| RB199 | |
|---|---|
| |
| RB199 at the Royal Air Force Museum Hendon | |
| Type | Turbofan |
| Manufacturer | Turbo-Union |
| First run | 1971 |
| Major applications | Panavia Tornado |
The Turbo-Union RB199 is a turbofan jet engine designed and built in the early 1970s by Turbo-Union, a joint venture between Rolls-Royce, MTU and Aeritalia. The only production application was the Panavia Tornado.
The RB199 originated with a requirement, in 1969, to power a new European multirole combat aircraft (MRCA) called the Panavia MRCA.[1] 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.[2] 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.[3] Rolls-Royce took over Bristol Siddeley in 1967 so the configuration for the RB199 was decided jointly, a three-shaft engine.
The overall design concept for the international collaborative program, three shafts and a bypass ratio (BPR) of about 1.2, 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.[4] 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 reheat. The reheat used cold air combustion techniques, described by Sotheran[5] and which were derived from their experience with ramjets and plenum chamber burning (PCB) in Pegasus front nozzles.[6] 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.[7]
A three-spool arrangement reduces the pressure ratio on each compressor[8] 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.[9]
The RB199 first ran on 27 September 1971 at Patchway, UK.[10] 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 and 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."[11]
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."[12]
Data from Rolls-Royce and MTU.[16][17]
