Airworthiness and Inoperative Equipment Under 14 CFR Part 91

Many pilots struggle with the regulations and procedures to follow when a preflight inspection or other before-takeoff check reveals a burned-out position light, a non-functional autopilot, or other inoperative equipment. Here’s a basic guide to help you through the thicket of FAA regulations and policies.

This discussion assumes you are operating a typical light GA aircraft under 14 CFR Part 91 and you’re not using a minimum equipment list (MEL). MEL are typically available only for multiengine and large aircraft, and they’re most often used in commercial operations. Note also that as of November 3, 2017, AC 91-67 – Minimum Equipment Requirements for General Aviation Operations Under FAR Part 91, has been canceled, pending a revision that “align[s] with the latest ICAO guidance.”

Before you begin the preflight inspection, review 14 CFR §91.7 Civil Aircraft Airworthiness:

§91.7 Civil Aircraft Airworthiness
(a) No person may operate a civil aircraft unless it is in an airworthy condition.

(b) 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.

Simply put, as PIC, you–not your mechanic, or the FBO from which you rent an airplane, or the partner(s) with whom you share an aircraft–are responsible for determining whether the aircraft you’re about to fly is legally airworthy and safe to operate.


Assume that during the preflight inspection, you discover that one of the wingtip position lights has burned out. The key questions to ask are:

  • Can you fly the airplane?
  • How can you comply with the applicable FAA regulations?

Many pilots think that such minor malfunctions require nothing more than recalling the required equipment regulations for day or night, VFR or IFR flight (14 CFR §91.205), and, if necessary, putting an “inoperative” sticker near the appropriate switch or gizmo before taking off.


The proper procedure, however, involves methodically tracing your way through several FAA regulations and references, including the aircraft flight manual (AFM) and associated aircraft documents.

Key FAA Regulations (14 CFR Part 91) and Documents

  • §91.7 Civil Aircraft Airworthiness
  • §91.205 Powered civil aircraft with standard category U.S. airworthiness certificates: Instrument and equipment requirements
  • §91.213 Inoperative instruments and equipment
  • §91.405 Maintenance required
  • Aircraft approved flight manual (AFM) or operating handbook (POH)
  • Applicable STC supplements
  • Aircraft Type Certificate Data Sheet (TCDS)

The process you must follow is described in §91.213 (PDF flow chart here). You are allowed to continue with the flight provided:


(2) The inoperative instruments and equipment are not—

(i) Part of the VFR-day type certification instruments and equipment prescribed in the applicable airworthiness regulations under which the aircraft was type certificated;

(ii) 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;

(iii) Required by §91.205 or any other rule of this part for the specific kind of flight operation being conducted; or

(iv) Required to be operational by an airworthiness directive

(3) The inoperative instruments and equipment are—

(i) Removed from the aircraft, the cockpit control placarded, and the maintenance recorded in accordance with §43.9 of this chapter; or

(ii) 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

(4) 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.

Here’s a flow chart that outlines the basic process described in §91.213.


Procedure for dealing with inoperative equipment under 14 CFR Part 91

Throughout the following discussion, note that if the defective or inoperative item is required at any of the decision points, maintenance or obtaining a ferry permit (technically a Special Flight Permit) is required before you can fly.

Begin by determining whether inoperative item is required under the basic regulations for VFR or IFR flight during the day or night (§91.205), including key engine instruments, altimeter, airspeed indicator, magnetic direction indicator, and so forth. Operations at night and under IFR (regardless of prevailing weather conditions) require additional instruments and equipment, such as lights (night) and radios and gyroscopic instruments (IFR).

If the item isn’t specifically listed in §91.205(a)-(d), next determine if it’s required by the AFM/POH equipment list or kinds of operations list (examples below).




If the item isn’t required by those equipment lists, or if you have an old AFM/POH that doesn’t include equipment lists, next confirm that the item is not required by the aircraft’s type certificate data sheet (TCDS). You can download PDF versions of TCDS from the FAA website, here. These data sheets are usually long and not easy to read, but you can search the PDF for your aircraft to help you locate specific model/serial numbers or items.


If the item isn’t required by the TCDS, review any STC supplements that apply to your aircraft. For example, if you’ve installed new avionics or electronic instruments in the panel, the STC under which that equipment was installed may contain specific limitations, such as additional sources of electrical power.


G500 AFMSupplement-02

Next, you must confirm that the item isn’t required by an airworthiness directive (AD). You can find ADs on the FAA website, here. Again, ADs can be difficult to parse. If you have questions, it’s best to consult a maintenance technician. Aircraft type and owner clubs are also good sources of information about ADs.

If you’ve answered “no” at each step of the process, you can proceed–but you must follow the proper procedure to deactivate or remove and then placard the item. And you must record the discrepancy and action taken in an appropriate record (§91.405 and §43.11).

Options at this point include disabling a switch, pulling and collaring a circuit breaker, or removing the equipment following the appropriate procedure. If the inoperative item is controlled by anything other than a simple switch, it’s best to consult a maintenance technician.

Finally, as PIC, you must determine that the aircraft is safe to operate under the conditions expected for the flight.

Note that you can’t continue to operate indefinitely with inoperative/defective equipment. See §91.405(c) and the De Joseph letter (2017) from the FAA chief counsel. In general, at the next required inspection the item must be repaired, replaced, or removed and the action properly documented by a maintenance technician.


The process described here is cumbersome, especially when you’re away from your home airport without easy access to references and technical advice.

But here’s a good rainy-day project. Create a list of equipment in your aircraft that isn’t clearly required by §91.205 for a typical day or night VFR flight, such as lights, avionics, accessories (seats, cabin heat, power plugs, speakers, etc.). Follow the flow chart, consult the resources described here, and note whether those items would be necessary for a flight under those circumstances.

If you fly IFR, add or note the equipment, beyond the basics in §91.205, that is required by the documents for your aircraft–regardless of the weather–to operate under those rules.

Keep those lists in your aircraft (or on your tablet or phone) so that you can quickly and easily determine whether you can proceed.

Additional References and Resources


Comments on Proposed Rule Changes

The FAA recently proposed several significant changes to regulations that expand the use of aviation training devices, training for the commercial pilot and certified flight instructor certificates, maintaining instrument currency, and other issues of interest to many general aviation pilots and flight instructor.

Below are my comments on some portions of the proposed rules, which I have submitted to the docket.

Use of TAA for Commercial and Flight Instructor Certificates

For all the reasons outlined in the proposal, I support the option to substitute a TAA (as redefined in the proposed rule) for the training and practical tests required for the commercial pilot and certified flight instructor certificates with single-engine-land ratings.

One commenter objects that pilots won’t gain experience “with higher performing engine[s], retractable gear, constant speed propeller, etc.” But most flight schools offering training for those certificates rely on aircraft such as the C172RG or Piper Arrow, which have at most 200-hp engines. These are hardly high-performance aircraft, either as defined by FAA regulation or by their speed, sophisticated avionics and equipment, or handling characteristics. Pilots who want to fly aircraft with retractable landing gear, constant-speed propellers, turbocharged engines, and other characteristics typically associated with high-performance aircraft will still, as a practical matter, require checkouts and operating experience mandated by regulations (e.g., the endorsement required to act as PIC in an aircraft with an engine rated at more than 200 HP), insurance, flight school policies, commercial operator specifications, and common sense (a refreshing concept endorsed in the recent proposal to revise 14 CFR Part 23 aircraft certification rules—viz., “The part 23 regulations should not need to prescribe basic physical principles, sound engineering judgment, and common sense.”).

The checkout required for aircraft like the C172RG or Piper Arrow is hardly a leap from a Skyhawk or Warrior. Instead, it’s a small step, and learning to operate and confirm the configuration of, for example, retractable landing gear, is only a small part of a complete commercial pilot or CFI training syllabus, and that basic training hardly prepares a pilot to fly a truly high-performance “complex” aircraft such as Cirrus SR22 (which has fixed landing gear) or a Beechcraft Bonanza.

Similar examples: (1) Pilots with MEL ratings on their pilot certificates legally can fly any multiengine aircraft that doesn’t require a type rating. But in the real world, they must receive training and gain operating experience in specific makes and models to obtain insurance, fly rental aircraft, or act as PIC in a commercial operation; (2) Regulations require only a single logbook endorsement to fly tailwheel aircraft. But the handling characteristics of tailwheel aircraft vary widely (even among those that don’t have big engines, constant-speed propellers, etc.). Again, insurance, rental policies, and common sense oblige pilots who fly tailwheel aircraft to receive training and gain operating experience in specific makes and models.

Maintaining IFR Currency with ATDs

I applaud the proposed changes that would allow instrument-rated pilots to maintain currency with in any combination of aircraft, FFS, FTD, or ATD without requiring an instructor to be present. The current regulations are a deterrent to pilots who use ATDs. They must parse the rules and carefully review their logbooks to ensure that they have met the arcane requirements for various tasks, time limits, and calendar constraints. Instead of using training devices, today most pilots hop in their aircraft with a safety pilot (not necessarily an instructor) and repeatedly fly the same familiar procedures in their local areas, missing opportunities to practice the important skills of briefing and setting up a variety of DPs, arrivals, and approaches that include such elements as DME arcs and course reversals. They also typically don’t gain experience handling realistic equipment failures, challenging weather, and so forth. As the FAA notes, the proposed changes would encourage pilots to maintain their instrument skills.

My experience as an instructor strongly suggests that it’s the mental, puzzle-solving side of IFR flying that deteriorates most quickly over time. Use of training devices is the most effective, efficient way to hone and maintain those mental skills.

Pilots who want to use a training device at a flight school will still require at least an initial checkout on the equipment to ensure that they can use it effectively. Those checkouts are an opportunity for pilots to work with instructors to deficiencies in both their understanding of IFR flying and specific piloting skills, and those encounters will help instructors to develop relationships with pilots who otherwise might not be receiving training.

Pilots are upgrading aircraft to include sophisticated avionics (even if the panel doesn’t meet the revised definition of a TAA). They are increasingly using tablets and other devices as substitutes for charts and to provide information about weather, traffic, and other details. Allowing pilots wider, creditable use of training devices that include, for example, GPS navigators, will help them develop and maintain the essential skills described in such publications as the Advanced Avionics Handbook and Instrument Procedures Handbook. Using training devices also gives pilots opportunities to practice using new technology and develop good operating procedures.

Definition of ATD

The notice includes a new definition of aviation training device (ATD):

The FAA is now proposing to define ATD in § 61.1 as a training device, other than a full flight simulator or flight training device, that has been evaluated, qualified, and approved by the Administrator.

It’s not clear, however, if the proposed changes would eliminate the basic aviation training device (BATD) and advanced aviation training device (AATD) categories as described in AC 61-136 FAA Approval of Basic Aviation Training Devices (BATD) and Advanced Aviation Training Devices (AATD). The language in various sections of the proposed rules is ambiguous and should be clarified, and AC 61-136 and related policy guidance should be revised to ensure that both FAA and airmen throughout the system have a clear understanding of distinctions among the devices. I understand that for the purposes of FAA approval the existing categories may remain desirable—especially for manufacturers. But FAA inspectors, pilots, and instructors should not be confused about the practical application of ATDs for training and maintaining currency.

“The AIM is not Regulatory”

"The AIM is not regulatory" is an often-heard refrain among pilots and flight instructors. And technically, of course, that’s correct.

From the introduction to the Aeronautical Information Manual:

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.

However, when aviators say, “The AIM is not regulatory,” they generally seem to argue that the procedures and guidance in the AIM (and related FAA publications, such as advisory circulars), are suggestions that pilots, at their discretion, may adopt or ignore.

I’m certainly not an attorney. But I offer this background on the authority of the AIM from AOPA Flight Training. That Legal Briefing (written by an attorney) notes in part:

…In older NTSB cases, both the FAA and the airman have used sections of the AIM to assess whether an airman’s conduct was in violation of the FAR or not. For example, an airman attempted to justify a right turn during his approach to the airport as part of a "straight-in" approach as set forth in the AIM. But the case did not rely on the new statutory language of deference.

In a more recent NTSB case involving a pilot’s misunderstood readback of an ATC instruction that ATC failed to correct and which resulted in an altitude deviation, the NTSB found that because the pilot acted as best he could to understand and comply with the ATC instruction, he could not be held responsible for the deviation. But the FAA appealed the NTSB’s decision to the Court of Appeals, which held that the NTSB must defer to the FAA’s interpretation that the pilot is responsible for accurately understanding and complying with an ATC instruction absent an equipment malfunction or an emergency. The court sent the case back to the NTSB, which then had to find the pilot in violation.

These cases suggest that you may be held responsible for complying with FAA guidance. Or, you could find yourself defending against an interpretation of a regulation that the FAA announces, for the first time, in response to your conduct. In any event, while it may not be a regulatory requirement to comply with any FAA written guidance, you can certainly expect any such guidance to be used in a FAA enforcement case. And, you can expect that the NTSB will be bound to defer to the FAA’s interpretation of your conduct as a violation of the FAR, unless you are prepared to show the FAA’s interpretation to be arbitrary, capricious, or illegal.

So, while it’s true that guidance in the AIM is, technically, just that–guidance–the information in the AIM, ACs, etc. isn’t just the FAA’s suggestions or a matter of procedure. If you choose to invent techniques for complying with the letter of the regulations, you may find the "AIM isn’t regulatory" a weak defense.