Airframe Oral Study Guide

What are four common basic stresses on an aircraft?

There are tension, compression, shear, and bearing.

What is a grip length of a rivet?

The grip length is the combined thickness of the materials to be joined by the rivet.

Where are special rivets such as huck or cherry lock rivets used?

they used where you cannot reach both sides of the structure, so a bucking bar cannot be used. They are called blind rivets.

What is bonded honeycomb construction?

Bonded honeycomb construction is a lightweight structure made of layers of metal or other materials bonded together in a honeycomb pattern to give strength while reducing weight

What type of materials are used in honeycomb construction?

stainless steel, titanium, magnesium, plywood, resin impregnated paper, e-glass, nylon in various combinations.

Where are sandwich construction assemblies used?

in control surfaces, fuselage panels, wing panels, empennage skins, or shear webs.

What calculations must be made when bending sheet metal?

Setback and bend allowance.

What factors are used to determine setback?

Bend radius and thickness of the material. (setback = radius + thickness)

When bending sheet metal, how should the grain be in relation to the bend?

The grain should be perpendicular to the bend.

What is a bend tangent line?

The line at which the metal starts to bend.

What is a joggle?

A joggle is a small bend in sheet metal that lets two or more pieces fit flat together.

What are several methods used in forming sheet metal?

Folding, bumping, crimping, shrinking and stretching.

What kind of metal forming is done by bumping?

Compound curves.

What are the proper dimensions for the shop head of a rivet?

1.5 times the diameter in width and 0.5 times the diameter in height after bucking.

Briefly describe the anodizing process and what purpose it serves.

Aluminum is put in an electrolytic solution to form a thin oxide layer, which protects against corrosion and helps paint stick

What size drill should be used for the common shank rivet diameters of 3/32 of an inch, 4/32 of an inch, 5/32 of an inch?

For a 3/32 rivet, a number 40. For a 4/32 rivet, a number 30. And for a 5/32 rivet, a number 21.

What is a lightning hole?

Is a hole cut in the structural parts to reduce weight and increase stiffness (strength)

When cutting a piece of sheet metal at the edge and you bend the corners in, what needs to be done?

You must drill a relief hole.

When riveting, what are some safety considerations to be made?

Wear safety glasses. Do not point the rivet gun. Wear gloves. And don't hold down the trigger.

What are the markings on rivet heads and what do they mean?

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 type of aircraft structure uses aircraft skin to support the load?

Monocoque.

What type of shielding gases are used for gas tungsten arc welding?

Helium and argon.

If you do a circle sheet metal patch with eight rivets, how many degrees apart should the rivets be?

45° apart.

How is the inner sleeve tube held in the structural tube until the gap is welded?

It is held in place with the rosette welds.

Why doesn't a TIG welder use flux?

It has helium shielding gas.

When opening an acetylene container, how many turns is the valve turned?

One and a half times.

Name an aircraft structure that a honeycomb panel can be used for.

They have a variety of uses on aircraft such as floor panel, bulkheads, and control surfaces as well as wing skin panels.

What is bonded honeycomb construction?

is a laminar construction consisting of a combination of alternating dissimilar materials assembled and fixed in relation to each other so that the properties of each can be used to attain specific structural advantages for the whole assembly while reducing weight.

What type of materials are used in honeycomb construction?

Honeycomb construction may employ stainless steel, titanium, magnesium, plywood, resin impregnated paper, e-glass, nylon, and various combinations.

Where are sandwich construction assemblies used?

They are used for such areas as bulkheads, control surfaces, fuselage panels, wing panels, radomes, empennage skins, or shear webs.

What procedure should be used to prevent damage to the hole when drilling through plexiglass?

place a piece of wood underneath for support and drill slowly

What is crazing and how does it occur?

is small hairline cracks on the surface of plastic caused by stress or improper handling, often from uneven heating.

When inspecting plexiglass, what should you look for?

Crazing and discoloration.

What causes honeycomb structures to delaminate?

Moisture.

What are the acceptable repair methods for bonded honeycomb structure that has been damaged?

the potted repair method and the laminated glass-fabric overlay repair

What is used for hole filling in a bonded honeycomb repair?

potting compound

What special precautions should be observed when repairing a radome (radar dome)?

The repair must retain its strength and electrical transparency.

Radome repairs must keep the structure strong and allow radar signals to pass through.

What is a warp line?

A highlighted strand in the fabric used for ply orientation.

Warp is the same direction as the length of the fabric.

What does pot life mean?

Pot life is the amount of time a resin stays workable after the hardener is added

What is a Barcol hardness tester?

is a device that pushes a small point into a material to see how hard it is, In metals, it measures hardness, and in composites, it can check how well the resin has cured

What is done to honeycomb before repairing?

Remove damaged honeycomb and either replace with potting compound or use a honeycomb replacement plug.

What is the difference between thermoplastics and thermosetting plastics?

Thermoplastics can be remelted and reformed. Thermosetting cannot.

What species of wood do you use for repair?

Spruce.

What does a metal bushing do in a wood structure?

It protects the wood.

What type of wood should be used for structural repairs in aircraft?

Soft wood.

What kind of wood is used in aircraft besides solid wood?

plywood or laminate

How do you repair pin holes in doped fabric?

by applying dope with a retarder over the pin holes

The silver layer on dope and fabric protects from what?

Antimicrobial rot.

What knot is used in fabric between the first and last knot?

Modified seine knot.

What happens to composites when you spill Skydrol on them?

Damage and delamination.

Are pin knot clusters allowable in aircraft structural wood?

Yes, if they cause only a small effect on grain direction.

What is the preferred seam used when machine sewing pieces of aircraft fabric together?

The French fell seam.

What are two types of fabrics used to cover aircraft?

Polyester and cotton.

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 is used, locking the thread every 8 to 10 stitches

What are two methods of attaching the fabric to the aircraft structure?

by sewing and with cement.

Why is a scarf joint angle and condition of wood spar repair important?

Strength of the repair.

What is the term for a piece of wood that has deteriorated to the point where when you crush it, it will turn into a dry powder?

Dry rot.

Pre-preg fabric in a freezer with a defrost cycle will do what?

Shorten the life of the fabric.

What are the benefits of envelopes on aircraft wings?

Time efficient.

What protective equipment do you wear when you work with carbon fiber or graphite?

Gloves and eye protection.

What happens to the fabric when the wood under it breaks?

The fabric cracks.

What two forms of stress are fabric sheets most susceptible to?

Tension and compression in relation to an aircraft.

What is the boundary layer?

It is part of the airflow close to the surface of the aircraft.

What are three types of commonly used flight control systems?

cable, the push-pull tube and the torque tube systems.

(The cable system is the most widely used because deflections of the structure to which it is attached do not affect its operation.)

What is used in large metal aircraft to keep control cable tension within acceptable limits?

A cable tension regulator.

What is a fairlead?

It is a device to prevent a cable from rubbing on the aircraft strcture.

How much cable deflection is acceptable due to a fairlead?

3°

Where does failure of control cables occur most frequently?

Where the cables pass over pulleys or through fairleads.

Which flight control surfaces are considered the primary group?

The elevators, the ailerons and the rudder.

Which flight controls are considered the secondary group?

The trim tabs, spring tabs, wing flaps, servo tabs, and the anti-servo tabs. They do not alone cause rotation of the aircraft about its axis.

Which flight controls are used in the auxiliary group?

Auxiliary flight controls include devices like flaps, slats, slots, and speed brakes.

Their purpose is to help the aircraft during low-speed flight, such as takeoff and landing, by increasing lift or slowing the aircraft down.

How do wing flaps affect landing speed and approach angle of an aircraft?

Flaps increase wing lift, allowing a slower landing speed and a steeper approach angle

What is a balance tab?

A balance tab is a small tab that moves opposite the control surface and uses air pressure to reduce the force the pilot must apply

What is a trim tab?

A trim tab is a small tab on the trailing edge of a control surface that reduces the force the pilot must apply to maintain a desired flight attitude.

what is servo trim tab

A servo trim tab is a small tab attached to a control surface. When the pilot moves the main control, the tab moves by using aerodynamic force

What is a spring tab?

A spring tab is a small tab that uses a spring to help control surface movement at high speeds.

What is the purpose of a collective pitch control in a helicopter?

It is used to change the pitch of the main rotor blades, therefore increasing or decreasing lift.

Why is it important for the blades of a helicopter rotor system to be tracked?

To reduce vertical vibrations.

What is the most efficient way to check a helicopter rotor for dynamic balance?

The use of a balance computer.

What unit on a helicopter is used to compensate for torque created by the main rotor?

The tail rotor.

What control operates the helicopter tail rotor?

The anti-torque pedals.

What are the three axes of an aircraft and which control surfaces cause the aircraft to move about each axis?

The three axes of an aircraft are longitudinal, lateral, and vertical; ailerons control roll about the longitudinal axis, elevators control pitch about the lateral axis, and the rudder controls yaw about the vertical axis.

When installing an aircraft bolt, what precautions would you take regarding the position of the bolt?

Install the bolt with the head up if vertical, and forward if horizontal, so it will not fall out if the locking device fails.

How is the propeller torque corrected for during assembly and rigging in some single engine aircraft?

Some aircraft have the leading edge of the vertical stabilizer offset to the center line to counteract engine torque.

What reference publications should be used to rig aircraft including the control system?

You should refer to the aircraft specifications or type certificate data sheet issued by the FAA and the maintenance manual issued by the manufacturer.

What are vortex generators?

Vortex generators prevent airflow separation from the upper surface of the wing.

What factors are used to determine the proper cable tension?

The size of the cable and the outside temperature.

Why do control surfaces need to be statically balanced?

Because an out-of-balance control surface can cause severe flutter.

What tool can be used to measure control surface travel?

A protractor or special control surface protractor.

What does a helicopter cyclic pitch control do.

The cyclic is used to control the main rotor to change the helicopter's direction of movement. move the helicopter forward, back, and laterally.

What will cause an aileron to flutter?

An out of balance condition on the aileron.

Where can you find the specifications for balancing the control surfaces of an airplane?

In the aircraft maintenance manual.

To establish conformity of an aircraft product, the mechanic must start with what document?

The type certificate data sheet.

What needs to be done to prepare an aircraft for an annual or 100-hour inspection?

Remove or open all necessary inspection plates, access doors, fairings, and cowlings. Then thoroughly clean the aircraft and the engine.

What is the difference between an annual and a 100-hour inspection?

Except for the difference in time between inspections and the person who can sign it off, there's no difference between the annual and the 100-hour inspection. They're identical in scope and detail.

Who has the authority to sign off and return to service a 100-hour inspection?

An appropriately rated mechanic may return an aircraft to service after a 100-hour inspection.

What are the operating conditions which make the 100-hour inspection mandatory?

aircraft that carry persons for hire or is used to give flight instructions for hire.

Where can you find a checklist for the 100-hour inspection?

In title 14, CFR part 43, appendix D.

Where would you find the recommended statement for recording the approval or disapproval for return to service of an aircraft after a 100-hour inspection?

In title 14 CFR part 43.11.

Who can approve an aircraft for return to service after an annual inspection?

An A&P mechanic who holds an inspection authorization certificate.