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your discretion if you have the whole
of the runway continuously in sight.
The minimum MDH and visibility
for visual manoeuvring are 250 ft
and 800m for helicopters, and as per
this table for aeroplanes:
Aircraft Category A B C D
MDH (ft) 400 500 600 700
Min Met Vis (m) 1500 1600 2400 3600
Visual Approach
The minimum RVR for a visual
approach is 800 m (1200 in Canada).
Aerodromes Without Approach Aids
If your destination doesn't have any
aids (unserviceability, perhaps), you
can either fly to your destination in
VMC, or under IFR to where you
can carry out an Instrument
Approach, then continue under VFR
to your original destination, which
must be within 25 miles.
In the latter case, permission must
be obtained from ATC at the letdown
point, and forecast weather
between the two aerodromes must
be better than 1000 ft cloudbase agl
and 3 nm visibility. This also means
that if you don't maintain the above
VFR conditions, you will be flying
below 1000 feet above Decision
Height en route, or if you're over the
sea, actually below DH where you
should really be under an approach
ban (see glossary). You should not
be below MSA unless you can
identify your position, and since
you're flying towards an aerodrome
without approach aids, you could
find that difficult. Your Company
may apply some rules in this case,
but you will more than likely have to
apply your own.
Airborne Radar Approach (ARA)—
Helicopters Overwater
You cannot undertake one unless
your radar is good enough to
provide course guidance for obstacle
clearance (cloud ceiling must also be
suitable for a safe landing). Before
starting, a clear path must exist on
the screen for the final and missed
approach segments. If lateral
clearance from any obstacle will be
less than 1 nm, you should either
approach to a nearby target structure
and proceed visually, or make the
approach from another direction
leading to a circling manoeuvre.
Minimum Descent Height (MDH)
This is determined from a radio
altimeter. It must be at least 200 ft
by day and 300 ft by night. The
MDH for an approach leading to a
circling manoeuvre shall be at least
300 ft by day and 500 ft by night.
Minimum descent altitude (MDA)
May only be used if the radio
altimeter is unserviceable, and shall
be at least MDH + 200 ft, based on
a calibrated barometer at the
Operational Procedures 69
destination or the lowest forecast
QNH for the region.
Decision range (DR)
At least ¾ nm unless you can
convince the CAA otherwise.
Visual reference
You cannot continue an approach
beyond DR or below MDH/MDA
unless you are visual with the
destination.
Single pilot operations
The MDH/MDA for a single-pilot
ARA shall be 100 ft higher than the
above—DR is not less than 1 nm.
An ARA to a rig or vessel under way
is only permitted for multi-crew.
Heliport Minima for VFR/IFR,
Onshore/Overwater
When VFR, if you are slow enough
to see other traffic and obstacles in
time, that is, get a 1 minute visual
reference ahead at 120 knots, the
inflight visibility should be at least 2
nm. Out of sight of land, flight
visibility must be at least 1500 m
during daylight and 5 km by night.
VFR En-Route Minima
Helicopters
On land, helicopters should have a
minimum cloud-base of 600 feet agl
(1500 feet at night) and 1000m
visibility (3 km). In reduced visibility,
adjust your airspeed to maintain a 1-
minute visual reference ahead, e.g. at
120 knots, the inflight visibility
should be at least 2 nm. A US Army
study indicates that it takes about 5
seconds to perceive a problem, make
a decision and start a correction. At
80 kts TAS, therefore, you will move
676 feet and get still closer as you
turn away from an obstacle, the
distance being equal to the radius of
the turn which, in this case, would
be 984 feet, assuming 30 degrees of
bank, giving you a total distance of
1660 feet to cope with, which is not
good if your visibility is only 1000
feet! So, in bad weather, slow down,
certainly enough to give you a 2-
minute visual reference.
Flying VMC on top of cloud is not
allowed because performance rules
require that, if an engine fails, you
must remain in sight of the surface,
and be able to carry out a safe forced
landing, but in twins it may be
undertaken by non-Instrument
　
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