Unlike commercial air transport and military aircraft, the high performance glider was developed as an end in itself so that individual pilots could achieve extended flights using only energy present in the air. From modest beginnings in the first two decades of this century the best gliders available today are able to fly 60 miles from a height of about 6000 ft in no wind and without upcurrents. Using thermals and other available lift in the air these gliders are capable of flying a distance of 1000 miles in a day. The realisation of such performance efficient gliders was possible because the design problems attracted top quality aerodynamicists. Germany led, and still leads, because German universities saw, in glider development, a fine training ground for young aeronautical engineers — initially encouraged, of course, by the Versailles Treaty which forbade the manufacture of powered aircraft at the end of WW1. Now superb gliders exist but because of their cost, complexity and size they can be afforded and/or flown by only a relatively small number of pilots. This paper follows the historical development of gliders, the arrival of hang gliders and paragliders and considers the way forward for motorless flight.

A number of modern “aerodynamic” bicycle wheels were tested at full scale speeds in a windtunnel. The effects of wheel geometry, rotational speed and cross winds on drag force, side force and yawing moment were investigated.

Compared with a conventional spoked wheel, all the “aerodynamic” wheels were found to give similar improvements in drag of approximately 25%. In cross wind conditions, aerodynamic characteristics were strongly dependent on wheel geometry, but essentially independent of wheel rotational speed.

Vortex breakdown phenomenon remains a challenging aspect of the flow over delta wings at high angle of attack. The observations of vortex breakdown and related interpretations for vortex tube experiments and delta wings are summarised in several review articles. The theoretical models of the phenomena are described in detail in References 1, 2, 3 and 7. These theoretical models are not complete enough to predict breakdown location over delta wings. The purpose of this note is to review several existing criteria and correlations for vortex breakdown over delta wings using a large database. The earliest criteria for delta wings was suggested by Lambourne and Bryer.

Excessive deceleration forces experienced during high speed deployment of parachute systems can cause damage to the payload and the canopy fabric. Conventional reefing lines offer limited relief by temporarily restricting canopy inflation and limiting the peak deceleration load. However, the open-loop control provided by existing reefing devices restricts their use to a specific set of deployment conditions. The sensing, processing, and actuation which are characteristic of adaptive structures form the basis of three concepts for active control of parachute inflation. These active control concepts are incorporated into a computer simulation of parachute inflation. Initial investigations indicate that these concepts promise enhanced performance as compared to conventional techniques for a nominal release. Furthermore, the ability of each controller to adapt to off-nominal release conditions is examined.

High-lift systems have to provide adequate low speed performance in terms of takeoff and landing lengths, approach speed, climb rate and community noise. Even if the performance of these systems has been continuously improved during the years, there are still some possibilities for further improvements.

ONERA has been involved for a long time in research on high-lift systems for transport aircraft. This research has provided valuable results in the following areas:

• ● The knowledge of the dominant flow processes involved for 2D and 3D geometries. In particular the stall mechanism, Reynolds and Mach number effects as well as sweep effects have been studied by performing detailed experiments.

• ● The development of 2D analysis and design codes which have been extensively calibrated with experimental data and are used with confidence for practical applications.

• ● The design and testing of various high-lift systems which provide manufacturers with data for their own designs.

The paper summarises these activities and presents some typical results. Future trends for research on high-lift systems at ONERA are also given.