Today's experts keep yesterday's legend airborne
Case Study
Nineteen forties engineering and 2011 welding expertise joined forces at TWI recently, in a combined effort to keep the world's oldest flying jet aircraft in the skies.
A thin sheet stainless steel shroud surrounding the jet pipe of a locally-based North American Aviation F-86A Sabre jet fighter was in need of some specialist and expert attention when it was delivered to TWI. The purpose of the shroud is to deflect any leaking exhaust gases away from the internal structure during the brief period, between start-up, and the engine reaching running temperature, when previously weeping seals around the jet expand and become leakproof.
Although within limits, several small cracks and tears were in need of attention during the Sabre’s annual maintenance if the aircraft was to achieve its Permit to Fly. Because there is no direct civilian equivalent, such historic ex-military aircraft fly under this rigorous permit system rather than the Civil Aviation Authority's certificate of airworthiness.
'It's very tricky to weld materials like this but we're lucky here at Duxford’ Roger King of the Aircraft Restoration Company told Connect. 'TWI's experts are almost on our doorstep. Its arc welding department had exactly the skills we required and offered to help us out.'
Using TIG welding, and an appropriate consumable for the aged material, TWI was able to arrest and repair cracks in the wafer thin material. 'It's not a structural part' clarifies King. 'It is a heat deflector. Had it made a structural contribution a more rigorous and detailed procedure would have been demanded. New parts no longer exist for this aircraft so the only alternative to repair would be to re-manufacture from scratch'.
The cracked state of the shroud has been attributed to strain and thermally related fatigue. During its 64 year life the component would have endured many thousands of heating and cooling cycles. 'The Americans are very good at mass production' says King. 'The part was probably rolled and formed in mass production back in the forties. Nowadays a replacement would have to be hand beaten'.
The Sabre is best known for its service in the Korean War where it was pitted against the Soviet MiG-15.
The Golden Apple Trust, which owns the Sabre
(registered G-SABR), believe it to be the oldest airworthy jet-powered
aircraft in the world: its first flight was in March 1949. Aircraft of
this vintage used largely aluminium at manufacture but some titanium is
known to have been used. The adoption of titanium was in its infancy in
the late forties. As the first swept-wing fighter aircraft the F-86 was a
completely new breed of aircraft: in terms of performance and
technology it was in an entirely different class to any that had gone
before. The Sabre’s structure had to withstand not only the rigors of
high-speed flight, but also extreme temperatures, especially in local
areas surrounding the engine turbine and jet pipe.
Nineteen forties engineering and 2011 welding expertise joined forces at TWI recently, in a combined effort to keep the world's oldest flying jet aircraft in the skies.
A thin sheet stainless steel shroud surrounding the jet pipe of a locally-based North American Aviation F-86A Sabre jet fighter was in need of some specialist and expert attention when it was delivered to TWI. The purpose of the shroud is to deflect any leaking exhaust gases away from the internal structure during the brief period, between start-up, and the engine reaching running temperature, when previously weeping seals around the jet expand and become leakproof.
Although within limits, several small cracks and tears were in need of attention during the Sabre’s annual maintenance if the aircraft was to achieve its Permit to Fly. Because there is no direct civilian equivalent, such historic ex-military aircraft fly under this rigorous permit system rather than the Civil Aviation Authority's certificate of airworthiness.
'It's very tricky to weld materials like this but we're lucky here at Duxford’ Roger King of the Aircraft Restoration Company told Connect. 'TWI's experts are almost on our doorstep. Its arc welding department had exactly the skills we required and offered to help us out.'
Using TIG welding, and an appropriate consumable for the aged material, TWI was able to arrest and repair cracks in the wafer thin material. 'It's not a structural part' clarifies King. 'It is a heat deflector. Had it made a structural contribution a more rigorous and detailed procedure would have been demanded. New parts no longer exist for this aircraft so the only alternative to repair would be to re-manufacture from scratch'.
The cracked state of the shroud has been attributed to strain and thermally related fatigue. During its 64 year life the component would have endured many thousands of heating and cooling cycles. 'The Americans are very good at mass production' says King. 'The part was probably rolled and formed in mass production back in the forties. Nowadays a replacement would have to be hand beaten'.
The Sabre is best known for its service in the Korean War where it was pitted against the Soviet MiG-15.
The Golden Apple Trust, which owns the Sabre (registered G-SABR), believe it to be the oldest airworthy jet-powered aircraft in the world: its first flight was in March 1949. Aircraft of this vintage used largely aluminium at manufacture but some titanium is known to have been used. The adoption of titanium was in its infancy in the late forties. As the first swept-wing fighter aircraft the F-86 was a completely new breed of aircraft: in terms of performance and technology it was in an entirely different class to any that had gone before. The Sabre’s structure had to withstand not only the rigors of high-speed flight, but also extreme temperatures, especially in local areas surrounding the engine turbine and jet pipe.
