Instruments Oral

Question 1

What instruments in an aircraft are connected to the static system?

Answer 1

The airspeed indicator, the vertical speed indicator, and the altimeter.

Question 2

What types of repairs or alterations can a certificated A&P mechanic make to aircraft instruments?

Answer 2

None. All repairs and alterations must be made by the instrument manufacturer or by an FAA-approved repair station certificated for the particular instrument.

Question 3

What is the significance of a red radial line on the dial of an aircraft instrument?

Answer 3

A red radial line marks a never-exceed condition.

Question 4

What is the significance of a yellow arc on the dial of an aircraft instrument?

Answer 4

A yellow arc marks a caution range of operation.

Question 5

What is the significance of a green arc on the dial of an aircraft instrument?

Answer 5

A green arc indicates the normal range of operation.

Question 6

What is the significance of a white arc on the dial of an airspeed indicator?

Answer 6

A white arc on an airspeed indicator indicates the airspeed at which the flaps may be lowered.

Question 7

What is used to warn a mechanic that the glass on an aircraft instrument that contains the range marks has slipped?

Answer 7

A white slippage mark that extends across the lower part of the instrument cover glass and the instrument case bezel shows whether or not the glass has slipped. A slipped glass would put the range marks over the incorrect numbers.

Question 8

Where can a mechanic find the range markings that are required on the instruments in a particular aircraft?

Answer 8

TCDS.

Question 9

What check must be made if a mechanic replaces any instrument that is connected to the instrument static system?

Answer 9

Leak check.

Question 10

Why are many of the electrical instruments mounted in steel cases?

Answer 10

A steel case concentrates the flux produced by magnets in the instrument and keeps it from affecting other nearby instruments.

Question 11

Why must an aircraft instrument panel be electrically bonded to the primary aircraft structure?

Answer 11

The bonding straps carry the return current from the instruments into the aircraft structure.

Question 12

What error is corrected when an aircraft compass is swung?

Answer 12

Deviation error.

Question 13

What fluid is used in an aircraft magnetic compass?

Answer 13

A special water-clear fluid that is similar to kerosene.

Question 14

What is the maximum amount of deviation error that is allowed when a magnetic compass is installed in an aircraft?

Answer 14

10 degrees.

Question 15

What is the maximum amount of leakage that is allowed when checking the static system of an aircraft that is operated under Instrument Flight Rules?

Answer 15

For an unpressurized aircraft, it must not leak more than 100 feet in one minute. For a pressurized aircraft, it must not leak more than 2% of the equivalent altitude of the maximum differential pressure or 100 feet in one minute.

Question 16

Why must the length of the thermocouple leads not be altered when installing a cylinder head temperature indicator?

Answer 16

The resistance of the thermocouple and its leads must be kept at the indicators specified value because an instrument operated by a thermocouple is a current-measuring device.

Question 17

What should a manifold pressure gauge read when the engine is not operating?

Answer 17

The existing barometric pressure.

Question 18

What is the difference between a two-minute and a four-minute turn and slip indicator?

Answer 18

A two minute turn indicator gives a one-needle-width deflection for a half-standard rate of turn (1-1/2 degrees per second). A four-minute turn indicator has doghouse shaped marks located two needle widths away from the center mark, when the needle is lined up with a doghouse, the aircraft is making a standard rate turn.

Question 19

What is the difference between a turn and slip indicator and a turn coordinator?

Answer 19

A turn and slip indicator is sensitive about only the yaw (vertical) axis of the aircraft while A turn coordinator uses a canted gyro that makes it sensitive about both the roll and yaw axes.

Question 20

What is used as the sensor in the fuel tank for an electronic-type fuel quantity indicating system?

Answer 20

Tubular capacitors which extend across the fuel tank from top to bottom.

Question 21

Why is a dual tachometer used on a single-engine helicopter?

Answer 21

One needle indicates speed of the engine and the other indicates speed of main rotor, when needles are married the clutch will not slip and the rotor is solidly engaged to the engine.

Question 22

In what units is the tachometer used on a turbine engine calibrated?

Answer 22

In percentage of the takeoff RPM.

Question 23

What kind of system is used to measure the exhaust gas temperature of a turbine engine?

Answer 23

An averaging system made up of a series of thermocouples arranged around the inside of the exhaust duct of the engine.

Question 24

What would likely cause the needle of an electrical oil temperature gauge to peg on the high side of the
instrument dial?

Answer 24

There is probably an open in the bulb circuit that is causing the instrument to see an infinite resistance. The higher the resistance of the bulb circuit, the further the needle moves across the dial.

Question 25

What is used as a flowmeter for most of the small horizontally opposed fuel injected aircraft engines?

Answer 25

A pressure gauge that measures the pressure drop across the injector nozzles.

Question 26

What two sources of power are used to operate the gyro instruments in an aircraft?

Answer 26

They may be air operated, either by suction or pressure, or they may be electrically operated.