1st Test for Flight Academics Flashcards
The METAR is a report that is issued ___.
hourly
What kind of report is made anytime there is a significant change in the weather (other than hourly) at the observation station?
Special Report (SPECI)
METAR KOZR 100955z would indicate an hourly report for what time on the current date?
1000z
The wind direction is given in degrees from ___ north and wind speed is always in ___.
- true
- knots
What is atmospheric pressure?
The force exerted by the weight of a column of air
What is the standard sea level pressure in inches of mercury?
29.92” Hg
What is the standard sea level temperature in degrees Celsius?
15 degrees C
What is the standard temperature lapse rate with altitude?
2 degrees C for every 1,000 ft. of altitude
A change in 1 inch of mercury pressure is equal to approximately ___ feet of altitude.
1,000 ft.
Define impact pressure.
Static pressure plus dynamic pressure
Define static pressure.
- Ambient atmospheric pressure
- Static pressure is also known as Ram, Total, or Pitot pressure
Which instruments depend on static pressure only?
- Altimeter
- Vertical Speed Indicator
Which instrument depends on both impact (dynamic) and static pressure?
Airspeed indicator
What pressures affect the pitot static system?
Dynamic and Static pressure
Name and define the three types of airspeed.
– Indicated - read from the dial on the face of the instrument.
– Calibrated - IAS corrected for instrument and position error.
– True - CAS corrected for density error.
Name and explain the three errors in the airspeed indicator.
– Installation Error - misalignment of the Pitot tube with the relative wind and position of the static vents.
– Density Error - caused by pressure and temperature changes, air less dense as altitude increases.
– Instrument Error - caused by friction in the instrument
Is the instantaneous vertical speed indicator (IVSI) a pressure differential measuring instrument?
Yes
What does the setting knob on the altimeter change when it is tuned?
Kollsman setting and position of the needles
A change of .15 inch of mercury pressure is equal to ___ feet.
150
Define indicated altitude.
Altitude as read on the dial with a current altimeter setting
Define true altitude.
Altitude above MSL
Define pressure altitude.
Altitude above the standard datum plane (29.92” Hg)
Define absolute altitude.
Altitude above the terrain (AGL)
Define altimeter setting.
Station pressure corrected to MSL
Why is an altimeter setting necessary?
To correct for pressure changes
What is the maximum allowable error in the altimeter?
+/- 75 feet (FAA), aviators should check operator or maintenance manual to confirm accurate limit for their aircraft.
When flying into an area of lower pressure without resetting the altimeter, would your true altitude be higher or lower than your indicated altitude?
Lower
When flying into an area of higher pressure without resetting the altimeter, would your true altitude be higher or lower than your indicated altitude?
Higher
If you depart a base with an altimeter setting of 29.82 and an hour later receive a new altimeter setting of 30.22, how much higher or lower than indicated altitude would true altitude be prior to adjusting the altimeter to the new setting?
400 feet higher than indicated altitude
At the last reporting point, you corrected the altimeter by setting the Kollsman scale on 29.92” Hg. Prior to landing, you received a new setting of 29.80. What is your true altitude in relation to indicated altitude (before you reset the altimeter)?
120 feet lower than indicated altitude
When flying into an area of colder than standard temperature, would the indicated altitude be higher or lower than true altitude?
Higher
The ___ stops function properly due to pitot icing.
Airspeed indicator
What is the recommended corrective action when the static system is clogged?
Switch to an alternate source
TRUE or FALSE. High DA and low air density mean nearly the same thing.
TRUE
What causes density error?
Nonstandard pressure and temperature (atmospheric conditions)
Define true airspeed.
Calibrated airspeed (CAS) corrected for density error.
Listed below are examples of Newton’s Laws of Motion. Indicate which law is involved in each.
1. Torque effect - ___
2. More power is needed to obtain a desired RPM than is needed to maintain the RPM - ___
3. Greater load, less acceleration - ___
- Action / Reaction
- Inertia
- Acceleration
If the airflow atop the airfoil increases, static pressure will ___ and dynamic pressure will ___.
- decrease
- increase
Define center of pressure.
The point along the chord line of an airfoil through which all aerodynamic forces are considered to act.
Define airfoil.
Any surface designed to produce lift when air is passed over it
List the two basic types of airfoils.
- Symmetrical
- Nonsymmetrical
Six descriptions of airfoil (blade) sections are listed. Give the airfoils terms that match the descriptions.
1. Rounded edge - ___
2. Straight line from the leading edge to the trailing edge - ___
3. Upper curvature - ___
4. Lower shape - ___
5. The length of the rotor blade from the point of rotation to the tip of the blade - ___
6. Tapered edge - ___
- Leading edge
- Chord
- Upper camber
- Lower camber
- Span
- Trailing edge
Define rotational relative wind as applied to an airfoil.
The flow of air parallel and opposite to the flight path of a rotating airfoil produced by the rotor blades turning about the mast.
Define induced flow.
Downward flow of air through the rotor blades
Define resultant relative wind.
Rotational relative wind modified by induced flow
How is the angle of incidence measured in a rotary-wing aircraft?
The angle between the chord of an airfoil and the plane of rotation (tip path plane)
Define angle of attack.
The angle between the chord of an airfoil and the resultant relative wind
Which flight control changes the angle of incidence differentially around the rotor system?
Cyclic pitch control
With an increase in the speed of air over a surface, what happens to dynamic and static pressure?
dynamic pressure increases, static pressure decreases
List the two components of total aerodynamic force.
Lift and Drag
Describe the relationship of lift to resultant relative wind.
It is perpendicular to resultant relative wind
Describe the relationship between drag and resultant relative wind.
Drag is parallel to and in the same direction of the resultant relative wind.
Indicate whether the drag is induced, parasitic, or profile:
1. Rotor-tip vortices - ___
2. Lift and total aerodynamic force tilting rearward on the airfoil - ___
3. Skin friction on the fuselage - ___
4. Skin friction on the airfoil - ___
5. Non-streamlined fuselage - ___
- Induced
- Induced
- Parasitic
- Profile
- Parasitic
Which type of drag decreases with an increase in airspeed?
Induced
Which type of drag increases with an increase in airspeed?
Parasitic
Define dissymmetry of lift.
Unequal lift between advancing and retreating halves of the rotor disk.
Relative wind velocity on the advancing blade equals blade speed ___ airspeed.
Plus
Relative wind velocity on the retreating blade equals blade speed ___ airspeed.
Minus
What causes the advancing blade to flap up?
An increase in lift
What causes the retreating blade to flap down?
A decrease in lift
How does the helicopter compensate for dissymmetry of lift?
Flapping
How does the pilot control dissymmetry of lift?
Cyclic Feathering
Define blowback.
Change in the attitude of the rotor system
How does the pilot correct for blowback?
Cyclic Feathering
Which forces in the lift equation can the pilot control?
The Coefficient of Lift (CL) (through AOA) and the relative wind velocity (or airspeed V2).
What are the three factors in air density (1/2 rho) that will affect lift?
- Pressure
- Temperature
- Humidity
A semi-rigid disk tilts relative to the ___.
Mast
An articulated disk tilts relative to the ___.
Hub
Define centrifugal force.
Outward force produced whenever a body moves in a curved path
Define rotor blade coning.
Upward flexing of the rotor blades
Rotor blade coning is a compromise between which two forces?
Lift and centrifugal force
Define gyroscopic precession.
When a force is applied to a rotating body, it will manifest 90 degrees after application in the direction of rotation.
Why is blade twisting necessary?
To distribute the lifting force more evenly along the blade
A pedal turn to the right requires ___ power than a pedal turn to the left.
Less
Define translating tendency.
Tendency of a single rotor helicopter to drift right while hovering.
List four methods used to overcome translating tendency in single rotor helicopters:____________
- Rigging the cyclic
- Tilting the mast
- Left cyclic
- Automatic flight-control/stabilization augmentation system
