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Aircraft Vortex Wake


Flight Safety, Aircraft Vortex Wake and Airport Operation Capacity

Tech Area / Field

  • SAT-AER/Aeronautics/Space, Aircraft and Surface Transportation

8 Project completed

Registration date

Completion date

Senior Project Manager
Tocheny L V

Leading Institute
Central Aerodynamic Institute, Russia, Moscow reg., Zhukovsky


  • National Aerospace Laboratory NLR, The Netherlands, Amsterdam\nDeutsches Zentrum für Luft- und Raumfahrt e.V. / Institut für Physik der Atmosphare, Germany, Wessling\nDaimlerChrysler Aerospace Airbus, Germany, Bremen\nAIRBUS Industrie, France, Blagnac

Project summary

According to ICAO's forecasts, for some years to come the world annual growth required of air traffic will amount to 6.5% for freight traffic and 5% for passenger transportation. For the Asia-Pacific region countries these figures will be twice as high. The impossibility of realizing the required freight and passenger traffic leads to economic losses (today's annual losses of USA's economy makes up 2 billion USD and, according to the European Strategic Research Institute, annual total losses of European economies will reach 10 billion USD by 2000). By the year 2010, 13 European airports, even modernized, will have entered a period of crisis and will not be able to satisfy growing demands in air traffic. Still more severe crisis is in store for the Asia-Pacific countries.

The goal of the Project is to work out safe-separation criteria reconciled with the foreign partners and to evaluate the possibilities of reducing safe-separation distances, which eventually would increase traffic density, first of all, when flying along the glide path. In the course of implementing ISTC Project # 201 "Investigation of Aircraft Vortex Wake Evolution and Flight Safety Problems" (VORSAF) one managed to form a unique research team, establish ties with foreign researchers (see Block-scheme 1 below) and accumulate expertise that can be used for solving the problem the urgency of which is associated with the realization of the air traffic growth required being impossible in the framework of existing technologies.

In particular, on the basis of available results of experimental and theoretical investigations, a probabilistic mathematical model was constructed of the vortex wake produced by an aircraft during landing. Accounted for in this model are the effects of ground proximity and atmospheric disturbances on moving and spatially curving vortex plaits. A methodology was developed for approximately calculating velocity fields induced by curved vortices and a technique for calculating aerodynamic loads and moments acting on an aircraft both in a quasi-steady flow regime and with taking into account unsteady effects. Estimates were obtained of the probability of in-flight reaching large values of the coefficient fmax = [(mx)dist / (mx)avail]max, which is the measure for hazard strength of a possible aircraft accident. On the basis of these estimates a preliminary assessment of the soundness of existing safe-separation regulations for aircraft of various types was performed. The models developed need refining by means of a thorough comparison of the results of mathematical and hardware-in-the-loop simulation with flight data obtained at various airfields.

In the new project, in accordance with consensus achieved with the collaborators, emphasis is placed on experimental studies to refine and verify models developed as well as to elaborate concrete measures and technical decisions to ride out of the crisis.

One of the possible ways to provide a higher landing and takeoff traffic density is wake visualization. In parallel with theoretical studies on the physics of formation of tracer microparticles and molecular clusters in aircraft vortex-jet wakes, experimental studies on wake visualization are planned in wind tunnels and field conditions using a movable lidar. Another possible solution of the problem under study is associated with increasing an aircraft's "survivability" in a vortex wake environment. In particular, the possibility is considered to double the available rolling moment by using differential deflections of flaps without degradation of an aircraft's takeoff/landing characteristics; measures to decrease dynamic loads on an aircraft during cross-track wake encounter are also investigated.

One more direction to solve the problem of flight safety is the creation of an on-board device for early detection of wake encounters by use of standard angular rate sensors and gaining pilots' skill to depart from dangerous situations with the help of flight simulators. Both systems should use the mathematical model of wake developed in the framework of the Project.

The principal safe-separation criterion is the provision for safe takeoff and landing operations of aircraft. In assessing a hazard degree of a situation, control modes and a pilot's behavior should be taken into consideration. It is planned to broaden investigations with the use of flight simulators to model aircraft accidents.


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