Aircraft lavatory servicing is an important Ground Support Operation that is critical for flight operation. There are old passengers, babies and a lot of times sick passengers traveling onboard which makes aircraft toilets very busy and the lavatory system requires servicing on every flight.

Importance and Scope of Aircraft Lavatory System

The requirement of an adequate lavatory servicing process arises due to the number of people that are onboard in any given flight as well as the time duration for which they remain in air.

Narrow body aircrafts like an Airbus A320 can carry more than 200 passengers while a Code-F aircraft like Airbus A380 can carry more than 500 passengers on board.

An Airbus A320 can fly nonstop for over 7 hours, for example between Bahrain and London Heathrow while A Boeing 777 and Airbus A380 can fly nonstop for over 17 hours on many long haul international routes.

A proper lavatory system is not just a necessity. Many wide body aircrafts have luxury washrooms for their business class passengers and a good lavatory system is part of the experience for such passengers. Airlines often advertise their luxurious washrooms onboard.

Basic Design of Aircraft Lavatory System

In view of all the factors described above that necessitate a fully functional lavatory system, all commercial aircrafts have a specialized system for handling waste.

Picking the design of an Airbus A320 as an example, the toilets are located towards the tail of the aircraft. All wastewater from the toilets is collected in a waste tank, which for a narrow body aircraft like an A320, can be of nearly 200 L capacity.

Drain line and flush line of this waste tank are carried to the lavatory ground service connection port. It is located near the tail of the aircraft and is used by lavatory service equipment to connect and carry out lavatory servicing.

Airbus A320 Waste Tank Illustration (Source: Airbus A320 Manual)

Lavatory Servicing Process

The procedure of lavatory servicing is aimed at simple emptying the waste tank of the aircraft after every flight and also flushing it when required. Moreover, the waste drained from the aircraft needs to be properly disposed at the airport.

The lavatory service port of the aircraft has a drain line used for draining all the waste and a flush line that is used by lavatory service equipment to inject a disinfectant solution for rinsing the waste tank.

Aircraft Lavatory Service Port Illustration. Drain line and Flush line are connected with respective hoses on the lavatory service truck. (Source Images: Airbus A320 Manual & Wikimedia Commons)

The basic process from collection of waste in air to its disposal at the airport comprises following main steps,

  1. Aircraft remains in the air where passengers use the toilets.
  2. All waste is stored in the aircraft’s waste tank as long as the aircraft remains in air.
  3. Aircraft’s waste tank is drained by lavatory service equipment on arrival of the aircraft at the airport.
  4. Lavatory service equipment (generally a truck) services one or more aircrafts in a single go and then dumps the waste in airport sewer line.
  5. Airport sewer line is connected to the city sewer system. In this way, waste from the aircraft is dumped into the city sewer.
Illustration of how lavatory servicing process works for proper waste handling

Types of Aircraft Lavatory Service Equipment

There are two main types of a lavatory service equipment.

  1. Lavatory service truck is the most common type where all equipment components are installed over a truck.
  2. The other type is lavatory service cart in which all components are installed over a cart that is needed to be towed to the desired location by a towing tractor.

All large airports use lavatory service trucks because they can service more aircrafts than a lavatory service cart and they don’t require any external machine such as a towing tractor for their movement.

Lavatory Service Truck (Image Credit: Wikimedia Commons/ Raimond Spekking / CC BY-SA 4.0)
Lavatory Service Cart is simply waste tanks assembled over a cart to be towed to the desired location at the airport.

Basic Design of Lavatory Service Truck

A lavatory service truck is a collection of components installed over a truck chassis. It has two main tanks. One is the waste tank that stores the waste drained from the aircraft. The other is the flush tank that stores the disinfectant liquid (often referred to as the blue water) used for rinsing the aircraft’s waste tank.

Basic Design of a Lavatory Service Truck

Flush tank is installed with a pump used for pumping the blue water into the aircraft’s waste tank for rinsing.

Lavatory service trucks can also be equipped with an aerial platform, that allows the operator to reach aircraft lavatory outlet because on larger aircrafts, the outlet is not reachable without any aid.

Some trucks also have a vacuum system installed with the waste tank that allows faster suction to reduce service time.

Some manufacturers also provide heaters in waste tank and flush tank to avoid the liquids from getting frozen in extremely cold weather on airports that experience sub-zero temperatures.

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