A&P - Airframe Oral Exam (Jeppesen)

What is the function of a vortex generator?

It is designed to delay of prevent separation of the boundary layer.

What are the three axes of an airplane?

Longitudinal, lateral, and vertical.

What are the three primary flight controls of an aircraft?

The ailerons, elevators, 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 primary 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 an 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 specal 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 strcture.

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 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 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 a control surface 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 method 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 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 tool for each different size and head shape, while one pulling tool will set and 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 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 (thickness or the materials being joined) 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 than 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 set is too small, the rivet head may be damaged, whereas a set with an over-sized 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 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 are the two special calculations that must be made 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 two reasons for installing a lightening hole in the sheet metal?

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 stacked flat against each other.

When repairing an all-metal aircraft, how do you determine what metal should be used?

Always use metal of the same type and thickness as the original structure.

What are 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 three types of glue uses 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 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 wood surfaces together evenly and is, in part, 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 Fahrenheit or as specified by the glue manufacturer.

When inspecting wood structues, why might it be important to consider stains and discolored area?

Stains and discoloration usually accompany decay and/or rot.

Describe the acceptable methods used to repair elongated bolts holes found in 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.

In what 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 maximum number of splices allowed for any single spar?

Two.

Describle 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 joint.

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

Gusset (or reinforcing) plates and aircraft skin.

Provide examples of at least three 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 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 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 bolts are tightened.

What is the purpose of large surface area washers when used on wooden structeres?

Large washers provide additional bearing area for hardware to help preclude damage to the 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 damaged area must be completely removed.

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

135 degrees.

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 ultraviolet light, stress, solvents, and improper handling.

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

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

Name the three principle types of welding.

Gas welding, electric arc welding, and electric resistance welding.

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 (or TIG) 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 common method of controlling expansion when welding a joint?

Place tack welds along the length of the joint.

What is the effect of inadeqate penetration on a weld?

The 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 of 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 contaminates and properly tinned.

What is the preferred method for welding aluminum?

Tungsten Inert Gas (TIG) welding.

What is the preferred method of welding magnesium?

Tungsten Inert Gas (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 off first?

Turn off the acetylene gas 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 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 covering fabrics are made of material from what two sources?

Organic materials and synthetic materials.

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 orginal 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 the fabric at right angles to the warp, and bias is a direction at a 45 degree angle to the warp and weft.

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

It prevents the fabric from unraveling.