BAE Systems is poised to hand over the first re-engined Sepecat Jaguar GR3 strike aircraft to the UK's Royal Air Force in February, while a two-seat T4 is due to follow towards mid-year. Operational clearance is due around the same time.

The programme, which involves Rolls-Royce and the UK Ministry of Defence's aircraft maintenance organisation DARA St Athan, is intended to improve the engine's maintainability and provide a thrust improvement, although the latter is not as great as predicted when the £105 million ($150 million) contract was signed in 1998.

BAE will modify the first two aircraft and St Athan another 58; R-R will upgrade 122 engines. Three aircraft are already at St Athan, which is due to deliver the last in 2005.

R-R is upgrading the Jaguar's Adour Mk104 engines to Mk106-standard by combining the Mk871 unit powering BAE Hawks with the reheat section fitted to export Jaguars. BAE was flying a test Jaguar with the new engine last year, although this aircraft is not representative of the service standard.

A Rolls-Royce source says the "imperative is more reliable propulsion," while a source from the MoD's Defence Logistic Organisation (DLO), which is the contracting agency, says the Mk104 has reliability and maintainability problems that required investment to remedy the situation. He says the Mk104 engine suffers around six engine failures per 1,000 flying hours, which is expected to fall to two per 1,000hwith the Mk106.

When R-R won the contract it predicted a 10% thrust increase, useful in an aircraft notorious for being under-powered since it came into service in the mid-1970s. The R-R source says the increase is in the region of 5-6%. The company acknowledges problems with hot-spots in the jet pipe, which have been cured with a combination of a fairing to smooth the air/fuel flow and clamps to restrict fuel injection in critical areas.

The DLO source says there is "potentially more performance to come from the engine... we need to understand what we can do with what we've got". He adds that the development delays have been recovered by accelerating the production programme.

The sources say, the thrust increase was not covered by the contract which only included better life-cycle costs, so no damages will accrue from the lower-than-expected thrust improvement.

Source: Flight International