ChipmunkEngineeringNewsOily RagSea VixenSwordfishWasp

‘Oily Rag’ from the Heritage Hangar

By February 19, 2020 March 5th, 2020 No Comments

The Westland Wasp XT420 is currently undergoing routine winter maintenance at North Weald and will be back within a few weeks to continue pilot training ready for the 2020 display season.

The Chipmunk WK608 was recently fitted with a reconditioned engine and is currently inhibited as evidenced by the flags and lack of spark plugs. As soon as the transition to the civil register has been completed, she will be ground run and test flown to return to full airworthiness.

Swordfish W5856 is nearing the end of her winter maintenance programme and is currently in the old hangar for the x-ray inspection of the tail fin. The LS326 is waiting patiently for her engine which is currently being rebuilt by deltair.

The Sea Fury T20 is at North Weald and under routine winter maintenance, the engineers found a leak in the oil tank and repairs are underway ready for a busy 2020 season.

The Sea Vixen XP924 repair scheme for the fuselage damage has been delivered by Acro Aeronautical Services Ltd. The drawings and specification are comprehensive. The engineers have busy translating the repair scheme into 3 work packages to deal with damage in the forward, mid and tail sections of the fuselage.  The first step would be to manufacture frame repair test pieces to prove the in-house fabrication capabilities. These sections are relatively complicated and would require sheet metal working skills rarely used in modern aviation but commonplace to many artificers and civil technicians trained in the 1960/70s.  These flanged curved frame sections would be shaped around timber formers using aluminium alloy sheet cut to shape. The alloy would be annealed to make it softer and clamped between the formers with the flange material protruding so that it may be carefully bent with special shaped mallets to form the flanges.  This is skilled work that would require the blows to be delivered precisely to stretch or compress the flange metal depending on whether they are on an inside or outside radius. During this bending process the metal needs to be re-annealed regularly to avoid excessive stress and cracks from work hardening. The flanges are then cut down to size, the edges draw filed to remove potential stress points from the cutting and then a final heat treatment to relieve any internal stresses.  If these capabilities could be proven the team would cut back the damaged frames to clean straight edges. They would then make the frame repair sections using hardwood formers and marry them to the cut frames with riveted reinforcing doublers.  Then newly manufactured alloy stringers would be fitted between the frames and finally the new outer skins.  This would be an exacting and time consuming process and there are some more complicated areas, for instance where pulleys for the flap control mechanism are mounted on machined alloy “packing blocks” details of which are included in the repair scheme in the form of original De Havilland blueprints.

There is also some progress with the Palouste starter pod which is designed to be mounted on a store pylon. This gives the Sea Vixen a self-start capability which is useful when visiting airfields that do not have compatible starting rigs.  The team have replaced the torch ignitor and have managed to get the primary fuel injectors to run up the gas turbine to 15,000 RPM.  However, there is a problem with the main injector system which needs to be rectified to get the Palouste to spin up to the normal operating range (24 to 35K RPM) and deliver the bleed off air to start an Avon main engine.

The Sea Vixen has been raised on jacks and is connected to a hydraulic rig  so that supporters that visited the recent Navy Wings at work event were able to witness the functioning of the undercarriage and the wing fold systems.  This is a significant spectacle and capable of transporting minds back to an era of powerful fixed wing air carrier borne operations. The ejector seat has been removed and is on display. This rear view of the seat in the foreground shows the telescopic tube or gun which when filled with gas from the explosive cartridges, propels the seat and pilot out of the aircraft.

The wonderful Sea Vixen engineers have done a fantastic job keeping her in a state of suspended maintenance and doing what repairs they can. We have now reached the stage where we will need to spend capital funds on the aircraft. This is a major decision for the charity and given that we have not yet had a ‘White Knight’ donor to underwrite the plan of a full back to flight restoration. Read more here