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BS SP — Aircraft Fasteners and Components Specifications (SP) Single-File Series Overview (22 Standards)
Aircraft Fasteners and Components Specifications (SP) — 22 Standards
📋 BS SP is the British aircraft component specification series issued by BSI for aircraft fasteners and mechanical components, including washers, bolts, screws, nuts, split pins, turnbuckles and cable fittings. The SP specifications originated in the early standardisation practice of the British aircraft industry; some items supersede parts from the Royal Aircraft Establishment (A.G.S.) part-numbering system. This review brings together 22 single-file SP specifications in this batch.
💡 Though small, aircraft fasteners matter to flight safety: material, heat treatment, thread tolerance, plating and locking performance are strictly specified. The SP specifications unified hundreds of aircraft standard parts, providing a common language for manufacture, procurement and inspection.
1. Series Background 📌
The British aircraft industry developed a huge standard-parts system between the two world wars, and the BS SP series is its national-level specification vehicle. SP specifications define the material, dimensions, performance and inspection requirements of aircraft fasteners and components, covering washers (plain, lock, crinkle and tab washers), fasteners (bolts, screws, nuts, self-locking nuts, anchor nuts, split pins), connecting parts (turnbuckles, fork ends, ball ends, eye bolts) and cable assemblies. Many early SP specifications have been revised several times (e.g. +A3 amendments), and some are still referenced by the aerospace industry today.
The 22 SP specifications in this batch span from 1949 to 2016 and can be grouped roughly into: washers (SP 8, 10, 13, 22, 122, 126, 134, 139); fasteners (SP 33, 41, 49, 55, 57, 59, 66, 107, 114, 115, 142); cables and connecting parts (SP 94, 119); the numbering conventions (e.g. B.A. threads, unified hexagons) reflect the historical convergence of British and American standards in aircraft fasteners.
⚠️ Aircraft fasteners are high-safety items; selection and acceptance must follow the currently valid edition and airworthiness requirements. Some older SP specifications have been superseded by European aerospace standards (e.g. EN) or industry specifications — verify current status before citing.
2. Standard Inventory (22 items) 📚
The table below lists all 22 single-file BS SP specifications in this batch, ordered by number, with the document number and subject.
| Document | Subject |
|---|---|
| BS SP 8:1949 | Specification for turnbuckles (tension rod type) for aircraft purposes |
| BS SP 10:1951 | Specification for washers for aircraft purposes |
| BS SP 13:1949 | Specifications for aircraft washer lock assemblies (aircraft use) |
| BS SP 22:1950 | Specification for B.A. washers for aircraft purposes (primarily for instrument use) |
| BS SP 33:1951 | Specifications for aircraft nuts and bolts (bolt and nut assemblies) |
| BS SP 41:1951 | Aircraft cable assemblies – Ball ends for swaging on cable (replacing A.G.S. parts) |
| BS SP 49:1953 | Specifications for ball ends for swaging on cable (aircraft use) |
| BS SP 51:1953 | Specifications for aircraft clevis pins and split pins (cotter pins) |
| BS SP 55:1953 | Aircraft rod-end (clevis) fittings and turnbuckle parts |
| BS SP 57:1955 | Aircraft anchor nuts (replacing A.G.S. parts) |
| BS SP 59:1955 | Specifications for aircraft split pins (cotter pins) |
| BS SP 66:1955 | Aircraft eye bolts and related parts |
| BS SP 94:1964 | Specification for aircraft cable parts and fittings |
| BS SP 107:1954 | Specifications for aircraft bolts, screws, nuts and washers (aerospace hardware series) |
| BS SP 114:1955 | Specification for aircraft self-locking nuts |
| BS SP 115:1956 | Specifications for aircraft screws and fasteners |
| BS SP 119:1957 | High tensile steel fork ends for aircraft cables |
| BS SP 122:2016 | Aerospace series – Washers for unified hexagons for aircraft (primarily for packing) |
| BS SP 126:1959 | Washers for unified hexagons for aircraft (primarily for facing) |
| BS SP 134:1968 | Specification for copper beryllium crinkle washers (aircraft use) |
| BS SP 139:1969 | Specification for aircraft lock washers and tab washers |
| BS SP 142:1973 | Aircraft bolts and nuts – Unified hexagon-head bolt specifications |
3. Technical Points of Representative Documents 🔬
1. BS SP 122:2016 — Aerospace Series: Washers for Unified Hexagons for Aircraft (Primarily for Packing)
This specification defines the requirements for washers for unified hexagons for aircraft, used primarily for packing, specifying dimensions, material and surface treatment. As one of the newer SP specifications in this batch, it reflects the combination of UK aerospace fastening standards with the unified-thread system, serving gap compensation and anti-loosening assistance in hexagon bolt/nut assemblies.
2. BS SP 107:1954 — Aircraft Bolts, Screws, Nuts and Washers (Aerospace Hardware Series)
This specification covers the general requirements of aircraft bolts, screws, nuts and washers, a typical representative of British aircraft fastening standardisation. It specifies material grades (mostly alloy or corrosion-resistant steel), heat-treatment state, thread accuracy, mechanical properties and surface treatment (e.g. cadmium or zinc plating), providing the basic technical requirements for the manufacture and acceptance of aerospace hardware.
3. BS SP 134:1968 — Copper Beryllium Crinkle Washers Specification
Copper beryllium alloys have excellent elasticity and fatigue resistance; their crinkle washers are used for elastic compensation and anti-loosening in aircraft assemblies. This specification defines the size series, material composition, and hardness and elasticity requirements after heat treatment, and is an important basis for selecting anti-loosening washers in aviation.
4. BS SP 119:1957 — High Tensile Steel Fork Ends (for Aircraft Cables)
This specification defines the dimensions, material and performance requirements of high tensile steel fork ends for aircraft cables. Fork ends connect cables to control mechanisms and carry tension/compression loads; their thread and fork dimensions must mate precisely with cable terminals and pins, and they are key parts for the safety of flight control systems.
5. BS SP 49:1953 — Ball Ends for Swaging on Cable
This specification defines the requirements for ball ends for swaging on cable ends. Ball ends are connected to cable terminals by a swaging process for reliable anchoring of control cables; the specification defines ball dimensions, geometric requirements of the swaging zone and material performance, ensuring the strength and reliability of the swaged connection.
✅ The five representative specifications above cover modern unified-hexagon washers, general aerospace hardware, copper-beryllium anti-loosening washers, cable fork ends and swaged ball ends, showing the technical evolution of the SP series from traditional standard parts to current aerospace parts. The remaining 17 are listed in the full inventory table.
4. Engineering Practice 🛠️
- ✈️ Standard-part selection: SP specifications can be used directly for selecting washers, bolts and nuts in aircraft assembly, ensuring interchangeability and traceability.
- 🔩 Anti-loosening and locking: self-locking nuts (114), lock washers (139), crinkle washers (134) and split pins (59) together form the anti-loosening system of aircraft connections.
- 🛠️ Procurement and inspection: the material, heat-treatment and dimensional requirements in the specifications are the basis for procurement technical agreements and incoming inspection of aircraft parts, implemented together with airworthiness management.
- 🔗 Control systems: turnbuckles (8, 55), fork ends (119), ball ends (49) and cable assemblies (94) serve flight control and actuation systems.
5. Frequently Asked Questions ❓
❓ Q: What kind of specification is the BS SP series?
A: SP (Specification) is the British aircraft component specification issued by BSI, defining the material, dimensions, performance and inspection requirements of aircraft fasteners and mechanical components — specification documents of a standard-parts nature.
A: SP (Specification) is the British aircraft component specification issued by BSI, defining the material, dimensions, performance and inspection requirements of aircraft fasteners and mechanical components — specification documents of a standard-parts nature.
❓ Q: What are the A.G.S. numbers in the SP specifications?
A: A.G.S. (Aircraft General Standard) is the early British standard-parts numbering system set by the aircraft industry; SP specifications often state “Replacing A.G.S. …”, i.e. superseding the corresponding A.G.S. parts and bringing them into the national specification system.
A: A.G.S. (Aircraft General Standard) is the early British standard-parts numbering system set by the aircraft industry; SP specifications often state “Replacing A.G.S. …”, i.e. superseding the corresponding A.G.S. parts and bringing them into the national specification system.
❓ Q: Can older SP specifications still be used directly?
A: Verify the current edition. Many SP specifications remain referenced because of continued use (kept valid by amendments), but some have been superseded by European aerospace standards such as EN; selection must follow the current status and airworthiness requirements.
A: Verify the current edition. Many SP specifications remain referenced because of continued use (kept valid by amendments), but some have been superseded by European aerospace standards such as EN; selection must follow the current status and airworthiness requirements.
🔍 Q: Why are material and heat treatment so strict for aircraft fasteners?
A: Aircraft fasteners endure alternating loads, vibration and temperature change; fatigue and corrosion are the main failure modes. Strict control of material composition, heat treatment and plating is the precondition for strength, toughness and corrosion resistance.
A: Aircraft fasteners endure alternating loads, vibration and temperature change; fatigue and corrosion are the main failure modes. Strict control of material composition, heat treatment and plating is the precondition for strength, toughness and corrosion resistance.