The second part of this survey closed a little after the termination of the First World War. By then the utility of the aeroplane as an instrument of warfare had been amply demonstrated. Moreover, something of its future potential in civil use had been indicated by such British achievements as the first transatlantic flight by Alcock and Brown in 1919, albeit in a Vickers Vimy biplane of otherwise limited performance. It was also at this time that the new aerodynamic ideas of Kutta, Zhukovskii and Prandtl reached Britain. All such thinking pointed inevitably to the greater speed, efficiency and economy to be expected of the streamlined monoplane.

This paper presents an algorithm to solve the three-dimensional unsteady Euler equations on unstructured tetrahedral meshes using a dynamic mesh algorithm. The driving algorithm is an upwind biased implicit second order accurate cell-centered finite volume scheme. The spatial discretisation technique involves a naturally dissipative flux-split approach that accounts for the local wave propagation characteristics of the flow and captures shock waves sharply. A continuously differentiable flux limiter has been employed to eliminate the spurious oscillations near shock waves, generally arising in calculations involving upwind biased schemes. The temporal discretisation is also second order accurate and uses a Newton linearisation for unsteady calculations. To calculate time dependent flows a dynamic mesh algorithm has been implemented in which the mesh is moved to conform to the instantaneous position of the body by modelling each edge of each cell by a spring. The paper presents a description of the solver and the grid movement algorithm along with results and comparison that assess their capabilities.

Routine periodic audiometry performed as part of the statutory medical examination of flight crew employed by a major international airline indicated that up to 27–5% may suffer noise induced hearing loss, with 10-8% showing unilateral hearing loss. This was considered to result from the practice of listening to radio communications through a headset covering one ear only, leaving the other ear uncovered to allow direct conversation between crew members on the flightdeck. Ambient noise levels at the crew seats and noise levels from crew headsets were measured on a sample of aircraft and routes using a Kemar acoustic manikin. Noise levels on the flightdecks were 70-79dB(A) Leqaveraged over a flight of typically seven to ten hours duration. Noise levels from headsets were 77-89dB(A) Leq being 80dB(A) or higher on 80% of flights, and 85dB(A) or higher on 40% of flights. Five prototype or production active noise reducing (ANR) headsets were evaluated in flight and in the laboratory. It was shown that the better examples, worn to cover both ears, would allow flight crew to reduce headset volumes so reducing risk to their hearing.