General aviation maintenance has a language of its own. This glossary explains the terms in plain English so owner-operators can read a logbook, talk to an A&P with confidence, and understand what TachMinder is tracking. Definitions are educational summaries — always confirm specifics with a certificated mechanic and current FAA regulations.
- 100-Hour Inspection
- An inspection identical in scope to an annual inspection, required for aircraft that carry passengers for hire or are used for flight instruction for hire. It is due every 100 hours of time in service. Purely private, non-commercial Part 91 operations generally do not require it (see 14 CFR 91.409).
- Related reading: How to Prepare for Your Annual Inspection →
- A&P Mechanic (Airframe and Powerplant)
- A mechanic certificated by the FAA to perform and approve maintenance on aircraft airframes and engines. An A&P can return most maintenance to service, but an annual inspection must be signed off by an A&P who also holds an Inspection Authorization (IA).
- AD (Airworthiness Directive)
- A legally enforceable rule issued by the FAA to correct an unsafe condition found in an aircraft, engine, propeller, or appliance. Compliance is mandatory, not optional. ADs may require a one-time action or repeated, recurring action.
- Related reading: Understanding Airworthiness Directives →
- Airframe
- The structure of the aircraft — fuselage, wings, empennage, and landing gear, with their associated components — excluding the engine and propeller.
- Airworthy / Airworthiness
- An aircraft is airworthy when it conforms to its type certificate (and any approved alterations) and is in condition for safe operation. An aircraft with an overdue AD or a lapsed required inspection is not airworthy.
- Altimeter & Static System Check
- A required test of the altimeter and static pressure system for aircraft flown under instrument flight rules (IFR). It is generally required every 24 calendar months (see 14 CFR 91.411).
- Annual Inspection
- A complete inspection of the aircraft required every 12 calendar months for most Part 91 aircraft. It must be performed and signed off by an A&P mechanic who holds an Inspection Authorization (IA) (see 14 CFR 91.409).
- Related reading: How to Prepare for Your Annual Inspection →
- Calendar Time
- A maintenance interval measured in elapsed calendar months or years, regardless of how much the aircraft is flown. Many inspections and some ADs run on calendar time rather than hours.
- Compression Test (Differential Compression)
- A test of how well each engine cylinder holds pressure, used to gauge the condition of the cylinders, piston rings, and valves. It is commonly performed during an annual inspection.
- Cycle
- One complete takeoff and landing. Some maintenance items and ADs are measured in cycles rather than hours, because each cycle imposes a distinct load on the airframe or engine.
- ELT (Emergency Locator Transmitter)
- A battery-powered transmitter that broadcasts a distress signal to aid search and rescue after an accident. ELTs are subject to required inspections and to battery replacement on a defined schedule (see 14 CFR 91.207).
- Hard Time
- A maintenance approach in which a component is overhauled or replaced at a fixed interval regardless of its apparent condition. It contrasts with on-condition maintenance.
- Hobbs Time
- Elapsed clock time recorded by a Hobbs meter, which runs at a constant rate whenever the engine is running (or the master switch is on, depending on the aircraft). One Hobbs hour equals one real hour. It is often used for rental billing and flight-time logging.
- IA (Inspection Authorization)
- An additional authorization held by an experienced A&P mechanic that allows them to perform annual inspections and to approve major repairs and major alterations.
- Logbook (Maintenance Logbook)
- The official record of an aircraft's maintenance history. Separate logbooks are typically kept for the airframe, engine, and propeller. Required maintenance, inspections, and AD compliance are all recorded here.
- Related reading: Why GA Pilots Need Digital Maintenance Tracking →
- Major Alteration
- A change to an aircraft, engine, or propeller — not listed in the type specifications — that may appreciably affect weight, balance, structural strength, performance, or other qualities affecting airworthiness. It must be documented (often on FAA Form 337) and approved appropriately.
- Major Repair
- A repair that, if done improperly, might appreciably affect airworthiness, or that is not done by elementary operations. Like major alterations, major repairs require specific documentation and approval.
- Oil Analysis (Spectrometric)
- A laboratory test that measures the parts-per-million of various metals — iron, copper, chromium, and others — in a used-oil sample. Tracked as a trend across multiple samples, it can reveal developing engine wear before it becomes a failure.
- On-Condition
- A maintenance approach in which a component stays in service as long as inspections and tests show it still meets condition standards, rather than being replaced at a fixed hour limit.
- Overhaul
- The process of disassembling a component (most often an engine), inspecting it, repairing or replacing parts as needed, and reassembling it to defined standards. An overhaul restores much of the component's service life.
- Owner-Performed Preventive Maintenance
- A limited list of simple tasks that a certificated pilot who owns or operates the aircraft may perform on an aircraft not used in commercial operations, and then record in the logbook. The list is defined in 14 CFR Part 43, Appendix A.
- Part 91
- The section of the Federal Aviation Regulations covering general operating and flight rules for general aviation, including most private, non-commercial flying. TachMinder is built specifically for Part 91 owner-operators.
- Pitot-Static System
- The system of ports and plumbing that supplies ram air and static pressure to the airspeed indicator, altimeter, and vertical speed indicator. It is tested as part of the IFR static-system check.
- Powerplant
- The aircraft engine and its directly associated components — the P in A&P.
- Pre-Buy Inspection
- A voluntary inspection of an aircraft commissioned by a prospective buyer to assess its condition, logbook completeness, and AD compliance before purchase. It is not a regulatory requirement, but it is strongly recommended.
- Preventive Maintenance
- Simple or minor preservation operations and the replacement of small standard parts not involving complex assembly operations. It is a defined subset of maintenance, some of which qualifying pilot-owners may perform themselves.
- Propeller
- The rotating airfoil that converts engine power into thrust. A propeller has its own logbook, its own ADs, and its own overhaul interval.
- Recurring AD
- An Airworthiness Directive that requires repeated action — such as a repeated inspection — at specified intervals, rather than a single one-time fix. Recurring ADs need ongoing tracking.
- Related reading: Understanding Airworthiness Directives →
- Return to Service
- The act of a certificated mechanic, or other appropriately rated person, approving an aircraft as airworthy after maintenance, inspection, or alteration by making the required logbook entry. Only certificated personnel can return an aircraft to service.
- Service Bulletin (SB)
- A notice issued by a manufacturer recommending an inspection, modification, or part change. Service bulletins are generally advisory for Part 91 operators unless they are made mandatory by an AD.
- Squawk
- Pilot and mechanic shorthand for a noted defect, discrepancy, or item needing attention on an aircraft — for example, a flickering light or a rough-running magneto.
- STC (Supplemental Type Certificate)
- An FAA approval for a major modification or alteration to a type-certificated product. An STC documents that the change has been shown to meet airworthiness standards.
- Tach Time (Tachometer Time)
- Engine time recorded by a tachometer, which advances at a rate proportional to engine RPM. At cruise RPM it roughly tracks real time; at low RPM, such as taxi and runup, it runs slower. It is commonly used for engine maintenance intervals and TBO.
- TBO (Time Between Overhaul)
- The manufacturer's recommended operating time, usually expressed in tach hours, before an engine or propeller is recommended for overhaul. For Part 91 operators, TBO is a recommendation, not a mandatory limit — condition matters more than the raw hour count.
- TCDS (Type Certificate Data Sheet)
- An FAA document that defines the approved configuration and limitations of a type-certificated aircraft, engine, or propeller. It helps identify exactly which type certificate a component falls under, which in turn determines which ADs apply.
- Time in Service
- The time from the moment an aircraft leaves the ground until it touches down. It is the reference used for many inspection and maintenance intervals.
- Transponder Check
- A required test of the aircraft's transponder system, generally required every 24 calendar months for the transponder to be used (see 14 CFR 91.413).
Aviation Disclaimer
TachMinder is an informational tool only. It is not a substitute for a certified A&P mechanic or IA. Only certificated mechanics and appropriately rated repair stations can approve return-to-service. Always verify Airworthiness Directive data with the FAA AD database (drs.faa.gov). TachMinder does not certify airworthiness.