Crossbar (of approach lighting system)
XS Atmospheric
Y
Y Yellow
YCZ Yellow caution zone (runway lighting)
yd Yard(s)
YR Your
Measurements
Air Pressure
Hektopascal (hPa)
Sometimes we also find inch in older instruments
Altitudes
Will be expressed and transmitted in feet
Breaking action
Friction coefficient
This is a part of the permanent snow plan applicable for the international airports. The mean friction coefficient will be indicated for each third for the runway. The breaking action will be measured continuously by the Skiddometer, the Surface-Friction-Tester or Tapley-Meter. All friction coefficients are measured and will be given on the basis of the following
| 0,40 and above | good | Code 5 |
| 0,39 – 0,36 | medium to good | Code 4 |
| 0,35 – 0,30 | medium | Code 3 |
| 0,29 – 0,26 | medium to poor | Code 2 |
| 0,25 and below | poor | Code 1 |
| unreliable | unreliable | Code 0 |
Horizontal velocity
The horizontal velocity will be indictated in nautical miles per hour and expressed in knots
Navigational distances
Nautical mile , NM and tenth of it.
1 nautical mile is equal of circle-minute of a great-circle. 1 NM = 1,852 km.
Runway
The identification of runway is expressed by numbers which indicate the magnetic direction of the runway.
Surface wind
The units of measurement used in flight operation for wind direction and velocity, except for take-off and landing, will be indicated in degrees true and knots.
(This means that wind direction readings given by the control tower for landing or departing aircraft are magnetic.
Time
We use worldwide in air traffic control the united time co-ordinated (UTC)
When transmitting the time, if there is no possibility of confusion, the minutes (two digits) are used only.
Vertikal Velocity
Feet per minute (ft/min)
Visual distances
Will be expressed in Metres or Kilometres
Questions on Chapter 1
1. Select the correct definition for "estimated time of arrival" in respect to IFR flights.
a) The time at which it is estimated that the aircraft will arrive over that designated point defined by reference to navigation aids, from which it is intended, that an instrument approach will be commenced
b) The time at which it is estimated that the aircraft will arrive over the designated point defined by reference to visual aids, from which it is intended, that an approach will be commenced
c) The time at which the aircraft will actually arrive over that designated point defined by reference to navigation aids, from which it is intended, that a visual approach will be commenced
d) In any case that time at which the aircraft will arrive over the aerodrome
2. What does the term "aeronautical station" mean?
a) A station in the aeronautical mobile service located on land or, in certain instances, on board of a ship or on a platform at sea
b) Any station established to exchange radiotelephony communications
c) A station in the aeronautical telecommunication service located on land or on board of an aircraft to exchange radiotelephony communications
d) A station forming part of the aeronautical telecommunication network
3. What does the term "blind transmission" mean?
a) A transmission of information relating to air navigation that is not addressed to a specific station or stations
b) A transmission of messages relating to en-route weather information which may affect the safety of aircraft operations that is not addressed to a specific station or stations
c) A transmission where no reply is required from the receiving station
d) A transmission from one station to another station in circumstances where two-way communication cannot be established but where it is believed that the called station is able to receive the transmission
4. What does the term "broadcast" mean?
a) A radiotelephony transmission from a ground station to aircraft in flight
b) A transmission where no reply is required from the receiving station
c) A transmission containing meteorological and operational information to aircraft engaged in flights over remote and oceanic areas out of range of VHF ground stations
d) A transmission of information relating to air navigation that is not addressed to a specific station or stations
5. What does the term "air-ground communication" mean?
a) Two-way communication between aircraft and stations or locations on the surface of the earth
b) One-way communication from aircraft to stations or locations on the surface of the earth
c) One-way communication from stations or locations on the surface of the earth
d) Any communication from aircraft to ground stations requiring handling by the Aeronautical Fixed Telecommunication Network (AFTN)
6. What does the term "clearance limit" mean?
a) The time of expiry of an air traffic control clearance
b) The time at which an aircraft is given an air traffic control clearance
c) A point to which an aircraft is granted an air traffic control clearance
d) The time after which an air traffic control clearance will be automatically cancelled if the flight has not been commenced
7. What does the term "expected approach time" mean?