Aircraft seat cushion guide
Aircraft seats use fire-retardant open-cell polyurethane foam, and on transport-category aircraft that foam is wrapped in a fire-blocking layer. The foam alone does not pass the requirement. The cushion assembly — foam, fire blocker, and upholstery cover together — is what gets tested, and it is tested under a kerosene burner, not a handheld Bunsen flame.
That is the short answer, and it is also the reason a foam sold as “FR” is not automatically the right foam. The label describes the foam. The requirement is on the assembly.
The cushion test is a different test
Upholstery coverings, coated fabrics, and leather are evaluated under the vertical Bunsen burner test in 14 CFR Part 25 Appendix F Part I. Seat cushions are evaluated under Appendix F Part II — the oil burner test, called out by 25.853(c).
| Upholstery cover | Seat cushion | |
|---|---|---|
| Rule | 25.853(a), App. F Part I | 25.853(c), App. F Part II |
| Flame source | Bunsen burner, 12-second application | Kerosene oil burner, 2-minute exposure at 2 gal/hr |
| Pass criteria | Burn length ≤ 8 in; flame time ≤ 15 s; drip flame time ≤ 5 s | Burn length ≤ 17 in; average weight loss ≤ 10% |
| What is tested | The material | The cushion assembly, as built |
Weight loss is the criterion that surprises people. It is a measure of how much of the cushion was consumed. A bare polyurethane foam block loses far more than 10% under a two-minute kerosene flame, which is exactly why the fire blocker exists.
What the fire-blocking layer is
The fire blocker sits between the foam and the decorative upholstery. It is a textile — commonly aramid, polybenzimidazole (PBI), fiberglass, or pre-oxidized PAN — woven, knitted, or felted, and it encapsulates the foam. Under flame it forms a carbonaceous char barrier that insulates the polyurethane underneath and keeps it from igniting.
Some specialty foams — neoprene, silicone, and certain modified urethanes — can be built to meet 25.853(c) without a separate fire-blocking textile. Those are the exception, and which path applies to your seat is a question for your approval authority, not a catalog decision.
One more construction note: if the cushion also serves as a flotation device, the foam must be closed cell — typically polyethylene — which is a different material from the open-cell urethane used for comfort.
Which rule applies to your aircraft
25.853(c) is a transport-category requirement. Part 23 aircraft — most piston singles and light twins — are certificated to a different basis, and many are not subject to the seat cushion oil burner test at all. Experimental aircraft generally fall outside the certification rules entirely.
None of that changes the physics. Unblocked polyurethane foam burns the same way in a Cessna as it does in an airliner. What changes is what you are legally required to document.
FAA guidance in AC 25.853-1 addresses seat cushion flammability compliance for transport-category aircraft. Ask the A&P, IA, repair station, engineer, or other applicable approval authority what cushion construction and evidence your particular project requires before any upholstery work begins.
Carolyn Fabrics' supply boundary
Carolyn Fabrics does not supply aircraft seat cushion foam, fire-blocking textile, or adhesive. We supply the upholstery cover material. The responsible aviation professional must specify and source the cushion system for the particular seat and approval path.
Do not substitute ordinary furniture foam, marine sew foam, or an older shop roll for a specified cushion system. Sew foam is a thin scrim-backed layer laminated behind a cover for appearance and wrinkle control — it is not a cushion, and it is not a fire blocker.
For the cover, Spirit Millennium is manufacturer-listed under FAA FAR 25.853(a). Manufacturer burn-test documentation is provided only when requested with your order and may not be available after shipment. That material record covers the vinyl. It does not approve the cushion, the seat, or the installation.
Questions to settle before cutting a new cover
- What aircraft and approval basis applies — Part 25, Part 23, or experimental?
- Is the existing cushion being reused, repaired, or replaced?
- What foam, fire-blocking layer, adhesive, and cover construction are required?
- Does the cushion double as a flotation device?
- What testing or conformity records must stay with the work?
- Who makes the final approval determination?
Frequently asked questions
What foam is used in aircraft seats?
Fire-retardant open-cell polyurethane foam is the standard cushion material, densities commonly around 2 lb/ft³. On transport-category aircraft it is encapsulated in a fire-blocking textile. Closed-cell polyethylene is used where the cushion must also function as a flotation device.
Does aircraft seat foam have to be fire rated?
On transport-category aircraft the cushion assembly must meet 25.853(c) under the Appendix F Part II oil burner test: burn length no more than 17 inches and average weight loss no more than 10%. The foam is not certified in isolation — the assembly is what passes or fails.
Can I use regular upholstery foam in an aircraft seat?
Not on a certificated aircraft without an approval basis and test evidence that supports it. Ordinary furniture foam has no flammability documentation and no fire blocker. On experimental aircraft the certification rules generally do not apply, but the burn behavior is unchanged.
What is a fire blocker on an aircraft seat?
A textile layer between the foam and the decorative cover — aramid, PBI, fiberglass, or pre-oxidized PAN — that chars under flame and insulates the foam so it does not ignite. It is what allows a polyurethane cushion to hold weight loss under 10% in the oil burner test.
Does my vinyl burn certificate cover the foam?
No. The material record covers the material tested, in the configuration tested. Foam, fire blocker, thread, and adhesive are separate items with separate documentation.
Is marine sew foam the same as aircraft seat foam?
No. Sew foam is a thin backing laminate used behind a cover for a smooth, plush appearance. It is not a cushion and carries no aviation flammability documentation.