When an aircraft is designed it must be suitable for its intended purpose, that is, what the market has demanded. Of course, it must also be safe and meet all of the regulatory requirements. To this end the aircraft designer determines the design rules the aircraft must meet.
For most modern general aviation aircraft with a maximum take-off weight of not more than 12,500 pounds (rounded to 5,700 kg in the metric system) the applicable design rules are usually the American Federal Aviation Regulations (FARs) Part 23. Recreational aircraft are designed to meet different design rules and I will look at those in another issue.
The Design Engineer determines what maximum take-off weight will be required to carry the desired payload and the operational category he desires, such as normal or acrobatic category. He then consults FAR Part 23 to determine the structural strength requirements and airspeed limitations that his design must meet in order for it to be subsequently certified and sold as a certified aircraft. These regulations specify the operational limits to which the aircraft can be operated.
Once the aircraft design is finished structural test components are built and tested to confirm that they are strong enough to carry the required loads. All major components such as wings, fuselage, tailplane, undercarriage, engine mount etc. are structurally tested this way, usually before the prototype aircraft is built or flown. Finally, the prototype aircraft is flown and tested. The testing starts off with basic flight handling assessment at light weights. The testing is continued, progressively becoming more severe, and eventually the entire flight envelope is evaluated at maximum weight, maximum speeds, through the full centre of gravity range and maximum allowable ‘g’ loadings.
In reality, flight testing consists of two distinct phases. The first is ‘developmental’ test flying. During this phase any deficiencies in the design are identified, fixed and tested again. Also, possible product improvements or suggestions from customers may be developed and tested at this time. Once the final design has been established the formal certification flight testing can begin. This testing is done in conjunction with the regulatory authority, in our case in Australia, CASA. This testing is carried out to formal test schedules with the aim of proving that the final product fully complies with the applicable design standard. All intended flight limitations are thus confirmed or determined during this process.
Once all of the flight testing has been completed, and all of the reports written, they are submitted to CASA for their evaluation and approval as the regulatory authority. The final step in the certification process is the issue, by CASA, of the Type Certificate (TC); the document that formally states that the aircraft type complies with all applicable design requirements and is suitable for manufacture and sale to the public. Another document, the Type Certificate Data Sheet (TCDS) forms part of the TC and lists the specifications, conditions and limitations under which airworthiness requirements for the aircraft were demonstrated and met such as engine make and model, fuel type, engine limits, airspeed limits, maximum weight, minimum crew, etc.
The structural and flight testing required for certification of a new type to FAR Part 23 is very extensive and may take a year or more to complete. This massive task is why your new aircraft can be so expensive. The design and type certification process takes so long and costs millions of dollars. This cost has to be amortised over only a few hundred aircraft of that model that will be built, rather than the tens or even hundreds of thousands when we are talking about cars.
Once the aircraft is in service pilots, LAMEs and CAR 35 engineers must have ready access to all limitations and airworthiness requirements. For all modern aircraft reference to the TCDS will provide the required information. The TCDS will not necessarily provide all of it directly but other sources will be clearly identified. For instance, the Approved Flight Manual is the document that provides all of the operating limitations and procedures required by the pilot, and similarly, for the LAMEs maintaining the aircraft, the Maintenance Manual which provides details and procedures for carrying out maintenance on the aircraft. This manual also details any airworthiness limitations that may apply such as any structural or component life limitations.
So clearly, the TCDS is the document that provides the definitive data relating to your aircraft. Interestingly it is not provided directly by the manufacturer when you buy a new aircraft as technically it is a document held by the airworthiness authority who certified the aircraft, in the case of an Australian manufactured aircraft, CASA.
I believe all aircraft owners should obtain a copy of the TCDS for their aircraft. For aircraft designed and certified in Australia (such as the Gippsland Aeronautics GA8 Airvan), the TCDSs can be found on the CASA web site at www.casa.gov.au/casadata/cota/aust.htm. For aircraft of US origin the TCDSs can be found on the FAA web site at www.faa.gov/aircraft and follow the link to the TCDSs.