Are you familiar with the wealth of information contained in your airplane’s TCDS? You should be!
What, you ask, is a Type Certificate Data Sheet (TCDS)? If you are an owner, you need to know. If you are thinking about becoming an owner, you also need to know. The TCDS is something that IAs must to be aware of, but do not always properly utilize. Every certificated airplane has one, save for some antiques.
The TCDS sets forth some of the critical parameters that the aircraft must meet in order to be considered airworthy. Before about 1960, the data sheets were called “Aircraft Specifications,” but the format is basically the same. The only exception to compliance with the TCDS is if the aircraft has had one of the TCDS particulars modified by a Supplemental Type Certificate (STC) or a field approval.
What does “airworthy” mean?
Let’s take a quick detour and discuss what is meant by the term “airworthy.” You will not find it in FAR Part 1, which contains definitions for terms used in the FARs. In 2005, the FAA added the definition in FAR 3.5(a), which is likely broadly applicable, even though it could be read as being limited to that section:
“14 CFR §3.5(a) Definitions. The following terms will have the stated meanings when used in this section: Airworthy means the aircraft conforms to its type design and is in a condition for safe operation.”
The interpretation that this 3.5(a) definition should be read as the operational definition of “airworthy” for all purposes is supported by ICAO’s Annex 8 and several NTSB decisions which essentially give the same two-part definition. (ICAO, the International Civil Aviation Organization, first adopted Airworthiness of Aircraft standards (Annex 8) in 1949. —Ed.)
So, to be airworthy, the plane must conform to its type design as set forth by the manufacturer or as properly modified with an STC or a field approval, and it must be safe for operation. This article addresses the first requirement.
Repairs must be made to certain specifications for an aircraft to adhere to the type design and thus remain airworthy. Changes that constitute a major repair need to be done with approved data. “Approved data” can be in accordance with FAA literature such as Advisory Circular 43.13-1B, the manufacturer’s structural repair manual or another FAA-approved source.
Diving into a TCDS
The starting point for determining whether an aircraft conforms to its type design is the TCDS. This article is limited to examining this important document. A TCDS can be just a few pages or it can be a very lengthy document.
As an example, we will look at the TCDS for the Piper PA-28 series. (See Resources for a link to the FAA Regulatory and Guidance Library, where you can access the TCDS database. —Ed.)
A TCDS is generally divided into four parts. The first part is the specifications for each different model. The second is titled “Data pertinent to all models.” The third section is: “Equipment.” The fourth section is the notes.
All the PA-28 series share the same TCDS. There are 22 individual models covered by TCDS 2A13. The format for the specifications of each model is pretty standard. (See Part 01, Page 23.) The heading tells you Piper’s designation for the model—in this case, PA-28R-200—and the serial number range covered. This happens to be the Arrow II.
Because it differed sufficiently from the previous years, the Arrow II got a new model specification. The changes made from the previous model are also listed in the header.
Of particular interest are the engine and propeller options available. Most owners and many mechanics don’t realize that you can change between TCDS-listed propellers or engines without an STC or field approval. If the option is listed in the TCDS, then it is already approved—and the most that might be necessary is to obtain the installation drawing, if different, from Piper.
The next section contains the data that applies to all models of the PA-28. (See Part 02, Page 24.) Of most significance is the certification basis, which in the case of the PA-28, is different for each model, notwithstanding that the list is in the section that supposedly applies to all models.
In addition to listing the regulations forming the basis of certification, it will also give the amendment date. For the PA-28, most are a mixture of CAR 3 and FAR Part 23.
While all PA-28 aircraft are basically CAR 3 aircraft—even ones built today—the more recent the model, the more additional FAR Part 23 requirements have been added. As the models were produced over the years and especially when changes were made, the FAA would often impose additional requirements. That is how a CAR 3 aircraft might have some FAR Part 23 sections required as well.
Many owners and pilots are not aware that there are two bodies of certification regulations that apply to common GA aircraft. Even many mechanics are really only aware of FAR Part 23, and may incorrectly assume that it applies to all aircraft. I have seen more than one maintenance bill for fixing something to comply with the wrong regulation.
A common example is the requirement for the level of fireproofing of seat covering material. The older certification regulation is Civil Air Regulation Part 3, abbreviated CAR 3. In general, CAR 3 does not require burn certifications. Here’s why you must read carefully: the section of FAR 23 that requires burn certification has been added to the basis of some aircraft designs that were originally all CAR 3.
It is good to know what actually applies to your model and serial number so that you can understand whether the maintenance personnel are applying the correct standards during annual inspection or repairs.
The next section pertains to the equipment. (See Part 03, Page 24.) For older aircraft that use Aircraft Specifications instead of a TCDS (like the PA-24 Comanche series), there is a list of individual pieces of equipment, engine options, etc. This can be detailed and require some level of approval to deviate from what is listed. While usually a PMA part or STC will cover that requirement, occasionally it requires a field approval.
Also in this equipment section is a listing of the AFM/POH required to be in the aircraft. It is worth checking to make sure you have the correct AFM/POH, as it is not uncommon to find them missing and some generic pilot’s guide in its place.
Lastly comes the notes. (See Part 04, Page 24.) The notes can cover a wide range of topics, some germane to a particular model and some more generally applicable. Important ones for the IA and owner are those dealing with required placards. You would probably not be shocked at the number of placards that disappear over the years.
Why is this information important?
For the owner, the TCDS for their aircraft is worth reading through at least once.
It is also a source of good information when researching a model to buy. For example, sales ads often misstate the model year, believing that model years start January 1. Like in the auto industry, the beginning of a model year can vary, but is usually sometime in the fall.
Knowing what the basis of airworthiness is for your aircraft better prepares you to understand the requirements to be a more active participant in the care and feeding of the plane.
Kristin Winter has been an airport rat for almost four decades. She holds an ATP-SE/ME rating and is a CFIAIM, AGI, IGI. In addition, Winter is an A&P/IA. She has over 8,000 hours, of which about 1,000 are in the Twin Comanche and another 1,000 in the Navajo series. She owns and operates a 1969 C model Twinkie affectionately known as Maggie. She is a recognized authority on Piper Comanche aircraft. Currently she is serving as Director of Operations for a commuter airline in Southeastern Alaska. Send questions or comments to editor@www.piperflyer.com.
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