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highest will determine the minimum
altitude for that route or sector (that
is, each intended track between
reporting points), which will
ultimately depend on the accuracy of
your position, your maps and the
characteristics of the area, in terms
of weather or terrain. There are
different definitions, depending on
the airspace you are in, but they all
provide you with a lowest safe
altitude you can use in an emergency.
You are responsible for ensuring
that before take-off you've got
minima for the relevant times at
every destination and at least one
suitable alternative, which must be
noted on the Operational Flight Plan
if you intend to use them (this can
mean up to 8 airfields if you include
takeoff alternates—see below).
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 which case, one
copy must be kept in Ops, and
another on board. They will be
higher than the precalculated ones,
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 according 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 or two, 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, you're not allowed
to start an approach past the outer
marker (or at least descend below
1,000 feet above the aerodrome
elevation), even if you've established
visual reference above that height.
76 Canadian Professional Pilot Studies
As they say, there is an approach ban
(see the Glossary). Remember the
minimum visual approach visibility is
1200m, which also helps to guard
against shallow fog, and you need to
increase the limits if the autopilot is
unserviceable.
It's a good idea, in a commercial
environment, to have something up
your sleeve as well, by which I mean
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 minute sectors
to each flight.
Many ILSs use an NDB as an outer
marker, so why not be prepared to
convert to an ADF approach? or a
VOR (or whatever)? As a
professional, you should not expect
to land from an approach, so you
don’t get fixated and try to get in
when you shouldn’t. Non-standard
minima must be retained with flight
documentation.
Allowance for Wind Speed
Within 20 nm of ground over 2000
ft amsl, increase MOCA/MORA by:
Elevation
(feet)
0–30
Kts
31–50
Kts
51–70
Kts
+ 70
Kts
2–8000 + 500’ +1,000’ +1500’ +2000’
+ 8000 +1,000’ +1500’ +2000’ +2500’
This is because the venturi effect
over a ridge makes the altimeter
misread, as well as causing
turbulence and standing waves. A
combination of all this, plus
temperature errors (see below), can
make an altimeter overread by as
much as 3000 feet.
Temperature Correction
When the surface temperature is well
below ISA, correct MSAs by:
Surface Temp (ISA) Correction
–16°C to –30°C + 10%
–31°C to –50°C + 20%
–51°C or below + 25%
Takeoff Minima
IFR ones are governed by visibility,
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