Annual / 100-Hour Inspections

Annual Inspection is a requirement under FAR’s 91.409 to assure the airworthiness of an aircraft. A detailed aircraft annual assures that the plane is inspected and all discrepancies are noted and subsequently corrected. At the minimum, our compliance is to FARs 43 Appendix D plus all other mandatory manufacturer requirements.

The following article is from AOPA that should concern all aircraft owners:

Guide to Aircraft Airworthiness:

Importance to Members

14 CFR 91.7 prohibits any person from operating an aircraft that is not in an airworthy condition. What exactly is airworthiness of an aircraft that is flyable and is not necessarily airworthy. Many aircraft owners might be surprised to find that there are multiple violations for flying an aircraft that is not airworthy.

FAR 3:5(a) Statements about products, parts, appliances and materials provides a definition of “airworthy” as follows: (a) Definitions. The following terms will have the stated meanings when used in this section: Airworthy means the aircraft conforms to its type design and is in a condition for safe operation. With this definition in mind, it is important to understand who is responsible for determining the airworthiness of the aircraft prior to flight. This subject report will discuss this and other information relating to aircraft airworthiness.


The FAA is very clear in its intent that only airworthy aircraft should be operated. The regulation places responsibility on the pilot in command by stating, “The pilot in command of a civil aircraft is responsible for determining whether that aircraft is in condition for safe flight. The pilot in command shall discontinue the flight when unairworthy mechanical, electrical, or structural conditions occur.”

It is important to note that the responsibility for determining airworthiness does not stop here. 14 CFR 91.407 places additional responsibility on the operator by stating, “No person may operate an aircraft that has undergone maintenance, preventative maintenance, rebuilding, or alteration unless: (1) It has been approved for return to service by a person authorized under 43.7 of this chapter; and (2) The maintenance record entry required by 43.9 or 43.11 , as applicable, of this chapter has been made.” Most owners and operators rely on maintenance facilities to perform required inspections and repairs along with ensuring all airworthiness directives, maintenance, and inspections are logged and signed off properly. Many owners and operators do not check for proper endorsements, which approve the aircraft for return to service and state that the aircraft is airworthy if a 100-hour or annual inspection was performed.

The condition of the aircraft is important but not the only factor in determining airworthiness. If you are an aircraft owner or operator, remember to review the logbooks after the aircraft is returned from maintenance. Ensure that the proper inspections, repairs, and airworthiness directives are completed and logged, and the logbooks contain a statement approving the aircraft for return to service.

Technical Information

Regulatory Requirements

FAR 91.7(a) requires that, “no person may operate a civil aircraft unless it is in an airworthy condition.” Subsection (b) of the same section provides that the pilot in command [PIC] of an aircraft is responsible for determining that the aircraft is in a condition for safe flight, and that the PIC must discontinue the flight when the aircraft encounters unairworthy mechanical, electrical, or structural conditions. FAR 3:5(a) Statements about products, parts, appliances and materials provides a definition of “airworthy” as meaning the aircraft conforms to its type design and is in a condition for safe operation.

What is conformity to type certificate? The FAA’s attitude has been that an aircraft must be in just about factory-new condition (if it was factory built), plus the alterations must be in the same condition as that when completed in accordance with a supplemental type certificate (if the craft was altered), plus the aircraft must be in compliance with any applicable airworthiness directives.

It is often debated whether the guidance offered to pilots in FAA publications such as the Aeronautical Information Manual (AIM) should be considered regulatory. That is, do you need to know and follow these publications just as you are required to know and comply with the federal aviation regulations? A good means to end this debate is an FAA issued description of the scope of the AIM, and other such publications. “This publication, while not regulatory, provides information which reflects examples of operating techniques and procedures which may be requirements in other federal publications or regulations. It is made available solely to assist pilots in executing their responsibilities required by other publications.” Such a statement expresses that although they should be taken as guidance and not requirements, a competent pilot in command would adhere the guidance recommended in the AIM.

Inspection Requirements

Under FAR 91.409(a), an aircraft must undergo an annual inspection every 12 calendar months to be legal to operate. If an aircraft is used to carry passengers or is operated for hire (as in flight instruction), it also must have either an annual or 100-hour inspection within the preceding 100 hours of time in service. It’s important to remember that while an annual can serve as a 100-hour inspection, a 100-hour inspection will not substitute for an annual. Remember that for an annual, the period of 12 calendar months extends from any day of any month to the last day of the same month in the following year.

Other inspections are required for the instruments and equipment installed in the aircraft. However, some of these inspections are only required if the aircraft is operated under instrument flight rules. For example, another inspection you should be aware of is the altimeter system and altitude reporting system test and inspection. This inspection, described in FAR 91.411(a), is required if the aircraft is operated in controlled airspace under IFR. It mandates that within the preceding 24 calendar months, each static pressure system, each altimeter instrument, and each automatic pressure altitude reporting system must have been tested and inspected and found to comply with appendix E of Part 43. Automatic pressure altitude reporting system is just a fancy name for the mode c transponders altitude encoder.

An example of an equipment inspection you should be aware of is the emergency locator transmitter (ELT) entry required by FAR 91.207. This regulation says that the ELT must have been inspected within 12 calendar months after the last inspection. The ELT is checked for proper installation, signs of any battery corrosion, the operation of the controls and crash sensor, and the presence of a sufficient signal radiated from its antenna.

Finally, in order to operate under IFR using the VOR system of radio navigation, the VOR equipment of that aircraft has to have been operationally checked within the past 30 days in accordance with FAR 91.171.

In conclusion in order to be legal and safe to fly, an aircraft must have a current annual, a 100-hour inspection if used to carry passengers or operated for hire, and all applicable ADs must have been complied with. Depending on how the aircraft is operated, it should also have static system and altimeter, transponder, ELT, and VOR equipment checks.

Progressive/Phase inspection: If the airplane is utilized quite extensively during each year, owners may consider Progressive inspection program for their Airplane that minimizes the maintenance down time with the same end results. The progressive inspection can be custom designed or factory recommended inspection program, however either one should be approved and stamped for the desired aircraft by the FAA prior commencing the Progressive inspection program. Obviously FAA office would accept, expedite and approve the program from the factory since all the mandatory inspection is included in their checklist.

How do you know if you should pick the progressive inspection program? If the plane is used for business travel and you can’t afford lengthy down time of the annual inspections and you fly in excess of 200 hours a year, then this is the right program for you.

These are the steps that starts the progressive inspection:

  1. As I mentioned earlier, letter of intent along with the inspection proposal must be submitted to the FAA….
  2. Upon FAA approval of the inspection program a complete annual inspection must be performed to the aircraft for the progressive cycle to start…
  3. Typically every 50 hours, airplane is brought in for each phase or event of progressive inspection. During each phase/event, one section of the aircraft is inspected in detail and other section gets only a routine inspection and visa versa at the next 50 hours the area that was routinely inspected will get a detail inspection and so on…..
  4. Progressive inspections are designed that the entire aircraft is inspected during each calendar year incrementally. If for any reasons the inspection cycle is not completed within 12 calendar month, then prior to the end of 12 calendar month, the remaining inspection requirement must be completed all at the same time in order to continue progressive program the following year.