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IN order to obtain machines of large carrying capacity, there is a tendency to increase the number of power units, and it is of great interest to consider the effect of this policy upon safety in flight. It is obvious that, if all the power units are of the same construction, the possibility of failure of one engine in a machine fitted with two engines is twice that in a machine fitted with one engine, so that in general the probability of one unit going out of action in a multi‐engined machine is proportional to the number of power units employed. In the case of a single‐engined machine horizontal flight cannot be maintained after the engine fails, and unless the failure occurs in the vicinity of a safe landing ground disaster may result. In the case of a multi‐engined machine, however, if level flight can be maintained on the power obtainable from the remaining units, it may bo possible to arrive at a safe landing ground without further trouble. The question, therefore, arises as to which factor is the more important, the increase in the probability of failure, or the ability to fly level with an engine out of action.

THE current discussions to define a multi‐role aircraft for the mid 1970s have been notable for dissension of opinion on the choice between one engine or two. This remarkably basic choice has been with us since pioneer days — Lindbergh's acid comment on the value of two engines was ‘twice the trouble’, while the very fact that there are many aircraft in use of both layouts indicates that there has not been a clear case for choosing cither. Not, that is, until very recently, when statistics on the loss rate of both single and twin‐engined aircraft have confirmed that a definite margin does exist. This is the key to the whole choice between two engines or one, for it is necessary to compare not only the initial costs, but also the maintenance and operating costs, replacement of lost aircraft, and pilot training costs to achieve a realistic comparison on an overall cost basis. As with most cost‐effective arguments a strong danger exists of losing sight of primary objectives in a welter of tenuously related facts. The objectives in the choice between two engines and one is simple; which configuration fulfills an operational requirement at the least overall cost.

Three‐Engined Types, Twin‐Engined Types and Single‐Engined Types.

RISING FUEL, service and maintenance prices have highlighted the need for strict cost monitoring of basic flying training, both in the military and commercial spheres. This requirement has become particularly acute in the multi‐engined aircraft primary training context. The use of conventional twin‐engined aircraft for this purpose is expensive, both in terms of first cost and in operation. Moreover, the simulation of the “engine out” condition can, on occasions, prove hazardous.

Lockheed has designed a twin‐engined derivative of its famous four‐engined C‐130 Hercules freight aircraft with the same size hold to carry 22 500 lb of cargo over 500 miles.

BY way of introduction we shall explain that we have used the rather unwieldy term “composite‐engined aeroplane” to define the type of aircraft with which we at Ryan are working. This is one having two power plants of different kinds, which are, in the FR‐1, Fireball, a nine‐cylinder Wright Cyclone engine of 1,820 cubic inches piston displacement and a General Electric 1–16 turbo‐jet engine of 1,600 pounds static thrust.

The present challenge for many service firms is to develop an offering that is flexible and open for tailoring and at the same time achieves efficiency through standardizing processes. Modularity has been suggested as being one tool for achieving this. The goal of the present study is to find out how services provided in modular form (here referred to as service modularity) can exert an influence on the value perception of the customer in the professional services field.

Empirical part consists of a case study of a large provider of professional services involving construction, engineering, procurement and project management service. Data were gathered by semi structured theme interviews of representatives of the case company and representatives of two of its customers.

The modular processes had an influence on the customer's expectations that are related to the experienced quality of the service, and hence they create value for the customer. In addition to the service outcome, the modular processes enhanced the customer's trust in the service provider's employees and their skills in co‐operating in a suitable way during the service process. The organizational modularity eased the customer's tasks of managing the project implementation.

The present study contributes the knowledge related to modularity in business services by incorporating the knowledge from the theoretical discussion on customer perceived value.

ON April 7, a three‐engined Wibault monoplane took‐off from Le Bourget, the Paris airport, for Toulouse, with a consignment of mail for South America. This flight marked the inauguration of a new all air‐mail service to South America, which will operate twice a month in each direction. From Toulouse the mail was carried to Casablanca in a Bréguet 393, a new three‐engined “sesqui‐plane” for commercial service. From Casablanca the mail was carried to Dakar, the jumping‐off point for trans‐Atlantic services in the Senegal, in a three‐engined long‐range version of the Wibault low wing monoplane. At Dakar the consignment of mail was loaded into the hold of the Blériot 5190 “Santos Dumont,” flying boat, which took‐off for Natal in South America. In exactly 43 hours and 52 minutes from the take‐off at Paris, the mail was landed at Natal, whence it was further transported by air to South American cities reached by Air France.

IN recent years the problems involved in flight on asymmetric power have attracted increasing attention and curiosity. It is safe to state that at the beginning of the British era of high‐powered twin‐engined aircraft, of which the Blenheim I is a representative type, pilots regarded an engine failure at any time as a major problem. A failure of the worst type—on take‐off—was thought to result invariably in loss of control, with the attendant after‐effects on aircraft and crew.

THE four‐engined bomber which was used to fly M. Molotov from Moscow to Britain U.S.A. and back, is an interesting type. The accompanying illustrations, the only ones yet available for publication, give a general impression of the aeroplane. The type is the obvious modern development of the early four‐engined monoplane bomber designed by A. N. Toupolev some fifteen years ago—the tail shape closely resembles that of the early machines. The latest four‐engined Russian type, before this aeroplane became kuown, was the TB‐6, which has already been illustrated in AIRCRAFT ENGINEERING. The present machine is undoubtedly a. “ cleaned‐up ” version of the TB‐6, which it resembles in general outline in the wing shape and in the deep inner engine nacelles.