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Due to the continuousweatherwatchprovidedby TTF, the 30minute
buffers required by the above paragraphs donot apply. Flightswhichwill be
completedwithin the time of validity of the TTFmay beplannedwhollywith
reference to the destination TTF (AIPENR1.1).
TTFmay have either one visibility or two visibilities included in the report.
Operational requirementswill applywhen:
• the sole visibility is less than the alternateminimum; or
• thehigher visibility is less than the alternateminimum (AIPENR1.1).
Flightswhich cannot use TTFwill plan theflight on the current TAFuntil
such time as the destinationETA fallswithin the validity periods of a TTF
(AIPENR1.1).
For flight by aeroplanes under theVFR (day or night) and helicopters operating
under theVFR at night, the alternateminima are a ceiling of 1500 ft and a
visibility of 8 km (AIPENR 1.1).
For VFR helicopter operations by day, the alternateminima are the same as
for night (above) unless the additional conditions specified onpage359 are
met.When these additional conditions aremet, the alternate requirements
are as shownon page 358 (AIPENR 1.1).
A flight permitted to operateunder theVFR at night (seepage 328)must
provide for an alternate aerodromewithin one (1) hour’s flight time of the
destination unless:
•
thedestination is served by a radionavigation aid (NDB/VOR) and the
aircraft is fittedwith the appropriate radio navigation system capableof
using the aid, or
•
the aircraft isfittedwith an approvedGNSS receiver and thepilot and
aircraftmeet the requirementsof AIPGEN1.5 (AIPENR1.1).
For night VFR operations alternates are required basedon airport lighting and
navaids. Details of these requirements are given in the night VFR sectionon
page 348.
alternatedue to facilities
2 – preparat i on
alternatedue toweather