Aircraft Cleaning

Author: Herbert AlpigerTHIS INTELLECTUAL WORK IS THE PROPERTY OF THE AUTHOR. In reference to KCTCS AP & P 3.3.5 .This work may be distributed for educational purposes, provided that credit is given to the author (by this page). All uses must be approved on a yearly basis by the author in writing. No changes can be made to this material without written consent of the author.

ATE 102Aircraft Cleaning and Corrosion

and Control

Part IAircraft Cleaning

Cleaning

The most important rule for corrosion control is to keep the aircraft clean.

• Dirt & grease hold moisture in contact w/ the metal surfaces

• A clean aircraft is easier to inspect for the first signs of corrosion

Cleaning an aircraft and keeping it clean are extremely important. • A cracked landing gear fitting covered with mud and

grease may be easily overlooked. • Dirt can hide cracks in the skin. • Dust and grit cause hinge fittings to wear excessively. • A film of dirt if left on the aircraft's outer surface, reduces

flying speed and adds extra weight. • A coating of dirt and grease on moving parts makes a sort

of grinding compound that can cause excessive wear. • Salt water has a serious corroding effect on exposed

metal parts of the aircraft.

Exterior Cleaning

There are three methods of cleaning the aircraft exterior:

(1) Wet wash, (2) Dry wash (3) Polishing.

Exterior Cleaning

Wet wash removes oil, grease, or carbon deposits and most soils, with the exception of corrosion and oxide films. The cleaning compounds used are usually applied by spray or mop, after which high pressure running water is used as a rinse. Either alkaline or emulsion cleaners can be used in the wet wash method.

Exterior CleaningDry wash is used to remove airport film, dust, and small accumulations of dirt and soil when the use of liquids is neither desirable nor practical. This method is not suitable for removing heavy deposits of carbon, grease, or oil, especially in the engine exhaust areas. Dry wash materials are applied with spray, mops, or cloths, and removed by dry mopping or wiping with clean, dry cloths.

Exterior CleaningPolishing can be broken down into hand polishing and mechanical polishing. The type and extent of soiling and the final desired appearance determine the cleaning method to be used.

Polishing restores the luster to painted and unpainted surfaces of the airplane, and is usually performed after the surfaces have been cleaned. Polishing is also used to remove oxidation and corrosion. Polishing materials are available in various forms and degrees of abrasiveness.

Exterior CleaningThe washing of aircraft should be performed in the shade whenever possible as cleaning compounds tend to streak the surface if applied to hot metal, or permitted to dry on the area. Install covers over all openings where water

or cleaners might enter and cause damage such as engine inlets & pitot tubes.

Various areas of aircraft, such as the sections housing radar and the area forward of the cockpit that are finished with a dull paint, should not be cleaned more than necessary and should never be scrubbed with stiff brushes or coarse rags.

A soft sponge or cheesecloth with a minimum of manual rubbing is advisable.

Wheel wells & the engine cowling usually have grease & oil deposits which are more difficult to clean.

• Soak these areas w/ a 1:2 mixture of emulsion cleaner• Scrub w/ a soft bristle brush • Rinse w/ high-pressure water

Exterior CleaningExhaust stains can be even more

difficult to remove.• Apply a 1:2 mixture of emulsion

cleaner w/ varsol or kerosene.• Scrub w/ a soft bristle brush • Rinse w/ high-pressure water

Exterior Cleaning

Fayed surface – the metal that is covered in a lap joint.

• During cleaning take care to prevent corrosive cleaners from seeping into the fayed surfaces.

Cleaning Aircraft TiresEngine oil can damage AC tires & should be

removed.• Remove any oil & grease by wiping w/ a rag

dampened w/ aliphatic naphtha• Wash w/ a mild soap & water• Dry w/ compressed air

Cleaning WindowsTransparent plastic such as acrylic are soft &

therefore easy to scratch. And the scratches will impair the pilot’s vision.

• First flush w/ fresh water to wash away loose particles to prevent scratching

• Remove any oil & grease by wiping w/ a soft cloth dampened w/ aliphatic naphtha.

• Wash w/ a mild soap & water using your hand to feel for abrasive particles

• Rinse w/ fresh water• Dry w/ a chamois or absorbent cotton

Powerplant Cleaning

Grease & dirt on AC engines can:• Interfere w/ cooling

• Hide cracks & other defects• Hide fuel, oil, & exhaust leaks

Powerplant Cleaning• Remove cowling• Wash w/ an emulsion cleaner / kerosene

mixture• Use a bristle brush to remove stubborn

deposits• Dry w/compressed air• Lubricate all bellcranks, control rods, &

other moving parts per the manufacturers maintenance manuals

Propeller CleaningPropellers should be cleaned w/ a mild soap

& water, dried, and coated w/ a thin layer of engine oil.

Preparation for PaintingWhen preparing a metal or fabric covered

surface for painting, remove every trace of oil or grease.

• Wipe the surfaces down w/ dope thinner or acetone

Exterior Cleaning

After cleaning, lubricate all grease fittings, hinges, etc., where removal, contamination, or dilution of the grease is suspected during washing of the aircraft.

Solvent CleanersAMT’s should review the Material Safety Data Sheet(MSDS) available for any chemical, solvent or othermaterials they may come in contact with during the

course of their maintenance activities

Particular attention should be paid to recommendedprotective measures including gloves, respirators and

face shields.

Solvent CleanersAliphatic naphtha – a petroleum product similar to

gasoline & kerosene used to clean grease from a painted surface.

Aromatic naphtha – a derivative of coal tar not to be used to clean aircraft parts or surfaces because it is toxic & attacks acrylics & rubber products.

Solvent Cleaners•Dry Cleaning Solvent ( aka. Stoddard solvent) is the most common cleaning solvent used on aircraft, due to its low toxicity, minimal effect on paint, and relative safety. It however leaves a slight residue upon evaporation which must be removed because it may interfere with the application of some final paint films.•Methyl Ethyl Ketone (MEK) is also available as a solvent cleaner for metal surfaces and paint stripper for small areas.

Solvent CleanersKerosene is mixed with solvent emulsion type cleanersfor softening heavy preservative coatings. It is alsoused for general solvent cleaning. Kerosene generally leaves an appreciable film on cleaned surfaces, which may actually be corrosive and should be removed with safety solvent, water emulsion cleaners, or detergent mixtures.

Solvent CleanersEmulsion Cleaners•a chemical cleaner which mixes w/ water or a petroleum solvent to form an emulsion mixture which will separate if it is allowed to stand.•They are used in general aircraft cleaning. Solvent emulsions are particularly useful in the removal of heavy deposits, such as carbon, grease, oil, or tar. When used in accordance with instructions, these solvent emulsions do not affect good paint coatings or organic finishes.

Solvent Cleaners• Do not use synthetic wiping cloths with flammable

agents. Because of the potential for static electrical discharge igniting flammable fumes, wiping cloths made of natural materials such as cotton should be used.

• Agents should not be applied with atomizing spray equipment. This is not only hazardous, but violates environmental regulations in most areas.

Mechanical Cleaning MaterialsNonwoven abrasive pads (a common brand name produced by the 3M company is Scotch-Brite™) are useful for the removal of corrosion products and for other light abrasive needs.

Mechanical Cleaning Materials

Powdered pumice can be used for cleaning corroded aluminum surfaces.  Impregnated cotton wadding material is used for removal of exhaust gas stains and polishing corroded aluminum surfaces

Mechanical Cleaning MaterialsAluminum metal polish is used to produce a high luster, long lasting polish on unpainted aluminum clad surfaces.

It should not be used on anodized surfaces because it will remove the oxide coat.

Mechanical Cleaning MaterialsAluminum wool  and fine grit Aluminum oxide paper (300 grit or finer) are considered safe to use on most surfaces.

Avoid the use of carborundum (silicon carbide) papers, particularly on aluminum or magnesium.

Emery paper or crocus cloth on aluminum or magnesium can cause serious corrosion of the metal

Mechanical Cleaning Materials

Steam cleaning is not recommended for general use on aircraft as it erodes paint, crazes plastic, debonds adhesives, damages electrical insulation, and drives lubrication out of bearings. It may however be used effectively to remove corrosion causing microbial growth from fuel tanks and for removing loosened paint and chemical stripper from aircraft surfaces.

Cleaning ProceduresThe following cleaning procedures are recommended:

• Remove/disconnect all electrical power; • Ground aircraft; • Aircraft wash personnel should wear protective gear (gloves, goggles,

aprons, etc.); • Protect against water/cleaning compound intrusion (close doors,

openings, cover vents, pitot static openings, cover wheels, etc.); • Mix cleaning solution to manufacturer's recommendation; • Use spray not a stream of water during aircraft wash; • Do not use abrasive cleaning pads; and • Rinse aircraft with fresh water to remove all cleaning compounds.

Postcleaning Procedures

• Remove all covers, plugs and masking materials; • Inspect and clear all drain holes; • Inspect all known water trap areas for water accumulation and

proper drainage; • Lubricate aircraft in accordance with applicable maintenance

manual; and • Apply operational preservation.