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This paper aims to present a numerical method based on computational fluid dynamics that allows investigating the buffet envelope of reference equivalent wings at the equivalent cost of several two-dimensional, unsteady, turbulent flow analyses. The method bridges the gap between semi-empirical relations, generally dominant in the early phases of aircraft design, and three-dimensional turbulent flow analyses, characterised by high costs in analysis setups and prohibitive computing times.

Accuracy in the predictions and efficiency in the solution are two key aspects. Accuracy is maintained by solving a specialised form of the Reynolds-averaged Navier–Stokes equations valid for infinite-swept wing flows. Efficiency of the solution is reached by a novel implementation of the flow solver, as well as by combining solutions of different fidelity spatially.

Discovering the buffet envelope of a set of reference equivalent wings is accompanied with an estimate of the uncertainties in the numerical predictions. Just over 2,000 processor hours are needed if it is admissible to deal with an uncertainty of ±1.0° in the angle of attack at which buffet onset/offset occurs. Halving the uncertainty requires significantly more computing resources, close to a factor 200 compared with the larger uncertainty case.

To permit the use of the proposed method as a practical design tool in the conceptual/preliminary aircraft design phases, the method offers the designer with the ability to gauge the sensitivity of buffet on primary design variables, such as wing sweep angle and chord to thickness ratio.

The infinite-swept wing, unsteady Reynolds-averaged Navier–Stokes equations have been successfully applied, for the first time, to identify buffeting conditions. This demonstrates the adequateness of the proposed method in the conceptual/preliminary aircraft design phases.

This paper aims to show results of numerical simulations of transonic flow around a supercritical airfoil at chord Reynolds number Re_c = 3 × 10⁶, with the aim of elucidating the mechanisms responsible for large-scale shock oscillations, namely, transonic buffet.

Unsteady Reynolds-averaged Navier–Stokes simulations and detached-eddy simulations provide a preliminary buffet map, while a high fidelity implicit large-eddy simulation with an upstream laminar boundary layer is used to ascertain the physical feasibility of the various buffet mechanisms. Numerical experiments with unsteady RANS highlight the role of waves travelling on pressure side in the buffet mechanism. Estimates of the propagation velocities of coherent disturbances and of acoustic waves are obtained, to check the validity of popular mechanisms based on acoustic feedback from the trailing edge.

Unsteady RANS numerical experiments demonstrate that the pressure side of the airfoil plays a marginal role in the buffet mechanism. Implicit LES data show that the only plausible self-sustaining mechanism involves waves scattered from the trailing edge and penetrating the sonic region from above the suction side shock. An interesting side result of this study is that buffet appears to be more intense in the case that the boundary layer state upstream of the shock is turbulent, rather than laminar.

The results of the study will be of interest to any researcher involved with transonic buffet.

EUROPEAN aerospace was well to the fore at the Show, with first appearances of the A320, Fokker 100 and BAe 146–300. Few large US aircraft were present although the executive jet market was well represented with products from both sides of the Atlantic. Potential developments were featured in many areas, all of which should be realised in the next few years. Progress of the flight trials of the Airbus Industrie A320 was detailed with three of the four aircraft in the programme now flying. The first of these is exploring all the critical flight conditions. The normal operating envelope was covered on the first flight; from 80 knots to 381 knots/0.89 M and a cg range up to 46% aft cg. Handling qualities have now been explored over the full flight envelope, with the protection devices working as predicted and buffet limits better than forecast. Major tasks have included stall identification and handling qualities at aft cg as well as flutter tests with and without the load alleviation function. The second A320 has the primary tasks of dealing with the development and checking of the systems, emphasis on the third is placed on flight control and computing and the fourth aircraft will be undertaking performance trials.

A commuter flight crashed when the left engine lost power at a critical point in the takeoff, apparently because of previously ingested metal fragments, the National Transportation Safety Board report.

The quality of aeroelastic predictions strongly depends on the quality of aerodynamic predictions. At the boundary of a typical flight envelope, special flow conditions may arise, which challenge the conventional Reynolds-averaged Navier–Stokes (RANS) approach beyond reasonable limits.

Test Case 3 of the Second AIAA Aeroelastic Prediction Workshop is a representative test case, where the flow over a supercritical wing separates downstream of the shock waves and generates large turbulent lengthscales.

In this study, RANS predictions are compared to those obtained in this particular test case with the more sophisticated hybrid RANS–large eddy simulation (LES) approach, in particular with the Spalart–Allmaras–delayed detached eddy simulation model. Results are indeed closer to experimental data.

However, the costs associated with this approach are much higher. It is argued that adopting hybrid RANS–LES modelling is not a simple model switch.

IN order to appreciate the development of the wing, it is necessary to understand how the basic objectives of the aircraft affect the wing, and the platform of knowledge on which the design was founded.

IF AIRBUS INDUSTRIE'S A300B continues its present rate of progress with its flight‐test programme, as scheduled it will undoubtedly become remarkable among modern prototypes for the speed of development. In the two months following its first flight on 28th October, 1972, the first A300B spent more than 100 hours in the air, including 62 in December alone. During that time, in the course of just over 30 sorties, it covered all but the top end of its flight envelope; completed stalls in all configurations at extreme CG positions, including preliminary stall clearance by the official CEV test crew; demonstrated cruise and low‐speed single‐engine performance within plus or minus one per cent of the design specification; achieved initial flutter clearance; and proved generally very easy and pleasant to fly.

The general reasons for considering a fresh approach to the calculation of air‐worthiness design tail loads and associated torques due to elevator‐induced pitching manoeuvres are discussed. Then follows a description of the manoeuvre itself, elevator actions to be assumed, and the proposed method of calculating the various response quantities. The analytical treatment of Czaykowski given to the unchecked manoeuvre is extended to cover the checked case in Appendix I, Part III and a comparison is made of the two types of manoeuvre. The application of the work to auto‐pilot feed‐back failure causing hunting of the elevator control is also dealt with. The effect of aircraft size, weight, e.g. position, forward speed and altitude on the various response quantities are discussed, with particular emphasis on the importance of the manoeuvre margin. To avoid possible confusion of terms the two types of elevator‐induced manoeuvre mentioned above and discussed in this paper are defined as follows:

DURING a test flight on a prototype Javelin aircraft, a flutter incident occurred involving the loss of both elevators. The pilot was fortunately able to continue flying the aircraft using the tail trimming control and subsequently made a crash landing. At the time of the incident all the recording instruments were running. These included an automatic observer, a chart recorder of control circuit forces and a two‐axis vibrograph which was mounted at the top of the fin. A copy of part of the record from the latter instrument is shown in FIG. 1. The upper stepped line is the timing signal and the lower trace gives the lateral displacement at the top of the fin, the rather spasmodic oscillations corresponding to the fin bending frequency of 4·8 c.p.s. The diverging oscillation shown on the centre trace corresponds to the vertical displacement at the top of the fin. From this and a similar record obtained from the elevator circuit force recorder, it was concluded that the elevators fluttered symmetrically at a frequency between 21 and 22 c.p.s.