Module 11.17_b1_rev 00.pdf

Module 11 – AIRCRAFT AERODYNAMICS AND STRUCTURES Sub Module 11.17 – WATER AND WASTE SYSTEMS

CATEGORY B1 - MECHANICAL

MODULE 11 SUB MODULE 11.17 WATER AND WASTE (ATA 38)

Rev. 00 Oct 2006

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Module 11 – AIRCRAFT AERODYNAMICS AND STRUCTURES Sub Module 11.17 – WATER AND WASTE SYSTEMS

CATEGORY B1 - MECHANICAL Table of Contents

Page

Table of Contents

Page

Introduction ................................................................................... 2

Removable Toilet Assemblies ..................................................... 28

Potable Water Systems ................................................................ 2

Liquid Flush Toilets ..................................................................... 28

Pressure Control........................................................................... 4

Operation .................................................................................... 30

Water System Distribution ............................................................ 4

Vacuum Toilets ........................................................................... 34

Water Heating............................................................................... 6

Vacuum Toilet Components........................................................ 34

Waste Water Collection and Drainage.......................................... 8

Vacuum Toilet Operation ............................................................ 36

Quantity Indication ...................................................................... 10

Waste Tanks ............................................................................... 38

Replenishment / Servicing .......................................................... 12

Toilet Servicing............................................................................ 40

Potable Water System Maintenance Practices ........................... 14

Special Features ......................................................................... 42

Sanitizing of Water Tanks........................................................... 14

Toilet Safety and Health Precautions .......................................... 42

Cleaning of Waste Water Lines .................................................. 14

Maintenance Practices................................................................ 44

Sampling of The Water System .................................................. 16

Cleaning of Waste Lines ............................................................. 44

Potable Water Systems Examples.............................................. 18

Disinfection of The Waste Tanks................................................. 45

Lockheed L-1011 Potable Water System ................................... 18 Boeing 757 Potable Water System ............................................. 22 Introduction ................................................................................. 26 Aircraft Toilets............................................................................. 26

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“The training notes and diagrams are compiled by SriLankan Technical Training and although comprehensive in detail, they are intended for use only with a Course of instruction. When compiled, they are as up to date as possible, and amendments to the training notes and diagrams will NOT be issued”.

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CATEGORY B1 - MECHANICAL

The purpose of the potable water system is to supply water for drinking to the galleys and hot and cold water to the washbasins in the toilets for use by the passengers and crew.

The potable water tank is stored under the passenger floor in a cradle type structure; the tank is constructed of fiberglass with metal bands bonded into the fiberglass, these bands act as reinforcement for the tank and as a means of supporting it in the cradle. Some older aircraft use stainless steel potable water tanks.

The potable water system allows several galleys and toilets to be fed from a single tank, so reducing the servicing time for replenishment. If vacuum toilets are fitted they are flushed using water from the potable water system.

If the aircraft operates in cold climates it may be fitted with an electric heater blanket to prevent the contents from freezing. The quantity of water required will depend on the number of passengers carried and the range of the aircraft.

POTABLE WATER SYSTEMS

Various pipelines are connected to the tank components such as the: -

INTRODUCTION

The major components in the potable water system are: -

-

tank drain,

-

a tank for storing the potable water,

-

fill connection,

-

an air pressure system to force the water from the tank,

-

overflow connection (with stand pipe),

-

distribution lines to deliver the water to the galleys and lavatories,

-

air pressure connection,

-

supply lines (to galleys and lavatories).

-

a filling system for tank replenishment through an exterior service panel,

-

a quantity indication system,

-

valves to drain the water from the system.

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A quantity transmitter system is installed to indicate the tank's contents; panels on the ends of the tank enable interior examinations and inspections to be carried out.

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Water Reservoir

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Module 11 – AIRCRAFT AERODYNAMICS AND STRUCTURES Sub Module 11.17 – WATER AND WASTE SYSTEMS

CATEGORY B1 - MECHANICAL PRESSURE CONTROL

WATER SYSTEM DISTRIBUTION

The water tank pressurization system provides air pressure into the tank to force the water up to the distribution line. The pressurized air is normally supplied by the aircraft's pneumatic system, but some types of aircraft also use an electric compressor, which will automatically start when the pneumatic pressure falls below a predetermined pressure.

A main water distribution line is taken from the tank and is routed up into the cabin ceiling area above the ceiling trim, from their individual supply lines go to the toilets and galleys. The distribution lines are usually flexible tubing enclosed in an aluminum shroud. The flexible tube is normally reinforced with fiber covering to prevent it from breaking due to freezing. The outer shroud prevents a leaking water line from dripping onto the ceiling panels and subsequently onto the passengers. The shroud will conduct any leaking water to the lower fuselage area via shroud drain tubes, where it can drain out of the fuselage via the lower fuselage drains.

The pressurized air passes through the following components before entering the water tank: -

filter, this normally uses a 'throwaway' paper element,

-

pressure regulator, this reduces and controls the air pressure to about 30 psi,

-

a pressure relief valve, which prevents the over pressurization of the tank should the regulator malfunction.

A quick disconnect fitting is located above each toilet and galley to enable the supply line to be disconnected from the toilet or galley when it has to be removed.

These components are usually located around the tank assembly.

A water shutoff valve is installed at each galley and lavatory to isolate the galleys and lavatories from the potable water system in case of a maintenance or operational need.

On aircraft using a compressor a riser loop or plumber's loop is incorporated to prevent water entering the compressor, the top of the loop is higher than the distribution ducting, therefore water will always go to the distribution lines first. A pressure switch in the air pressurization line will start or stop the compressor as the tank pressure varies. If a compressor is not fitted or for test purposes then an air valve (Schrader) can be fitted onto the ground-replenishing panel to enable the tank to be pressurized whilst the pneumatic system is unpowered.

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Distribution system

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A core plug type pressure relief valve in the water heater is designed to relieve pressures above a specific value (approx 140 psi). The primary purpose of the relief valve is to relieve excessive pressure should the heater overheat due to a malfunction of the cycling switch or overheat switch.

WATER HEATING A water heater with a capacity of about 3 pints is installed under each lavatory sink in the supply plumbing to the hot water tap, and is mounted to the side of the cabinet on brackets. The heater contains electrical elements inserted in the bottom of the tank. On the side of the tank is: -

a warning light,

-

a control switch,

-

an overheat reset switch,

-

a relief valve.

If the water heater requires replacement it can be isolated from the potable water system by the lavatory water shutoff valve.

Normally the heater switch will be 'ON' and the light will illuminate, a cycling switch in the bottom of the water heater will regulate the water temperature to about 125oF. As this temperature is achieved the switch will open but the light remains 'ON' (see Fig. b on the next page). If a malfunction of this switch occurs and the temperature of the water exceeds a pre-determined value, the overheat switch will operate and interrupt the power to the heater and the light. If an overheat occurs the overheat switch must be manually reset by pressing a button on the top of the water heater after a cooling down period. If the reset operation is successful the light will illuminate. The reset switch is normally covered with a rubber 'bubble'.

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FIG. b

FIG. a

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CATEGORY B1 - MECHANICAL WASTE WATER COLLECTION AND DRAINAGE Wastewater collection and drainage vary on different aircraft designs. On some types of aircraft the wastewater from washbasins in the toilets and the galley drains is sent overboard via drain masts under the fuselage. These masts are normally electrically heated to prevent freezing, and the forward motion of the aircraft ensures that the wastewater is finely atomized as it leaves the drain mast. For the aircraft which use the system illustrated in Fig. b the wash basin waste enters the toilet tank and is used to assist the flushing fluid into the rinse ring. NOTE: NO TOILET WASTE EVER LEAVES THE AEROPLANE THROUGH THE DRAIN MASTS. On early types of galley, collection bins were placed under the galley counter (work surface). These containers are removed, emptied, and refitted by the catering staff on each galley restock. On modern aircraft to prevent cabin air leaking overboard through the drain masts FLOAT type drain valves are introduced in the lavatory and galley drains system.

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FIG. a FIG. b

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CATEGORY B1 - MECHANICAL QUANTITY INDICATION

-

an empty tank will illuminate the empty light,

Although some aircraft use a simple sight gauge by the side of the tank to indicate the level of its contents, on large aircraft the tank, which is usually buried in the lower fuselage, requires a sensor fitted in the tank to signal a remote quantity indicator in a location convenient for the cabin staff.

-

a 1/4 full tank will illuminate the empty light and the 1/4 full light,

-

a 1/2 full tank will illuminate the empty light 1/4 and 1/2 full lights,

-

a 3/4 full tank will illuminate the empty light, 1/4, 1/2 and 3/4 full lights,

-

a full tank will illuminate all the lights.

One method of indication is to use a gauge, inside the cabin on the attendant's panel, and a corresponding gauge, which is fed from the same float and electrical transmitter on the replenishment/drain panel. See Fig. a on the next page, for typical quantity gauge indications.

If the button is pushed and no lights illuminate, not even the empty light, then it is an indication that there is no power to the circuit.

Another common method of indicating the tank contents is to use a series of lights controlled by magnetic floats installed in the water tank as shown in Fig. b on the next page. In this case the indicators consist of five lights, which will illuminate when the button on the panel is pressed. There is a light for each of the following quantities: -

empty,

-

1/4 full,

-

1/2 full,

-

3/4 full,

-

full tank.

The transmitter is a probe in the tank. A float, circular in shape, and containing magnets will move up and down the probe following the water level in the tank. Fitted inside the probe are reed switches. As the float, and therefore the magnets, moves up and down the probe, it will open or close each reed switch that it passes. These reed switches are connected to the lights so that: -

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FIG. b FIG. a

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The drain valve handle will allow the potable water tank and the supply lines to be drained through the water drain connection, a pipe is normally fitted to the connection prior to draining to carry away the drained water.

REPLENISHMENT / SERVICING Replenishment of the potable water tank is usually required after each flight, or when the cabin log is annotated for the tank to be refilled. Potable water tanks are normally replenished to their full capacity, however, some airlines with a limited number of passengers on a flight may specify a lesser quantity.

The quantity gauge will only be required for part loads otherwise the tank is replenished until it overflows. Quantity gauges can be in gallons/liters as required by the operator.

Replenishment is carried out at the servicing panel, which is situated on the lower skin of the fuselage.

If cold conditions are encountered whilst the aircraft is parked for long periods (i.e., overnight) it will be necessary to drain the water system to prevent fractures caused by frozen lines. If frost damage is to be avoided all the delivery lines and the tank must be" emptied.

A typical servicing panel is shown in Fig. a on the next page it is normally covered with a flush fitting panel. The servicing panel shown in Fig. a contains: -

a water fill connection,

-

a water drain connection,

-

a water/vent valve handle,

-

a drain valve handle,

-

a quantity gauge.

A vent valve is incorporated to prevent a vapor lock occurring in the wash basin taps by opening the tap lines to atmosphere, later aircraft have self venting taps which will automatically relieve the vapor lock, (American manufactured aircraft refer to taps as faucets). WARNING: IF THE WATER SYSTEM IS DRAINED ENSURE ALL THE WATER HEATERS ARE TURNED OFF. On modern aircraft for water tank-servicing quantity pre-selection via a panel located in the cabin is available. This is made possible by automatic closure of fill valves when selected quantity is reached. This optimizes aircraft performance and eases servicing of aircraft.

The water fill connection, under a dirt excluder cap, is where the potable water rig is plugged in to replenish the tank; it is a standard size coupling. When the tank is at its full capacity the water flows up a stack pipe in the tank and overflows through the overflow connection onto the ground, which is remote from the panel. To enable the tank to be vented of pressurizing air and to open the fill valve in the tank, the water/vent handle is pulled. If the aircraft has an electrical compressor, pulling this handle will also shut off the compressor while the tank is being vented. (See Fig. b on the next page).

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FIG. a

FIG. b

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Once the system has been refilled to overflow,

POTABLE WATER SYSTEM MAINTENANCE PRACTICES It should always be remembered that potable water systems are for human consumption, and therefore strict hygiene precautions should be exercised at all times.

-

close the fill vent valve.

-

leave the solution in the system for the specified time (usually 1 hour),

-

open all wash basin and galley taps until the solution flows through,

-

drain off the chlorine solution,

-

refill and drain with clean drinking water testing the tap outflow until the water no longer tastes of chlorine (this fill and drain operation to remove the chlorine taste, may need to be repeated three or four times).

Basic procedures are as follows: -

-

finally, replace the charcoal filters (if fitted),

-

drain the water system, turn off water heaters,

-

replenish the water system,

-

remove any water filter cartridges (if fitted),

-

turn on the water heaters.

-

charcoal filters are sometimes fitted under the toilet washbasin.

Always put on rubber gloves, goggles and protective clothes to prevent infection during this work.

-

close all valves and refit filter cases,

Obey the manufacturers instructions when you use special materials, as they could be harmful.

Whenever supply lines are disconnected for maintenance they must be immediately blanked to prevent the ingress of dirt. If the aircraft has been left standing for excessive periods, or if complaints are received of foul tasting water the system will have to be disinfected and sterilized. This action is laid out in the Maintenance Manual in Chapter 38 (Water/Waste). Water carts should always be operated at the specified pressure. SANITIZING OF WATER TANKS

Replenish the water system with a chlorine solution; this can be achieved by one of three methods: -

Do not get the water with the disinfectant solution on your skin or in your eyes.

A concentrated chlorine solution may be introduced first and then diluted by adding clean water.

Put a guard around the water faucet outlet to prevent spray from the solution getting on adjacent surfaces.

Chlorine may be mixed with clean water and then pumped into the system.

CLEANING OF WASTE WATER LINES It is a good practice to clean the wastewater drains (overboard drains) at frequent intervals to prevent drain blockage during operations. A procedure commonly used is described below. Manufacturers instructions must be followed always if applicable.

Chlorine can be added as the system is being filled.

NOTE: Do not add more chlorine than is directed as the water system will then taste of chlorine.

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Put the one end of the drain hose equipped with a shut off valve in drain line of each drain mast.

-

Ensure that all connections of the waste water system are tightened. If the connections are loose liquid will flow into the lower fuselage.

-

Put the other end of the drain hose assemblies in a container.

-

Close the shutoff valves on the drain hose assemblies.

-

Make a solution of vinegar and water (mix 10 l of vinegar with 190 1 of water).

-

Pour the mixture or approved cleaning material slowly into the most forward washbasin(s) connected to the drain mast(s) until it is full.

-

Leave the mixture in the wastewater lines for about 1 hour.

-

Then, open the shutoff valves on the drain hose assemblies and drain the mixture from the lines.

-

Flush each wastewater drain with clean water.

-

When the flow of water has stopped, remove the drain hose assemblies from the drain masts.

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CATEGORY B1 - MECHANICAL SAMPLING OF THE WATER SYSTEM

Germs

It is necessary for an airline to test the quality of water at intervals recommended by the manufacturer or as mandated by the aviation authorities. One must always follow instructions of the manufacturer a general guide to accomplish this task is given below.

Max. Allowed quantity milliliter/Usfl. Oz.

No. of germs increase at 20 1000 /1 ml deg.C (68 deg.F) for 48 hours 1000/0.034Usfl.oz.

Make sure that the equipment you use for this procedure is clean and Approved for the potable water system. If not it can cause contamination of the potable water system.

No of germs increase at 36 100/1ml deg.C (96.8 deg.F) for 100/0.034Usfl. oz. 48hours

Only qualified persons are permitted to take samples.

Table 1

Get samples from the water faucet at these locations: -

at a galley,

-

at a lavatory.

Germ increase rate Echerichia Coli

0/100 ml 0/3.38 Usfl.oz.

Coliform Bacteria

0/100 ml 0/3.38 Usfl.oz.

It is generally recommended to get the two samples at the farthest point from the potable-water tank. Apply a disinfectant to the outlet of the water faucet with a -spray gun or Soak a lint-free cloth with disinfectants and clean the outer surface of the Water faucet and wait for approximately 1 minute. Use sterile rubber gloves.

Table 2

Position the sterile glass sample bottle in front of the lavatory waterfaucet outlet, before you operate the faucet. Carefully operate the water faucet, and then fill the clean sterile glass sample bottles with water. Seal the glass sample bottles and make sure that no contamination goes into the bottles. Put a tag on the glass sampling bottles. Write down the aircraft registration, the system, the location, the date and the time on the tag. Send all the water sample bottles to a hygienic institute for analysis. Listed below is a typical water analysis table wherever applicable the national standards should be adapted. Sampling should be carried out at the source, water bowser and the aircraft outlets.

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Module 11 – AIRCRAFT AERODYNAMICS AND STRUCTURES Sub Module 11.17 – WATER AND WASTE SYSTEMS

CATEGORY B1 - MECHANICAL STUDENT NOTES

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distribution lines to permit isolation of galley facilities for maintenance purposes.

POTABLE WATER SYSTEMS EXAMPLES LOCKHEED L-1011 POTABLE WATER SYSTEM

A 3/4" fill connection at the water service panel provides for attachment of a water supply line from ground servicing equipment. Water enters the tank through the open fill/overflow valve, which can be operated remotely at the service panel through a remote control cable, or directly at the valve by the valve handle. When the tank water level reaches the standpipe, overflow water returns to the service cart via the overflow line. When closed the fill/overflow valve enables pressurization by interconnecting the fill port/line with the standpipe/overflow line.

The potable water system, shown in Figure a, distributes drinkable water to lavatory sinks, drinking fountains and coffee makers in the galleys. Chlorinated potable water is stored in a fiberglass 150-gallon tank located in the lower galley sidewall area. Tank quantity, which varies between airlines, is determined by the length of a standpipe in the overflow line, as shown in Figure b The air space above the water level is pressurized through the air supply port by two on-board compressors, illustrated in Figure c, or by a ground air source connected at the service panel. Compressor output passes through position indicating check valves, which monitor the output pressure and cause annunciators at the flight station to illuminate if a 5-psi differential is sensed. Air then enters the tank through a screen filter, relief valve, and check valve. The filter contains a red indicator, which is displayed when the filter is 80% clogged.

The normally closed drain valve can be opened by operating its handle at the service panel. When the drain valve and supply shutoff valves are open. The entire system can be drained to a holding cart attached to the overflow/drain connection. The system must be drained if the aircraft is going to be parked without electrical power in below freezing weather for any length of time.

Compressor control switches monitor pressure in the tank to turn on the associated compressor when tank pressure is less than 30 psi, and turn off the compressor when tank pressure reaches 35 psi. The air is directed to the tank through a 35-psi regulator and a check valve. If both compressors are inoperative, water can be made available to the user system by half filling the tank with water and pressurizing the remaining air space from a ground source. On demand, water under pressure exits the tank through an outlet at the lower center, which is plumbed, to all using facilities. The material composition of most distribution lines is corrosion resistant steel; however, titanium, Monel and flexible Teflon© hoses are used in some areas. To prevent freezing, some distribution lines are heated by wrap-around heater blankets; heater jackets protect the fill/overflow valve and the drain valve. Two manually operated shutoff valves are located in the

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FIG. a

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FIG. b

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FIG. c

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Although some of the distribution lines are heated, they are fabricated of materials that will sustain freezing without rupture or permanent distortion. System pressure is maintained automatically and is designed so that system pressure shall not drop below 10 psig with one lavatory faucet open for full flow.

BOEING 757 POTABLE WATER SYSTEM The major sub-systems of the potable water system are distribution, stowage, pressurization, quantity indication and fill/drain (servicing). The distribution system consists of lines that extend from the stowage tank to all the lavatories and galleys.

The water pressurization system interfaces with the left pneumatic distribution system. When pressurized, the left pneumatic distribution system provides air to pressurize the water system.

The water tank shown in Figure a is filled with potable water from a ground cart through an exterior service panel. The tank is pressurized by an electric driven compressor or the engine bleed pneumatic manifold. Once pressurized, the water is forced from the tank through distribution lines to the galleys and lavatories. In the lavatories, some of the water is diverted through an electric water heater before being delivered to the hot water faucets. The water heater, located under the washbasin in each lavatory. consists of a one and one-half quart cylindrical tank containing three 140 watt heating elements to heat the water, and a cycling thermal switch which regulates the water temperature to approximately 125°F. (52°C). The water distribution system shown in Figure b is located below the passenger compartment floor for the aft galley complex and above the passenger compartment ceiling for all the lavatories and forward galley complex. Waste water from the galleys and from the lavatory sinks is directed overboard through forward and aft drain masts. All supply and drain lines below the level of the passenger floor are protected from freezing by the use of heater tape. The drain masts are also electrically heated. The quantity indication system uses a transmitter located on the tank and indicators located on the servicing panel and in the forward galley area. All components of the water system are constructed of corrosion resistant materials suitable for use with superchlorinated water.

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FIG. a

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FIG. b

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CATEGORY B1 - MECHANICAL STUDENT NOTES

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CATEGORY B1 - MECHANICAL INTRODUCTION

The three types of toilet are: -

The provision of aircraft toilets is an essential requirement for any aircraft carrying passengers over long distances. Without toilet facilities an aircraft's range would be much reduced. Although considered somewhat of a joke, aircraft toilets must be maintained and serviced with care, there is no need for a toilet or its compartment to give off smells if it is properly maintained. The passengers' comfort and health must be protected. It is a sign of the airline's diligence if the toilets are working correctly, and they are clean and odor free.

-

removable toilet assembly,

-

liquid flush type,

-

vacuum toilet assembly.

AIRCRAFT TOILETS There are three types of toilet fitted to aircraft. The type used will depend upon the number of passengers the aircraft can carry, and also the age of the aircraft. In all cases it is essential that the relevant health precautions be observed whenever the toilet is serviced. Due to the nature of the fluids carried in the toilet, protection must also be given to the structure of the aircraft to protect it from corrosion caused by these fluids.

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PAGE INTENTIONALLY LEFT BLANK

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CATEGORY B1 - MECHANICAL REMOVABLE TOILET ASSEMBLIES

LIQUID FLUSH TOILETS

The removable, or carry out toilet is the simplest type of aircraft toilet. This type of waste storage device is often called an Elsan toilet, and is simply a storage bin, which is filled with a strong chemical deodorant. A seat is fitted to the top rim of the bin and when installed in the aircraft the bin is covered by a decorative laminate material.

Liquid flush toilets are the most common type of toilet found in passenger aircraft, each toilet is completely self contained, having its waste collection tank mounted directly below the toilet bowl, as shown in Figure on the next page. The toilet bowl and the top of the waste tank are normally covered by a decorative laminate shroud, which also contains the toilet seat and cover. The waste tanks are shaped to fit into the structure of the aircraft and attached to the structure by tie-rods. Directly below the waste tank is a drain fitting.

After the toilet has been used, the bin is removed complete with its contents from the aircraft and the contents are disposed of in an approved dumping site. The storage bin is refilled with the correct amount of disinfectant and replaced in the aircraft, and recovered with the decorative shroud.

The toilet bowl is constructed of stainless steel and the tank units can be of stainless steel or fiberglass laminate. The tank capacity will vary depending on the number of passengers carried and the number of toilets fitted to the aircraft; the usual capacity is 20 gallons.

Most removable toilet assemblies are secured by a quick release method of attachment such as pip-pins to facilitate removal and fitting. The carry out toilet is usually fitted to the smaller types of aircraft that operate over short ranges.

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The tanks are filled with a precharge of a strong chemical which is a disinfectant, dye and deodorant of about 3 gallons, this will enable the toilet to be used about 100 times, after which the toilet should be emptied, cleansed and recharged.

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Toilet assy

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CATEGORY B1 - MECHANICAL Figure on the next page shows the equipment that is fitted to the toilet tank and includes the: -

motor and pump,

-

filter,

-

hinged separator,

-

rinse ring,

-

flush line,

-

related tubing,

-

drain valve.

OPERATION The toilet is an electrically powered flushing unit. It collects waste material in the toilet tank, disinfects, deodorizes, dyes and separates the liquids in the waste and uses these liquids for flushing purposes. Toilet flushing is initiated by pushing the toilet flush button; this energizes an electric timer which runs the motor in the waste tank for a 10 second cycle. The motor is attached to a pump and a mechanical self-cleaning filter. The pump impeller draws liquid through the rotating filter and pumps it through a flush ring around the top of the toilet bowl with a swirling action. This action carries the deposits into the waste tank by opening the hinged separator. At the end of the 10-second cycle the motor stops and rearms itself ready for the next operation. On the next operation the motor will reverse its direction to prevent the rotating filter becoming entangled with non-decomposable waste

The other items required for toilet operation not fitted to the tank are: -

flush handle,

-

timer.

These items are found on the cabinet above the toilet bowl attached to the decorative laminate.

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Typical Flush lavatory

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driven by the motor, rotates with the pump. A stationary knife blade is placed adjacent to the wire mesh to keep the exterior surface clear of waste. This type of filter does not break down the solid waste into liquid.

FLUSHING COMPONENTS (Refer to Fig) The toilet bowl is mounted on the top of the waste tank; it is manufactured of stainless steel and is highly polished to enable the waste to be easily flushed off its surface. The lower part of the bowl is closed off by a hinged separator which is very lightly sprung loaded closed, this separator acts as a sight trap so the waste is covered from the passengers view and also prevents splash back of the strong chemical during use.

A flush line, which is a perforated tube, is placed around the top of the waste tank, its purpose is to clean the sides of the tank whenever replenishment of the chemical takes place through the ground flush line. A tube enters the waste tank from the toilet bowl, as the toilet sink also drains its wastewater into the waste tank. A vent to atmosphere via a venturi acts as a choke, to limit the outflow of cabin air when the aircraft is pressurized. The vent from the cabin and the atmosphere vent ensure that any odors produced by the waste tank are exhausted overboard.

On the top of the waste tank a reversible three phase 115 Volt a.c. motor is fitted, this assembly drives both the rotating filter and an impeller to pump the flushing fluid to the flush ring. The pump is selfpriming and fitted with a non-corrodible carbon rotor. The toilet flush motor and pump is removed as a complete unit.

A drain valve spring loaded closed, can be opened to allow the waste tank to be emptied via a 4-inch diameter pipe to a standard Roylin connection on a toilet-servicing vehicle. Some aircraft also have lavatory floor drains to allow any liquid spilled on the floor covering to be drained during toilet servicing. Toilet servicing will be discussed later in this sub module.

The filter assembly can be of two types: -

disc filter,

-

filter basket.

DISC FILTER This consists of a stack of flat wheel shaped discs, each disc being separated by a spacer. The thickness of the spacer holding the discs apart determines the degree of filtration. A stationary knife blade is mounted beside the disc stack, and the blade extends into the slots created by the spacers. When the filter is rotated by the motor all the waste is combed through the slots by the cleaner blades, and it is then broken down into liquid waste. This type of filter will break down the waste particles to 300 microns. FILTER BASKET The filter basket surrounds the pump inlet, it is fitted to prevent the solid waste entering the flush ring, the basket (shown in Fig. ) that is gear

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Typical Flush lavatory

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VACUUM TOILET COMPONENTS

VACUUM TOILETS

The components of a typical vacuum toilet are shown in Fig.

On an aircraft fitted with a number of liquid flush toilets there were two major problems, e.g., the corrosion risk and the time taken to drain and replenish each individual toilet. Aircraft fitted with vacuum toilets overcome these problems by having dry toilet assemblies located at convenient points around the passenger cabin and connected to a centralized storage tank by pipelines. A typical vacuum toilet assembly is shown in Figure on the next page.

TOILET BOWL The toilet bowl is manufactured from stainless steel; some manufacturers coat the bowl with Teflon to give it a 'non-stick' effect. A rinse ring around the top of the bowl allows a supply of clean flushing water to clean the bowl after use. FLUSH CONTROL

The vacuum toilet uses a waste container that has a negative pressure inside it, (vacuum). When the remote toilet bowl is flushed a valve opens and the waste is sucked down the pipeline into the storage tank. Water is used for rinsing the bowl but vacuum toilets use clean water from the drinking water tank, this water once used also goes to the waste tank.

The flush control contains a vacuum operated solenoid controlled valve, which is opened for flushing. It can be closed by a manual shut off lever should the valve malfunction, thus preventing a permanent leak of cabin pressure to atmosphere.

On large aircraft with many toilets two waste tanks are used, a number of toilet bowls using one tank the remaining remote toilets using the other tank. This arrangement ensures that if one tank is full or not working, the rest of the toilets using the remaining tank will still be operative.

WATER CONTROL VALVE The water control valve is a solenoid-operated valve that opens when the toilet is flushed to put a predetermined amount of water into the flush ring. This valve can also be manually shut in case of a leak of water into the cabin, or when the toilet assembly is removed.

Whilst the aircraft is flying at altitude a differential pressure exists between the cabin and the ambient conditions, this differential pressure can be used to evacuate the air from the tanks. When the aircraft is at low altitudes or on the ground, vacuum blowers are used to pump the air from the storage tanks thus creating a vacuum.

TIMING MODULE The timing module sequences the flush cycle, it is activated by the flush handle. VACUUM BREAKER The vacuum breaker is in the rinse water line between the rinse ring in the toilet bowl and the water valve. It prevents water being drawn back into the drinking water system from the rinse ring.

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Vacuum Lavatory

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CATEGORY B1 - MECHANICAL VACUUM TOILET OPERATION Consider Fig. a adjacent and Fig. b on the next page. When the flush handle is operated the cycle is started: -

if the aircraft is at low altitude (below 16,000 ft) the vacuum blowers are turned on.

-

one second later the water valve is opened and pumps a small amount (6 to 8 ounces) of water to the rinse ring to clean the toilet bowl.

-

the flush valve solenoid is energized, and the valve is opened using vacuum power. The valve stays open for four seconds to allow the waste to be sucked into the waste tank.

-

after the cycle is completed the vacuum blowers are switched off, and the timer returns to the start ready for the next cycle as shown in Fig. a.

FIG. a

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FIG. b

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CATEGORY B1 - MECHANICAL WASTE TANKS

WASTE LINE CONNECTORS

The storage tanks are situated over a common drain point. They are manufactured from stainless steel with a jacket of fiberglass. Mountings are fabricated into the tank, and the tanks are mounted into a cradle, which is held onto the aircraft structure by support struts, (see Fig. a).

These are the input from the toilet assemblies into the waste tanks. LEVEL SENSORS These are fitted to the top of each tank to prevent it over filling. The level sensor when operated illuminates a light on a cabin attendant's panel to indicate which toilets are not functioning.

Into the top of the tanks are mounted the connections for toilet operation: -

waste line connections,

-

level sensors,

-

vacuum blower connection,

-

differential pressure connection,

-

rinse fittings,

-

liquid separator.

VACUUM BLOWER AND DIFFERENTIAL CONNECTIONS They provide the tank with a negative pressure source, which source is used depends on the altitude at which the aircraft is flying. RINSE FITTINGS These direct a jet of cleaning fluid from a connection on the ground service panel to clean the level sensors and the inside of the storage tank. LIQUID SEPARATOR

These are shown in Fig. b.

This filter prevents the contents of the tank, particularly liquids, from entering the vacuum source lines during aircraft maneuvers.

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FIG. b

FIG. a

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TOILET SERVICING

VACUUM BLOWERS

Toilets are emptied from a toilet servicing point, which is usually on the underside of the fuselage (Fig. b on the next page). A toilet truck with a hose and connection is fitted to the drain point on the aircraft, the toilet vehicle's tank is then evacuated and a drain valve is opened in the drain tube of the toilet. The waste is sucked into the vehicle's tank from the toilet storage tank.

The vacuum blowers are mounted on the aircraft structure close to the top of the storage tanks; they are connected to the tanks by flexible rubber hoses. (See Fig. a on the next page). The blowers are powerful centrifugal compressors that evacuate the tanks, and are protected by thermal switches to prevent motor overheat. The blowers are controlled by the flush switches in the toilets and by aneroid switches, which will automatically start the motor when the toilets are flushed and the aircraft altitude is below 16,000 feet. The motors are cooled by air drawn into the motors via an air filter, which ensures that no foreign objects are drawn into the motor.

Rev. 00 Oct 2006

Also on the toilet vehicle is a tank containing the precharge fluid, this is pumped into the storage tank through the tank flush line (liquid flush toilets). Vacuum toilets require no precharge fluid, except for cleaning the tank at regular intervals through the rinse fittings.

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FIG. b FIG. a

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CATEGORY B1 - MECHANICAL SPECIAL FEATURES

TOILET SAFETY AND HEALTH PRECAUTIONS

Many aircraft toilet drainpipe fittings include a safety plug; the plug is made from rubber or plastic material. The fitment of the plug prevents inadvertent drainage of the toilet; it also acts as a second seal. The drain cap is prevented from being closed unless the plug is fitted and the exterior panel will not lie flush if the cap is not secured. See figure on next page.

The following notes relate to toilets in general, for specific precautions you should refer to the aircraft's Maintenance Manual {Chapter 38, Water -Waste). -

on completion of maintenance of toilet systems you should clean all the tools used.

-

wash your hands with soap and water when you complete work on the waste system especially before eating or smoking.

-

do not run the flush motor if the toilet tank is empty as overheating could occur.

-

mop up all spilt liquids immediately to prevent corrosion occurring to the aircraft structure.

-

do not drop cigarette ends down the toilet, as many toilet pipelines are plastic.

Always use rubber gloves when you do work on the toilet waste system or on parts that have contamination from the waste system. Do not work on the waste system and the potable water system at the same time to prevent contamination of the potable water system.

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Safety features

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Warm water, will make the cleaning procedure easier. Operate the high-pressure water pump. Slowly push the high-pressure hose into the waste line. If necessary apply common grease to the high-pressure hose. During the cleaning procedure you must flush the toilet periodically to drain the waste line. stop the high-pressure cleaning equipment at specified intervals and drain the waste holding tanks

MAINTENANCE PRACTICES CLEANING OF WASTE LINES Prepare the toilet assemblies. -

Remove the toilet shrouds

-

Close the water shutoff valves in the lavatories.

-

Disinfect the toilet assemblies.

When the spray nozzle does not go further into the waste line:

Put specified amount of approved disinfectants in each toilet assembly of the aircraft and Flush the toilet assemblies.

-

stop the high-pressure water pump,

-

remove the high-pressure hose from the waste line.

Do the procedure for all of the toilets on the aircraft.

Apply disinfectants to the toilet bowl, the flush valves and other contaminated areas.

On completion of the task

if a toilet waste line is blocked, the line must be removed and cleaned before you continuation with this procedure.

-

Remove the ground support and maintenance equipment, the special and standard tools and all other items.

Drain the waste holding tanks, put plastic sheets on the floor of the lavatory and the surrounding area to protect the floor coverings.

-

Clean and dry the work area with lint-free cloths.

-

Install the toilet

-

Examine the toilet connections and the waste lines for leaks.

Disconnect the toilet assemblies from the aircraft Assemble the high-pressure cleaning equipment (VACLAV Cleaner) .The high-pressure cleaning equipment must have: -

a high-pressure water pump-VACLAV Cleaner,

-

a high-pressure hose,

-

a spray nozzle-VACLAV Cleaner

Make sure that the hose does not go into the waste separator. if it does it can cause damage to the waste separator and to the waste holding tank. Put the spray nozzle approximately 1 m into the waste line of the toilet.

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CATEGORY B1 - MECHANICAL CLEANING OF WASTE LINES (Procedure 2) -

Service the waste holding tanks

-

Start the procedure at the most forward lavatory.

-

Flush the toilet assembly.

-

Put specific amount of crushed ice into the toilet assembly. The ice must be crushed, you must not use ice cubes.

-

Put vinegar (10% acetic acid solution) or approved disinfectant) into the toilet and flush the toilet immediately.

-

Flush the toilet about 3 times to rinse the toilet bowl.

Do the procedure for all of the toilets on the aircraft. DISINFECTION OF THE WASTE TANKS Use the toilet service vehicle to fill each waste holding tank with specified amount of approved disinfectants. Make sure that there is no leaks from the toilet drain connections or the fill/rinse connections. Turn off the toilet service vehicle and disconnect the service hoses. Close the caps of the waste drain-line valve and the tank flush connections. Clean

and

Rev. 00 Oct 2006

dry

the

service

panel

area

with

a

clean

cloth.

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The logic control boxes are identical; each contains line-replaceable printed circuit cards, including a separate 12-second flush timer card for each toilet in the subsystem and space for spare timer card storage. Each logic box also contains externally accessible switches and indicator lights for testing motor/pump/filter assemblies.

WASTE SYSTEMS Examples L-1011 WASTE SYSTEM The waste system shown in figure consists of independent forward and aft subsystems which are functionally the same and physically similar. Both installations are self-contained. Recirculating liquid chemical systems, which process and store lavatory toilet waste products. Forward lavatory toilets are served by a 40-gallon waste tank; aft lavatory toilets by an 80-gallon tank.

The waste tank is drained, flushed and filled at the waste service panel. It is gravity drained to a suitable ground holding cart through a manually operated drain valve, and is pressure-flushed / filled through a selfsealing fill / flush port.

Forward and aft service panels contain provisions for draining, flushing and pre-charging the associated tank. The service panels also contain indicating lights for tank liquid level indication.

Fill or flush liquid enters the tank through a fill/flush manifold, which contains six spray nozzles. The nozzles direct flush liquid spray to assure complete cleaning action.

Each tank is pre-charged prior to flight with a dye – deodorant – disinfectant (3D) chemical flushing liquid; the forward tank with 15 gallons, the aft with 20 gallons. In each system, pressure for toilet flushing is supplied by three tank-mounted motor/pump/filter assemblies, which operate one at a time in selective rotational sequence. One pump develops sufficient pressure to flush all subsystem toilets simultaneously. The pumps are controlled by solidstate circuitry in a logic control box mounted near the tank.

With the drain valve closed, the tank is pre-charged through the fill/flush port and spray nozzles with a dye-deodorant-disinfectant liquid chemical. The service panel also contains indicating lights for determining the quantity of accumulated waste in the tank.

A flush valve on each toilet in the system is also controlled by the logic box. Flush signals are initiated at each toilet by a flush control lever/switch assembly.

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CATEGORY B1 - MECHANICAL The wastewater panel, shown in figure at the flight engineer station, contains forward and aft pump dial lights for annunciation of pump failure in the associated subsystem. A flush signal is generated when a flush control lever is momentarily pressed. Logic box circuitry opens the associated flush valve and activates the next pump in rotational sequence. At the end of 12 seconds the flush valve is closed and the pump is shut off. Unless it’s operating time is extended through activation of other timers by concurrent flush signals. Waste tank odors are ducted overboard through a vent line, which terminates near the service panel. Air pressure for tank venting can be supplied from one of three sources: cabin pressure, the pneumatic system, or ground air. When the aircraft is pressurized, cabin air passes through the toilets into the waste tank and exhausts overboard through the vent line and outflow control valve. If the cabin is not pressurized, odors are drawn from the tank by a vent air jet pump in the vent line, which can be operated from air pressure supplied by the pneumatic system, or from a ground source through the ground vent air valve at the service panel.

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CATEGORY B1 - MECHANICAL 757 WASTE SYSTEM The waste system shown in Figure provides toilet facilities in each lavatory. The system consists of a toilet assembly in each lavatory; airplane exterior-mounted servicing panels, and the necessary plumbing and hardware for system control, operation and servicing. Each toilet consists of a waste tank and flushing equipment. The lavatory compartments, toilet bowls and waste tanks are vented by the lavatory/galley ventilation system. Servicing is accomplished externally through three service panels.

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CATEGORY B1 - MECHANICAL The toilet/waste assembly, shown in Figure, is a self-contained unit installed in each lavatory. It is installed above the floor of the lavatory and attached to airplane structure with two tie bolts. Initiation of the flush cycle is through a switch and timer located on the lavatory wall. The toilets are serviced from exterior service panels. The toilet tank is constructed of molded Kevlar

and the various components required for operation of the toilet are mounted on the top. These components consist of the toilet bowl with separator, the motorpump-filter assembly, the tank drain valve assembly, the motor driven shutoff valve assembly, fluid level sensor and the tank and toilet bowl vents. The entire unit is covered with an easily removable decorative shroud. The toilet-timer is a self-contained unit mounted with four screws behind the lavatory wall at the back of the toilet. A shaft on the unit extends though the wall and an operating handle is attached to this shaft with a self-locking setscrew. Each time the handle is pressed, power is applied to the control circuitry, starting a solid-state timer and energizing a relay. This will supply 115 VAC power to the flush motor for a period of 10 seconds after which the relay will open.

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Waste tank level is monitored by two level sensors in each waste tank. The sensors are connected to a sensor and logic control module. When a waste tank reaches capacity, the level monitoring system prevents the associated toilets from flushing, and illuminates a LAV INOP light on the attendant's panel. All waste tanks are serviced from one waste service panel.

747-400 TOILET WASTE SYSTEM The 747-400 toilet waste system uses a vacuum system to collect, transport and store toilet waste. The waste system shown in Figure provides toilets throughout the main deck and upper deck passenger cabin. The system uses potable water to flush the toilet bowls, and vacuum (differential pressure) to transport the waste through toilet drain lines to waste tanks in the bulk cargo compartment.

The panel contains a waste drain cap and rinse fittings. The drain cap is opened to provide a connection for ground service equipment. When the drain valves are opened waste tank contents flow out this connection. After draining, the tanks are rinsed with flushing liquid through the rinse fitting on the service panel. The liquid passes through a filter before entering the rinse housing assemblies in the tank. After rinsing, a wet pre-charge may be added to the tanks.

The toilet flushing cycle is controlled by a flush control unit. This unit sequences and times the cycle including the rinse water valve, flush valve, and vacuum blower operation. The vacuum (differential) is created by a vacuum blower at lower altitudes and differential pressure at high altitudes. At altitudes below 16.000 feet (12.000 feet on descent) the vacuum blower is not operating and the blower shutoff valve is closed at high altitudes, the differential pressure between the cabin and ambient provides the vacuum. All air leaving the waste tanks passes through a liquid separator.

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