Aircraft Vibration, NVH & Shock Isolation

Three steps, in order. First, locate the disturbance band: the platform's propeller or rotor orders and the equipment's vibration categories name it. Second, choose the softness and thickness that put the loaded natural frequency well below that band; the ladder tool on this page walks the logic qualitatively.

Third, load-match: every grade has a working stress range on its TDS (ASTM D3574 for the PORON ladder), and pad area is the tuning variable, small footprints for light boxes, spread footprints for heavy ones. Send the mounted mass with the drawing and the grade-plus-footprint answer comes back matched. [4]

Resonance. A mount only isolates above the crossover ratio; below it, it transmits, and at its own natural frequency it amplifies, sometimes dramatically. A pad chosen by feel commonly lands its natural frequency inside the platform's strong band and turns the mount into a multiplier, which is why a wrong mount is worse than no mount.

The fix is the ladder discipline: name the band, then drive the mounted frequency well below it with softness, thickness, and footprint, and verify the loaded deflection on a first article. If the input is broadband acoustic, no mount frequency works and the job changes to damping and mass barriers.

Three mechanisms for three problems. Isolation separates a mass from a vibrating base with a soft spring and works when the disturbance frequency is well above the mounted natural frequency: the pad-under-the-box physics. Damping bleeds energy out of a structure that is resonating: a lossy layer bonded to a ringing panel, effective at the panel's own modes. Mass barriers block airborne sound transmission with limp weight: the A2 silicone sheets in a sidewall stack.

Diagnose which one your problem is before buying material, because each mechanism's material does nothing for the other two jobs. [8]

They are equipment-level test vocabularies, not material ratings: MIL-STD-810 methods and DO-160 section categories define the vibration and shock environments the equipment maker qualifies the box against. For the converter they are the most useful documents in the conversation, because the test curves name the frequency bands and levels the mount must beat. No pad is "MIL-STD-810 rated"; a mounted system passes its category with the pad's help.

Bring the category or curve to the drawing review and the band-ladder conversation becomes specific instead of qualitative. [1]

Find the dry contacts and keep them loaded. BSR noise comes from micro-motion at panel joints, bin interfaces, and trim edges; the cure is a thin, soft, low-set pad at each contact that converts the motion to silent shear. The converting format is most of the battle: exact footprints to the trim drawing, kiss-cut on liner for one-step installation, PSA matched to the substrate pair, and zone-kitted sets so each panel run pulls one part number.

Interior placement adds the fire context: the FAR-referenced ENSOLITE MLC Black grade, kSil KSV silicone sponge and V-0 PORON entries keep the fix documented. [9]

Move up the temperature ladder: silicone foam first. The HT-800 series keeps its spring across a wide published window and brings flame and smoke data per its TDS; SCE neoprene covers the oil-misted, abuse-heavy middle below silicone temperatures; and SAE pressed felt remains the contamination-tolerant veteran with a published −62 to +93 °C class. Urethane stays in the benign bays where its set performance shines.

If the location is genuinely fluid-wetted rather than misted, the selection leaves this page for the fluid-zone logic. Measured local temperature beats bay averages on every drawing. [11]

The energy-absorbing urethanes: slow-rebound PORON (4790-92 class) and the ShockSeal grades. Shock is a single large impulse, and the pad's job is to spread it over time and stroke without bottoming, then recover; slow-rebound chemistry does exactly that, with impact data per grade on the TDS. The design discipline is travel: enough thickness and the right firmness that the event uses most of the stroke.

Thin ShockPad-class films protect displays and boards inside equipment, and thick rebonded pads take transport and base duty. Equipment shock categories (DO-160 section 7, MIL-STD-810 methods) define the event the design must eat. [10]

Set is stiffness drift with a schedule. A permanently compressed foam slowly keeps some of that compression; as the pad flattens, its working deflection shrinks, the mounted natural frequency climbs, and the mount migrates back toward the disturbance band, which reads as a gradual rise in vibration squawks years after a clean install.

The drivers are material class (low-set urethanes and silicones versus commodity foams), over-compression past the working range, and temperature above the rated window. Spec from the published set data per ASTM D395 / D3574 at the service temperature, and budget deflection margin so year ten still sits below the band. [7]

Adjacent, with a hard boundary. SAE AS8049 is the performance standard vocabulary for aircraft seats, and seat systems (including their energy-absorbing cushion builds) are certified by the seat maker under it; H-O does not supply certified seat systems or claim any part of that approval.

What we convert, as a materials supplier, are the cushioning, BSR, and comfort-adjacent foam details around interiors and monuments, reviewed against the program's flow-downs, with FAR-referenced grades where interior placement requires documentation. If your part is inside a certified seat build, your seat maker leads and we support their material spec. [3]

Inside the cabin and cabin-adjacent bays, expect the question and carry the answer. Interior-materials context (the FAR 25.853 vocabulary) reaches pads, liners, and BSR details, and the program will ask what data stands behind each one. The families on this page answer on their TDS: the PORON V-0 grade, the FAR-referenced ENSOLITE MLC Black entry, the kSil KSV sponge (FAR 25 Appendix F, ABD0031, smoke and toxicity data), and the silicone foams' flame and smoke data.

Which clause applies to which part is the program's call, and the FST materials page maps that logic; the converter's job is supplying grades whose paperwork is ready when the question lands. [9]

Yes, and this application is where kitting pays fastest, because the parts are numerous, small, and station-specific. H-O and kiss-cuts the pad set, bags it by installation zone or work card, labels to your numbering, and ships one part number per kit with lot-coded TDS records per component, through our assembly & kitting capability. Interiors lines stop losing minutes to pad-hunting, MRO refresh kits match the shop visit instead of the warehouse, and material substitution stops happening at the bench because the right grade is the one in the bag.

H-O is a die-cutter and converter, so every pad, liner, and barrier stack is made-to-order to your drawing, including samples. We maintain working material relationships with the urethane, vinyl nitrile, silicone, and felt makers and keep common stocks on hand for faster turnaround.

Samples typically ship in 3–5 business days for common configurations on materials we keep on hand. Standard production runs ship about 2 weeks after drawing approval, including kiss-cut PSA-backed sets and zone kits. Expedited service is available when line or retrofit dates are hard. MOQ varies by material and part; prototype quantities through production runs are equally accepted. Send the drawing and quantity through the form below for a specific commitment with your quote.