MS29512-06 - Lycoming OEM Fuel Injector Nozzle O-ring Seal

MS29512-06 – Lycoming OEM Fuel Injector Nozzle Seal (Four-Lobed Ring)

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The MS29512-06 is a high-performance, four-lobed seal manufactured in strict accordance with Military Standard MS29512 and specified by Lycoming for a flight-critical application: sealing fuel injector nozzles at the cylinder head. While it performs the function of an O-ring, this component's X-shaped cross-section offers significant engineering advantages, providing a more stable and redundant seal. Its role is to prevent both the leakage of raw fuel onto the hot cylinder head and the ingress of unmetered air (induction leak) into the intake port, either of which can create a serious operational hazard.

This seal is fabricated from a Fluorocarbon (FKM) elastomer, commonly known as Viton®, which is specifically chosen for this application. This material provides superior resistance to the degrading effects of aviation gasoline (Avgas), heat, and oil. The integrity of the fuel and induction system at each individual cylinder depends on the performance of this precision seal.

Key Features

• Military Standard (MS) Certified: Manufactured to the exact material and dimensional tolerances of the MS29512 specification, ensuring reliable performance.

• Four-Lobed Profile for Superior Sealing: The X-shaped cross-section provides two distinct sealing surfaces on each side, creating a more stable and redundant seal compared to a standard O-ring.

• Fluorocarbon (FKM/Viton®) Material: Offers exceptional resistance to aromatic hydrocarbons in fuel, high temperatures at the cylinder head, and engine oil, preventing swelling or hardening.

• Prevents Fuel and Induction Leaks: Creates a positive seal that both contains fuel pressure and prevents unmetered air from leaning out the mixture for that cylinder.

• Resists Spiral Twist: The square-like profile of the four-lobed design is inherently stable and resists the twisting and rolling in the groove that can lead to the failure of standard O-rings.

Technical Specifications

• Part Number: MS29512-06

• Component Type: Four-Lobed Seal Ring (Quad-Ring® Type)

• Governing Specification: MS29512

• OEM Applicability: Lycoming Engines, Continental Motors, and other manufacturers requiring MS-standard seals.

• Material: Fluorocarbon (FKM), Viton®.

• Hardness: 75 Durometer Shore A

• Size (AS568A Dash Number): -006

• Dimensions:

  • Inside Diameter: 0.114 inches (2.90 mm)

  • Cross-Section: 0.070 inches (1.78 mm)

Engine Compatibility

The MS29512-06 is a standard hardware component used on nearly all fuel-injected reciprocating aircraft engines. It is the specified seal for fuel injector nozzles on the vast majority of fuel-injected Lycoming engines, including but not limited to:

• IO-320, IO-360, LIO-360, AEIO-360 Series

• IO-540, TIO-540, LTIO-540, AEIO-540 Series

• IO-580 and IO-720 Series

Crucial Note: The correct part number for a specific application must be verified against the engine's Illustrated Parts Catalog (IPC) or maintenance manual.

Item Specification

  Fits in

1. Bombardier Challenger 300
2. Bombardier Challenger 601
3. Bombardier Challenger 604
4. Bombardier Challenger 605
5. Bombardier Global Express
6. Bombardier Learjet 40
7. Bombardier Learjet 45
8. Bombardier Learjet 55
9. Bombardier Learjet 60 - all variants
10. Dassault Falcon 2000 all variants
11. Dassault Falcon 900 all variants
12. Embraer Legacy 600-650
13. Gulfstream G-IV/GIV-SP/G-400/G-450/G-300
14. Gulfstream G-V/G-V-SP/G-550/G-500
15. Pilatus PC-12
16. Piper Aircraft PA-42 Cheyenne
17. Textron Aviation Beechcraft King Air 100 - all variants
18. Textron Aviation Beechcraft King Air 200 - all variants
19. Textron Aviation Beechcraft King Air 300 - all variants
20. Textron Aviation Beechcraft King Air 90 - all variants
21. Textron Aviation Beechcraft Premier
22. Textron Aviation Bell 206 Jetranger/Longranger
23. Textron Aviation Cessna 500 Citation I-ISP
24. Textron Aviation Cessna 510 Citation Mustang
25. Textron Aviation Cessna 525 Citation Citationjet
26. Textron Aviation Cessna 550 Citation I-II-Bravo
27. Textron Aviation Cessna 560 Citation V-Ultra-Encore-Excel-XLS
28. Textron Aviation Cessna 650 Citation III-IV-VI-VII
29. Textron Aviation Cessna 680 Citation Sovereign
30. Textron Aviation Cessna 750 Citation X
31. Textron Aviation Hawker 400-400XP
32. Textron Aviation Hawker 800
33. Textron Aviation Hawker 800XP-850XP
34. Textron Aviation Hawker 900XP

Applications

• Primary Application: Sealing the base of the fuel injector nozzle where it is installed into the intake port of the cylinder head.

• Required Replacement: This seal must be replaced whenever a fuel injector nozzle is removed for cleaning, inspection, or replacement. Typically, two seals are used per nozzle.

Why Choose MS29512-06?

Choosing a genuine MS29512-06 is a critical decision for both safety and engine health. The failure of a fuel injector seal can have two dangerous outcomes: an external fuel leak onto a hot cylinder creates a severe fire risk, while an internal air leak (induction leak) will cause that one cylinder to run dangerously lean, leading to extreme temperatures and potentially destructive detonation. The MS-standard part, with its advanced four-lobed geometry and certified FKM material, is specifically engineered to provide the reliable, long-lasting seal required for this high-stress, high-temperature environment.

The engineering superiority of the MS29512 four-lobed seal geometry over a standard O-ring (toroidal cross-section) is significant. A standard O-ring seals along a single, narrow, and potentially unstable tangent line of contact. The MS29512's X-shaped profile creates two distinct and stable sealing footprints on both the inner and outer surfaces, effectively doubling the sealing redundancy. The space between the lobes acts as a reservoir for lubricant, which reduces friction and wear in dynamic applications. Crucially, the relatively square cross-section of the four-lobed design is inherently resistant to spiral twist failure, a common failure mode for O-rings in reciprocating or oscillating applications where the ring can roll in its groove, leading to deep, helical cuts and seal failure. Furthermore, the mold's parting line (a potential source of imperfections) is located in the trough between the lobes, away from the critical sealing surfaces, eliminating a primary source of leaks that can be present in standard O-rings.

Note: This is a flight-critical, single-use component. These seals MUST be replaced with new ones every time a fuel injector nozzle is removed. Re-using a seal can lead to fuel or air leaks. Care must be taken to prevent cutting or nicking the seal during installation. The seal should be lightly lubricated with engine oil or an approved fuel-soluble lubricant prior to installation. Installation must be performed by a certified A&P mechanic in accordance with the applicable Lycoming maintenance manual.

Documentation

The definitive technical requirements for this component are detailed in Military Standard MS29512. Applicability must be confirmed via the engine's parts catalog.