MIL-DTL-26500 Connectors:
Complete Guide to the Classic Aerospace Bayonet Circular Connector

What MIL-DTL-26500 Is — and Why It Still Matters

MIL-DTL-26500 (originally issued as MIL-C-26500) is the miniature circular connector that wired the first generations of commercial jet aircraft. With its distinctive three-point bayonet coupling, positive keyed polarization, and crimp-and-insert contact system, it became the standard interconnection on Boeing and Douglas airframes from the 707 and DC-8 forward. Millions of these connectors remain in service today on legacy commercial platforms, military aircraft, and ground support equipment — which is why procurement and MRO teams still specify, source, and cross-reference them every day.

Unlike its more famous cousins (MIL-DTL-38999 and MIL-DTL-26482), the 26500 family uses a different contact standard with higher per-contact current ratings, and it has a direct line of descent into the modern MIL-DTL-83723 specification. Both facts matter the moment you try to substitute one connector for another. This guide covers the part numbering, coupling options, contact system, insert arrangements, materials, and cross-reference path to Airoadcon equivalents.

MIL-C-26500 → MIL-DTL-26500 → MIL-DTL-83723: The Lineage

The connector is the same whether you see it written MIL-C-26500 or MIL-DTL-26500 — the U.S. Department of Defense re-designated thousands of its "C" specifications to the "DTL" format around the year 2000 without changing the hardware. The more important lineage note is that MIL-DTL-26500 is now a legacy specification, formally superseded by MIL-DTL-83723. Glenair's own catalog lists 26500 products under a "legacy connector designs superseded by MIL-DTL-83723" banner.

The critical practical point: the two families share the same shell geometry and the same MIL-STD-1554 insert arrangements, and they are documented as intermateable. That means a legacy 26500 application can often be satisfied by a modern 83723 equivalent — same cavity layout, same contacts, same coupling envelope — which is exactly the substitution path Airoadcon supports. We cover the 83723 family in detail in our MIL-DTL-83723 guide.

Coupling: Bayonet vs Threaded

One of the first things to pin down when sourcing a 26500 connector is the coupling style — both are valid under the specification, and they are not interchangeable on a panel:

Bayonet coupling is the classic 26500 signature — fast to mate, self-locking against vibration, and easy to verify by feel. The threaded variant appears most often on single-hole and jam-nut receptacles where the coupling ring must apply a controlled axial load.

Part Number Breakdown: MS24264 / MS24265 / MS24266

MIL-DTL-26500 connectors are ordered under MS24264-series part numbers. The shell style is the first thing the number encodes:

A full part number reads, in order: style + class + shell size + insert arrangement + contact type + polarization. For example, MS24264R22-19PN decodes as:

• MS24264 — square-flange receptacle
• R — Class R (aluminum shell, black anodized)
• 22 — shell size 22
• 19 — insert arrangement 22-19 (19 × size-16 contacts)
• P — pin contacts
• N — normal polarization (alternate key positions are also available to prevent mismating)

Shell sizes run from 8 through 24 (larger sizes appear in specialized variants), and insert arrangements are defined by MIL-STD-1554. Always confirm the exact arrangement number against the insert-arrangement table — a "22-19" and a "22-55" share a shell size but hold a completely different contact population.

Contact System: BACC47, Not AS39029

This is the single most important technical difference between 26500 and the 38999/26482 families, and the one that causes the most cross-reference mistakes. MIL-DTL-26500 uses BACC47 crimp contacts (a Boeing-specified contact), not the AS39029 contacts used by 38999 and 26482. The contact geometries and current ratings are not the same:

Notice the gap versus the AS39029 system: a size-16 contact in a 26500 connector carries up to 22 A, whereas the same physical size in 38999/26482 is rated 13 A. A size-12 contact reaches 41 A versus 23 A. Do not blindly substitute a 38999 connector into a 26500 circuit — the higher per-contact current rating may be the reason the original design chose 26500 in the first place. For a fuller treatment of how contact sizes map to current and wire gauge across standards, see our contact-size guide.

Insert Arrangements (MIL-STD-1554)

The insert arrangements available under 26500 are defined by MIL-STD-1554 and range from 2 to 61 circuits. A few of the most common:

Because the arrangements are the same MIL-STD-1554 layouts used by 83723, a 26500 insert maps directly onto a 83723 equivalent — a key reason the two standards are intermateable and a key lever when you need to modernize a legacy BOM.

Materials, Classes & Environment

The two primary environmental classes are distinguished by shell material and finish:

Both classes meet the MIL-DTL-26500 altitude-immersion sealing test and are qualified against the fluids that matter in an aircraft environment — MIL-PRF-5606 hydraulic fluid and MIL-PRF-23699 / MIL-PRF-7808 lubricating oils. Beyond the two main classes, the family also includes hermetic (glass-to-metal sealed) receptacles for pressurized bulkheads and higher-grade variants for space and firewall service — extending the same part-numbering logic into specialized territory.

26500 vs 26482 vs 83723: Which Spec Do You Actually Need?

The decision rule is simple: if you are maintaining a legacy airframe and need an exact form/fit/function drop-in, order the 26500 part. If you are starting a new design or modernizing a BOM, specify 83723 — you get an active, current specification, AS39029 contacts, and (for most arrangements) a connector that still mates into the legacy envelope.

Manufacturer Cross-Reference: Who Makes MIL-DTL-26500

For cross-reference assistance — mapping an Amphenol Pyle ZZW, a Glenair hermetic receptacle, or a Cinch BACC47 part to the Airoadcon equivalent — contact our technical team with your target part number. We verify the coupling, class, insert arrangement, and contact rating 1:1 against your existing part.

MIL-DTL-26500 Selection Checklist

• Confirm the coupling — bayonet or threaded; they are not interchangeable on a panel.
• Pin the class — R (aluminum/black anodized) vs E (stainless/passivated) vs hermetic for pressure bulkheads.
• Verify the insert arrangement against MIL-STD-1554 — same shell size, different arrangements, very different contact counts.
• Check the contact current rating — BACC47 #16 carries 22 A, not 38999's 13 A; don't substitute down in rating.
• Decide legacy vs modern — exact 26500 drop-in for MRO, or a 83723 equivalent for new designs (intermateable in most arrangements).
• Specify polarization — normal (N) or an alternate key position if adjacent connectors could cross-mate.
• Add the right accessory — backshell and strain relief sized to the shell size and cable bundle.