Estructura De Madera

and the wood structure). The mechanic should also look for evidence of swelling or warpage of the aircraft’s wood structure, which would indicate underlying damage or decay. Particular attention should be paid to the wood structure immediately beneath the upper surfaces, especially under areas that are finished in dark colors, for signs of deteriorating adhesives. Cracks in wood spars are oftenhidden under metal fittings or metal rib flanges and leading edge skins. Any time a reinforcement plate exists that is not feathered out on its ends, a stress riser exists at the ends of the plate. A failure of the primary structure can be expected to occur at this point.

b. Tapping the wood structure with a light plastic hammer or screwdriver handle should produce a sharp solid report. If thesuspect area sounds hollow and soft, further inspection is warranted by the following methods.

c. Probe the area in question, if accessible, with a sharp metal tool. The wood structure
Should be solid and firm. If the suspect area feels soft and mushy the mechanic should
Assume that the area is rotted. Disassembly of the structure is warranted at this point.

d. Prying the area of a bondjoint will reveal any mechanical separation of the joint. If
the mechanic detects any relative movement between two adjacent wood members, a failure of the bond is evident. Any loose fittings should arouse the mechanic’s suspicion, and the fittings should be removed to check for elongated bolt holes. Disassembly is warranted for further inspection.

e. Odor is an important indicator ofpossible deterioration. During the initial inspection,
as the access panels are being removed from the structure, the mechanic should be aware of any areas that smell musty or moldy. These odors are indicative of the presence of moisture and associated fungal growth and decay.

f. Visual inspection requires looking at the wood structure both externally and internally
for visual signs of decay orphysical damage. Any accumulations of dirt, bird nests, or rodent nests are likely places to hold moisture and promote decay.

(1) The mechanic should remove any such accumulations that are found and inspect
the area for signs of decay. Decay will appear as a dark discoloration or gray stains running
Along the grain and often a swelling of the wood member if still wet. Fittings will be imbeddedin the wood instead of flush.

(2) Highly suspected structurally damaged areas are shown in figure 1-3. A list of most likely areas to incur structural damage include the following:

(a) Check front and rear spars for compression cracks adjacent to the plywood reinforcing plates, where the lift struts attach, and at the rib attach points on either side of the strut attach points. Triple-checkthese areas and the spar to fuselage attach points for cracks if the wingtip has contacted the ground, a hangar wall, etc.

(b) Check all metal fittings which attach to wooden structure for looseness, corrosion, cracks, or warps. Areas of particular interest are strut attach fittings, spar butt fittings,
Aileron and flap hinges, jury strut fittings, compression struts, pulley brackets, andAny landing gear fittings.

(c) Check front and rear spars for longitudinal cracks at the ends of the plywood
Reinforcement plates where the lift struts attach. Triple-check this area if the wing has encountered any kind of ground strike.

(d) Check ribs on either side of strut attach points for missing or loose rib-to-spar
attach nails.

(e) Check ribs on either side of strut attachpoints for cracks where the cap strips
pass over and under the spars.

(f) Check for cracked leading edge skin and/or failed nose ribs in the area directly
in front of the jury strut.

(g) Check the brackets which attach the struts to the spars for cracks.

(h) Check the aileron, flap hinge, and hinge brackets for cracks and loose or missing
rivets.

(i) Check all exposed end grain wood,...