PPL Navigation & Communication Theory cheat sheet

Great circle: shortest path between two points on a sphere; its track crosses each meridian at a different angle except at the equator and at the vertex.

Rhumb line (loxodrome): constant track angle relative to all meridians; longer than the great circle except along the equator or a meridian.

1 minute of latitude = 1 nautical mile = 1,852 m; 1 minute of longitude = 1 NM x cos(latitude).

Latitude 0-90 degrees N/S; longitude 0-180 degrees E/W from Greenwich; both are angles measured at the Earth's centre.

Conversion: degrees to radians multiply by pi/180; 1 radian = 57.3 degrees; circumference of the Earth is approximately 21,600 NM.

Departure (NM) = change of longitude in minutes x cos(mean latitude); difference of latitude in minutes equals distance in NM along a meridian.

True bearing is measured clockwise from true north 000-360; magnetic bearing = true bearing minus easterly variation (plus westerly).

Compass deviation is error caused by aircraft magnetic fields; it varies with heading, whereas variation depends only on geographic position.

Position can be defined as place (lat/long), bearing and distance from a fix, or as a point on a defined track.

Mercator projection: meridians parallel, rhumb lines straight, scale increases with latitude; unsuitable for great-circle plotting without a graticule.

Lambert conformal conic: straight-line great circles approximately, standard parallels where scale is exactly correct, used for ICAO 1:500,000 topographical/area charts.

Chart scale 1:500,000 means 1 cm on the chart equals 5 km on the ground; 1:250,000 gives twice the detail of 1:500,000.

Statute mile = 1,609 m; nautical mile = 1,852 m; 1 NM = 1.15 SM; kilometre = 0.54 NM.

AIP structure: GEN (general), ENR (en-route), AD (aerodromes); NOTAM and AIC supplement or amend the AIP.

Flight plan fields include aircraft identification, type, wake category, speed, level, route, destination, alternate and endurance (EET).

Fuel planning: trip fuel + contingency + alternate + final reserve + taxi; final reserve is 30 minutes holding for commercial transport aeroplanes.

Wind triangle: heading and TAS combined with wind vector give track and groundspeed; drift is the angle between heading and track.

Sunrise/sunset and civil twilight are tabulated for latitude bands; night is defined by the state authority, often between end of evening and start of morning civil twilight.

Dead reckoning position = last known fix advanced by heading, TAS, elapsed time and wind (heading and groundspeed).

Distance flown = groundspeed x time; time = distance / groundspeed; keep units consistent (minutes/60 for hours).

Wind triangle formulas: wind velocity = (track vector) - (heading/TAS vector); drift = track - heading (positive right).

Crosswind component = wind speed x sin(angle between wind and runway/track); headwind component = wind speed x cos(angle).

The circular slide rule side of the navigation computer solves TAS/altitude temperature (CAS to TAS) and fuel flow/time problems.

CAS to TAS: TAS increases about 2 percent per 1,000 ft of altitude at constant CAS; exact value from the computer with OAT and pressure altitude.

1 in 60 rule: a 1 degree track error over 60 NM gives 1 NM off track; off-track distance = distance flown x error/60.

Plotting convention: measure tracks and bearings with a protractor from the nearest meridian; apply variation to convert true to magnetic.

Position lines from two or more bearings, ranges or a bearing plus distance fix the aircraft position; the intersection of two position lines is a fix.

VOR: 108.0-117.95 MHz, line-of-sight, displays magnetic bearing from the station (radial); CDI centred with TO/FROM flag indicates on-course.

VOR accuracy is typically +/-1 degree ground station; use the 1-in-60 rule to convert radial error to lateral distance.

DME: UHF 960-1215 MHz, measures slant range; at high altitude and close range slant range exceeds ground distance significantly.

NDB/ADF: 190-1750 kHz, LF/MF, bearing is relative to aircraft heading; ADF reading plus heading gives magnetic bearing to the station (QDM).

ILS: localizer 108-112 MHz gives lateral guidance, glideslope UHF gives vertical guidance; typical glideslope 3 degrees, giving about 300 ft/NM.

Marker beacons: outer marker about 4-7 NM from threshold, middle marker about 3,500 ft from threshold; DME fixes are commonly used instead.

GNSS: GPS L1 1575.42 MHz; position from pseudoranges to at least 4 satellites; RAIM detects and excludes faulty satellites for integrity.

SBAS (e.g. EGNOS/WAAS) improves accuracy and integrity for approach use; GBAS provides local differential corrections at an aerodrome.

Radar: primary radar uses skin reflection with range and azimuth; secondary surveillance radar uses transponder replies (Mode A identity, Mode C altitude).

VHF band 118.000-136.975 MHz, line-of-sight, AM voice; 8.33 kHz channel spacing gives three times the channels of 25 kHz spacing.

Emergency frequencies: 121.5 MHz (civil VHF), 243.0 MHz (military UHF); distress call MAYDAY, urgency call PAN PAN.

Standard readback: clearances, runway, altitude, heading and frequency items must be read back; prefix with own call sign.

Phonetic alphabet and figure pronunciation are used for letters and digits; 'decimal' is spoken for the point in frequencies.

Squelch suppresses receiver noise between transmissions; volume should be set with squelch open so weak signals are not lost.

Transponder codes: 7700 emergency, 7600 radio failure, 7500 unlawful interference; Mode C reports pressure altitude.

Radio failure in IMC: follow the last assigned route/level and the published lost-communication procedure; in VFR continue under VFR and land.

HF (3-30 MHz) is used for long-range oceanic communication where VHF line-of-sight is not available; SELCAL reduces crew listening watch.

ISA: sea level 15 degrees C and 1013.25 hPa; temperature lapse 1.98 degrees C per 1,000 ft up to the tropopause (about 36,090 ft).

Pressure altitude = indicated altitude with subscale 1013.25 hPa; true altitude = pressure altitude corrected for temperature error.

Cold air below ISA makes the altimeter over-read; flying at a true altitude below the planned one, so terrain clearance is reduced.

QNH gives altitude above mean sea level; QFE gives height above the aerodrome reference point; QNE (1013.25) gives flight level.

Wind is named by the direction it comes from; veering means direction turns clockwise, backing anticlockwise.

In the northern hemisphere, wind veers with height and blows slightly across isobars towards low pressure due to surface friction.

Jet streams: strong narrow bands of wind near the tropopause, typically 100-200 kt; headwind/tailwind significantly alters groundspeed and fuel.

Thunderstorm hazards: severe turbulence, icing, hail, microburst wind shear; avoid cells by at least 20 NM and do not attempt to overfly.

Icing risk greatest at 0 to -20 degrees C in visible moisture; freezing rain indicates a warm front aloft with severe icing potential.

ICAO airspace classes A-G: A requires clearance for all flights and IFR only; B, C and D mix IFR and VFR with varying clearance and separation rules.

Class E controlled airspace: IFR gets separation, VFR does not require clearance in many states but must comply with VMC and equipment rules.

Class F is advisory; Class G is uncontrolled, with separation provided only through the see-and-avoid principle.

VMC minima vary with class and altitude; typical values are 5 km flight visibility and 1,000 ft vertical, 2,000 m horizontal from cloud in controlled airspace.

Semi-circular rule: magnetic tracks 000-179 use odd flight levels, 180-359 use even levels, separated by 1,000 ft or 2,000 ft above FL290.

Position reporting in uncontrolled airspace: identify, position, time, altitude/level, next position and ETA.

Special VFR allows VFR flight in controlled airspace below VMC by ATC clearance; it does not guarantee separation from other traffic.

Transponder and radio mandatory zones require a serviceable transponder and continuous two-way radio before entry.

Clearance readback and adherence: ATC clearance limits (level, route, speed) must be maintained; deviations require an amended clearance.

Convergency of meridians = change of longitude x sin(latitude); at the poles all meridians meet, so convergency equals the change of longitude.

Great circle track changes continuously; the vertex is the highest latitude reached, and the track crosses the equator at its maximum inclination.

Conversion angle (half convergency) = 0.5 x change of longitude x sin(mean latitude); applied to convert great circle to rhumb line bearings.

Composite great circle: limited by a maximum latitude, consisting of two great circle arcs joined by a parallel of latitude.

Mean sun and apparent sun differ; equation of time up to about +/-15 minutes, relevant to sunrise/sunset and twilight calculations.

Magnetic variation is shown on charts as isogonals; the agonic line is where variation is zero.

Altimetry: 1 hPa pressure change is about 30 ft near sea level; 1 degree C temperature error changes true altitude about 4 ft per 1,000 ft per degree.

Fuel required = taxi + trip + contingency (5 percent of trip) + alternate + final reserve + additional; extra fuel is at the commander's discretion.

Endurance (hours) = fuel available / fuel flow; safe endurance uses fuel excluding final reserve.

Specific range = air distance per unit fuel; maximum range is achieved near the speed for best lift/drag ratio.

Piston engine fuel flow varies with power setting and mixture; turbine engines use roughly proportional flow with altitude and Mach.

Groundspeed from wind triangle; ETA = departure time + (distance / groundspeed); update ETA at each waypoint using actual groundspeed.

Point of no return (equal time point): distance = (total endurance x groundspeed out) / (groundspeed out + groundspeed back) when outbound and return speeds differ.

Critical point (equal fuel point) uses fuel flow rather than time and is used when fuel consumption differs between outbound and return legs.

ILS categories: CAT I decision height 200 ft and RVR 550 m; CAT II 100 ft and 300 m; CAT III allows lower or zero decision height with autoland.

Localizer course width is about 5 degrees total at the threshold; glideslope width about 1.4 degrees, giving roughly 0.7 degree fly-up/fly-down.

VOR/DME area navigation: a radial plus DME distance defines a fix; the computer solves rho-theta position.

RNAV/GNSS approach minima depend on SBAS or baro-VNAV; LNAV minima are higher than LPV minima because vertical guidance differs.

Holding pattern: standard turns are right-hand, 1 minute inbound legs below 14,000 ft, 1.5 minutes above; entry via direct, parallel or teardrop.

Missed approach point is where the missed approach must be initiated if the runway is not in sight; MAPt may be a fix, a DME distance or a time.

NDB approach accuracy is limited by coastal refraction, night effect and thunderstorm static; VOR is less affected by these but is line-of-sight.

Radar vectoring provides headings and altitudes to intercept the final approach; the pilot must still be able to revert to the published procedure.

Initial call: station called, own call sign, position, altitude, and request; keep transmissions brief and use standard phraseology.

Frequency change: the pilot reads back the new frequency and confirms when established on it; 'contact' means the next station is expecting the call.

Clearance delivery and ground control handle route clearance and taxi; tower handles take-off and landing; approach/departure handle terminal phases.

Readback requirements include route clearances, hold short instructions, level instructions, headings and altimeter settings.

Position report format: call sign, position and time, flight level, next position and ETA, and the following significant point.

Distress (MAYDAY) has priority over all other communications; urgency (PAN PAN) is for safety but not immediate danger.

Test transmissions should be brief and identified; a readability scale of 1-5 is used to report signal quality.

8.33 kHz spacing channels are identified by three digits after the decimal, e.g. 118.005, 118.010; the frequency is spoken with each digit.

Geostrophic wind blows parallel to straight isobars; surface friction causes it to cross isobars at about 30 degrees over land and 10 degrees over sea.

Buys Ballot's law (northern hemisphere): with back to the wind, low pressure is on the left.

Thermal wind: the wind change with height is related to the horizontal temperature gradient; cold advection causes backing with height.

Foehn/chinook: descending air on the lee side of mountains warms and dries; turbulence and mountain waves occur on the lee side.

Low-level wind shear and microbursts are most dangerous below 1,000 ft AGL; go-around is the standard recovery from a severe shear encounter.

Tropopause height varies from about 25,000 ft at the poles to 55,000 ft at the equator; jet streams are found near it.

Volcanic ash and sandstorms reduce visibility and damage engines; SIGMETs warn of these and of severe turbulence and icing.

Class A: IFR only, all aircraft separated; Class B: IFR and VFR, all separated; Class C: IFR separated from all, VFR separated from IFR.

Class D: IFR separated from IFR, VFR receives traffic information; Class E: IFR separated, VFR receives traffic information where practical.

Class G: no ATC service, no separation; flight information service may be available on a discrete frequency.

Controlled aerodromes have ATZ/CTR; entry requires clearance and two-way radio unless a specific exemption applies.

Alerting service: ATC alerts search and rescue when an aircraft is overdue or in emergency; the flight plan and position reports support this.

Flight information service provides weather, traffic and aerodrome information but does not issue clearances or separation.

Advisory service (e.g. in Class F) provides traffic information but no separation; pilots remain responsible for collision avoidance.

Airspace infringements are avoided by studying charts, noting vertical limits and requesting a clearance before entry.

Altimeter errors: position error, instrument error, temperature error and pressure error; only temperature and pressure errors are correctable by the pilot.

Airspeed indicator errors: position error, instrument error, compressibility error and density error; CAS corrects position and instrument error.

Mach number = TAS / local speed of sound; speed of sound decreases with temperature, about 661 kt at sea level ISA.

Machmeter indications are independent of pressure altitude and temperature errors that affect the ASI, because Mach is a ratio.

Turn indicator shows rate of turn; a standard rate turn is 3 degrees per second, giving a 2-minute 360-degree turn.

Heading indicator/gyro errors: drift and apparent wander; precession and real wander cause slow heading errors, checked against the magnetic compass.

Magnetic compass errors: variation, deviation, turning error (acceleration error in the northern/southern hemisphere), and dip errors.

GPS constellation: 24+ satellites in 6 orbital planes at about 20,200 km altitude, 12-hour orbital period.

RAIM availability depends on satellite geometry; a minimum of 5 satellites is needed for RAIM detection, 6 for exclusion.

Receiver autonomous integrity monitoring does not protect against ionospheric errors common to all satellites; SBAS or GBAS is used instead.

Ionospheric delay is largest near the equator and at high latitudes and varies with solar activity; dual-frequency receivers correct it.

GPS accuracy: standard positioning service about 15 m horizontal; SBAS improves to a few metres.

GNSS jamming and spoofing can cause loss of position or false position; cross-check with VOR/DME or dead reckoning.

Altitude from GNSS is referenced to the WGS-84 ellipsoid, not mean sea level; the geoid separation must be applied for height.

Preferred routes and airways are published with minimum en-route altitudes (MEA) ensuring terrain and radio reception clearance.

Minimum obstacle clearance (MOC) for en-route IFR is typically 1,000 ft in non-mountainous and 2,000 ft in mountainous terrain.

Route selection considers wind at cruise level, airway direction rules, restricted and danger areas and fuel.

Equal time point and point of no return calculations assume constant wind and fuel flow; update with actual winds in flight.

Alternate aerodrome weather minima: forecast must meet the operator's planning minima, which may require a higher ceiling and visibility than the approach minima.

Take-off alternate is required when the departure aerodrome weather is below the operator's landing minima and the destination is more than a specified time away.

Flight plan EET to destination plus fuel endurance determines the search and rescue alerting time.

Plot a fix by transferring a bearing from the compass rose through the station to the aircraft position; use the nearest meridian for track measurement.

To measure a true track, align the protractor with a meridian and read the angle clockwise from north.

Apply magnetic variation with the mnemonic: variation east, magnetic least (true minus east variation = magnetic).

Drift and track error: track error is the angle between the planned track and the actual track; drift is between heading and track.

Closing angle from a second position line allows a direct heading to destination: heading change = track error + closing angle.

Wind vector plotting: draw wind direction as the direction the wind comes from, and the vector points towards the direction it blows to.

Scale measurement: use the chart scale bar, not the latitude scale, for distance on a Lambert or Mercator chart except along a meridian.

VHF communication range depends on altitude: approximately range (NM) = 1.23 x square root of height in feet.

121.5 MHz is monitored by emergency services and many aircraft; 123.45 MHz is used for air-to-air communication in some regions.

VHF direction finding (VDF) gives a magnetic bearing from the station; classes of fix depend on the accuracy of the reported heading.

ACARS and CPDLC provide data link communication; CPDLC is used in oceanic and some continental airspace for clearances.

Emergency locator transmitter (ELT) transmits on 121.5 and 406 MHz; the 406 MHz signal is detected by the COSPAS-SARSAT system.

Antenna placement and line-of-sight: terrain and aircraft attitude can shadow VHF signals; use a relay or HF when out of range.

Frequency spacing 8.33 kHz requires radio equipment certified for it; older 25 kHz-only radios cannot use those channels.

TAF: aerodrome forecast valid typically 9-30 hours; trend forecasts (TTF) give changes within 2 hours of issue.

METAR: routine observation, issued hourly or half-hourly; SPECI for significant changes.

SIGMET: warning of severe turbulence, icing, volcanic ash, tropical cyclones and severe squalls; valid for 4 hours (6 for volcanic ash).

AIRMET/GAMET: warnings of moderate hazards, low visibility, mountain obscuration; useful for light aircraft.

Wind and temperature aloft forecasts (FD) give winds and temperatures at specified levels and are used for flight planning.

Freezing level forecast and icing forecasts (e.g. in GAMET) determine levels where icing is likely.

Significant weather charts (SIGWX) show fronts, jet streams, CAT and CB clusters for route planning.

Semi-circular rule applies above the transition altitude; transition level is the lowest flight level above the transition altitude.

Transition altitude is published for each aerodrome; below it, altimeters are set to QNH, above to standard 1013.25.

Quadrantal rule: tracks 000-089 use odd levels, 090-179 even, 180-269 odd, 270-359 even (in some states, e.g. UK).

RVSM airspace (FL290-FL410) requires 1,000 ft separation, approved altimetry and autopilot; outside RVSM, 2,000 ft is used above FL290.

Mandatory occurrence reporting covers accidents, serious incidents and certain defects; voluntary reporting schemes exist for other safety events.

Right-of-way rules: converging aircraft give way to the one on the right; landing aircraft have priority over others in the pattern.

Minimum fuel and emergency fuel declarations: 'minimum fuel' means no undue delay can be accepted; 'MAYDAY FUEL' declares an emergency.

Groundspeed = distance / time; if 120 NM takes 40 minutes, groundspeed is 180 kt.

Fuel flow (kg/h) = fuel used / time; fuel used = flow x time.

Wind component along track = TAS - groundspeed (headwind positive) when track and heading are aligned.

Drift angle sin(drift) = (wind speed x sin(wind angle to track)) / TAS; use the computer for exact values.

Radius of turn = TAS / (rate of turn in radians per second); at standard rate, radius (NM) = TAS / 60 x (1/pi) approximately.

1 in 60 rule also applies to height: at 60 NM, 1 degree of glidepath error is about 1 NM (6,000 ft) of height error.

Time to a fix from a position line = distance along track / groundspeed; use two position lines to derive groundspeed and drift.

VOR radial is the magnetic bearing from the station; a TO indication means the selected course leads to the station.

VOR line-of-sight range approximately 1.23 x square root of height in feet, similar to VHF communication.

DME slant range error: at 6 NM ground distance and 6,000 ft altitude, slant range is about 6.5 NM.

NDB bearing is affected by coastal refraction (bends towards the coast), night effect and static from thunderstorms.

ILS localizer gives left/right guidance; the glideslope gives up/down guidance; both are combined on the flight director or HSI.

ILS critical area must be protected during low visibility operations; vehicles and aircraft can cause signal disturbance.

Marker beacon colours: outer blue, middle amber, inner white; each has a distinct audio tone.

PBN specifies RNAV and RNP systems; RNP requires on-board performance monitoring and alerting, RNAV does not.

RNP 10 and RNP 4 are used in oceanic airspace; RNP 0.3 for terminal and approach procedures.

Required navigation performance (RNP) value is the lateral accuracy in NM that must be maintained for 95 percent of the flight time.

ADS-B out transmits position, altitude and identity; required in many airspace regions for IFR and some VFR flights.

GNSS approach minima: LNAV, LNAV/VNAV and LPV; LPV uses SBAS and can give decision heights down to 200 ft.

Baro-VNAV uses barometric altitude for vertical guidance and is limited by temperature; cold temperature corrections may be required.

RAIM prediction must be checked before an RNP approach; a RAIM outage requires an alternate procedure.

Radio failure: squawk 7600, continue according to the last clearance or the published lost-communication procedure.

In IMC, maintain the last assigned level for a specified time, then follow the flight plan route; in VFR, remain VFR and land.

Emergency descent: turn off the autopilot, set speed and spoilers, descend to 10,000 ft or MSA, and broadcast MAYDAY.

Ditching and evacuation: transmit MAYDAY with position, number of persons and nature of emergency; set transponder 7700.

Interception: acknowledge by rocking wings, follow the intercepting aircraft; if unable, continue on route and broadcast on 121.5.

Emergency frequency 121.5 is monitored by ATC and many aircraft; use it for distress and urgency communications.

Survival radio and ELT: activate ELT on 121.5/406 MHz after a forced landing; the 406 MHz signal gives a position to SAR.

Altimeter setting: QNH gives altitude above MSL; QFE gives height above aerodrome; QNE (1013.25) gives flight level.

Pressure altitude = indicated altitude when subscale is 1013.25; true altitude = pressure altitude corrected for temperature.

Cold temperature correction: true altitude is lower than indicated in cold air; apply a correction on approach in very cold conditions.

1 hPa = 30 ft near sea level; 1 hPa = 27 ft at higher altitude; use 30 ft for quick calculations.

Wind at altitude: wind speed generally increases with height; veering with height in the northern hemisphere due to thermal wind.

Jet stream core winds can exceed 200 kt; the polar front jet is associated with the polar front and mid-latitude depressions.

Mountain wave: strong winds across a ridge cause lee-side turbulence and downdrafts; avoid flying close to the lee side.

ATC clearance: an authorization to proceed under specified conditions; it does not relieve the pilot of responsibility for terrain clearance or collision avoidance.

Radar control: controller provides headings, altitudes and speeds; pilot must advise if unable to comply.

Position reporting in procedural airspace: report at each significant point with time, level and next point.

Separation: vertical separation is 1,000 ft in RVSM, 2,000 ft outside; horizontal separation is provided by radar or procedural means.

Emergency: declare MAYDAY, squawk 7700, and follow ATC instructions; ATC will provide priority and separation.

Airspace classes: A, B, C, D, E, F, G; each defines clearance, separation and VMC requirements.

Transponder mandatory zones require Mode A/C or Mode S; Mode S provides aircraft identity and altitude.

Trip fuel = fuel from take-off to landing at destination; contingency fuel is typically 5 percent of trip fuel.

Alternate fuel = fuel from destination to alternate plus approach and landing; final reserve is 30 minutes holding.

Additional fuel is required for cases such as a destination with no alternate; operator policy defines the amount.

Taxi fuel is included in the fuel plan but not in trip fuel; it covers engine start, taxi and APU.

Fuel check: at each waypoint compare fuel remaining with the flight plan; a significant difference requires a revised plan.

Equal time point (ETP) is the point where time to destination equals time back to the departure or alternate.

Point of no return (PNR) is the point beyond which the aircraft cannot return to the departure aerodrome with the fuel remaining.

Navigation computer: the wind side solves heading, track, TAS, wind and groundspeed; the circular slide rule solves time, distance, fuel and conversions.

To find TAS: set pressure altitude against temperature, read TAS on the outer scale against CAS on the inner scale.

To find groundspeed: set wind direction under the true index, mark wind speed, rotate to track, read groundspeed and drift.

Conversions: 1 NM = 1.852 km; 1 SM = 1.609 km; 1 kg = 2.205 lb; 1 US gallon = 3.785 litres.

Time calculations: set groundspeed on the outer scale against 60 on the inner scale, then read time against distance.

Fuel calculations: set fuel flow against 60 to read fuel used per minute; multiply by time for total fuel.

Track error and closing angle: use the 1 in 60 rule to calculate heading changes to regain track.

GNSS position: receiver measures pseudoranges to satellites and solves for latitude, longitude, altitude and time.

Dilution of precision (DOP) depends on satellite geometry; low DOP means better accuracy.

SBAS: geostationary satellites broadcast corrections and integrity; coverage is regional (e.g. EGNOS in Europe, WAAS in North America).

GBAS: ground station provides local corrections and integrity for precision approach; supports CAT I and higher.

Primary radar: detects aircraft by reflected pulses; range and azimuth are displayed; no altitude information.

Secondary radar: interrogates transponder; Mode A gives identity, Mode C gives altitude, Mode S gives unique address and data.

TCAS: traffic alert and collision avoidance system; resolution advisories must be followed unless it conflicts with ATC instructions.

Readback: route clearances, hold short instructions, level instructions, headings and altimeter settings must be read back.

Initial call: station called, own call sign, position, altitude and request; keep it brief.

Frequency change: read back the new frequency and confirm when established; 'contact' means the next station is expecting the call.

Position report: call sign, position and time, level, next position and ETA, and the following significant point.

Distress: MAYDAY repeated three times; urgency: PAN PAN repeated three times; both have priority over other communications.

Test transmission: brief and identified; readability scale 1-5 is used to report signal quality.

Phonetic alphabet: Alpha, Bravo, Charlie...; digits are spoken individually, with 'decimal' for the point.

Fronts: cold front steep and fast-moving with squall lines; warm front shallow with widespread cloud and precipitation.

Low pressure: air converges and rises, causing cloud and precipitation; high pressure: descending air, generally clear.

Thunderstorm life cycle: cumulus, mature and dissipating; the mature stage has the strongest updrafts, hail and lightning.

Icing: clear ice from large supercooled droplets, rime ice from small droplets; both increase weight and reduce lift.

Wind shear: sudden change in wind speed or direction; microbursts cause severe downdrafts and are a major hazard on approach.

Volcanic ash: abrasive and can melt in engines; avoid the ash cloud and report any encounter.

SIGMET: issued for severe turbulence, icing, volcanic ash, tropical cyclones and severe squalls; valid for 4 hours.

Controlled airspace: ATC provides separation; clearance required for IFR and, in most classes, for VFR.

Uncontrolled airspace (Class G): no separation service; pilots use see-and-avoid and may use flight information service.

VMC minima: vary by class and altitude; typical 5 km visibility and 1,000 ft vertical separation from cloud in controlled airspace.

Special VFR: clearance to operate in controlled airspace below VMC; pilot must remain clear of cloud and in sight of ground.

Semi-circular rule: magnetic tracks 000-179 use odd flight levels; 180-359 use even flight levels; separated by 1,000 ft.

Position reporting: required in procedural airspace and at mandatory reporting points; use standard format.

Transponder mandatory zones: require serviceable transponder and continuous two-way radio before entry.