Corrosion Repair.
There is exfoliation corrosion in several areas of the upper spar caps of both mainplanes. The section shown above is on the outer Right mainplane main spar just outboard of the transport joint rib. The corrosion will need to be removed, the amount of material that has been removed will be assessed and a repair plate fitted. Other areas of the spar caps have previously been repaired as this is a well-known problem with Aluminium Alloy forgings. The repair will need to be referred to Boeing who now holds the historical rights to the Douglas design office. We hold historical reference documents which appear to prohibit repairs to the spar caps inboard of the engine nacelles, further research indicates that it is splice repairs which are not allowed rather than corrosion removal. We have entered into a discussion with Cranfield Aerospace who has agreed in concept there will be no problem with the repairs.
Each repair is estimated to take a minimum of two weeks to accomplish, there are six areas of corrosion. A limited inspection of the spar webs has been carried out in the centre section and inside the inboard engine nacelles. No obvious defects were found and the spar webs and booms appear to be sound. The skins are secured to the structure using Magnesium Alloy rivets. Over long periods the structure of the rivet is weakened and the rivet will fail as has happened in the above picture in the area of the right-wing outer mainplane transport joint. The repair for this will be to remove the failed rivets and replace with a modern alternative. There is also evidence of corroded structure below the skin (as evidenced by the skin swelling up) which will require further inspection and investigation. A conservative estimate would be that the repairs would take between eight and twelve weeks to complete.
Engines.
Pratt and Whitney have adopted a “hands-off” approach to the support of reciprocating radial engines. We have talked to Anderson Aeromotive who overhaul these engines in the United States. They have set the time between overhaul at 1500 hours. The engine condition is monitored through oil consumption, once oil consumption rises above a maximum amount the engine is in need of attention. A lot of investigation and rectification can be carried out “on the wing” and the intention is to carry on this philosophy during operations. Because these engines have not flown in more than twelve years they will need to be dismantled and a thorough inspection carried out by an authorized repair organization.
Historically the engines have run very well with anti-deterioration runs being carried out until recently. In March 1976 FAA STC was raised to replace R-2000-4 with R-2000-6 engines this modification has been carried out in the number 2 position and it is possible to modify the remaining engines to this standard. There is a spare engine in the fuselage which may be used as a source of spares or possibly overhauled and returned to service. We have purchased an additional low time (50 hrs since overhaul) engine. A plan for the examination of the four installed engines and the spare engine has been prepared by Weald Aviation Ltd.
Propellers.
There are detailed log books for the props until June 2002 when all four props were removed for work related to A.D. 81-13-06 in Canada, this work needs to be satisfied at an interval not exceeding 18 months. It has been recommended that the props are removed and overhauled before the engines are started. Weald Aviation Ltd. have prepared a plan for the overhaul and satisfaction of A.D. 81-13-06 of all four propellers in their on-site facility.
Avionics.
There is a full set of VFR avionics fitted but they will need to be updated to a modern standard. An agreement is in place for the overhaul and upgrade of the historic avionics and installation of a modern avionics fit from a private sponsor.
Flying Control Surfaces.
There is a full set of VFR avionics fitted but they will need to be updated to a modern standard. An agreement is in place for the overhaul and upgrade of the historic avionics and installation of a modern avionics fit from a private sponsor.
Hydraulic Components & Landing Gear.
As with the engines the components of the hydraulic system and the landing gear will have to be overhauled and certified by a recognized repair organisation. Once again we have several offers of support from companies in the U.K. with F.A.A. accreditation (one of which has links to the Berlin airlift) who are capable of carrying out this work.
