Hi Brian;
This question has been a topic of discussion on many owners forums. The following is the consensus after discussion with legality experts.
To my knowledge, there’s nothing in the type certificate data sheet (TCDS) that prohibits repairs as described.
The Piper Service manual for your airplane-at the date the airplane was manufactured—did not prohibit this type of patch repair:
“4-57. STRUCTURAL REPAIRS. Structural repair methods used may be made in accordance with the regulations set forth in Federal Aeronautics Manual 18 or FAA Advisory Circular 43.13-1A. To assist in making repairs, Figure 4-10 identifies the type and thickness of skin structure used. Never make a skin replacement or patch from a material thinner than the original skin. Original material and thickness is recommended and must result in a surface which is as strong as, or stronger than, the original skin. However, flexibility must be retained so that the surrounding areas will not receive extra stress. When making major structural repairs, other than using factory manufactured parts, it is recommended the manufacture.”
It’s only the Piper Service manuals produced for airplanes manufactured later than yours that address repairs on tail flight surfaces: (from a PA28-236 service manual)
“STRUCTURAL REPAIRS Structural repairs must be made in accordance with the regulations set forth in FAA Advisory Circular 43- 13-lA. To assist in making repairs or replacements, figure 51-1 identifies the type and thickness of various skin materials used. —WARNING— No access holes are permitted in any control surfaces. The use of patch plates or repairs of all movable tail surfaces is prohibited. The use of any filler material normally used for repair of minor dents and materials used for filling the inside of surfaces is also prohibited on all movable tail surfaces. Never make a skin replacement or patch plate from materials other than the type used on original skin. The repair must be as strong as the original skin and flexibility must be retained so the surrounding areas will not receive extra stress. “
Note there is no prohibition against patch repairs on ailerons or flaps. This is the latest PA 28 service manual information and should be enough for your IA to sign off the patch repairs.
If it’s suggested that these are major repairs, here are the definitions of major repairs: From FAR 43 Appendix A
(1) Airframe major alterations. Alterations of the following parts and alterations of the following types, when not listed in the aircraft specifications issued by the FAA, are airframe major alterations:
(i) Wings.
(ii) Tail surfaces.
(iii) Fuselage.
(iv) Engine mounts.
(v) Control system.
(vi) Landing gear.
(vii) Hull or floats.
(viii) Elements of an airframe including spars, ribs, fittings, shock absorbers, bracing, cowling, fairings, and balance weights.
(ix) Hydraulic and electrical actuating system of components.
(x) Rotor blades.
(xi) Changes to the empty weight or empty balance which result in an increase in the maximum certificated weight or center of gravity limits of the aircraft.
(xii) Changes to the basic design of the fuel, oil, cooling, heating, cabin pressurization, electrical, hydraulic, de-icing, or exhaust systems.
(xiii) Changes to the wing or to fixed or movable control surfaces which affect flutter and vibration characteristics.
As long as the aileron is within the balance limits, the patch should not affect either the flutter or vibrations characteristics (see xiii). If there’s any doubt, check to see that the aileron with the patch is within the balance limits as specified in the service manual.
According to table IV-II “Balancing Specifications” the static balance of an aileron on your PA 28-235 is +2 inch pounds fwd and -20 inch pounds aft.
I hope this answers your question.
Steve
