What Are BMS Specifications? A Guide for Aircraft Buyers
What are BMS specifications? BMS stands for Boeing Material Specification, a designation used to identify requirements for materials used in Boeing aerospace applications. For aircraft buyers, a BMS number helps narrow the required material, but the full requirement may also include a revision, type, class, grade, product part number, and aircraft-specific instructions.
Key Takeaways
- BMS means Boeing Material Specification; the number identifies a specification, not necessarily one unique product.
- Type, class, grade, and revision details can distinguish requirements within the same BMS family.
- A supplier listing that cites a BMS specification does not, by itself, establish suitability for a particular repair or aircraft.
- A useful RFQ includes both the exact manufacturer part number and the complete specification callout from the purchasing or maintenance record.
What a BMS Specification Identifies
A BMS designation provides a reference point for material requirements. Those requirements may concern a material category, its properties, its form, or how it is identified and evaluated. The designation is particularly useful when an engineering document calls for more than a generic description such as “fiberglass fabric,” “epoxy filler,” or “silicone sealant.”
It is important to separate the specification from the item being purchased. BMS 5-28, for example, appears in listings for two different epoxy materials: one identified as Type 3 and another as Type 6. A buyer searching only for “BMS 5-28 epoxy” could therefore receive results for materially different products. The complete callout—and the required part number when one is specified—makes the request more precise.
A BMS designation is also different from an aircraft part number. A part number identifies an item in a manufacturer’s catalog or purchasing system; a BMS reference identifies a material specification cited in the item’s documentation. They may appear together on a drawing, requisition, or product listing, but neither should be assumed to replace the other.
How to Read a BMS Callout
Start with the BMS number, then read every qualifier that accompanies it. The formatting is not a universal code in which each digit has the same meaning across all BMS specifications. Instead, treat the complete string in the controlling document as the purchasing requirement.
- Specification number: A reference such as BMS 5-28 identifies the specification family.
- Type, class, or grade: These qualifiers identify a more specific requirement when they appear. For example, a listing describes an epoxy filler as BMS 5-28 Type 3, while another describes an epoxy syntactic compound as BMS 5-28 Type 6.
- Revision: A letter may appear as part of the specification reference. The listed silicone elastomer DOWSIL 93-006-1-RF, for instance, cites BMS 5-175D. Record the revision exactly when it is part of the requirement.
- Product identification: Capture the manufacturer and full part number separately. Package or kit details may also be necessary to distinguish the item being requested.
Not every product code beginning with “BMS” is merely a specification citation. The fiberglass fabric part number BMS9-3-TYH3CL7ST7781/38 contains additional characters beyond the BMS 9-3 reference; its listing identifies the fabric as BMS 9-3 Style 7781. Preserve the entire part number rather than shortening it to “BMS 9-3 fabric.” For more on identifying the underlying material, see the fiberglass fabric buying guide for aircraft MRO.
Examples Across Aircraft Material Categories
BMS references occur across different material categories. The examples below show why a specification number should be read alongside the product description and any type, class, grade, or style information.
| Listed product | Material and stated BMS reference | Distinction to capture |
|---|---|---|
| BMS9-3-TYH3CL7ST7781/38 | Dry fiberglass fabric; BMS 9-3 Style 7781 | The listing identifies an 8-harness satin weave. Retain the full fabric part number and style. |
| EPOCAST1511-A/B | Epoxy edge filler; listed as qualified to BMS 5-28 Type 3 | It is described as a non-flow filler for honeycomb edges and metal fairings. |
| EPOCAST1636-A/B | Epoxy syntactic compound; listed as meeting BMS 5-28 Type 6 | The Type 6 reference distinguishes it from the Type 3 filler above. |
| DAPCO-18-4F | Two-component silicone paste; listed as meeting BMS 5-63 | The listing describes coating, sealing, and filleting uses; specify the product, not just “silicone.” |
These are examples of how products are described in listings, not a cross-reference showing that products within a specification family are interchangeable. Even a shared BMS number can encompass distinct types, as the two BMS 5-28 examples demonstrate.
How Buyers Can Check a Requirement Before Sending an RFQ
The most reliable starting point is the document that created the demand: a drawing, bill of materials, maintenance task, or internal purchasing record. Copy its wording rather than reconstructing a specification from a catalog search result. If that document gives only a shorthand description, ask the responsible engineering or maintenance team for the missing identifier before treating a search match as the requested material.
- Compare complete identifiers. Check the BMS number and every stated revision, type, class, grade, or style against the requirement.
- Verify the product identity. Compare the manufacturer name, full part number, material form, and any specified kit or package configuration.
- Identify documentation needs. State what product documentation or traceability information the purchase requires, rather than assuming every shipment includes the same records.
- Keep substitutions separate. If the named part cannot be quoted as requested, ask that any proposed alternative be identified explicitly for review.
For example, a vague request saying “quote BMS 5-28 epoxy” leaves open which type and product are needed. A clearer request is: “Please quote Huntsman EPOCAST1511-A/B, listed as BMS 5-28 Type 3. Confirm the quoted part number and kit configuration, and identify any proposed substitution separately.” That wording gives the supplier a specific item to match while preserving the type distinction.
Airworthiness caution: A catalog description or supplier statement of specification compliance is not a substitute for required approvals or an engineering determination. Confirm the applicable aircraft maintenance documentation and manufacturer’s data sheet before selecting, substituting, mixing, applying, or installing a material.
Sourcing from CraftJetAero
Buyers can request a quote from CraftJetAero by part number. Include the complete BMS callout, manufacturer, quantity, required configuration, and any documentation requirements in the request so the quoted item can be compared with the purchasing record.
Frequently Asked Questions
What does BMS stand for in aerospace materials?
BMS stands for Boeing Material Specification. It is a material specification reference, not a universal part-number format.
Is a BMS number the same as a product part number?
No. A BMS number identifies a specification, while a product part number identifies an item from a manufacturer or supplier. Some part numbers contain a BMS reference, so record the complete part number as well as the specification.
Can two products cite the same BMS number?
Yes. Listings for EPOCAST1511-A/B and EPOCAST1636-A/B both cite BMS 5-28, but identify Type 3 and Type 6, respectively. The shared number alone is not enough to specify the same material.
What details should an RFQ include besides the BMS number?
Include the full manufacturer part number and every qualifier in the requirement, such as revision, type, class, grade, or style. Add quantity, configuration, and documentation requirements where applicable.
Does a product listing that cites BMS establish that it fits my repair?
No. The listing is a starting point for identifying a candidate product; the specific application and its controlling documents determine whether that product is appropriate.