Select scope (private pilot is the default): Instrument Rating Related Commercial Rating Related Instructor Rating Related

Defining Airworthiness:

  • Two main factors determine if an aircraft is airworthy:
    • The aircraft conforms to its type certificate and authorized modifications; and
    • The aircraft must be in condition for safe operation

Determining Airworthiness:

  • 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 un-airworthy mechanical, electrical, or structural conditions occur
  • Likewise, the remote pilot-in-command is responsible for the determination of airworthiness before flight and to discontinue the flight when he or she knows or has reason to know that the small unmanned aircraft system is no longer in a condition for safe operation
  • No person may operate any aircraft that has undergone maintenance, preventive maintenance, rebuilding, or alteration unless:
    • It has been approved for return to service by a person authorized under Sec. 43.7 of this chapter; and
    • The maintenance record entry required by Sec. 43.9 or Sec. 43.11, as applicable, has been made
  • No person may carry any person (other than crewmembers) in an aircraft that has been maintained, rebuilt, or altered in a manner that may have appreciably changed its flight characteristics or substantially affected its operation in flight until an appropriately rated pilot with at least a private pilot certificate flies the aircraft, makes an operational check of the maintenance performed or alteration made, and logs the flight in the aircraft records
    • The requirement for an in-flight operational check may be waived if, prior to flight, ground tests, inspection, or both show conclusively that the maintenance, preventive maintenance, rebuilding, or alteration has not appreciably changed the flight characteristics or substantially affected the flight operation of the aircraft
  • Aircraft must conform to the Type Certificate Data Sheet (TCDS)
  • Failing the ability to conform to the TCDS, pilots may utilize minimum equipment lists or kinds of equipment lists, as applicable

Minimum Equipment Lists (MEL) and Operations With Inoperative Equipment:

  • Minimum Equipment List
    Minimum Equipment List
  • The MEL is the specific inoperative equipment document for a particular make and model aircraft by serial and registration numbers; e.g., BE-200, N12345
    • A FAR Part 91 MEL consists of the MMEL for a particular type aircraft, the MMEL's preamble, the procedures document, and a LOA
  • Under 14 CFR, all aircraft instruments and installed equipment are required to be operative prior to each departure
  • Recognizing that safe clight can be conducted under specific conditions with inoperative instruments and equipment, the FAA adopted the minimum equipment list
    • When the FAA adopted the minimum equipment list (MEL) concept for 14 CFR part 91 operations, it allowed aircraft to be operated with inoperative equipment determined to be nonessential for safe flight
    • At the same time, it allowed part 91 operators, without an MEL, to defer repairs on nonessential equipment within the guidelines of part 91
  • The FAA has two acceptable methods of deferring maintenance on small rotorcraft, non-turbine powered airplanes, gliders, or lighter-than-air aircraft operated under part 91:
    • The deferral provision of 14 CFR, part 91, section 91.213(d), and
    • An FAA-approved MEL
  • Inoperative Equipment Deferral:

    • The deferral provision of 14 CFR, part 91, section 91.213(d) is simple, requiring minimal paperwork
    • When inoperative equipment is found during a preflight inspection or prior to departure, the decision should be to cancel the flight, obtain maintenance prior to flight, or to defer the item or equipment
    • Maintenance deferrals are not used for inflight discrepancies
      • The manufacturer's AFM/POH procedures are to be used in those situations
    • Assuming the pilot wishes to defer maintenance for equipment that would ordinarily be required prior to flight:
      • The pilot first determines whether the inoperative equipment is required by type design, 14 CFR, or ADs
      • If the inoperative item is not required, and the aircraft can be safely operated without it, the deferral may be made
      • The inoperative item shall be deactivated or removed and an INOPERATIVE placard placed near the appropriate switch, control, or indicator
        • If deactivation or removal involves maintenance (removal always will), it must be accomplished by certificated maintenance personnel and recorded in accordance with 14 CFR part 43
          • For example, if the position lights (installed equipment) were discovered to be inoperative prior to a daytime flight, the pilot would follow the requirements of 14 CFR, part 91, section 91.213(d)
        • The deactivation may be a process as simple as the pilot positioning a circuit breaker to the OFF position or as complex as rendering instruments or equipment totally inoperable
        • Complex maintenance tasks require a certificated and appropriately rated maintenance person to perform the deactivation
    • While deferrals may be necessary, the FAA regulation division's interpretation is clear, that inoperative equipment shall not stay so indefinitely
  • Minimum Equipment List:

    • Once an operator requests an MEL, and a Letter of Authorization (LOA) is issued by the FAA, then the use of the MEL becomes mandatory for that aircraft
      • All maintenance deferrals must be accomplished in accordance with the terms and conditions of the MEL and the operator-generated procedures document
    • The use of an MEL for an aircraft operated under 14 CFR part 91 also allows for the deferral of inoperative items or equipment
      • The primary guidance becomes the FAA-approved MEL issued to that specific operator and N-numbered aircraft
      • The FAA has developed Master Minimum Equipment Lists (MMELs) for aircraft in current use
      • Upon written request by an operator, the local Flight Standards District Office may issue the appropriate make and model MMEL, along with a Letter of Authorization, and preamble
      • The operator then develops operations and maintenance (O&M) procedures from the MMEL. This MMEL with O&M procedures now becomes the operator's MEL
      • The MEL, LOA, preamble, and procedures document developed by the operator must be on board the aircraft during each operation
      • The FAA considers an approved MEL to be a supplemental type certificate (STC) issued to an aircraft by serial number and registration number
      • It, therefore, becomes the authority to operate that aircraft in a condition other than originally type certificated
    • With an approved MEL, if the position lights were discovered inoperative prior to a daytime flight, the pilot would make an entry in the maintenance record or discrepancy record provided for that purpose
      • The item would then either be repaired or deferred in accordance with the MEL
      • Upon confirming that daytime flight with inoperative position lights is acceptable in accordance with the provisions of the MEL, the pilot would leave the position lights switch OFF, open the circuit breaker (or whatever action is called for in the procedures document), and placard the position light switch as INOPERATIVE
    • There are exceptions to the use of the MEL for deferral
      • For example, should a component fail that is not listed in the MEL as deferrable (the tachometer, flaps, or stall warning device, for example), then repairs are required to be performed prior to departure
      • If maintenance or parts are not readily available at that location, a special flight permit can be obtained from the nearest FSDO
      • This permit allows the aircraft to be flown to another location for maintenance
      • This allows an aircraft that may not currently meet applicable airworthiness requirements, but is capable of safe flight, to be operated under the restrictive special terms and conditions attached to the special flight permit
    • Minimum Equipment List
      Minimum Equipment List
    • Understanding the Minimum Equipment List:

      • There are two categories of procedures: maintenance procedures (M) and operations procedures (O)
        • An authorized mechanic must complete "M" procedures, but the pilot or flight crew can do "O" procedures
        • Once the owner/operator has created the procedures document, it is presented to the FAA for approval. If granted, the FAA inspector will issue a letter of authorization (LOA). When this letter is received the MEL is complete and the aircraft may be operated within the guidelines of the MEL rather than the procedures outlined in the regulations. This formula will help you remember: MMEL + Procedures Document + LOA = MEL
      • When a part of the aircraft is found to be inoperative the pilot will refer to the MEL
        • If the item is not in the procedures document, the aircraft is grounded
        • If the item is found, the pilot will take the appropriate actions required by the procedures document before flight
        • An MEL is equivalent to a supplemental type certificate and is required to be on board the aircraft during flight
        • The MEL is only valid for a specific aircraft and cannot be transferred to another
      • Column one shows each piece of equipment, listed by system [Figure 2]
      • Column two shows how many of that item are installed on the aircraft [Figure 2]
      • Column three shows the number of items installed that have to be operational for the aircraft to be airworthy [Figure 2]
      • Column four shows remarks or exceptions [Figure 2]
  • Kinds of Equipment Lists:

    • Beechcraft Kinds of Equipment List
      Weight and Balance Data
    • Pilots are required to determine if an aircraft confirms to the type certificate data sheet for which it was certified
    • These requirements can be modified depending on the operation, called Kinds of Equipment Lists (KOELs)
    • KOELs can be found in the aircraft POH operating limitations section
    • KOELs specify the kinds of operations (e.g., visual flight rules (VFR), instrument flight rules (IFR), day, or night) in which the aircraft can be operated
    • FAR 91.203 allows a person to takeoff an aircraft in operations conducted under part 91 with inoperative instruments and equipment without an approved Minimum Equipment List provided the flight operation is conducted in a:
      • Rotorcraft, nonturbine-powered airplane, glider, or lighter-than-air aircraft, powered parachute, or weight-shift-control aircraft, for which a master minimum equipment list has not been developed; or
      • Small rotorcraft, nonturbine-powered small airplane, glider, or lighter-than-air aircraft for which a Master Minimum Equipment List has been developed; and
      • The inoperative instruments and equipment are not:
        • Part of the VFR-day type certification instruments and equipment prescribed in the applicable airworthiness regulations under which the aircraft was type certificated;
        • Indicated as required on the aircraft's equipment list, or on the Kinds of Operations Equipment List for the kind of flight operation being conducted;
        • Required by Sec. 91.205 or any other rule of this part for the specific kind of flight operation being conducted; or
        • Required to be operational by an airworthiness directive; and
      • The inoperative instruments and equipment are:
        • Removed from the aircraft, the cockpit control placarded, and the maintenance recorded in accordance with Sec. 43.9 of this chapter; or
        • Deactivated and placarded "Inoperative." If deactivation of the inoperative instrument or equipment involves maintenance, it must be accomplished and recorded in accordance with part 43 of this chapter; and
      • A determination is made by a pilot, who is certificated and appropriately rated under part 61 of this chapter, or by a person, who is certificated and appropriately rated to perform maintenance on the aircraft, that the inoperative instrument or equipment does not constitute a hazard to the aircraft. An aircraft with inoperative instruments or equipment as provided in paragraph (d) of this section is considered to be in a properly altered condition acceptable to the Administrator
    • Although the certification rules require this information, there is no standard format; consequently, the manufacturer may furnish it in various ways
    • Beechcraft Kinds of Equipment List
      Weight and Balance Data

Documents Required:

  • Aircraft must have documentation to show compliance with federal regulations
    • The ability to show compliance at any time requires these documents are carried on the aircraft, usually located in a single binder or in a slip holder perhaps sewn on the back of a seat or side of the cabin
  • Those documents can be easily remembered through the acronym "AROW" or "ARROW:"

Inspections Required:

  • In addition to the required documentation, inspections must be completed in accordance with the operation
  • The required inspections can be remembered with the acronym "AVIATE:"
    • A – Airworthiness Directives

    • V – VOR Check:

      • Required every 30 days for aircraft operating under Instrument Flight Rules
      • Governed by FAR 91.171
      • May be performed by any pilot
    • I – Inspections:

      • 100-Hour:

        • Governed by FAR 91.409(b)
        • Aircraft operated for hire or used for flight instruction must have either an annual inspection or a 100-hour inspection every 100 hours of time in service
          • With respect to maintenance time records, time in service is the time from the moment an aircraft leaves the surface of the earth until it touches it at the next point of landing
          • Time in service is generally calculated with the tachometer
          • Note that renting an aircraft, even from a flight school, for personal use or carrying passengers not for hire is exempt from having a 100-hour inspection
        • The 100-hour limit may be exceeded by no more that 10 hours for the sole purpose of flying (for hire) to a location where the inspection can be completed
          • Any excess time over the 100-hour due time will be subtracted from the next 100 hour inspection
        • Aircraft normally operated for hire (for example, flight instruction at a flight school) may overfly the 100-hour inspection if the aircraft is not flown for hire (for example, a pilot rent's it for personal use)
      • Annual:

        • Governed by FAR 91.409(a)
        • Required for all aircraft
        • Completed every 12 calendar months, expiring at the end of the month one year after the inspection
        • Must be completed and properly endorsed by a mechanic with an inspection authorization (IA)
    • A – Altimeter/Pitot-Static System (IFR Only):

      • Altimeter inspections and tests are governed by Federal Aviation Regulation 91.411
      • Each altimeter must be tested and inspected within the preceding 24 calendar months or following installation or maintenance on the automatic pressure altitude reporting system of the ATC transponder where data correspondence error could be introduced
      • The static pressure system must be tested and inspected within the preceding 24 calendar months
      • These tests must be conducted by:

        • The manufacturer of the airplane, or helicopter, on which the tests and inspections are to be performed;
        • A certificated repair station
        • A certificated mechanic with an airframe rating (static pressure system tests and inspections only)
      • Altimeter and altitude reporting equipment approved under Technical Standard Orders are considered to be tested and inspected as of the date of their manufacture
      • No person may operate an airplane, or helicopter, in controlled airspace under IFR at an altitude above the maximum altitude at which all altimeters and the automatic altitude reporting system of that airplane, or helicopter, have been tested
    • T – Transponder

      • Transponder inspections and tests are governed by Federal Aviation Regulation 91.413
      • Must be tested and inspected within the previous 24 months or after installation or maintenance where data correspondence error could be introduced
      • Tests conducted by:
        1. A certificated repair station
        2. A holder of a continuous airworthiness maintenance program
        3. The manufacturer of the aircraft on which the transponder to be tested is installed, if the transponder was installed by that manufacturer
    • E – Emergency Locator Transmitter (ELT)

      • Must be tested and inspected every 12 calendar months
      • Governed by FAR 91.207
      • Must be replaced or recharged if the transmitter has been used for more than one hour of cumulative use
      • Must be replaced or recharged if 50% of its useful life has expired

Required Equipment:

  • Visual Flight Rules:

  • Instrument Flight Rules:

    • Day/Night IFR (GRABCARD):

      • G - Generator or alternator
      • R - Rate of turn indicator (turn coordinator or turn & bank indicator)
      • A - Altimeter, sensitive, adjustable for barometric pressure (Kollsman window)
      • B - Ball (slip-skid indicator [inclinometer])
      • C - Clock (digital or analog displaying hours, minutes, and seconds)
      • A - Attitude indicator
      • R - Radios (radio communication and navigation equipment suitable for the route to be flown)
      • D - Direction (gyroscopic) indicator (directional gyro or heading indicator)
  • Inoperative Equipment:

    • If any other item is inoperative, 14 CFR section 91.405 states that it shall be placarded as required by Sec. 43.11
    • Following scheduled inspections:
      • Aircraft shall have discrepancies repaired unless it is permitted to be in operative by 91.213
      • Maintenance personnel shall make appropriate entries in the aircraft maintenance records indicating the aircraft has been approved for return to service
    • Equipment impacting safety of flight must be repaired, but items that are not required may remain inoperative indefinitely provided they are appropriately placarded

Airworthiness Responsibilities:

  • Pilot-In-Command:

    • Determine airworthiness
  • Owner/Operator:

    • Register the aircraft
    • Maintain the aircraft in an airworthy condition in accordance with FAR 47.403 (see inspections above)

Airworthiness Certificate:

  • On the actual airworthiness certificate itself, you will find:
    • "Unless sooner surrendered, suspended, revoked, or a termination date is otherwise established by the Administrator, this airworthiness certificate is effective as long as the maintenance, preventive maintenance, and alterations are performed in accordance with parts 21, 43, and 91 of the federal aviation regulations, as appropriate, and the aircraft is registered in the United States"
  • "Unless sooner surrendered, suspended, revoked, or a termination date is otherwise established by the Administrator"
    • Various reasons including aircraft condition or legislation may null and void an airworthiness certificate
  • "This airworthiness certificate is effective as long as the maintenance, preventive maintenance, and alterations are performed in accordance with parts 21, 43, and 91 of the federal aviation regulations, as appropriate, and the aircraft is registered in the United States
    • The aircraft must be maintained in accordance with inspections listed above and preventative maintenance rules and regulations

Airworthiness Requirements Airman Certification Standards:

  • Satisfy the requirements of Section I, Task B by determining that applicant exhibits satisfactory knowledge, risk management, and skills associated with airworthiness requirements, including aircraft certificates
  • References: 14 CFR parts 39, 43, 91; FAA-H-8083-2, FAA-H-8083-25

Airworthiness Requirements Knowledge:

The applicant must demonstrate an understanding of:

Airworthiness Requirements Risk Management:

The applicant demonstrates the ability to identify, assess and mitigate risks, encompassing:
  • PA.I.B.R1:

    Inoperative equipment discovered prior to flight

Airworthiness Requirements Skills:

The applicant demonstrates the ability to:
  • PA.I.B.R1:

    Locate and describe airplane airworthiness and registration information
  • PA.I.B.R2:

    Determine the airplane is airworthy in a scenario given by the evaluator
  • PA.I.B.R3:

    Apply appropriate procedures for operating with inoperative equipment in a scenario given by the evaluator

Airworthiness Knowledge Quiz:


  • Airworthiness is a nuanced topic:
    • Manufacturers are responsible for airworthiness from factory
    • The A&P makes an airworthiness determination once a year on annual
    • The owner is responsibility to ensure that the airworthiness certificate is valid
    • The PIC is making an airworthiness determination continuously, every flight, and if an unairworthy condition develops in flight, the PIC is to end the flight
  • Remember that airworthiness requirements apply to all aircraft, owned or rented, as do the responsibilities to ensure compliance
    • Ramp checks are not the time to start taking airworthiness seriously
  • It is true that the Pitot-Static system does not require an inspection if operating VFR however, if operating in airspace which requires a transponder then the system will be looked at, albeit to a lesser extent than the required IFR check
  • To learn more about inspections, see also AOPA's guide to aircraft inspections
  • Whether or not your airplane has an MEL, FAR 91.213 still applies to all inoperative equipment and it is the pilot's responsibility to find out if the airplane has an MEL
  • MEL deferral of maintenance is not to be taken lightly, and due consideration should be given to the effect an inoperative component may have on the operation of an aircraft, particularly if other items are inoperative
    • Further information regarding MELs and operations with inoperative equipment can be found in AC 91-67, Minimum Equipment Requirements for General Aviation Operations Under FAR Part 91
  • Hours for inspectiosn are based on time in service, which is an ill-defined number
    • When basing inspections off hours, pilot's may run off the slower hours, to save money, or the higher hours, to be conservative
  • Master minimum equipment lists and associated documentation can be found on the FAA's website
  • Read more about aircraft lighting for additional context on requirements
  • Do not make it a habit to fly with a faulty component, unless there is a deliberate plan to correct
    • Further, if its tied to airworthiness, and especially if ATC knows about it, don't push your luck!
  • Those looking to apply for a radio license to fly internationally may visit the Federal Communications Commision's Universal Licensing System to learn more and apply
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