Type certificates and supplemental type certificates — more usually referred to by the acronyms TC and STC, with the latter sometimes called supplementary type certificates — sit at the heart of aircraft certification, but what’s the difference? Who provides TCs and STCs, and what are the nuances in the cases that both are an option? Join us for the latest of our ab initio primer guides!
At the highest level, airworthiness authorities, such as the US Federal Aviation Administration or the European Union Aviation Safety Agency, issue type certificates to aircraft original equipment manufacturers, like Boeing or Airbus for each kind of aircraft they design and produce: the 787 or A350, for example.
A TC “confirms that the aircraft of a new type intended for serial production complies with applicable airworthiness requirements established by the relevant national civil aviation authority,” Nina Schulz, managing director of the Independent Aircraft Modifier Alliance, an industry group that focusses on improving, standardising and harmonising STCs, tells us. “A supplemental type certificate, STC, is a civil aviation authority approved, major modification or repair to an existing type certified aircraft.”
“The main difference between them,” Schulz explains, “is that a TC is issued to a new aircraft type and can only be applied for and issued to the aircraft manufacturer, whereas an STC is issued once the authority has approved to modify an aircraft from its original design.”
STCs have, by and large, been approved independently of each other by certifying regulators, and in many cases independent of the original equipment manufacturer.
As an example, an airline might install an inflight connectivity system onto their aircraft, adding a radome, satellite antenna and wireless access point — plus all the wiring and systems integration — some time after the aircraft’s delivery.
This has led to a certain amount of inconsistency and a lack of commonality: installation of system A vs B, by MRO provider B vs C, on aircraft type D vs E, under the auspices of regulator F vs G.
This could introduce inconsistencies even within an owner-operator airline, but is even more of an issue for lessors, where the business model largely relies on an interchangeable, largely commodified, fleet of aircraft that pass between operators, with minimal differences between airframe.
To solve the problem, IAMA, whose members include Design Organisations and are among the largest STC providers, has been working to harmonise and standardise STCs.
Current certification trends include connectivity, cabin densification and P2F
With a very broad range of inflight connectivity providers, technologies, components and suppliers, getting the Internet to the aircraft is a complex matter.
Here in particular, says IAMA’s Nina Schulz, “one of the biggest challenges for the design and certification of aircraft modifications is the possession and use of Intellectual Property. One key driver of IAMA is establishing a community based and jointly agreed STC standards to create a level playing field with the TC holders.”
This is often referred to as the commercial right to use a technology. Returning to our example of an inflight connectivity system, if Airline X installs a system from a certain provider on an airframe and then later sells that airframe to Airline Y, there is no inherent right for Airline Y to be able to use that system without entering into a commercial arrangement with that provider.
Joern Dahmen, senior director for special engineering services at Lufthansa Technik, tells us that “a growing need for airlines is to receive certified installations including more capable hardware, preferably with better performance, but more important with respect to more flexibility.”
“Due to high costs of hardware and installation downtimes, a certified hardware set should be capable to communicate with a variation of satellite constellations, allowing a change of connectivity contract a lot faster than only after 7–10 years,” Dahmen says. “Lufthansa Technik is working hard to design STC-based solutions supporting such flexibility.”
Also on trend: densifying cabins, particularly those of older aircraft. Dahmen explains that, “in order to improve their economics, some airlines have an interest to try to fit as many seats into their cabins as possible. Here, STC-based modifications can help, for example by modifying or re-arranging galleys and lavatories in a way that they make room for additional rows of seats.”
This is driven by a number of factors. An airline might be installing premium economy cabins and thus opening up the so-called comfort canyon between that class and regular economy. It might be moving larger aircraft onto higher capacity routes, or standardising its subfleets, including previous high-premium subfleets. It might also be revising its projections of the demand market segmentation in the post-COVID period.
“Another interesting upcoming topic is the increased consciousness of the needs of passengers with reduced mobility. This reflects the changing demographics we all observe,” Schulz notes. “Next to this, we see providers offering solutions for lavatories that also respect these special needs.”
Sustainability, particularly around cabins, is also of particular focus. “We will surely observe how the general demand for sustainable solutions will find its way into the retrofit market. It is clear that sustainability cannot be limited to speaking about propulsion,” says Schulz. “Consumers are demanding sustainable solutions also — or even especially — for the aviation industry. We see stunning developments of plant-based materials used for aircraft cabins and are curious how the market will accept and develop these remarkable ideas further.”
Also part of the context: the repercussions of the changing cargo market, with the temporary pandemic-limited STC solutions certified during the worst of COVID-19 coming to an end July 2022. A substantial amount of demand for passenger-to-freighter conversions is forthcoming, demonstrated most recently by Boeing recently announcing it will open two new 767-300BCF conversion lines at GAMECO in Guangzhou.
Digitalisation, in particular, “continues to be a driver for future modification programs. There are multiple examples from sensor-driven collection use and maintenance data, augmented reality application to ease specification and fit checks, digital mock-ups to speed up design processes and AI based simulations,” Schulz explains. “Still, luckily human beings play a vital role in retrofit campaigns. Human interaction is essential, and it will be key for the entire ecosystem to retain talents and ensure sufficient and skilled capacity.”
Author: John Walton
Published 19th July 2022
Photo by Tienko Dima on Unsplash
;
