It is comforting to know that the giant Airbus A380 airliner has achieved a test evacuation of 853 passengers and 20 crew in just 80 seconds, but another high-speed evacuation on the aircraft will also make passengers feel more comfortable.

The passenger evacuation was carried out in the dark and only half of the aircraft’s 16 exits were used. Participants did not know which emergency doors and slides would be operating.

The evacuation test was the first to be done on a double-deck plane. It was supervised by the European Aviation and Safety Agency in conjunction with the American Federal Aviation Authority.

The other A380 evacuation success is of more interest to plumbing engineers.

An Airbus factory in Hamburg, Germany, houses a three-story test rig that replicates the A380’s almost 1000m of piping. Its main function is to test the effectiveness of up to 20 toilets that can be installed in the aircraft. The rig can be tilted to simulate flying conditions.

Apart from the usual considerations of flushing, extraction and hygiene, plumbing engineers must deal with the odd objects that somehow find their way into aircraft toilets.

Frank Dohrmann is head of design support and cabin testing at the main German plant. He says passengers would not be too upset if the temperature inside an aircraft varied slightly, but if toilets were jammed they would remember it for years.

“Toilets are very important to airlines,” he says. “Some people put anything down there – towels, spoons, glasses, diapers. They behave as if they were at home.”

A typical A380 configuration accommodates about 550 passengers, but charter companies can specify more than 800 seats. That’s a lot of people wanting to go to the toilet.

Consequently, engineers operating the test rig in Hamburg have done their best to block the toilets – then figure out how to avoid serious problems in flight. One airline is reported to have asked for socks to be stuffed into the test toilets.

Waste pipes from the 20 toilets on the rig are fabricated in clear plastic for observation purposes. The pipes in the aircraft are formed from titanium to reduce weight.

Toilet flushing is achieved by pumping air from the system, creating a part vacuum to evacuate waste to a holding tank in the rear of the aircraft.

The engineers have proudly announced a pipe speed ‘best’ on their test rig of 60m per second, which equates to more than 200kmh (125mph). Such speeds are important – the A380 is 73m (80 yards) in length, so it’s a long way from the front toilets to the holding tank.

In a technical paper for the 25th International Congress of the Aeronautical Sciences late last year, Dr Michael Rempe and Dr Murat Ünlü of Airbus write that cabin systems of modern aircraft are increasingly designed as distributed systems.

With the A380 water/waste system as an example, they show how design and testing methods must cover the entire development process.

The design of aircraft water/waste systems has to reflect several requirements relating to flexibility of the cabin and options such as humidifiers and galley inserts. It also has to meet challenging ‘operational interruption’ targets to ensure market competitiveness.

To cope with such requirements, a basic system architecture of four independent waste sub-systems was selected for the A380.

To support the general mechanical system architecture a corresponding distributed control and monitoring architecture based on a serial communication bus –the controller area network bus (CAN-bus) – was chosen.

The potable water system and the waste system are distributed systems – that is, composed of autonomous local small computers connected by a communications network and equipped with software enabling them to co-ordinate activities and share resources.

There are four CAN-buses for the waste system – one for each side on the aircraft’s main and upper decks.