Airframe Flashcards
For maximum strength of a formed sheet metal fitting, should the bend be made along or across the grain of the metal?
Across the grain.
What determines the minimum bend radius that can be used when forming a sheet metal structural fitting?
The alloy, the metal thickness, and its hardness.
What is meant by the neutral axis in a sheet of metal?
A plane within the metal that neither stretches nor shrinks when the metal is being bent.
What is a mold line in the development of a flat pattern for a formed metal part?
An extension of the flat sides beyond the radius.
What is the bend tangent line?
A line in a flat pattern layout at which the bend starts.
What is meant by setback?
The distance the jaws of a brake must be set back from the mold line to form a bend.
What is meant by bend allowance?
The actual amount of metal in a bend. It is the distance between the bend tangent lines in a pattern layout.
What is a sight line?
A line drawn on a flat pattern layout within the bend allowance that is one bend radius from the bend tangent line.
What is the main function of throatless shears in an aircraft sheet metal shop?
Throatless shears are used to cut mild carbon steel up to 10-gauge, and stainless steel up to 12-gauge.
What kind of metal forming is done by a slip roll former?
Simple curves with a large radius.
What kind of metal forming is done by bumping?
Compound curves in sheet metal.
What must be done to the flanges when forming a curved angle?
The flanges must be stretched for a convex curve and shrunk for a concave curve.
When hand-forming a piece of sheet metal with a concave curve, where should the forming be started?
Start at the edges and work toward the center.
What is meant by a joggle in a piece of sheet metal?
A joggle is a small offset near the edge of a piece of sheet metal that allows the sheet to overlap another piece of metal.
What type of device is a Cleco fastener?
A patented fastener that is inserted in the rivet holes and used to hold two pieces of sheet metal together until they can be riveted.
What type of rivet may be used to replace a round head rivet in an aircraft structure?
A universal head rivet.
How long should a rivet be to join two pieces of sheet metal?
The combined thickness of the metal sheets plus 1-1/2 times the rivet shank diameter.
How can rivets be physically identified for part number and type of material?
The identifying mark on the head of an aluminum alloy rivet indicates the specific alloy used in the manufacture of the rivet.
What must be done to an aircraft fuel tank before it can be repaired by welding?
The gasoline fumes must all be purged from the tank by running live steam through it for at least 30 minutes, by soaking it in hot water, or by filling it with nitrogen or carbon dioxide.
What precaution should be taken when drilling out rivets on an airplane?
Do not allow the drill to enter into the space behind the structure, as the drill may cause damage to other structures or systems.
Should a riveted joint fail in shear or in bearing?
It should fail in shear. The rivets should shear before the sheet tears at the rivet holes.
What are two advantages of laminated construction over riveted sheet metal?
Light weight and rigidity.
What are two popular types of core material used in laminated structure?
Foam and honeycomb.
What are two popular types of matrix material used in laminated structure?
Polyester and epoxy resins.
What are the two parts of a polyester matrix material?
Resin and catalyst.
What are the two parts of an epoxy matrix material?
Resin and hardener.
What are three materials that may be used to reinforce the matrix material for aircraft structure?
Fiberglass, Kevlar®, and graphite.
What is meant by a unidirectional fabric?
A fabric in which all of the major fibers run in the same direction.
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 make up the core.
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.
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.
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.
What are two types of repair to a damaged honeycomb core composite material?
Room-temperature cure repair and hot-bond repair.
What must a mechanic give the owner or operator of an unairworthy aircraft after a 100-hour inspection?
A signed and dated list of all of the discrepancies that keep the aircraft from being airworthy.
Where can you find the recommended statement for recording the approval or disapproval of an aircraft after a 100-hour inspection?
In 14 CFR §43.11.
Under what conditions can an aircraft be operated with a 100-hour inspection overdue?
The aircraft can be operated for no more than 10 hours after an inspection is due for the purpose of flying it to a place where the inspection can be performed.
For how long can an aircraft be operated if a 100-hour inspection is overdue?
For no more than 10 hours. The time beyond the 100 hours must be subtracted from the time before the next inspection is due.
Under what conditions can an aircraft that is due for an annual inspection be operated?
It can only be flown when a special flight permit is issued.
What certification is required for a mechanic to approve an aircraft for return to service after a 100-hour inspection?
An Aviation Mechanic certificate with Airframe and Powerplant ratings.
What determines whether or not an aircraft must be given a 100-hour inspection?
Aircraft that carry persons for hire and aircraft that are used for flight instruction for hire must be given 100-hour inspections.
What is the difference between an annual inspection and a 100-hour inspection?
The inspections themselves are identical. An annual inspection can be conducted only by an A&P mechanic who holds an Inspection Authorization, while a 100-hour inspection can be performed by an A&P mechanic without an IA.
What certification is required for a mechanic to conduct an annual inspection and approve the aircraft for return to service after the inspection?
An Aviation Mechanic certificate with Airframe and Powerplant ratings and an Inspection Authorization.
Where does the air come from to operate the pneumatic deicer boots on a reciprocating-engine powered airplane?
From the discharge side of the air pump used to operate the gyro instruments.
What is meant by a wet vacuum pump used to power pneumatic deicer boots?
It is a vacuum pump that uses engine oil to lubricate its steel vanes. A dry vacuum pump uses carbon vanes, and it does not require any oil for lubrication.
What is the purpose of the oil separator in a deicer system?
Oil separators are used with wet vacuum pumps to remove the lubricating oil from the discharge air before this air is used in the deicer boots.
How are rubber deicer boots cleaned?
By washing them with mild soap and water.
How are rubber deicer boots attached to the leading edges of aircraft wings and tail surfaces?
They are bonded to the surface with an adhesive. Boots on the older aircraft were attached with machine screws and Rivnuts.
What is the sequence of inflation of a deicing boot system?
There are three tubes in a deicer boot, upper, center, and lower. The center tube inflates first with the upper and lower tubes a specified number of seconds later.
What is meant by a fully articulated rotor system?
It is a rotor system in which the individual blades are free to flap, drag, and feather.
What is meant by a semirigid rotor system?
A two-blade rotor system in which the blades can feather, but cannot flap or drag. The rotor hub is mounted on the mast with a teetering hinge that allows the entire rotor to rock as a unit.
What is meant by a rigid rotor system?
A rotor system that has freedom of motion about its feather axis only. The flexibility of the blades is sufficient to provide the needed flapping and dragging.
What is a progressive inspection?
An inspection of the same level as an annual inspection but approved by the FAA to be performed on a schedule that does not require the aircraft to be out of service for the time necessary to perform the entire inspection all at once.
What certification is required for a mechanic to conduct a progressive inspection?
An Aviation Mechanic certificate with Airframe and Powerplant ratings and an IA.
Where can you find the requirements for inspecting the altimeter and static systems of aircraft operated under instrument flight rules?
In 14 CFR Part 43, Appendix E.
Where can you find the requirements for inspecting the ATC transponder that is installed in an aircraft?
In 14 CFR Part 43, Appendix F.
What items must be inspected on a helicopter in accordance with the Instructions for Continued Airworthiness?
The drive shafts or similar systems, the main rotor transmission gear box, the main rotor and center section, and the auxiliary rotor.
What are the different types of corrosion and their identifying features?
a. Surface corrosion - General roughening, etching, or pitting, frequently accompanied by a powdery deposit of corrosion products.
b. Filiform corrosion - Worm-like traces of corrosion below the paint film.
c. Pitting corrosion - First shows as a white or gray powdery deposit. When cleared away, tiny holes or pits can be seen in the surface.
d. Dissimilar metal corrosion - Extensive pitting caused by the contact of two dissimilar metals in the presence of a conductor.
e. Concentration cell corrosion - Metal-to-metal joint corrosion, or corrosion of a spot on the metal surface covered by a foreign material.
f. Intergranular corrosion - An attack along the grain boundaries of an alloy.
g. Exfoliation corrosion - An advanced form of intergranular corrosion that shows up as a lifting up of the surface grains of the metal by the expanding corrosion below the surface.
h. Stress-corrosion/cracking - Corrosion caused by a constant or cyclic stress acting in conjunction with a damaging chemical environment.
i. Fretting corrosion - A corrosive attack that occurs when two mating surfaces begin to have a slight relative motion between them.
j. Fatigue corrosion - When a cyclic stress and a corrosive environment combine to reduce the life of the part through pitting and cracking.
k. Galvanic corrosion - Corrosion that occurs when two dissimilar metals make electrical contact in the presence of an electrolyte.
What are the two general classifications of corrosion that cover most specific forms?
Direct chemical attack and electrochemical attack.
What is the definition of a critical fatigue area of a control cable?
Any working length of a cable where the cable runs over, under, or around a pully, sleeve, or through a fairlead; or any section where the cable is flexed, rubbed, or worked in any manner; or any point within 1 foot of a swaged-on fitting.
What would cause the warning horn to sound when the throttles are pulled back, reducing the engine power for landing?
The warning horn will sound if any of the landing gears are not down and locked.
What is indicated by a red light in the landing gear position-indication portion of the annunciator panel?
The red light indicates that the landing gear is not in a safe condition for landing.
What information is given to a pilot to indicate that all of the landing gears are down and locked?
Three green lights are used on most aircraft to indicate that all three landing gears are down and locked.
Is a chevron seal a one-way or a two-way seal?
A one-way seal.
To which side of a chevron seal should the pressure be applied?
To the open side.
Is an O-ring seal a one-way or a two-way seal?
A two-way seal.
How can you be sure of getting an O-ring made of the correct material for a specific hydraulic component?
The O-ring must have the correct part number and it must have been obtained from a reputable source.
On which side of an O-ring should the backup ring be placed?
On the side away from the source of pressure.
What should be done to the sharp edges of threads and actuator pistons when installing O-rings?
The sharp edges should be covered with paper.
What are the two main gases that make up our atmosphere?
Nitrogen and oxygen.
What is used to check an oxygen system for leaks?
A special leak-detector liquid that is a form of non-oily soap.
Why must fittings in an oxygen system not be tightened to stop a leak when there is pressure on the system?
When the system is pressurized, the tubing is expanded slightly; if the fitting is tightened when it is expanded, it will likely leak when the pressure is reduced.
What kind of gaseous oxygen must be used to service an aircraft oxygen system?
Only aviators’ breathing oxygen. Hospital oxygen and welding oxygen contain too much moisture to be used.
What identification must be stamped on an oxygen bottle carried in an aircraft?
The identification DOT 3AA or DOT 3HT, the date of manufacture, and the date of all of the hydrostatic tests.
To what pressure and how often should DOT 3AA oxygen cylinders be hydrostatically tested?
They should be tested to 5/3 of their working pressure every three years.
To what pressure and how often should DOT 3HT oxygen cylinders be hydrostatically tested, and when should they be retired from service?
They should be tested to 3,083 psi every three years and retired from service after 15 years or 4,380 pressurizations, whichever occurs first.
What kind of lubricant can be used for installing fittings in an oxygen system component?
Teflon tape or a special water-base lubricant.
What is used to check for leaks after replacing a fitting in an oxygen system?
A special leak-detector liquid that is a form of non-oily soap.
What cleaning solutions can be used to clean parts used in an oxygen system?
Anhydrous ethyl alcohol, isopropyl alcohol, or freon.
What may be used to dry components in an oxygen system after they have been cleaned?
Water-pumped dry nitrogen.
What may be used to purge the lines in an oxygen system after it has been opened for servicing?
Water-pumped dry nitrogen.
What must be done before any maintenance can be done on an oxygen system?
The oxygen supply must be turned off at the bottle valve.
On what two frequencies does the emergency locator transmitter operate?
121.5 and 243.0 megahertz.
Where is the ELT transmitter normally located on an aircraft?
In the tail of the aircraft or as far aft as possible, so it will be least likely to be damaged in a crash.
How often should ELT batteries be replaced or recharged?
When the transmitter has been in use for more than 1 cumulative hour, when the battery expiration date has been reached, or when 50% of their useful life or charge has expired.
How can you know when an ELT battery must be replaced or recharged?
By the date marked on the outside of the transmitter.
How often must ELTs be inspected for proper installation, battery corrosion, operation of the controls and sensor, and the presence of the radiated signal?
Every 12 calendar months.
What causes an ELT to actuate?
An inertia switch that detects an impact parallel to the longitudinal axis of the aircraft as would occur in a crash.
How is an ELT tested to determine that it is working?
Actuate the test switch and listen on 121.5 or 243.0 MHz. Make the test during the first five minutes of the hour and do not allow the ELT to operate for more than 3 sweeps. If the ELT is operated outside of this time frame, you should contact the control tower before conducting the test.
What markings must appear near the filler opening of the fuel tanks on a reciprocating-engine-powered aircraft?
The word ‘Avgas’ and the minimum grade of fuel.
What markings must appear near the filler opening of the fuel tanks on a turbine-powered aircraft?
The words ‘Jet Fuel,’ the permissible fuel designations, the maximum permissible fueling supply pressure, and the maximum permissible defueling pressure.
Why is it important to drain all of the fuel sumps before the first flight of the day?
Water can condense in the fuel tanks and it must be drained out before the aircraft is safe for flight.
Is the procedure of draining the sumps with the aircraft in the ground attitude an assurance that all of the water is removed from the tanks?
No; some aircraft require special procedures to remove all of the water. Refer to the airplane flight manual or pilot’s operating handbook.
What must be done after a fuel system strainer has been cleaned or replaced?
The system must be tested for leaks by pressurizing the system with the boost pump, if one is used.
What must be done if the sump drains sample shows traces of jet fuel?
The fuel system must be drained and flushed out with the proper grade of aviation gasoline.
What is used as the sensor in the fuel tank for an electronic-type fuel quantity indicating system?
Tubular capacitors that extend across the fuel tank from top to bottom.
What is the principle upon which the electronic-type fuel quantity indicating system operates?
Tubular capacitors extending across the fuel tanks change their capacitance as the fuel level changes. The dielectric constant (k) of the fuel is approximately twice that of air.
What is used as a sensor in the fuel tank for the older resistance-type fuel quantity indicating system?
A variable resistor with an arm that is moved by a float riding on top of the fuel in the tank.
What is the purpose of a drip gauge in the fuel tank of a large aircraft?
The drip gauge allows a mechanic to check the fuel level in a tank from the bottom of the tank.
When must the fuel quantity indicating system indicate ‘zero’?
During level flight when the fuel in the tank is equal to the unusable fuel supply.
What size generator must be used in an aircraft electrical system if the connected electrical load is 30 amps, and there is no way of monitoring the generator output?
When monitoring is not practical, the total continuously connected electrical load must be no more than 80% of the rated generator output. This would require a generator with a rating of 37.5 amps. Practically, a 40-amp generator would be installed.
What is meant by ‘flashing’ the field of a generator?
Restoring the residual magnetism to the frame of the generator. This is done by passing battery current through the field coils in the direction it normally flows when the generator is operating.
What is meant by paralleling the generators in a multi-engine aircraft?
Adjusting the voltage regulators so all the generators share the electrical load equally.
What are three types of voltage regulators used with aircraft generators?
Vibrator-type, carbon-pile type, and solid state-type.
What is meant by a trip-free circuit breaker?
A circuit breaker that cannot be closed while a fault exists, regardless of the position of the operating handle.
What is meant by a slow-blow fuse?
A fuse that will allow more current than its rating to flow for a short period of time, but will open the circuit if more than its rated current continues to flow.
What is the function of a fuse or circuit breaker in an aircraft electrical circuit?
It protects the wiring from an excess of current. It will open the circuit if enough current flows to heat the wire.
What are two principles upon which circuit breakers operate?
Magnetic circuit breakers open a circuit when the current creates a strong enough magnetic field. Thermal circuit breakers open a circuit when the current causes enough heat.
What circuit in an aircraft electrical system is not required to have a circuit protective device?
The main circuit for starter motors, used during starting only.
Is an automatic-reset circuit breaker approved for aircraft electrical circuits?
No, a manual operation is needed to restore service after the circuit breaker has tripped.
How does a vibrator-type voltage regulator maintain a constant voltage?
When the voltage rises above the desired value, an electromagnetic relay opens and inserts a resistor in the generator field circuit, decreasing the field current and lowering the generator output voltage.
What two components are normally housed with a vibrator voltage regulator in a single-unit generator control?
A current limiter and a reverse-current cutout relay.
Where could you find the part number of a switch in an aircraft electrical system?
In the equipment table or bill of materials on the electrical circuit diagram for the aircraft.
What is the main disadvantage of aluminum wire over copper wire for use in an aircraft electrical system?
Aluminum wire is more brittle than copper. It is more subject to breakage when it is nicked or when it is subjected to vibration.
What size aluminum wire would be proper to replace a piece of four-gauge copper wire?
Two-gauge. When you substitute aluminum wire for copper wire, use a wire that is two gauge numbers larger.
What is the smallest size aluminum wire that is approved for use in aircraft electrical systems?
Six-gauge.
Can you substitute aluminum wire for copper wire?
Yes. However, you must use aluminum wire two wire gauge sizes larger to carry the same current. Aluminum wire should never be used in runs of three feet or less, or in communication and navigation systems.
Can wire in free air carry the same current as wire in a bundle?
Wire in free air may be used to a higher current level than the same size wire in a bundle. Always refer to an electrical wire size selection chart.
What are common causes of wire failure in a crimped connector?
The wire was not inserted far enough into the connector and/or the connector was excessively crimped.
What is one of the first things to check if an electrical component does not operate?
Always start with simple solutions and move to more complex. Is the component turned on? Is power available?
For example, if a light doesn’t function is the system turned on, is the aircraft electrical system energized, or is the bulb burnt out?
What may be provided by the manufacturer to assist in troubleshooting?
Manufacturers often provide a troubleshooting logic chart.
What are the four basic steps of troubleshooting?
Know how the system should operate. Observe the way the system is operating. Divide the system into smaller segments to isolate trouble. Look for the obvious problem first.
When routing a fluid line parallel to an electrical wire bundle, which should be on top?
The electrical wire bundle should be on top.
What are the colors and positions of aircraft position lights?
Left side/wing tip - red, Right side/wing tip - green, Aft - white.
What is the purpose of wing inspection lights?
To permit visual detection of ice formation on wing leading edges while flying at night.
How is ice kept from forming on the pitot tube of an airplane?
Pitot tubes are heated by electric current flowing through heater elements built into them.
How is ice prevented from forming on the windshield of modern jet transport airplanes?
The windshield has a heater element embedded in it. Electric current heats the windshield and keeps ice from forming on it.
Are pneumatic deicer boots operated before ice forms or after it has formed?
Pneumatic deicer boots are not operated until ice has formed over them. When the boot inflates, it breaks the ice, and the air flowing over the airfoil blows it away.
