Flight Instruments

Question 1

Pitot-Static System

Answer 1

Uses static pressure measured by the static vents and total pressure measured by the pitot tube

Question 2

Dynamic Pressure

Answer 2

Static pressure + dynamic pressure = total pressure

Question 3

Pressure Instruments

Answer 3

Altimeter
Airspeed Indicator
Vertical Speed Indicator

Question 4

Altimeter

Answer 4

Reference datum is MSL
Uses static vent (if blocked remains at same alt)
Bellows expand as altitude increases and air flows out of the chamber surrounding the bellows
Assumption that pressure reduces by 1hPa every 30ft

Question 5

Vertical Speed Indicator (VSI)

Answer 5

Uses the rate of change in static pressure to show rate of climb or descent
Outside air enters the capsule and the instrument case via a choke (takes longer) when descending
Pressures will equal when aircraft is level
Measured in feet per minute
Reads 0 if static vent is blocked

Question 6

Airspeed Indicator (ASI)

Answer 6

Uses the difference between total pressure and static pressure
Contains a diaphragm with total pressure and static pressure around it
Diaphragm expands and contracts
Errors if pitot tube or static vent become blocked (PUDSUC)
Measured in kts

Question 7

Instrument Lag on the VSI

Answer 7

Caused by a restricting diffuser in the pressure case

Resolved using an IVSI

Question 8

Alternate Static Source

Answer 8

Measures from inside the cabin when external static vent is blocked
ASI and Alt tend to over-read due to differences in pressure within the cabin (generally a lower pressure) and the outside

Question 9

Gyroscopic Instruments

Answer 9

The Artificial Horizon
The Turn Coordinator
The Directional Gyro

Question 10

Rigidity

Answer 10

Tendency to resist movement, stable on the spinning axis

Aeroplane rolls around the gyroscope

Question 11

Precession

Answer 11

When a force is applied, it will be felt 90 degrees in the plane of rotation

Question 12

Mechanical Drift

Answer 12

Due to wear

Question 13

Vaccum

Answer 13

Gyroscopes are run on a vacuum

The suction gauge indicates the pressure present in the vacuum system

Question 14

Artificial Horizon (AH)

Answer 14

Uses rigidity
Indicates pitch, roll and bank
Usually vacuum driven

Question 15

Directional Gyro (DG)

Answer 15

Indicates aircraft heading
Uses rigidity
Usually vacuum drives
Needs alignment and constant monitoring during flight due to the rotation of the Earth

Question 16

Apparent Drift

Answer 16

Gyro axis is aligned parallel to the meridian line and remains aligned to the same point in space, however the Earth is rotating

Question 17

Turn Coordinator (TC)

Answer 17

Indicates roll and yaw
Uses precession
Usually electrically driven

Question 18

Magnetic Compass

Answer 18

Aeroplane rotates around the compass

Shows heading according to magnetic north

Question 19

Magnetic Compass Deviation

Answer 19

Can be affected by any magnetic field that it is in causing a deviation from magnetic north
Corrected using a deviation card

Question 20

Compass Errors

Answer 20

Acceleration
Turning
Due to the lines of flux dipping toward the poles
In the southern hemisphere the CG is north of the pivot

Question 21

Acceleration Errors

Answer 21

SAND

Due to inertia causing the CG to lag and produces an apparent turn on the compass card

Question 22

Turning Errors

Answer 22

ONUS
Due to inertia causing the CG to lag behind and the centripetal force to accelerate the pivot in the direction of the turn