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Aviation History
1990
1990 - 2686.PDF
though the wooden blades used by the Spit fires and Hurricanes are made by Hoffmann in Germany for Dowty. Some components are just not available at all, and there the flight has to adapt. "Getting hold of 12-volt instruments and electrical equipment is now difficult," says Sears, so the flight is slowly converting its fighters to 24V - the Lancaster was -24V from new. The "new" 24V instruments are visually almost identi cal to the 12V equipment so, Sears says: "Cosmeti cally, the planes look the same -they're just a bit more modern underneath". Some essential 12V equipment -such as fuel gauge sender units -has to be retained, and that is given stepped-down voltage. While the Spitfires have been rewired and Griffon 58 joins a Spitfire... converted, the Hurricanes are still running on 12V for the meantime so the redundant Spitfire equipment is being used as back-up until the Hurricanes can be converted too. Tooling up to build new parts can be extremely expensive, and might only be practical if several different groups club together to make manufacture economically viable for both the manufacturer and the customer. That is hap pening at the moment, in a venture to make new brake linings. New wheels have been made for the Spitfires (the magnesium-alloy cast ings were done in Bei jing!). There is another project under way which may lead to Mer lin camshafts -now ex tremely rare -being made again. The BBMF commissioned new brake drums for the early Spitfires, and was Spitfires will average 42h each during this display season able to supply them to others. Where new parts do have to be made, the flight still refers back, just as with a modern aircraft, to the original design authority - in this case British Aerospace. For instance, when the Spitfires were rewired and con verted to 24V, it was all done to modern specifications and drawings from BAe. A much more complex situation arose when supplies of 60-series Rolls-Royce (R-R) Griffon engines started to dry up, threatening the continued use of the Mk. XIX Spitfires. Because 8 Sqn's Avro Shackle- tons are still in service, there are much better supplies of the Griffon 58 available, and a swap was contemplated. Unfortu nately, the 58 was* designed for a contra- rotating propeller, and its supercharger casing is 18mm wider than that on the 61, so a 58 will not even fit inside the Spitfire's frame. Rolls-Royce at East Kilbride has engineered a conversion, however, and Grif- Lancaster flies most hours on the Flight, and will need re-sparring soon •I fon 58s now keep R-R's own Spitfire and the BBMF trio flying. Some other major spares will be needed in the mid dle-term future, perhaps the most critical being new three-bladed propellers for the Hurricanes. More in triguing is the re-sparring of the Lancaster. On current life and usage, the Lancaster would need its mainplane rear lower, and fuselage rear upper and lower spars re placed by 1998-2000. This re-sparring is driven largely by experience with the sur viving Shackletons and by the fatigue meter which is fitted to the Lancaster. "The Lancaster is very similar to the Shackleton both in construction and in the manner in which it is flown," says Sears, "so the engineering authority on Shacks advises us when critical items arise." That Shackleton ...and needs a different prop experience will probably lead to the Lan caster re-sparring being done early. The Shackletons have all been re-sparred in the last couple of years, and Sears is keen to profit not only from the spares made then ("I've got the spare spar billets from the Shackleton programme already...") but also from the expertise acquired in doing the job. He fears that such experience will be lost again from the RAF if the flight waits too long to do its re-sparring, so the cur rent intention is to do the job in the winter of 1994/ 1995. Once the spars are done, the Lancaster should enjoy another 3,500ft flying be fore the next critical item arises, if current operating procedures and usage con tinue. The flight is a little less well-placed in fatigue experience on the Spitfires and Hurricanes, because there is no current service 176 FLIGHT INTERNATIONAL 5-11 September 1990
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