One of Boeing's smallest airliners, the 737, is made up of 367,000 parts. These parts serve to deliver a safe and comfortable flying experience to passengers, and many play a pivotal role in keeping the plane airborne.
Even though my job mostly boils down to helping companies choose the right cleaning solutions, I'm surprised at how often I come across some very surreal situations. For instance, I once visited a customer site where they were testing critical aviation components.
Walking around the facility, I came to a room where a team of engineers were testing a transponder — the device used to send an electronic signal to air traffic control and other aircraft — that had recently been removed from an aircraft.
As I watched, the team proceeded to call Boeing to alert the manufacturer that they were about to set off the emergency alarm under test conditions and that there was no need to worry about any real danger. It struck me that, were it not for their strict adherence to procedures, the engineers might well have inadvertently caused a distressing false alarm.
This situation demonstrates the exacting standards of the aviation industry. There's a procedure for absolutely everything. Sometimes, these procedures govern obvious things like periodically testing a transponder or deploying the inflatable chute on an aeroplane — only to deflate and replace it for use in an emergency.
On other occasions, the procedures are less obvious, like selecting the right solvent or water-based degreaser to clean soiled parts. Unlike when you are cleaning your house, a single multipurpose cleaner simply won't do. This is one of the reasons why the global industrial cleaning market is estimated to be worth $50.24 billion by 2020 according to MarketsandMarkets.
In fact, the subject of aircraft cleaning is so complex that the World Health Organisation (WHO) has published a magnum opus on the subject, entitled ‘A Guide to Hygiene and Sanitation in Aviation’.
“Cleaning and disinfection on aircraft require special attention, as it is necessary to use agents that are not corrosive or otherwise detrimental to aircraft components,” WHO explains in its book. “For this reason, not all effective cleaning disinfecting agents can be used in the aircraft cabin”, for example.
The demands from the aviation industry take two forms; one consists of regulations and the other consists of the manufacturer's specifications for products that will work safely with its aircraft. Maintenance engineers should consider both sets of demands when choosing the cleaning agent and the cleaning equipment.
There are two regulations that are particularly relevant: EU 1321/2014, which looks at the airworthiness of aircraft and EC 216/2008, which brings together the common rules in the field of civil aviation.
These rules stipulate that when aircraft and their parts are cleaned "The maintenance programme must contain, in particular, maintenance tasks and intervals, especially those that have been specified as mandatory in the instructions for continuing airworthiness," and that "the aircraft must not be operated unless it is released to service by qualified persons or organisations."
Cleaning up your act
Different cleaners can react differently to different grades of aluminium, steel, silicones, plastics and rubber seals, causing wear, etching, or corrosion to the material, something that could potential render an aircraft non-airworthy.
As well as the type of cleaner, the method of cleaning is also critical. Manual hand cleaning, using stiff-bristled brushes can leave microscopic scratches, forcing contaminants deeper inside the component, reducing its lifespan and causing a potential risk to airworthiness.
That's not ideal when you have a high volume of parts to clean. Aircraft maintenance checks are usually carried out at set intervals, and follow a staged process from A-D. At each stage, the aircraft will be towed into a hangar to be cleaned and serviced.
The checks are carried out after anywhere from 500 flight-hours — where routine maintenance might take ten hours to complete — to 50,000 flight hours, where maintenance can last months and involve a complete overhaul and engine rebuilds. The biggest challenges are the volume, variety and complexity of maintenance.
Maintenance engineers are responsible for a variety of tasks such as disassembling the wing section to clean the actuator that controls the flaps, cleaning brakes, engine parts, seats or landing gears, to more complex tasks such as overhauling a Rolls-Royce turbojet engine.
In the work of its Parts Cleaning Innovation Platform, NCH Europe has specialised in solving this problem for many years. The company recognises that cleaning any aircraft requires a two-pronged approach; having the right cleaning agent, and having the right type of cleaning machine that will clean a variety of parts.
As a result, the company has developed a range of solvent and water-based degreasers that work with aviation approved chemistries. Our hydrocarbon-based D60-rated cleaners, for example, offer a high flash-point for reduced flammability and the added benefit of military-spec performance means it is ideal for even the most demanding applications.
Wash and go!
However, having a good cleaning agent is worthless if engineers cannot clean parts effectively. This is why NCH Europe has introduced a full range of parts-cleaning equipment including everything from a basic sink-on-drum manual hydrocarbon cleaner, to fully automatic water-based machines that use high pressure jets to get the cleaning agent into even the most difficult-to-reach areas. At all times the equipment and cleaning agents are meeting the requirements and regulations of the aviation industry.
The largest standard parts cleaning machine that NCH Europe makes is 1.2m wide, about the right size to fit a car engine, and will accommodate parts weighing up to 200kg. We've also built bespoke equipment for companies in the aviation sector based on the frequency, volume and complexity of their cleaning requirements.
Despite the burden of regulatory compliance and manufacturer specifications, cleaning and maintenance in the aviation industry doesn't need to be difficult. By choosing specialised parts-cleaning equipment and combining it with cleaning agents that meet aviation approved chemistries, maintenance engineers can ease the challenge of cleaning, even if, as with the Boeing 737, there's 367,000 parts to get through.