Jeppesen A&P Airframe Oral Exam (CCC)

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?

Lateral, longitudinal, and vertical

What are the three 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 to 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. (when the primary control surface is moved in any direction, the tab automatically moves in the opposite direction, helping pilot move the control surface)

What are the four most common types of high lift devices?

Leading edge flaps, trailing edge flaps, slats, and slots

Describe some of the tools used to check control surface travel.

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 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 its cycle of 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, or anti torque, 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 is 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 1.5 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 a double dash

What happens to the stem of a self-plugging (friction lock) 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 three types of self-plugging mechanical lock rivets

CherryMAX, CherryLOCK, OLYMPIC-LOK, and HuckLok

What is the difference between the tools required to pull a cherryLOCK rivet and a CherryMAX rivet?

CherryLOCK rivets require a different size tool for each 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 be 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, as long as edge distance and spacing meet minimums

Describe the process for determining the total length of a solid rivet for a particular installation.

1.5 times the rivet diameter plus the grip length

What minimum edge distance and spacing should be used for a single row of protruding head rivets?

At least two rivet diameters from the edge and not less than three 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 fit the rivet?

If the radius of the rivet set is too small, the rivet head may be damaged. If it is too large, the sheet metal may be damaged.

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 if may be difficult to control and cause damage to the surrounding structure, where a bucking 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 pin punch to tip off the rivet head and drive the remaining shank out of the hole while supporting the surrounding metal

What two calculations must be made when bending sheet metal?

Setback and bend allowance

What factors must be considered to determine setback?

Bend radius and material thickness

What is done to a corner where two bends intersect to prevent cracking?

relief holes are drilled in the corner

What are the two reasons for installing a lightening hole in a sheet metal wing rib?

Lightening holes reduce the weight and increase stiffness

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 tacked flat against each other

What are three forms of wood commonly used in aircraft construction?

Solid, laminated, and plywood

What type of would 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

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 three types of glues used in modern aircraft construction and repair?

Resorcinol glue, phenol-formaldehyde, 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, minimizing dimensional changes

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 the 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 surfaces together evenly, and is responsible for the strength of the glue line

Describe some of the 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 degrees F or as specified by the manufacturer

When inspecting wood structures, why is it important to consider stains and discolored areas?

They usually accompany decay or rot

Describe the acceptable methods used to repair elongated bolt holes found in a wooden wing spar

Remove the section containing the elongated holes 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

Where are splices 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 max number of splices for a single spar?

2

Describe the characteristics of a scarf joint

The pieces 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 with a scarf joint?

They must match exactly for a tight glue joint

What are the two primary uses for plywood in aircraft construction?

Gusset (reinforcing) plates, and aircraft skin

Give three examples of plywood skin repairs

Splayed patches, surface patches, plug patches, 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 may be used if the hole can be cleared out to a diameter of less than 15 thicknesses 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 waxed paper or vinyl plastic between the patch and the plate

Why are lightweight steel bushings sometimes used in wooden structures?

Bushings prevent the wood from being crushed when 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 prevent damage to wood when 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, 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 made of open six sided cells.

What must be done with a damaged area in a bonded honeycomb structure before repairs?

Remove damaged area

A drill bit used for drilling composites should have an included angle of how many degrees?

135

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

UV light, stress, solvents, improper handling

How should a hole be drilled in plexiglas to avoid damage to the hole when the drill breaks through?

Back up the plastic with a piece of wood and feed the drill slowly

Name the three types of welding

Gas, electric arc, electric resistance

What are some advantages of shielded gas 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 (TIG) welding

What is the purpose of shielding an arc weld with an inert gas?

The gas prevents oxygen or nitrogen from contaminating the weld

What is a common method of controlling expansion when welding a joint?

Place tack welds along the length of the joint

What is the effect of inadequate penetration on a weld?

Weld will be weak

What is the purpose of the flux used with brazing and silver soldering?

The flux cleans the base metal by removing any oxide film

What type of flame is used when torch brazing or silver soldering?

Neutral flame

What must be done to a soldering iron tip to increase the amount of heat transferred from the tip to the work?

Tip must be cleaned of contaminates and tinned

What is the preferred method for welding aluminum?

Tungsten Inert Gas (TIG)

What is the preferred method of welding magnesium?

TIG

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 gas pressure

When an oxyacetylene torch is extinguished, which valve is turned off first?

Acetylene first

When a gas welding project is completed, what safety precautions should be accomplished?

All the valves turned off and the pressures relieved

What should be done to a heat treated aluminum part after welded repairs are completed?

The part must be re heat-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 very 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 fabrics are made of materials from what two sources?

Organic and synthetic

How would you determine the strength requirements for fabric used to re-cover an aircraft?

The fabric must be of at least the quality and strength of the fabric used by the original manufacturer.

What is meant by warp, weft, and bias?

Warp is the direction along the length of the fabric, weft is across the fabric at right angles, and bias is at a 45 degree angle to warp and weft

What two types of organic fibers are used for covering aircraft?

Cotton and linen

What is the purpose of the selvage edge on a roll of fabric?

It prevents the fabric from unravelling

What identification marking is found on the selvage edge on a roll of fabric, and in what direction is the warp applied?

The FAA-PMA stamp is on the selvage edge, and the warp is applied parallel to the line of flight