Home Table of Contents

9.31 Weather Services

Quiz

Back Next

Mandatory Forecast

Before beginning a flight, a pilot in command must study all available information appropriate to the intended operation and, in the cases of flights away from the vicinity of an aerodrome and all IFR flights must make a careful study of:

  1. current weather reports and forecasts for the route to be flown and the aerodromes to be used;
  2. the airways facilities available on the route to be flown and the condition of those facilities;
  3. the condition of aerodromes to be used and their suitability for the aircraft to be used;
  4. the Air Traffic Control rules and procedures pertaining to the particular flight; and
  5. all Head Office and FIR NOTAM applicable to the en route phase of flight, and location-specific NOTAM for aerodromes.

The pilot must then plan the flight in relation to the information obtained. Note: Full details on the services provided by the briefing office(s) are available in ERSA GEN.

Forecasts

A forecast must be either a flight forecast or an area forecast with an aerodrome forecast for the destination and, when required, the alternate aerodrome. For a flight to a destination for which a prescribed instrument approach procedure does not exist, the minimum requirement is an Area Forecast.

For flights for which a forecast is required and cannot be obtained, the flight is permitted to depart provided the pilot is satisfied that the weather at the departure point will permit the safe return of the flight within one hour of departure. The flight is permitted to continue provided a suitable forecast is obtained for the intended destination within 30 minutes after departure.

For flights to a destination for which an aerodrome forecast is required and cannot be obtained or is “provisional”, the flight is permitted to depart provided an alternate aerodrome meeting all the requirements specified in ENR 1.1 Section 72. is provided.

CHTR, AWK and PVT operations under the VFR at night must not be conducted unless the forecast indicates that the flight can be conducted in VMC at not less than 1000FT above the highest obstacle within 10NM either side of track.

A pilot in command must ensure that the forecasts cover the period of the flight and that the aerodrome forecasts for the destination and alternate aerodromes, to be nominated in the flight plan, are valid for a period of not less than 30 minutes before and 60 minutes after the planned ETA.

When a flight is delayed so that the meteorological and operational information does not cover the period of flight, updates must be obtained as necessary, to allow the flight to be concluded safely.

A series of flights may be included on the one flight plan provided that:

  1. the meteorological forecast will cover all the flights; and
  2. relevant AIS information is available at flight planning.

When pre-flight briefing is obtained more than one hour prior to ETD, pilots should obtain an update before departure to ensure that the latest information available can be used for the flight. The update should be obtained by NAIPS pilot access, telephone, or, when this is impracticable, by radio.

Alternate Aerodromes

General

A pilot in command must make provision for flight to an alternate aerodrome, when required, in accordance with the following paragraphs.

When a flight is required to provide for an alternate aerodrome, any aerodrome may be so nominated for that flight provided:

  1. it is suitable as a destination for that flight; and
  2. is not an aerodrome for which that flight would require to provide for an alternate aerodrome.

When an aerodrome forecast is not available or is “provisional”, the pilot in command must make provision for a suitable alternate that has a firm forecast.

Weather Conditions

Except when operating an aircraft under the VFR by day within 50NM of the point of departure, the pilot in command must provide for a suitable alternate aerodrome when arrival at the destination will be during the currency of, or up to 30 minutes prior to the forecast commencement of, the following weather conditions:

  1. cloud – more than SCT below the alternate minimum.
  2. Note: In determining requirements for alternate aerodromes, forecast amounts of cloud below the alternate minima are cumulative. For determining requirements, the cumulative cloud amount is interpreted as follows:

    • FEW plus FEW is equivalent to SCT,
    • FEW plus SCT is equivalent to BKN,
    • SCT plus SCT is equivalent to BKN or OVC.
  3. visibility – less than the alternate minimum; or
  4. visibility – greater than the alternate minimum, but the forecast is endorsed with a percentage probability of fog, mist, dust or any other phenomenon restricting visibility below the alternate minimum; or
  5. wind – a crosswind or downwind component more than the maximum for the aircraft.

    Note: Wind gusts must be considered.

When operating a helicopter under the VFR, and the use of helicopter VMC is permissible at the destination, the pilot in command must provide for a suitable alternate aerodrome when either of the following conditions is forecast at the destination:

  1. cloud – more than SCT below a ceiling of 1,000FT; or
  2. visibility – less than 3,000M.

When weather conditions at the destination are forecast to be as specified at para 72.2.1, but are expected to improve at a specific time, provision for an alternate aerodrome need not be made if sufficient fuel is carried to allow the aircraft to hold until that specified time plus 30 minutes.

When weather conditions at the destination are forecast to be above the values specified at para 72.2.1, but, additionally, intermittent or temporary deteriorations in the weather below the values are forecast, provision of an alternate need not be made if sufficient additional fuel is carried to allow the aircraft to hold for:

  1. 30 minutes for intermittent deterioration (INTER); and
  2. 60 minutes for temporary deterioration (TEMPO).

When thunderstorms or their associated severe turbulence or their probability is forecast at the destination, sufficient additional fuel must be carried to permit the aircraft to proceed to a suitable alternate or to hold for:

  1. 30 minutes when the forecast is endorsed INTER; or
  2. 60 minutes when the forecast is endorsed TEMPO.

When a forecast has multiple INTER or TEMPO deteriorations and holding fuel will be carried, fuel must be carried to hold for only the most limiting requirement. INTER and TEMPO holding fuel requirements are not cumulative.

When TAFs include a FM period, during which time an operational requirement will either become effective or be removed, the timing for the change in operational requirement is as follows:

  1. When the weather during the FM period is forecast to create an operational requirement, that operational requirement will become effective 30 minutes before the start of the FM time.
  2. When the weather during the FM period is forecast to remove an operational requirement, that operational requirement will remain effective until 30 minutes after the FM time stated in the forecast that removes the operational requirement.

The additional fuel required by paras 72.2.4 or 72.2.5 must be carried when the ETA of the aircraft at its destination or alternate falls within the period 30 minutes before the forecast commencement of these deteriorations to either:

  1. 30 minutes after the forecast cessation of these deteriorations; or
  2. sufficient fuel is carried to hold until 30 minutes after the forecast time of cessation of these deteriorations.

Due to the continuous weather watch provided by TTF, the 30 minute buffers required by paragraphs 72.2.7 and 72.2.8 do not apply.

Flights which will be completed within the time of validity of the TTF may be planned wholly with reference to the destination TTF.

TTF may have either one visibility or two visibilities included in the report. Operational requirements will apply when:

  1. the sole visibility is less than the alternate minimum, or
  2. the higher visibility is less than the alternate minimum.

Flights which cannot use TTF will plan the flight on the current TAF until such time as the destination ETA falls within the validity period of a TTF.

For IFR flights, the alternate minima are as follows:

  1. For aerodromes with an instrument approach procedure, the alternate minima published on the chart (ENR 1.5, Section 6.).
  2. For aerodromes with an instrument approach procedure where an aerodrome forecast is unavailable or is “provisional”, the pilot in command must make provision for a suitable alternate.
  3. For aerodromes without an instrument approach procedure, the alternate minima are the lowest safe altitude for the final route segment plus 500FT and a visibility of 8KM (also refer ENR 1.10 sub-section 1.4).

For flight by aeroplanes under the VFR (day or night) and helicopters operating under the VFR at night, the alternate minima are a ceiling of 1,500FT and a visibility of 8KM.

For VFR helicopter operations by day, the alternate minima are the same as for night unless the additional conditions specified in ENR 1.2 para 2.6 are met. When these additional conditions are met, the alternate minima requirements are as shown in para 72.2.2.