28.06.2013

Propeller overhaul: Experience second to none

He is 96 years old, and the Super Star propellers could not be in better hands than his: Chet Heth has more decades of experience than anyone else in the overhaul of Hamilton Standard propellers, which are the ones fitted on the Deutsche Lufthansa Berlin-Stiftung (DLBS)'s Lockheed L-1649A. For Chet Heth was himself involved in the production of the Super Star propellers over half a century ago.

The Lockheed L-1649A Super Star is an unusual aircraft in many respects, and when it was being developed in the 1950s the engineers pushed forward the boundaries of aircraft construction to territory previously unknown. The same applies to the design and construction of the aircraft's Hamilton Standard propellers. Their blades are the longest propellers ever to have been used in civil aviation.

When the Lockheed Super Star team approached United Technologies Corporation (today the parent company of Hamilton Standard) with a request for help with the overhaul of a total of six propeller sets, it referred the team to Chet Heth. The 96 year old propeller expert worked for Hamilton Standard for over half a century and was involved in propeller production for the L-1649A back in the 1950s. No one else has such an in-depth technical knowledge of historic Hamilton Standard propellers. Through his company, Los Angeles based Conversion Technology, Chet Heth was engaged to overhaul the Super Star propeller sets in 2008. As well as the blades, there are the system components, such as the complex synchrophaser system, which synchronizes the position of the propellers in-flight and thus enhances passenger comfort.

Despite his age, Chet Heth is still very active and is closely involved in the detailed work. The actual propeller overhauls are being carried out at Hope Aero in Toronto, Canada. Here the six propeller assemblies, including two spare sets of propellers, are being overhauled by local specialists. Each set consists of three individual blades. The extensive work package starts with a visual incoming inspection, following which NDT and ultraviolet checks are performed to identify any cracks and defects in the material. Subsequent stages include surface checks and contour mapping of the individual propeller blades, remedial work on the blades for the alignment of similar contours and the removal of damage and defects. The propeller blades are now grouped by size, weight and contour for later dynamic balancing. Before the propellers are painted, assembled and balanced in the static state, their blade attachment rings (barrels) together with toothed gears and hydraulic control units have to be overhauled.

The first propeller assembly was finished at Hope Aero in April 2013 after about three months' work. It is expected that the last set of propellers will be completed this November. Following successful final inspection in Toronto, the assemblies will first have to be dismantled due to their size before they can be transported to Auburn. Shortly before installation in the Super Star engines they will be reassembled for the last time. But that will not be the end of it. In a final step the propeller sets have to be dynamically balanced on the aircraft. Only then will it be possible to say that the complex propeller overhaul is complete.