The decision has been made to progress with the Pegasus engine reassembly which was held up for want of serviceable exhaust valves. A spare set has been sourced and although their use is subject to ongoing deliberations by the many players in the Engineering Authority and its scientific and industry advisors, it was agreed to steal a march and get closer to test flights and potentially a good many display appearances this season. In the worst case, if alternative valves are needed they will take time to source and manufacture, however in the meantime the aircraft will at least be fully assembled which is better for preservation and presentation to the flights visitors. The current advice is that they are fit for purpose having been treated following a treatment with a special dry film graphite lubricant which arrived on site at the beginning of June. The valves work in a pretty hostile environment exposed to heat and the elements, with little lubrication apart from the oil impregnated pad attached to the spring retainer. The intake valves run a bit cooler thanks to the air fuel charge rushing by and are fitted with a valve stem seal on top of the guide. But the exhaust valves run very hot and have a sodium filled stem core to aid cooling and thereby protect the valve. The graphite was applied to the valves which were then baked in an oven to impregnate the stems which aids lubrication between the valve stem and valve guide. The baked lubricant can clearly be seen as a black deposit
The heads and barrels are normally treated as a single component being joined by an interference fit screw thread and the valves are inserted into their guides through the cylinder bore. A shaped wooden pole holds the valves in place and provides a stand to aid assembly of the springs. A simple bent rod secured in the spark plug holes provides a fulcrum for the simple special tool used to compress the three springs and allow the collets to be inserted
Finally, a new oil soaked felt pad is secured in the recess of the spring retainer by a circlip. With the cylinder refitted to the crankcase the rocker and push rod assembly is refitted
fiddly work but the team are well practiced as the pistons continue to be inspected every 15 flying hours.
Throughout last season only 1 piston was found to be degraded and this has now been replaced.
Aside from the engine work the anti-collision PFLARM installation is complete and evidenced by small triangular aerials under the rear fuselage and on top of the upper wing. This should facilitate all round communication with other fitted aircraft to aid detection and avoidance. Oily rag readers may recall a new strut had to be manufactured to support the engine starting crank lug. This has now been fitted and can just be seen where it is attached to the forward fuselage
Sadly the report received on the valves that were being tested, has recommended we do not fit them to the Pegasus engine. Further work is required and a new set will have to be sourced with changes to the valve hardening process required before they will be approved for use. Work is already underway to source new valves but the reality is they will not be produced and cleared into the aircraft in time for the 2017 display season. If we can get the aircraft serviceable this year she would be test flown, a new pilot waiting in the wings converted, with the aim of getting ahead for the 2018 season.
WK608 is running and flying well and had an outing to the Shuttleworth Fly Navy air show.
The Sea Vixen
The unfortunate undercarriage failure and subsequent, controlled belly landing pose significant engineering challenges, which are covered here
The Sea Fury T20
Lt Cdr Chris Gotke is in the process of engine testing the Sea Fury T20 for more news click here