Electronic/electric technology benefits study

The benefits and payoffs of advanced electronic/electric technologies were investigated for three types of aircraft. The technologies, evaluated in each of the three airplanes, included advanced flight controls, advanced secondary power, advanced avionic complements, new cockpit displays, and advanced air traffic control techniques. For the advanced flight controls, the near term considered relaxed static stability (RSS) with mechanical backup. The far term considered an advanced fly by wire system for a longitudinally unstable airplane. In the case of the secondary power systems, trades were made in two steps: in the near term, engine bleed was eliminated; in the far term bleed air, air plus hydraulics were eliminated. Using three commercial aircraft, in the 150, 350, and 700 passenger range, the technology value and pay-offs were quantified, with emphasis on the fiscal benefits. Weight reductions deriving from fuel saving and other system improvements were identified and the weight savings were cycled for their impact on TOGW (takeoff gross weight) and upon the performance of the airframes/engines. Maintenance, reliability, and logistic support were the other criteria

An in-flight interaction of the X-29A canard and flight control system

Many of today's high performance airplanes use high gain, digital flight control systems. These sytems are liable to couple with the aircraft's structural dynamics and aerodynamics to cause an aeroservoelastic interaction. These interactions can be stable or unstable depending upon damping and phase relationships within the system. The details of an aeroservoelastic interaction experienced in flight by the X-29A forward-swept wing airplane. A 26.5-Hz canard pitch mode response was aliased by the digital sampling rate in the canard position feedback loop of the flight control system, resulting in a 13.5-Hz signal being commanded to the longitudinal control surfaces. The amplitude of this commanded signal increased as the wear of the canard seals increased, as the feedback path gains were increased, and as the canard aerodynamic loading decreased. The resultant control surface deflections were of sufficient amplitude to excite the structure. The flight data presented shows the effect of each component (structural dynamics, aerodynamics, and flight control system) for this aeroservoelastic interaction

Preliminary design studies of an advanced general aviation aircraft

The preliminary design results are presented of the advanced aircraft design project. The goal was to take a revolutionary look into the design of a general aviation aircraft. Phase 1 of the project included the preliminary design of two configurations, a pusher, and a tractor. Phase 2 included the selection of only one configuration for further study. The pusher configuration was selected on the basis of performance characteristics, cabin noise, natural laminar flow, and system layouts. The design was then iterated to achieve higher levels of performance

Stability Enhancement for Single-Loop Voltage Controlled Voltage-Source Converters with LC-Filter

Voltage controlled voltage source converters (VSCs) have been widely applied in microgrids, uninterruptible power sources, smart transformer and 400 Hz ground power units for airplanes, etc. An LC filter is generally adopted to attenuate high frequency switching harmonic and to improve the qualities of output voltage and current for grid or loads. Nevertheless, VSCs have to trade-off between the stability characteristic and the ability of switching harmonics suppression when a single-loop voltage control method is adopted. In general, the resonant frequency ω r of LC filter should be less than 1/4 of sampling frequency ω s to ensure sufficient attenuation of the switching harmonic. However, ω r should be higher than 1/3 of ω s for the system stability when a proportional-resonant (PR) controller with a positive proportional gain is implemented. This paper proposes a feedback of modulation voltage (FMV) control design method for single-loop control to ensure stability condition in a higher frequency range and good switching harmonics suppression at the same time. Finally, simulation results are provided to verify the effectiveness of the proposed method

Aircraft electromagnetic compatibility

Illustrated are aircraft architecture, electromagnetic interference environments, electromagnetic compatibility protection techniques, program specifications, tasks, and verification and validation procedures. The environment of 400 Hz power, electrical transients, and radio frequency fields are portrayed and related to thresholds of avionics electronics. Five layers of protection for avionics are defined. Recognition is given to some present day electromagnetic compatibility weaknesses and issues which serve to reemphasize the importance of EMC verification of equipment and parts, and their ultimate EMC validation on the aircraft. Proven standards of grounding, bonding, shielding, wiring, and packaging are laid out to help provide a foundation for a comprehensive approach to successful future aircraft design and an understanding of cost effective EMC in an aircraft setting

Systems study for an Integrated Digital-Electric Aircraft (IDEA)

The results of the Integrated Digital/Electric Aircraft (IDEA) Study are presented. Airplanes with advanced systems were, defined and evaluated, as a means of identifying potential high payoff research tasks. A baseline airplane was defined for comparison, typical of a 1990's airplane with advanced active controls, propulsion, aerodynamics, and structures technology. Trade studies led to definition of an IDEA airplane, with extensive digital systems and electric secondary power distribution. This airplane showed an improvement of 3% in fuel use and 1.8% in DOC relative to the baseline configuration. An alternate configuration, an advanced technology turboprop, was also evaluated, with greater improvement supported by digital electric systems. Recommended research programs were defined for high risk, high payoff areas appropriate for implementation under NASA leadership

Integrated Application of Active Controls (IAAC) technology to an advanced subsonic transpot project-demonstration act system definition

The 1985 ACT airplane is the Final Active Controls Technology (ACT) Airplane with the addition of three-axis fly by wire. Thus it retains all the efficiency features of the full ACT system plus the weight and cost savings accruing from deletion of the mechanical control system. The control system implements the full IAAC spectrum of active controls except flutter-mode control, judged essentially nonbeneficial, and incorporates new control surfaces called flaperons to make the most of wing-load alleviation. This redundant electronic system is conservatively designed to preserve the extreme reliability required of crucial short-period pitch augmentation, which provides more than half of the fuel savings

Initial results from flight testing a large, remotely piloted airplane model

The first four flights of a remotely piloted airplane model showed that a flight envelope can be expanded rapidly and that hazardous flight tests can be conducted safely with good results. The flights also showed that aerodynamic data can be obtained quickly and effectively over a wide range of flight conditions, clear and useful impressions of handling and controllability of configurations can be obtained, and present computer and electronic technology provide the capability to close flight control loops on the ground, thus providing a new method of design and flight test for advanced aircraft

Design of DC-Link VSCF AC Electrical Power System for the Embraer 190/195 Aircraft

A proposed novel DC-Link VSCF AC-DC-AC electrical power system converter for Embraer 190/195 transport category airplane is presented. The proposed converter could replace the existing conventional system based on the CSCF IDGs. Several contemporary production airplanes already have VSCF as a major or backup source of electrical power. Problems existed with the older VSCF systems in the past; however, the switched power electronics and digital controllers have matured and can be now, in our opinion, safely integrated and replace existing constant-speed hydraulic transmissions powering CSCF AC generators. IGBT power transistors for medium-level power conversion and relatively fast efficient switching are used. Electric power generation, conversion, distribution, protection, and load management utilizing VSCF offers flexibility, redundancy, and reliability not available with a conventional CSCF IDG systems. The proposed DC-Link VSCF system for E190/195 delivers several levels of 3-ϕ AC and DC power, namely 330/270/28 VDC and 200/ 115/26 VAC utilizing 12-pulse rectifiers, Buck converters, and 3-ϕ 12-step inverters with D-Y, Y-Y, and Y-D 3-ϕ transformers. Conventional bipolar double-edge carrier-based pulse-width-modulation using three reference AC phase signals and up to 100 kHz triangular carriers are used in a manner to remove all even and many odd super-harmonics. Passive low-pass filters are used to remove higher harmonics. The RL AC loads are active in connection with the synchronous and induction AC motors and also include passive AC loads. The overall power factor exceeded 85%. Total harmonic distortions for voltages and currents are below 5%, thus satisfying the MIL-STD-704F and the IEEE Std. 519 power-quality standards, while avoiding the need for active filters. Several PI and PID controllers that regulate synchronous generator DC excitation and inverter banks were designed and tuned using the continuous–cycle tuning method to offer required performance and stability of the feedback loop. Mathworks’s SimulinkTM software was used for simulation of electrical components and circuits. Several critical scenarios of aircraft operations were simulated, such as go-around, to evaluate the transient behavior of the VSCF system