(Photo and supporting information from Rolls-Royce)
The original Viper engine was produced by Armstrong Siddeley (later Bristol Siddeley and now Rolls-Royce) to a requirement for a 10-hour life small jet engine and was intended to be fitted to airborne target drones. The engineers built in some leeway to allow for ground tests and were anticipating 14 hours between overhauls. However, the first tests in 1951 revealed a basic engine core which was so well designed that it would eventually be upgraded and improved beyond the wildest dreams of those pioneering engineers.(source Air Scene UK)
Arguably best known in the Jet Provost / Strikemaster, they served most successfully of all in the Hawker Siddeley HS125. And gone, but not forgotten, are the Shackleton Mk.3 aircraft that had Vipers fitted into the outer Griffon nacelles for additional takeoff boost.
Viper engines were also manufactured under licence in numerous overseas countries for fitting into a wide variety of aircraft. Sud Aviation in France fitted their Mach 2 SO.9000 Trident fighter with MD530 (Viper 5) engines on the wingtips to supplement the fuselage mounted rocket engine. A similar type to the HS125 is Italy’s Piaggio PD808 still in service with the AMI in an ECM role, fitted with a pair of Viper 20s. Other overseas producers/overhaulers included India (for the Kiran), South Africa (for the Impala), Romania (for the Orao and IAR99), Yugoslavia (Orao, Galeb, Jastreb and Super Galeb), Brazil (for the MB326) and Italy (MB326, MB339 and PD808).(source Air Scene UK)
In fact it is the latest production version, the Viper 680, that powers the Aermacchi MB339. It also powers the remotely piloted Jindivik aircraft operated by the UK's Royal Air Force as a target towing vehicle for pilot training.
So with more than 5,500 engines delivered and over 13 million flying hours, this may not be an engine that has touched us all in the way a Rolls-Royce RB211 most probably has. But with the current production and applications the Viper has a real chance of becoming the first 100 year old desgn still in manufacture - how many aerospace products can say that?
I'm a conscientious man... when I throw rocks at seabirds I leave no tern unstoned. (Ogden Nash)
Et nom de dieu! C'est triste Orly la dimanche (Jacques Brel)
Ermanno Bazzocchi, the Aermacchi chief designer and eventually AD (my entry for the Greatest Persons list) would have shared this view. Acting in his staff, we considered many and many alternative engines for the MB339 (not really easy to be installed there) but he used to remark: the only better engine than the Viper is the next Viper.
A remark: to my knowledge, the Viper was born as an expendable engine for the Australian Jindivik drone / RPV and retained (with the J85) for a long time one of the best - maybe the best - T/W ratio for mil dry turbojet / turbofan engines, while growing up eventually to become a very successful and widespread engine.
It is remarkable how the PD-808, known as VespaJet unofficially, served for more than 25 years without even a problem... the 2 Viper MK.526 engines had the task of running BOTH DC generators and alternators, the latter only for de-icing and external heating equipment ... AC power to avionics, instruments and so on was powered by a set of 3 inverters ...
You could spot a PD-808 approaching the hangar by it's distinctive whistle ...
It was with some interest that I read your comment about the Rolls Royce Viper engine, which was designed and initially developed by Armstrong-Siddeley Aircraft Gas Turbines, of Parkside Coventry.
As a young graduate engineer in the design and evelopment department of Armstrong-Siddeley's from 1949 to 1951 I had been engaged in the development of the Armstrong-Siddeley Mamba turbo-jet and its sister engine the Armstrong-Siddeley Adder pure-jet engine. Both of those were excellent engines with a small frontal area profile and individual combustion cans. However they both suffered to some extent from problems of matching the turbines to the axial compressors.
The Viper was a new design to a Ministry specification for an expendable jet engine to power the Jindivik target towing aircraft being developed for use at the target range at Woomera in Australia. Having had the experience of working on the Adder, it fell to me to arrange and carry out the very first-ever test on the first prototype Viper, which, if I can recall correctly was in April 1951. John Marlow was the Chief Development Engineer and he was present during that test. The main functions initially being recorded were thrust and fuel consumption. After going through the preliminary run-up procedures, we put some power on to the engine and on calculating the specific fuel consumption, Johnnie Marlow thought I'd got something wrong, so would I do it again. I repeated the calculations with Johnnie looking over my shoulder and, agreeing with what I did, He was totally astounded at the result and performance and was immediately and joyously telling all around that at last Siddeley's had matched a turbine and a compressor.
The prototype was quite remarkable. The first few rows of the axial compressor had plastic blades, the oil pumps for the shaft bearings were simple plunger pumps which were bought from the local motor cycle makers. However, part of the real success was annular combustion chamber with its inherent simplicity. Siddeley's had already had extensive experience of annular combustion chambers with their Sapphire engine, which in fact was used by the US Army to power their fleet of Canberra bombers which they built under licence, although I believe that the original annular combustion chambers were inherited from Metrovickers whose designs had been sold to Rover cars before being transferred to Siddeley's.
Eventually Siddeley's were merged with Bristol Engines to form Bristol Siddeley, which eventually was absorbed by Rolls Royce who continued and advanced the Viper design to what is indeed the longest production aircraft engine in the business. I believe it is from that merger that most Rolls engines have the pre-fix RB.
Shortly after running the Viper test, I left Coventry to take up an academic lecturing post in Aberdeen, where I eventually became Associate Head of the School of Mechanical and Offshore Engineering in what is now the Robert Gordon University. But I look back on those days at Parkside and the testing bays at Ansty with fond memories and some pride.
Bert Hosie, BSc,CEng, FIMechE, Fellow of RGU, Inverurie, Aberdeenshire.
I have just been checking why the image in my original post has disappeared and it seems the Rolls-Royce have removed the Viper from their engine list on their website. Whilst there are a few references to service contracts for the engine, I can no longer find any details of the engine as a product.
Does this mean that the engine has now gone out of production or has it just fallen to sufficiently small numbers to not be worth mentioning? Can anyone post an update on its status? Ta.