PTS Area of Operation II: Technical Subject Areas- A Flashcards
Airspeed Indicator
differential pressure gauge that
measures and promptly indicates the difference between pitot
(impact/dynamic pressure) and static pressure. When the aircraft moves through the air, the
pressure on the pitot line becomes greater than the pressure
in the static lines. This difference in pressure is registered by
the airspeed pointer on the face of the instrument,
ASI uses both
pitot tube and static system. ASI introduces the static
pressure into the airspeed case while the pitot pressure
(dynamic) is introduced into the diaphragm. The dynamic
pressure expands or contracts one side of the diaphragm,
which is attached to an indicating system. The system drives
the mechanical linkage and the airspeed needle.
Pitot Tube
Ram Air- Impact air forced into the pitot tube by the relative wind which exerts pressure
Types of airspeed
Indicated Calibrated true Groundspeed
Indicated airspeed
the direct instrument
reading obtained from the ASI, uncorrected for
variations in atmospheric density, installation error,
or instrument error. Manufacturers use this airspeed
as the basis for determining aircraft performance.
Takeoff, landing, and stall speeds listed in the AFM/
POH are IAS and do not normally vary with altitude
or temperature.
Calibrated airspeed
IAS corrected for installation error and instrument error. Although manufacturers attempt to keep airspeed errors to a minimum, it is not possible to eliminate all errors throughout the airspeed operating range. At certain airspeeds and with certain flap settings, the installation and instrument errors may total several knots. This error is generally greatest at low airspeeds and nose high attitudes. In the cruising and higher airspeed ranges, IAS and CAS
are approximately the same. Refer to the airspeed calibration chart to correct for possible airspeed errors
True airspeed
corrected for altitude and nonstandard temperature. Because air density decreases with an increase in altitude, an aircraft has to be flown faster at higher altitudes to cause the same
pressure difference between pitot impact pressure and static pressure. Therefore, for a given CAS, TAS
increases as altitude increases; or for a given TAS, CAS decreases as altitude increases. A pilot can find TAS by two methods. The most accurate method is
to use a flight computer. With this method, the CAS is corrected for temperature and pressure variation by
using the airspeed correction scale on the computer. Extremely accurate electronic flight computers are
also available. Just enter the CAS, pressure altitude, and temperature, and the computer calculates the TAS.
A second method, which is a rule of thumb, provides the approximate TAS. Simply add 2 percent to the
CAS for each 1,000 feet of altitude. The TAS is the speed that is used for flight planning and is used when
filing a flight plan.
Groundspeed
actual speed over the ground
ASI color coding
Aircraft weighing 12,500 pounds or less, manufactured after
1945, and certificated by the FAA are required to have ASIs
marked in accordance with a standard color-coded marking
system
White arc
commonly referred to as the flap operating range since its lower limit represents the full flap stall speed and its upper limit provides the maximum flap speed. Approaches and landings are usually flown at speeds within the white arc
Lower limit of white arc
Lower limit of white arc (VS0)—the stalling speed
or the minimum steady flight speed in the landing
configuration. In small aircraft, this is the power-off
stall speed at the maximum landing weight in the
landing configuration (gear and flaps down).
Upper limit of white arc
Upper limit of the white arc (VFE)—the maximum
speed with the flaps extended.
Green arc
the normal operating range of the aircraft.
Most flying occurs within this range.
Lower limit of green arc
Lower limit of green arc (VS1)—the stalling speed
or the minimum steady flight speed obtained in a
specified configuration. For most aircraft, this is the
power-off stall speed at the maximum takeoff weight
in the clean configuration (gear up, if retractable, and
flaps up).
Upper limit of the green arc
Upper limit of green arc (VN0)—the maximum structural cruising speed. Do not exceed this speed except in smooth air.
Yellow arc
Yellow arc—caution range. Fly within this range only in smooth air and then only with caution.
Red Line
never exceed speed. Operating above
this speed is prohibited since it may result in damage or structural failure
S model V speeds
Vso 40
Vs 48
Vbg 68
Vx 62
Vy 74
Vfe flaps 10 110
Vfe flaps 20 30 85
Va Max 105
Vno 129
Vne 163
ASI Instruments check
Prior to takeoff, the ASI should read zero. However, if there
is a strong wind blowing directly into the pitot tube, the ASI
may read higher than zero. When beginning the takeoff,
make sure the airspeed is increasing at an appropriate rate.
Altimeter
The altimeter is an instrument that measures the height of
an aircraft above a given pressure level
altimeter works by
A stack of sealed aneroid wafers comprise the main
component of the altimeter. An aneroid wafer is a sealed wafer that is evacuated to an internal pressure of 29.92 inches of mercury (“Hg). These wafers are free to expand and contract with changes to the static pressure. A higher static pressure presses down on the wafers and causes them
to collapse. A lower static pressure (less than 29.92 “Hg)
allows the wafers to expand. A mechanical linkage connects
the wafer movement to the needles on the indicator face, which translates compression of the wafers into a decrease in altitude and translates an expansion of the wafers into an
increase in altitude
kollsman window
barometric pressure window is sometimes referred to as
the Kollsman window
GOING FROM A HIGH TO A LOW, LOOK OUT BELOW.”
For example, if an aircraft is
flown from a high pressure area to a low pressure area without adjusting the altimeter, a constant altitude will be displayed, but the actual heigh of the aircraft above the ground would
be lower then the indicated altitude. :
FROM HOT TO COLD, LOOK OUT
BELOW
Since cold air is denser than warm air, when operating in temperatures
that are colder than standard, the altitude is lower than the altimeter indication
Not changing altimeter setting example
The importance of properly setting the altimeter cannot
be overemphasized. Assume the pilot did not adjust the
altimeter at Abilene to the current setting and continued using
the Mineral Wells setting of 29.94 “Hg. When entering the
Abilene traffic pattern at an indicated altitude of 2,600 feet,
the aircraft would be approximately 250 feet below the proper
traffic pattern altitude. Upon landing, the altimeter would
indicate approximately 250 feet higher than the field elevation.
Not changing altimeter setting example
The following is another method of computing the altitude
deviation. Start by subtracting the current altimeter setting
from 29.94 “Hg. Always remember to place the original setting
as the top number. Then subtract the current altimeter setting.
Mineral Wells altimeter setting 29.94
Abilene altimeter setting 29.69
29.94 – 29.69 = Difference 0.25
(Since 1 inch of pressure is equal to approximately 1,000 feet
of altitude, 0.25 × 1,000 feet = 250 feet.) Always subtract
the number from the indicated altitude.
2,600 – 250 = 2,350
Now, try a lower pressure setting. Adjust from altimeter
setting 29.94 to 30.56 “Hg.
Mineral Wells altimeter setting 29.94
Altimeter setting 30.56
29.94 – 30.56 = Difference –0.62
(Since 1 inch of pressure is equal to approximately 1,000 feet
of altitude, 0.62 × 1,000 feet = 620 feet.) Always subtract
the number from the indicated altitude.
2,600 – (–620) = 3,220
The pilot will be 620 feet high.
Indicated altitude
read directly from the altimeter
(uncorrected) when it is set to the current altimeter
setting
True altitude
—the vertical distance of the aircraft
above sea level—the actual altitude. It is often expressed as feet above mean sea level (MSL). Airport, terrain, and obstacle elevations on aeronautical charts are true altitudes
Absolute altitude
the vertical distance of an aircraft
above the terrain, or above ground level (AGL).
Pressure altitude
the altitude indicated when
the altimeter setting window (barometric scale) is
adjusted to 29.92 “Hg. This is the altitude above the standard datum plane, which is a theoretical
plane where air pressure (corrected to 15 °C) equals 29.92 “Hg. Pressure altitude is used to compute density
altitude, true altitude, true airspeed (TAS), and other performance data.
Density altitude
pressure altitude corrected
for variations from standard temperature. When
conditions are standard, pressure altitude and density
altitude are the same. If the temperature is above standard, the density altitude is higher than pressure altitude. If the temperature is below standard, the density altitude is lower than pressure altitude. This is an important altitude because it is directly related to the aircraft’s performance.
Altimeter instrument check
set pressure altitude if off elevation more than 75 feet cant use
VSI displays what
- Trend information shows an immediate indication of an increase or decrease in the aircraft’s rate of climb or descent.
- Rate information shows a stabilized rate of change in altitude
VSI operation
static pressure decreases, and as it decreases immediately in the diaphragm. But the instrument casing is a different story. Since the calibrated leak lets air out slowly, it creates a higher pressure in the casing than the diaphragm. When that happens, it creates a pressure differential, the diaphragm is squeezed down, and the gears connected to the VSI needle make it move up or down
When you initially start climbing or descending, your VSI needle will start moving, but it can’t immediately indicate how fast you’re climbing. This is what’s called trend information. When you see the directing of the needle moving up, you know your climb rate is increasing, and when it moves down, you know your climb rate is decreasing. You just don’t know how much
After a second or two, the calibrated leak has a chance to catch up and reach equilibrium, and your VSI will stabilize at a certain climb or descent rate. When that happens, you have rate information.
VSI Instrument check
VSI must be established. Make sure the VSI indicates a near zero
reading prior to leaving the ramp area and again just before
takeoff. If the VSI indicates anything other than zero, that
indication can be referenced as the zero mark.
Blocked Pitot tube
ASI- zero
Altimeter- works
VSI- works
Blocked Pitot tube and Drain Hole. Open static
ASI- High climb, Low descent
Altimeter-works
VSI- works
Blocked Static, Open pitot
ASI- Low Climb, High descent
Altimeter- Frozen
VSI- Frozen
Using alternate static air
ASI- reads high
Altimeter- reads high
VSI- momentarily shows climb
Broken VSI Glass
ASI- reads high
Altimeter- reads high
VSI-reverses
Precession
Precession is the tilting or turning of a gyro in response to a
deflective force. The reaction to this force does not occur at
the point at which it was applied; rather, it occurs at a point
that is 90° later in the direction of rotation. This principle
allows the gyro to determine a rate of turn by sensing the
amount of pressure created by a change in direction. The rate
at which the gyro precesses is inversely proportional to the
speed of the rotor and proportional to the deflective force
Attitude indicator
shows pitch and bank. the gyro in the attitude indicator is mounted in a horizontal plane, and depends upon rigidity in space for its operation. The horizon bar is fixed to the gyro and remains in a horizontal plane as the aircraft is pitched or banked about its lateral or longitudinal axis, indicating the attitude of the aircraft relative to the true horizon. The gyro spins in the horizontal plane and resists deflection
of the rotational path. Since the gyro relies on rigidity in space, the aircraft actually rotates around the spinning gyro.
Rigidity in Space
a gyroscope remains in a fixed position in the plane in which it is spinning.
An example of rigidity in space is that of a bicycle wheel. As the bicycle wheels increase speed, they become more stable in their plane of rotation. This is why a bicycle is unstable and
maneuverable at low speeds and stable and less maneuverable
at higher speeds. By mounting this wheel, or gyroscope, on a set of gimbal
rings, the gyro is able to rotate freely in any direction. Thus, if the gimbal rings are tilted, twisted, or otherwise moved,
the gyro remains in the plane in which it was originally spinning.
Gyros powered by
Vacuums or electronic
Attitude instrument Check
up and erect after 5 minutes within 5 degrees
attitude indicator error
Cannot pitch more than 70 degrees and bank 110 degrees would cause tumbling.
Heading indicator
shows changes in heading but cant measure heading, must set it based on mag compass. operates on riggity in space and has a vertically mounted gyro so only the horizontal axis is used to drive the display. Airplane spins around the gyro itself, when the aircraft turns the gyro and main drive gear stays in place and the. the main drive gear spins in the horizontal axis and then drives the compass card gear to indicated heading change.
Heading indicator error
precession or friction, must re align
Turn indicators
turn coordinator and turn and slip indicator
Turn coordinator
electric. used while banking. shows rate and quality of turn. shows straight and level and standard rate turns. also has inclinometer, shows slips or skids. gyro rotates vertivcally from a motor in the center angled at 30 degrees so it can remain upright in a turn
slip
needs more rudder, ball inside the turn
skid
needs less rudder, ball outside the turn
S model electrical system
28 volt DC system
Alternator with 60 amps
24 volt battery
4 volt discrepancy To charge the battery
Standby battery
Standby battery test for 10 seconds to make sure the green light stays on and shows a trend of constant power. Located between the firewall and instrument panel. Power essential bus if alternator and main battery fail. ARM-OFF-TEST. IF not armed does not charge and cannot be used if failures occur.
Standby battery annunciation shows -.5 volts are being drawn for more than 10 seconds