Weather & Aeronautical Decision Making
Weather kills more pilots than mechanical failure. ADM is the mental discipline that keeps you out of those statistics.
Reading a METAR
Meteorological Aerodrome Report — issued hourly, gives current conditions at a specific airport.
METAR KAUS 121753Z 18012KT 10SM FEW045 BKN080 28/14 A2992 RMK AO2
- KAUS: Station identifier (Austin-Bergstrom)
- 121753Z: Day 12, time 1753 Zulu
- 18012KT: Wind 180° at 12 knots
- 10SM: Visibility 10 statute miles
- FEW045: Few clouds at 4,500 AGL (ceiling begins at BKN or OVC)
- BKN080: Broken clouds at 8,000 AGL — this is the ceiling
- 28/14: Temp 28°C / Dewpoint 14°C
- A2992: Altimeter setting 29.92 inHg
Reading a TAF
Terminal Aerodrome Forecast — issued 4x daily, covers a 24–30 hour period for airports with instrument approaches.
- Format is similar to METAR but includes time groups showing when conditions change
- FM: From — permanent change at the specified time
- TEMPO: Temporary — conditions last less than 1 hour at a time
- BECMG: Becoming — gradual change over a 2-hour window
- PROB30/40: 30% or 40% probability of the following conditions
Live products: read current METAR/TAF and the Graphical Forecast for Aviation (GFA) at the NWS Aviation Weather Center. The GFA is the modern replacement for the legacy textual Area Forecast — synopsis, clouds, weather, icing, turbulence, and winds aloft on time-stepped map layers from now to 15 hours out. It belongs in every pre-flight briefing.
Density Altitude
Pressure altitude corrected for non-standard temperature. High density altitude = less air = reduced engine and rotor performance.
- Formula: DA = PA + (120 × (OAT - ISA temp))
- ISA standard: 15°C at sea level, decreasing 2°C per 1,000 ft
- Hot + High + Humid = Horrible performance
- Always check performance charts before flying from high-elevation airports or on hot days
- Never assume you can hover OGE just because you did it last week — density altitude changes daily
Types of Fog
Fog is a cloud at the surface — visibility under 5/8 SM. Mist is the same but with visibility above that threshold. All forms of fog can ground a VFR helicopter pilot for hours or days.
- Radiation fog: Forms on clear, calm nights as the ground cools and chills the air directly above it. Common in valleys after sunset. Usually burns off within hours of sunrise.
- Advection fog: Forms when moist air moves over colder ground or water. Common along coastlines. Deepens with wind up to ~15 kts; stronger winds lift it into stratus. Can persist for days.
- Upslope fog: Moist, stable air forced up sloping terrain. Requires wind to form and persist. Will not burn off with sun alone — can last for days like advection fog.
- Steam fog (sea smoke): Cold dry air over warm water. Water evaporates, rises, and resembles smoke. Common over lakes/oceans in winter. Often comes with low-level turbulence and icing.
- Ice fog: Forms in extreme cold (-25°F or colder) when water vapor sublimates directly into ice crystals. Mostly an Arctic phenomenon.
Temperature inversion: Normally air cools with altitude (adiabatic cooling as it rises and expands). In an inversion, temperature increases with altitude. The warm cap traps moisture, smoke, and pollutants below — visibility deteriorates rapidly. Common after clear, calm nights.
TFRs & NOTAMs
- Check tfr.faa.gov or 1800wxbrief for active TFRs before every flight
- Stadium TFRs activate 1 hour before and extend 1 hour after major sporting events (3 NM radius, surface to 3,000 AGL)
- Presidential TFRs have zero tolerance — entering one unannounced will result in an intercept
- Check NOTAMs for airspace changes, closed runways, tower cranes, and outages affecting navigation
Aeronautical Decision Making (ADM)
The structured approach to making safe decisions in aviation. The FAA defines ADM as a systematic approach to the mental process used by aircraft pilots to consistently determine the best course of action.
- DECIDE Model: Detect, Estimate, Choose, Identify, Do, Evaluate
- IMSAFE Checklist: Illness, Medication, Stress, Alcohol, Fatigue, Emotion — check yourself before every flight
- PAVE Checklist: Pilot, Aircraft, enVironment, External pressures
- Recognize hazardous attitudes: Anti-authority, Impulsivity, Invulnerability, Macho, Resignation
Go/No-Go Decision Making
The hardest skill in aviation. Pressure to fly — from passengers, schedule, cost — kills pilots.
- Establish personal minimums before the flight, not during it
- If the weather is below your minimums at departure, it will be below them en route too
- The helicopter will still be there tomorrow. You might not be.
- The only time you need to make it is when you have to — define "have to" very strictly
- Continuing VFR into IMC is the leading cause of fatal general aviation accidents