Weather And Airfoil Flashcards
METAR
Meteorological Aviation Report - Testable (hourly updates, observation portion on the JET)
Zulu time is 6 hours further from Alabama time - must be converted
Winds based on true north, runways based on magnetic north
We ONLY use centigrade/celsius readings
A3004 = 30.04Hg altimeter setting
AO1 - Automated weather station (no precip discriminator)
AO2 - Automated weather station with precipitation discriminator
AO2A - Automated weather station with precipitation discriminator and a human input
SLP174 = Sea Level Pressure to be converted to Hg Mercury
TAF - Terminal Aerodrome Forecast - reports within 5 miles of location
Ex) QNH2992INS = lowest reported altimeter height
C-63 flight pub - SM meters reading to statute miles; 9999m = 7SM - Infinity miles
TX25/1219z TN05/1311z = max and min temperatures from 12 1900z to 13 1100z
JET
Joint Environmental Toolkit
The weather report with the observation in the lower left corner
Two components of an RVR report
Runway visual range in:
- “Hundreds of feet”
- Effective runway
3 components of atmospheric density
Temperature, pressure, humidity
What is associated with a cumulonimbus cloud?
Thunderstorms
Flight control surfaces
Anti-torque pedals: correct for nose yaw, assist in flight trim
Cyclic: provides directional control of aircraft, produces a thrust the direction the disk is pointed
Collective: provides vertical control (ie. changes pitch collectively to all blades)
Vectors
All forces are vectors (tug boat image)
4 quadrants of lifting forces (FL, FR, RL, RR)
Newtons Laws of Motion
**Four forces of flight: “lift opposes weight, thrust opposes drag”
1) A body at rest will remain at rest and a body in motion will remain in motion unless a force acts upon them (lower torque in fixed velocity flight than acceleration)
2) An acceleration is a change in velocity with respect to time (pitch forward)
3) For every action there is an equal and opposite reaction (tail rotor thrust)
An example of inertia (level flight)
An example of acceleration (upward win of traffic pattern)
An example action/reaction (takeoff to a hover)
Bernoulli’s principal
Within a “confined” system, total energy remains the same
Constriction causes faster speed, dynamic pressure increases and static pressure decreases and total pressure is unchanged
Airfoil
An airfoil is a surface/body/structure that produces a LIFT or THRUST.
Top of airfoil - dynamic pressure increases, static pressure decreases, total pressure unchanged
Bottom of airfoil - dynamic pressure reduces, static pressure increases, total pressure unchanged.
*High STATIC pressure seeks lower pressure - lift is produced by underside of airfoil air static pressure seeking the low static pressure above the airfoil
**with an INCREASE in air speed above an airfoil, it’s dynamic pressure increases”
Chordline
Line protruding from leading edge to trailing edge, where all winds and angles of forces are measured
Chord
Distance from blade leading edge to trailing edge, PROVIDES longitudinal dimension of an airfoil (Self contained within airfoil)
Airfoil sections
Camber - the shape or curvature of an airfoil, expressed as upper or lower camber
Upper chamber - top side of airfoil
Lower chamber - lower side of airfoil
Span
Length of a rotor blade from point of rotation (root) to blade tip
CENTER OF PRESSURE
Where all aerodynamic forces act on an airfoil (most critical part of an airfoil!!!)
Center of pressure is considered constant/fixed (immovable) on a symmetrical airfoil, and considered to be moveable in a non/un-symmetrical system
**Not called “asymmetrical”
What is the difference between the symmetrical and un-symmetrical blades? - their different
Rotors
The blade advances into a relative wind (from 6 o’clock to 3o’clock) - flaps up due to relative velocity increase [right side advancing side]
Blade “retreats from a relative wind” (from 12o’clock to 9o’clock) and blade flaps down to to relative wind decrease [left side retreating side]
Types of relative wind
Rotational relative wind as seen by a rotor blade is the relative wind coming towards the rotor blade is it rotates.
Relative wind on the advancing side is ALWAYS faster than the retreating side.
Rotor tip velocity is 394 knots. Rotor rotates at 394 rpm as well (coincidence?). Use 400 knots for exam
Induced flow
The component of air flowing vertically through the rotor system
Final wind
Final wind is the RESULTANT RELATIVE WIND: the rotational relative wind that is MODIFIED by induced flow.
Induced flow in forward flight
The only way to reduce the effects of INDUCED FLOW is through FORWARD AIRSPEED
Angle of incidence
Measured BETWEEN the CHORD-LINE and the ROTATIONAL RELATIVE WIND
Angle of Incidence (AOI) is a MECHANICAL angle
Angle of attack
Measured from the CHORD-LINE to the RESULTANT RELATIVE WIND. This is the AERODYNAMIC angle
What is the cause of all general aviation stalls?
*Exceeding the critical angle of attack
Induced flow with respect to angle of attack
When induced flow is increase, the angle of attack decreases
This is why at hover, we dont “fly” well. Only forward speed will increase our angle of attack here
Airspeed indicator
Diaphragm is vented to the pitot tube
Case is vented to the static port/pressure
Pressures used IN a pitot static system
Static (static ports
Impact = dynamic (all for airspeed indicator) Ram = dynamic Pitot = dynamic Total = dynamic
True altitude
Altitude above mean sea level (MSL)
Pressure altitude
Measured above the standard datum plane
Indicated altitude
Uses current altimeter setting to indicate pressure altitude
