| Autor(en) | Diekmann, Jobst Henning | Pichler, Maximilian | Steen, Meiko | Hecker, Peter |
|---|---|
| Titel | Controllability of an aircraft with active high-lift system using a segmentwise controllable flap system |
| Herausgeber | CEAS Aeronautical Journal, Springer Verlag, 2018 |
| Erscheinungsjahr | 2018 |
| Abstract | Active high-lift aircraft needs exceptional aerodynamic control performance to operate at low airspeed. In this study, a new concept for the improvement of controllability is investigated, incorporating the special capabilities of a blown Coanda flap system. The blowing system along the flaps is divided into 12 independently controllable segments. This provides the opportunity to influence the lift distribution along the wingspan by individual blowing performance settings for each segment without changing the flap deflection. This offers the chance to control the airplane in the final approach phase with fully deflected flaps using only the blowing system and to dedicate specific control tasks to particular segments. A model for the blowing system influence on the local wing aerodynamics is implemented in an existing nonlinear full aircraft flight mechanics model. The system capabilities in terms of roll control and the climb performance are investigated by criteria evaluation and dynamic simulation assessment. The ability to fly turn/altitude change maneuvers by utilizing the active high-lift system is proven and a corresponding control concept is presented. It also includes the compensation of different blowing failure cases, which leads to acceptable but still improvable aircraft reactions. |
| Autor(en) | Diekmann, Jobst Henning |
|---|---|
| Titel | Flight Mechanical Challenges of STOL Aircraft Using Active High-Lift |
| Herausgeber | 35. Applied Aerodynamics Conference, AVIATION 2017, Denver, CO |
| Erscheinungsjahr | 2017 |
| Abstract | 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. |
| Autor(en) | Diekmann, Jobst Henning | Keller, Dennis | Faez, Edris | Rudnik, Ralf | Gollnick, Volker |
|---|---|
| Titel | Flight mechanics model for spanwise lift and rolling moment distributions of a segmented active high-lift wing |
| Herausgeber | CEAS Aeronautical Journal |
| Erscheinungsjahr | 2017 |
| Abstract | 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. |
| Autor(en) | Diekmann, Jobst Henning | Keller, Dennis | Faez, Edris | Rudnik, Ralf | Gollnick, Volker |
|---|---|
| Titel | FLIGHT MECHANICS MODEL FOR SPANWISE LIFT AND ROLLING MOMENT DISTRIBUTIONS OF A SEGMENTED ACTIVE HIGH-LIFT WING |
| Herausgeber | 65. Deutscher Luft- und Raumfahrtkongress, Braunschweig |
| Erscheinungsjahr | 2016 |
| Abstract | 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 model for fast-time simulation of flight dynamics, which has been derived from high-fidelity CFD results. An assessment of single segment 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 on which the failure appears. Thus, the potential for an increase of system reliability shall be proven. The results show that less performance investment is necessary to compensate the rolling moment of a failing segment instead of its lift. However, large performance increases for the remaining wing segments occur for some of the failure cases. |
| Autor(en) | Diekmann, Jobst Henning |
|---|---|
| Titel | Analysis of trimmable conditions for a civil aircraft with active high-lift system |
| Herausgeber | CEAS Aeronautical Journal, Springer Verlag, Wien, 2014 |
| Erscheinungsjahr | 2014 |
| Abstract | 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 take-off and approach procedures. The flight physics are 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. |
| Autor(en) | Vechtel, Dennis | Meissner, Ute Marita | Hahn, Klaus-Uwe |
|---|---|
| Titel | On the use of a steerable main landing gear for crosswind landing assistance |
| Herausgeber | CEAS Aeronautical Journal, ISSN 1869-5582 |
| Erscheinungsjahr | 2014 |
| Abstract | Several crosswind-related incidents show that landing under heavy crosswind conditions can be challenging for pilots and may pose a threat to aviation or at least lead to higher pilot workload and/or irregularities in operations. For transport aircraft the common approach technique for crosswind landings is the so-called crabbed approach with wings level and a windward heading correction. This technique requires alignment of the aircraft with the runway prior to touchdown in order to keep lateral loads of the landing gear and tyres as low as possible and to maintain the controllability on ground after touchdown. The German Aerospace Center Institute of Flight Systems has used the idea of steerable main gears and developed a crosswind landing assistance system. During approach all gear struts are automatically aligned with the runway so that no decrab manoeuvre is required. On ground the assistance system uses each steerable landing gear, differential braking, and the aerodynamic control surfaces to control and stabilise the aircraft. After touchdown the aircraft is automatically aligned with the runway centreline and the still existing crab angle is slowly reduced. A simulator study with pilots in the loop using a model of a typical medium range transport aircraft was conducted in order to evaluate the benefits of such a landing technique. The study revealed that not only the aircraft controllability could be improved by landing in crabbed motion under strong crosswind conditions, but that the side forces acting on the landing gear can be reduced significantly as well. It was also shown that the use of steerable main landing gears is able to enlarge the spectrum of autoland operations, which is relatively limited at present in terms of maximum allowable crosswinds. All together the system has shown to be able to improve flight safety, lower the risk of weather-related delays due to go-arounds or diversions, and it also reduces structural loads on the landing gear during touchdown and landing. |
| Autor(en) | Diekmann, Jobst Henning |
| Titel | Trim Analysis of Nonlinear Flight Dynamics for a Civil Aircraft with Active High-Lift System |
| Herausgeber | 62. Deutscher Luft- und Raumfahrtkongress, Stuttgart, 2013 |
| Erscheinungsjahr | 2013 |
| Abstract | This paper shows recent flight mechanical simulation results of a civil active high-lift aircraft with blown Coandu 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 high-lift 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 high-lift system, namely characteristics hardly compatible with safe take-off 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. |
| Autor(en) | Horst, Peter | Keller, Dennis | Diekmann, Jobst Henning | Krukow, Ian | Sommerwerk, Kay |
|---|---|
| Titel | SFB880: Flight Dynamics |
| Herausgeber | Deutscher Luft- und Raumfahrtkongress, Stuttgart, 2013 |
| Erscheinungsjahr | 2013 |
| Abstract | The paper summarizes approaches and first results on flight dynamics of the Collaborative Research Centre SFB 880 - "Fundamentals of High Lift for Future Commercial Aircraft" - , i.e. high fidelity solutions of dynamics in aerodynamics, aeroelasticity and flight control. |
| Autor(en) | Diekmann, Jobst Henning |
|---|---|
| Titel | Investigation of Flight Dynamics of a Civil Aircraft with Active High Lift System |
| Herausgeber | Deutscher Luft- und Raumfahrtkongress 2012 (Berlin) |
| Erscheinungsjahr | 2012 |
| Abstract | 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. |
| Autor(en) | Schwarz, Carsten | Hahn, Klaus-Uwe |
|---|---|
| Titel | Automated pilot assistance for wake vortex encounters |
| Herausgeber | Aerospace Science and Technology, ISSN 1270-9638, Vol. 15, Iss. 5, Elsevier, P. 416 - 421, 2011 |
| Erscheinungsjahr | 2011 |
| Abstract | Wake vortices pose a possible hazard for encountering aircraft in all phases of flight. Hence wake vortex encounters are to be avoided in any case. In case of an unintended wake vortex encounter special aircraft controllers can act as a safety net. Such an active wake vortex control system is being developed by the DLR Institute of Flight Systems based on feed-forward disturbance compensation. The control system has been tested with offline and pilot-in-the-loop investigations as well as with flight tests. It can be shown that the aircraft response can be improved significantly if the pilots are supported by an automatic wake assistance system. For the subjective assessment of the wake vortex encounters a dedicated pilot rating scale has been developed. The results show a clear tendency that the wake vortex controller improves the situation. |