11 / 20

Refer to figure. 
An aircraft is flying from Point A to Point B at the flight level corresponding to the pressure surface of the constant pressure chart. Which of the following statements is correct?

  • A
    The true altitude will be higher over B than over Paris
  • B
    Wind speed over A is higher than over B
  • C
    Wind speed over B is higher than over Paris
  • D
    The true altitude will be higher over B than over A

FEW CONSIDERATIONS:

Firstly, it is important to point out that this is a Contour chart and pressure information is not provided - Pressure is constant everywhere => this shows the True Altitude of a certain pressure level. For example, the 500 hPa level, in ISA conditions, corresponds to FL180. Isohypses will show you whether its true altitude is found at a lower or higher level (due to temperature variations).
Isohypses are are plotted with the reference being MSL and the heights give us an indication of the distance that a pressure level is from MSL. If the contours are high values (wider spaced) then we can assume a high pressure exists. Conversely if the contours are lower values (closely packed) ,then we can assume a low pressure.
Having that established, it is true that roughly the same rules apply as for isobar charts. The closer the contours the stronger the wind.
Circulation of air around a High and Low Pressure system:
In the Northern Hemisphere:
- The air moves anticlockwise around a low pressure centre; and
- Clockwise around a high pressure centre.

In the Southern Hemisphere:
- The air moves clockwise around a low pressure centre; and
- Anticlockwise around a high pressure centre.
With regards to this question,
  • We can see that this question depicts a situation in the Northern Hemisphere, in Paris.
    Now, notice the wind arrow on the lower right side of "A", which indicates that the wind is blowing from a Southerly direction, therefore indicating an anticlockwise direction => which means that both are low pressure areas.
  • The tighter packed Isohypses show lower elevations, wider spaced isohypses show higher elevations => by looking at the isohypses, we can see that the contours at "B" are closer than at "A", therefore true altitude is higher over "A"/Paris than "B".
  • Furthermore, as we have discussed, the contour lines are closer together at "B" than at "A"/Paris so the wind is stronger at "B" than at "A"/Paris

Your Notes (not visible to others)



This question has appeared on the real examination, you can find the related countries below.

  • United Kingdom
    3
  • Austro Control
    2
  • Greece
    2
  • Poland
    2
  • Slovakia
    2
  • Lithuania
    1
  • Spain
    1
Keyboard Shortcut Use Keyboard Shortcuts