AERO ENGINES

The aero engine side of Alvis was an important facet of its history, told in Roy Probert‘s book  “Leonides”. Roy died on June 17th 2021 at the age of 86. His legacy is a detailed history of the Alvis company’s aero engine activities and his research into the early years of the Alvis company. Much of his accumulated documentation is now held in the Archive.

We now hold copies of the Leonides manual which are available in both hard copy and digital form for members of the trust. The contents are:

Roy was authorised by Alvis to provide service information for the Leonides aero engine in his retirement which responsbility has now been passed to John Boswell. John has a background in the servicing and operation of these engines in a supervisory capacity and also as an instructor on the engine type while serving in the Royal Air Force. He holds all the relevant technical data and all enquiries for information should be channelled to him via ASK A QUESTION

Roy was with Alvis for 27 years, becoming a Quality Engineering Manager. He was given the memorabilia of the late George Clarke, then Chief Engineer when he retired from Alvis. He has contributed the following….

ALVIS AND THE AERO ENGINE

The decision by Alvis in 1935 to enter the realm of aero engine manufacture was bold, considering that it had no experience in this field of engineering. The company were aware that there was a market opportunity for a British engine of greater power than those currently then available and reasoned that their ambitions would best be served by building under licence an existing foreign engine they could learn from and further develop to meet that need.

T G John had some background to doing this from his time at Siddeley’s in Coventry where he had previously held the position of Works Manager with a brief to improve the performance and reliability of a badly designed engine that would eventually emerge as the Puma.  Alvis’s Chief Engineer, Captain Smith-Clarke, although having had close association with acceptance standards for aero engines during his time as a government inspector, was less enthusiastic at the idea having witnessed the pitfalls of meeting the increasing quality and performance requirements for an aero engine.  However, they pressed ahead and entered into negotiations with a leading French engine producer, Society des Gnome et Rhone of Paris, and secured a contract that would give realisation to their ambitions.

Such was their enthusiasm and confidence in the venture that a modern new factory was built on land the company already owned adjacent to the existing car factory in Coventry.  The new premises were of the most advanced design in the country at the time, in respect of facilitisation, providing a high degree of independence from subcontracting by incorporating most of the manufacturing process requirements under one roof.  Complimenting a large engine development test bed acoustically designed in conjunction with The National Physical Laboratory, were machine shops where each machine was self-powered dispensing with the overhead pulley and belt drives that characterised production plants of that time.  Incorporated also were a pattern shop and a foundry smelting steel, iron and aluminium.  Metallurgical, physical and chemical laboratories, and x-ray cells.  Electro-plating shops, a coppersmiths, furnace heat treatment department, functional testing rigs and a toolroom producing all the necessary jigs and fixtures.  In fact everything to ensure controlled, quality production.

Recognising that they would need government support for the enterprise, T G John had earlier approached the ministry and gained tacit approval on the understanding that the engines Alvis were to produce would be given imperial sizing and accommodate British accessories as all others did, and Alvis gave assurances to this effect.  However, the turn of events in the following months were to see government take a hostile stance towards Alvis’s intentions and refusal to buy engines of foreign origin.  In retaliation to this the company intensified the design of its own, wholly British engine that in the months ahead was to emerge as Leonides. (1938).

With the approaching threat of war with Germany, Alvis were forced to shelve their interests in aero engine development and to assist the war effort, the new factory making a valuable contribution to the manufacture of numerous aircraft parts, plus other related activities.

Serious production of their 9-cylinder radial engine began in 1947, competing uncertainly at that time in the wake of the gas turbine against which its prospect for success was a gamble.  But this modern and aesthetically pleasing engine found favour by its performance characteristics as an ideal power unit for certain post-war aircraft design applications, notably as suited to powering a new generation of rotary wing aircraft.  In order to adapt the engine for the emerging helicopter designs, Alvis reconfigured the engine so it would operate lying on its back with the drive shaft uppermost.  Unique but perfectly suited to the requirement.

The success of Leonides grew steadfastly throughout the 1950’s and its power was increased from the original engine figure of 450hp to reach 615hp, and eventually saw the arrival of a 14-cylinder version producing 750hp.  But the tide of aircraft engineering progress was to herald the decline of the piston engine as a power unit for future aircraft by the end of the decade.  Leonides had a production span of 18 years during which time it found notable application in a number of fixed wing and rotary wing aircraft an well as experimental design uses the most unique of which was as the power unit for the first hovercraft.

Alvis’s aero engine era was a chapter to be proud of in the history of this renowned company.  A full and detailed account of the engine’s development and career is given in a book devoted to the subject.  ‘Leonides’ – The Alvis Aero Engine by Roy Probert is published in hardback and obtainable from us, price £16.95 plus post and packing. Just leave a comment if you would like a copy.

Roy’s book makes a fascinating read and an insight into the efforts put into making the aero engine a commercial success after the war with John Parkes as MD. This photo is extracted from Reflections in Retirement published in the Bulletin compiled by Eric Stapleton:

Alvis advertised their products widely and here are some examples, courtesy of Aviation Ancestry (and thanks to Dave Culshaw for the research):

The process of digitising the Leonides Manual has started and this Chapter 9 on Dismantling is now available to download.

This Review of Roy’s book was published by the VSCC in the Winter 2011 edition number 247.