+Weather for Fearful Flyers

On a day when you’d have to leave the car in the garage and stay at home … the airlines continue operating, albeit in a limited way. That’s not to say that there aren’t some long delays … of course there are but it takes time to clear a runway of snow, and when it’s foggy planes can’t land as frequently … but they are still flying. Things slow down, but they don’t grind to a halt as they do on the roads. Most importantly, in aviation, everyone is working together to a rigid and enforced set of rules and standards.

Top Tips about weather

A plane cannot land or take off if the visibility or wind is outside legal limits.
A plane cannot make an approach to land if the weather is outside its operating limits.
A plane cannot fly within 25nm of a thunderstorm.

Weather is caused by

the changing states of air. The air in the atmosphere has these changeable properties:

Pressure
Moisture content
Temperature

And here is what these properties cause:

Pressure differences cause wind.
Moisture content determines the type and amount of cloud.
Temperature determines how much moisture is stored by the air.

Remember:

Weather doesn’t affect the way an aircraft flies.
Turbulence may be uncomfortable but is not dangerous.
Aircraft do not drop or plummet thousands of feet because of turbulence.

Anxious flyers are generally interested in four main aspects of the weather, first fog, secondly the wind affecting the take-off and landing, thirdly thunderstorms and of course, turbulence, but that is dealt with elsewhere on this site.

Fog The wind Thunderstorms Snow and ice

Fog is caused when the air contains a lot of moisture and the temperature drops, and the moisture instead of remaining invisible … which it usually is … condenses into water vapour. Fog will clear when the temperature rises to re-absorb the moisture. Sometimes, however, the early morning sun will help to mix the air and actually make the fog thicker for a while. You’d be surprised how little fog affects aircraft operation and modern autopilots systems allow landings in zero-zero conditions. (No visibility) When landing in fog, the pilot confirms that the autopilot is going through the correct sequence until the aircraft touches down All that has to be done then is for the reverse thrust to be applied.

The wind is caused by the difference in pressure between air masses. The air will always move from high to low pressure and that movement we feel as wind. The greater the difference in pressure, the stronger the wind will be. Many fearful flyers believe that the wind has more influence on an aircraft than it really does. On the ground, in a crosswind, the natural tendency for the aircraft is to turn towards the wind direction and as a passenger you may feel the aircraft moving to the left or right slightly as the controls are adjusted to keep to the centre of the runway. When the aircraft is airborne, the wind has no effect other than to influence the direction the plane is traveling in. It does not have any effect on controlling the aircraft or the way it flies. Crosswinds are not difficult for the pilot.

Aircraft are not allowed, by law, to fly into thunderstorms and when passing them must avoid them by at least 25 nautical miles. You may get the impression that you are in a storm because of nearby turbulence and, at night you will see lightning and sometimes you will be in cloud as well. But the weather radar will show the pilots very clearly where any storms are and allow the pilot time to steer around them.

Snow and ice do not an aircraft as much as you would think. All major airports have de-icing facilities available in the form of de-icing trucks or gantries through which the aircraft taxis to have all the ice and snow removed. The runways are cleared and then an accurate report is given to pilots as to the exact depth of snow/ice/water that remains on them. The pilots use special performance criteria which limit the aircraft if the contamination exceeds a certain amount. What this means in practice is that planes will take off at a reduced weight.

Best wishes, Captain Keith

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