## Aircraft Design, Certification, and Airworthiness 

The FAA certifies three types of aviation products: aircraft, aircraft engines, and propellers. Each of these products has been designed to a set of airworthiness standards. These standards are parts of Title 14 of the Code of Federal Regulations (14 CFR), published by the FAA. The airworthiness standards were developed to help ensure that aviation products are designed with no unsafe features. Different airworthiness standards apply to the different categories of aviation products as follows: 

• Normal, Utility, Acrobatic, and Commuter Category Airplanes- 14 CFR part 23 

• Transport Category Airplanes—14 CFR part 25 

• Normal Category—14 CFR part 27 

• Transport Category Rotorcraft—14 CFR part 29 

• Manned Free Balloons—14 CFR part 31 

• Aircraft Engines—14 CFR part 33 

• Propellers—14 CFR part 35 

Some aircraft are considered “special classes” of aircraft and do not have their own airworthiness standards, such as gliders and powered lift. The airworthiness standards used for these aircraft are a combination of requirements in 14 CFR parts 23, 25, 27, and 29 that the FAA and the designer have agreed are appropriate for the proposed aircraft. 

The FAA issues a Type Certificate (TC) for the product when they are satisfied it complies with the applicable airworthiness standards. When the TC is issued, a Type Certificate Data Sheet (TCDS) is generated that specifies the important design and operational characteristics of the aircraft, aircraft engine, or propeller. The TCDS defines the product and are available to the public from the FAA website at www.faa.gov. 

## A Note About Light Sport Aircraft 

Light sport aircraft are not designed according to FAA airworthiness standards. Instead, they are designed to a consensus of standards agreed upon in the aviation industry. The FAA has agreed the consensus of standards is acceptable as the design criteria for these aircraft. Light sport aircraft do not necessarily have individually type certificated engines and propellers. Instead, a TC is issued to the aircraft as a whole. It includes the airframe, engine, and propeller. 

Aircraft, aircraft engines, and propellers can be manufactured one at a time from the design drawings, or through an FAA approved manufacturing process, depending on the size and capabilities of the manufacturer. During the manufacturing 

process, each part is inspected to ensure that it has been built exactly according to the approved design. This inspection is called a conformity inspection. 

When the aircraft is complete, with the airframe, engine, and propeller, it is inspected and the FAA issues an airworthiness certificate for the aircraft. Having an airworthiness certificate means the complete aircraft meets the design and manufacturing standards, and is in a condition for safe flight. This airworthiness certificate must be carried in the aircraft during all flight operations. The airworthiness certificate remains valid as long as the required maintenance and inspections are kept up to date for the aircraft. 

Airworthiness certificates are classified as either “Standard” or “Special.” Standard airworthiness certificates are white, and are issued for normal, utility, acrobatic, commuter, or transport category aircraft. They are also issued for manned free balloons and aircraft designated as “Special Class.” 

Special airworthiness certificates are pink, and are issued for primary, restricted, and limited category aircraft, and light sport aircraft. They are also issued as provisional airworthiness certificates, special flight permits (ferry permits), and for experimental aircraft. 

More information on airworthiness certificates can be found in Chapter 9, in 14 CFR parts 175-225, and also on the FAA website at www.faa.gov. 

## Lift and Basic Aerodynamics 

In order to understand the operation of the major components and subcomponents of an aircraft, it is important to understand basic aerodynamic concepts. This chapter briefly introduces aerodynamics; a more detailed explanation can be found in Chapter 5, Aerodynamics of Flight. 

Four forces act upon an aircraft in relation to straight-and­ level, unaccelerated flight. These forces are thrust, lift, weight, and drag. [Figure 3-1] 

Thrust is the forward force produced by the powerplant/ propeller. It opposes or overcomes the force of drag. As a general rule, it is said to act parallel to the longitudinal axis. This is not always the case as explained later. 

Drag is a rearward, retarding force and is caused by disruption of airflow by the wing, fuselage, and other protruding objects. Drag opposes thrust and acts rearward parallel to the relative wind. 

