Holger Spangenberg

Challenges for Health Monitoring of Electromechanical Flight Control Actuation Systems

Flight control systems of civil aircraft have undergone huge developments in the last decades. The current more/all electric aircraft concepts lead to the replacement of the hydraulic actuators in the primary flight control systems by electromechanical systems. Integrating electromechanical systems in safety critical applications implies three main challenges: (a) the detection of all fault cases which could lead to a safety critical state, (b) finding measurement parameters capable to detect faults, and (c) the development of algorithms to detect faults under all flight conditions. Putting the scope on the health monitoring of the mechanical components of a direct drive actuator, a new technology based on piezoresistive thin film sensors (TFS) is presented and its potential shown by using defective ball bearings as an example.

Power budget and system performance analysis of the pof link for future avionic applications

Statistical analysis provided an accurate estimate on the influence of different connectors in the link performance. More link performance measurement data and test patterns for different cases under extended and normal operating conditions have been analyzed.

Hardware-in-the-Loop Simulation with Flight Control Actuators

High complexity of modern airplanes and the permanently fast growth of market must not lead to rising numbers of accidents. Especially very large airplanes like the A380 are in the focus of public; a catastrophic failure which is specified with a maximum of 1*10 -9 total losses per flight hour would not only be catastrophic for this aircraft - it could have major influence in the acceptance of aviation in public. For a safe and comfortable flight, a fundamental part of the aircraft is the flight control system. Detailed tests of this system must be carried out for new flight control solutions to increase safety of the aircrafts. Although lots of tests can be performed in computer simulation today, test rigs with hardware-in-the-loop are indispensable for flight critical systems. A test rig like the one described here can help to solve problems of future flight control systems and to recognize problems in the early development process.

Fault detection and classification for flight control electromechanical actuators

Future aircraft architectures will incorporate more energy-efficient electromechanical actuators (EMA) for flight controls actuation. Development of reliable health monitoring techniques for EMAs promises to maintain or even increase the overall availability and safety of these new aircraft designs. When it comes to EMAs and similar mechanisms, certain fault types clearly manifest themselves through loss of functionality. Other faults, referred to as latent, do not immediately result in a significantly compromised actuator performance, thus making them challenging to detect. This paper presents a new vibration-based hybrid technique for detecting latent EMA faults without needing an initial stage of fault feature learning. The two faults considered in the study are a high-criticality jam and a low-criticality spall (metal flaking) in the actuator ballscrew mechanism. The actuator position is used to resample variable-speed vibration measurements of a single accelerometer into constant-rate measurements. A set of health characterization signatures is derived theoretically based on the EMA ballscrew kinematics. These theoretical signatures are compared with the signatures extracted from vibration signals measured experimentally on the EMA test articles. The vibration signatures approach is also compared to the diagnostic approach based on EMA motor current measurements. The ability to detect and classify latent faults early as high-or low-critical can improve maintenance planning and increase aircraft dispatch reliability. The technique has been validated on fault-injected data sets collected on the NASA Ames Research Center Flyable Electro-Mechanical Actuator (FLEA) test stand.

Polymer optical fiber splicing technique for avionic applications: First step towards standardization

This investigation shows the temperature sensitivity of the POF splices restricted their use specifically to non-critical applications. However, avionic POF splice can be realized in the future with suggested modification.

Safety and reliability analysis of wireless data communication concepts for flight control systems

Wireless communication systems take the place of wired communication systems in various fields to overcome cable-based problems and their limitations. Avionics is one of the fields in which aging and damaging of cables can cause severe accidents. The most important advantages of wireless systems in avionics are weight reduction, resulting in less fuel consumption, flexibility, ease of layout, maintenance and modification. In this contribution, replacement of wired-based safety-critical data communication systems in an aircraft with wireless systems, in terms of safety and reliability is discussed. Under the scope of this work, the conceptual baseline study on wireless flight control systems is carried out. A point-to-point data transmission for a wireless flight control network is simulated considering safety constraints. Therefore, relevant transmission parameters of the wireless system are evaluated, which improve safety level of the wireless transmission. To assess the safety and reliability of the system, failure sources are studied and effects of most influential environmental disturbing factors on the simulated data link are investigated. As a result, effects of changing environmental conditions on the wireless data link for the concept of flight control system are analyzed.

Investigation on harsh environmental effects on polymer fiber optic link for aircraft systems

To integrate polymer fiber based physical layer for avionic data network, it is necessary to understand the impact and cause of harsh environments on polymer fiber optic components and harnesses. Since temperature and vibration have a significant influence, we investigate the variation in optical transmittance and monitor the endurance of different types of connector and splices under extreme aircraft environments. Presently, there is no specific aerospace standard for the application of polymer fiber and components in the aircraft data network. Therefore, in the paper we examine and define the thermal cycling and vibration measurement set up and methods to evaluate the performance capability of the physical layer of the data network. Some of the interesting results observed during the measurements are also presented.

Integrating polymer optical fibers in civil aircraft: Enviromental requirements and challenges

The potential of polymer optical fiber (POF) and its link components in short distance data communication has been well established by the automotive (e.g. media oriented system transport bus) and telecommunication industries. Avionics networks can also be considered as short distance data communication as they have a limited size with a maximum length of 100 m between the nodes. This paper discusses the challenges and options in integrating commercial POF link and its passive/active components to the critical as well as non critical data communication in commercial aircraft. The paper will focus particularly on the relevant firm environmental requirements that have to be fulfilled to assure the reliability and safety of the commercial aircraft data communication network. Further, characterisation of POF will be analyzed in detail based on MIL STD 1678/TIA 455 series and compliance with RTCA/DO 160E will also be evaluated in detail.

Failure detection, identification and reconfiguration - applications for a modular iron bird

The permanently fast growth of airline market must not lead to rising numbers of accidents. To improve aircraft safety, pilot workload has to be reduced especially in critical situations. This paper describes the system architecture of a new test rig to evaluate the effects and advantages of new concepts in the area of flight control. A first application of the iron bird to demonstrate its potential deals with the evaluation of a solution for reconfiguration: elevator failures are compensated by using a new Trimmable Horizontal Stabilizer Actuator concept with higher dynamics, which can be integrated in modern airliners. The test rig enables research on the interactions of different subsystems for failure detection, identification and reconfiguration of the modified controller by using Hardwarein-the-Loop tests of flight control actuators in combination with pilot evaluations in a cockpit simulator.

Simulation Examples of Military Transport Issues in Research Simulator

Modern military transport for increasing missions require a large variety of new functions and capabilities. Conventional tasks of tactical and strategic troop transport are augmented by requirements arising from peace keeping and humanitarian missions for example. A key element for safe and cost efficient development such future transport aircrafts is the use of advanced but pragmatic simulation tool. To recognize problems early in the design process, simulators with the capability to quickly and easily reflect these novel flight control functions are highly advisable. The present paper describes various research activities and prerequisites which such a simulation tool. An initial chapter is devoted to representative aircraft dynamics models and other simulation features. The following illustration depicts real terrain elevation data. SRTM data from one of the Space Shuttle missions has been used to simulate this mountainous terrain.