The two-year project to carry out a complicated repair to the ‘Frame 5’ bulkhead of BBMF Spitfire PRMk XIX PS915 came to a successful conclusion in February and the aircraft can now be rebuilt to flying condition.
PS915 has been grounded since July 2018 when cracks were found in the ancillary gearbox mounting bracket on the front of its ‘Frame 5’, the bulkhead behind the engine. In 2021 the BBMF engineers traced the cause of the cracking in the bracket to it being misaligned on the ‘Frame 5’; this was verified by Retro Track & Air using a specially designed alignment tool. At first it seemed that the only solution was to have a completely new ‘Frame 5’ manufactured, and for the aircraft to be taken by road to a contractor for the frame to be replaced; a major, expensive and lengthy undertaking.
In early 2022 the BBMF explored other options for returning PS915 to airworthy condition and involved the specialists of 71 (Inspection and Repair) Squadron to carry out a repair to PS915’s ‘Frame 5’ in the BBMF hangar, supported by the BBMF Project Team (PT) EA4 (Structures team). The project was complicated by a shortage of available drawings of the Spitfire PR Mk XIX ‘Frame 5’ and the limited utility of those that did exist. Some extrapolation was necessary, working from known points on the drawings, to assess precisely where the holes, including those for mounting the ancillary gearbox bracket, were situated on the face of the ‘Frame 5’ bulkhead.
A work package was produced by 71 Squadron and, as no ‘Frame 5’ bulkhead spare part existed and because the drawings were limited, it became a “replacement by development” project. The work package was split into two phases: a strip and inspection phase and a manufacturing and replacement phase.
In June 2022 a team of technicians from 71(IR) Squadron, led by Sergeant Matt Walker, with Corporal Tom Harris-Jones and AS(1)Ts Sam Fennell and Billy Hull, began stripping and inspecting the affected ‘Frame 5’ on Spitfire PS915 in the BBMF hangar. Meanwhile, the BBMF PT contracted Airframe Assemblies Ltd on the Isle of Wight to manufacture new blank-form steel sheets, shaped and sized for the centre and top sections of a new ‘Frame 5’. These were delivered to the BBMF in late July. In addition, the RAF Coningsby Station Workshops manufactured some parts for the repair, such as stiffeners and mounting brackets.
Cranfield Aerospace Solutions Ltd (CAeS) was contracted by the BBMF PT to provide the necessary Design Organisation approval of the repair, along with a Certificate of Design and supporting drawings. (CAeS is the MOD Design Approved Organization Scheme defence contractor that has acted as Design Advisor and Independent Technical Evaluator for the BBMF fighters since 1985.) Over the course of the project, 76 complex technical queries were raised by the 71 Squadron team and posed to the PT’s EA4 team. Many of these questions were related to the ‘as fitted’ condition not being representative of the initial drawing standard or due to ambiguities in the drawing set. In each case, the PT, in conjunction with the 71 Squadron team, devised a solution for consideration by CAeS. In addition, as questions arose over such issues as material selection or alternative rivets these were put to CAeS by the PT EA lead. Some answers were provided by CAeS during the process and some were retrospective, allowing work on the aircraft to continue uninterrupted. All technical queries required subsequent approval by a PT Letter of Airworthiness Authority holder.
By October 2023 PS915’s new ‘Frame 5’ was finished and was sent to Airframe Assemblies for cadmium plating and painting. It was returned to Coningsby in early 2024 and was then assembled and fitted to the aircraft for the final time, so that the Spitfire’s Rolls-Royce Griffon engine could be refitted and a 71 Squadron Technical Inspector could conduct a detailed review of the work carried out by the 71 Squadron team. Finally, the complete repair technical package was sent to Group Captain Andy March, the BBMF Type Airworthiness Authority, for his review and approval. This complicated airframe repair project for Spitfire PS915’s ‘Frame 5’ involved multiple organisations and companies, including: 71(IR) Squadron, the BBMF engineers, the BBMF Project Team, Paul Blackah and Elev8 Aviation, Airframe Assemblies Ltd, Cranfield Aerospace Solutions Ltd, Retro Track and Air UK Ltd and RAF Coningsby Station Workshops.
Spitfire PS915 can now be rebuilt by the BBMF engineers who will also carry out a penalty Primary Star maintenance programme on the Spitfire. It is hoped PS915 will be seen and heard in the skies again this year for the first time in over six years.
