Before we start with how to wash an aircraft correctly
and successfully, maybe we should first ask; why should
we wash an aircraft? Is this a trick question? Not really.
Of course we wash aircraft to make them clean again after
service. Why do we wish to have them clean? Is it purely
for aesthetic reasons or is there a more important agenda
behind this time consuming task? One of the main purposes
of washing is to slow down or reduce the amount of corrosion
occurring in the airframe. Other issues revolve around
safety; being able to see through windows clearly, not
slipping when boarding or disembarking on oil and exhaust
fouling, etc. Another most important, yet overlooked safety
aspect is that of an opportunity for a thorough inspection.
Whilst washing, one can carefully inspect the airframe
for impact damage, degradation to seals and plastic components,
loose fittings and fastenings and other potential problems.
Now that we have ascertained why we are going to wash
the aircraft, lets get ready to actually carry out the
work. Equipment required for the job is usually: Cleaning
fluid, buckets, mop/brush/sponge, chamois, hose with fine
spray nozzle and other items of personal preference. If
you are really fortunate, you may have access to a foam
applicator for applying the cleaning fluid. This is the
preferred method of applying the cleaning fluid to an
aircraft.
Notice that a pressure washing device IS NOT INCLUDED
in this list! Pressure washers have no place in aircraft
cleaning! They can cause horrendous long term damage to
an airframe. There are far too many nooks, crannies and
crevices on an aircraft where water and particles can
lodge under pressure to cause long term degradation and
damage to the airframe. Water under pressure can also
damage and penetrate seals, exacerbate paint loss, and
damage adhesive bonds found on aircraft structures. Another
literally, potentially fatal mistake that even professional
operators make is to use cleaning products not specified
or intended for aircraft use. On any aircraft type, whether
it be ultralight, gyro, GA or heavy commercial,
ONLY use products that have been designed and approved
for use on airframes. Truck wash and car cleaners undoubtedly
do a very good job of cleaning, however they are often
found to contain highly corrosive constituents that may
damage the aircraft. Certified aircraft cleaners have
been thoroughly tested on materials found in airframes,
to demonstrate that they will not damage or degrade any
part of an aircraft structure. For all of you saying;
"but I've got a composite aircraft it doesn't matter",
well sorry, it does. There are many constituents of commercial
and household cleaners that will irreversibly damage composite
substrates, acrylics, rubber and synthetic seal materials
and even two pack paint.
A problem far removed from the airframe itself is that
of cleaners damaging electrical wiring terminations. When
cleaning products are evaluated for military usage, they
are tested specifically regarding this concern. Above
all, never use cleaners containing solvents. Such cleaners
may, as well as damaging substrate, remove grease from
inside bushes and penetrate or otherwise damage seals
on rod ends and similar. Now that we have the correct
kit, we can commence the task. First, lightly rinse the
entire aircraft to remove loose material and dust/dirt
that may scratch the surface. Next, dilute a small quantity
of cleaning fluid to the manufactures recommendation for
"Heavy duty" or "badly soiled", or
whatever terminology they use for a strong dilution. With
this concentrated solution, wash all badly fouled areas
of the aircraft including brakes and wheels, oleos, exhaust
trails, oil streaks and deposits around static wicks.
Most people use a sponge to apply the liquid. Purpose
made soft bristle brushes designed for washing trucks
and coaches are commonly available and lend themselves
to aircraft washing.
They save a lot of bending and stretching, not to mention
keeping you away from the stuff dripping off the underside
of the aircraft. Once the concentrated solution has been
applied to the areas in question, dilute the remains of
the bucket at the ratio specified for general, or light
cleaning. With this, go over the entire airframe starting
at the highest point, agitating the solution on the surface
with a sponge, broom or rag to loosen dirt and grime.
All cleaning products require a bit of physical effort,
despite manufacturers claims of miracles! Products that
don't require movement or agitation on the surface are
way too aggressive for aircraft use and may contain toxic
substances which may end up in your liver. Depending on
the type of product being used, from this point, on the
cleaning process may need to be broken into sections and
rinsing done at the end of each section. Again, no matter
what the manufacturers claim, most detergents will leave
spotting that is difficult to remove if they are allowed
to dry on the surface.
There are non detergent cleaners available such as colloidal
based technology that do not seem to suffer from this
problem. Either way move across the airframe as quickly
and systematically as possible, using this opportunity
to inspect the surface for any damage or defects. To complete
the cleaning re-wash the areas that were done with the
concentrated solution initially. If any parts have been
missed go back and re-apply solution to them. It is suggested
that the whole airframe should be lightly rinsed again
using a fine spray from the hose and if required finish
off with a chamois. Often at this point we are faced with
the dilemma of "To wax or not to wax"? Some
people swear by the application of a wax or polish to
their paint work. If you should choose to apply a surface
finish, again, be exceedingly careful to ascertain that
it is suitable for aircraft use. Many polishes contain
a myriad of solvents and hydro carbons that should not
be applied to plastics found on aircraft. Some preparations
also build up a film on the surface which can capture
and lock in marks and blemishes on the surface, making
future cleaning more difficult.
Even if the product information states that it is safe
for use on plastics be over-cautious about applying it
to windscreens, canopies and bubbles. Again, we are faced
with problems that are not a great concern in other facets
of life. Many products can leave a film on the windscreen
which will produce optical distortion or halo effect.
Both of these situations can be very dangerous in an aircraft.
Haloing is the term given to the phenomenon of getting
a circular rainbow image emanating from the solid surface.
It can be very annoying and dangerous, as it can obscure
vision beyond the windscreen or canopy. It is probably
a good time to point out that when working on a clear
surface, such as the windscreen, there is a method which
should not be deviated from. When rubbing with a cloth,
sponge or even fingers, ALWAYS rub perpendicular to the
horizon. This is extremely important. Should you unwittingly
scratch the surface, you will be able to look around the
scratch rather than having to try and look through it.
Multiple fine scratches can produce a form of optical
distortion which fortunately only have minimal effect
when viewed vertically.
