Air Navigation Revision Booklet
Chapter 5 Weather
Visual Meteorological conditions (Visual Met Conditions (VMC)) - good visibility and cloud base at least above circuit height (1000ft). The aerodrome controller will decide if VMC conditions are present.
If the weather conditions are worse than VMC then instruments and an instrument rated pilot are required to fly weather worse than VMC are known as Instrument Met Conditions (IMC).
Visual circuit - staying within visible range of the airfield, cloud base of 1500ft and horizontal visible distance of 1.5km.
You want to take off into wind (wind blowing towards the aircraft) as the take off run will be shorter.
Take off downwind is not advised as the take off run will be longer as the wind speed will need to be overcome before reaching take off speed.
You can also have a crosswind which can change the distance that is needed to take off. You need to know how much of a crosswind and how much of a headwind there will be which can be worked out using the angular difference between the runway heading and the wind direction. If the angle between the wind direction and the runway is 60 degrees or more than the crosswind component is the full wind speed e.g. angle between runway and wind direction of 90 degrees and a wind speed of 13kts the cross wind component would be 13kts.
Runway Visual Range - Due to the shallow glide slope when landing shallow fog will appear thicker than it is this slant visibility is called Runway Visual
Range (RVR)
Precipitation - Wet or frozen water that falls from clouds
Icing - Ice can build up on the wings when flying in cold moist air, the ice can change the wing shape so that it does not create as much lift and the ice adds weight which increases drag. The ice will also affect the engine performance.
Earth rotates from east to west as the sun rises in the east and sets in the west.
Chapter 5 Weather - Revision Questions
1. In order to fly in a visual circuit a trainee pilot requires a. No wind b. Good visibility and no cloud in the sky c. Good visibility and no wind

d. Visibility and cloud base conditions to meet the aerodrome controllers requirements
2. In order to fly in instrument met conditions which of the following required a. The correct instrumentation and a suitable pilot instrument rating b. No cloud in the local area c. A clear windscreen canopy d. An instrument rating only
3. Beginners may only fly in good weather conditions. The conditions are called a. Runway visual range b. Instrument Meteorological conditions c. Visual Circuits d. Visual Meteorological conditions
4. A wind is blowing at 90 degrees angle off the runway direction. If the wind speed is 20kts what is the cross wind component. a. 10kts b. 20kts c. 12kts d. 2kts
5. The wind is blowing directly down the length of the runway, what is the cross wind component a. Zero crosswind component b. Equal to half the wind speed c. Equal to 3/4 the wind speed d. Equal to the wind speed
6. Why does an aircraft take off into wind a. To decrease the length of the take off run b. To increase the groundspeed at take off c. To use the full length of the runway d. To take off at a lower airspeed
7. During periods of poor visibility due to fog Air Traffic Control will advise the pilot of the slant visibility along the runway. This visibility is measured carefully and is called a. Glide slope visibility b. Radar visual range c. Runway visual range d. Runway range
8. The runway has a covering of shallow fog. A pilot circling directly overhead sees the runway lights clearly. However on the approach to land he may have great difficulty in seeing some lights, why is this a. Fog is more dense closer to the ground b. Fog will appear thicker when on the glide path because the pilot is looking at a shallower angle c. Runway lights are designed to be seen at high level only

d. The thickest fog always settles at the end of the runway
9. What can be the effects of heavy icing on an aircrafts performance a. It will fly much slower b. There is no adverse effect on the aircraft’s performance c. Loss of aerodynamics and reduced engine performance d. Loss of aerodynamics only
10. What problems can be caused by precipitation at freezing temperatures a. Icing b. Crosswinds c. Fog d. Thunderstorms
11. what effect can icing have on the aerodynamics of an aircraft a. The windscreen may freeze over b. Lift will decrease and weight will increase c. Ice forming on the leading edge of the wing will increase lift d. There will be no adverse effect upon the aerodynamics
12. What problems can be caused by heavy rain a. Restricted visibility and flooded runway b. Heavy snow c. Thunderstorms d. Runway Visual Range
13. Which way does the earth revolve on its axis a. North to South b. West to East c. South to North d. East to West
14.