Airworthiness Certification

Overview

After type certification, other issues must be dealt with on the way to issuance of an airworthiness certificate.

In this section, the following subjects are covered:

• • Major and minor changes to type design
• • Foreign design standards
• • Production certification
• • Issuance of the airworthiness certificate
• • Postcertification activities

Changes to Type Design

The holder of a Type Certificate (TC) may make changes to the TC, the procedures for which will depend on whether those changes are major or minor.

7.2.3 Defining Major and Minor Changes

Determining whether a change to a product is major or minor has long been a problem subject. To some extent it involves a judgment call, complicated by the fact that the finding may be correct for the specific product system, but may not be correct if the change also affects other systems or product performance. Some guidance can be found in Federal Aviation Regulations (FAR) Part 43, Appendix A, Type Design Changes. This is a FAA document.

Major Change

As defined in FAR 21.93, a major change to a type design is one that has an appreciable effect on:

• • weight
• • balance
• • structural strength
• • reliability
• • operational characteristics
• • other characteristics affecting airworthiness

7.2.5 Minor Change

A minor change is defined as having no appreciable effect on these characteristics; any change not classified as major is classified as minor.

Appreciable—Derived Definition for TC Purposes

Some changes to the type design of a product (such as cosmetic changes) may obviously have no effect on the aforementioned characteristics, while other changes may have some effect, but not “appreciable.”

So, there are actually three degrees of change:

• • no effect
• • some effect
• • appreciable effect

A change is considered to have an appreciable effect on the specified characteristics when:

• • revisions to published data or procedures (relative to the characteristics) are required;
• • tests are required to reestablish compliance with the FAR applicable to the change, and/or to reestablish that hazardous or unreliable conditions are not introduced in the product because of the change.

A change that has some effect on the specified characteristics, but for which none of the actions specified previously for a major change are required, may be classified as a minor change.

A change that has no effect on any of the specified characteristics may be classified as a minor change.

Change Approvals

FAR 21.97 requires that the applicant (TC holder) submit substantiating data and necessary descriptive data for inclusion in the type design. Depending upon the complexity of the change and its effect on basic airworthiness, flight tests and/or ground tests may be required to resubstantiate compliance with the applicable FAR. The steps in the approval process are generally similar to those for a complete Type Certificate, since the change may require revisions to the AFM, the TC Data Sheet, or verification of compliance with FAR 121. This would be standard procedure for major changes.

Approvals for Minor Change

FAR 21.95 states that before submitting any substantiating or descriptive data, minor changes may be approved under a method acceptable to the Administrator. Additionally, FAR 21.95 implies that the substantiating or descriptive data must be submitted to the Aircraft Certification Office (ACO) after the minor changes have been approved. The extent of postapproval review of the data would be at the option of the ACO.

Type Design Changes by Persons Other Than the Type Certificate Holder

Anyone may apply for FAA approval of changes to a type certified product, and the applicant for the approval does not need to get permission from the TC holder. The approval process for such changes may take one of several forms, but in all cases the applicant must show, and the FAA must find, that the basic airworthiness standards of the FAR have been met.

Supplemental Type Certificates

A supplemental type certificate (STC) is a design approval processed and issued by an FAA ACO or a Designated Alteration Station for a modification to an aircraft in service, or by an FAA ACO for replacement or modification parts for use on type-certified products.

An applicant for an STC may have one of a number of reasons for the design approval. The person may be the owner of an aircraft who wishes to modify his/her aircraft for better performance, such as installing a larger engine or adding high lift devices to the wings.

Also, persons who wish to produce replacement or modification parts for type-certified products may apply for an STC to cover the parts and the installation of the parts in specific products.

STCs are not issued on parts for general applications—so-called “standard” parts.

The final evidence of STC approval is a certificate similar to a type certificate that carries the same privileges. An STC may be sold or leased by the holder to others and may be used as the basis for obtaining a production approval. If the approved modification affects the operating characteristics of the aircraft in which it is installed, then changes to the performance procedures and any operating limitations required are issued as a supplement to the original type-certified AFM and this is part of the STC. There is no amendment to the original Type Certificate Data Sheet or AFM. An STC can’t be issued until installation approval of the product is obtained from the FAA. Accordingly, the systems engineer may require STC system callout on airplane OEM installation drawings as part of the amended type design.

Foreign Adoption of FAA Regulations

As an acceptable international standard, many countries have adopted the FAA regulations for use by their own aviation industry. Some, such as West Germany, have adopted the FARs verbatim in the English language. Others, such as Brazil, have translated the FARs into their own language, perhaps with modifications to meet their own purposes. Such modifications would be acceptable to other countries if they still meet or exceed the basic International Civil Aviation Organization (ICAO) standards.

Joint Airworthiness Requirements

The Joint Airworthiness Requirements (JARs) are design standards for aircraft and other products adopted by most of the countries of Western Europe and the United Kingdom, intended as a common standard for aircraft and other products marketed among participating countries. The JARs may be described as a combination of ICAO standards, FARs, and BCARs (British Civil Aviation Regulations), with other requirements submitted by member countries to satisfy their own purposes. Today, the JARs are the European airworthiness standard for any new type of certification program.

Other Airworthiness Requirements

Basically, there are no other design standards with international acceptance except the FARs, BCARs, and JARs. The former Soviet Union is a member of ICAO with standards that meet ICAO requirements; however, its design standards have now just been “divulged” to the West.

The People’s Republic of China until recently used the Russian standards, but now has adopted the FARs verbatim. Civil Aviation Administration of China (CAAC) was formed on November 2, 1949 to manage all non-military aviation in the country, as well as provide general and commercial flight service.

Inspections—Airworthiness vs Conformity

There is a difference between types of inspections depending on whether the inspection is for type certification or production certification.

Conformity Inspections

FAA inspections performed at an airplane OEM or at the supplier prior to issuance or amendment of a Type Certificate are called conformity inspections. Conformity inspections are done on parts components only.

Airworthiness Inspections

By contrast, FAA inspections performed at an airplane OEM after issuance or amendment of a Type Certificate are called “airworthiness” inspections. These inspections are done on the product; components are not inspected individually.

1. 1. Production Certification
   FAR Subpart G
   FAA inspections performed at OEM after Type Certificate is issued or amended by FAA.
   The inspections are known as “airworthiness inspections.”
   Authority:
   FAR 21.157
   FAR 21.163
   FAR 21.183
   Method:
   FAA Order 8130.2
2. 2. Type Certification
   FAR Subparts B & D
   FAA inspections performed at DAC or suppliers prior to Type Certificate being issued or amended.
   These inspections are known as “conformity inspections.”
   Authority:
   FAR 21.33
   FAR 21.53
   Method:
   FAA Order 8110.4

Standard Airworthiness Certificate

A Standard Airworthiness Certificate attests that the aircraft to which it is issued conforms to the Type Certificate for the aircraft and meets the international requirements of ICAO. The Standard Airworthiness Certificate denotes the highest level of airworthiness, and that the aircraft may be used for carrying passengers in commercial operations.

A Standard Airworthiness Certificate is transferable with the aircraft and remains valid as long as the aircraft is airworthy, properly maintained, and all replacement or modification parts are properly approved and installed in accordance with approved data.

Standard Airworthiness Certificates are issued for aircraft type certified to the standards in FARs 23, 25, 27, 29 and 31, and for special classes of aircraft shown to meet design standards found acceptable by the FAA.

Special Airworthiness Certificates

Special Airworthiness Certificates are issued for aircraft that do not meet the high standards set for “standard” aircraft but may be safely operated under limitations established in the FAR and/or prescribed by the issuing FAA inspector. In general, an aircraft with a Special Airworthiness Certificate cannot be operated for hire, in some cases cannot carry passengers, and may be restricted to operations only over sparsely populated areas or over water.

There are several types of Special Airworthiness Certificates: restricted, limited, and experimental. For the purposes of this section, we will take up the experimental category only.

Experimental

An Experimental Airworthiness Certificate may be issued for any aircraft that does not conform to a TC but may be operated under limitations for the protection of persons and property on the ground, as well as other aircraft in flight. For most of the experimental purposes authorized in FAR 21.191, passengers cannot be carried and operations cannot be conducted for hire. The purposes for which experimental certificates may be issued (that are applicable to this section) are:

• • flight testing (for research and development or to show compliance with the FARs)
• • crew training (of the applicant’s flight crews)
• • market surveys—under this purpose, in addition to market surveys, customer sales demonstrations and customer crew training may also be conducted. Since this purpose involves carrying passengers and operations from busy airports, certain requirements in the interest of safety must be met before an experimental certificate may be issued for this purpose.

Airworthiness Directives

Airworthiness Directives (ADs) are issued by the FAA when an unsafe condition exists in a type certificated product, and that condition is likely to exist on other products of the same type design. Any action requiring either correction or redesign of a system is an action in which the responsible systems engineer will be involved.

Obviously, it would be preferable to have no need for corrective action, which brings us full circle. To the degree we all know what is expected from the FAA, including the FARs and other regulatory requirements, we can reduce the need for correction and for ADs.

Doing it right the first time will always be preferable to corrections and redesigns downstream, even when those corrections and redesigns are done well.