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otherwise they wouldn't be flying.
In any case, you are responsible for
ensuring that before take-off you've
got weather minima for the relevant
times at every destination and at
least one suitable alternative, which
must be noted on the Nav Log if
you intend to use them (this can
mean up to 8 airfields if you include
takeoff alternates—see below). For
Commercial Air Transport, foreign
airfields are also subject to UK rules,
and minima which apply to you will
be the highest of:
· Those established by the State
in which you are flying.
· UK minima, as shown in the
Airway Manual.
· Basic minima established by
your Company.
Remember that foreign airfields tend
to close down automatically when
the weather gets too bad, whereas an
airport authority in UK may only
close down on their own initiative in
the case of snow or a blocked
runway – however, attempts to land
in marginal weather are reported
back to the Authorities.
While you're not allowed to reduce
the limits given, you are actively
encouraged to increase them if you
think it's necessary. As they're
calculated for fog conditions with
little or no wind, you should make
due allowance for rain and/or
crosswinds. Naturally, minima are
not valid if anything affecting their
calculation has been changed
through NOTAMs, or as instructed
by ATC.
Minima not in the Airways Manual
can be worked out with figures in
the Ops Manual. In this case, one
copy of your calculations must be
retained in Ops, and another carried
on board. However, airfields used
regularly in this way should be
permanently in the Manual, and it's
the Company's responsibility to selfcheck
them. Such calculations will be
higher than anything precalculated,
because they come from blanket
figures which allow for aircraft in
lower performance groups avoiding
obstacles visually if an engine fails
on take-off, so Cloud Ceiling figures
will vary as to where you can start to
construct your Net Flight Path data
(see Performance). If that happens at
300 feet (that is, your engines are
assumed to be working till then),
expect a 300 ft Cloud Ceiling.
The same principle goes for RVR
figures, which are related to the time
required to see and avoid
obstacles—if you're going at 90
knots, 1500m RVR will give you
thirty seconds between seeing and
missing anything. RVR is the
distance you can see in the direction
of take-off or landing, determined by
a certain procedure, usually with the
aid of a transmissometer, and based
on runway lights at setting 3. The
distance given is taken as the RVR
for the time being, that is, only valid
for a short time. If the reported RVR
is below your expected minima,
62 Operational Flying
you're not allowed to start an
approach past the outer marker (or
at least descend below 1000' above
aerodrome elevation), even if you've
established visual reference above
that height. As they say, there is an
approach ban (see Glossary). The
minimum visual approach visibility is
800m (1200m in Canada), to guard
against shallow fog. Increase the
limits if the autopilot is out.
It's a good idea, in a commercial
environment, to have something up
your sleeve, meaning what do you do
if the ILS goes off halfway down an
approach? In training, you would
probably go around, but that's
expensive and the commercial
department will love you if you keep
adding 10 minutes to each flight.
Many ILSs use an NDB as an outer
marker, so why not be ready to
convert to an ADF approach? or a
VOR (or whatever)? Most
professionals don’t expect to land
from an approach, which means they
don’t get fixated and try to get in
when they shouldn’t. Non-standard
minima must be retained with flight
documentation for 3 months.
Planning Requirements
Take-Off/Alternates
If your multi-engined aeroplane
can either stop or continue to 1500'
above the aerodrome while clearing
obstacles by the margins, the takeoff
minima may not be less than:
Facilities RVR
(m)
Vis (m)
Cat D
Nil (Day Only) 500
Runway Edge Ltg and/or
Centreline Marking
250 300
Runway Edge, Centre Lights 200 250
Runway Edge, Centre Lights
and Multi RVR
150 200
At night, at least runway edge and
end lights are required. RVR/Vis for
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