Helicopter Pilot Review Notes

Flashcards covering essential aviation weather, airspace, flight operations, and human factors for helicopter pilots.

Stable Air

Cool, dry air that is colder than its surroundings, causing it to sink and condense. It spins clockwise.

Unstable Air

Warm, moist air that is warmer than its surroundings, causing it to rise and expand. It spins counter-clockwise.

Standard Pressure

29.92 inches of Mercury (Hg) at Sea Level, equivalent to 1013.2 Millibars. Unequal heating of the earth’s surface causes changes in pressure.

Standard Temperature

15°C at Sea Level.

Standard Pressure Lapse Rate

1 inch of Mercury (Hg) decrease per 1,000 feet of altitude.

Lapse Rate

The rate at which temperature decreases with altitude.

Standard Lapse Rate

2°C decrease per 1,000 feet of altitude.

Dry Adiabatic Lapse Rate

3°C (5.4°F) decrease per 1,000 feet for dry air, which changes temperature faster than moist air.

High Pressure System

An area surrounded on all sides by lower pressure. Air flows clockwise, down, and out, typically leading to poor visibility, Stratus clouds, no turbulence, Rime ice, and steady precipitation.

Ridge (High Pressure)

An elongated area of high pressure.

Low Pressure System

An area surrounded on all sides by higher pressure. Air flows counter-clockwise, up, and in, typically leading to good visibility, Cumulus clouds, more severe turbulence, Clear ice, and showery precipitation.

Trough (Low Pressure)

An elongated area of low pressure.

Temperature Inversion

A layer in the atmosphere where temperature increases with altitude instead of decreasing. It traps haze, smoke, or fog, reduces visibility, and can create low-level wind shear.

Surface-based Temperature Inversion

Forms on cool, clear, calm nights when the ground cools and lowers the temperature of the air directly above it.

Frontal Temperature Inversion

Forms when cool air is forced under warm air, or warm air spreads over cooler air.

Cloud Formation

Clouds form when air is cooled to its dew point (or becomes saturated) and water vapor condenses into tiny droplets or ice crystals, often through adiabatic cooling.

High Clouds

Clouds found above approximately 20,000 feet AGL, made of ice crystals, including Cirrus, Cirrostratus, and Cirrocumulus.

Cirrus (Ci)

Wispy, hairlike high clouds formed from sublimation of ice crystals in very cold, stable air.

Cirrostratus (Cs)

Thin, sheet-like high clouds covering the sky, often producing halos around the sun or moon.

Cirrocumulus (Cc)

Small, white patches or ripples in high altitudes, often called 'mackerel sky.'

Middle Clouds

Clouds found between 6,500 and 20,000 feet AGL, often associated with frontal systems, including Altostratus and Altocumulus.

Altostratus (As)

Gray/blue-gray middle cloud layer that covers the sky, making the sun appear as if behind frosted glass.

Altocumulus (Ac)

White/gray patches of middle clouds, appearing as rolls or rounded masses.

Low Clouds

Clouds found from the surface up to 6,500 feet AGL, including Stratus, Stratocumulus, and Nimbostratus, which can bring steady rain.

Stratus (St)

A uniform gray layer of low clouds that can bring drizzle or mist, similar to fog but not on the ground.

Stratocumulus (Sc)

Low, lumpy clouds covering much of the sky.

Nimbostratus (Ns)

Thick, dark low clouds producing steady precipitation.

Clouds with Vertical Development

Clouds formed by strong convection in unstable air, such as Cumulus and Cumulonimbus, which indicate rising air.

Cumulus (Cu)

Puffy, cotton-like clouds with flat bases that indicate rising air in unstable conditions.

Cumulonimbus (Cb)

Towering thunderstorm clouds that can extend through all atmospheric levels, producing heavy rain, lightning, hail, turbulence, and wind shear.

Steam Fog (Evaporation Fog)

Forms when cold, dry air moves over warm water, causing water to evaporate and then quickly condense into fog, often seen over bodies of water in early fall/winter.

Upslope Fog

Forms when moist air is forced up an incline by wind and cools adiabatically to its dew point, requiring wind and a moist, stable air mass.

Radiation Fog

Forms overnight on clear, calm nights when the ground cools by radiating heat, cooling the air near the surface to its dew point. Common in valleys and associated with temperature inversions.

Advection Fog

Forms when warm, moist air moves horizontally over a colder surface and cools to its dew point, common near coasts with winds of 10-15 knots.

Precipitation Fog

Forms when warm rain falls through cooler air near the surface, and some evaporates, raising the dew point of the cooler air to saturation. Requires continuous precipitation and light winds.

Temperature

A measure of how hot or cold the air is; determines air density, affecting aircraft performance (warmer air = less dense = less lift).

Dew Point

The temperature at which air becomes saturated (100% relative humidity) and can no longer hold water vapor. When temperature and dew point are close (within ~3°C), fog, mist, or low clouds are likely.

Stable Air (Weather)

Air that resists vertical motion, leading to smooth air, poor visibility, stratiform clouds, and steady precipitation.

Unstable Air (Weather)

Air that promotes vertical motion, leading to turbulence, good visibility, cumuliform clouds, and showery precipitation.

Thunderstorm Formation Conditions

Requires moisture (water vapor), unstable air (air that wants to rise once lifted), and a lifting action (heating, fronts, terrain).

Cumulus Stage (Thunderstorm)

Characterized by dominant updrafts building towering cumulus clouds, little to no precipitation, and developing turbulence.

Mature Stage (Thunderstorm)

The most dangerous stage, with coexisting updrafts and downdrafts, heavy rain, hail, lightning, microbursts, and gust fronts; cloud tops can exceed 60,000 feet with anvil tops.

Dissipating Stage (Thunderstorm)

Characterized by dominant downdrafts, tapering precipitation, and loss of energy, but still with dangerous turbulence and possible wind shear.

Squall Lines

Highly hazardous lines of thunderstorms along a cold front, which can be hundreds of miles long and typically 10-20 miles wide, often nearly impassable for pilots.

Supercell Thunderstorm

A large, rotating thunderstorm, most likely to produce tornadoes, large hail, and severe turbulence.

Wind Shear

A sudden change in wind speed and/or direction over a relatively short distance, occurring horizontally or vertically, significantly affecting aircraft performance.

Vertical Wind Shear

A change in wind speed/direction with altitude that can cause rapid changes in climb rate, power required, and ground speed.

Horizontal Wind Shear

A change in wind speed/direction across a horizontal distance, which can cause drift changes, yaw corrections, and turbulence.

Microburst

One of the most dangerous sources of wind shear, characterized by severe localized downdrafts and strong horizontal outflow winds. It typically lasts less than 15 minutes but can have winds in excess of 100 knots.

Turbulence Penetration Speed

The technique and airspeed (e.g., 60 knots, 0.7 Vne, no lower than 57 knots) used when flying through moderate or severe turbulence to minimize structural loads and maintain control.

Virga

Precipitation that evaporates before reaching the ground. The evaporative cooling can create strong downdrafts, turbulence, and even microbursts, posing a risk of wind shear and rapid power changes.

Structural Icing

Ice forming on the external parts of the helicopter (rotor blades, airframe, engine inlets) due to supercooled water droplets freezing on contact, disrupting airflow and increasing weight.

Clear Ice

Smooth, glossy, heavy ice that spreads over surfaces, forming in 0°C to -10°C with large supercooled droplets; it's dangerous because it's hard to see, adds significant weight, and distorts rotor blade shape.

Rime Ice

Rough, milky ice that traps air bubbles, forming in colder temperatures (-10°C to -20°C) with small droplets; it's easier to see but still disrupts airflow and increases drag.

Mixed Ice

A combination of clear and rime ice, forming in -10°C to -15°C when temperature and droplet size vary in the same area.

Frost

Forms through deposition when water vapor changes directly into ice crystals on a cold aircraft surface that has been cooled by radiation in clear, cold, and humid conditions.

METAR

Aviation Routine Weather Report; an hourly surface weather report providing current conditions like winds, visibility, ceiling, temperature, dew point, and altimeter setting.

PIREP

Pilot Report; real-time weather reports from pilots used to confirm actual conditions aloft such as turbulence, icing, and cloud bases/tops.

UA (PIREP Code)

Signifies a routine weather report, meaning observed conditions are not considered immediately hazardous.

UUA (PIREP Code)

Indicates an urgent weather report, signifying potentially dangerous conditions like severe turbulence, hail, or low-level wind shear, requiring immediate attention.

Terminal Aerodrome Forecast (TAF)

A weather forecast issued every 6 hours, valid for 24 hours, forecasting conditions within 5 SM of an airport in a format similar to a METAR.

Area Forecast (FA)

(Discontinued) Formerly issued every 8 hours, valid for 18 hours, covering an area of several states, mostly used for categorical outlook (VFR, MVFR, IFR).

Winds & Temps Aloft (FB)

A forecast issued every 6 hours providing wind speed, direction (true north), and temperature information at various altitudes, with specific reporting rules for altitudes near the station and above 24,000 feet.

Surface Analysis Chart

Depicts fronts, pressure systems, and their movement over the entire U.S., offering a large-scale view of current weather patterns.

Significant Prognostic Chart (Prog Chart)

Issued every 6 hours, valid for 24 hours, providing forecasts of significant weather, including fronts, pressure systems, and precipitation areas.

Radar Summary Chart

Issued hourly, showing precipitation (not clouds), indicating intensity with different levels, direction of movement, speed, and maximum tops/bottoms.

Weather Depiction Chart

A graphical overview of observed flying conditions across the U.S., derived from METARs and updated every three hours, showing IFR, MVFR, and VFR areas based on ceiling and visibility.

IFR (Weather Depiction Chart)

Instrument Flight Rules conditions, indicated by shaded/hatched areas, where ceiling is less than 1,000 feet and/or visibility is less than 3 statute miles.

MVFR (Weather Depiction Chart)

Marginal VFR conditions, indicated by lightly shaded areas, where ceiling is 1,000-3,000 feet and/or visibility is 3-5 statute miles.

VFR (Weather Depiction Chart)

Visual Flight Rules conditions, indicated by unshaded (clear) areas, where ceiling is greater than 3,000 feet and visibility is greater than 5 statute miles.

AIRMETs

Airmen's Meteorological Information; provide information on weather hazards that are potentially hazardous but less severe than SIGMETs, covering widespread areas for all aircraft (especially smaller ones).

AIRMET Sierra

Warns of widespread areas of IFR conditions (ceilings < 1,000 feet and/or visibility < 3 SM) or extensive mountain obscuration.

AIRMET Tango

Warns of moderate turbulence, sustained surface winds greater than 30 knots, or non-convective low-level wind shear.

AIRMET Zulu

Warns of moderate icing and provides freezing level heights for flight planning.

SIGMET (WS)

Significant Meteorological Information; warns of adverse, non-convective weather widespread over an area of at least 3,000 square miles (e.g., severe turbulence, severe icing, volcanic ash).

Convective SIGMET (WST)

Warns of adverse weather that is convective in nature (e.g., squall lines, thunderstorms over a large area, embedded thunderstorms, hail ¾" or greater, surface winds 50+ knots).

ATIS (Automated Terminal Information Service)

A pre-recorded broadcast of non-control information at high-activity airports, including weather, runway in use, and other operational details, updated upon receipt of new weather.

CWA (Center Weather Advisory)

An unscheduled weather advisory issued by Air Traffic Control (ATC) to alert pilots of existing or anticipated adverse weather conditions.

World Aeronautical Chart (WAC)

Aeronautical chart with a 1:1,000,000 scale (1 inch = 14 NM), updated annually, used by high-speed aircraft for flight planning.

Sectional Chart

Aeronautical chart with a 1:500,000 scale (1 inch = 7 NM), valid for 56 days, most used chart for VFR flight, named after a major city it covers.

Terminal Area Chart (TAC)

Aeronautical chart with a 1:250,000 scale (1 inch = 3.5 NM), valid for 56 days, showing greater detail around Class B airspace airports and the surrounding area.

Helicopter Route Chart

Three-color charts with a 1:125,000 scale (1 inch = 1.7 NM), valid for 56 days, depicting aeronautical information useful to helicopter pilots in areas with high helicopter activity, including routes, heliports, and obstructions.

Chart Supplement (Airport/Facility Directory)

A series of civil/military flight information publications issued by the FAA, valid for 56 days, providing detailed airport information such as hours of operation, fuel types, and runway widths.

Filing Flight Plans

Submitting a detailed plan of your intended flight (destination, route, ETA, number of people) through entities like FSS or flight planning software, allowing for search initiation if something happens en route.

Opening Flight Plans

Activating a filed flight plan, typically done by contacting FSS airborne, via easy open/easy close services, or through apps like ForeFlight.

Closing/Cancelling Flight Plans

Notifying FSS upon arrival at your destination or anytime during the flight to terminate search and rescue responsibility. Failure to close a flight plan within 30 minutes of ETA can initiate search and rescue.

Class A Airspace

Airspace from 18,000 feet MSL up to Flight Level (FL) 600, requiring an IFR flight plan and ATC clearance to enter.

Class B Airspace

Surface to 10,000 feet MSL surrounding the nation’s busiest airports, depicted as a solid blue line. Requires ATC clearance, 2-way radio, transponder with altitude reporting, ADS-B Out, and VFR weather minimums of 3 statute miles visibility clear of clouds.

Class C Airspace

Surface to 4,000 feet MSL with towered airports, depicted as 2 concentric magenta lines. Requires 2-way radio, transponder with altitude reporting, established communication with ATC, and VFR weather minimums of 3 SM vis, 500' below, 1,000' above, 2,000' horizontal.

Class D Airspace

Surface to 2,500 feet MSL with towered airports, depicted as a dashed blue line. Requires 2-way radio, established communication with ATC, and VFR weather minimums of 3 SM vis, 500' below, 1,000' above, 2,000' horizontal.

Class E Airspace

Controlled airspace, depicted by magenta or blue vignette lines (700' or 1,200' MSL up to 14,500' MSL). Requires transponder with altitude reporting and ADS-B Out at or above 10,000' MSL. VFR weather minimums vary below and at/above 10,000' MSL.

Class G Airspace

Uncontrolled airspace, depicted by faded blue boundaries. VFR weather minimums vary by altitude (below/above 1,200' AGL, below/above 10,000' MSL) and time of day (day/night).

Crew Resource Management (CRM)

The effective use of all available resources (human, hardware, information) to achieve safe and efficient flight operations, including maintaining situational awareness, managing workload, and applying risk management.

Workload Management (CRM)

Prioritizing tasks ('Aviate – Navigate – Communicate'), using checklists, and planning routes to stay ahead of the aircraft and manage demands effectively during flight.

PAVE Checklist (CRM)

A risk management tool for preflight assessment, addressing the Pilot (IMSAFE), Aircraft, enVironment, and External pressures.

IMSAFE Checklist (CRM)

A personal minimums checklist used by pilots to assess their fitness to fly: Illness, Medication, Stress, Alcohol, Fatigue, Emotion/External Pressures.

Taxiway Centerline

A continuous yellow line indicating the center of a taxiway.

Taxiway Edge Lines (Solid Double Yellow)

Indicate pavement not usable for taxiing.

Taxiway Edge Lines (Dashed Double Yellow)

Indicate pavement usable to cross but not for taxiing on.

Hold Short Lines

Two solid, two dashed yellow lines across a taxiway, indicating a point beyond which an aircraft must not proceed without ATC clearance.