Enduralock Self-Aligning Nut Plate

Votes: 4
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Enduralock self-aligning nut plates are designed to dramatically reduce the time and cost of installation and maintenance of aerospace access panels.

Nut plates are used throughout aerospace for the attachment of access panels. Rather than having the panel bolts thread into the substructure, nut plates are employed. The nut plate consists of a retained nut in a body that is either welded or bonded to the inner surface of the substructure. Current nut plates offer translation of the nut element in a radial (side to side) direction, but they do not allow for the nut element to tip (to engage an off-axis bolt) or travel in an axial direction. With large aerospace access panels, such as the panel connecting the fuselage to the wing, there could be a few hundred bolts that are retained to the rim of the panel. As current nut plates do not allow for tipping of the nut element, the installment of the access panel requires the mechanics to align all of the bolts in a perpendicular fashion to the nut plates to engage the nut element of the nut plates. This dramatically increases the time and cost of installation of the access panel.

The Enduralock self-aligning nut plate has a nut element that is axially spring-loaded, which allows it to tip to engage an off-axis bolt. As the bolt is threaded, it self-aligns. This dramatically reduces maintenance time for the application of large access panels.

Current access panels employ bolts that need to be retained to the rim of the access panel. These fasteners are typically retained to the panel by a sliding retaining ring on the bolt. The problem is that a sliding retaining ring on the bolt can bind and then break, which can lead to FOD (foreign object debris). The Enduralock self-aligning nut plate bolt dramatically reduces FOD, as the retaining ring is a much more robust fixed position conical retaining ring (split on one side to allow for the installation of the bolt to to the panel). During application of the panel with a fixed retaining ring, the nut element of each nut plate is pushed axially away from the substructure. As each bolt is tightened, the nut element is drawn towards the substructure. The axially spring-loaded nut element allows for each individual bolt to be completely tightened before moving to the next bolt. In removal of the access panel, each nut plate allows for complete loosening of a bolt before moving to the next bolt, as the spring-loaded nut element is pushed axially away from the substructure during the loosening of an individual bolt. Without the axial travel of the retaining ring during the application or removal of the access panel, the retaining ring is much less likely to break to create foreign object debris (FOD).

In summary, the Enduralock self-aligning nut plate reduces the time and cost of access panel installation and maintenance, and it reduces the chance of foreign object debris (FOD).


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  • Name:
    Harold Hess
  • Type of entry:
    Team members:
    Dr. Harold Hess
    Igor Komsitsky
    Zoltan Furu-Szekely
    Armando Perez III
  • Software used for this entry:
  • Patent status: