Piper PA-28-161, Maintenance Manual

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PAGE 3
Nov 30/06 4C21
51-70-00
PIPER AIRCRAFT, INC.
PA-28-161, WARRIOR III
MAINTENANCE MANUAL
(13) As soon as the patch begins to set up, but while still rubbery, take a sharp knife and cut away
extra cloth and mat. Cut on outside edge of feathering. Strip cut edges of structure. Do this
before cure is complete, to save extra sanding. Allow patch to cure overnight.
(14) Using dry 80 grit sandpaper on a power sander or sanding block, smooth patch and blend with
surrounding surface. Should air pockets appear while sanding, puncture and fill with catalyzed
resin. A hypodermic needle may be used to fill cavities. Let cure and resand.
(15) Mix catalyzed resin and work into patch with fingers. Smooth carefully and work into any
crevices.
(16) Cover with cellophane and squeegee smooth. Allow to cure completely before removing
cellophane. Let cure and resand.
(17) Brush or spray a coat of catalyzed resin to seal patch. Sand patch, finish by priming, again
sanding and applying color coat.
NOTE: Brush and hands may be cleaned in solvents such as acetone or methylethylketone. If
solvents are not available, a strong solution of detergent and water may be used.
2. Thermoplastic Repairs
The following procedure will assist in making field repairs to items made of thermoplastic which are used
throughout the airplane. Chart 1 lists materials needed to perform these repairs along with suggested
suppliers. Common safety precautions should be observed when handling some of the materials and
tools used while making these repairs. Refer to Vendor Information, Chapter 91, for supplier addresses.
A. Surface Preparation
(1) Surface dirt and paint if applied must be removed from the item being repaired. Household
cleaners have proven most effective in removing surface dirt.
(2) Preliminary cleaning of the damaged area with perchlorethylene or V M & P Naphtha will
generally ensure a good bond between epoxy compounds and thermoplastic.
B. Surface Scratches, Abrasion or Ground-in-Dirt (See Figure 1.)
(1) Shallow scratches and abraded surfaces are usually repaired by following directions on
containers of conventional automotive buffing and rubbing compounds.
(2) If large dirt particles are embedded in thermoplastic parts they can be removed with a hot air
gun capable of supplying heat in the temperature range of 300° to 400° F. Use care not to
overheat the material. Hold the nozzle of the gun about 1/4 of an inch away from the surface
and apply heat with a circular motion until the area is sufficiently soft to remove the dirt
particles.
(3) The thermoplastic will return to its original shape upon cooling.
C. Deep Scratches, Shallow Nicks and Small Holes - Less than 1 inch in diameter (See Figure 2.)
(1) Solvent cements will fit virtually any of these applications. If the area to be repaired is very
small, it may be quicker to make a satisfactory cement by dissolving thermoplastic material of
the same type being repaired in solvent until the desired paste like consistency is achieved.
(2) This mixture is then applied to the damaged area. Upon solvent evaporation, the hard durable
solids remaining can easily be shaped to the desired contour by filing or sanding.
(3) Solvent adhesives are not recommended for highly stressed areas, or thin walled parts or for
patching holes greater than 1/4 inch in diameter.
(4) For larger damages, an epoxy patching compound is recommended. This type material is a
two part, fast curing, easy sanding commercially available compound.
(5) Adhesion can be increased by roughing the bonding surface with sandpaper and by utilizing as
much surface area for the bond as possible.