Airworthiness of Components – the Basics

After having described the overall concept of airworthiness and the general concepts of the airworthiness of aircraft it is certainly time to get into the airworthiness of aircraft components. Only airworthy components (parts) make for an airworthy aircraft, so let’s take a look at what this is all about.

I have started the series on airworthiness posts by a post on the overall and general concept of airworthiness and then, naturally, with an article on the airworthiness of aircraft. What I didn’t really mention in the latter was that the management of an aircraft’s airworthiness is directly associated with the management of the airworthiness of components. This may seem obvious once you’ve read it, but it becomes easy to forget during the everyday hassle of airline airworthiness management.

In one short sentence: in order for an aircraft to be airworthy, all the components installed on that aircraft need to be airworthy as well. But what does it mean for a component or any other part to be airworthy? Let’s take a look into that:

Each component which you’re about to install on an aircraft was either just manufactured (it’s factory new), overhauled, repaired or modified. In other words, you can’t just take them out of a scrapped aircraft or by them on e-bay from JohnAviation1234 (sorry if anyone’s actually using that nickname). All those tasks need to be carried out by an appropriately approved maintenance organization (for the overhauls, repairs and mods) or manufacturing organization if you’re buying it brand new. The way you can tell whether a component has gone through a properly approved company is by means of appropriate certificates which must accompany all components and most parts which you install on your aircraft. The certificates may differ from country to country, but the most common ones are the European EASA Form One certificate and the American FAA 8130-1 certificate. The look almost the same and serve the same purpose – to assure an airworthiness manager that the component in their hands is compliant with (almost) all necessary requirements.

So is that it? I need to make sure there is a Form One or 8130 and we’re set to go?

Well, not quite. If you go back to my post on the airworthiness of aircraft, you will notice that for an airframe, there are several things an airworthiness manager has to consider before accepting an aircraft as being airworthy. These documents include airworthiness directives, service bulletins and maintenance manual entries which apply directly to airworthiness.

Component airworthiness issues are no different in that respect. For aircraft components you will also get airworthiness directives (issued by your civil aviation authority or the authority of the manufacturer of the component with the latter being always a great hassle), you may get service bulletins from the manufacturer and you also get maintenance manuals (known as Component Maintenance Manuals – CMM). Again, they need to be checked to make sure that the component you’re holding in your hands conforms to the newest standards.

Wait, but wasn’t the certificate supposed to assure me of that?

To a certain extent, but not completely. You need to take into account that the certificate may have been issued quite some time ago (you may have bought a brand new component which was sitting on the vendors shelf for 6 months) and this directly influences the airworthiness of components. During the time from the issuance of the certificate until the moment you install the aircraft new airworthiness data may have appeared (for instance, your CAA may have released a new airworthiness directive for that particular component). Which is why an airworthiness department must make sure that all the documents are checked for possible requirements which have not been satisfied when the certificate has been issued.

Apart from that, just like with the airframe, many components have their life limits or time between overhauls which need to be considered at all times and not exceeded to make sure that your part will serve your aircraft for as long as the manufacturer has foreseen with no unnecessary problems. Those also need to be taken into account for the airworthiness of components.