CHAPTER 11
GROUND HANDLING, SAFETY, AND SUPPORT EQUIPMENT
INTRODUCTION Aircraft maintenance technicians devote a portion of their aviation career working with ground support equipment and ground handling i aircraft. The complexity oi support equipmen nd the hazards involved in ground handing o expensive aircraft require that maintenance technicians possess a detailed knowledge of safe procedures used in aircraft servicing, taxing, runup, and in the use of ground support equipment. The information provided in this chapter is intended as a general guide for working on all types of aircraft.
GENERAL The following instructions cover the starting procedures for reciprocating, turboprop, and turbojet engines. These procedures are presented only as a general guide for familiarization with typical procedures and methods. Detailed instructions for starting a specific type of engine can be found in the manufacturer's instruction book.
Before starting an aircraft engine:
1. Position the aircraft to head into the prevailing wind to insure adequate air flow over the engine for cooling purposes.
2. Make sure that no property damage or personal injury will occur from the propeller or pro-
5. If the aircraft is jet engine powered, the area in front of the jet inlet must be kept clear of personnel, property and/or debris. Also, the exhaust area must be kept clear.
6. These "before starting" procedures apply to reciprocating, turbo-propeller and turbo-jet powerplants.
STARTING ENGINES Reciprocating Engines The following procedures are typical of those used to start reciprocating engines. There are, however, wide variations in the procedures for the many reciprocating engines. No attempt should be made to use the methods presented here for actually starting an engine. Instead, always refer to the procedures contained in the applicable manufacturer's instructions.
Reciprocating engines are capable of starting in fairly low temperatures without the use of engine heating or oil dilution, depending on the grade of The various covers (wing, tail, cockpit, wheel, etc.) protecting the aircraft must be removed before attempting to turn the engine. External sources of electrical power should be used when starting engines equipped with electric starters.
This eliminates an excessive burden on the aircraft battery. All unnecessary electrical equipment should be left off until the generators are furnishing electrical power to the aircraft power
3. If external electrical power is used for starting, make sure that it can be removed safely.
4. During any and all starting procedures a "fire guard" equipped with a suitable fire extinguisher shall be stationed in an appropriate place. ("Fire guard"-someone familiar with aircraft starting "Fire extinguisher"-a CO2 extinguisher at least of 5-lb. capacity. Appropriate place"-adjacent to the outboard side of the engine, in view of the pilot, and also where he can observe the engine/aircraft for indication of starting prob- Before starting a radial engine that has been shut down for more than 30 minutes, check the ignition switch for off; turn the propeller three or four complete revolutions with the starter, or it may be pulled through by hand to detect a hy.
draulic lock if one is present.
Any liquid present in a cylinder is indicated by the abnormal effort required to rotate the propeller, or by the propeller stopping abruptly during rotation. Never use force to turn the propeller when a hydraulic lock is detected.
Sufficient force can be exerted on the crankshaft to bend or break a connecting rod if a lock is present.
To eliminate a lock, remove either the front or rear spark plug from the lower cylinders and pull the propeller through. Never attempt to clear the hydraulic lock by pulling the propeller through in the opposite direction to normal rotation. This tends to inject the liquid from the cylinder into the intake pipe. The liquid will be drawn back into the cylinder with the possibility of complete or partial lock occurring on the subsequent start.
To start the engine, proceed as follows:
1. Turn the auxiliary fuel pump on, if aircraft is so equipped.
2. Place the mixture control to the position recommended for the engine and carburetor combination being started. As a general rule, the mixture control should be in the "idle cutoff" position for pressure type carburetors and in the "full rich" position for float type carburetors.
Many light aircraft are equipped with a mixture control pull rod which has no detented intermediate positions. When such controls are pushed in flush with the instrument panel, the mixture is set in the "full rich" position. Conversely, when the control rod is pulled all the way out, the carburetor is in the "idle cutoff" or "full lean" position. Unmarked intermediate positions between these two extremes can be selected by the operator to achieve any desired mixture setting.
3. Open the throttle to a position that will provide 1,000 to 1,200 r.p.m. (approximately ⅛ to ½ inch from the "closed" position).
4. Leave the preheat or (carburetor air) control in the "cold" position to prevent damage and fire in case of backfire. These auxiliary heating devices should be used after the engine warms up.
They improve fuel vaporization, prevent fouling of the spark plugs, ice formation, and eliminate icing in the induction
5. Energize the starter after the propeller has made at least two complete revolutions, and turn the ignition switch on. On engines equipped with an induction vibrator, turn switch to the "both" position.
When starting an engine that uses an impulse coupling magneto, ignition switch to the "left" position.
Place the ignition switch to "start" when the magneto incorporates a retard breaker assembly. Do not crank the engine continuously with the starter for more than 1 minute. Allow a 3- to 5-minute period for cooling the starter between successive attempts. Otherwise the starter may be burned out due to overheating.
6. Move the primer switch to "on" intermittently, or prime with one to three strokes of priming pump, depending on how the aircraft is equipped. When the engine begins to fire, hold the primer on while gradually opening throttle to obtain smooth operation.
After the engine is operating smoothly on the primer, move the mixture control to the "full rich" position. Release the primer as soon as a drop in r.p.m. indicates the engine is receiving additional fuel from the carburetor.
Hand Cranking If the aircraft has no self-starter, the engine must be started by swinging the propeller. The person who is turning the propeller calls,ifuel on, switch off, throttle closed, brakes on." The person operating the engine will check these items and repeat the phrase. The switch and throttle must not be touched again until the person swinging the prop calls "contact." The operator will repeat "contact" and then turn on the switch. Never turn on the switch and then call "contaet."
When swinging the prop, a few simple precautions will help to avoid accidents. When touching a propeller, always assume that the ignition is on. The switches which control the magnetos operate on the principle of short-circuiting the current to turn the ignition off. If the switch is faulty, it can be in the "off" position and still permit current to flow in the magneto primary circuit.
Be sure the ground is firm. Slippery grass, mud, grease, or loose gravel can lead to a fall into or under the propeller. Never allow any portion of your body to get in the way of the propeller. This applies even though the engine is not being Stand close enough to the propeller to be able to step away as it is pulled down. Stepping away after cranking is a safeguard in case the brakes fail. Do 490
not stand in a position that requires leaning toward the propeller to reach it. This throws the body off balance and could cause you to fall into the blades when the engine starts.
In swinging the prop, always move the blade downward by pushing with the palms of the hand.
Do not grip the blade with the fingers curled over the edge, since "kickback" may break them or draw your body in the blade path.
Excessive throttle opening and intermittent priming after the engine has fired are the principal causes of backfiring during starting. Gradual opening of the throttle while priming continuously will reduce the initial "over rich" mixture to a smooth running, best power mixture as the engine picks up speed. An engine operating on an "over rich" mixture is sluggish but will not backfire.
When starting an engine using a priming pump, move the mixture control into "full rich" position, if not previously placed there, when the engine begins to fire. If the engine fails to start immedi-.
ately, return the mixture control to "idle cutoff" position. Failure to do so will create an excessive amount of fuel in the carburetor air scoop, constituting a fire hazard.
Avoid priming the engine before it is turned over by the starter. This can result in fires, scored or scuffed cylinders and pistons, and, in some cases, engine failures due to hydraulic lock. If the engine is inadvertently flooded or overprimed, turn the ignition switch off and move the throttle to the "full open" position. To rid the engine of the excess fuel, turn it over by hand or by the starter.
If excessive force is needed to turn over the engine, stop immediately. Do not force rotation of the engine. If in doubt, remove the lower cylinder spark plugs. If very serious overloading has occurred, it may be necessary to remove the lower cylinder intake pipes. To reduce the likelihood of damage to the engine due to overpriming on some medium and large aircraft, the engine blower drain valves should be checked frequently for fouling or Immediately after the engine starts, check the oil pressure indicator. If oil pressure does not show within 30 seconds, stop the engine and determine the trouble. If oil pressure is indicated, adjust the throttle to the aircraft manufacturer's specified
r.p.m. for engine warm-up. Warm-up r.p.m. will usually be in the 1,000 to 1,300 r.p.m. range.
Most aircraft reciprocating engines are air cooled and depend on the forward speed of the aircraft to maintain proper cooling. Therefore, particular care is necessary when operating these engines on the ground.
During all ground running, operate the engine with the propeller in full low pitch and headed into the wind with the cowling installed to provide the best degree of engine cooling. The engine instruments should be monitored closely at all times. Do not close the cowl flaps for engine warm-up; closing of the cowl flaps may cause the ignition harness to overheat. When warming up the engine, make sure that personnel, ground installations, equipment that may be damaged, or other aircraft are not in the propeller wash.
Extinguishing Engine Fires In all cases a fireguard should stand by with a CO2 fire extinguisher while the aircraft engine is being started. This is a necessary precaution against fire during the starting procedure. He should be familiar with the induction system of the engine so that in case of fire he can direct the CO, into the air intake of the engine to extinguish it. A fire could also occur in the exhaust system of the engine from liquid fuel being ignited in the cylinder and expelled during the normal rotation of the engine.
If an engine fire develops during the starting procedure, continue cranking to start the engine and blow out the fire. If the engine does not start and the fire continues to burn, discontinue the start attempt. The fireguard should extinguish the fire using the available equipment. The fireguard must observe all safety practices at all times while standing by during the starting procedure.
TURBOPROP ENGINES Prestart Procedures The various covers protecting the aircraft must be removed. Engine tailpipes should be carefully inspected for the presence of fuel or oil. A close visual inspection of all accessible parts of the engines and engine controls should be made, followed by an inspection of all nacelle areas to determine that all inspection and access plates are secured. Sumps should be checked for water. Air inlet areas should be inspected for general condition and foreign material. The compressor should be checked for free rotation, when the installation permits, by reaching in and turning the blades by hand.
The following procedures are typical of those used to start turboprop engines. There are,
however, wide variations in the procedures applicable to the many turboprop engines, and no attempt should be made to use these procedures in the actual starting of a turboprop engine. These procedures are presented only as a general guide for familiarization with typical procedures and methods. For starting of all turboprop engines, refer to the detailed procedures contained in the applicable manufacturer's instructions or their approved equivalent.
The first step in starting a turbine engine is to provide an adequate source of power for the starter. Where an air turbine starter is used, the starting air supply may be obtained from a gas-turbine compressor (GTC), an external source, or an engine cross-bleed operation. To start the first engine, use a GTC or low-pressure, large-volume tank. Start the remaining engine(s) using bleed air from the running engine.
While starting an engine, always observe the following:
1. Never energize the starter while the engine is rotating.
2. Do not move the power lever of any engine while it is being bled for cross-bleed
3. Do not perform a ground start if turbine inlet temperature is above that specified by the manufacturer.
4. Do not use bleed air from an engine that is accelerating.
Starting Procedures To start an engine on the ground, perform the following operations:
1. Place the start selector switch to the desired engine and the start-arming switch (if so equipped) to the "start" position.
2. Turn the aircraft boost pumps on.
3. Place the fuel and ignition switch on.
4. Position the low-r.p.m. switch in low or normal (high).
5. Make sure that the power lever is in the "start" position. If the propeller is not at the "start" position, difficulty may be encountered in making a start.
6. Depress the start switch and, if priming is necessary, depress the primer button.
7. Make sure the fuel pump parallel light comes on at, or above, 2,200 r.p.m. and remains on up to 9,000 r.p.m.
8. Check the oil pressure and temperature.
Maintain the power lever at the "start" position until the specified minimum oil temperature is reached.
9. Disconnect the ground power supply.
If any of the following conditions occur during the starting sequence, turn off the fuel and ignition switch, discontinue the start immediately, make an investigation and record the findings.
1. Turbine inlet temperature exceeds the specified maximum. Record the observed peak temperature.
2. Acceleration time from start of propeller rotation to stabilized r.p.m. exceeds the specified time.
3. There is no oil pressure indication at 5,000 r.p.m. for either the reduction gear or the power unit.
4. Torching (visible burning in the exhaust nozzle other than normal enrichment) or excessive smoke is observed during initial fire-up.
5. The engine fails to ignite by 4,500 r.p.m.
or maximum motoring r.p.m. (whichever is first), and r.p.m. stagnates or begins to decay-
6. Abnormal vibration is noted or compressor surge occurs (indicated by backfiring).
7. There is fuel spewing from the nacelle drain, indicating that the drip valve did not close.
8. Fire warning bell rings. (This may be due to either an engine fire or failure of an anti-icing shutoff valve to close.)
TURBOJET ENGINES Preflight Operations Unlike reciprocating engine aircraft, the turbojet-powered aircraft does not require a preflight runup unless it is necessary to investigate a suspected malfunction.
Before starting, all protective covers and airinlet duct covers should be removed. If possible, the aircraft should be headed into the wind to obtain better cooling, faster starting, and smoother engine performance. It is especially important that the aircraft be headed into the wind if the engine is to be trimmed.
The runup area around the aircraft should be cleared of both personnel and loose equipment.
Distance in feet → 30 Ft.
- 200 100° 35K
- 150 Velocity in knots - K 125° 60K Temperature in °F.
Exhaust
- 100 → 12 ft. 100° 150° 100K 200° 200K 150° BOK 300K 300° 200° 100K 500K 500° 300° 200K 900K 700° 25 ft.
Air intake Air intake Idle Takeoff FIGURE 11-1. Engine intake and exhaust hazard areas.
The turbojet engine intake and exhaust hazard areas are illustrated in figure 11-1. Care should also be taken to ensure that the runup area is clear of all items such as nuts, bolts, rocks, rags, or other loose debris.
A great number of very serious accidents occur involving personnel in the vicinity of turbojet engine air inlets. Extreme caution should be exercised when starting turbojet aircraft.
The aircraft fuel sumps should be checked for water or ice, and the engine air inlet should be inspected for general condition and the presence of foreign objects. The forward compressor blades and the compressor inlet guide vanes should be visually inspected for nicks and other damage.
If possible, the compressor should be checked for free rotation by turning the compressor blades by hand.
All engine controls should be operated, and engine instruments and warning lights should be checked for proper operation.
Starting a Turbojet Engine The following procedures are typical of those used to start many turbojet engines. There are, however, wide variations in the starting procedures used for turbojet engines, and no attempt should be made to use these procedures in the actual starting of an engine. These procedures are presented only as a general guide for familiarization with typical procedures and methods. In the starting of all turbojet engines, refer to the detailed procedures contained in the applicable manufacturer's instructions or their approved Most turbojet engines can be started by either air turbine or combustion-type starters. Airturbine starters use compressed air from an external source. This source may be a ground cart unit or air bled from another engine on the aircraft that is in operation. Combustion starters are small gas turbine engines that obtain power from expanding gases generated in the starter's combustion chamber. These hot gases are produced by the burning of fuel and air or, in some cases, a slow-burning solid or liquid monopropellant specially compounded for such starter units.
Fuel is turned on either by moving the powerlever to "idle" position or by opening a fuel shutoff valve. If an air-turbine starter is used, the engine should start or "light up" within approximately 20 seconds after the fuel is turned on. This is an arbitrarily chosen time interval that, if exceeded, indicates a malfunction has occurred and the start should be discontinued. After the cause of the trouble has been removed, another start may be made. If a combustion starter is used, the 20-second interval need not be observed, since starter operation will discontinue automatically after a predetermined time interval. The following procedures are useful only as a general guide, and are included to show the sequence of events in starting a turbojet engine.
1. Move power lever to "off" position unless the engine is equipped with thrust reverser.
If the engine is so equipped, place the power lever in the "idle" position.
2. Turn on electrical power to engine.
3. Turn fuel system shutoff switch to fuel on" position.
4. Turn fuel boost pump switch on.
5. A fuel inlet pressure indicator reading of 5 p.s.i. ensures fuel is being delivered to engine fuel pump inlet.
6. Turn engine starter switch on; when engine begins to rotate, check for oll pressure rise.
7. Turn ignition switch on after engine begins to rotate.
8. Move throttle to idle (if engine is not equipped with thrust reverser).
9. Engine start (light up) is indicated by a rise in exhaust gas temperature.
10. After engine stabilizes at idle, ensure that none of the engine limits are exceeded.
11. Turn engine starter switch off after start.
12. Turn ignition switch off.
Unsatisfactory Turbojet Starts
1. Hot Starts.
A hot start occurs when the engine starts, but the exhaust gas temperature exceeds specified limits. This is usually caused by an excessively rich fuel/air mixture entering the combustion chamber. The fuel to the engine should be shut off immediately.
2. False or Hung Start.
False or hung starts occur when the engine starts normally but the r.p.m. remains at some low value rather than increasing to the normal starting r.p.m. This is often the result of insufficient power to the starter, or the starter cutting off before the engine starts self-accelerating. In this case, the engine should be shut down.
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