CPL Navigation flashcards
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31 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Nautical mile definition
- One minute of latitude, equal to 1,852 metres or 6,076.1 feet. Used for all air navigation distances because it relates directly to angular measurement on the Earth's surface.
- Great circle
- The shortest path between two points on a sphere, formed by a plane through both points and the Earth's centre. Its direction changes continuously along the route.
- Rhumb line
- A line crossing every meridian at the same angle, appearing straight on a Mercator chart. It is longer than the great circle except along the equator or a meridian.
- Mercator chart properties
- Scale increases with latitude, so straight lines are rhumb lines and great circles curve poleward. Suitable for plotting constant-heading legs but not for measuring long great-circle distances directly.
- Lambert conformal conic
- A chart projection using a cone intersecting the Earth, giving a straight-line great circle approximately. Commonly used for aeronautical charts in mid-latitudes because angles are preserved.
- Magnetic variation
- The angular difference between true north and magnetic north at a location. East variation is subtracted from true to obtain magnetic; west variation is added.
- Compass deviation
- The error caused by aircraft magnetic fields, tabulated on a compass card for each heading. Applied after variation when converting between magnetic and compass directions.
- Track error calculation
- Track error in degrees equals distance off track divided by distance flown, multiplied by 60. Used to determine the heading correction needed to regain the intended track.
- Closing angle
- The angle subtended at the aircraft by the remaining distance to destination, calculated as distance off track divided by distance remaining times 60. Added to track error for the correction heading.
- One-in-sixty rule
- An angle of one degree subtends one nautical mile at a distance of 60 nautical miles. Basis for quick drift and track-error mental calculations in flight.
- Wind triangle
- Vector relationship between true airspeed and heading, wind velocity, and resulting groundspeed and track. Solved graphically or with the sine rule to find drift and groundspeed.
- Drift angle formula
- Drift in degrees approximately equals crosswind component divided by true airspeed, multiplied by 60. Positive drift means the wind pushes the aircraft right of heading.
- Crosswind component
- Wind speed multiplied by the sine of the angle between wind direction and runway or track. Determines the lateral wind effect on takeoff, landing, and drift.
- Pressure altitude formula
- Pressure altitude equals elevation plus 30 feet for each hectopascal that QNH is below 1013.25. Used for performance charts and flight-level calculations.
- Density altitude formula
- Density altitude equals pressure altitude plus 120 times the difference between actual temperature and ISA temperature at that altitude. Higher values degrade aircraft performance.
- ISA sea level values
- International Standard Atmosphere at sea level: 15 degrees Celsius, 1013.25 hectopascals, and a lapse rate of about 1.98 degrees Celsius per 1,000 feet up to the tropopause.
- True altitude correction
- When air is colder than ISA, true altitude is lower than indicated altitude. The error is roughly 4 feet per 1,000 feet per degree Celsius of ISA deviation.
- Fuel plan components
- Taxi, trip, contingency, alternate, final reserve, and additional fuel. Each is computed separately and summed to give total fuel required for the flight.
- Final reserve fuel
- Fuel required to hold for a specified period, commonly 30 minutes at 1,500 feet above the alternate, at holding fuel flow. It must remain unused on arrival.
- Contingency fuel
- Fuel added to cover unforeseen deviations, often 5 percent of trip fuel or a fixed time equivalent. It is not available for normal planning use.
- Endurance calculation
- Endurance in hours equals usable fuel divided by hourly fuel flow. Safe endurance subtracts reserve fuel before dividing, giving usable flight time.
- Range calculation
- Range in nautical miles equals groundspeed multiplied by safe endurance in hours. Wind changes groundspeed and therefore range for a given fuel load.
- Specific range
- Nautical miles flown per unit of fuel, equal to groundspeed divided by fuel flow. Maximum specific range occurs near the speed for best lift-to-drag ratio.
- Weight and balance moment
- Moment equals weight multiplied by arm, the distance from the reference datum. Summing moments and dividing by total weight gives the centre of gravity position.
- Centre of gravity limits
- Forward and aft limits within which the aircraft must remain for all phases. Exceeding aft limits reduces stability; exceeding forward limits increases stall speed and trim drag.
- Navigation log purpose
- A worksheet recording waypoints, tracks, wind, headings, speeds, times, and fuel for each leg. It allows in-flight comparison of planned and actual progress.
- NOTAM
- A notice distributed to flight crews containing time-critical information about facilities, services, or hazards not published in advance. Must be reviewed before flight planning is complete.
- AIP and supplements
- The Aeronautical Information Publication contains permanent operational data; supplements publish temporary changes. Both must be current when preparing a flight plan.
- Alternate aerodrome requirement
- A destination alternate is required when destination weather is marginal or no instrument approach exists. The alternate must satisfy published weather minima and fuel reserves.
- Chart currency check
- Each aeronautical chart carries an effective date and edition number. Using an expired chart risks navigating with obsolete frequencies, airspace, or obstacles.
- VFR fuel requirement
- Common regulatory minimum: enough fuel to reach destination plus 30 minutes by day or 45 minutes by night at normal cruise. Always confirm the exact national rule.