air navigation part 1 distance & speed. recap latitude and longitude lines divide the surface of...
TRANSCRIPT
AIR NAVIGATION
Part 1
Distance & Speed
RECAP
Latitude and Longitude lines divide the surface of the Earth
into degrees and minutes.
One minute of latitude represents one nautical mile (nm)
1 degree of latitude
(60 minutes) equals 60nm
RECAP
Latitude and Longitude lines divide the surface of the Earth
into degrees and minutes.
As a complete circle is 360°
then 360 x 60 gives the circumference of the Earth as 21600 nm
(approx 25000 statute miles).
RECAP
• Lines of Longitude • are sometimes called MERIDIANS
• The line of Latitude must be given first.
• The starting point goes through Greenwich and is referred to as the
• “Prime Meridian”
Distances Between Points
Nautical maps have no scales on the borders, we use the nm scale shown on each meridian.
Distances Between Points
If two places are on the same meridian(longitude)
then it is possible to calculate the distance between them,
rather than having to actually measure it.
Distances Between Points
For example:
Torrejon airfield (in Spain) is due south of RAF St Athan (in Wales) on the same meridian
These two latitudes are N40º29’ and N51º24’
So how do we calculate the distance between them?
Meridian Calculation
First Latitude N 51º 24’
Second Latitude N 40º 29’
Subtracting gives 10º 55’
Remember – 60 degrees to a minute
Because 29’ is more than 24’60’ minus 29’ = 31As we carry 1 across, we now have 51º – 41º = 10º
?
Plus 24’ = 55’
Meridian Calculation
Second Latitude: N 40º 29’
Subtracting gives: 10º 55’
Now convert 10º 55’ into nautical miles:
10º multiply by 60 = 600Add the 55’ = 655 nm
First Latitude N 51º 24’
Aircraft Speed
•What is the measurement of speed •for cars, motorcycles and land vehicles:
– Miles per hour
•For aircraft, the speed is a measure of:
– Nautical Miles per hour – (Knots)•(remember 1’ of latitude is 1 nautical mile (nm))
Aircraft Speed
•What do we use to show the of speed •for cars, motorcycles and land vehicles:
– Speedometer
•For aircraft we use an
•Air Speed Indicator •(ASI)
• The Air Speed Indicator (ASI) measures • the Dynamic Air pressure
• caused by forward motion of the aircraft.
•This is achieved by measuring the air •captured in the Pitot Tube
Aircraft Speed
• The Air Speed Indicator (ASI) measures • the Dynamic Air pressure
• caused by forward motion of the aircraft.
•The pressure of the air •surrounding the aircraft•( “Static Pressure”) •and the air pressure •captured in the Pitot Tube •(“Pitot Pressure”), •are measured and compared.
Aircraft Speed
Pitot Tube
Static Tube
Airstream
A simplified ASI
• The Air Speed Indicator (ASI) measures • the Dynamic Air pressure
• caused by forward motion of the aircraft.
•In forward flight •the pressure above •the diaphragm is both •Dynamic + Static.• •But below the diaphragm is just Static.•
Aircraft Speed
Pitot Tube
Static Tube
Airstream
A simplified ASI
Dynamic + Static
Static
• The Air Speed Indicator (ASI) measures • the Dynamic Air pressure
• caused by forward motion of the aircraft.
• •The two static pressures •cancel each other out, •and so the diaphragm •moves up and down•due only to the •Dynamic Air Pressure.
Aircraft Speed
Pitot Tube
Static Tube
Airstream
Dynamic
Static
A simplified ASI
+ Static
Aircraft Speed• The Air Speed Indicator (ASI) measures
• the Dynamic Air pressure• caused by forward motion of the aircraft.
•The movement due to dynamic pressure •is amplified and displayed on the instrument
•as Indicated Air Speed (IAS) in knots.
Check UnderstandingDistance on the earth’s surfaceis measured in nautical miles.Which of the following is true?
1 nm = 1 min of Latitude
1 nm = 1/10,000 of the distance from the North pole to the equator
1 nm = 1 min of Longitude
1 nm = 5280 feet
Check Understanding
One degree of latitude represents:
1 nm
6 nm
60 nm
360 nm
Check UnderstandingWhat time is used as standard
in military and commercial aviation?
Greenwich Mean Time
The local time of the country flying over
European Standard Time
British Summer Time
Check UnderstandingGlasgow is due north of Plymouth
(approximately on the same meridian).
If Glasgow is latitude 55°50’ and Plymouth is latitude 50°25’
what distance are the two places apart?
525 nm
275 nm
450 nm
325 nm
55° 50’ - 50° 25’
55° – 50° = 5
50’ – 25’ = 25
5 x 60 = 300 300 + 25 = 325nm
Check UnderstandingWhat does an ASI measure?
Forward thrust of the aircraft engines
Dynamic air pressure caused by forward motion of the aircraft
Overall speed of the surrounding air
Dynamic air pressure caused byspeed of the outside air
Check UnderstandingIn the RAF, aircraft speeds are
generally expressed in:
Nautical miles per hour
Miles per hour
Metres per second
Knots
Check UnderstandingWhat is shown on an ASI?
Nautical miles per hour
True Air Speed in knots
Dynamic Air Speed in knots
Indicated Air Speed in knots
AIR NAVIGATION
End of Presentation