Transcript Air Navigation_Part 5 - 2008 (Bawtry) Air Cadets

AIR NAVIGATION
Part 5
Weather
LEARNING OUTCOMES
On completion of this unit, you should:
– Be able to carry out calculations to
determine aircraft distance, speed and time
– Understand the principles of vectors and the
triangle of velocities to establish an aircraft’s
track and ground speed
LEARNING OUTCOMES
– Understand the principles of the 1 in 60 rule
– Understand the types of compass systems
used for air navigation, how they work and
their limitations
– Know the hazards that weather presents to
aviation
Weather
Introduction
You will have previously studied the weather
as it relates to walking in the hills.
Icing weather
is a far more
seriousaircraft
It is the same
that affects
problem
an one
aircraft
than
it is for
operations
butfor
with
major
difference
a walker
Meteorological Conditions
Simple aircraft such as
basic trainers are not
equipped with
The student
pilot does
instruments
to not
have
thethem
experience
to fly
fly
enable
to safely
ininfog
or cloud.
cloud
or fog
Meteorological Conditions
Consequently, it is
necessary to define the
weather
conditions
in which
These
are called
beginners may fly.
Visual Met Conditions
a simplified version of
the rules are set out in
VMC
the following
table
ABOVE 3000’
Visibility - 8 KM
distance FROM
cloud:
1000’ vertically
1500m horizontally
BELOW 3000’
Visibility - 5 KM
distance FROM
cloud:
1000’ vertically
1500m horizontally
NB AIRCRAFT FLYING BELOW
140 KTS AND IN SIGHT OF THE
GROUND MAY USE KM
VISIBILITY AND MERELY KEEP
CLEAR OF THE CLOUD
It follows that if an
aircraft flies in weather
worse than shown in the
table, it must have the
necessary instruments
to fly in or near to cloud
or in poor visibility.
This weather is known as
Instrument Met Conditions
Only aircraft with
suitable
IMC
equipment and
pilots with suitable
instrument ratings may
fly in IMC
The Visual Circuit
In the early stages of flying, a
achieve
trainee pilotTowill
not want to lose
is needed
sight this,
of theVMC
runway
when flying
and
normally
the takecircuits in
order
to practice
aerodrome
controller
offs and landings
will decide if the
weather is good enough
If the circuit height is 1000’ then the lowest
cloud base will need to be above this
(usually 1500’)
and the visibility will need to be good enough
to be able to see the runway from anywhere
in the circuit
(usually 5 km)
THE VISUAL CIRCUIT 2
1500’ CLOUDBASE
5 KM VISIBILITY
26
Surface Wind
We have already looked at the
effects of wind & drift, when
transiting from A- B.
On the airfield we must also note the
effect of surface wind.
Surface Wind
If conditions are not completely calm, we need
to know the wind direction & strength, so we
take off & land into the wind
You hopefully will remember that takeoffs
& landings into the wind are shorter !
Wind Component
Normally
the
wind
will blow
partly
across
It
is
very
rare
to
find
the
wind
blowing
To find this you can draw a vector, use a
the runway,
so we
needthe
to runway
calculate cross
exactly
along
table or a simple mental method, as we shall
wind & headwind
see.
(even thought runway directions are
chosen along the line of the prevailing
wind)
THE VECTOR
60
Angle Off
TAKE OFF
SURFACE WIND
130/20 KNOTS
40
50
CROSSWIND
COMPONENT
13 KNOTS
27
HEAD
WIND
15 KNOTS
90°- Angle Off =
Angle between wind direction & runway heading for crosswind
component
THE TABLE
This is a
standard
table to
enable you
to work out
the wind
component
10
W
i
n
d
s
p
e
e
d
i
n
K
n
o
t
s
20
30
40
50
60
70
80
90
5
5
1
2
2
3
4
4
4
5
10
2
3
5
6
7
8
9
9 10
15
3
5
7
9
11 13 14 14 15
20
3
7
10 13 15 17 18 19 20
25
4
8
12 16 19 22 23 24 25
30
5
10 15 19 23 26 28 29 30
Note: these angles
are from the vector
triangle shown
minus angle off
80
70
60
50
40
30
20
10
0
For headwind component - Angle between wind direction and
runway heading
To use the table you need the
angle between the runway
heading & the wind direction
(angle off)
If it is 40 degrees you obtain the crosswind
component you use the top row of angles, find
the 40 degree column, & follow it until you get
to the windspeed, in this case 20 knots.
This gives
the cross
wind
component
as 13 knots
Angle between wind direction & runway heading for crosswind
component
10
W
i
n
d
s
p
e
e
d
i
n
You use the bottom
angles if you know the
headwind
K
n
o
t
s
20
30
40
40
50
60
70
80
90
5
1
2
2
3 4
4 4
5 5
10
2
3
5
6
7
8
9 10
15
3
5
7
9
11 13 14 14 15
20
20
3
7
10 13 15 17 18 19 20
25
4
8
12 16 19 22 23 24 25
30
5 10 15 19 23 26 28 29 30
Note: these angles
are from the vector
triangle shown
minus angle off
9
80
70
60
50
40
30
20
10
0
For headwind component - Angle between wind direction and
runway heading
The Quick Method
ANGLE BETWEEN WIND
DIRECTION AND RUNWAY
This is somewhat
easier
&
and
definitely
quicker
HEADING FOR CROSS WIND
COMPONENT
DEGREES
0-15
15-30
30-45
45-60
60-90
ZERO
1/4 WIND STRENGTH
1/2 WIND STRENGTH
3/4 WINDSTRENGHT
FULL WIND STRENGTH
Shallow Fog
As fog starts to form in the early evening,
However once in the approach on the
there is often a shallow layer, a few feet
glide slope the fog will appear to be
thick, next to the ground.
much thicker, & prevent the aircraft from
landing
thecircuit,
runway
or light will
A pilot inasthe
especially
at no
be visible.
night maylonger
not even
notice this as
the ground & lights are clearly
visible
Shallow Fog
This slant visibility can be measured & if
800 visual
METRES?range
ABORT!( RVR ) is under
the UNDER
runway
800 metres a safe landing is unlikely.
Precipitation
It causes the following problems:
This is a fancy word for rain!
Leaks
into
aircraft
on
the
ground
Covers
rain,
sleet,
snow,
Once a fluid has frozen on thehail
airframe
etc with de icing fluid
it must be removed
Floods runways
If it is frozen it can stick to the
airframe and cause takeoff
problems
Airborne Hazards
Apart from thunderstorms, the main
hazard is ice
Even in VMC icing can form on an
airframe at certain temperatures.
TEMPERATURE
ICE !
This can be fatal, but why ?
In a car the main problem
on a frosty morning is the
frozen windscreen
In an aircraft this is easily
cured by heating the
windscreen.
But you cannot heat the whole of the airframe
So the ice will stick to the surface.
On the wings this means the shape of the
wing changes & will eventually cease to be
an aerofoil
Ice on leading edge
WING
However this is not all. As the ice
gathers on the airframe the weight
increases
This means that lift will be decreasing,
& eventually the aircraft will fly like a
brick
Icing can also affect other aspects of the
aircrafts operations, such as undercarriages,
controls surfaces, and radio aerials
It will also affect engine operation, so
the best advice is to stay away from
icing