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Aviation History
1989
1989 - 0119.PDF
T-45 performance 'inadequate', says US Navy The US Navy this week begins flight-testing a McDonnell Douglas T-45 Goshawk trainer with an uprated engine, after finding that the aircraft is underpowered. The existing 5,4501b-thrust engine has been re-rated to 5,7001b thrust for the tests, which follow a Navy test report that "The T-45A in its current configuration does not have the potential to be operationally effective in the carrier training environment". The Navy's complaints have arisen from flight testing since last April of two development aircraft at Patuxent River Naval Test Centre, and principally concern performance and stall characteristics. With its speci fied 5,4501b-thrust Rolls-Royce F405-RR-400 engine, the aircraft has proven inadequately powered to achieve a go-around if it fails to engage an arrester wire on the carrier. Rolls-Royce tells Flight that it has always been "concerned" about the McDonnell Douglas/ Navv choice of a derated model of the 5,7001b-thrust Adour 861 (which powers the export version of the British Aerospace Hawk, from which the T-45A is derived). "They asked' us to derate the engine to the lower level, and yet the T-45A weighs 1,3001b more than the standard Hawk aircraft. "As recently as December 1988," says Rolls-Royce, "the Navy stated that the F405 meets all 'specification requirements o^uJUM^iBuy a?87 Two McDonnell Douglas/British Aerospace T-45 Goshawks are now flying placed on it by McDonnell Douglas. The : F405 engine's thrust was derated from that of the Adour 861 series at the customer's instruction. The full thrust is available should the customer desire." Perhaps fortunately for the Navy, re-rating the F405 to the Adour 861 thrust level is simply a matter of adjusting the fuel control unit and turbine gas temperature controllers. This is work that can be done within an hour—with an insignificant effect on fuel burn. So why did the Navy decide on the low- thrust engine? "To reduce life- cycle costs," says McDonnell Douglas. A further T-45A performance problem has already been fixed. Navy test pilots had complained that the engine spooled up too slowly during approach to a carrier (the Patuxent River test centre has a dummy carrier deck painted on the runway). It turned out that the pilots were ignoring Rolls-Royce recom mendations for a 70 per cent high-pressure spool idle speed. "They were pulling the throttle back to 55 per cent," says Rolls- Royce. The throttles of the flight-test aircraft have now been fitted with a detent to prevent throttle retraction below 70 per cent. T-45A stall characteristics are "inconsistent", according to McDonnell Douglas, "and therefore not very good for students". Various devices, including wing fences, are being tried on one of the two aircraft now flying at Patuxent River. "It's hard to test the fixes in a windtunnel—it's a matter of playing with devices on the flight-test aircraft," says McDonnell Douglas. Another aerodynamic prob lem concerns the T-45A's airbrakes, which cause the air craft to pitch up when deployed, and to pitch down when retracted. British Aerospace is understood to be working on a solution. A hydraulic problem which caused the airbrakes to retract under aerodynamic pres sure has been fixed. "The T-45 programme is in the full-scale development phase and has reached an early stage of a carrier operation assessment by the US Navy," notes British Aerospace. "Problems and queries are expected to arise at this time, to ensure that the operational needs are satisfied, particularly in relation to student pilot training. "Current concentration on the stall characteristics requires flight testing of wing dressings, such as fence location, rather than windtunnel activity. There is a trim change with speed- brake extension, and BAe has been asked to investigate a change to the hydraulically operated deployment system," concludes BAe. The Navy plans to buy 302 T-45s by 1997 as part of a total training package supplied by McDonnell Douglas. Aircraft production at McDonnell Douglas Long Beach plant began in December. Ten-year US strategic weapons plan proposed The influential chairman of the US House of Representatives' Armed Services Committee has proposed breaking strategic weapons spending out of the overall defence budget and putting it on a ten-year planning timetable. This "magic ingredient of time", he says, would give budget-makers a chance to avoid conflicts in! priorities when funding pressures coincide. Les Aspin, a Democrat, calls for strategic programmes to be funded at a flat level over the period, perhaps based on the $31-billion allotted to these systems in the current FY1990 defence budget, and adjusted for inflation. Aspin is concerned that the USA has been spending money on its strategic forces in a lopsided manner during the Reagan Administration. "In all, we have spent $215 billion 'to develop, build, and operate major strategic weapons systems during the Reagan years. We spent a quarter on sea- based missiles and submarines. We spent a whopping 60 per cent on our bomber fleet, first to build the B-l, then begin the B-2, but we spent only 16 per cent of the money on land- based missiles," he says. "We spent more than 80 per cent of the money on the two legs of the triad that, while needing upgrading, were not in danger," Aspin argues. The "window of vulnerability" affecting land-based missiles which President Reagan campaigned on in 1980 is. "still wide open," claims Aspin. Recounting the "sorry tale" of efforts to fix the land-based missile dilemma, Aspin says that the current stalemate in Congress between the MX and Midgetman ballistic missiles has been caused by passing the buck from year to year. The point where the issue must be solved has now been reached. "If we look out one or two years ahead, there is no solu tion. But look out aN little further, and the basis for a compromise appears. We are going to have to create A ne.w consensus on strategic forces over the next decade." Aspin proposes puttin'g money for SDl, submarines, B-52s, B-1BS, B-2s, Trident missiles, MX, cruise missiles, and mobile missiles into the pot. "Then, with a ten-year time horizon, rational decisions can be made on the timing of systems, and this is where we can tackle their affordability." If this were to happen, Aspin believes the following steps could be taken: • Give priority to the fielding of Midgetman, a "truly survivable land-based missile", and plan for its deployment in 1995; • Maintain current spending plans for Trident missiles and submarines, at the rate of two boats a year; D Slow down procurement of the B-2 bomber by two years; D Hold SDI funding at its current level of $4 billion through 1996; • Keep Rail-MX funding low until 1993, then boost it towards first production in 1996. FLIGHT INTERNATIONAL, 21 January 1989 5
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