Keeping hangars, shop, and the flight line orderly and clean is essential to safety and efficient maintenance.
The highest standards of orderly work arrangements and cleanliness should be observed during the maintenance of aircraft.
Where continuous work shifts are established, the outgoing shift should remove and properly store personal tools, rollaway boxes, all work stands, maintenance stands, hoses, electrical cords, hoists, crates, and boxes that were needed for the work to be accomplished.
Signs should be posted to indicate dangerous equipment or hazardous conditions. There should also be signs that provide the location of first aid and fire equipment.
Safety lanes, pedestrian walkways, and fire lanes should be painted around the perimeter inside the hangars. This is a safety measure to prevent accidents and to keep pedestrian traffic out of work areas.
Safety is everyone’s business, and communication is key to ensuring everyone’s safety. Technicians and supervisors should watch for their own safety and for the safety of others working around them. If other personnel are conducting their actions in an unsafe manner, communicate with them, reminding them of their safety and that of others around them.
Safety Around Hazardous Materials:
Material safety diamonds are very important with regard to shop safety. These forms and labels are a simple and quick way to determine the risk and, if used properly with the tags, will indicate what personal safety equipment to use with the hazardous material.
The most observable portion of the Material Safety Data Sheet (MSDS) label is the risk diamond. It is a four colour segmented diamond that represents Flammability (Red), Reactivity (Yellow), Health (Blue), and special Hazard (White). In the Flammability, Reactivity, and Health blocks, there should be a number from 0 to 4. Zero represents little or no hazard to the user; 4 means that the material is very hazardous. The special hazard segment contains a word or abbreviation to represent the special hazard. Some examples are: RAD for radiation, ALK for alkali materials, Acid for acidic materials, and CARC for carcinogenic materials. The letter W with a line through it stands for high reactivity
to water. [Figure 11-2]
The Material Safety Data Sheet (MSDS) is a more detailed version of the chemical safety issues. They all have the same information requirements, but the exact location of the information on the sheet varies by MSDS manufacturer. These forms have the detailed breakdown of the chemicals, including formulas and action to take if personnel come into contact with the chemical(s). The U.S. Department of Labor Occupational Safety and Health Administration (OSHA) requires certain information be on every MSDS.
These forms are necessary for a safe shop that meets all the requirements of the governing safety body, the U.S. Department of Labor Occupational Safety and Health Administration (OSHA).
Safety Around Machine Tools:
Hazards in a shop’s operation increase when the operation of lathes, drill presses, grinders, and other types of machines are used. Each machine has its own set of
safety practices. The following discussions regarding precautions should be followed to avoid injury.
The drill press can be used to bore and ream holes, to do facing, milling, and other similar types of operations.
The following precautions can reduce the chance of injury:
• Wear eye protection.
• Securely clamp all work.
• Set the proper RPM for the material used.
• Do not allow the spindle to feed beyond its limit of travel while drilling.
• Stop the machine before adjusting work or attempting to remove jammed work.
• Clean the area when finished.
Lathes are used in turning work of a cylindrical nature.
This work may be performed on the inside or outside of the cylinder. The work is secured in the chuck to provide the rotary motion, and the forming is done by contact with a securely mounted tool. The following precautions can reduce the chance of injury:
• Wear eye protection.
• Use sharp cutting tools.
• Allow the chuck to stop on its own. Do not attempt to stop the chuck by hand pressure.
• Examine tools and work for cracks or defects before starting the work.
• Do not set tools on the lathe. Tools may be caught by the work and thrown.
• Before measuring the work, allow it to stop in the lathe.
Milling machines are used to shape or dress; cut gear teeth, slots, or key ways; and similar work. The following precautions can reduce the chance of injury:
• Wear eye protection.
• Clean the work bed prior to work.
• Secure the work to the bed to prevent movement during milling.
• Select the proper tools for the job.
• Do not change the feed speed while working.
• Lower the table before moving under or away
from the work.
• Ensure all clamps and bolts will pass under the arbor.
Grinders are used to sharpen tools, dress metal, and perform other operations involving the removal of small amounts of metal. The following precautions can reduce the chance of injury:
• Wear eye protection even if the grinder has a shield.
• Inspect the grinding wheel for defects prior to use.
• Do not force grinding wheels onto the spindle. They fit snugly, but do not require force to install them. Placing side pressure on a wheel could cause it to explode.
• Check the wheel flanges and compression washer. They should be one-third the diameter of the wheel.
• Do not stand in the arc of the grinding wheel while operating, in case the wheel explodes.
Welding should be performed only in designated areas.
Any part to be welded should be removed from the aircraft, if possible. Repair would then be accomplished in the welding shop under a controlled environment.
A welding shop should be equipped with proper tables, ventilation, tool storage, and fire prevention and extinguishing equipment.
Welding on an aircraft should be performed outside, if possible. If welding in the hangar is necessary, observe these precautions:
• During welding operations, there should be no open fuel tanks, and no work on fuel systems should be in progress.
• No painting should be in progress.
• No aircraft are to be within 35 feet of the welding operation.
• No flammable material should be in the area around the welding operation.
• Only qualified welders should be permitted to do the work.
• The welding area should be roped off and placarded.
• Fire extinguishing equipment of a minimum rating of 20B should be in the immediate area with 80B rated equipment as a backup. These ratings will be explained later in this chapter.
There should be trained fire watches in the area around the welding operation.
• Aircraft being welded should be in towable condition, with a tug attached, and the aircraft
parking brakes released. A qualified operator should be on the tug, and mechanics available to assist in the towing operation should it become necessary to tow the aircraft. If the aircraft is in the hangar, the hangar doors should be opened.
Flight Line Safety:
The flight line is a place of dangerous activity. Technicians who perform maintenance on the flight line must constantly be aware of what is going on around them.
The noise on a flight line comes from many places.Aircraft are only one source of noise. There are auxiliary- power units (APUs), fuel trucks, baggage handling equipment, and so forth. Each has its own frequency of sound. Combined all together, the ramp or flight line can cause hearing loss.
There are many types of hearing protection available. Hearing protection can be external or internal. The external protection is the earmuff/headphone type. The internal type fit into the auditory canal. Both types will reduce the sound level reaching the eardrum and
reduce the chances of hearing loss.
Hearing protection should also be used when working with pneumatic drills, rivet guns, or other loud or noisy tools or machinery. Because of their high frequency, even short duration exposure to these sounds can cause a hearing loss. Continued exposure will cause hearing loss.
Foreign Object Damage (FOD)
FOD is any damage caused by any loose object to aircraft, personnel, or equipment. These loose objects can be anything from broken runway concrete to shop
towels to safety wire.
To control FOD, keep ramp and operation areas clean, have a tool control program, and provide convenient receptacles for used hardware, shop towels, and other
The modern gas turbine engine will create a low pressure area in front of the engine that will cause any loose object to be drawn into the engine. The exhaust of these engines can propel loose objects great distances with enough force to damage anything that is hit.
The importance of an FOD program cannot be overstressed when a technician considers the cost of engines, components, or the cost of a human life.
Never leave tools or other items around the intake of a turbine engine.
Safety Around Airplanes:
As with the previously mentioned items, it is importantto be aware of propellers. Do not assume the pilot of a taxiing aircraft can see you. Technicians must stay where the pilot can see them while on the ramp area.
Turbine engine intakes and exhaust can also be very hazardous areas. There should be no smoking or open flames anywhere near an aircraft in operation. Be aware
of aircraft fluids that can be detrimental to skin. When operating support equipment around aircraft, be sure to allow space between it and the aircraft and secure it so it cannot roll into the aircraft. All items in the area of operating aircraft must be stowed properly.
Safety Around Helicopters:
Every type of helicopter has its own differences. These differences must be learned to avoid damaging the helicopter or injuring the technician.
When approaching a helicopter while the blades are turning, observe the rotor head and blades to see if they are level. This will allow maximum clearance as you approach the helicopter. Observe the following:
• Approach the helicopter in view of the pilot.
• Never approach a helicopter carrying anything with a vertical height that the blades could hit.
This could cause blade damage and injury to the person.
• Never approach a single-rotor helicopter from the rear. The tail rotor is invisible when operating.
• Never go from one side of the helicopter to the other by going around the tail. Always go around the nose of the helicopter.
When securing the rotor on helicopters with elastometric bearings, check the maintenance manual for the proper method. Using the wrong method could damage the bearing.
Performing maintenance on aircraft and their components requires the use of electrical tools which can produce sparks, along with heat-producing tools and equipment, flammable and explosive liquids, and gases.
As a result, a high potential exists for fire to occur. Measures must be taken to prevent a fire from occurring and to also have a plan for extinguishing it. The key to fire safety is knowledge of what causes fire, how to prevent it, and how to put it out. This knowledge
must be instilled in each technician emphasized by their supervisors through sound safety programs, and occasionally practiced. Airport or other local fire departments can normally be called upon to assist in training personnel and helping to establish fire safety programs for the hangar, shops, and flight line.
Aircraft Cleaning Purpose:
Paint is one reason why specialty cleaners have been developed. The second reason is that aluminum — both the sheet metal and the castings for things such as the landing gear — is very chemically sensitive to many common cleaning agents.
Aluminum has the wonderful properties of strength and light weight, but there is an Achilles heel of sorts. Certain chemicals found in many common cleaners have alkaline properties that can have an adverse effect on both paint and the aluminum itself. These chemicals can contribute to hydrogen embrittlement or structural weakening of highly stressed aluminum, or in the case of sheet metal, a dulling of unpainted surfaces, which promotes pitting and corrosion.
The concern is great enough that the FAA has issued an advisory circular warning of care in using common alkaline cleaning agents. The surprising thing is that some of these “harsh” chemicals have been commonly used in the past. They have undoubtedly contributed to the early dulling and destruction of aircraft paint when used by well-meaning but uninformed people.
Cleaners such as Formula 409 and regular Simple Green have no place in an aircraft cleaning kit. Note that there is now a special Simple Green designed to meet the safety standards set forth for aircraft. The container clearly indicates its different formulation. It is called Extreme Simple Green and has been completely reformulated to be safe on aircraft when properly used. It’s also biodegradable.
Mirror Glaze Plastic Cleaner and Polish
Getting bug stains off of wings is always a chore, but there are new cleaners that work on dissolving the proteins in the bugs rather than abrasive action typical of the old ways to get the wings clean. Clean wings can be good for a few knots.
Another area of concern is with Plexiglas in aircraft, which can be dulled, scratched and crazed by common household chemical use, especially with dirty rags used in cleaning the general surfaces of the aircraft. Plexiglas needs TLC and separate handling and chemicals when it comes to cleaning.
Anything other than new, cotton flannel is asking for trouble, whether during the cleaning cycle or at any time the windshield is cleaned during a fuel-up. There is no room for paper towels of any sort when it comes to cleaning Plexiglas, either. Always decline the line service offer to do the windshield if you want max. life for your windows.
Plexiglas must be cleaned in stages, with plenty of water to keep any dirt flowing off the surfaces. This is then followed by the clean (no shop rags) flannel cloth with an approved Plexiglas cleaner or polish designed expressly for the job.
My favorite brand has always been Meguiar’s Mirror Glaze. Use Plastic Cleaner Number 17 for cleaning and getting rid of hairline scratches. Follow with a coat of Meguiar’s Number 10 Plastic Polish.
Avoid Power Washers
Probably one of the easiest ways to clean and possibly ruin the paint or even the structure of an airplane is to use a power washer loaded up with a harsh, powerful, alkaline cleaner. These washers develop over 1000 psi of water pressure and can warp skins, peel paint, and even drive alkaline chemicals under the skin through seams — particularly if the washer is directed from the back to the front of the aircraft and into the seams. These chemicals then sit in the seams or other areas where they can literally fester, causing corrosion.
The worst thing that you can do is to blast water up into the plane from angles never designed to protect the structure from the elements in the normal course of flying.
Use the Proper Cleaners
Extreme Simple Green for Aircraft
Catalog sources such as Aircraft Spruce have a substantial choice of cleaning agents dedicated to aircraft structures. And while they may cost a little more than an auto-store source, the long-term health of the airplane is what’s at stake.
The investment does not have to be that great. A general-purpose mild cleaner is needed to clean the “sunny side” of the plane. Hand washing the aircraft skin has the benefit of enabling you to go over the entire skin, looking for any early signs of problems such as corrosion or missing paint. And regardless of the wash agent you use, there is no substitute for through and complete rinsing with the universal solvent — water.
Never go over the Plexiglas with washrags. When you are washing the plane use your bare hands to caress the plastic clean. Once all the cleaning is done and the windows are dry, then it’s time for the Plexiglas cleaner and polish.
A Dirty Belly
A belly stained with grease, oil and exhaust is par for the course, especially in older planes with tired engines. There are dedicated products for this purpose that do a good job, while leaving your paint intact. Of course, the longer you wait to attack the problem the worse it will be, so let’s get to it.
If the grime is really thick your best bet is a pressure sprayer, but not the 1000-psi variety. Something as simple as a garden sprayer will work to dispense the cleaner. Shop air and a wand with a tube dipped into cleaner will also do the job. In this case the cleaner must be liquid rather than a gel cleaner. Even the new Extreme Simple Green claims to be able to do this tough job when diluted as recommended and used in a pressure sprayer.
Give it a chance to work before washing it off. This is one chore where repeating the cycle will be necessary, as will elbow grease to get the grime off. And don’t forget the eye protection while you are under the aircraft.
If you want to do a really thorough job, a creeper to slide under the aircraft will be very helpful. And if the job is monumental from years of accumulation, you may want to consider an inexpensive, disposable, plastic tarp to catch the bulk of the grease to be environmentally responsible.
Most airports have designated wash areas so that the run-off will not go into the normal drainage system. All the concentrated chemicals are simply too harsh to dump into normal drains. Be sure to use these designated wash areas whenever they are available.
Aircraft Spruce has a large selection of cleaners and polishes to choose from. The first one that you will want to use is a gentle wash product approved for aviation. One example is Safety Wash, which meets Boeing standards. For heavy grease and oil you can try a more powerful degreaser that has a gel consistency for tough belly stains. One recommended product is Hydrasolve.
For general-purpose and spot cleaning, Extreme Simple Green will also do the trick. Follow the directions on the container for dilution.
The real secret to making the process less painful is to not wait too long between cleanings. You will find that it is well worthwhile in the long-term health of the aircraft.
If you feel that you must polish the aircraft, as we said, use an aircraft-qualified polish that does not contain any abrasives. A good choice here is Racer’s Edge polish, which meets Boeing safety standards.
If the paint is faded, then you will have to get rid of oxidation with a polishing compound. There are several grades of polishing compounds with varying degrees of cutting action.
In the horizontal mode (such as on top of the wing), the weight of the orbital buffer alone is sufficient; otherwise use your body to apply modest pressure to the buffing process. Always keep the buffer moving.
This is an area where you should seek the counsel of a knowledgeable aircraft-paint care person, because it’s easy to ruin paint if you get too aggressive or use the wrong polishing technique. Usually, more than one grade of compound is required, and you will best be served by staying with a polishing system such as from 3M.
Rotary electric buffers that spin under 1800 rpm or have variable speeds are the realm of the pro or knowledgeable amateur. You can burn through the paint in a heartbeat. With combination orbital buffers you have much less chance of doing harm.
The big issue is trying to go too fast and trying to use too aggressive cleaners to speed up the process. Some faded paint just cannot be saved no matter what you do because the oxidation just runs too deep.
As a general rule, only rated pilots and qualified airframe and power plant technicians are authorized to start, run up, and taxi aircraft. All taxiing operations should be performed in accordance with applicable local regulations. Figure 11-22 contains the standard taxi light signals used by control towers to control and expedite the taxiing of aircraft. The following
section provides detailed instructions on taxi signals and related taxi instructions.
Many ground accidents have occurred as a result of improper technique in taxiing aircraft. Although the pilot is ultimately responsible for the aircraft until the engine is stopped,
a taxi signalman can assist the pilot around the flight line. In some aircraft configurations,
the pilot’s vision is obstructed while on the ground.
The pilot cannot see obstructions close to the wheels or under the wings, and has little idea of what is behind the aircraft. Consequently, the pilot depends upon the taxi signalman for directions. Figure 11-23 shows a taxi signalman indicating his readiness to assume guidance of the aircraft by extending both arms at full length above his head, palms facing each other.
The standard position for a signalman is slightly ahead of and in line with the aircraft’s left wingtip. As the signalman faces the aircraft, the nose of the aircraft is on the left. [Figure 11-24] The signalman must stay far enough ahead of the wingtip to remain in the pilot’s field of vision. It is a good practice to perform a fool proof test to be sure the pilot can see all signals.
If the signalman can see the pilot’s eyes, the pilot can see the signals.
Figure 11-24 shows the standard aircraft taxiing signals published in the FAA Aeronautical Information Manual (AIM). It should be emphasized that there are other standard signals, such as those published by the Armed Forces. In addition, operation conditions in many areas may call for a modified set of taxi signals. The signals shown in Figure 11-24 represent a minimum number of the most commonly used signals. Whether this set of
signals or a modified set is used is not the most important consideration, as long as each flight operational center uses a suitable, agreed-upon set of signals.
Figure 11-25 illustrates some of the most commonly used helicopter operating signals.
The taxi signals to be used should be studied until the taxi signalman can execute them clearly and precisely.
The signals must be given in such a way that the pilot cannot confuse their meaning. Remember that the pilot receiving the signals is always some distance away, and must often look out and down from a difficult angle. Thus, the signalman’s hands should be kept
well separated, and signals should be over-exaggerated rather than risk making indistinct signals. If there is any doubt about a signal, or if the pilot does not appear to be following the signals, use the “stop” sign and begin the series of signals again.
The signalman should always try to give the pilot an indication of the approximate area in which the aircraft is to be parked. The signalman should glance behind himself or herself often when walking backward to prevent backing into a propeller or tripping over a chock,
fire bottle, tiedown line, or other obstruction.
Taxi signals are usually given at night with the aid of illuminated wands attached to flashlights. [Figure 11‑26] Night signals are made in the same manner as day signals with the exception of the stop signal. The stop signal used at night is the “emergence stop” signal.
This signal is made by crossing the wands to form a lighted “X” above and in front of the head.