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The Department joined the SCADE Academic Program

Wednesday, 01. October 2014

The Department of Flight Mechanics, Flight Control and Aeroelasticity of the Institute of Aeronautics and Astronautics has joined the SCADE Academic Partnership program of Esterel Technologies GmbH in September 2014. The SCADE Suite® is an environment for the model-based development of safety critical software for embedded systems. SCADE Suite® tools are used at the department in education and research for the development of flight control functions.

AIAA Best Paper Award 2014 for "Modeling Wake Vortex Roll-Up and Vortex-Induced Forces and Moments for Tight Formation Flight"

Monday, 28. April 2014

Formation flight of birds
Lupe

The Modeling and Simulation Technologies Technical Committee of the American Institute of Aeronautics and Astronautics (AIAA) Aerospace Sciences Group selected the research paper, “Modeling Wake Vortex Roll-Up and Vortex-Induced Forces and Moments for Tight Formation Flight,” as Best Paper. The paper was co-authored by Department of Flight Mechanics, Flight Control and Aeroelasticity doctoral candidate André Kaden and Professor Dr. Robert Luckner and it was presented at the Modeling and Simulation Technologies Conference 2013, 19-22 August 2013, at Boston, Massachusetts. It addresses a method to model the wake vortex roll-up and the resulting induced velocities in the near field region behind a generating aircraft. A good knowledge of the vortex-induced velocities and their effect on encountering aircraft is fundamental for tight formation flight investigations.

Tight formation flight mimics the technique of migratory birds that uses the upwash of the leading birds to save energy. Aircraft can use the same principle to ideally save up to 15% fuel. To date, commercial aircraft do not fly in tight formation because of unresolved technical and operational issues. However, increasing fuel cost and environmental constraints are drivers to investigate tight formation flight and the potential fuel savings. One important unresolved aspect is the development of an automatic flight control system that enables a stationary formation flight. This is the objective of the research project “Automatic Formation Flight” that is funded by the Deutsche Forschungsgemeinschaft (DFG).

Kaden and Luckner will be presented a Certificate of Merit in recognition of technical and scientific excellence during AIAA's Aviation and Aeronautics Forum and Exposition (AVIATION 2014), 16-20 June 2014, at the Hyatt Regency Atlanta, Atlanta, Georgia. The AIAA is the world’s largest technical society for aerospace profession.



Reducing Gust Loads by Flight Control

Tuesday, 15. October 2013

Testing the gust load alleviation system on the STEMME S15-LAPAZ that is equipped with a beam for gust measurement and trailing edge flaps along the complete wing span.
Lupe

Wind gusts and turbulence as they do often occur in autumn are not desired during flight, because they reduce passenger comfort, stress the aircraft structure and disturb the aircraft attitude. The opposite is true, if a gust load alleviation system shall be flight tested, as it is the case for the utility aircraft STEMME S15. Here, patience is needed when waiting for weather conditions with sufficient turbulence levels that allow rigorous testing of the system.

Gust load alleviation systems shall compensate accelerations induced by wind gusts. For transport aircraft such systems have already been researched. However they are new for smaller and slower aircraft with lower wing loading and higher aspect ratio, which are used as utility aircraft. Such aircraft as the STEMME S15 are more susceptible to wind and turbulence. They are important for utility aircraft, which. Certain measurements only yield good results, if the sensors are not disturbed by gusts. In order to conduct these kinds of measurement flights in atmospheric turbulence the aircraft has to be stabilized. This stabilization can be achieved by flight control.

Within the LAPAZ project an automatic flight control system is developed and tested by the department for Flight Mechanics, Flight Control and Aeroelasticity from the TU Berlin together with the project partners: the company STEMME and the University of Stuttgart. This system has recently been supplemented with a gust load alleviation system.

Compensation of vertical gusts is achieved by directly influencing the lift with fast moving trailing edge flaps that are located along the whole wingspan of the STEMME S15. Ideally the flaps are deflected into the right position, when a gust hits the wing. In this case the source of the disturbance is compensated as it occurs. However, calculation of the required flap setting and the adjustment of the flaps by the actuators require some amount of time. Therefore the information about a gust is needed before it hits the wing. Hence, a five meter long, extremely light and rigid beam made from ultra-high modulus carbon fiber was developed and attached under the wing. On its tip, two wind vanes are mounted to measure the gust-induced angle of attack. This gives the flight control system enough time to compute the command value and move the flaps into a position that allows compensating the effect of gusts to a large extend.

In addition to this function, the other functions of the flight control system have been improved and extended since first the automatic landing in Neuhardenberg on 22 March 2012. With the enhanced flight control system the first full traffic pattern from start to landing was automatically flown on 23 November 2012. To this day, more than 60 automatic starts and landings where performed on different airfields with grass and concrete runways.

This month a new flight control software version is tested, the last one in this project phase. It contains two new functions. A low level flight function enables measurement flights in low altitudes. It uses a very accurate terrain model. Safe flight is ensured by the pilot, who monitors the flight path by looking outside, as well as the flight control system itself. A laser altitude sensor warns the pilot as soon as the aircraft descends through the planned flight altitude. The second novel function provides the possibility of automatic landings in a glider fashion: the engine is in idle and the angle of approach is controlled with the airbrakes. This method is also suited for emergency landings in case of engine failure.

The LAPAZ project is a cooperation between the STEMME AG, Prof. Dr.-Ing. Robert Luckner and his researchers at the department for Flight Mechanics, Flight Control and Aeroelasticity at the TU Berlin as well as Prof. Reinhard Reichel at the Institute for Avionics Systems and his team at the University of Stuttgart. The research is supported by the Federal Ministry of Economics and Technology.

For additional information please contact: Prof. Dr.-Ing. Robert Luckner, TU Berlin, Institut für Luft- und Raumfahrt, Fachgebiet Flugmechanik, Flugregelung und Aeroelastizität, Tel.: +4930/314-29624,

Test flight of the STEMME S15-LAPAZ: Large beam for gust measurement below the right wing and small beam of the flight test measurement equipment below the left wing
Lupe

First complete automatic mission achieved on November 23rd, 2012

Friday, 23. November 2012

Take-off for the first complete automatic mission: Immediately before becoming airborne the STEMME S15 passed the spectators near Strausberg’s runway.
Lupe

For the first time a complete mission from take-off to touch-down has been demonstrated with the Automatic Flight Control System LAPAZ on the STEMME S15 test aircraft. Test pilot and head of development Lothar Dalldorff repeated this flight four times and was enthusiastic about the perfect test result. The LAPAZ-S15 aircraft lifted off from Strausberg EDAY airfield at Friday afternoon, November 23rd, 2012. The S15 was taxied manually from parking position to the runway, where the LAPAZ system took over. From that moment on, Lothar Dalldorff acted as safety pilot monitoring the flight without operating the controls. The S15 was commanded to automatically takeoff, to fly over two waypoints that defined a very large traffic pattern and finally to land on the same runway.

During the third landing approach, the aircraft initiating a go-around just two meters above the runway. The control instance of LAPAZ has detected a short loss of the airspeed signal and aborted the approach. Although not planned, this event had shown LAPAZ’s ability to cope with such a situation. To find the cause, a non-optimal monitor threshold, and to improve the system belong to the next tasks for TU Berlin’s department “Flight Mechanics, Flight Control and Aeroelasticity”. Also gigabytes of test data are waiting for analyzes and assessment to validate that the Automatic Flight Control System LAPAZ has worked as planned. More information about the LAPAZ project can be found here.

Link: http://www.stemmesystems.com/lapaz_full_mission.htm

The safety pilot: Dipl.-Ing. Lothar Dalldorff acted as a safety pilot, to allow the aircraft to be flown in controlled airspace.
Lupe
Touch-down on the center-line: Because of crosswinds, the starboard main wheel touched a split second after the other onto the runway. Note that the front wheel is right on the centre line.
Lupe

WakeNet3-Europe-Workshop on Recategorisation at TU Berlin

Wednesday, 22. June 2011

"RECAT"-Workshop participants in TU Berlin's "Lichthof"
Lupe

On June 20th and 21st, 2011, an international workshop on "re-categorization" was held at TU Berlin within the framework of the EU project WakeNet3-Europe. Participants from industry, government and research discussed the safe separation of aircraft in flight.

This separation currently is based on regulations that were defined in the 1970s by the International Civil Aviation Organization (ICAO). These regulations classify aircraft into three categories (light, medium, heavy) according to their maximum takeoff weight. For each of the categories, minimum separation distances that must be observed during take-off an landing are defined. The heavier the preceding aircraft, the longer the distance which the follower has to maintain.

These minimum separation distances have proven safe in the last 40 years. However, they are regarded to be over-conservative in many situations, thus reducing airspace capacity. S
everal countries have implemented national and, to some airports, even local changes to the separation rules. Some of the modifications include the weight category boundaries or assign special rules to some aircraft types (e. g. Boeing 757).

At a workshop on wake vortex modeling in Berlin in 2006 the idea was born to propose to ICAO a new set of safe separation distances. The European Civil Aviation Authority Eurocontrol and the US
Civil Aviation Authority FAA initiated the RECAT project. This project has three phases: In the first phase, all aircraft are grouped into six new categories, in the second phase aircraft are separated pairwise with fixed minima; in the third phase, separation minima are dynamically adjusted to weather and vortex aging conditions.

To adjust the regulations it is necessary to perform a safety analysis in which it is proven with a transparent and physics-based method that the new separation minima do not reduce flight safety.

The 2011 workshop's objectives were to initiate the discussion about models, methods and metrics for the re-categorization, involving experts from industry, government and research, and to identify research needs for the re-categorization process. It was seen that, due to extensive measurement campaigns and large, multi-disciplinary research projects, in the past decades significant progress was made on the understanding of wake-vortex physics. However, several open questions remain before the RECAT phases can be realized. WakeNet3-Europe will identify research needs and therefore gives directions for the focus of future research.

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