Private Pilot Ground School

rangebeaverMécanique

22 févr. 2014 (il y a 3 années et 8 mois)

82 vue(s)

Private Pilot Ground
School

Section 2

Chris Tavenner CFI

www.tractorking.org

Engines Instruments and Systems

Magnetic Compass and

Compass errors


During flight, magnetic
compasses can be considered
accurate only during straight
-
and
-
level flight at constant
airspeed.



The difference between
direction indicated by a
magnetic compass not
installed in an airplane and
one installed in an airplane is
called
deviation
.


Magnetic fields produced by
metals and electrical
accessories in an airplane
disturb the compass needles.


Magnetic Compass and

Compass errors


In the Northern Hemisphere, acceleration/deceleration error occurs when on an east
or west heading.
Remember ANDS: Accelerate North, Decelerate South.



A magnetic compass will indicate a turn toward the north during acceleration when
on an east or west heading.



A magnetic compass will indicate a turn toward the south during deceleration when
on an east or west heading.



Acceleration/deceleration error does not occur when on a north or south heading.


Magnetic Compass and

Compass errors


In the Northern Hemisphere, compass
turning error occurs when turning from a
north or south heading.


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)

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)

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).


A magnetic compass will
lead

or precede
the turn when turning from a
south
heading
.


Turning errors do not occur when turning
from an east or west heading.


These errors diminish as the
acceleration/deceleration or turns are
completed.

Pitot
-
Static System


The pitot
-
static system is a source of
pressure for the

1.
Altimeter.

2.
Vertical
-
speed indicator.

3.
Airspeed indicator.



The pitot tube provides impact (or
ram) pressure for the airspeed
indicator only.



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.



If only the pitot tube is clogged, only
the airspeed indicator will be
inoperative.


Airspeed indicator

Airspeed indicators have several color
-
coded markings


The white arc is the full flap operating range.


1)

The lower limit is the power
-
off stalling speed with wing
flaps and landing gear in the landing position (VS0).

2)

The upper limit is the maximum full flaps
-
extended speed
(VFE).

The green arc is the normal operating range.

1)

The lower limit is the power
-
off stalling speed in a
specified configuration (VS1). This is normally wing
flaps up and landing gear retracted.

2)

The upper limit is the maximum structural cruising speed
(VNO) for normal operation.

The yellow arc is airspeed which is safe in smooth air
only.

1)

It is known as the caution range.

The red radial line is the speed that should never be
exceeded (VNE).

1)

This is the maximum speed at which the airplane may be
operated in smooth air (or under any circumstances).


The most important airspeed limitation which is
not

color coded is the maneuvering speed (VA).


The maneuvering speed is the maximum speed at
which full deflection of aircraft controls can be
made without causing structural damage.


It is usually the maximum speed for flight in
turbulent air.


Altimeter


Altimeters have three hands (e.g.,
as a clock has the hour, minute,
and second hands;).


The three hands on the altimeter
are the


10,000
-
ft. interval (short needle).


1,000
-
ft. interval (medium needle).


100
-
ft. interval (long needle).


Altimeters are numbered 0
-
9.


To read an altimeter,


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).


Second, determine whether the
medium needle is between 0 and 1
(0
-
1,000), 1 and 2 (1,000
-
2,000),
etc.


Third, determine at which number
the long needle is pointing, e.g., 1
for 100 ft., 2 for 200 ft., etc.


Types of Altitude


Absolute altitude is the altitude above the surface,
i.e., AGL.



True altitude is the actual distance above mean sea
level, i.e., MSL. It is not susceptible to variation with
atmospheric conditions.



Density altitude is pressure altitude corrected for
nonstandard temperatures.



Pressure altitude is the height above the standard
datum plane of 29.92 in. of mercury. Thus, it is the
indicated altitude when the altimeter setting is
adjusted to 29.92 in. of mercury (also written 29.92"
Hg).



Pressure altitude and density altitude are the same
at standard temperature.



Indicated altitude is the same as true altitude when
standard conditions exist and the altimeter is
calibrated properly.



Pressure altitude and true altitude are the same
when standard atmospheric conditions (29.92" Hg
and 15
°
C at sea level) exist.



When the altimeter is adjusted on the ground so
that indicated altitude equals true altitude at airport
elevation, the altimeter setting is that for your
location, i.e., approximately the setting you would
get from the control tower.

Setting the Altimeter


The indicated altitude on the
altimeter increases when you
change the altimeter setting to
a higher pressure and
decreases when you change
the setting to a lower pressure.


This is opposite to the
altimeter's reaction due to
changes in air pressure.



The indicated altitude will
change at a rate of
approximately 1,000 ft. for 1 in.
of pressure change in the
altimeter setting.


EXAMPLE: When changing
the altimeter setting from
29.15 to 29.85, there is a 0.70
in. change in pressure (29.85
-

29.15). The indicated altitude
would increase (due to a
higher altimeter setting) by
700 ft. (0.70 x 1,000).


Non Standard Temp/Pressure


Since altimeter readings are adjusted for changes in barometric
pressure but not for temperature changes, an airplane will be at
lower than indicated altitude when flying in colder than standard
temperature air when maintaining a constant indicated altitude.


On warm days, the altimeter indicates lower than actual altitude.


Non Standard Temp/Pressure



Likewise, when pressure
lowers en route at a
constant indicated
altitude, your altimeter will
indicate higher than
actual altitude until you
adjust it.


Remember, when flying
from high to low
(temperature or
pressure), look out below.


Low to high, clear the
sky.


Gyroscopic Instruments

Vacuum system

Gyroscopic Instruments

Attitude Indicator (AI)


The attitude indicator, with its miniature
aircraft and horizon bar, displays a picture of
the attitude of the airplane.



The relationship of the miniature aircraft to the
horizon bar is the same as the relationship of
the real aircraft to the actual horizon.



The relationship of the miniature airplane to
the horizon bar should be used for an
indication of pitch and bank attitude, i.e., nose
high, nose low, left bank, right bank.



The gyro in the attitude indicator rotates in a
horizontal plane and depends upon rigidity in
space for its operation.



An adjustment knob is provided with which the
pilot may move the miniature airplane up or
down to align the miniature airplane with the
horizon bar to suit the pilot's line of vision.



Gyroscopic Instruments

Turn Coordinator


The turn coordinator shows the
roll and yaw movement of the
airplane.



It displays a miniature airplane
which moves proportionally to
the roll rate of the airplane.
When the bank is held
constant, the turn coordinator
indicates the rate of turn.



The ball indicates whether the
angle of bank is coordinated
with the rate of turn.


Gyroscopic Instruments

Turn Coordinator


The heading indicator
is a gyro instrument
which depends on the
principle of rigidity in
space for its
operation.


Due to gyro
precession, it must be
periodically realigned
with a magnetic
compass.


Engine Temperatures


Excessively high engine temperature either in the air or on the ground will cause
loss of power, excessive oil consumption, and excessive wear on the internal
engine.




An engine is cooled, in part, by circulating oil through the system to reduce friction
and absorb heat from internal engine parts.




Engine oil and cylinder head temperatures can exceed their normal operating
range because of (among other causes)


Operating with too much power


Climbing too steeply (i.e., at too low an airspeed) in hot weather


Using fuel that has a lower
-
than
-
specified octane rating


Operating with too lean a mixture


The oil level being too low


Excessively high engine temperatures can be reduced by reversing any of the
above situations, i.e., reducing power, climbing less steeply (increasing airspeed),
using higher octane fuel, enriching the mixture, etc.


Engine Temperatures

Constant speed Propeller


The advantage of a constant
-
speed propeller (also known as
controllable
-
pitch) is that it permits
the pilot to select the blade angle
for the most efficient performance.




Constant
-
speed propeller
airplanes have both throttle and
propeller controls.



The throttle controls power output,
which is registered on the
manifold pressure gauge.



The propeller control regulates
engine revolutions per minute
(RPM), which are registered on
the tachometer.



To avoid overstressing cylinders,
excessively high manifold
pressure should not be used with
low RPM settings.

Manifold
pressure is
controlled
by the
Throttle

(power)

The Rpm is
controlled by
the prop lever

Engine Ignition system

“Magneto”


One purpose of the
dual
-
ignition system is
to provide for
improved engine
performance.



The other is
increased safety.


Carb Ice


Carburetor
-
equipped engines are more
susceptible to icing than fuel
-
injected
engines.


The operating principle of float
-
type
carburetors is the difference in air
pressure between the venturi throat
and the air inlet.


Fuel
-
injected engines do not have a
carburetor.


The first indication of carburetor ice on
airplanes with fixed
-
pitch propellers and
float
-
type carburetors is a loss of RPM.




Carburetor ice is likely to form when
outside air temperature is between 20
°
F
and 70
°
F and there is visible moisture or
high humidity.




When carburetor heat is applied to
eliminate carburetor ice in an airplane
equipped with a fixed
-
pitch propeller,
there will be a further decrease in RPM
(due to the less dense hot air entering
the engine) followed by a gradual
increase in RPM as the ice melts.


Carb Heat


Carburetor heat enriches the fuel/air mixture,


Because warm air is less dense than cold air.


When the air density decreases (because the air
is warm), the fuel/air mixture (ratio) becomes
richer since there is less air for the same amount
of fuel.


Applying carburetor heat decreases engine
output and increases operating temperature.

Fuel Air Mixture


At higher altitudes, the fuel/air mixture must be leaned to
decrease the fuel flow in order to compensate for the
decreased air density, i.e., to keep the fuel/air mixture
constant.


If you descend from high altitudes to lower altitudes
without enriching the mixture, the mixture will become
leaner because the air is denser at lower altitudes.


If you are running up your engine at a high
-
altitude
airport, you may eliminate engine roughness by leaning
the mixture,


Particularly if the engine runs even worse with carburetor
heat, since warm air further enriches the mixture.


Fuel Air Mixture

4 Stroke Principles

Abnormal Combustion


Detonation occurs when the fuel/air mixture explodes
instead of burning evenly.


Detonation is usually caused by using a lower
-
than
-
specified grade (octane) of aviation fuel or by excessive
engine temperature.


This causes many engine problems including excessive
wear and higher than normal operating temperatures.


Lower the nose slightly if you suspect that an engine
(with a fixed
-
pitch propeller) is detonating during
climbout after takeoff. This will increase cooling and
decrease the engine's workload.


Pre
-
ignition is the uncontrolled firing of the fuel/air
charge in advance of the normal spark ignition.

Aviation Fuel Practices


Use of the next
-
higher
-
than
-
specified (octane) grade of fuel is
better than using the next
-
lower
-
than
-
specified grade of fuel. This
will prevent the possibility of
detonation, or running the engine
too hot.



Filling the fuel tanks at the end of
the day prevents moisture
condensation by eliminating the
airspace in the tanks.



In an airplane equipped with fuel
pumps, the auxiliary electric fuel
pump is used in the event the
engine
-
driven fuel pump fails.

Fuel Systems

Fuel Injection

Types of Fuel Systems


1.
Gravity feed

2.
Pump driven

3.
Injected

Engine starting


After the engine starts, the throttle should be
adjusted for proper RPM and the engine
gauges, especially the oil pressure, checked.




When starting an airplane engine by hand, it is
extremely important that a competent pilot be at
the controls in the cockpit.


(hand propping not allowed at WVFC)




Refer to your aircrafts POH for proper starting
and operating techniques and concerns.

The End

Chris Tavenner

Tractor King Aviation Services

www.tractorking.org