Flight mechanics model for spanwise lift and rolling moment distributions of a segmented active high-lift wing

In this study, the aerodynamics of wings using an active high-lift system are investigated. The target is the flight mechanical description of the spanwise forces and resulting moments and the influence of the active high-lift system to their distribution. The high-lift system is a blown flap system divided into six segments per wing. Each segment is assumed to be individually controlled, so the system shall be used for aircraft control and system failure management. This work presents a flight mechanical sub-model for the simulation of flight dynamics, which has been derived from high-fidelity CFD results. An assessment of single-segment blowing system failures will be presented including recommendations for compensation of either lift or rolling moment loss. For this investigation, the compensation is required to act at the same wing side on which the failure appears. Thus, the potential for an increase of system reliability shall be proven. The results show that less performance investment in terms of pressurized air is necessary to compensate the rolling moment of a failing segment instead of its lift. However, large blowing performance increases for the remaining wing segments that occur for some of the failure cases

Analysis of Trimmable Conditions for a Civil Aircraft with Active High-Lift System

This paper outlines recent flight dynamic Analysis results of a civil aircraft with active high-lift System using blown Coanda˘ flaps. The main focus lies in the trim analysis of the aircraft. Therefore, the basic structure and core elements of the nonlinear model, describing the dynamic behavior of an aircraft with this specific type of active high-lift system are presented. The center of gravity range allowing controllability and static stability of the aircraft is determined, and the resulting characteristics of the aerodynamic model and their impact on the trim results of the aircraft are analyzed. The results show specific flight dynamic difficulties related to the active high-lift system, namely in the flying characteristics necessary for safe takeoff and approach procedures. The flight physics is explained and discussed. The necessity of the application of a wing leading edge device is outlined by preliminary studies and further remedial means are proposed

Investigation of flight dynamics of a civil aircraft with active high lift system

In this paper ongoing research on the flight dynamic modeling and analysis of an aircraft with active high lift is presented. The considered aircraft is being designed with an aircraft multidisciplinary design and optimization tool (PrADO) and is a twin turboprop equipped with an active high lift system consisting of a Coandă surface flap whose knee is blown to enable boundary layer control. In this paper, a longitudinal model is derived from the first aerodynamic data available for this aircraft and used to make a first assessment of the flight dynamics of this aircraft configuration. In particular, the effects of the active high lift system on the trim conditions and the normal modes of the aircraft are shown, as well as a first assessment of the consequences of an active blowing system failure. A remarkable intermediate result is that with proper actions of the pilot (or the flight control system) such a failure seems to have significantly less severe consequences than initially feared

Nonlinear Flight Dynamics Simulation Model for a Civil Aircraft with Active High Lift System

The design of innovative control concepts by using the opportunities of an active high lift system is only possible with a proper understanding of the underlying flight dynamics of active high lift aircraft. This report shows the achievements in flight dynamics simulation model design. The target of this work is to create a nonlinear mathematical model, which describes the dynamic behavior of an active high lift aircraft and which provides direct access to the active high lift system in order to use it for aircraft control. The main focus lies on the development of a suitable model structure and the design of an aerodynamic derivative model. In addition an engine model which allows for usage of bleed air for blown flaps has to be established and integrated into the simulation environment. The consistent further development of an existing model structure for conventional aircraft, as well as the identification of the aerodynamic model by analysis of SFB 880 created CFD results will be presented. The modeled effects of the active high lift system on the aerodynamics are introduced and the existing nonlinearities which are occurring due to stall are explained. These nonlinearities are also reflected in the model for downwash and pitching moment. The resulting characteristics of the aerodynamic model and their impact on the longitudinal motion of the aircraft will be demonstrated and discussed

Trim Analysis of Nonlinear Flight Dynamics for a Civil Aircraft with Active High-Lift System

This paper shows recent flight mechanical simulation results of a civil active highlift aircraft with blown Coand˘a flaps. The main focus lies on the trim analysis of the aircraft. To this end the basic structure and core elements of the nonlinear model, describing the dynamic behavior of an aircraft with this specific type of active highlift system, are presented. The center of gravity location range allowing controllability and static stability of the aircraft is determined, followed by an analysis of the resulting characteristics of the aerodynamic model and their impact on the trim results of the aircraft. The results show specific flight mechanical difficulties due to the active highlift system, namely characteristics hardly compatible with safe takeoff and approach procedures. The physical explanations will be given and discussed. The necessity of the application of a wing leading edge device is pointed out by preliminary studies and further remedial means are proposed

Flugmechanische Charakteristika von propellergetriebenen Flugzeugen mit aktiven Hochauftriebssystemen

Durch das stetig steigende Flugaufkommen gelangen Lufträume und stark frequentierte große Flughäfen zunehmend an ihre Kapazitätsgrenzen. Die Erschließung existierender kleiner, stadtnaher Flughäfen mit kurzen Start- und Landebahnen für den Linienflugverkehr ist hierfür ein attraktiver Lösungsansatz zur Entlastung. Dies Bedarf eines kurzstart- und -landefähigen Passagierflugzeugs mit ausreichender Transportleistung und kurzer bis mittlerer Reichweite. Um diese Fähigkeit zu erhalten, sind aktive Hochauftriebssysteme notwendig, die eine signifikante Reduktion der Anfluggeschwindgkeiten solcher Flugzeuge ermöglichen. Derart leistungsfähige Hochauftriebssysteme sind bereits seit mehreren Jahrzehnten Gegenstand der Forschung, finden jedoch aufgrund ihres hohen zusätzlichen Energiebedarfs und/oder sensiblen sicherheitskritischen Technologien bislang keinen Einsatz in der kommerziellen Luftfahrt. Im Rahmen des Sonderforschungsbereichs 880 (SFB 880) "Grundlagen des Hochauftriebs künftiger Verkehrsflugzeuge" werden aktive Hochauftriebssysteme zu diesem Zweck mit modernsten Methoden erforscht und weiterentwickelt. In dieser Arbeit wird eine Flugzeugkonfiguration betrachtet deren Hochauftriebssystem aus einer Kombination von angeblasenen sog. Coanda-Klappen und Propellerstrahleffekten besteht. Dadurch werden sehr hohe Auftriebsbeiwerte und damit langsame Fluggeschwindigkeiten bei wirtschaftlich akzeptablem zusätzlichen Energieaufwand erzielt. Die Kombination aus angeblasenen Klappen und Propellerstrahleffekten ist bereits in der Vergangenheit in Forschungsprogrammen von NASA und NAL erforscht worden. Trotz der bestätigten guten Flugleistungen zeigten sich in der Vergangenheit stets nicht zufriedenstellende bis inakzeptable Flugeigenschaften in der Seitenbewegung solcher Konfigurationen mit unvorhersehbarem Verhalten im Kurvenflug. Die Gründe für dieses Flugverhalten blieben jedoch bislang weitgehend ungeklärt und auch stabilisierende Unterstützungssysteme konnten keine zufriedenstellenden Eigenschaften erzeugen. Die vorliegende Arbeit befasst sich daher mit der flugmechanischen Analyse der Gründe für dieses Flugverhalten und der Synthese von Lösungsansätzen, um die Leistungsfähigkeit dieser effizienten Hochauftriebssysteme für den kommerziellen Gebrauch uneingeschränkt nutzbar zu machen. Zu diesem Zweck wird ein flugmechanisches Modell vorgestellt, das die Aerodynamik dieser Flugzeugkonfiguration auf Basis modernster Strömungslösungen beschreibt. Besondere Aufmerksamkeit wird der Beschreibung der Propellerstrahlinteraktion mit dem Rumpfheck gewidmet, die einen entscheidenden Einfluss auf das Flugverhalten der Konfiguration hat. Mittels flugmechanischer Simulation werden die besonderen Flugleistungen der Konfiguration bestätigt. Weiter werden die Flugeigenschaften und die Steuerbarkeit analysiert. Dabei wird herausgestellt, welche aerodynamischen Effekte und Kopplungen das defizitäre Flugverhalten erzeugen, das sich auch für die SFB-Konfiguration in ausgeprägter Form zeigt. Diese Erkenntnisse werden in einer Synthese zur Verbesserung der Eigenschaften eingesetzt. Es wird überprüft, welches Verbesserungspotential durch aerodynamische Adaption und regelungstechnische Kompensation mittels der Steuerorgane erzielt wird. Dadurch ist es gelungen die Ursachen für das defizitäre Flugverhalten solcher Konfigurationen flugmechanisch eindeutig zu identifizieren und effiziente Lösungsansätze vorzustellen

Flight Mechanical Challenges of STOL Aircraft Using Active High-Lift

This paper focuses on the flight mechanical characteristics of an active high-lift supported transport type aircraft. The presented configuration combines a boundary-layer controlled flaps system with the benefits of propeller slipstream deflection. The underlying aerodynamic models and assumptions are provided. The extraordinary flight performances especially at low airspeed will be pointed out, as well as potential weaknesses. Special attention is paid to the unusually strong aerodynamic couplings in the lateral motion. Therefore, flight dynamics characteristics will be presented and their challenges discussed. The key influences are pointed out and an outlook will be given, how to exploit this knowledge for safe and satisfactory aircraft operation and handling

Flight Mechanical Challenges of STOL Aircraft Using Active High Lift

This paper focuses on the flight mechanical characteristics of an active high-lift supported transport-type aircraft. The presented configuration combines a boundary-layer controlled flaps system with the benefits of propeller slipstream deflection. The underlying aerodynamic models and assumptions are provided. The extraordinary flight performances especially at low airspeed will be pointed out, as well as potential weaknesses. Special attention is paid to the unusually strong aerodynamic couplings in the lateral motion. Therefore, flight dynamics characteristics will be presented and their challenges discussed. The key influences are pointed out and an outlook will be given, how to exploit this knowledge for safe and satisfactory aircraft operation and handling

Entwicklung eines Softwaremoduls zur Generierung von Trajektorien zum kleinräumigen Ausweichen vor Wirbelschleppen

Das DLR-Projekt "Wetter & Fliegen" des Instituts für Flugsystemtechnik befasst sich allgemein mit den Auswirkungen von atmosphärischen Störungen auf den Flugbetrieb. Hierbei spielen Wirbelschleppen eine große Rolle, da sie ein großes Gefahrenpotential für die Luftfahrt bedeuten. Eine der Zielsetzungen des Projektes ist die Entwicklung eines Detektions- und Ausweichsystems für Wirbelschleppen. Als ein Teil dessen soll in dieser Arbeit ein Algorithmus zur Generierung von Trajektorien zum Ausweichen vor Wirbelschleppen entwickelt werden. Durch den Vergleich verschiedener Ausweichkonzepte soll ein geeignetes Konzept ausgewählt und erprobt werden. Es werden dabei Konzepte aus verschiedenen Bereichen vorgestellt, die sich bereits auf anderen Anwendungsgebieten bewährt haben

Nonlinear Flight Dynamics Simulation Model for a Civil Aircraft with Active High Lift System

The design of innovative control concepts by using the opportunities of an active high lift system is only possible with a proper understanding of the underlying flight dynamics of active high lift aircraft. This report shows the achievements in flight dynamics simulation model design. The target of this work is to create a nonlinear mathematical model, which describes the dynamic behavior of an active high lift aircraft and which provides direct access to the active high lift system in order to use it for aircraft control. The main focus lies on the development of a suitable model structure and the design of an aerodynamic derivative model. In addition an engine model which allows for usage of bleed air for blown flaps has to be established and integrated into the simulation environment. The consistent further development of an existing model structure for conventional aircraft, as well as the identification of the aerodynamic model by analysis of SFB 880 created CFD results will be presented. The modeled effects of the active high lift system on aerodynamics are introduced and the existing nonlinearities which are occurring due to stall are explained. These nonlinearities are also reflected in the model for downwash and pitching moment. The resulting characteristics of the aerodynamic model and their impact on the longitudinal motion of the aircraft will be demonstrated and discussed