Chapter 2: Airplane Instruments, Engines, and Systems
A. COMPASS TURNING ERROR
1) During flight, magnetic compasses can be considered accurate only during straight-
and-level flight at constant airspeed.
2) The difference between direction indicated by a magnetic compass not installed in an
airplane and one installed in an airplane is called deviation.
i. Magnetic fields produced by metals and electrical accessories in an airplane
disturb the compass needles.
3) In the Northern Hemisphere, acceleration/deceleration error occurs when on an east
or west heading. Remember ANDS: Accelerate North, Decelerate South.
i. A magnetic compass will indicate a turn toward the north during acceleration
when on an east or west heading.
ii. A magnetic compass will indicate a turn toward the south during deceleration
when on an east or west heading.
iii. Acceleration/deceleration error does not occur when on a north or south
heading.
4) In the Northern Hemisphere, compass turning error occurs when turning from a north
or south heading.
i. A magnetic compass will lag (and at the start of a turn indicate a turn in the
opposite direction) when turning from a north heading.
1. 1) If turning to the east (right), the compass will initially indicate a turn
to the west and then lag behind the actual heading until your airplane is
headed east (at which point there is no error).
2. 2) If turning to the west (left), the compass will initially indicate a turn
to the east and then lag behind the actual heading until your airplane is
headed west (at which point there is no error).
ii. A magnetic compass will lead or precede the turn when turning from a south
heading.
iii. Turning errors do not occur when turning from an east or west heading.
5) These errors diminish as the acceleration/deceleration or turns are completed.
B. PITOT-STATIC SYSTEM
1) The pitot-static system is a source of pressure for the
i. Altimeter.
ii. Vertical-speed indicator.
iii. Airspeed indicator.
2) The pitot tube provides impact (or ram) pressure for the airspeed indicator only.
3) When the pitot tube and the outside static vents or just the static vents are clogged,
all three instruments mentioned above will provide inaccurate readings.
4) If only the pitot tube is clogged, only the airspeed indicator will be inoperative.
, C. AIRSPEED INDICATOR
1) Airspeed indicators have several color-coded markings
(Figure 4).
2) The white arc is the full flap operating range.
i. The lower limit is the power-off stalling
speed with wing flaps and landing gear in
the landing position (VS0).
ii. The upper limit is the maximum full flaps-
extended speed (VFE).
3) The green arc is the normal operating range.
i. The lower limit is the power-off stalling speed in a specified configuration
(VS1). This is normally wing flaps up and landing gear retracted.
ii. The upper limit is the maximum structural cruising speed (VNO) for normal
operation.
4) The yellow arc is airspeed which is safe in smooth air only.
i. It is known as the caution range.
5) The red radial line is the speed that should never be exceeded (VNE).
i. This is the maximum speed at which the airplane may be operated in smooth
air (or under any circumstances).
6) The most important airspeed limitation which is not color-coded is the maneuvering
speed (VA).
i. The maneuvering speed is the maximum speed at which full deflection of
aircraft controls can be made without causing structural damage.
ii. It is usually the maximum speed for flight in turbulent air.
D. ALTIMETER
1) Altimeters have three hands (e.g., as a clock has the hour, minute, and second hands;
2) The three hands on the altimeter are the
i. 10,000-ft. interval (short needle).
ii. 1,000-ft. interval (medium needle).
iii. 100-ft. interval (long needle).
3) Altimeters are numbered 0-9.
4) To read an altimeter,
i. First, determine whether the short needle points between 0 and 1 (1-
10,000), 1-2 (10,000-20,000), or 2-3 (20,000-30,000).
ii. Second, determine whether the medium needle is between 0 and 1 (0-
1,000), 1 and 2 (1,000-2,000), etc.
iii. Third, determine at which number the long needle is pointing, e.g., 1 for
100 ft., 2 for 200 ft., etc.
A. COMPASS TURNING ERROR
1) During flight, magnetic compasses can be considered accurate only during straight-
and-level flight at constant airspeed.
2) The difference between direction indicated by a magnetic compass not installed in an
airplane and one installed in an airplane is called deviation.
i. Magnetic fields produced by metals and electrical accessories in an airplane
disturb the compass needles.
3) In the Northern Hemisphere, acceleration/deceleration error occurs when on an east
or west heading. Remember ANDS: Accelerate North, Decelerate South.
i. A magnetic compass will indicate a turn toward the north during acceleration
when on an east or west heading.
ii. A magnetic compass will indicate a turn toward the south during deceleration
when on an east or west heading.
iii. Acceleration/deceleration error does not occur when on a north or south
heading.
4) In the Northern Hemisphere, compass turning error occurs when turning from a north
or south heading.
i. A magnetic compass will lag (and at the start of a turn indicate a turn in the
opposite direction) when turning from a north heading.
1. 1) If turning to the east (right), the compass will initially indicate a turn
to the west and then lag behind the actual heading until your airplane is
headed east (at which point there is no error).
2. 2) If turning to the west (left), the compass will initially indicate a turn
to the east and then lag behind the actual heading until your airplane is
headed west (at which point there is no error).
ii. A magnetic compass will lead or precede the turn when turning from a south
heading.
iii. Turning errors do not occur when turning from an east or west heading.
5) These errors diminish as the acceleration/deceleration or turns are completed.
B. PITOT-STATIC SYSTEM
1) The pitot-static system is a source of pressure for the
i. Altimeter.
ii. Vertical-speed indicator.
iii. Airspeed indicator.
2) The pitot tube provides impact (or ram) pressure for the airspeed indicator only.
3) When the pitot tube and the outside static vents or just the static vents are clogged,
all three instruments mentioned above will provide inaccurate readings.
4) If only the pitot tube is clogged, only the airspeed indicator will be inoperative.
, C. AIRSPEED INDICATOR
1) Airspeed indicators have several color-coded markings
(Figure 4).
2) The white arc is the full flap operating range.
i. The lower limit is the power-off stalling
speed with wing flaps and landing gear in
the landing position (VS0).
ii. The upper limit is the maximum full flaps-
extended speed (VFE).
3) The green arc is the normal operating range.
i. The lower limit is the power-off stalling speed in a specified configuration
(VS1). This is normally wing flaps up and landing gear retracted.
ii. The upper limit is the maximum structural cruising speed (VNO) for normal
operation.
4) The yellow arc is airspeed which is safe in smooth air only.
i. It is known as the caution range.
5) The red radial line is the speed that should never be exceeded (VNE).
i. This is the maximum speed at which the airplane may be operated in smooth
air (or under any circumstances).
6) The most important airspeed limitation which is not color-coded is the maneuvering
speed (VA).
i. The maneuvering speed is the maximum speed at which full deflection of
aircraft controls can be made without causing structural damage.
ii. It is usually the maximum speed for flight in turbulent air.
D. ALTIMETER
1) Altimeters have three hands (e.g., as a clock has the hour, minute, and second hands;
2) The three hands on the altimeter are the
i. 10,000-ft. interval (short needle).
ii. 1,000-ft. interval (medium needle).
iii. 100-ft. interval (long needle).
3) Altimeters are numbered 0-9.
4) To read an altimeter,
i. First, determine whether the short needle points between 0 and 1 (1-
10,000), 1-2 (10,000-20,000), or 2-3 (20,000-30,000).
ii. Second, determine whether the medium needle is between 0 and 1 (0-
1,000), 1 and 2 (1,000-2,000), etc.
iii. Third, determine at which number the long needle is pointing, e.g., 1 for
100 ft., 2 for 200 ft., etc.
