Atmospheric Pressure, Humidity and Frontal Systems

• Atmospheric circulation relies on unequal heating from the sun
• Every weather process involves or results from heat exchange

Atmospheric Pressure

• Atmospheric pressure decreases with elevation
• It decreases 1 inch of mercury per 1,000 feet of elevation gain
• Temperature decreases about 2 degrees Celsius (3.5 degrees Fahrenheit) per 1,000 feet increase in elevation

Humidity and Dew Point

• A small or converging temperature/dewpoint spread can lead to fog and low clouds

Moisture in the Air

• Unsaturated air has a relative humidity below 100%
• Saturated air has a relative humidity at 100%

Processes Adding Moisture to Unsaturated Air:

• Evaporation: liquid to water vapor
• Sublimation: ice to water vapor

Frontal Systems

• Pressure typically falls as a front approaches and rises after it passes
• Winds shift to the right after a frontal passage

Thunderstorm Formation

• Avoid thunderstorms by at least 20 nautical miles
• Three conditions must exist:
  • Unstable air (warmer air parcels)
  • Lifting action (fronts, terrain, solar heating)
  • High moisture levels
• LIM: Lift, Instability, Moisture
• Thunderstorms and squall lines often form ahead of fast-moving cold fronts.

Thunderstorm Types

• Single Cell: Lasts less than 1 hour
• Multi Cell: Cluster of storms in different development stages
• Squall Line: Forms 50-100 miles ahead of fast-moving cold front

Wind Shear

• Wind shear is a change in wind speed or direction over a short distance
• Microbursts are dangerous downdrafts linked to convective activity

Icing Conditions

• Pilots cannot fly into known icing without anti-icing/deicing equipment, according to regulations

Flight Review (FAR 61.56 and 61.57)

• A pilot must receive a flight review within the preceding 24 calendar months to act as PIC
• To carry passengers during the DAY, the pilot must have completed 3 takeoffs and landings in the same category and class of aircraft within the preceding 90 days
• To carry passengers at NIGHT (1 hour after sunset and 1 hour before sunrise), the pilot must have completed 3 takeoffs and landings to a full stop during night hours within the preceding 90 days

Aircraft Category and Class

• Example: Category - Airplane, Class - Single Engine Land (SEL)

Night Definition (FAR 1.1)

• Night is the time between the end of evening civil twilight and the beginning of morning civil twilight

Aircraft Lighting (FAR 91.209)

• Position and anti-collision lights must be on from sunset to sunrise

Intoxicated or Drugged Passengers (FAR 91.17)

• Pilots cannot allow intoxicated or drugged persons on board except in emergencies

Preflight Action (FAR 91.103)

• The Pilot in Command (PIC) must be familiar with all available information before the flight.

NWKRAFT (Preflight Information)

• NOTAMS
• Weather
• Known ATC delays
• Runway lengths
• Alternates
• Fuel requirements
• Takeoff/landing distances

Required Aircraft Documents (FAR 91.203, ARROW)

• A - Airworthiness Certificate
• R - Registration Certificate (must not be expired)
• R - Restricted Radiotelephone Operator's Permit (only required for international flights)
• O - Operating Limitations (found in POH)
• W - Weight and Balance information

Aerobatic Flight Restrictions (FAR 91.303)

• Over congested areas
• Over open-air assemblies of people
• Within Class B, C, D, or E airspace
• Within 4 NM of a Federal airway centerline
• Below 1,500 feet above the surface
• When flight visibility is less than 3 statute miles

Required Day VFR Equipment (FAR 91.205, "A TOMATO FLAMES")

• A - Airspeed Indicator
• T - Tachometer (each engine)
• O - Oil Pressure Gauge (each engine)
• M - Manifold Pressure Gauge (altitude engines)
• A - Altimeter
• T - Temperature Gauge (liquid-cooled engines)
• O - Oil Temperature Gauge (air-cooled engines)
• F - Fuel Gauge (each tank)
• L - Landing Gear Position Indicator (if applicable)
• A - Anti-Collision Lights (red/white)
• M - Magnetic Compass (with deviation card)
• E - Emergency Locator Transmitter (ELT)
• S - Safety Belts (for all passengers > 2 years old)

Required Night VFR Equipment (FAR 91.205, "A TOMATO FLAMES + FLAPS")

• F - Fuses (spare set)
• L - Landing Light
• A - Anti-Collision Lights
• P - Position Lights
• S - Source of Electrical Power (battery or alternator)
• Plus Day VFR Equipment "A TOMATO FLAMES"

Passenger Briefing (FAR 91.107)

• PIC must brief passengers on how to fasten/unfasten seatbelts and shoulder harnesses

PIC Authority and Responsibility (FAR 91.3)

• PIC has final authority over the flight and aircraft
• PIC may deviate from FARs in an emergency

ATC Instructions and Clearances (FAR 91.123)

• Pilots cannot deviate from ATC clearances without an amended clearance or an emergency
• If an ATC clearance violates an FAR, disregard it and notify ATC

NTSB Part 830: Reporting Aircraft Accidents and Incidents

• Accident: death or serious injury, or substantial damage to the aircraft
• Incident: any occurrence affecting or potentially affecting safety of operations

NTSB Notification Requirements

• Flight control system malfunction or failure
• In-flight fire
• Aircraft collision in flight
• Damage > $25,000 to property other than the aircraft
• Release of a propeller blade (except from a ground strike)

METAR (Meteorological Aerodrome Report)

• Also known as Aviation Routine Weather Report
• Observation, not a forecast
• Valid within 5 NM of an airport
• Issued hourly, valid for 1 hour, or until the next METAR
• Special METAR (SPECI) issued when significant weather changes occur
• Use AWC METAR/TAF websites

Reading a METAR

• Sequence: station identifier, date/time, wind, visibility, precipitation, cloud cover, temperature/dewpoint, altimeter setting, remarks

Surface Analysis Chart

• Displays location of fronts and pressure systems
• U.S. low-level significant weather prog chart is valid up to 24,000 feet.

Flight Service Station (FSS)

• Frequency 122.2
• Primary source for preflight weather information
• Call 1-800-WX-BRIEF or go to 1800wxbrief.com to file VFR or IFR flight plans and obtain weather briefings

Types of Weather Briefings

• Outlook Briefings are for departures 6 or more hours away

Data Link Weather

• Often included with GPS and EFB cockpit or tablet display systems

Explores how the atmospheric circulation relies on unequal heating from the sun. Also describes atmospheric pressure, humidity, dew point, frontal systems, and thunderstorm formation. It provides essential insights into weather processes and safety measures.