Are AN, MS and NAS parts interchangeable?
Not as a rule. The public notices describe three different cases. A document was renamed and the part number kept (MS20470 under NASM20470). A standard was superseded by another with different part numbers, listed in a cross-reference table (AN960 and NAS1149). Or the two numbers are different parts that look alike (AN3 and NAS6203). The notice for the exact part number says which case applies. The aircraft's IPC, SRM or engineering authority decides what may be installed.[1][2][3][4][5]
AN470, MS20470, NASM20470 →
AN470 superseded by MS20470. MS20470H superseded by NASM20470 in 1998; part numbers not changed.[5][1]
AN3, NASM3, NAS6203 →
AN3 thru AN20 superseded by NASM3 thru NASM20 in 1999; part numbers identical. NAS6203 is a separate close tolerance bolt standard.[4][5]
AN960, NAS1149 →
AN960 cancelled in 2011. Notice 2 of 2016 says NAS1149 supersedes it and lists a different NAS1149 part number against each AN960 part number.[2][3]
AN365, MS20365, MS21044, MS21042 →
AN365 cancelled in 1958, superseded by MS20365. MS20365 cancelled in 1966. MS21044 says it can replace both except in 7/16-20, and not the reverse. MS21042 lists a substitute for some AN365 dash numbers and none for others.[6][7][8][9][10]
MS20470, MS20426, NAS1097 →
Three head styles. For joint strength data in the sheet critical range, MIL-HDBK-5J says fasteners with different head sizes "(NAS 1097, MS 29694, or MS 20426)" are "different fasteners" that "require separate tests".[11]
NAS1303, NAS6603
Not in a public source. No public document read for this page says that one replaces the other or what differs. Both sheets are AIA documents. What is public: the FAA lists NAS1303-1320 as "Bolt, hex. head, close tolerance, 160,000 psi" and NAS6604-6620 as "Bolt, hex head, long thread, alloy steel". AIA lists NAS6603-NAS6620 at Rev 11, 31 December 2025, titled "BOLT, TENSION, HEX HEAD, CLOSE TOLERANCE, ALLOY STEEL, LONG THREAD, REDUCED MAJOR DIA., SELF-LOCKING AND NONLOCKING, 160 KSI Ftu". The Department of Defense adopted NAS6603 thru NAS6620 on 5 December 1980 and NAS1303 thru NAS1320 on 6 July 1983.[5][12][13][14]
This page reports what public documents print. It does not approve a substitution. The aircraft's IPC, SRM or engineering authority decides what may be installed.
Reference only: the controlling drawing, its process spec and the manufacturer's installation instructions govern. How to use these answers
What a notice can say4
- A renamed document, from MS20470H Notice 1: "The Part Identification Numbers (PIN) for MS20470H and the part numbers for NASM20470 are identical. The part numbers have not been changed."[1]
- A different part number, from AN960 Notice 2: "Table 1 provides a detailed cross-reference of cancelled AN960 Part or Identifying Numbers (PIN) and replacement NAS1149 PINs." The same page adds: "The supersession information is valid as of the date of this notice and may be superseded by subsequent revisions of the superseding document."[3]
- A one-way statement, from MS21044H note 4: "AN365, MS20365 AND NAS1021 NUTS CANNOT UNIVERSALLY REPLACE THE MS21044 NUTS."[9]
- FAA AC 43.13-1B, para 7-44: "Do not substitute for close-tolerance fasteners without specific instructions from the aircraft manufacturer or the FAA."[5]
Not in a public source2
- NAS and NASM sheets are AIA documents and are sold, not published. Where a difference is printed only on one of them, these pages say so and give no number.
- NAS1303 vs NAS6603 has no page of its own: no public document states the supersession or the differences.
Sources14
Sources
Each number above links to its document. Scanned sheets were read by eye and re-read by OCR; the check script is in the repository under docs/audit-2026-10/reddit-pages.
- MS20470H Notice 1 (18 August 1998) (Department of Defense)
- AN960 Rev 21 Notice 1 (16 September 2011) (Department of Defense)
- AN960 Rev 21 Notice 2 (15 January 2016) (Department of Defense, from DLA ASSIST)
- AN3 thru AN20 Rev 12 Notice 1 (1 December 1999) (Department of Defense)
- FAA AC 43.13-1B (Change 1) (FAA)
- AN365 document record (DLA ASSIST)
- MS20365 document record (DLA ASSIST)
- MS20365 Rev C (5 September 1958) (Department of Defense)
- MS21044 Rev H (21 September 1993) (Department of Defense)
- MS21042 Rev M (6 January 1995) (Department of Defense)
- MIL-HDBK-5J (31 January 2003) (Department of Defense)
- AIA NAS/NASM Mailing 25-13 (31 December 2025) (Aerospace Industries Association)
- NAS6603 thru NAS6620 DoD adoption notice (DLA ASSIST)
- NAS1303 thru NAS1320 DoD adoption notice (DLA ASSIST)
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