Making Nacelle Lip Skins
Work done using the TM Tech Air Power Hammer

Home > Gallery of Metalwork > Aircraft Metal Work > Making Nacelle Lip Skins for the Hawker-Beech XP400, Work done using the TM Tech Air Power Hammer

Kent was hired by Siera Industries in 2011 to make a set of 6 prototype nacelle lip skins for the Hawker Beech XP 400, a new business jet. Since even protoype tooling for a job like this is nearly $80,000 and then making just six lip skins to meet prototype requirements would add to that tooling cost, it was decided to hire a craftsman to make them by hand. Kent chose a combination of two methods, “flow forming” to stretch the inner radius and using his TM Technologies Air Power Hammer to shrink and planish the outer profile.

This photo shows the flow forming tooling in place with the blank aluminum skin clamped above it. Material is 2024 T-0 .063, cold worked and then heat treated to T-3.
Two men are flow forming the inside of the ring, using 4X rivet guns. This is a stretching operation.
The outer edge will be shrunk, and it has been ruffled in measured humps for the shrinking operation, next.
The Air Power Hammer is set up with the Soft Metal Shrinking Dies, developed by TM Technologies. This is a radically different form of shrinking, and is trademarked by TM Technologies.
The Hammer shrinks very efficiently, with 50% less fatigue than any other current shrinking technology, by Pullmax thumbnail dies, Eckold, ERCO, YNE, or Marchant. Since Kent has all of these other machines in his shop, he uses them for comparison and has measured the results carefully.
90% of the shrinking was accomplished with the TM Air Power Hammer, and 10% with the ERCO extended jaws in the HDAS4, sold by TM Technologies
Since this is aerospace work, there are many specifications to be met: thickness, contour, surface finish, profile, flatness, and hardness. The profile templates are waterjet cut and the lip skins must match within .020”
The areas that must conform are laid out by degrees on the circle.
My confirmations were 0-0” for over half of each gauge point, and were .012” out at the worst. All corrective work was done after heat treat, since distortion can add a little bit of waviness and departure from contour and fit.
Flatness was held to spec at .050” and thickness was easy because of shrinking – .071” on the outer edge and .059” on the inner. When I called the inspector to get the final results, she told me, “You do beautiful metal work, Mr. White.” Hardness was to spec, and contour and surface was to spec, measured by laser.
Final photo shows the XP400 in flight, with one polished ring showing around the nacelle intake. It is very uncommon, from what has since been heard from the industry engineers, for a craftsman to make these by hand. There is no way any other shrinking method could have accomplished this, as Kent tested all other methods and was met with repeated fatigue failure long before contour was achieved.