2.3 Required Aircraft Inspections & Maintenance Records

Required Aircraft Inspections & Maintenance Records

Airworthiness is not an assumption—it is a verifiable legal status documented in the aircraft maintenance logbooks. Under 14 CFR § 91.403 and § 91.405, the owner or operator is primarily responsible for maintaining the aircraft in an airworthy condition, but the Pilot-in-Command (PIC) is solely responsible for determining whether the aircraft is in condition for safe flight prior to each departure (14 CFR § 91.7).

To conduct an IFR flight in controlled airspace, the pilot must review the aircraft records to confirm compliance with all mandatory periodic inspections.

---

1. The AVIATES Maintenance Framework

The standard aviation mnemonic AVIATES captures the mandatory periodic inspection cycles required for IFR flight:

+-----------------------------------------------------------------------------+
|                        AVIATES INSPECTION FRAMEWORK                         |
|                                                                             |
|   [A] Airworthiness Directives (ADs) ---> 14 CFR Part 39 (One-time/Recurring)|
|   [V] VOR Equipment Check           ---> 14 CFR 91.171 (Preceding 30 Days)  |
|   [I] Inspections (Annual / 100-Hr) ---> 14 CFR 91.409 (12 Cal Mos / 100 Hr)|
|   [A] Altimeter & Pitot-Static      ---> 14 CFR 91.411 (24 Cal Mos for IFR) |
|   [T] Transponder Check             ---> 14 CFR 91.413 (24 Cal Mos)         |
|   [E] Emergency Locator Transmitter ---> 14 CFR 91.207 (12 Cal Mos / Batt)  |
|   [S] Supplemental / Static System  ---> Part 23 / ICA Life Limits          |
+-----------------------------------------------------------------------------+

---

2. Airworthiness Directives (14 CFR Part 39)

Airworthiness Directives (ADs) are legally enforceable federal regulations issued by the FAA under 14 CFR Part 39 to correct an unsafe condition found in an aircraft, engine, propeller, or appliance.

Types of ADs

1. One-Time ADs: Require a single specific modification, inspection, or part replacement. Once completed, no further action is required unless specified.
2. Recurring ADs: Require repetitive inspections or maintenance actions at fixed intervals (e.g., every 50 hours of time-in-service, every 100 hours, or every 12 calendar months).
3. Emergency ADs: Issued immediately when an urgent safety hazard requires immediate grounding or inspection prior to further flight.

Service Bulletins (SBs) vs. ADs

• Service Bulletins (SBs): Issued by aircraft or component manufacturers. SBs are advisory recommendations for Part 91 general aviation operators and are not mandatory unless explicitly incorporated by reference into an FAA Airworthiness Directive.

---

3. Annual and 100-Hour Inspections (14 CFR 91.409)

Federal aviation regulations establish two distinct airframe and powerplant inspection cycles based on operational use.

The Annual Inspection (14 CFR 91.409(a))

• Scope: Required for all civil aircraft operated under Part 91.
• Interval: Every 12 calendar months, expiring on the last day of the 12th calendar month following the month of the previous inspection.
  • Calculation Example: If an annual inspection is signed off on May 12, 2025, it remains valid through May 31, 2026.
• Sign-off Authority: Must be performed and approved for return to service by an Airframe & Powerplant (A&P) mechanic holding an Inspection Authorization (IA), an approved Part 145 repair station, or the aircraft manufacturer.

The 100-Hour Inspection (14 CFR 91.409(b))

• Scope: Required for aircraft operated for hire, carrying passengers for hire, or provided by a flight instructor for hire in flight training.
• Interval: Every 100 hours of time-in-service.
• Sign-off Authority: Can be performed and returned to service by any certificated A&P mechanic (IA is not required).

The 10-Hour Overfly Rule (91.409(b))

• The 100-hour limit may be exceeded by a maximum of 10 hours solely for the purpose of flying the aircraft to a location where the inspection can be performed.
• Mandatory Subtraction: Any excess time used must be subtracted from the next 100-hour interval.
  • Example: If a 100-hour inspection was due at 1,200.0 hours tachometer time, and the aircraft is flown to 1,208.0 hours to reach the maintenance base, the inspection is performed at 1,208.0 hours. The subsequent 100-hour inspection is due at 1,300.0 hours (1,200 + 100), NOT 1,308.0 hours.

Substitution Relationship

• An Annual inspection can substitute for a 100-hour inspection.
• A 100-hour inspection can NEVER substitute for an Annual inspection.

---

4. Altimeter & Pitot-Static System (14 CFR 91.411)

Under 14 CFR § 91.411, specialized testing of the barometric pressure system is mandated for instrument flight:

• Requirement: No person may operate an airplane in controlled airspace under IFR unless within the preceding 24 calendar months, each static pressure system, each altimeter instrument, and each automatic pressure altitude reporting system (altitude encoder / blind encoder) has been tested and inspected in accordance with 14 CFR Part 43, Appendix E.
• Scope: Applies to any IFR operation in controlled airspace, even if flying in visual meteorological conditions (VMC).
• Expiration: Valid until the last day of the 24th calendar month.
  • Example: Tested on August 15, 2024 $\rightarrow$ Valid through August 31, 2026.

---

5. ATC Transponder Inspection (14 CFR 91.413)

Under 14 CFR § 91.413, any transponder operated in civil aircraft must be inspected:

• Requirement: Tested and inspected within the preceding 24 calendar months in accordance with 14 CFR Part 43, Appendix F.
• Scope: Applies to all aircraft operating in airspace where a transponder is required by 14 CFR 91.215 (Class A, Class B, Class C, within 30 NM Mode C Veil, and above 10,000 feet MSL).
• Authorization: Must be conducted by an authorized Part 145 repair station, avionics technician, or manufacturer.

---

6. Emergency Locator Transmitter (14 CFR 91.207)

Under 14 CFR § 91.207, the Emergency Locator Transmitter (ELT) is subject to both calendar inspection and battery replacement rules:

Annual ELT Inspection (91.207(d))

• Inspected every 12 calendar months for:
  • Proper installation and antenna integrity
  • Battery corrosion
  • Operation of the crash-impact inertial switch (G-switch)
  • Sufficient radiated RF signal from its antenna

ELT Battery Replacement / Recharge (91.207(c))

ELT batteries must be replaced (or recharged, if rechargeable) when:

1. The transmitter has been in use for more than 1 cumulative hour of operating time; OR
2. 50% of the battery's useful life (or useful charge) has expired, as established by the manufacturer and stamped on the exterior of the battery casing.

[!TIP] ELT Operational Testing Rules: Airborne or ground operational testing of 121.5 MHz analog ELTs must only be conducted during the first 5 minutes past any hour, and is restricted to no more than 3 audio sweeps. Digital 406 MHz ELTs contain internal self-test circuits and should never be triggered over the air without following manufacturer self-test button sequences.

---

7. Comprehensive Inspection Summary Table