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FOR a number of years now it has been evident that a successor to the well‐tried Vickers Viscount and Convoir 240/340/440 series was required. However, the big problem was to design an aircraft such that its economics and passengerappealweresub‐stantially better than the machines it would ultimately replace. Other important factors which had to be con‐sidered were improved reliability, easier and cheaper maintenance, higher standards of safety and means of reducing ramp times. Furthermore, the difficult choice of passenger capacity and cruising speed had to be made. Probably the easiest decision was to employ the twin‐engine configuration with the power plants placed in the now familiar rear position, one on cither side of the fuselage.

Pressure pulsations and vibration working condition lead to dynamic troubles in hydraulic devices. It is highly desirable to be able to estimate the durability at the design stage so that appropriate maintenance period can be determined for safety and reliability. The purpose of this paper is to propose a quantitative evaluation method for pulsation and vibration based on reliability.

Pressure pulsations are approximately treaded as a stationary random process. The principle of transform function and fluid network chain rules are used to disassemble the hydraulic power unit into the series‐system. Mean square deviation of dynamic stress under the pumping source white noise exciting was calculated based on frequency responses. Statistical regularity of displacement and stress responses of pipelines under external random vibration are obtained by the spectrum analysis. Both the first‐passage failure criterion and fatigue damage accumulation failure criterion are adopted to analyze the dynamic pressure reliability of hydraulic pipelines.

The terminal joint, bellow pipe and pipe clamps are verified as the weak location of the pipelines. The mean square deviations of pulsations and vibration response influence the pipelines reliability. The results indicated that the preventative design method of controlling the pressure below 10 per cent of rated pressure does not meet the security specification of the hydraulic power unit.

The paper proposes a quantitative evaluation method for random pressure pulsation and external vibration based on reliability, which provides a new approach for the safety assessment and design of hydraulic pipelines.

THE Trident IE fuel system, designed to operate on cither kerosene or JP.4, has a straightforward layout with few controls. Five integral tanks (FIG. 1), comprising four in the wings and one in the centre section, give a total of 5,880 Imp. gall, of which 2,000 Imp. gall, are contained in the centre tank. (Total fuel capacity of the Trident 1C is 4,960 Imp. gall, with 1,160 Imp. gall, in the centre tank.) Each wing inner tank has slightly more than twice the capacity of the outer.

THESE notes have been prepared because it is a fact that there is no publication available to the ordinary aeroplane mechanic which gives him the essential information which will guide him in the overhaul and maintenance of hydraulic equipment. There are only one or two books which even touch on the subject other than the official (and very excellent) R.A.F. publication, A.P. 1803.

AS is to be expected, the various systems on the Trident 2E closely follow those evolved for the Tridents 1 and 1E, except for the changes in the fuel system necessitated by the introduction of the fin fuel tank, and the embodiment of a turbine‐compressor type of cold air unit in the air conditioning system.

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 floor area of the Ferranti Environmental Test Laboratories at Silverknowes, Edinburgh has been increased — from 9,000sq ft to 27,000sq ft — and the test facilities greatly expanded and improved.

Inspection prior to retrofitting computer numerical control on a two‐metre‐cube, 35‐tonne Dixi horizontal NC borer revealed so little wear that there was no detectable alteration to the two‐micron‐deep hand‐scraped surface of the slideways after 11 years of virtually continuous double shift operation. Neither was there are measurable change in the alignment of the slideways or spindle.