Measurements of wing buffeting, using root straingauges, were made in the Nasa Langley 0-3 mcryogenic windtunnel to refine techniques which willbe used in larger cryogenic facilities such as theUnited States National Transonic Facility (NTF) andthe European Transonic Windtunnel (ETW). Thequestions addressed included the relative importancevariations in frequency parameter and Reynoldsnumber, the choice of model material (consideringboth stiffness and damping) and the effects ofstatic aeroelastic distortion.

The main series of tests was made on three half modelsof slender 65° delta wings with a sharp leadingedge. The three delta wings had the same planformbut widely differing bending stiffnesses andfrequencies (obtained by varying both the materialand the thickness of the wings). It was known thatthe steady flow on this configuration would beinsensitive to variations in Reynolds number. Onthis wing at vortex breakdown the spectrum of theunsteady excitation is unusual, having a sharp peakat particular frequency parameter.

Additional tests were made on one unswept half-wing ofaspect ratio 1·5 with an NPL 9510 aerofoil section,known to be sensitive to variations in Reynoldsnumber at transonic speeds. The test Mach numberswere M = 0·21 and 0·35 for the delta wings and to M= 0·30 for the unswept wing. On this wing theunsteady excitation spectrum is fairly flat (as onmost wings). Hence correct representation of thefrequency parameter is not particularlyimportant.

An analysis technique capable of simulating the effectof engine failure during takeoff from offshoreplatforms is presented. Use is made of inversesimulation whereby the control actions required fora subject helicopter to follow a particulartrajectory can be established. A mathematicalrepresentation of the towering takeoff procedure,and details of the modified inverse simulationtechnique needed to cope with the modelling of anengine failure are described. Detailed pilotingaccounts of the strategy used to fly the toweringtakeoff (with and without engine failures) are alsogiven and are used to give qualitative validation ofthe analytical approach. Simulation results for asingle engine failure of a transport helicopterduring critical phases of a towering takeoff arepresented. Finally, some directions for future workand potential applications of the technique arediscussed.

The influence of isolated spherical roughness elementsupon the transition of a three-dimensional boundarylayer on a swept flat plate is discussed in thispaper. Perturbations induced by the roughness arefound to be more effective on the start oftransition rather than the crossflow of the laminarundisturbed boundary layer at the roughnesslocation.

This paper describes an investigation of theaerodynamic characteristics of collectively variableincidence wing tips at low speeds. Theoreticalconsiderations supported by experimentalmeasurements suggest that the use of articulatedtips which can be rotated to a high incidence forlow speed flight will decrease sensitivity to gusts.Furthermore, windtunnel measurements demonstratethat the use of very high tip incidences can producean increment in maximum overall lift coefficient forsome wing configurations. Another featureinvestigated is the possibility of utilising thelift increment for the purposes of direct liftcontrol. The use of a radio controlled model to testthe practical viability of the concept isdescribed.