Equipment failures on a military fighter jet can be catastrophic. So, when the seal for a crucial pod mounted against the outside of a jet’s fuselage kept leaking and tearing, it not only compromised the jet’s electromagnetic shielding but also put the vital equipment within the pod at risk of damage from air pressure and physical debris. Laird leveraged its testing and modeling capabilities, detailed materials database, and design engineering ingenuity to create a gasket that could retain its integrity and seal the pod under the rigors of flight. Read how this novel seal solution allowed the manufacturer to protect this crucial pod from air pressure and debris, while also maintaining consistent and reliable electromagnetic shielding.

Read below:

Shielding the warfighter with a novel seal solution

BACKGROUND

Equipment failures on a military fighter jet can be catastrophic. Something as seemingly small as a frayed gasket can easily lead to something as significant as critical equipment failure or even enemy detection. So, when the seal for a crucial pod mounted against the outside of a jet’s fuselage kept leaking and tearing, it not only compromised the jet’s electromagnetic shielding but also put the vital equipment within the pod at risk of damage from air pressure and physical debris. The manufacturer needed a solution that would protect the valuable equipment and servicemembers aboard the jet. It worked with Laird to diagnose the problem and devise a novel way to address this complex issue and seal the pod securely.

CASEBOOK SITUATION

The seal for this large pod presented a unique set of challenges for Laird’s design engineers. For one, the conductive gasket needed to fill a large gap. It also needed to be compressible enough to allow the pod to close fully. In other words, the motor that closed the pod had to be able to overcome the counteracting force from the seal. Most critically, there was a large amount of internal pressure trying to escape the pod and a similarly large amount of external pressure trying to get in. This differential pressure changed constantly during high-speed maneuvers at varying altitudes, pushing and pulling the gasket violently in different directions. The manufacturer needed the gasket to seal reliably from the inside and the outside in these fast-changing, high-stakes situations.

RESOLUTION

Laird tackled this collection of challenges using its unmatched testing and modeling capabilities, detailed materials database, and design engineering ingenuity. Laird’s engineers needed to design a cross-sectional shape for the gasket that could retain its integrity and seal the pod under the rigors of flight. Tapping its database of material characteristics and advanced 3D modeling software, Laird performed a series of simulations to assess how various gasket shapes would respond to repeated compression cycles, a wide range of temperatures, and forces from different directions. The Laird team modeled a variety of gasket shapes, but most designs failed when subjected to the intense side pressure that would occur during flight. For instance, simulations showed that side force on this trapezoidal bulb seal would blow it out before it reached its required pressure.

Ultimately, the team found success with a dual-blade seal design, which has what resemble two “arms” and two “legs” and effectively converts pressure on the side of the gasket to increased sealing contact pressure. In other words, force from any direction made the seal more secure.

IMPLEMENTATION

Laird put the gasket through a full qualification program, which included testing to measure the force required to fully compress the gasket at a broad range of temperatures. This video shows the stress and strain on the gasket when it is compressed at -40 degrees Celsius (i.e., cold closure force).