Orals Flashcards
What is the function of a vortex generator?
It is designed to delay or prevent separation of the boundary layer.
What are the three axes of an airplane?
Longitudinal, Lateral, and Vertical
What are the 3 primary flight controls of an aircraft?
Ailerons, Elevator, and rudder
Name several secondary flight controls and describe their general purpose.
Secondary flight controls consist of various types of trim tabs such as balance tabs, anti-servo and servo tabs, and spring tabs. Their function is to assist the pilot in moving the controls and trim the aircraft to fly hands off
Name several types of auxiliary flight controls and describe their general purpose.
The auxiliary flight controls consist of the various high-lift devices used during low-speed flight such as leading and trailing edge flaps, slats, slots, speed brakes, etc.
What is a servo trim tab?
It is an auxiliary control, positioned by the movement of a cockpit control and designed to create aerodynamic forces to assist in moving a control surface.
What is a spring tab?
It is an auxiliary control designed to aid the movement of a primary control at high speeds when control forces become too high
What is a balance trim tab?
It is an auxiliary control designed to create aerodynamic forces to assist in moving a control surface. The tab is positioned by a control rod connected to the fixed surface on the same side as the horn on the tab.
What are four most common types of high lift devices?
Leading and trailing edge flaps, slats, and slots.
Describe some of the tools used to check control surface travel.
A universal propeller protractor, or special control surface protractor.
Name three mechanical methods by which flight control systems may be actuated.
Cables, push pull rods, and torque tubes
What is a fairlead?
It is a device to prevent a cable from rubbing on the aircraft structure.
What are the most likely places for a control cable to wear or break?
Where the cables pass over pulleys or through fairleads.
What information is required before a cable rigging chart can be used?
The ambient temperature and the cable size.
What is the function of a cable tension regulator?
It automatically adjusts the cable tension to compensate for expansion and contraction in the aircraft structure.
Describe the function of a rotorcraft collective pitch control.
The collective control causes each rotor blade to change its pitch angle by the same amount, thus increasing or decreasing the lift produced by the rotor.
Describe the function of a rotorcraft cyclic pitch control.
The cyclic control tilts the main rotor disc by changing the pitch angle of each rotor blade during the cycle of its rotation, which causes the helicopter to move in the direction the rotor tilts
What mechanism is most commonly used to compensate for the torque produced by the main rotor of a helicopter?
The tail rotor
How is the amount of thrust produced by the tail rotor controlled?
By moving the foot pedals.
Why should control surfaces be locked when an aircraft is parked?
To prevent damage from the wind.
What is the major type of damage to aluminum structures that s caused by exposure to the weather?
Corrosion.
Name several methods for forming sheet metal.
Bending or folding, stretching, shrinking, bumping, and crimping.
What are the dimensions of a properly formed rivet head?
The head should be 1 1/2 times the shank diameter in width and 1/2 the shank diameter in height.
Describe the markings found on the heads of A, B, D, AD, and DD rivets.
A rivets are plain, B rivets have a cross, D rivets have a raised dot, AD rivets have a dimple, and DD rivets have double dash.
What happens to the stem of a self-plugging rivet when the rivet is installed?
The stem is pulled until it snaps off and the remaining projecting part is trimmed flush with the head.
Name at least 3 types of self-plugging mechanical lock rivets.
CherryMAX, CherryLOCK, OLYMPIC-LOK and Hucklok rivets
What is the difference between the tools required to pull a CherryLOCK rivet and a CherryMAX rivet?
CherryLOCK rivets require a tool for each different size and head shape, while one pulling tool will set any size CherryMAX rivet.
Which of the five stresses is the most common cause of rivet failure?
Shear.
If a 2024 rivet must e replaced with a 2117 rivet, how do you determine the size to be used?
For 5/32 or smaller diameter, use the next larger size 2117 rivet, assuming that the edge distance and spacing meet the minimum requirements
Describe the process for determining the total length of a solid rivet for a particular installation.
Add the grip length plus 1 1/2 times the rivet diameter.
What minimum edge distance and spacing should be used for a single row of protruding head rivets?
Not less tan 2 rivet diameters from the edge and not less than 3 rivet diameters apart
How can a mechanic determine whether the countersink for a flush rivet should be dimpled or drilled?
By the thickness of the top sheet; thin sheets are dimpled while thick sheets may be countersunk.
What action is taken to prevent cracks from forming while dimpling magnesium or some hard sheet metals?
Hot dimpling equipment is used to preheat and soften the metal before the dimple is formed.
What type of damage can occur when using a rivet set that does not properly fir the rivet?
If the radius of the set is too small, the rivet head may be damaged, whereas a set with an oversized radius may cause damage to the sheet metal.
Why is it important to use the proper size and weight bucking bar when performing sheet metal riveting?
If a bucking bar is too large or heavy it may be difficult to control and may cause damage to the surrounding structure, whereas a buking bar that is too light will not properly upset the rivet before work hardening occurs.
What procedures should be followed to properly remove a solid shank rivet?
Center punch the rivet and then drill just to the base of the rivet head with the same size or one size smaller drill. Once drilled, use a in punch to tip off the rivet head and drive the remaining shank out of the hole while supporting the surrounding metal
What are the two special calculations that must be made when bending sheet metal?
Bend allowance and setback.
What factors must be considered in order to determine setback?
The thickness of the metal and the bend radius.
What is done to a corner where two bends intersect to prevent cracking?
Relief holes are drilled in the corner
What are the 2 reasons for installing a lightening hole in a sheet metal wing rib?
Lightening holes reduce weight and increase stiffness.
When repairing an all metal aircraft, how do you determine what metals should be used?
Always use metal of the same type and thickness as the original structure.
What are the three forms of wood commonly used in aircraft construction?
Solid, laminated, and plywood.
What type of wood should be used when splicing or reinforcing plywood webs?
The same type of plywood as originally used
Name at least four different types of defects found in wood.
Knots, checks, splits, pitch pockets, cross grain, curly grain, decay, dry rot, etc.
Can a section of wood containing a hard knot be used?
Yes, within specified limits.
What type of glue may have been used in older wooden aircraft construction that requires careful inspection to detect deterioration?
Casein glue.
What are the 3 types of glues used in modern aircraft construction and repair?
Resorcinol glue, Phenol-formaldehyde glue, and epoxy resin glue.
Is compression wood acceptable for structural repairs?
No.
Why should the various pieces of wood being joined be kept in the same room for at least 24 hours prior to joining?
To allow the moisture content to equalize, thereby minimizing dimensional changes in the wood.
Why is it important to consider the open-assembly time when gluing wooden structures?
If the maximum open assembly time is exceeded, the joint may fail since he glue may begin setting up before the joint is assembled.
Why is it important to apply the proper clamping pressure to a glue joint?
Clamping forces air out of the joint, brings the wood surfaces together evenly and is, in part, responsible for the strength of the glue line.
Describe a joggle and explain its function.
A joggle is an offset formed at an intersection of two or more sheets of metal to allow the multiple sheets to be stacked flat against each other
Describe some methods used to apply pressure to glue joints.
Clamps, nailing strips, power presses, brads, nails, and small screws.
What minimum curing temperature should be observed when joining wood with various adhesives?
70 Fahrenheit or as specified by the glue manufacturer.
When inspecting wood structures, why might it be important to consider stains and discolored areas?
Stains and discoloration usually accompany decay and/or rot.
Describe the acceptable methods used to repair elongated bolt holes found in a wooden wing spar?
Remove the section containing the elongated hole and splice in a new section or replace the entire spar.
What type of joint is used to splice a solid or rectangular wood spar?
A scarf joint
In what areas are splice to a wood spar prohibited?
Under an attachment fitting for the wing root, landing gear, engine mount, lift, or inter-plane strut.
What is the maximum number of splices allowed for any single spar?
2
Describe the characteristics of a scarf joint.
The pieces to be joined are tapered or beveled on a slope of 1 to 10 or 1 to 12
Why must the beveled cut be accurate on both pieces of wood being repaired with a scarfed joint?
The two pieces must match exactly to ensure a tight glue joint.
What are two primary uses for plywood in aircraft construction?
Gusset plates and aircraft skin.
Provide examples of at least 3 types of plywood skin repairs.
Splayed patches, surface patches, plug patches, and scarfed patches.
What type of patch should be used to repair small holes in thin plywood skin if the skin is less than 1/10th inch thick?
A splayed patch should be used if the hole can be cleared out to a diameter of less than 15 thickness of the skin.
What should be done to prevent a plywood patch and the pressure plate from sticking together if glue is extruded from the joint?
Place a piece of waxed paper or vinyl plastic between the patch and the pressure plate.
Why are lightweight steel bushings sometimes used in wooden structures?
Bushings prevent the wood from being crushed when the bolts are tightened.
What is the purpose of large surface area washers when used on wooden structures?
Large washers provide additional bearing area for hardware to help preclude damage to wood when the hardware is tightened.
Name several facings and core materials used in bonded honeycomb structures intended for special applications.
Stainless steel, titanium, magnesium, plywood, glass, nylon, and cotton cloth.
Describe the construction of a bonded honeycomb structure.
It is a laminated structure that has a solid facing bonded to either side of a core consisting of open, six sided cells.
What must be done with a damaged area in a bonded honeycomb structure prior to beginning repairs?
The area must first be inspected to determine the damaged area prior to completely removing the damaged material.
A drill bit used for drilling composites should operate at approximately what speed?
Use an air-driven tool capable of a free speed of up to 20,000 rpm
What are the most common causes for delamination of a composite structure?
Sonic vibration, expansion of internal moisture, liquid leakage, and a manufacturing error.
What type of defect in, or damage to, a bonded honeycomb structure can be repaired using the potted repair method?
Filling a hole.
Name some of the factors that cause crazing in transparent plastic windows and windshields?
Exposure to UV light, stress, solvents, and improper handling.
How should a hole be drilled in Plexiglass to avoid damage to the hole when the drill breaks through the underside?
Back up the plastic with a piece of wood and feed the drill slowly.
Name he three principle types of welding.
Gas welding, electric arc, electric resistance
What are some advantages of gas shielded arc welding?
The weld is stronger, more ductile, and more corrosion resistant
Which method of welding is less likely to cause buckling or warping of thin metal sheets?
Electric arc welding
What is the purpose of shielding an arc weld with an inert gas?
The gas prevents atmospheric oxygen and or nitrogen from contaminating the weld.
What is a common method of controlling expansion when welding a joint?
Place tack weld along the length of the joint
What is the effect of inadequate penetration on a weld?
The weld will be weak.
Wha is the purpose of the flux used wth brazing and silver soldering?
Th flux cleans the base metal by removing any oxide film
What type of flame is used when torch brazing or silver soldering?
A neutral flame
What must be done to a soldering iron tip to increase the amount of heat transferred from the tip to the work?
The tip must be clean of all contaminants and properly tinned.
What is the preferred method for welding aluminum?
TIG Welding
What is the preferred method of welding magnesium?
TIG welding
What precautions must be observed in order to weld titanium?
All traces of oxygen and nitrogen must be kept away from the weld area.
Describe one type of repair that could be made to a dented steel tube cluster joint.
A formed steel patch plate could be welded over the damaged area.
How can a soft flame be obtained without reducing the heat output of the torch?
Use a larger tip and adjust the gas pressure accordingly.
What factors determine the amount of heat delivered by a gas welding torch?
The size of the torch tip and the gas pressure.
When an oxyacetylene torch is extinguished, which valve is turned of first?
Turn off the acetylene valve first.
When a gas welding project is completed, what safety precautions should be accomplished?
All the valves are turned off and the gas pressures are relieved.
What should be done to a heat treated aluminum part after welded repairs are completed?
The part must be reheat treated
Welding magnesium can create a serious safety hazard. What is the nature of this hazard?
Magnesium burns with a very hot flame that is hard to extinguish.
What technique might be used to enable a tight-fitting inner sleeve to be inserted into a tubular repair?
The inner tube could be chilled with dry ice or in a freezer while the outer tube could be heated slightly with a torch.
Aircraft covering fabrics are made of materials from what two sources?
Organic materials and synthetic materials
How would you determine the strength requirements for fabric used to recover an aircraft?
The fabric must be of at least the quality and strength of the fabric used by the original manufacturer.
What two types of organic fibers are used for covering aircraft?
Cotton and linen
What is meant by warp, weft, and bias?
Warp is the direction along the length of the fabric, weft is the direction across the fabric at right angles to the warp, and bias is a direction 45 degrees to the warp and weft.
What is the purpose of the selvage edge on a roll of fabric?
It prevents it from unraveling.
What identification marking is found on the selvage edge, and in which direction is the warp applied?
The FAA-PMA stamp is found on the edge and the warp is applied parallel to the line of flight.
How are the fabric type and strength requirements determined for fabric covered aircraft?
The original manufacturer determines the fabric type, and the strength requirements are a function of the never exceed speed and wing loading.
What types of synthetic fibers are used for covering aircraft?
Fiberglass and heat shrinkable polyester fibers
Which of the several types of fabric is unaffected by moisture and mildew?
Fiberglass
What is the function or purpose of reinforcing tape?
Reinforcing tape is used between the fabric and the rib stitching to prevent the lacing cord from cutting through the fabric.
Where could you use surface tape?
Over rib stitching and sewed seams, over lapped edges, around corners, along leading and trailing edges.
How should the edges of drainage, inspection, and ventilation holes be reinforced?
With plastic, aluminum, or brass grommets.
What are the principle methods used to test the condition of fabric?
Punch testers such as Maule or Seybolt, and laboratory pull testing
Fabric is considered unairworthy when it has deteriorated to what percentage of its original strength?
Less than 70 precent
How should a structure that will be covered with doped fabric be prepared following inspection and prior to covering?
Treat it with a protective coating of paint or varnish as appropriate
What is the principle advantage of the envelope method for covering wings?
Almost all the seams are machine sewed by the envelope supplier
What is a tie-off knot?
A standard, modified seine knot used on all stitches except the starting stitch
Name three common types of machine sewed seams
Plain overlap, folded fell, and French fell
Where are anti tear strips used?
Under wing rib stitching when the never-exceed speed is greater than 250 mph
How would you determine the correct spacing for rib stitching if the original spacing was unknown?
Consult the chart in AC 43.13 1B
Why is butyrate dope safer to use than nitrate dope?
It is much less flammable
What are the two types of dope used for fabric finishes?
Cellulose Nitrate and Cellulose Acetate Butyrate
What is the appearance of a blushing paint finish?
Chalky or cloudy
What finishing defect is the result of a paint room temperature that is too warm?
Pinholes or blisters
What causes dope to blush?
High humidity, moisture in the spray system, or application over a damp surface.
What factors cause spray paint sags and runs?
Inadequate surface preparation or paint sprayed on too thick
What components or parts of the airframe must be protected from damage when using paint stripper?
Windshields and windows, plastics, composites, synthetic rubber, and fabrics.
What is the function of zinc-chromate or wash primers?
Primers serve to inhibit corrosion and provide a good bond between the metal and the topcoats.
Name several common types of paint used on aircraft
Zinc chromate and wash primers, synthetic enamels, acrylic lacquer, and polyurethane
What is the proper thinner to use with zinc-chromate primer?
Toluene
What health and safety precautions must be observed when using the toxic solvents and thinners that are part of modern finishing systems?
Respirators and or masks must be worn when spraying finishes.
If spray painting dust causes a surface to appear dry and rough, what are the most likely causes?
Too much air pressure or the spray gun is too far from the surface being painted.
What causes “orange peel”
Spray pressure too high, use of a thinner that dries too fast, cold temperatures, or a damp draft over the surface.
What regulation governs the application of the registration numbers to aircraft registered in the United States?
FAR Part 45
Other than appearance, what is another reason for touching up painted surfaces?
Reduction or elimination of general corrosion problems.
What references should used to determine if a control surface must be checked and or rebalanced after painting?
The manufacturer’s service manual.
What would be the effect if dope was used over paint or enamel?
The dope tends to dissolve those materials.
What are the three most commonly used methods of applying paint?
Dipping, brushing, and spraying
What is the effect on paint finishes if too much drier is added to the paint?
The paint film will be brittle and tend to crack and peel.
What paint systems may be used with epoxy topcoats?
Any paint system in good condition.
What could cause an AC electric motor to run too fast?
Excessive applied voltage or shorted field windings.
What tool is used to check a motor or generator armature for shorts and opens under load conditions?
A growler.
When using a growler, what indication will occur when a short exists between an armature segment?
When a metal blade is held over the armature and a short exists in a segment, the blade will begin to vibrate and chatter
How is the output voltage of an alternator controlled?
By varying the field current that excites the alternator.
What instruments are used to monitor electrical system loads?
Ammeters and voltmeters
How would you identify a specific wire in a wire bundle?
By the identification code marked on the wire.
What tool would you use the determine the size of an unmarked wire?
A wire gauge