The New Zealand Government takes airspace safety very seriously. The level of safety in New Zealand airspace is measured by the number of recorded airspace incidents. An airspace incident can be thought of as a failure in the chain of operations in the air traffic system when it is provided with an air traffic service (ATS). Some of these incidents result in a loss of separation between aircraft, varying from slight to a very serious loss with a significant risk of collision, known as a near collision. New Zealand’s Civil Aviation Authority (CAA) identifies the causal factors for all airspace incidents using the Reason model of human error, divided into three areas; active failures committed by individuals involved in the incident, local factors relating to the task and the ATS environment and organisational factors originating in the managerial and organisation spheres of the ATS provider. Based upon the CAA’s database, this paper analyses trends in controller caused incidents in the NZ airspace during the period 1994 to 2002 in six controller caused categories. The results indicate that for controller caused incidents, execution errors dominate the active failures category, while in the case of local factors, poor concentration/lack of attention, inadequate checking and controller workload are the dominant factors. For the organisation category, poor planning and inadequate control and monitoring dominate. These results should form the basis of a robust and transparent framework for intervention mechanisms by the New Zealand Civil Aviation Authority for enhanced airspace safety.

The interaction of a helicopter tail rotor blade with the tip vortex system from the main rotor is a significant source of noise and, in some flight states, can produce marked reductions in control effectiveness. This paper describes a series of wind-tunnel tests to simulate tail rotor blade vortex interaction with a view to providing data for the development and validation of numerical simulations of the phenomenon. In the experiments, which were carried out in the Argyll wind-tunnel of Glasgow University, a single-bladed rotor located in the tunnel’s contraction was used to generate the tip vortex which travelled downstream into the working section where it interacted with a model tail rotor. The tail rotor was instrumented with miniature pressure transducers that measured the aerodynamic response during the interaction. The results suggest that the rotor blade vortex interaction is similar in form to that measured at much higher spatial resolution on a fixed, non-rotating blade. The combination of the two datasets, therefore, provides a valuable resource for the development and validation of predictive schemes.

Control activity is a recognised gauge of pilot workload and recent research has employed wavelet decomposition to classify discrete control actions into categories such as guidance and stabilisation. The aim of the present work is to extend the wavelet approach so that workload may be quantified through sets of rules based on appropriate control activity metrics. The rules are derived from data collected in piloted simulation trials of a variety of flying tasks involving a number of pilots and different helicopter configurations. Statistical tests are then applied which test the efficacy of the derived rules. The immediate aim of the research is to establish whether workload can be successfully predicted from control responses. The underlying goal however, is to be able to predict workload ratings from desktop simulations in order to provide indicative workload information at the design stage. The contribution of the current study to this objective is discussed.

The effect of multigrid acceleration implemented within an upwind-biased Euler method for hovering rotor flows is presented. Previous work has considered multigrid convergence for structured single block rotor solutions. However, for forward flight simulation a multiblock approach is essential and, hence, the flow-solver has been extended to include multigrid acceleration within a multiblock solver. The requirement to capture the vortical wake development over several turns means a long numerical integration time is required for hovering rotors, and the solution (wake) away from the blade is significant. Hence, the solution evolution and convergence is different to a fixed wing case where convergence depends primarily on propagating errors away from the surface as quickly as possible, and multigrid acceleration is shown here to be less effective for hovering rotor flows. Previous single block simulations demonstrated that a simple multigrid V-cycle was the most effective, smoothing in the decreasing mesh density direction only, with a relaxed trilinear prolongation operator. This is also shown to be the case for multiblock simulations. Results are presented for multigrid computations with 2, 3, and 4, mesh levels, and a CPU reduction of approximately 80% is demonstrated for 4 mesh levels.

A statistical approach is followed for prediction of tolerences of notched strength of composite laminates using the recently proposed improved inherent flaw model (IFM). In order to examine the validity of this approach, the existing fracture data on graphite/epoxy composite laminates containing central holes and cracks were used. The notched strength estimations are found to be within the range of tested values.

The present work investigates feedback control of flutter using piezoceramic strain actuators. A two degree-of-freedom oscillating airfoil model with the air loads simulated assuming unsteady aerodynamics is considered. Various feedback measurement combinations for SISO feedback control and strain actuation in the heave and pitch direction are studied to quantify their effect on flutter. The effect of sensor placement on the airfoil, for combined pitch and heave measurement feedback, is also studied. The results show that for a given aeroelastic system, sensor location is an important parameter in realizing an increase in the flutter speed. It is demonstrated that the flutter speed can be increased by more than 50% through strain actuation in the pitch direction.