Aviation Glossary

FAA document that certifies a part is in an airworthy condition. Required for return-to-service in the U.S. and accepted by many international authorities.

UK agency investigating civil aviation accidents. Equivalent to the U.S. NTSB. Publishes detailed accident reports.

Mandatory FAA order requiring inspection, repair, or modification of an aircraft or component within a specified time to correct an unsafe condition.

System where aircraft broadcast GPS-derived position automatically. ADS-B Out was mandated for most U.S. airspace in 2020. Enables surveillance without ground radar.

FAA-approved document that must be carried aboard the aircraft. Contains limitations, normal/emergency procedures, and performance data.

U.S. trade association representing major aerospace and defense manufacturers. Develops industry standards and advocates on regulatory issues.

Same as IPC — alternate term used by some manufacturers (notably Airbus). Contains effectivity codes to specify which aircraft serial numbers a part applies to.

OEM-published manual with step-by-step procedures for maintaining and servicing an aircraft. The primary reference for line and base maintenance.

Brazil's civil aviation authority. Regulates aircraft certification and airworthiness within Brazil.

Critical status indicating an aircraft cannot fly due to a missing or unserviceable part. AOG situations command premium pricing and expedited logistics.

Small turbine engine providing electrical power and bleed air on the ground without running the main engines. Also used for engine starting.

U.S. trade association representing FAA Part 145 certificated repair stations. Advocates on MRO regulatory and policy issues.

SAE aerospace quality management system standard, based on ISO 9001 with additional aviation requirements. Required for most aerospace supply chain qualification.

SAE quality standard specifically for aviation parts distributors. Requires traceability documentation and counterfeit part prevention programs.

Urgent service bulletin issued by an OEM for safety-related issues. Often precedes or accompanies an FAA Airworthiness Directive.

NASA-administered confidential reporting system where pilots, mechanics, and others report safety hazards without FAA enforcement action.

Now Airlines for America (A4A). Originally published the ATA 100 specification that became the universal aircraft documentation numbering system.

ATA 100 specification divides aircraft systems into numbered chapters (e.g., ATA 27 = Flight Controls, ATA 71 = Power Plant). Used universally for aircraft documentation.

List of suppliers pre-qualified by an airline or MRO to provide parts or services. Parts from non-AVL suppliers require additional vetting.

Non-mandatory safety communication issued by an authority or OEM recommending inspection or modification. Compliance is advisory unless referenced by an AD.

Mandatory life limits or maintenance requirements for structural or safety-critical parts, defined in the Instructions for Continued Airworthiness (ICA).

Assessment that the cost to repair a component exceeds its replacement value. BER parts are typically scrapped or sold for test/training.

Equipment purchased by the airline (buyer) and supplied to the airframer for installation. Common for in-flight entertainment and cabin systems.

Document issued by a national aviation authority confirming an aircraft meets airworthiness standards and is approved for flight.

Generic term for a national aviation regulatory body. Used specifically for the UK CAA (post-Brexit, separate from EASA).

5-character code assigned to manufacturers, suppliers, and government entities in the U.S. and NATO countries. Required for DoD contracts.

EASA-approved organization responsible for managing the continuing airworthiness of aircraft on behalf of the registered owner or operator.

FAA-approved maintenance program for Part 135 operators ensuring aircraft remain airworthy between scheduled inspections.

Document specifying which external parts (fairings, panels) may be missing for dispatch, with associated performance penalties.

GE/Safran joint venture producing CFM56 and LEAP turbofan engines — the most widely used commercial jet engines in the world.

The codification of all U.S. federal rules. Aviation regulations appear in 14 CFR (Title 14 — Aeronautics and Space).

OEM manual providing maintenance, overhaul, testing, and repair procedures for a specific aircraft component or LRU.

Mandatory maintenance task identified during aircraft certification to ensure continued airworthiness of safety-critical items.

Supplier document certifying that delivered parts meet the purchase order specifications, applicable standards, and airworthiness requirements.

Number of pressurization cycles accumulated on a component since manufacture. Critical life-limiting metric for turbine engine parts and pressure vessel structure.

FAA-designated individual authorized to issue airworthiness certificates and export certificates on behalf of the FAA.

Seller bears all costs and risk of delivery, including import duties. Used when the seller handles customs clearance.

Process of rendering military parts unusable for their original purpose before disposal. DEMIL code determines whether a part can be sold commercially after military surplus.

FAA-designated individual authorized to approve technical data on behalf of the FAA, including repairs, alterations, and design approvals.

U.S. DoD agency that manages supply chain for military services. Assigns NSNs, maintains the WebFLIS parts database, and contracts for aviation spare parts.

Radio navigation system providing slant-range distance from a ground station. Used with VOR for position fixing and approach procedures.

DoD term for the problem of obsolete parts whose original manufacturers have stopped production. Common in long-lived military aircraft.

FAA's online database of regulatory documents including all PMA approvals, STCs, TCs, and ADs. Publicly accessible at drs.faa.gov.

EU regulatory authority for civil aviation safety, equivalent to the FAA. Issues its own ADs, Part-21 approvals, and airworthiness standards.

EASA equivalent of FAA Form 8130-3. Certifies a part or maintenance action meets EASA Part-145 airworthiness standards.

Advanced terrain warning system using GPS and a global terrain database to provide look-ahead terrain alerts. Also called TAWS (Terrain Awareness and Warning System).

Key engine health parameter measured at the turbine. Elevated EGT margins indicate engine degradation and approaching maintenance action.

Military airworthiness standards developed by European Defence Agency nations, parallel to EASA standards for military aircraft.

Expected delivery date for a part shipment. Critical information in AOG situations where hours matter.

Authorization allowing twin-engine aircraft to fly routes where a diversion airport is more than 60 minutes away. Requires specific maintenance and parts standards.

All wiring, connectors, and terminations on an aircraft. Post-TWA 800, FAA mandated specific EWIS inspection and maintenance requirements.

U.S. government agency responsible for regulating civil aviation. Issues ADs, type certificates, PMAs, STCs, and repair station certifications.

Comprehensive inspection of the first production unit to verify it conforms to design specifications. Required before production quantities are delivered.

U.S. regulations governing all aviation activities, codified in 14 CFR. FAR Part 145 covers repair stations; Part 21 covers certification.

Shipping term where seller delivers goods to a named carrier at seller's location. Risk transfers to buyer at that point. Common in aerospace parts trade.

Airline-specific operations manual derived from the AFM plus airline procedures. Used by flight crew, not maintainers.

Systematic analysis of aircraft functions to identify and classify potential failure conditions by severity. Foundation of the aviation safety case.

Manual providing systematic procedures to identify the root cause of system faults, often referencing specific test equipment.

Engineering analysis identifying all ways a component can fail and the effect of each failure on the system. Required for certified aircraft systems.

FMEA extended with criticality ranking to prioritize failure modes by severity and probability. Used to set maintenance task intervals.

Integrated avionics computer managing navigation, flight planning, and performance optimization. Central to RNAV and RNP operations.

First 4 digits of an NSN, grouping items by type. Aviation-relevant classes include 1510 (aircraft), 1560 (airframe structural components), 1610 (aircraft propellers), 2840 (gas turbine engines).

U.S. trade association representing manufacturers of general aviation aircraft, engines, avionics, and parts.

Equipment provided by a government entity to a contractor for installation in a military aircraft or system.

System alerting crew to dangerous proximity to terrain. Superseded by EGPWS (Enhanced) which adds terrain database look-ahead.

Parts excess to government needs, sold through DLA Disposition Services. May include aircraft components — airworthiness status varies widely and requires verification.

Scheduled maintenance event triggered by calendar time or flight hours/cycles, regardless of component condition.

Section of a turbofan engine that compresses air before combustion. HPC blades and vanes are LLPs and are closely tracked for cycle accumulation.

First turbine stage after combustion. Highest temperature and stress components in the engine. HPT blades are LLPs subject to strict cycle limits.

Trade association of world airlines. Sets standards for ground handling, e-ticketing, cargo labeling (IATA hazmat), and MRO coding systems.

FAA-required documentation from the type certificate holder specifying maintenance, inspection, and overhaul requirements for the aircraft's lifetime.

UN agency that sets global civil aviation standards and practices. Member states implement ICAO standards through their national regulations.

Radio navigation system providing precision guidance (localizer + glideslope) for instrument approaches. Required for CAT II/III low-visibility operations.

OEM-published catalog with exploded diagrams and part numbers for all aircraft components. The authoritative source for part number lookup and interchangeability.

Engine or rotor component with a mandatory retirement life expressed in flight cycles. LLPs cannot be repaired beyond their cycle limit — they are scrapped.

A component designed to be removed and replaced at the flight line (without depot maintenance). Examples: avionics boxes, actuators, sensors.

FAA-approved document listing equipment that may be inoperative while still allowing dispatch. Derived from the MMEL issued by the aircraft manufacturer.

U.S. DoD specification defining performance and quality requirements for materials and parts used in military applications. Many MIL-SPEC parts are used in both military and civilian aircraft.

FAA-issued baseline from which operators develop their operator-specific MEL. Defines what can be deferred and for how long.

OEM-issued document listing all required and recommended maintenance tasks with intervals. Airlines use the MPD to build their approved maintenance programs.

The part number assigned by the OEM. Also written as P/N. May differ from the NSN or cage-code-based identifiers used in procurement.

The industry sector that maintains, inspects, repairs, and overhauls aircraft, engines, and components. MROs range from airline internal shops to independent certified repair stations.

Industry-developed methodology for creating aircraft maintenance programs based on reliability-centered maintenance principles. Used for all modern commercial aircraft.

Industry-managed accreditation program for special processes (heat treating, NDT, plating, welding) in the aerospace supply chain.

Synonym for NDT in the aviation context. Used in AMM procedures to specify inspection methods for structural checks.

Inspection methods that evaluate material integrity without damaging the part. Common methods: eddy current, ultrasonic, X-ray, dye penetrant, magnetic particle.

The last 9 digits of an NSN (after the FSC). Uniquely identifies an item within the NATO supply system.

13-digit NATO standardization number identifying a specific item of supply. Format: XXXX-XX-XXX-XXXX (FSC-CC-NIIN). Used extensively in military and government procurement.

Independent U.S. agency investigating civil aviation accidents and incidents. NTSB findings frequently drive FAA regulatory action.

Maintenance practice where a component is maintained based on monitored performance or inspection results, not fixed time intervals.

FAA program allowing large organizations to perform certain certification functions (e.g., type design approval, conformity inspections) under FAA oversight.

The manufacturer that produced the original certified part. OEM parts are purchased directly from the company that holds the design approval.

Standard commercial part (fasteners, tubing, filters) available from general suppliers, not requiring OEM-specific sourcing.

Alphanumeric identifier assigned by a manufacturer to a specific part. Not globally unique — the same P/N can be used by different manufacturers.

FAA approval authorizing production and sale of aircraft replacement parts. PMA parts are FAA-certified alternatives to OEM parts.

Formal document committing to purchase specific parts at agreed price and delivery terms. Triggers legal obligations on both buyer and seller.

EASA approval for organizations manufacturing aircraft parts and products, equivalent to FAA Production Approval Holder (PAH).

FAA certification standard for repair stations. Part 145 certification is required to return aircraft and components to service for U.S.-registered aircraft.

Systematic processes ensuring products and services meet specified requirements. In aviation, QA includes traceability, documentation control, and supplier oversight.

A pre-assembled engine module with its accessories (nacelle, mounts, harnesses) ready for rapid installation to minimize AOG time.

Formal process to identify why a defect or escape occurred and implement permanent fixes. Required by AS9100 when nonconformances are found.

Formal document sent to suppliers soliciting pricing and availability for specific parts. Standard procurement step before a purchase order.

The act of certifying and documenting that maintenance has been performed correctly and an aircraft or component is airworthy.

Unique identifier assigned to a specific manufactured unit of a part, traceable through its entire service life.

Standards body that publishes widely used aerospace standards including AS9100 (quality management) and thousands of material and process specifications.

OEM-issued instructions for inspections, modifications, or repairs. May be mandatory (if referenced by an AD) or optional. Critical for tracking component configuration.

FAA database report filed when a component fails or exhibits a defect in service. SDRs are a key source of field reliability data and can trigger ADs.

OEM-published manual with approved methods for inspecting and repairing aircraft structural components without requiring an STC.

A subcomponent of an LRU that is replaced during bench maintenance at an overhaul shop, not at the line.

FAA approval for a modification to a type-certificated aircraft, engine, or propeller. The STC holder owns the design approval and installation data.

Parts whose airworthiness approval documentation cannot be verified. FAA issues SUP notifications when bogus parts enter the supply chain. Major safety and liability risk.

Time from receipt of a part or aircraft at a shop to return of the serviceable item. Key KPI in MRO contracting.

Manufacturer-specified interval for engine or component overhaul. Expressed in flight hours, cycles, or calendar time. Determines shop visit frequency.

FAA document certifying that an aircraft design meets airworthiness standards. All production variants must conform to the TC.

Airborne system that monitors transponder signals from other aircraft and issues Resolution Advisories (RAs) to avoid collisions. Mandated on commercial aircraft.

Canadian aviation safety authority, equivalent to the FAA. Issues Canadian Airworthiness Directives (CADs).

FAA document listing the specifications, limitations, and approved configurations for a type-certificated product. Publicly available on the FAA website.

Hours or cycles accumulated on a component since its most recent overhaul. Used to determine remaining life until next shop visit.

OEM guide for diagnosing and isolating faults in aircraft systems, cross-referenced to AMM procedures.

Total flight hours accumulated since manufacture. Used with CSN to determine airworthiness and remaining useful life.

FAA minimum performance standard for specified articles (e.g., avionics, life vests). TSO authorization allows manufacture and installation.

FAA formal finding that a part lacks the required airworthiness approval. UPD parts must be removed from service.

Parts removed from aircraft that have been inspected and certified as airworthy for reinstallation. Also called serviceable used parts.

Radio frequency band (30–300 MHz) used for aircraft communications and VOR navigation. Standard comms radio for civil aviation worldwide.

OEM manual containing complete electrical wiring schematics for an aircraft. Critical for avionics troubleshooting and modification work.