. An evaluation of the flown flight parameters is carried out exclusively for validation and comparison of the pilots’ answers with the actual flight situation. A more detailed evaluation of the flight parameters is given in [8].

The questionnaire after each approach consists of nine questions. First, three questions assess the approach itself, asking about differences from normal operations and examining what worked well or not so well during the respective approach. Then the pilots are asked to rate the workload of the approach in comparison to the same approach with a standard flap setting. The rating is based on a scale of 1 to 10, where 5 corresponds to an unchanged workload, 0 to a much lower workload and 10 to a much higher workload. This custom rating scale has been choosen, as the pilots should not rate the workload of the approach itself, which can be rated by NASA TLX or Bedford rating scale. The important point in this study is the comparison to a flight as the pilots would experience it during line operations with standard flaps. The changes to the system are then discussed in more detail. The pilots are asked to rate how often, they checked the flap position to have an indicator of the pilots’ confidence in the ACMSFS. The following three questions refer to the energy management during the approach and how the pilots dealt with the extension of the landing gear in this context and whether and how they used the change in the control law. Finally, the pilots were asked to assess the adjustments to the displays. The following section evaluates the results of the pilots’ responses.

4 Results

The evaluation of the questionnaires in this paper is based on the answers of the pilots in the areas of workload, energy management and display design. As the answers of the pilots represent subjective opinions, a comparative classification is made with the results of the time records of physical parameters that were created during the flight simulator campaign.

4.1 Workload

The workload for the pilots is assessed by the pilots themselves. The pilots are asked to rate the workload per approach in comparison to the same approach with a stepwise flap setting, for which they are responsible themselves. Figure 7 shows the results of the self-assessment. The value 5 corresponds to no change in workload, while 1 means a much lower workload and 10 a much higher workload. In the box plot the red line indicates the median per approach scenario/flight number. The box around the median corresponds to the lower and upper quartile. The black bars at the bottom and the top of the box represent the minimum and maximum ratings of the pilots per approach scenario. Only if a rating is more than 1.5 times bigger or smaller than the quartiles it is marked as a spike with a red cross. In the median, the pilots indicated a lower or equal workload for approaches with the continuous flap system for all approach scenarios compared to a standard approach with a stepwise flap setting by themselves. Approaches No. 3 and 7 are approaches with a low approach mass and place the greatest demands on the pilots, and even in this approach scenarios, the pilots have considered in the median that the workload has not been increased. In the first approach number 2, the pilots have not yet become familiar with the system and the new function, the perception is a relief of workload with the automatic function. Likewise, on approach No. 8 with a high overall workload due to a manual Continuous Descent Approach (CDA), the pilots perceive the continuous flap function as a considerable relief on the workload. Since approach 4 was flown with a failure case of asymmetric flap setting and without a go-around, it does not correspond to the pilots’ standard procedure with a failure case and it was not possible for the pilots to make a meaningful workload comparison with the approach of the study. Still the failure case was important for the evaluation of the display design and information management and presentation in the cockpit. The analysis of the workload rating with regard to the pilot experience level showed no influence (cf. Fig. 8). Only the two most experienced pilots behaved different than all the others. One of them just retired and was very sceptical with the new system. The other well-experienced pilot works as an instructor and was not stressed by the system or situation at all.

Fig. 7
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Workload classification of the pilots compared to the same approach with standard flap setting by the pilots’ (1 less, 5 equal, 10 increased). Training flight No. 01 is not included in the examination

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Fig. 8
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Workload classification of the pilots versus the experience level of the pilots in flight hours

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In addition to assessing the level of workload, pilots needed to evaluate how often they checked the flap position in the cockpit centre console. About three quarters of the pilots stated that they rarely sporadically checked the flap position. A quarter of the pilots said they looked at the flap position more frequently. 50% of the pilots who checked the flap setting more frequently stated that they checked the flap positions out of curiosity and interest. The other half of the pilots who checked the flap setting more frequently stated that they checked the pitch and thrust settings with the flap positions for plausibility. The frequency of checking the flap display was reduced as the system became more familiar to the test pilots. During the last test approaches, 90% of the pilots checked the flap setting at most during speed changes and when reaching stabilisation altitude.

4.2 Energy management

The pilots were asked to classify the energy management for each approach. Energy management is defined as the desired speed and altitude reduction, as well as if and how easily the stabilisation altitude was reached. To reach stabilisation altitude, all of the following parameters must be achieved to an altitude of 1000 ft above ground level (AGL):

  • \(V_{\text {app}} - 3\,\text {kt}< V < V_{\text {app}} + 10\,\text {kt}\),

  • landing gear fully extended,

  • final approach flap position achieved,

  • deviation from glide path \(< 1\) dot, and

  • adequate thrust.

According to Fig. 10, for a majority of the pilots, energy management worked adequate to good for heavy aircraft configurations (approaches 2, 5, 6 and 8). For approach cases 3 and 7 with very light aircraft configuration, the energy management was not acceptable for about half of the approaches (cf. Fig. 11). Figure 9 summarizes all achieved stabilisation altitudes of all pilots for all approaches in a box plot. In Sect. 4.1 is an explanation of box plots. Comparing the results of Figs. 10 and 11 with Fig. 9, where all stabilisation altitudes per approach are shown, it becomes clear that these statements refer primarily to approach case 7. For that case, only one pilot succeeded in achieving a stabilised approach at 1000 ft AGL. This was possible because he was the only pilot who used speed brakes during large parts of the approach. The pilot was one of the most experienced pilots during the study and works as an instructor. All other pilots didn’t want to use speed brakes, because they normally do not need speed brakes for a standard approach. According to some pilots, there are airlines that accept stabilisation at 800 ft AGL if there is a relatively high-speed instruction from Air Traffic Control (ATC), up to approximately 4 NM before reaching the runway. Since this was the case in the simulator tests, under half of the pilots rate the energy management during the approaches with low approach mass as adequate to good.

Fig. 9
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Stabilisation altitudes for all approach scenarios

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Fig. 10
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Energy management evaluation for flight cases 2, 5, 6 and 8

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Fig. 11
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Energy management evaluation for flight cases 3 and 7

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4.3 Display design

The changes in the cockpit display design to show the system state of continuous flap operation are explained in more detail in Sect. 2.2. Pilot comments and annotations differ between the PFD and the ECAM display.

Primary Flight Display

The “R” indication for retraction of the flaps is recognized as useful for go around (GA) cases by three of the pilots. Whereas four pilots mentioned that the “E” indication (for first flap extension) gives no additional information as during the flown approaches the indication is identical to Green Dot display. One pilot considered the information misleading, since “E” and “GD” in PFD were on top of each other. Another pilot summarized that the indication of “E” and “R” have no added value and therefore distract from other information. Four other pilots found the indication helpful or informative, but not absolutely necessary. Two pilots did not perceive the “R” and “E” because it was not yet included in their scan and monitoring scheme.

The “Gear” message included in the PFD display, which allows a stabilized approach at 1000 ft, was in most of the approaches not indicated, since for almost all cases, the pilots deployed the landing gear prior to the message. Three pilots deployed the gear just in the second when the message appeared, so they recognized it as suitable for the approach planning. An acoustic signal was suggested by one test pilot, but not implemented due to the risk of confusion with the already existing warning "Too low gear", which sounds in the cockpit in case the Ground Proximity Warning System (GPWS) detects an unsafe terrain clearance without the gear extended. At the moment, the indication in the PFD is coloured in amber. One pilot suggested to change the colour to green because amber is an indication for a failure.

ECAM Display

The ECAM Display in the centre of the cockpit was clearly recognisable for all of the participating pilots. Some pilots criticised the fact that the name of the continuous flap function “CMSFS” indicated above the flap animation is confusing, since it adds no further information as the magenta colour of the animation already shows that the system is managed by the computer. The suggestion is to only show the name of the system in the ECAM display if it is not working properly. Additionally, the “Normal Drag” indication raised confusion for a few of the participating pilots. The suggestion was to only show “Extra Drag” when it is selected. One pilot found the design unfamiliar and misleading. He suggested to place the percentage in the middle of the display because he thought it indicates only the slat position. The same pilot also suggested to change the colour in the engine display, when the slat and flaps start moving instead of the “E” indication in the PFD. The display of the slat/flap position as a percentage of the maximum deflection was rated very differently by the pilots. Three pilots found the percentage display difficult to interpret or not meaningful. One of these pilots suggested limiting the display to increments of ten. Three other pilots found the percentage of flap position meaningful and especially helpful in abnormal situations to select safe airspeeds based on table values. The safe airspeeds per percentage deflection should be made available to pilots as a rule of thumb or manual. The pilots who did not like the percentage indication, focused more on the animation to better assess slat and flap positions and rated it as meaningful. Those pilots in favour of a percentage display, found the animation less relevant. Most of the pilots did not pay attention to the trend arrow of the flaps, because it was noticed to be a bit small. The behaviour was clear for all pilots, but as the slat/flap position is coupled to the airspeed, the airspeed trend in the PFD is indicating quite the same and therefore more tangible for the pilots. Most of the pilots were in favour of a separate display when full configuration is reached. One suggestion was to display the landing configuration in green on the landing checklist.

Additional Necessary Information on Flap System Status

In the discussion after all flight tests the pilots suggested improvements and additional information that might be important to know during flight.

For one pilot the lack of correlation between percentage and speed (e.g. S and F in PFD) was a drawback and he wishes a correlation to check slat/flap positions. For all other pilots, this was no issue, because maximal and minimal airspeeds in the speed band of the PFD are adjusted according to the continuous slat/flap position, which was considered as sufficient information. Additionally, the flap travel and trend arrow can be implemented in the PFD, as it is already in some new aircraft. The final position of the flaps should be known to the pilots. Currently, there is only the Full configuration as flap position, which does not change below an altitude of 1000 ft. Three pilots would like this to be clearly communicated and marked on the display. One pilot would also like to hear a callout such as "Final Flaps". In addition, eight of the pilots would like to be able to set the landing configuration, as they report from line operations that in turbulence, for example, they often land with a lower flap setting to have energy reserves for a possible go-around manoeuvre. This setting could possibly be entered via the Flight Management System or as suggested by one pilot with a rotary knob (implemented like this in some Boeing aircraft), which could also serve as a backup system, which was thought to be necessary for certification. In failure cases, seven pilots would have liked more information about the error displayed in the ECAM display. The pilots’ request arises from the fact that checklists and error lists are displayed in ECAM during line operation. This is currently not the case in the flight simulator SEPHIR. Finally, two pilots were confident that every necessary information is displayed clearly enough, and a process of training for the familiarisation is necessary.

4.4 Pilots’ remarks on the ACMSFS

The pilots were asked for their remarks on the effectiveness of the control laws and working with the new ACMSFS during the debriefing. The most experienced and the least experienced pilot were the most critical of the new system. This was because the most experienced pilot preferred less automation in the cockpit. While the least experienced pilot was not yet familiar with the standard approach procedures and thus required a lot of attention to complete the approach task. For two pilots, the effect of the Extra Drag law was too small. Other pilots noted that the ACMSFS works well when the spoilers are used appropriately. Half of the pilots expressed a desire for a checklist outlining the sequence of spoiler usage, control law changes, and landing gear extension. Almost all pilots positively evaluated the improvement in flight economy and the reduced ballooning effect on control achieved by the ACMSFS. All pilots emphasized the ease of operation during approach scenarios with high air traffic. Additionally, one pilot mentioned that the automation of flaps represents an overdue and consistent implementation of the control philosophy in new commercial aircraft.

5 Conclusion

The results of the survey of the simulator test campaign with ten airline pilots show that the advantages of fuel saving have not been accompanied by an increase in the workload by most of pilots and scenarios tested. Even in the most challenging approach scenarios, the average of pilots noticed a reduction or at least no increase in workload. The results are independent of pilot experience levels. For future work, it is planned to develop a guide of actions for pilots, so that the order of using flaps, spoilers and landing gear to decelerate during the approach can be used in a fuel and noise-minimising manner. It is also recommended to implement the pilots’ suggestions to adapt the display of the PFD and ECAM in order to achieve a clear design. In the PFD the main point is the colour change of the “Gear” indication to green. In the ECAM the “CMSFS” indication and the trend arrow shall be removed as well as the “Normal Drag” indication, as these information add no value. Two further important comments by the pilots are the indication that the landing configuration is reached on the landing checklist in green and the possibility to adjust the final landing configuration by the pilots during approach briefing. The principle function of the ACMSFS with two control laws should be retained, as well as the landing gear display since the procedural trigger of manual flap operation for the pilots is no longer present.