Propulsion Controlled Aircraft Research Articles

Robust thrust-only control of a civil transport aircraft with vertical tail damage

Abstract Thrust-only control of a jet transportation aircraft is also referred to as propulsion-controlled aircraft (PCA). It may be adopted as an alternative to using propulsive force to provide a certain level of control capability in case of failure of the aircraft's conventional control system. Previous PCA research was mainly concerned with control surface malfunctions such as free-floating and locked-in-place situations. On the other hand, structural damage to the aircraft control surfaces makes it necessary for PCA study and results in significant challenges due to the damage-induced aerodynamic and geometric parameter deviations. This paper presents a damage-tolerant control system design for aircraft with vertical tail damage. An H∞ loop transfer recovery (LTR) technique is applied to address the stability recovery and robustness of performance in maintaining safe flight operation of a damaged aircraft. Modelling of the damaged flight dynamics and control design is presented followed by numerical...

Flight Control System Design for Propulsion-Controlled Aircraft

The loss of an aircraft's primary flight controls can lead to a fatal accident. However, if the engine thrust is available, controllability and safety can be retained. This article describes flight control using engine thrust only when an aircraft has lost all primary flight controls. This is a kind of flight control reconfiguration. For safe return, the aircraft must first descend to a landing area, decelerate to a landing speed, and then be capable of precise flight control for approach and landing. For these purposes, two kinds of controllers are required: a controller for descent and deceleration and a controller for approach and landing. The former controller is designed for longitudinal motion using a model-following control method, based on a linear quadratic regulator. The latter is designed by an H∞ state-feedback control method for both longitudinal and lateral-directional motions. Computer simulation is conducted using linear models of the Boeing 747. The results indicate that flight path control, including approach and landing, is possible using thrust only; however, speed control proves more difficult. However, if the horizontal stabilizer is available, the airspeed can be reduced to a safe landing speed.

Nonlinear Fly‐By‐Throttle H∞ Control Using Neural Networks

ABSTRACTA neural network approach to gain scheduling H∞ controllers for propulsion controlled aircraft (PCA) systems is introduced. The PCA system is applied to backup control of aircraft experiencing control surface failure. The H∞ technology is applied to the problem of matching the crippled aircraft and the nominal model. Various H∞ controllers at various flight conditions are used to train radial basis function networks (RBFN), which can then be used as the nonlinear controller. Simulation on an L‐1011 under fly‐by‐throttle control demonstrates that the RBFN controller can stabilize the crippled airplane to obtain the desired model and possesses robustness against the engine delay.

Propulsion control of crippled aircraft by H/sub ∞/ model matching

An H/sub /spl infin// method for propulsion controlled aircraft (PCA) design is introduced. The PCA system is adopted for emergency fly-by-throttle control of an airplane with multiple control surface failure. The H/sub /spl infin// methodology is applied to the problem of matching by dynamic compensation the throttle-actuated crippled aircraft and the nominal control-surface-actuated aircraft model. The design procedure is used to synthesize model matching H/sub /spl infin// controllers for an L-1011, a commuter airliner, and a thrust vectoring aircraft model in longitudinal motion and an L-1011 model in lateral motion. Simulation results demonstrate that the concept is workable.

From Sioux City to the X-33

The history of the “Propulsion Controlled Aircraft (PCA)” problem is reviewed. While there had been repeated warnings that life-threatening hydraulic failure in a modern airliner can occur despite an estimated probability of 10 −9, only after the Sioux City accident was the possibility of using some automatic fly-by-throttle back-up control system for crippled airplane seriously considered. Several different schemes to help pilots fly hydraulically depleted aircraft by using collective and differential thrust of the engines will be reviewed. Special attention will be devoted to the system theoretic “model matching” methodology, in which the propulsion controlled aircraft is compensated so as to respond as if it were under normal aerodynamic control. Applications of these concepts to Unhabited Air Vehicles (UAV's) will also be considered. Finally, it will be shown how the propulsion control concepts can be extrapolated to the X-33, the reduced scale demonstration vehicle of the new space shuttle, the engines of which cannot be gimballed so that differential thrust instead of thrust vectoring has to be used. The latter application is more in the spirit of “reconfigurable control” and is based on the novel methodology of Linear Set Valued Dynamically Varying (LSVDV) control.

From Sioux City to the X-33

The history of the “Propulsion Controlled Aircraft (PCA)” problem is reviewed. While there had been repeated warnings that life-threatening hydraulic failure in a modern airliner can occur despite an estimated probability of 10-9, only after the Sioux City accident was the possibility of using some automatic fly-by-throttle bade up control system for crippled airplane seriously considered. Several different schemes to help pilots fly hydraulically depleted aircraft by using collective and differential thrust of the engines will be reviewed. Special attention will be devoted to the so-called “model matching” methodology. Finally, it will be shown how this research can be extrapolated to the X-33, the reduced scale demonstration vehicle of the new space shuttle.

H∞ longitudinal control of crippled trijet aircraft with throttles only

A novel propulsion controlled aircraft (PCA) design technique for airplanes with control surface failures is presented. The H ∞ model-matching methodology is applied to the problem of controlling the crippled aircraft from conventional stick input commands using the engines as the only available actuators. This paper focuses on pitch control of trijet configuration aircraft, and more specifically on the effect of the height of the tail engine above the center of gravity of the airplane. Simulations on “modified” L-1011 models demonstrate the concept.

Flight-Test Results of Propulsion-Only Emergency Control System on MD-11 Airplane

A large, civilian, multiengine transport MD-11 airplane control system was recently modie ed to perform as an emergency backup controller using engine thrust only. The emergency backup system, referred to as the propulsion-controlled aircraft (PCA)system, would be used if a majorprimary e ight control system fails. To allow for longitudinal- and lateral-directional control, the PCA system requires at least two engines and is implemented through software modie cations. A e ight-test program was conducted to evaluate the PCA system high-altitude e ying characteristics and to demonstrate its capacity to perform safe landings. The cruise e ight conditions, several low approaches, and four landings without any aerodynamic e ight control surface movement were demonstrated; however, only one landing is presented. Results that show satisfactory performance of the PCA system in the longitudinal axis are presented. Test results indicate that the lateral-directional axis of the system performed well at high altitude but was sluggish and prone to thermal upsets during landing approaches. Flight-test experiences and test techniques are also discussed, with emphasis on the lateral-directional axis because of the dife culties encountered in e ight test.