Editing Turbo-Union RB199 (section)

==Design and development==
[[File:Turbo Union RB199 Montrose.jpg|thumb|Turbo Union RB199 turbofan engine on display at Montrose Air Station Heritage Centre]]
The RB199 originated with a requirement, in 1969, to power a new European [[multirole combat aircraft]] (MRCA) called the [[Panavia]] MRCA.<ref>Jane's All The World's Aircraft 1975-76, {{ISBN|0 531 03250 7}} p.112</ref> The engine requirements to meet the Panavia MRCA specification were significant advances over current engines in thrust-to-weight ratio, fuel consumption and size. The final selection of the engine for the MRCA was made between a new European collaboration, [[Turbo Union]], with the RB199, and Pratt & Whitney who proposed the JTF16.<ref>Rolls-Royce Aero-Engines, Bill Gunston 1989, {{ISBN|1 85260 037 3}}, p.232</ref> The Panavia MRCA would later be called the [[Panavia Tornado]].

Advanced engine studies at [[Bristol Siddeley]] had already been done to support the [[BAC/Dassault AFVG]] and were based on the Pegasus two-spool arrangement. At [[Rolls-Royce]], where the three-shaft RB211 engine was in development, three shafts were considered better.<ref>The Birth Of Tornado, Royal Air Force Historical Society 2002, {{ISBN|0 9530345 0 X}}, RB199- The Engine For Tornado by Dr. Gordon Lewis, p.50</ref> Rolls-Royce took over Bristol Siddeley in 1967 so the configuration for the RB199 was decided, a three-shaft engine, but fundamentally to Bristol's design and Bristol's higher technology. 

The overall design concept for the international collaborative program, three shafts was decided by Rolls-Royce. The bypass ratio was chosen for long-range, with low fuel consumption, particularly when throttled back. The selected BPR also gave a higher reheat boost than with smaller values used on similar engines.<ref>https://archive.org/details/DTIC_ADA129168?q=agard+cp+324,AGARD Conference Proceedings CP No.324,Engine Handling,{{ISBN|92 835 0327 9}} CP 324, Round Table Discussion p.RTD-8</ref> The design of the individual modules was shared between Rolls-Royce, MTU and Fiat according to their existing expertise. Rolls-Royce designed the fan using scaled-down Pegasus knowledge, the combustor, the high pressure (HP) turbine and the [[afterburner|reheat]]. The reheat used cold air combustion techniques, described by Arthur Sotheran<ref>{{Cite web|url=https://www.freepatentsonline.com/3633362.html|title = Reheat Combustion Apparatus for Bypass Gas Turbine Engines}}</ref> and which were derived from their experience with ramjets and plenum chamber burning (PCB) in Pegasus front nozzles.<ref>https://archive.org/details/DTIC_ADA202495?q=agard+cp+422, AGARD Conference Proceedings CP No.422, Combustion and Fuels in Gas Turbine Engines,{{ISBN|92 835 0465 8}},High Performance Turbofan Afterburner Systems p.12-2</ref> Fiat had built turbines for the Viper so designed the low pressure (LP) turbine as well as the final nozzle. MTU designed the intermediate pressure(IP) and high pressure (HP) compressors, the IP turbine, and the thrust reverser.<ref>Flight International, 22 August 1981,RB.199: Compact Tornado power, p.552-558</ref>
An interesting read from MTU's very early RB199 days  can be found in https://aeroreport.de/en/aviation/rb199-development-the-engine-that-started-it-all.

A three-spool arrangement reduces the pressure ratio on each compressor<ref>https://archive.org/details/DTIC_ADA129168?q=agard+cp+324, AGARD Conference Proceedings CP No.324,Engine Handling,{{ISBN|92 835 0327 9}}, p.25-2</ref> so no variable stators were needed. To meet the short afterburner requirement an arrangement known as mix-then-burn, as used in current engines, was not possible because it was too long and heavy. The RB199 used a much shorter arrangement known as mix/burn.<ref>https://archive.org/details/DTIC_ADA202495?q=agard+cp+422, AGARD Conference Proceedings CP No.422, Combustion and Fuels in Gas Turbine Engines,{{ISBN|92 835 0465 8}},High Performance Turbofan Afterburner Systems p.12-5</ref> 

The RB199 first ran on 27 September 1971 at Patchway, UK.<ref>{{cite book |author=<!--Staff writer(s); no by-line.--> |title=Flight International World Aircraft and Systems Directory |publisher=Reed Business Information Ltd. |page=187 |date=2001 |isbn=0-617-01289-X}}</ref>  It was flight-tested using an [[Avro Vulcan]] with the engine installed in a [[nacelle]] that was representative of the Tornado aircraft. The Vulcan first flew with the RB199 in 1972.

Service flying with the Royal Air Force, German Navy and German and Italian Air Forces in the European environment showed normal failure mechanisms for turbine blades, [[thermal fatigue]], [[creep (deformation)|creep]] and high cycle fatigue ([[High-cycle fatigue|HCF]]) so development started on replacing the initial production equiaxed blades with single-crystal ones which last longer at high temperatures.

Sand ingestion tests had been done and passed as part of the qualification for service introduction but operating in desert conditions with the [[Royal Saudi Air Force]] produced new problems. Frequent flying in air carrying different sizes of sand particles caused deposits on the HP turbine blades from sand passing through the combustor. In addition, sand carried with the cooling air through the blades blocked the cooling holes. Single crystal blades were being introduced to improve the life of the blades for the European operating conditions and revised cooling hole arrangements were introduced at the same time to reduce the detrimental effect of sand on blade cooling. With incorporation of these blade processing and cooling changes "Desert Storm Tornado aircraft flew some of the most arduous missions of any Allied aircraft with reliability no worse than peacetime and no engines were rejected for HP Turbine blade defects."<ref>https://archive.org/details/NASA_NTRS_Archive_19950013267?q=agard+cp+558, AGARD Conference Proceedings CP No.558, Erosion, Corrosion, Foreign Object Damage Effects in Gas Turbine Engines,Paper 1, Out of Area Experiences with the RB199 in Tornado</ref>
   
Looking back on the RB199 program in 2002 Chief Engineer for the RB199, Dr.Gordon Lewis, concluded "The final production standard provided satisfactory reliability and performance."<ref>The Birth Of Tornado, Royal Air Force Historical Society 2002, {{ISBN|0 9530345 0 X}}, RB199- The Engine For Tornado by Dr. Gordon Lewis, p.50</ref>