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PartsTable / COMPONENT / AS21921-4D
AS21921-4D ✓ Verified by PartsTable
— · HOSE FITTING
WHAT YOU NEED TO KNOW
PTFE tape on tapered threads (NPT/BSPT) JIC/AN flare connections seal metal-to-metal — no tape
NPT != BSPT — look identical, NOT interchangeable
PRODUCT OVERVIEW

The INJECTOR ASSEMBLY,FUEL is a the manufacturer industrial component. Key specifications include material: ALUMINUM ALLOY 2014 OR ALUMINUM ALLOY 2024 OVERALL, nut_style: TUBE COUPLING, nut_height: 0.710 INCHES MINIMUM AND 0.730 INCHES MAXIMUM IN, seat_angle: 45.00 DEGREES NOMINAL, thread_class: 3B, thread_series: UNIFIED NATIONAL JOINT FINE (UNJF). This product is currently in active production with full OEM support.

This part is cataloged in the Federal Logistics Information System (FLIS) under NSN 4730-00-555-8203, indicating validated use in U.S. government and defense logistics supply chains. Available through authorized enterprise resellers and TPM (Third Party Maintenance) channels.

Verify compatibility with your specific system configuration before ordering.

WHERE IT FITS
AS21921-4D
NSN: 4730-00-555-8203
FSC: 4730
CAGE: 81343 — SOCIETY OF AUTOMOTIVE ENGINEERS INC (USA)
SPECIFICATIONS
materialALUMINUM ALLOY 2014 OR ALUMINUM ALLOY 2024 OVERALL
nut_styleTUBE COUPLING
nut_height0.710 INCHES MINIMUM AND 0.730 INCHES MAXIMUM IN
seat_angle45.00 DEGREES NOMINAL
thread_class3B
thread_seriesUNIFIED NATIONAL JOINT FINE (UNJF)
special_featuresGRUMMAN AEROSPACE CORP A10 AIRCRAFT; WEAPON SYSTEM ESSENTIAL
thread_directionRIGHT-HAND
surface_treatmentANODIZE OVERALL
length_to_shoulder0.537 INCHES MINIMUM AND 0.557 INCHES MAXIMUM IN
width_across_flats0.562 INCHES NOMINAL IN
nominal_thread_size0.438 INCHES IN
NSN4730-00-555-8203
COMPONENT DIAGRAM
HOSE FITTING — THREAD TYPE IS CRITICAL END A: — STRAIGHT END B: — SPECIFICATIONS Thread: — Material: — Pressure: — PN: AS21921-4D · OEM ⚠ VERIFY BEFORE ORDERING NPT ≠ BSPT — tapered threads look identical but are NOT interchangeable. Wrong thread = leak. JIC (37°) ≠ AN (37°) ≠ SAE 45° — flare angles must match exactly. Measure thread pitch with gauge — visual identification is unreliable ✓ BROKER TIP Always use thread sealant (PTFE tape or pipe compound) on tapered threads (NPT/BSPT). JIC/AN flare fittings seal metal-to-metal — never use tape on flare connections PARTSTABLE TECHNICAL DRAWING — NOT TO SCALE
KEY FEATURES
•
THREAD CLASS: 3B
•
NOMINAL THREAD SIZE: 0.438 INCHES IN
•
CRITICALITY CODE JUSTIFICATION: FEAT
•
MATERIAL: ALUMINUM ALLOY 2014 OR ALUMINUM ALLOY 2024 OVERALL
•
MATERIAL DOCUMENT AND CLASSIFICATION: QQ-A-367,T6 FED SPEC SINGLE MATERIAL RESPONSE OR QQ-A-225/6,T6,T62 OR T851 FED SPEC SINGLE MATERIAL RESPONSE OVERALL
•
THREAD SERIES: UNIFIED NATIONAL JOINT FINE (UNJF)
•
SEAT ANGLE: 45.00 DEGREES NOMINAL
•
THREAD QUANTITY PER INCH: 20
TECHNICAL CHARACTERISTICS (FLIS)
THREAD CLASS3B
NOMINAL THREAD SIZE0.438 INCHES IN
CRITICALITY CODE JUSTIFICATIONFEAT
MATERIALALUMINUM ALLOY 2014 OR ALUMINUM ALLOY 2024 OVERALL
MATERIAL DOCUMENT AND CLASSIFICATIONQQ-A-367,T6 FED SPEC SINGLE MATERIAL RESPONSE OR QQ-A-225/6,T6,T62 OR T851 FED SPEC SINGLE MATERIAL RESPONSE OVERALL
THREAD SERIESUNIFIED NATIONAL JOINT FINE (UNJF)
SEAT ANGLE45.00 DEGREES NOMINAL
THREAD QUANTITY PER INCH20
END ITEM IDENTIFICATIONAIRCRAFT APPLICATION,IROQUIS UH-1,CHINOOK CH-47 HELICOPTER,DELTA DART F-106,F-111. TOMCAT F-14A,STARLIFTER C-141 AIRCRAFT,E-3A AIRCRAFT WARNING AND CONTROL SYSTEM (AWACS) A
WIDTH ACROSS FLATS0.562 INCHES NOMINAL IN
VERIFIED SUBSTITUTES & CROSS-REFERENCES 24
SAE-AS18280Interchangeable
interchangeable cross-reference
interchangeable
MS21921W4Interchangeable
interchangeable cross-reference
interchangeable
MS21921D4Interchangeable
interchangeable cross-reference
interchangeable
15610Interchangeable
interchangeable cross-reference
interchangeable
8318XSInterchangeable
interchangeable cross-reference
interchangeable
476406Interchangeable
interchangeable cross-reference
interchangeable
LIFECYCLE
StatusACTIVE
AvailabilityOEM and secondary market
RoHS CompliantEAR99Not HAZMAT
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FREQUENTLY ASKED QUESTIONS
What is AS21921-4D?
AS21921-4D is a INJECTOR ASSEMBLY,FUEL.
What parts can replace AS21921-4D?
There are 24 known substitutes for AS21921-4D: SAE-AS18280, MS21921W4, MS21921D4 and 21 more. Substitute compatibility should be verified for your specific system.
What is the NSN for AS21921-4D?
AS21921-4D is cataloged in the Federal Logistics Information System (FLIS) under NSN 4730-00-555-8203. This indicates validated use in U.S. government and defense supply chains.
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✓ Validated with multiple authoritative sources, including Government, OEM, and Certified sources.
PartsTable Design LLC · partstable.com
Last verified: July 2026