Karolin Schreiter

nxControl Instead of Pitch-and-power : A Concept for Enhanced Manual Flight Control

AbstractA command system for manual control of the longitudinal load factor in flight path direction of an aircraft is designed that completes existing flight control command systems (e.g. with sidesticks that command normal load factor). The system is called nxControl. It aims to assist pilots during manual flight by reducing the workload for monitoring flight parameters as well as for controlling thrust and airbrakes. Important for the nxControl concept is the direct flight mechanical relation between longitudinal load factor and changes of the total aircraft energy. This paper presents the system concept and a prototype realization. The nxControl system consists of the control law that combines the actuation commands for engines and airbrakes, a new input device for the longitudinal load factor command and augmented display elements informing pilots about aircraft energy states to assure situation awareness. In order to investigate the feasibility of the concept as well as to evaluate consequences on human performance, a flight simulator study with airline pilots was conducted. The nxControl prototype was used by the pilots as expected. Changes in instrument scanning behaviour and thrust lever usage confirmed this. After just a short familiarization and practice, the pilots were able to perform standard flight tasks with nxControl without exceeding given tolerance limits. So, the results provide first evidence for the feasibility of the concept.

Implementing Energy Status in Head-Down Cockpit Displays Impact of Augmented Energy Information on Pilot’s Performance

It is safety critical for pilots to be aware of the aircraft’s energy state in terms of proper altitude and airspeed. A loss of energy awareness is an important human factors issue in modern civil aircraft. In order to maintain the energy awareness and support the manual flying skills, several cockpit display concepts suggest to augment the current energy status of the aircraft on primary flight displays in terms of the total energy angle. An experiment was carried out to determine which effect this additional energy information has on pilots’ flight path control, instrument scanning, and situation awareness. Outcomes of the study show a significant shift of the scanning pattern from airspeed, altitude scale, and engine parameter towards the center of the primary flight display with unchanged situation awareness. In addition, pilots are better able to maintain given speed targets.

nxControl: Ground Mode for Manual Flight Control Laws with Longitudinal Load Factor Command

More complex flight trajectories and rising requirements on flight precision increase pilots’ workload during manual flight. The control augmentation system nxControl supports manual control by enabling pilots to command the longitudinal load factor \(n_x\) instead of engine thrust and spoiler deflections in flight. The load factor \(n_x\) is equivalent to the total energy angle and is directly influenced by thrust and aerodynamic drag. The system allows for higher precision with lower workload during manual flight. In order to prevent mode switching problems in the time-critical and demanding situations of take-off and landing the system was extended with a ground mode for aircraft control on ground and the transition phases. It controls forward thrust, spoilers, wheel brakes, and thrust reverser. This paper describes the design of the feedback controller considering common take-off and landing procedures as well as the pilots’ view. The resulting control laws of the ground mode as well as the new human-machine interface are presented. In a flight simulator study with seven airline pilots, the feasibility of the nxControl extension was tested in landing, taxi, and take-off scenarios. The results show, that the pilots were able to precisely manage the used runway length at landing. At taxi, the pilots could manage taxi speed with low command input frequency. The general performance during the take-off process, in particular in case of engine failure, was not influenced by nxControl.

Manual flying and energy awareness

In order to enable pilots to better maintain energy awareness and energy management in manual flight, a new concept has been proposed, which transfers the demand control principle of fly-by-wire control laws also to the control of thrust. It includes a total-energy-related augmented thrust controller combined with a modified cockpit instrumentation enriched by specific energy displays. In order to empirically evaluate the human performance consequences of this new approach, an experimental study was conducted in a flight simulator investigating its effects on pilots’ performance, workload, and situation awareness. A total of 24 commercial aircraft pilots performed a landing and approach on a complex flight trajectory with and without the new system elements. The results confirm the expected beneficial effects of the new system on flight precision and lowered effort involved in thrust control as compared with conventional raw data flying. No negative side effects, for example, impaired situation awareness, were found.