Experimental aircraft regulations trade the design freedom of an FAA experimental airworthiness certificate for a fixed set of operating restrictions, testing obligations, and inspection duties that stay with the airplane for its entire life. The certificate is issued under 14 CFR 21.191 for specific purposes: research and development, showing compliance with regulations, crew training, exhibition, air racing, market surveys, amateur-built, primary kit-built, and light-sport.1eCFR. 14 CFR 21.191 – Issue of Experimental Airworthiness Certificates Amateur-built aircraft make up the largest share of the registry, and most of the rules below apply squarely to them.
Whichever purpose you hold, the operating limitations document issued with the certificate is the rulebook for your airplane. It sets your test area, your minimum flight hours, your inspection requirements, and precisely what you can and cannot do. Everything that follows either comes from that document or from the federal regulations it points to.
Phase I Flight Testing
Every newly certificated experimental aircraft enters Phase I flight testing before it can carry anyone besides the required flight crew or fly outside a restricted geographic area. The purpose is to prove the airplane flies safely: control response, stability, engine performance, stall behavior, and every installed system.
Hours and Test Area
Your operating limitations will specify either 25 or 40 hours of required flight testing. Aircraft using an engine and propeller combination with an established track record on that airframe design typically get the 25-hour minimum. Aircraft with untested powerplants or unconventional configurations get 40 hours.2Federal Aviation Administration. Amateur-Built Aircraft and Ultralight Flight Testing Handbook
Every Phase I flight must stay within a geographic area defined in your limitations, usually a radius from your home airport. That area has to be over sparsely populated land or open water with light air traffic. No flying over densely populated areas, through congested airways, or into Class B airspace without prior approval. Each test flight has to begin and end at the airport named in your limitations.
Who Can Be On Board
During Phase I, only the minimum required flight crew may be aboard. For a typical single-engine amateur-built, that means the pilot and no one else. No passengers, no observers, no helpers until Phase I is signed off.3Federal Aviation Administration. Advisory Circular 90-116 – Additional Pilot Program for Phase I Flight Test
The Task-Based Alternative
The FAA now offers a task-based alternative to hour-based Phase I. Under AC 90-89C, you work through 17 structured test tasks using test cards carried in the aircraft. Phase I ends when all tasks are complete and the aircraft demonstrates expected performance. The program also requires you to compile an Aircraft Operating Handbook from your test results. Your operating limitations must specifically authorize this option, so raise it with your DAR or FSDO inspector before the airworthiness inspection, not after.2Federal Aviation Administration. Amateur-Built Aircraft and Ultralight Flight Testing Handbook
Permanent Operating Restrictions in Phase II
Completing Phase I moves the aircraft into Phase II, where it will remain for the rest of its operational life. The area and crew restrictions relax significantly. Several hard limits never go away.
No Flying for Compensation or Hire
You cannot carry persons or property for compensation or hire in an experimental aircraft. That rules out air taxi, paid sightseeing, and charter. The FAA can issue a letter of deviation authority allowing flight training in certain experimental aircraft, but the applicant has to request it at least 60 days in advance and demonstrate an equivalent level of safety.4eCFR. 14 CFR 91.319 – Aircraft Having Experimental Certificates: Operating Limitations
Densely Populated Areas and Congested Airways
The default rule is straightforward. No operations over densely populated areas or in congested airways. Altitude sufficient for an emergency landing does not satisfy this requirement, contrary to what some builders assume. The only way to legally operate over a densely populated area is to obtain special operating limitations from the Administrator, issued case by case.4eCFR. 14 CFR 91.319 – Aircraft Having Experimental Certificates: Operating Limitations
Telling Passengers and ATC
Before every flight carrying another person, you have to advise them the aircraft has an experimental certificate. It is a regulatory requirement, not courtesy. You also have to notify air traffic control of the aircraft’s experimental status when using ATC services.4eCFR. 14 CFR 91.319 – Aircraft Having Experimental Certificates: Operating Limitations
Night and Instrument Flight
By default, experimental aircraft are restricted to VFR flight during daytime hours. This surprises builders with well-equipped panels who assume the equipment authorizes the operation. It does not. Night and instrument flight have to be specifically authorized by the Administrator through your operating limitations.4eCFR. 14 CFR 91.319 – Aircraft Having Experimental Certificates: Operating Limitations
In practice, the FAA routinely grants night and IFR authorization for amateur-built aircraft through standard operating limitations language, provided the equipment listed in 14 CFR 91.205(c) for night flight or 91.205(d) for IFR is properly installed, operational, and maintained. All maintenance and inspection of IFR equipment must be recorded in the aircraft’s maintenance records. If your operating limitations document does not include this authorization, you are day-VFR only regardless of what is in the panel.
Pilot Certificate and Medical
The experimental certificate applies to the aircraft, not the pilot. You still need a valid pilot certificate. For most amateur-built aircraft, that means at least a private pilot certificate with the appropriate category and class rating. A sport pilot certificate may work for certain lighter experimentals that meet sport pilot aircraft limits, but it will not cover larger or faster homebuilts.
Medical certification follows the rules for any other aircraft in the same operating category. A current FAA medical certificate (Class 3 or higher) is required unless you qualify for BasicMed. BasicMed is available for experimental aircraft operations as long as the aircraft carries no more than seven occupants and has a maximum certificated takeoff weight of 12,500 pounds or less, which covers virtually every homebuilt on the registry.
Maintenance and the Annual Condition Inspection
Owner Maintenance
Experimental aircraft owners can perform their own maintenance, preventive maintenance, and alterations, including engine work, avionics changes, and structural modifications. Type-certificated aircraft require a certificated mechanic for most of that work. Experimental aircraft do not.
Condition Inspection Every 12 Months
Experimental aircraft are exempt from the standard annual and 100-hour inspection requirements that apply to type-certificated aircraft.5eCFR. 14 CFR 91.409 – Inspections In their place, the operating limitations require a condition inspection every 12 calendar months. Its scope follows Appendix D to 14 CFR Part 43, covering the airframe, engine, propeller, and installed systems.6Legal Information Institute. 14 CFR Appendix D to Part 43 – Scope and Detail of Items To Be Included in Annual and 100-Hour Inspections
The condition inspection can be performed by a certificated mechanic holding an Airframe and Powerplant (A&P) rating, or by the aircraft’s original builder if that person holds a Repairman Certificate. The airplane cannot legally fly until the inspection is signed off.
Repairman Certificate for the Builder
If you built the aircraft yourself, you can apply for a Repairman Certificate (Experimental Aircraft Builder) under 14 CFR 65.104. It authorizes you to perform the annual condition inspection on that specific aircraft and no other. To qualify you must be at least 18, be the primary builder, demonstrate sufficient skill to assess the aircraft’s condition for safe operation, and be a U.S. citizen or lawful permanent resident.7eCFR. 14 CFR 65.104 – Repairman Certificate, Experimental Aircraft Builder, Eligibility, Privileges and Limitations
The certificate has real value. Hiring an A&P for a condition inspection typically runs several hundred dollars annually, and scheduling can be difficult in areas with few mechanics experienced in experimental aircraft. The repairman certificate removes that dependency for as long as you own the airplane. It does not transfer with the aircraft on sale, so a subsequent owner needs an A&P for condition inspections.
Records
Whether you do your own maintenance or hire it out, you have to keep complete records for the airframe, engine, propeller, and all appliances. Each entry needs a description of the work, the completion date, and the signature and certificate number of the person returning the aircraft to service. You also have to track total time in service, current inspection status, and the status of any life-limited parts. Records transfer with the aircraft on sale.8eCFR. 14 CFR 91.417 – Maintenance Records
Insurance
The FAA does not require insurance for privately operated experimental aircraft. No federal rule mandates liability or hull coverage. Some airports require proof of liability insurance as a condition of basing or landing, and any lender financing your build will almost certainly require hull coverage, but the regulatory requirement simply does not exist.
Flying without liability insurance is still a serious financial gamble. A single ground-impact accident involving property damage or injuries to people on the ground can produce liability exceeding most individuals’ net worth. Experimental aircraft coverage is available from specialty aviation underwriters, and premiums tend to run higher than comparable coverage for type-certificated aircraft. Insurers typically evaluate the builder’s experience, total flight hours, the aircraft type’s safety record, and whether Phase I is complete. Getting quoted during the build, before you need coverage, gives you time to shop rates and address any underwriting concerns.