Aircraft Parts Condition Codes Explained

If you have shopped for vintage aircraft parts, you have seen the two or three letter codes stamped next to a listing: NS, OH, RB, RD. They look like shorthand, and they are, but they are not arbitrary. Every one of them is a direct descendant of a classification system the U.S. War Department built to answer one question during two world wars: is this part good enough to put back into service, and if not, what happens to it next. Here is where those codes came from, and exactly what each one means on an AirCorps Depot listing.

A short history of condition codes

The idea of sorting military property by condition did not start in World War II. It started in World War I. In January and November 1918, the War Department issued General Orders 9 and 106, which adopted the word "salvage" specifically to replace the vaguer terms "conservation" and "reclamation" then in use (Quartermaster Corps in WWII Operations). Out of that came the Army's first simple property classes: Class A for new property, Class B for reclaimed property that was still serviceable, Class C for unserviceable property that could be reclaimed, and Class D for unserviceable property not fit for reclamation (Quartermaster Supply history). That A/B/C/D shape, new, serviceable, repairable, and scrap, is the direct ancestor of every condition code in use today.

Between the wars, two developments built the framework the next war would run on. The Navy's 1914 Naval Depot Supply and Stock Catalog became the Federal Standard Stock Catalog in 1929, the first real attempt at a single government item catalog (DLA: History of the Federal Catalog System). And in February 1937, the Army-Navy Aeronautical Board formed a joint committee to eliminate duplicate part specifications between the two services, eventually issuing more than 1,100 Army-Navy Aeronautical Standards (Defense Standardization Program history). That committee is why an AN bolt looks the same whether it came off an Army or a Navy line, a standard that predates Pearl Harbor by four years.

World War II turned this into hard regulation. FM 9-10, Ordnance Maintenance and General Supply in the Field (20 April 1942), set the classification that AR 711-50 required: Serviceable Group A for items ready for immediate issue, Serviceable Group B for everything else serviceable, Unserviceable Group C for items that were unserviceable but economically repairable, and Unserviceable Group D for items not worth repairing (FM 9-10). An Army Service Forces Circular dated 6 December 1943 then defined "condemned," "discarded," "abandoned," and "damaged" property, all of which, by definition, could still be restored to usefulness through repair, refabrication, or renovation (The Ordnance Department: Procurement and Supply). Materiel that failed inspection outright was called "Ordnance rejected" and segregated until it was reworked, granted a waiver, or scrapped, the direct ancestor of a rejected part today.

The Army Air Forces layered its own procedures on top. TM 38-410, Army Air Forces Base Supply Procedure, required every item turned in at a base to pass through a receiving and classification unit where a qualified inspector verified its status as Serviceable, Reparable, or Condemned, stamped in bold letters directly on the paperwork (TM 38-410). The most visible surviving piece of that system is the color coded parts tag the Army Air Corps developed during the war: red for scrap, yellow for serviceable and airworthy, green for not airworthy but repairable (Aviation parts tag, Wikipedia). That color scheme is still on our own tags today, described below.

After the war, having every service run its own classification and cataloging system was too costly to keep. President Roosevelt directed a single U.S. Standard Commodity Catalog in 1945, which matured into the Defense Cataloging and Standardization Act of 1952 and the Federal Catalog System still in use across the Department of Defense today (DLA: History of the Federal Catalog System). The single letter Supply Condition Codes DoD uses now, A through H, are the direct descendants of the Serviceable A/B and Unserviceable C/D groups FM 9-10 set out in 1942 (DoD / Federal Condition Codes, LogTool). The letters changed shape over eight decades, but the underlying question, new or used, serviceable or repairable, worth fixing or not, has not changed at all.

AirCorps Depot condition codes

We group our twelve condition codes into four categories that describe how much work, if any, stands between a part and airworthiness: Unknown, Airworthy, Work Required, and Rejected. It is the same four part logic that runs through the whole history above, just with modern labels.

Code	Category	Meaning	Historical parallel
UK	Unknown	Condition cannot be established, including items from inventory where condition was never recorded. No accompanying paperwork or certification. A physical inspection is required before the part can move to another code. Often loosely called "As Is" in casual sales conversation, which is different from the formal AS code below.	Closest analog is FM 9-10's Unidentified Supplies group, items not identified by stock number or nomenclature at all.
NE	Airworthy	New: never installed, zero cycle time, produced by an FAA-approved manufacturer (OEM, PMA holder, TC or PC holder) or another acceptable procurement method, with documentation that stays with the part. Can be resold supplier to supplier and stay NE, but the designation changes to NS the moment it is sold from a supplier to an end user.	Direct descendant of "accepted matériel," new production stamped with the Ordnance escutcheon once it passed inspection, and the original Serviceable Group A definition of new items ready for immediate issue.
TST	Airworthy	Tested: visually inspected and functionally tested against OEM data, an AD, a T.O., a CMM, or other applicable technical data. Common triggers are scheduled interval testing, a part that sat out of service for a long time (an NS part, for example), or a part pulled from one airframe for reinstallation on another.	Descends from the wartime practice of having a technically qualified inspector verify status before anything was stamped and routed onward.
RD	Airworthy	Repaired: inspected, found unairworthy, and repaired back to original condition or serviceable allowance under an FAA-approved process or equivalent.	Maps to FM 9-10's Unserviceable Group C, unserviceable but economically repairable, and to the "Reparable" stamp under TM 38-410.
OH	Airworthy	Overhauled: disassembled, cleaned, inspected, repaired as necessary, reassembled, and tested back to original specifications or serviceable allowances under an FAA-approved process.	Direct descendant of the Army's wartime reclamation program, defined in 1943 as repair, refabrication, or renovation back to usefulness.
RB	Airworthy	Rebuilt: a deeper rework than overhaul, using new parts or used parts restored to new tolerances, tested to new-item limits. Must be performed by the original manufacturer or a manufacturer-approved agency under 14 CFR 43.3(j).	Closest wartime parallel is the vocabulary the Ordnance Department used for its combat vehicle reclamation program: repair, rebuilding, renovation, or remanufacture.
NM	Work Required	New Manufacture: produced without an FAA-approved manufacturer, process, or design, most often for non-type-certificated airframes, which 14 CFR 43.1(b)(1) exempts from that requirement. Dimensions, material, and heat treat should be verified before installation.	No direct WWII regulatory analog. The closest parallel is the prewar and wartime lack of standardization the AN, NAS, and MS parts system was built to solve.
NS	Work Required	New Surplus: released as surplus by the military, an OEM, an owner or operator, a repair facility, or a parts supplier. Never installed, zero operating time, often obsolete, and frequently missing its original certification paperwork. Typically needs a Test (TST) before it earns a release to service.	The clearest living link to the WWII surplus story and the postwar disposal of surplus aircraft and components.
AR	Work Required	As Removed: pulled from an airframe or powerplant, with no certification paperwork verifying airworthiness or eligibility for return to service. Must be recertified before reinstallation, or sold As Is if it is not.	Closest historical analog is FM 9-10's Unclassified group, an item identified by nomenclature but not yet examined for condition.
AS	Work Required	As Is: new condition, but lacking the conformity documentation or markings that would qualify it as NE or NS. The buyer is responsible for determining airworthiness and applicability. Distinct from both UK (true unknown condition) and AR (pulled from an airframe), even though all three get loosely lumped together as "as is."	Closest wartime parallel is new production that reached a depot without its individual identification or inspection paperwork.
RP	Work Required	Repairable: economically viable to repair and return to service, though not currently being worked. Often called a core. Typically an As Removed part with no manufacturing traceability, sometimes accompanied by a Non-Incident Statement or removal history.	Same lineage as Unserviceable Group C, and the category the wartime green tag identified: not airworthy, but repairable.
RJ	Rejected	Rejected: unairworthy and will never become airworthy, whether unsalvageable, beyond economical repair, unserviceable, or an unapproved part. Segregated and marked with a Red Tag.	Closest one-to-one match in the whole list: "Ordnance rejected" materiel in WWII was segregated from the line until it was reworked, granted a waiver, or scrapped.

How we document each condition

Every part in the Airworthy category (TST, RD, OH, and RB) leaves our shop with documentation that satisfies 14 CFR 43.9(a): a description of the work performed, the date it was completed, the name of the person who performed the work if different from the approving person, and the signature, certificate number, and certificate type of the person approving the part for return to service. Depending on the job, that documentation is either our shop's Yellow Tag or an FAA Form 8130-3, not both. They serve the same purpose; the 8130-3 is the newer, FAA-standardized form that has largely replaced yellow tags across the industry and is recognized internationally, while the Yellow Tag is our shop's own long-standing serviceable tag.

NE (New) parts do not get a Yellow Tag, since they have never been installed or returned to service. They carry whatever conformity documentation came from the manufacturer or supplier, and that paperwork stays with the part until installation. NS (New Surplus) sits outside the Airworthy category by default; long storage means an NS part typically needs a Test or other inspection confirming it still meets its original specifications and any applicable Airworthiness Directives before it earns its own Yellow Tag or 8130-3. NM, AR, AS, RP, and UK have not cleared an inspection step and are sold without a release to service. RJ parts get a Red Tag instead.

The Yellow Tag is the direct functional descendant of the Army Air Corps' wartime color-coded parts tag: red for scrap, yellow for serviceable and airworthy, green for not airworthy but repairable. The FAA Form 8130-3 is the modern, standardized successor to that same tag: it is not a separate document layered on top of the Yellow Tag, it replaces it for the job it is issued on.

AirCorps Aviation is an FAA 8130-3 facility

AirCorps Aviation is an FAA 8130-3 facility. Parts processed through our shop under that authority receive a Form 8130-3 Authorized Release Certificate as their airworthiness documentation, in place of our standard Yellow Tag, meeting the specific completion and signature requirements FAA regulations set for that form (FAA Order 8130.21H). In practice, this applies to OH, RB, RD, and TST work performed in our own shop. Parts that only pass through documentation review, or that arrived already tagged by another facility, carry whichever tag that originating facility issued. Either way, you are looking at the same underlying release to service, just on different paperwork.

PMA parts

PMA-produced parts in our inventory are coded NM (New Manufacture) rather than NE. Most of our PMA parts go on WWII warbirds operating on an FAA Experimental certificate, most commonly for the exhibition purpose, which 14 CFR 43.1(b)(1) exempts from Part 43's requirements as long as the FAA has not previously issued that airframe a different kind of certificate. Since a warbird's certificate basis (Experimental versus a Limited category type certificate) affects which exemption applies, reach out to our team if you need that detail confirmed for a specific tail number.

Why this matters when you are buying

A condition code is not marketing language. It is the modern end of a documentation chain the War Department started building in 1918 to answer the same question every parts buyer asks today: what exactly am I getting, and can I trust it. When you see OH, RD, RB, or a Tested TST or NS part with a Yellow Tag or FAA Form 8130-3 attached, you are looking at a release-to-service process with an eighty year paper trail behind it. When you see AS, AR, RP, NM, or UK, you are looking at a part where that work has not been done yet, and pricing and risk should follow accordingly.

Questions about a specific listing's condition code or documentation? Reach out to our team, we are happy to walk through what a part has been through before it reaches you.