Chemetall Applies Space Age Technology for a Venerable Old Girl
Chemetall, the surface treatment chemical specialist, which supplies the internationally renowned ARDROX technology, was invited to assist in the restoration of an Avro Tutor from the famous Shuttleworth Collection.
The Shuttleworth Collection is an assemblage of veteran aircraft, which has grown out of the private collection originally started by Richard Shuttleworth. One thing that makes this group of aircraft special is that they are maintained by five permanent engineers ably assisted by a band of dedicated volunteer enthusiasts to airworthiness standards. So once the dark days of winter have passed by, these glories of a bygone age take to the skies of Bedfordshire.
To ensure that each aircraft is airworthy it has to pass strict criteria. This is done by making sure that each plane is integrally sound. It is also necessary to combat the ravages of old age so the planes are periodically stripped, inspected and reassembled. Once the 2002 flying season was over the Avro Tutor was scheduled to undergo a deep strip and inspection programme. It was during this inspection that an internal examination of the spar booms revealed what first appeared to be severe surface corrosion (rust). The aircraft was wheeled into the workshop where the wings were totally disassembled for a more detailed look-see.
Trevor Wright, Chemetall Aerospace Technologies UK Business Development Consultant, became involved. Trevor is an aircraft enthusiast and is able to combine his love of aircraft with his job as he works for Chemetall PLC, a company, which is a major supplier to both the civil and military aircraft industry. Part of the Chemetall product portfolio includes products specifically designed for the maintenance and overhaul of aeroplanes. Most of these products have approvals from the original aircraft manufacturers.
It was agreed to use the Chemetall products on the corroded wing spar booms, however as the spar booms are sixteen feet long and access is restricted to a 4.7mm hole, a diagnostic camera was inserted into the spar to determine the position and extent of the corrosion. Then the fun began! ARDROX 17, an acid scale and rust remover, was applied hot to the inside of the spar via a funnel and plastic tube. It was then allowed to drain out. The process was repeated but this time both ends of the spar were sealed and the wing spar was rotated 360 degrees about its longitudinal axis to ensure complete coverage. Once this had been done the liquid was allowed to flow out of the tube and it was noted that this liquid now contained a considerable amount of red rust deposits. A similar procedure was followed with the cold application of ARDROX 185L, an alkaline deruster, which neutralised any remaining acidic solution inside the hollow spar boom.
At this stage the wing spar required thorough rinsing, which was achieved by taking the spar outside and flushing it through using a high tech hosepipe.
The part was taken back to the workshop where it was dried out thoroughly prior to the application of the Corrosion Inhibiting Compound (CIC). Once the inside of the wing spar boom was dry ARDROX-DINITROL AV 8, a corrosion inhibiting compound, was applied in a similar way to the previous products. This will protect the internal surfaces of the wing spar boom and also offer greater integrity to those previously corroded areas. The CIC used in this project is also available in aerosol form to owner pilots and to smaller workshops.
This Avro Tutor was originally built in 1933 and after its refit, it should be as good as or, perhaps, even better than new. Unfortunately because of the rectification man-hours involved, this plane will not be ready to fly this year, however, by 2004 it should once again be ready for takeoff. It was originally painted in a yellow based livery however it will be given a new colour scheme as part of the refit. The whole restoration project includes not only inspecting the engine but also rebuilding and recovering the airframe skeleton. It is a very time consuming operation, and with each stage in the process meticulous care is taken, however, it is worthwhile in the end.
For more information about the Shuttleworth Collection, please visit their website at www.shuttleworth.org. To find out more about Chemetall and their products for aerospace, please visit their website at www.aerospace.chemetall.com.
Contact: Christina Zabinski
Phone: +44 1908 361 885
Further Contact: Guido Kruppa
Phone: +49 69 7165 2030