Equipment / Furnishings - BMS 8-39 Urethane Foam Fire-Retardant Seals - Replacement
- Published
- Effective
- Deadline
AI-generated summary of the official EASA document. Verify against the PDF before acting.
What to do
Operators of affected Boeing 747-400, -400D, and -400F series airplanes must replace the BMS 8-39 urethane foam seals with BMS 1-68 silicone foam rubber seals within 72 months from the effective date of February 22, 2022. They must also perform a general visual inspection for tube or wire penetrations in the foam and seal any found penetrations according to Boeing Special Attention Service Bulletin 747-25-3381, Revision 3.
Summary
The Federal Aviation Administration's Airworthiness Directive 2021-26-10 addresses certain Boeing 747-400, -400D, and -400F series airplanes. It mandates the replacement of Boeing Material Specification (BMS) 8-39 urethane foam seals used in various areas of these aircraft due to deterioration of their fire-retardant properties over time. This directive aims to maintain fire safety by ensuring proper sealing in critical compartments.
What changed
This new airworthiness directive introduces a requirement to replace the BMS 8-39 urethane foam seals with BMS 1-68 silicone foam rubber seals in specified areas of the affected Boeing 747 models. It also mandates a general visual inspection for any penetrations in the foam and sealing of those penetrations. This AD is a new regulation rather than an amendment and establishes compliance procedures and timelines.
Why it matters
This directive is critical for aviation professionals because the deteriorated urethane foam seals can fail to maintain adequate Halon concentrations in cargo compartments, compromising fire suppression capabilities. Operators and maintenance organizations must address this to prevent fire or smoke penetration in hard-to-access areas, thereby ensuring continued airworthiness and safety compliance.
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