Non-Metallic Structures Flashcards
1
Q
Why must abrupt changes in the cross-sectional area of a wooden structural member be avoided?
A
Abrupt changes in the cross sectional area of a structural member concentrate stresses and can cause failure.
2
Q
How can you determine the slope of the grain in a piece of wood to be used in a wing spar?
A
Suitable wood for aircraft must have a slope that is not steeper than 1:15.
3
Q
How much pressure must be applied to a glue joint in a piece of softwood to produce a strong joint?
A
125 to 150 pounds per square inch.
4
Q
Why should sandpaper never be used when preparing a scarf joint in a wing spar for splicing?
A
The dust caused by sanding will plug the pores of the wood so the glue cannot get in to form a good bond.
5
Q
Why are light steel bushings often used in bolt holes in a wood wing spar?
A
The bushing keeps the spar from being crushed when the nut on the attachment bolt is tightened.
6
Q
Why should wooden wing spars be finished with a transparent varnish?
A
The transparent finish allows any decay or rot that develops in the wood to be detected.
7
Q
What effect does moisture have on a wood aircraft structure?
A
Moisture causes the wood to swell and crack as it dries out. It allows fungus to develop in the wood and cause it to decay.
8
Q
Which species of wood is considered to be the standard when comparing other woods for use in aircraft structure?
A
Sitka spruce.
9
Q
What is the basic difference between laminated wood and plywood?
A
In laminated wood, all of the grain runs in the same direction. In plywood, the grain in the layers cross the others at a 90° or a 45° angle.
10
Q
Which wood is more inclined to warp, flat grain or vertical grain?
A
Flat grain.
11
Q
What are three types of wood used in aircraft structures?
A
Spruce
Douglas fir
Noble fir
Western hemlock
Northern white pine
Port Orford white cedar
Yellow poplar
12
Q
What is the basic wood used for aircraft wing spars?
A
Sitka spruce.
13
Q
Can northern white pine be used as a substitute for spruce?
A
Yes, but it must be increased in size to compensate for its lower strength.
14
Q
How do you detect decay in a wood structure?
A
Stick a sharp-pointed knife blade in the suspect area and pry the wood up. If the wood is good, it will come up as a long splinter; if it is decayed it will come up as a chunk.
15
Q
Are mineral streaks in a piece of structural aircraft wood reason for rejecting the wood?
A
No, if there is no evidence of decay in the wood.
16
Q
How is compression wood identified?
A
It has a high specific gravity, it appears to have an excessive growth of summerwood, and it has little contrast between springwood and summerwood.
17
Q
Is a hard knot that 1/2-inch in diameter allowed if it is in the web of a wing spar?
A
No, 3/8-inch diameter is the maximum allowable knot, and it must meet severe restrictions.
18
Q
Are pin knot clusters allowable in aircraft structural wood?
A
Yes, if they cause only a small effect on grain direction.
19
Q
What kind of glue is recommended for making repairs to a wood aircraft structure?
A
synthetic resin or resorcinol glue.
20
Q
What reference material may be used for acceptable repairs to wood aircraft structure?
A
AC 43.13-1B, Chapter 1.
21
Q
How is a scarf splice on a wing spar reinforced?
A
Solid spruce or birch plywood reinforcing plates are glue to each side of the spar, centered at each end of the scarf.
22
Q
What is the correct repair to a wooden aircraft wing spar if the wing-attach bolt holes in the spar are elongated?
A
Splice in a new section of the spar and drill new holes.
23
Q
What is the minimum taper to use when repairing a wood wing rib cap strip?
A
12 times the thickness recommended; 10 times is the minimum.
24
Q
How is aircraft plywood prepared for making a compound bend?
A
Soak the wood in hot water until it is pliable.
25
What is used to apply pressure to a glued joint when splicing a wood aircraft wing spar?
Cabinetmakers' parallel clamps.
26
What kind of repair is recommended for a hole in the plywood skin of aircraft wing?
A scarf patch.
27
What is the recommended taper for a scarf patch in a plywood aircraft skin?
12 to 1.
28
What is largest hole in a plywood wing skin that can be repaired with a fabric patch?
1-inch in diameter.
29
How long should a glue joint be kept under pressure when splicing a wood aircraft wing spar?
For at least 7 hours.
30
Which area of a wood wing spar must not contain any splice?
There must be no splice under wing attach fittings, landing gear fittings, engine mount fittings, or lift and interplane strut fittings.
31
What is the recommended taper for a splayed patch in a plywood aircraft skin?
5 to 1.
32
What is done to a splice in a wood aircraft wing spar to strengthen the splice?
Reinforcing plates are glued to both sides of the splice.
33
When an aircraft is being recovered, when is fungicidal dope applied to the fabric?
With the first coat of dope that is brushed into the fabric
34
What is the recommended type of repair to a fabric covered aircraft surface when it has an L-shaped tear, with each of the legs of the tear more than 14 inches long?
If the never-exceed speed of the aircraft is less than 150 miles per hour, a doped-on repair can be made.
35
How is aircraft performance related to the determination of appropriate fabric covering?
Aircraft wing loading and certified never exceed speed determine the fabric strength requirements.
36
What reference material may be used for acceptable covering methods for fabric-covered aircraft structure?
AC 43.13-1B, Chapter 2.
37
What are three types of fabric that can be used to cover an aircraft?
Cotton, polyester, and glass fabric.
38
What material is used for the inter-rib bracing in a fabric-covered aircraft wing?
Cotton reinforcing tape.
39
What are the two basic types of dope used on fabric-covered aircraft?
Nitrate dope and butyrate (cellulose acetate butyrate, or CAB) dope.
40
What kind of dope is used on polyester synthetic fabric that has been heat-shrunk on an aircraft structure?
Non-tautening butyrate dope.
41
What type of fabric is most widely used for covering aircraft structures?
Heat-shrinkable polyester fabric.
42
What is the preferred seam used for machine-sewing pieces of aircraft fabric together?
The French fell seam.
43
Should a sewed seam in the fabric used to cover an aircraft wing run spanwise or chordwise?
both spanwise and chordwise seams are permissible, but chordwise seams are preferred.
44
What type of hand-sewing stitch is used when sewing in a panel of new fabric on an aircraft fabric-covered wing?
A baseball stitch, locked every eight to ten stitches.
45
What is meant by the selvage edge of a piece of fabric?
It is the woven edge of fabric used to prevent the material unraveling during normal handling.
46
What is an antitear strip, and when are they required on a fabric-covered aircraft?
An antitear strip is a strip of the same type of fabric as is used for covering the wings. It is laid over the rib between the reinforcing tape and the fabric. An antitear strip is required for aircraft that have a never-exceed speed in excess of 250 mph.
47
Why are some portions of the structure of an aircraft dope proofed before they are covered with fabric?
Dope proofing keeps the fabric from sticking to the structure when the first coat of dope is applied. The fabric normally sags enough to touch the structure before it begins to pull taut.
48
What are two methods of applying the fabric to the wing of an airplane?
The blanket method and the envelope method.
49
What material is used to cover the overlapping edges of the leading edge metal to protect the fabric?
Cloth tape.
50
How are the wrinkles pulled out of cotton fabric?
Wet the cotton with water and allow it to dry.
51
How is polyester fabric shrunk on the aircraft structure?
With heat from an iron.
52
Where are the drainage grommets located on a fabric-covered aircraft wing?
At the lowest point in each bay. It is customary to install a grommet on each side of a wing rib, on the underside of the wing, at the trailing edge.
53
How wide should the surface tape be that is used to cover the trailing edge of an aircraft wing?
Three inches wide.
54
What type of rib lacing cord is recommended for attaching cotton fabric to an aircraft structure?
Waxed linen cord.
55
What are two methods of attaching the fabric to the aircraft structure?
By sewing and with a cement.
56
What type of knot is used for locking the stitches that are used for rib lacing on fabric-covered aircraft wing?
A modified seine knot.
57
What determines the spacing of the rib lacing stitches on a fabric-covered aircraft wing?
The never-exceed speed of the aircraft.
58
why is the surface tape used on the trailing edge of control surfaces of some airplances notched?
since the edges of this tape face into the wind, it is possible that it could start to lift and form a very effective spoiler. If the tape is notched, it will tear off at a notch.
59
What is the purpose of the reinforcing tape used between the fabric and the rib lacing on an aircraft wing?
The reinforcing tape keeps the rib lacing cord from pulling through the fabric.
60
What areas of a fabric-covered aircraft are more susceptible to deterioration?
All areas exposed to the elements, and especially those exposed to UV radiation, such as the upper surface of the aircraft.
61
What is done to cotton and linen fabric to protect it from mildew?
The first coat of dope used on cotton and linen fabric has a mildewcide mixed in it.
62
Does rejuvenator restore strength to the fabric?
No, it only restores resilience to the finish.
63
What is the minimum strength to which aircraft fabric is allowed to deteriorate before it is considered to be unairworthy?
Fabric can deteriorate to 70% of the strength of the fabric required for the aircraft.
64
How is the strength of the fabric on an aircraft structure determined?
An approximate strength test can be made with an FAA-approved fabric punch tester, but the only wat to know for sure that the fabric has sufficient strength is by pull-testing a one-inch wide sample of the fabric.
65
What paperwork must be completed if an aircraft that was originally covered with Grade-A cotton fabric is re-covered using a synthetic fabric?
The covering must be done according to a STC, and a Form 337 must be executed, stating that all materials and processes complied with the requirements of the STS.
66
When is the finishing tape applied to a fabric-covered wing when it is being recovered?
After the second coat of dope has dried and the nap of the fabric has been sanded off.
67
When are drainage grommets applied when an aircraft is being re-covered?
They are laid into the third coat of dope, at the same time the surface tape is applied.
68
What will happen if dope is sprayed over an enameled surface?
The thinner is the dope will penetrate the enamel surface and cause it to swell.
69
What can be done to remedy blushing that has formed on a doped surface that has just been sprayed?
Spray a very light mist coat of a mixture of one part retarder to two parts of thinner over the blushed area. Allow it to dry and spay on another coat. If this does not remove the blush, the blushed dope will have to be sanded off and new dope applied.
70
What is a rejuveenator?
A slow-drying finishing material that has potent solvents and plasticizers that soften a dried surface film and restore resilience to the film.
71
Why is the first coat of dope brushed onto the fabric?
To ensure thorough penetration and encapsulation of all of the fibers.
72
What is the general reason for runs and sags in a finish that is being sprayed onto a flat surface?
Too much dope is being applied to. The film is too thick.
73
What is the most common cause for dope roping?
The dope was improperly thinned or it was too cold.
74
What causes pinholes in a dope finish?
Excessive atomizing air pressure on the spray gun.
75
Why should the first coat of dope be thinned?
To ensure thorough penetration and encapsulation of all of the fibers.
76
Why aluminum pigmented dope used on fabric-covered aircraft?
to protect the clear dope and the fabric from the harmful effects of the sun.
77
Why should a fabric-covered surface be electrically grounded when dry-sanding it?
Dry-sanding can create enough static electricity of the surface that it can cause a spark and ignite the dope fumes inside the structure.
78
What instructions must be followed when covering and finishing an aircraft with materials specified in a STC?
The instructions that are a part of the STC.
79
What finishing materials must be used when recovering an aircraft using an STC?
The finishing materials specified by the STC.
80
How can water entrapped in a honeycomb structure be detected?
By the use of radiographic inspection.
81
What effect can entrapped moisture have on metal honeycomb structure?
Entrapped water can cause corrosion.
82
What type of nondestructive inspection is suitable for detecting internal damage in honeycomb material?
Ultrasonic inspection.
83
What is the simplest way to detect delamination in a composite structre?
Tap the surface with the edge of a coin. If the material is sound, the tapping will result in a clear ringing sound; but if it is delaminated, the sound will be a dull thud.
84
What are the types of defects than can be found in composite structures?
Manufacturing defects include delamination, resin-starved areas, resin-rich areas, blisters, air bubbles, wrinkles, voids, and thermal decomposition.
In-service defects include environmental degradation, impact damage, fatigue, cracks from local overload, debonding, delamination, fiber fracturing, and erosion.
85
What are two advantages of laminated construction over riveted sheet metal?
Light weight and rigidity.
86
What are two popular types of core material used in laminated structure?
Foam and honeycomb.
87
What are two popular types of matrix material used in laminated structure?
Polyester and epoxy resins.
88
What are the two parts of a polyester matrix material?
Resin and catalyst.
89
What are the two parts of an epoxy matrix material?
Resin and hardener.
90
What are three materials that may be used to reinforce the matrix material for aircraft structure?
Fiberglass, Kevlar, and graphite.
91
What is meant by a unidirectional fabric?
A fabric in which all of the major fibers run in the same direction.
92
What is meant by the ribbon direction of a honeycomb material?
The direction in a piece of honeycomb material that is parallel to the length of the strips of material that makes up the core.
93
What is meant by the shelf life of a material.
The normal length of time a material can be expected to keep its usable characteristics if it is stored and not used.
94
What is meant by the pot life of a resin?
The length of time a resin will remain workable after the catalyst has been added.
95
Where are pre-impregnated (prepreg) materials normally stored?
In a freezer, at temperatures specified by the manufacturer.
96
What kind of repair can be made to a small damage of the core material and one face sheet of a piece of aluminum alloy honeycomb structure?
A potted compound repair.
97
How do you grind the point of a twist drill that is to be used for drilling transparent acrylic material?
The cutting edge should be dubbed off to a zero rake angle, and the included angle of the tip should be ground to 140 degrees.
98
What is a warp clock in a structural repair manual?
An alignment indicator to show the orientation of the plies of a composite material. The ply direction is shown in relation to a reference direction.
99
What are two types of repair to a damaged honeycomb core composite materia?
Room-temperature cure repair and hot-bond repair.
100
Of what class of resins are aircraft windows and windshields made?
Thermoplastic.
101
What is meant by crazing of a transparent plastic material?
Tiny hair-like cracks that may not extend all of the way to the surface. Crazing is caused by stresses or chemical fumes.
102
How should sheets of transparent plastic material be stored?
Leave the protective paper on the material and store it tilted approximately 10° from the vertical.
103
What are the two types of resins used in aircraft construction?
Thermoplastic and thermosetting.
104
What is necessary to cure a thermosetting resin?
Heat.
105
How tight should the screws be tightened when installing an acrylic windshield in a channel?
Tighten the screw to a firm fit and back if off one full turn.
106
What type of material is ued to remove surface damage to a piece of acrylic resin?
Micro-mesh abrasive sheets.
107
What type of transparent plastic material is used for most aircraft windshields?
Acrylic plastic.
108
What are the proper methods of repairing windows?
A temporary repair can be made by first stop-drilling the crack, drilling small holes along the crack, and lacing with brass safety wire. Another method of a temporary repair is to stop drill the cracks and clamp the crack together with machine screws, nuts, and washers. In both cases, fill the cracks with clear silicone to waterproof the repair.
109
What special precautions must be taken when repairing a radome?
Nothing must be done to the radome that will affect its electrical transparency or its aerodynamic strength.
110
What document lists the safety of hazards associated with a resin used in composite structure?
The MSDS for that resin.
111
What are the critical areas of inspection on seat belts, shoulder harnesses, and aircraft upholstery?
-Verify that seat belts are manufactured in accordance with TSO C22.
-Inspect belt webbing for fray and tears.
-Inspect buckles and inserts for condition and wear.
-Inspect upholstery for condition and wear. Replace upholstery only with fire-resistant materials approved for aircraft use.
112
Why is it important to select the appropriate glue or fastener for aircraft structures?
The use of any glue or fastener not specified by the aircraft manufacturer may render the aircraft unairworthy and unsafe.
113
Explain the risk associated with composite structural repairs and how to mitigate the risks.
It is critical that structural repairs are accomplished in accordance with the aircraft manufacturer's instructions or with FAA guidance. Repairs that are not made in accordance with approved data may be unairworthy and unsafe.
114
What PPE should be used when performing a composite repair?
Eye protection, breathing protection, and protection of skin and clothing. If power equipment is in use, use hearing protection.
115
What factors should be considered in the storage of composite materials?
Most composite materials have shelf-life limitations that are dependent on proper climate control. Some materials, such as prepregs, should not be kept in a freezer at temperatures specified by the manufacturer. Any time spent outside of the freezer should be tracked and recorded in accordance with material specifications.
116
What are the possible results of improper measuring or mixing of materials used with composite construction?
A resin-rich application can add unnecessary weight. A resin-starved application will show the fibers through the surface. Improper measuring or mixing of materials can compromise the bond and strength.
117
Why is it important to only use materials that are approved for a composite repair?
Is it critical that composite repairs are accomplished in accordance with the aircraft manufacturer's instructions or with FAA guidance. Repairs that are not made in accordance with approved data may be unairworthy and unsafe.
118
What are the risks of using materials that have an expired shelf-life?
The material properties of the expired materials will begin to degrade and strength and adhesion qualities may suffer.
