FIGURE 11-2. Mobile ground power unit (towed).
3. Engine Will Not Start.
The engine will not start within the prescribed time limit. It can be caused by lack of fuel to the engine, insufficient or no electrical power, or malfunctions in the ignition system. If the engine fails to start within the prescribed time, it should be shut down.
In all cases of unsatisfactory starts the fuel and ignition should be turned off. Continue rotating the compressor for approximately 15 seconds to remove accumulated fuel from the engine. If unable to motor (rotate) the engine, allow a 30- second fuel draining period before attempting another start.
ELECTRICAL POWER Ground support electrical power units vary classified as either towed or self-propelled items of equipment.
The towed power units vary in size and range of available power. The smallest units are simply high-capacity batteries used to start light aircraft.
These units are normally mounted on wheels or skids and are equipped with an extra-long electrical line terminated in a suitable plug-in adapter.
Larger units (figure 11-2) are equipped with generators. These units provide a wider range of output power.
Such power units are normally designed to supply constant-current, variable-voltage d.c.
electrical power for starting jet aircraft engines, and constant-voltage direct current for starting reciprocating aircraft engines. This type of vehicle is normally somewhat top-heavy and possesses a large inertia; consequently, it should be towed at restricted speeds, and sharp turns should be avoided.
Self-propelled power units are normally more expensive than the towed units and in most instances supply a wider range of output voltages and frequencies. For example, the self-propelled power unit shown in figure 11-3 is capable of supplying d.c. power in varying amounts, as well as 115/200-volt, 3-phase, 400-cycle a.c. power continuously for 5 minutes.
When using ground electrical power units, it is important to position the unit carefully. It must be positioned to prevent collision with the aircraft being serviced, or others nearby in the event the brakes on the unit fail. It should be parked a full service cable length away from the aircraft being serviced.
All electrical safety precautions should be observed when servicing an aircraft, and a power unit should never be moved when service cables are attached to an aircraft or when the generator system is engaged.
HYDRAULIC POWER Portable hydraulic test stands are manufactured in many sizes and cost ranges. Some have a limited range of operation, while others can be used to perform all the system tests that fixed shop test stands are designed to perform. For example, one particular type of portable test unit can perform the following functions:
1. Drain the aircraft hydraulic system.
2. Filter the aircraft system hydraulic fluid.
FIGURE 11-3. Self-propelled ground power unit.
vides an output of up to 400,000 B.t.u. per hour.
A single engine supplies power to the truck and the air-conditioning equipment. This is accomplished by means of power-takeoffs mounted on an auxiliary transmission. By simple shifting of gear handles in various combinations of positions, an operator can drive the truck, operate the blower only, or operate the blower and the refrigeration equipment. All controls and switches for operation are in the cab.
GROUND SUPPORT AIR START UNITS FIGURE 11-4. Air conditioner and heater unit.
3. Refill the aircraft system with clean, micronically filtered hydraulie fluid.
4. Check performance of aircraft systems and subsystems.
5. Check the aircraft hydraulic systems for internal and external leakage.
This type of portable hydraulic test unit is usually an electrically powered unit. It uses a hydraulic system capable of delivering a variable volume of fluid from zero to approximately 24 gallons per minute at variable pressures up to 3,000 p.s.i.g. The test unit and its components are mounted on a metal base enclosed by a removable top cover. The base is usually mounted on four pneumatic rubber tire wheels. It may be selfpropelled or provided with a tow bar for towing by hand or vehicle.
AIR-CONDITIONING AND HEATING UNITS Mobile air-conditioning and heating units are ground support equipment designed to supply conditioned air to heat or cool aircraft. Such units are capable of delivering a large airflow against static pressure at the end of a flexible duct or into an aircraft. Compared to the air-conditioning capability, the heating capability is normally considered an optional accessory, but in some climates the heating capability is often as useful as the cooling.
Figure 11-4 shows a typical mobile air conditioner and heating unit. This unit is capable of delivering up to 3,500 cu. ft. of cooling air per minute. It is capable of dropping the interior temperature of a large aircraft from 115° F. to approximately 76° F. Its heating capability pro- Air start units provide a supply of compressed air to operate pneumatic starters on turboprop and gas-turbine engines. Air start units may be mounted on trailer units to be towed to the aircraft, or they may be self-propelled units similar to that shown in figure 11-5.
A typical air start unit consists of the following components: A GTC, a high-capacity storage battery, and the necessary fuel, oil and electrical systems, controls, and compressed air lines.
The typical GTC is basically a two-stage centrifugal compressor assembly directly coupled to a radial inward-flow turbine. In addition to compressed bleed air, the compressor supplies compressed air for combustion to drive the turbine wheel. The combustion gas is passed through the combustion chamber to the turbine nozzle assembly. The power extracted by the turbine wheel is transmitted to the compressor, accessory section, and control system components.
FIGURE 11-5. Air start unit.
Quantity meter Pressure gage » Hand pump Filler lie FIGURE 11-6. Pressure oil unit.
PREOILING EQUIPMENT Preoiling reciprocating aircraft engines is usually necessary before starting a new or preserved engine, or one which has been idle for a period of time.
Using a preoiler (see figure 11-6) for reciprocating aircraft engines simplifies the job of preoiling.
Such units supply preheated oil under pressure to the engine to ensure adequate lubrication before starting.
The conditions for preoiling turbine engines are essentially the same as those for reciprocating engines. In addition, if a lubricating oil line fitting has been disconnected on a turbine engine, the engine must be preoiled before starting again. The portable preoiler tank supplies low-pressure oil to the lubrication system of the turbine engine.
AIRCRAFT FUELING Strict fire precautions must be adhered to during the fueling process. Smoking is not permitted in or around an aircraft during fueling. Also, open flames such as oil lanterns, candles, or matches are prohibited. Exposed electric switches, sliprings or commutators, dynamos or motors, spark-producing electrical equipment, or any burning material must not be permitted within 100 feet of an aircraft being fueled or defueled. No lights other than approved explosion-proof lights are permitted within 100 feet of these operations, and no light of any sort may be placed where it can come in contact with spilled fuel. Warning signs should be posted as a precautionary measure.
All aircraft fuels or other combustible liquids accidentally spilled should be immediately removed by washing with water or covered with a foam blanket to prevent ignition, or neutralized by other means. The proper fire authorities must be notified if necessary.
If indications of underground leakage of combustible liquids are discovered, areas must be guarded by appropriate means, and the proper fire authorities must be notified immediately.
It is recommended that aircraft fuel tanks be filled before storing aircraft in hangars, since this leaves no space for explosive vapors to form. This practice is also recommended after each flight to prevent water condensation in fuel tanks.
The fuel tanks should not be filled completely to the top when aircraft are stored in hangars, especially if the outside temperature is cooler than the inside temperature. If it is warmer inside the hangar than outside, fuel in the tanks expands and causes overflow through the fuel tank's venting system, creating a fire hazard.
Nonspark tools must be used when working on any part of a system or unit designed for storing or handling combustible liquids.
Use of leaky tanks or fuel lines is not permitted.
Repairs must be made on discovery, with due regard to the hazard involved.
All fuel is filtered and passes through waterseparating equipment at the tank farm when it is delivered to the mobile refueler; or in the case of island-type refueling stations, as it leaves the supply connections. The mobile refueler also passes the fuel through a system of filters and waterseparating equipment before its delivery to the aircraft. These filters and separators are usually checked in the morning for evidence of dirt and water, and each time thereafter that the mobile refueler is reloaded. When the mobile refueler is loaded, it must sit at least 15 minutes and then have the sumps checked for water before any aircraft are refueled from it.
When using fuel which has been stored in cans or barrels, it must be run through a strainer-funnel before being put into aircraft. This practice is necessary as condensation and rust develop inside cans and barrels.
If a chamois is used to filter the fuel, an increase in the static electricity hazard results from the passage of gasoline through the material. The chamois must be grounded and remain grounded until all gasoline has drained through the filter.
This can be done by contact with a supporting metal screen which is positively grounded. Never use a plastic funnel, bucket, or similar nonconductive container when servicing from storage cans or Aircraft should be fueled in a safe place. Do not fuel or defuel an aircraft in a hangar or other enclosed space except in case of an emergency.
Aircraft should be free from fire hazards, and have engine switches off and chocks placed under the wheels prior to fueling or defueling.
A person who functions as a fireguard with a COz extinguisher or other firefighting equipment should possess a thorough knowledge of all fuel-servicing hazards. He should guard against breathing hydrocarbon vapors, which may cause sickness or dizziness, or may even be fatal.
Adequate ventilating measures to prevent the accumulation of fumes should be provided.
Because of its high lead content, fuel should not be allowed to come in contact with clothes, skin, or eyes. Fuel-saturated clothing should be removed as soon as possible and the parts of the body exposed to the fuel washed thoroughly with soap and water. Wearing clothing saturated with fuel creates a dangerous fire hazard, and painful blisters (similar to those caused by fire burns) may result from direct contact with fuel. If fuel enters the eyes, medical attention should be sought immediately.
should be removed from the aircraft's vicinity. The truck fuel tank covers should be kept closed except when a tank is actually being loaded.
Ideally, refueling crews for large aircraft would possibly involve four men. One person stands by with the firefighting equipment; another stays with the truck; the third man handles the fuel hose on the ground; and the fourth man handles the tueling hose at the aircraft and fills the tanks (A and B of figure 11-7).
Care should be taken to identify the aviation fuel and lubricating oil dispensed from each refueling unit before beginning the actual servicing. Aviation technicians should be familiar with the various grades and the aircraft's gasoline requirements so that the appropriate fuel is used A check should also be made to see that all radio equipment and electrical switches not needed for the fueling operation are turned off, and nonessential outside electrical sources are not connected to the aircraft. A member of the crew then makes sure that both the aircraft and the truck are properly grounded to prevent sparks from static electricity.
Fueling Operations In the overwing fueling of large aircraft, the man with the CO2 bottle stands close to the aircraft to be refueled. The fuel hose handler on the truck unreels the hose and passes it up to the man on the aircraft who is to do the fueling. Care should be taken in bringing the hose nozzle up to the filler neck of the fuel tank to avoid excessive marring of the aircraft finish.
Attached to the nozzle is a ground wire which is plugged into the receptacle adjacent to the fuel Refueling Crew Duties When an aircraft is to be overwing fueled by truck, it should be located on the apron or a dispersal site, and should not be in the vicinity of possible sources of fuel-vapor ignition. Consideration must be given to the direction of the wind so that fuel vapors are not carried toward a source of The tank truck should be driven to a point as distant from the aircraft as the length of hose permits, and preferably to the windward (upwind) side of the aircraft. It must be parked parallel to or heading away from the wing, or in such a position that it may be driven away quickly in the event of fire (4 of figure 11-7). As soon as the tank to be filled. Another type of ground wire commonly used terminates in an alligator clip connected to a grounding post. This connection is made before the fuel tank cap is removed from the filler neck. This serves as a continuous ground connection for the fuel nozzle (C of figure 11-7).
The fuel truck has two ground wires; one is connected to a suitable ground on the apron (A of figure 11-7), and the other is connected to the aircraft (1 and B figure 11-7). The aircraft should also be grounded to the apron.
This grounding arrangement may take other forms. In many cases, the fuel truck is grounded by a metal chain that is dragged behind the truck;
the aircraft is grounded by a carbon strip embedded in the tires; and the aircraft and fuel truck fueling operation has been completed, the truck are held at a common electrical potential by a 498
Ground wire FIGURE 11-7. Refueling an aircraft.
FIGURE 11-8. Fueling a small aircraft.
conducting wire encircling the fuel hose from nozzle to tank fitting. All this is to prevent a spark from static electricity that may be created as the fuel flows through the fuel hose into the aircraft's The fueling of light aircraft involves fewer problems. While the fueler's responsibilities are still the same, it is usually a one- or two-man operation. The danger of marring the aircraft finish is minimized since the height and location of the fuel tanks usually permit easy accessibility to the filler neck. In addition, small aircraft can be easily pushed by hand to a fueling position near a fuel truck or a fueling island. Figure 11-8 shows a small aircraft being fueled.
When the fuel tank is nearly full, the rate of fuel flow should be reduced for topping off the tank;
that is, the tank should be slowly filled to the top without spilling fuel on the wing or ground. The filler cap is replaced on that tank, the ground wire plug removed from its receptacle, and then the man handling the fuel nozzle takes the hose and moves on to the next tank to be filled. This procedure is followed at each tank until the aircraft is completely refueled. Then the ground wires are disconnected from the aircraft, and the hose is rewound onto the hose reel in the truck.
During this operation the hose or nozzle should not be allowed to drop to the ground.
Pressure Fueling Pressure fueling is used on many late-model aircraft. This fueling process, sometimes referred to as single-point or underwing fueling, greatly reduces the time required to service large aircraft.
There are also other advantages in the pressure fueling process. It eliminates aircraft skin damage and hazards to personnel and reduces the chances for fuel contamination. Pressure fueling also reduces the chance of static electricity igniting fuel vapors.
Because of the limited fuel tank area, there are fewer advantages of a pressure fueling system in light aircraft. Thus, they are usually incorporated only in medium size executive jets and large military or commercial transport aircraft.
Most pressure fueling systems consist of a pressure fueling hose and a panel of controls and gages that permit one man to fuel or defuel any or all fuel tanks of an aircraft. A single-point fueling system is usually designed so that an in-the-wing fueling manifold is accessible near a wingtip or under the wing near the wing root. The valves connecting the various tanks to the main fueling manifold are usually actuated in response to fuel pressure signals.
Fueling and defueling procedures are normally placarded on the fueling control panel access door.
The fueling operator should possess a thorough knowledge of the aircraft fuel system to recognize malfunction symptoms. Since the design of pressure fueling systems varies somewhat with each type of aircraft, the fueling operator should consult the manufacturer's instructions for detailed procedures.
Due to varying procedures in defueling aircraft, it is important to consult the applicable manufacturer's maintenance instructions.
FIRE Types of Fire The National Fire Protection Association has classified fires into three basic types:
a. Class A fires--as fires in ordinary combustible materials such as wood, cloth, paper, upholstery materials, etc.
b. Class B fires--as fires in flammable petroleum products or other flammable or combustible liquids, greases, solvents, paints, etc.
c. Class C fires-as fires involving energized electrical equipment where the electrical nonconductivity of the extinguishing media is of im- 500
portance. In most cases where electrical equipment is deenergized, extinguishers suitable for use on Class A or B fires may be employed effectively.
A fourth class of fire, Class D fire, is defined as fire in flammable metal. Class D fires are not considered a basic type since they are generally caused by a Class A, B, or C fire. Usually these fires involve magnesium in the shop or in aircraft wheels Any one of these types of fires can occur during maintenance or operations. There is a particular type extinguisher which is most effective for each Fire Extinguishment Three things are required for a fire. Fuel— something that will in the presence of heat combine with oxygen, thereby releasing more heat and as a result reduces itself to other chemical compounds.
Heat--can be considered the catalyst which accelerates the combining of oxygen with fuel, in turn releasing more heat. Oxygen--element which combines chemically with another substance through the process of oxidation. Rapid oxidation, accompanied by a noticeable release of heat and light is called combustion or burning (figure 11-9). Re:
move any one of these things and the fire goes out.
IT TAKES THREE THINGS
TO START A FIRE
OXYGEN, HEAT, FUEL OXYGEN
FRICTION (HEAT) FUEL FIGURE 11-9. Three elements for fire.
thereby making combustion impossible. Foam is effective, especially when used in large quantities.
Water is ineffective on class B fires and will cause the fire to spread.
Class C fires involving electrical wiring, equipment, or current respond best to carbon dioxide (CO½) which displaces the oxygen in the atmosphere making combustion improbable. The CO2 equipment must be equipped with a nonmetallic horn to be approved for use on electrical fires.
Two reasons for this must be considered:
1. The discharge of CO2 as through a metal horn can generate static electricity. The static discharge could reignite the fire.
2. The metal horn if in contact with the electrical current would transmit that current to the extinguisher operator.
Halogenated hydrocarbons are very effective on Class C fires. The vapor reacts chemically with the flame to extinguish the fire. Dry chemicals are effective but have the disadvantage of contaminating the local area with powder. Also, if used on wet and energized electrical equipment, it may aggravate current leakage.
Water, wet water or foam are not acceptable agents for use on electrical equipment fires.
Class D fires respond to application of dry powder, which prevents oxidation and the resulting Application may be from an extinguisher or scoop or shovel. Special techniques are needed in combating fires involving metal. Manufacturers recommendations should be followed at all times.
Areas which could be subjected to metal fires should have the proper protective equipment installed.
Under no conditions use water on a metal fire. It will cause the fire to burn more violently and can cause explosions.
Fire Extinguisher Periodic Check List
1. Appropriate extinguisher located in proper place.
2. Safety seals unbroken.
3. Remove all external dirt and rust.
4. Gage or indicator in operable range.
5. Check for proper weight.
6. No nozzle obstruction.
Types of Fire vs. Extinguishing Agent Class A fires respond best to water or water type extinguishers which cool the fuel below combustion temperatures. Class B and C extinguishers are effective but not equal to the wetting/cooling action of the Class A extinguisher.
Class B fires respond to carbon dioxide (CO2), halogenated hydrocarbons (Halons) and dry chemicals, all of which displace the oxygen in the air Fire Extinguishing Agents A. Water and water based agents.
Water may be combined with antifreeze compounds or wetting agents (accelerate penetration of materials by water). Water is used on carbonaceous fires. It extinguishes fires by cooling the fuel below the combustion temperature.
1. Soda-acid and foam act on a fire the same as water by lowering the temperature. Foam 501
has some effect on a petroleum base fire by preventing oxygen from getting to the fire.
2. Loaded stream contains an antifreeze as well as a fame retardant.
B. Dry Chemical.
Four types of chemicals are used:,
1. Sodium bicarbonate (Formula H). For ordinary risk class B and C fires.
2. Ammonium phosphate (Multipurpose). For multiple risk class B and C fires.
3. Potassium bicarbonate (Purple K). For high risk class B and C fires
4. Multipurpose dry chemical (ABC). For use on Class A, B, and C fires. The dry chemicals extinguish a fire by smothering it, cutting off oxygen, and the blanket of dry chemicals prevents reflash fires. It also affords the operator some protection from the heat.
dry chemicals are nonconductors of electricity.
C. Gas.
1. Carbon dioxide (COz) has a toxicity rating (Underwriter's Laboratory) of 5A especially recommended for use on class B and C fires.
Extinguishes flames by dissipating oxygen in the immediate area.
2. Halogenated hydrocarbons (commonly called freon by the industry), are numbered according to chemical formulas with Halon numbers.
Carbon tetrachloride (Halon. 104). Chemical formula CCL. UL toxicity rating of 3. It is poisonous and toxic. Hydrochloric acid vapor, chlorine and phosgene gas are produced whenever carbon tetrachloride is used on ordinary fires. The amount of phosgene gas is increased whenever carbon tetrachloride is brought in direct contact with hot metal, certain chemicals, or continuing electri- It is no longer approved for any fire extinguishing use.
Methyl bromide (Halon 1001). Chemical formula CH Br-a liquified gas, UL toxicity rating of 2. Effective but very toxic and also is corrosive to aluminum alloys, magnesium and zinc. Not recommended for aircraft use.
Chlorobromomethane (Halon 1011). Chemical formula CH¿CIBr-a liquified gas, UL toxicity rating is 3. Not recommended for aircraft use.
Dibromodifluoromethane (Halon 1202). Chemical formula CBrzF2. UL toxicity rating of 4. Not recommended for aircraft use.
Bromochlorodifluoromethane (Halon 1211). Formula CBrCIF2-a liquited gas with a toxicity rating of 5. It is colorless, noncorrosive and evaporates rapidly leaving no residue whatever.
It does not freeze or cause cold burns and will not harm fabrics, metals, or other materials it contacts.
Halon 1211 acts rapidly on fires by producing a heavy blanketing mist that eliminates air from the fire source, but more importantly interferes chemically with the combustion process. It has outstanding properties in preventing reflash after the fire has been extinguished.
Group Definition Examples rases or vapors which in concentrations up to at least 20% by volume fo Bromotrifluoromethane (least lurations of exposure of the order of 2 hours do not appear to produce (Halon 1301) toxic injury.
5a Gases or vapors much less toxic than Group 4 but more toxic than Group Carbon dioxide 4 Gases or vapors which in concentrations of the order of 2 o 2% for Dibromodifluoromethane durations of exposure of the order of 2 hours are lethal or produce serious (Halon 1202) injury.
3 Gases or vapors which in concentrations of the order of 2 to 2:2% for dura- Bromochloromethane tions of exposure of the order of 1 hour are lethal or produce serious injury. (Halon 1011), Carbon tetrachloride (Halon 104) 2 Gases or vapors which in concentrations of the order of 1/2 to 1% for dura- Methyl bromide tions of exposure of the order of 1/2 hour are lethal or produce serious (Halon 1001) injury.
FICURE 11-10. Toxicity table.
Classes of Self-generating Self-expelling Cartridge of N, cylinder Stored oressure fire Pump Hand Extinguishing Materials B Water and antifreeze Soda-acid (water) Wetting agent Foam Loaded stream X+ Multipurpose dry chemical X+ Carbon dioxide X + Dry chemical Bromotrifluoromethane - Halon 1301 Bromochlorodifluoromethane - Halon 1211 Dry powder (metal fires) + Smaller sizes of these extinguishers are not recognized for use on these classes of fires.
FIGURE 11-11. Extinguisher operation and methods of expelling.
Bromotrifluoromethane (Halon 1301). Chemical formula CF Br is also a liquified gas with a UL toxicity rating of 6. It has all the characteristics of Halon 1211. The significant difference between the two is: Halon 1211 forms a spray similar to CO2, while Halon 1301 has a vapor spray that is more difficult to direct.
D. Powder.
Dry powder for metal fires. Fires in metal require special handling. If water is used on a magnesium fire the burning is accelerated. Special dry powders are available for use wherever metal fires are possibilities. These are normally applied by scoop or shovel. Multipurpose (ABC) dry chemicals have a limited use on metal fires such as fires in wheel brakes or in magnesium fires.
(See figures 11-10 and 11-11).
RECOMMENDED MARKINGS TO INDICATE EX-
TINGUISHER SUITABILITY (From NFPA Standard #10) The following recommendations are given as a guide in marking extinguishers, and/or extinguisher locations, to indicate the suitability of the extinguisher for a particular class of fire.
Markings should be applied by decalcomanias, painting or similar methods having at least equivalent legibility and durability.
Where markings are applied to the extinguisher, they should be located on the front of the shell above or below the extinguisher nameplate. Markings should be of a size and form to give easy legibility at a distance of 3 feet.
Where markings are applied to wall panels, etc., in the vicinity of extinguishers, they should be of a size and form to give easy legibility at a distance of 25 feet. (See figures 11-12 and 11-13).
AIRCRAFT FIRE EXTINGUISHERS Fire is one of the most dangerous threats to aircraft- either in flight or on the ground. Airborne fixed, powerplant and airframe, detection and extinguishing systems are designed and installed by the manufacturer in compliance with applicable FAR's. The requirement for portable fire extinguishers installed in the crew and passenger compartment says, the extinguisher must be approved, must be appropriate for the kind of fire likely to occur and must minimize the hazard of toxic gases.
ORDINARY FLAMMABLE 3. Methyl bromide is more toxic than CO, and cannot be used in confined areas. It is also very B corrosive to aluminum alloy, magnesium and zinc. 4. Chlorobromomethane, although an effective extinguishing agent, is toxic.
COMBUSTIBLES LIQUIDS
TYPICAL EXTINGUISHER MARKINGS
ELECTRICAL COMBUSTIBLE
ORDINARY
COMBUSTIBLES
1. Water
EQUIPMENT METALS
FLAMMABLE ELECTRICAL FIGURE 11-12. Identification of fire extinguisher type location.
LIQUIDS EQUIPMENT The National Fire Protection Association tinguishers, suggests the type, capacity, location and quantity of hand fire extinguishers for the (NFPA) Standard #408, Aircraft Hand Fire Ex- 2. Carbon Dioxide, Dry Chemica! Bromotrifluoromethane Bromochlorodifluoromethane and protection of aircraft compartments occupied by passengers and crew. This standard suggests car- ORDINARY FLAMMABLE ELECTRICAL bon dioxide and water (water solution) as the extinguishing media for hand type extinguishers.
Both type extinguishers are suggested for use in the passenger compartment, the number of units COMBUSTIBLES LIQUIDS EQUIPMENT being regulated by the number of passengers carried. Carbon dioxide is suggested for the crew 3. Multipurpose Dry Chemical compartment. A halogenated hydrocarbon extinguishing agent (Halon 1211 or Halon 1301) having FLAMMABLE ELECTRICAL an Underwriter's Laboratory toxicity rating of 5 or higher may be substituted for the carbon dioxide, C if there is sufficient free air volume in the immediate area to prevent serious irritating effects on LIQUIDS EQUIPMENT CAPABILITY the occupants.
The following extinguishing agents are not rec- 4. Multipurpose Dry Chemical (Insutricient Agent tor ommended for aircraft use: "A" Rating)
1. Dry chemical extinguishers are very effective COMBUSTIBLE in Class B and C fires but they leave a residual dust or powder. This obstructs vision, is difficult to clean up and causes damage to electronic equipment.
2. Carbon tetrachloride is no longer approved as METALS gas (phosgene) when in contact with hot metals. a fire extinguishing agent. It produces a poisonous 5. Dry Powder Soda acid and foam, these are toxic to a degree and can be corrosive to adjacent materials. FIGURE 11-13. Typical extinguisher markings.
Extinguishers The common aerosol can type extinguishers are definitely not acceptable as airborne hand type extinguishers. In one instance, an aerosol type foam extinguisher located in the pilot's seat back pocket exploded and tore the upholstery from the seat.
The interior of the aircraft was damaged by the foam. This occurred when the aircraft was on the ground and the outside temperature was 90° F. In addition to the danger from explosion, the size is inadequate to combat even the smallest fire.
another instance, a dry chemical extinguisher was mounted near a heater vent on the floor. For an unknown reason, the position of the unit was reversed. This placed the extinguisher directly in front of the heater vent. During flight, with the heater in operation, the extinguisher became overheated and exploded filling the compartment with dry chemical powder. The proximity of heater vents should be considered when selecting a location for a hand fire extinguisher.
Additional information relative to airborne hand fire extinguishers may be obtained from the local FAA District Office and from the National Fire Protection Association, 470 Atlantic Ave., Boston, MA 0221 Ground Type Extinguishers-Hand Type The selection of a fire extinguisher for ground installation, shop, fueling station, etc., is not restricted as it is for airborne installations. The range of selection for agent and type extinguishers is shown in figure 11-11. (See figures 11-16 and 11-17).
Methods of Extinguisher Operation. The methods of operation of extinguishers are most conveniently arranged by grouping extinguishers according to their expelling means. Six methods are in common use.
Self-generating-actuation causes gases to be generated that provide expellent energy.
Self-expelling-the agents have sufficient vapor pressure at normal operating temperatures to expel themselves.
Gas cartridge or cylinder-expellent gas is confined in a separate pressure vessel until an operator releases it to pressurize the extinguisher shell.
Stored pressure-the extinguishing material and expellent gas are kept in a single container.
Mechanically pumped-the operator provides expelling energy by means of a pump and the vessel containing the agent is not pressurized.
Hand propelled--the material is applied with scoop, pail, or bucket.
Several different extinguishing materials are handled by each of these expelling means.
Discontinued Fire Extinguishers (see figures 11-14 and 11-15) There are still in use today several million fire extinguishers of a design no longer manufactured.
These are the 1½, 2½ and 5 gallon "invert to use" liquid extinguishers. The last of this type were manufactured in the 2½ gallon size. The agents used in these extinguishers are:
1. Soda-acid.
2. Foam.
3. Water cartridge.
4. Loaded stream cartridge.
The reasons which influenced the decision to discontinue manufacturing these extinguishers are:
1. Invert to use-difficult and unorthodox method of activation.
2. Limited to the types of fires for which they are suitable. Mostly Class "A" fires, very limited application of foam on Class "B' fires.
3. None approved for electrical fires.
4. Effective on only minimal size fires.
5. The container does not meet current pressure vessel standards. This is the most significant of all.
Comparison of Safety Factors Discontinued types of extinguishers use a shell rated at either 350 or 500 p.s.i. However, when these extinguishers are inverted to operate, the pressures generated often are unpredictable, totally unlike the pressures in other extinguisher designs.
Pressures may range from 100 to 300 p.s.i for sodaacid extinguishers and from 100 to 350 p.s.i. for the foam extinguishers.
SERVICING AIRCRAFT WITH OIL Aircraft oil tanks are normally checked at the the t the same time the fuel tanks are filled. There are a few exceptions to this general rule, since some manufacturers recommend that the oil level in certain jet engines be checked within a specified time after engine shutdown. In all cases, the manufacturer's instructions should be followed for the specific aircraft not only for servicing procedures but also for type and grade of oil used.
Aircraft oil tanks should never be filled to capacity or above the labeled full mark on the gage or dipstick. This is because oil expands when it becomes hot, and at high altitude it bubbles and expands. The extra space in oil tanks allows for expansion and prevents overflowing. The aircraft's oil requirements should be checked, and no substitutions should be made for the type of oil to be used unless substitute oils have been approved 505
PARROL Soda-acid fire extinguisher. Cartridge operated water fire extinguisher.
FIGURE 11-14. Discontinued types of fire extinguishers #1.
CARBON TETRACHIORIDE Foam fire extinguisher. Vaporizing liquid fire extinguisher.
FIcURE 11-15. Discontinued types of fire extinguishers #2.