The structural problems introduced by the kinetic heating of high speed aircraft require a radical extension of what has hitherto been regarded as the normal domain of structural theory. Aerodynamics, for example, cannot be regarded as a self-contained subject which merely provides basic data for the structural worker. Certain aspects of aerodynamic theory, particularly the mode of heat generation, have to be considered simultaneously with the structural problem. Thermodynamics and metallurgy are still more closely integrated with structural theory. The laws of heat transfer, and the variation of material properties with temperature, are both essential factors in the structural analysis.

The main task of the aircraft accessory designer is to provide fully developed and type-tested equipment to meet the needs of the Aircraft Industry at the time when a new aircraft is at a stage in construction where accessories are to be fitted.

But he must do more than this, particularly with equipment for multi-engined aircraft. He must endeavour to set up and test a complete aircraft ancillary power system. This is particularly important for the electrical system, where two or more generators have to operate in parallel, successfully sharing the load on the system and providing over-voltage and other protection in such a manner that failure of the complete system does not result from failure of one engine, generator or its attendant equipment.

Today there is growing interest on the part of aeronautical engineers in forgings of large size, for three main reasons. Certain types of forgings will naturally need to be bigger as the aircraft itself becomes bigger; more composite structures are being replaced by single components made as forgings; and there is an increasing use of complex units machined directly from blocks of metal which are too big in at least one dimension to be made as extrusions or rolled plate. It is with these larger forgings that we are mainly concerned. Their production presents many serious problems. It is reasonable to hope that some of these will be overcome as experience grows and techniques are improved but others seem to be inherent in the materials used and must be appreciated at the design stage of the component if fully satisfactory service is to be obtained.

How much is known about high altitude clear air turbulence? Sufficient to show that aircraft may, with little or no warning, experience bumpiness which the pilot would describe as “ moderate ” or, on occasions, “ severe,” at altitudes up to at least 40,000 feet, thus including altitude bands where commercial jet aircraft will be flying during the next few years. The phenomenon, therefore, is of significance to airline operators and the requirement is for the aircraft commander to be supplied with sufficient information to enable him to avoid such turbulence, or to provide him with adequate warning so that crew and passengers can be properly prepared for it. This does not imply that there is evidence to suppose that clear air turbulence may be of such severity as to affect the safety of a flight. It is important, however, to take good care of the passengers and their comfort is an essential consideration.

The work reported in this Note originally formed part of a comprehensive investigation into the fatigue strength of magnesium alloy ZW2 (2 per cent. zinc, 0·65 per cent. zirconium) in sheet form. The major portion of the programme was eventually cancelled but the tests herein described are sufficiently self-contained to be repotted by themselves. Direct stress fatigue determinations were made on small round test pieces machined from ¾ in. thick plate, at mean stresses of 0, 4,000, 8,000 and 13,000 lb./in.2. Static and rotating bar fatigue tests were also made.

The primary purpose of this note is to draw attention to the powerful influence of Coriolis forces and flapping pin offset on helicopter stability. It is shown that, for a conventional rotor of small offset, the damping in pitch and the flight stability are greatly reduced by the absence of drag hinges, an effect which may explain the use of stabilising bars on the successful helicopters which use this configuration. A “see-saw” rotor without some form of synthetic damping would be very unpleasant to fly by present-day standards.

In a previous note the authors gave a method of solution for the problem of a finite rectangular plate under non-normal loading. The problems considered in the present note are those of constant and variable inclined loading on a circular plate.