Date: 31 October, 1992
Subject: [Composite Primary Structures] - Amateur-Built Aircraft
[This advisory material provides guidance for the construction of amateur-built aircraft whose primary structure is made of composite (non-metallic) materials.]
2. Reference Airworthiness Standards.
Airworthiness Manual Chapter 549 (Airworthiness Standards Amateur Built Aircraft) Section 549.7 paragraph (b).
3. Background And Discussion.
[When composite amateur-built aircraft first appeared, there was a need to provide guidance to builders, designers and Transport Canada Airworthiness Inspectors or others to ensure that each designer provided adequate instructions with his product for the builder, to ensure that the builder had complete instructions for the proper assembly procedures.
[Since that time, the availability of composite aircraft kits has increased to the point where they are one of the most common types on the market. As a result, designers are more knowledgeable of proper manufacturing technologies, they are providing adequate information for the proper assembly of their product, and Transport Canada now accepts such kits without evaluation.
[While the designs and designers instructions are generally adequate, there are still instances where builders of composite aircraft are not always adhering to the manufacturers instructions during construction. Such cases of improper construction techniques have resulted in fatal accidents. Thus, there is still a need to make builders aware of the importance of observing the proper techniques for the assembly of composite aircraft.
[Construction of aircraft in which primary structure is a fibre reinforced resin requires several special considerations that are not applicable to traditional methods of construction. Even with ideal conditions, structural integrity is not assured. This applies whether the aircraft is built from raw materials or from bonded, pre-moulded components. Following inspections and investigations of accidents, it has been determined that joints do delaminate, even when reasonable preparation techniques have been followed. Unfortunately, at this time it is impossible to determine integrity by any non-destructive inspection technique, therefore general builder attitude and expertise is the only available guide to the probability of a good job being done.]
- [Builders of composite aircraft are urged to familiarize themselves with the recommended procedures for fabricating composite materials. As a part of this process, builders should:
- [carefully review all aspects of the design and designer's instructions;
- [review inspection and repair instructions;
- [familiarize themselves with related material regarding composite aircraft construction;
- [fabricate the aircraft structure in conformance with the designer's instructions, other instructions or any other "mandatory" advice in the form of newsletter or service bulletins;
- [not substitute for specified materials unless authorized by the designer;
- [ensure proper shop and working conditions (temperature, humidity); and
- [ensure proper joint preparation.
- [It is strongly recommended that builders make and retain for future reference, representative samples of all bonded joints, paying particular attention to those made during environmental changes of temperature, humidity etc.]
5. [Reference Bibliography/Material.
The Experimental Aircraft Association Aviation Foundation offers for sale publications and videos on the subject of composite aircraft construction. Information may be obtained by contacting:
EAA Aviation Foundation
P.O. Box 3065
Chief, Airworthiness Standards