Mountain waves
Today we'll be talking about this dangerous yet beautiful weather phenomena, that appears above mountains in windy conditions
Mountain waves
Reading time: ~5-7 minutes
Air currents moving around and over mountains begin to oscillate due to the irregularities of the terrain. Therefore, flying over mountain ranges can be very turbulent, and for small aircraft, even dangerous.
What's up today?
Chapter 1
Chapter 3
Chapter 4
What are mountain waves
The wavelength and amplitude of the oscillations depends on many factors including the height of the high ground relative to surrounding terrain, the wind speed and the instability of the atmosphere.
Formation of Mountain Waves can occur in the following conditions:
Formation of Mountain Waves can occur in the following conditions:
- Wind direction within 30 degrees of the perpendicular to the ridge of high ground and no change in direction over a significant height band.
- Wind speeds at the crest of the ridge in excess of 15 kts, increasing with height.
- A temperature inversion just above the hill or mountain barrier.
In the end, mountain waves are associated with strong turbulence, strong vertical currents, and icing.
How mountain waves influence the flight
Mountain waves are often associated with strong turbulence, strong vertical currents, and icing. They can thus have a negative impact on the flight.
Loss of Control and / or Level Bust
he vertical currents in the waves can make it difficult for an aircraft to maintain en route altitude leading to level busts and can cause significant fluctuations in airspeed potentially leading, in extremis, to loss of control. Loss of Control can also occur near to the ground prior to landing or after take off with a risk of terrain contact or a hard landing if crew corrective response to a downdraft is not prompt.
Turbulence
Aircraft can suffer structural damage as a result of encountering severe clear air turbulence. In extreme cases this can lead to the break up of the aircraft. In even moderate turbulence, damage can occur to fittings within the aircraft especially as a result of collision with unrestrained items of cargo or passenger luggage. If caught unaware, passengers and crew walking around the aircraft cabin can be injured.
Icing
Severe icing can be experienced within the clouds associated with the wave peaks.
Possible defenses
Mountain waves pose a significant danger, especially for small aircraft and aircraft approaching for landing or taking off. To avoid negative consequences, it is necessary to know how to protect against these effects. In the event of encountering increased turbulence caused by mountain waves, the standard recommendations apply - as with other types of turbulence, it is necessary to increase speed, turn on the "Fasten Seat Belts" sign, and inform the controller about the area.
However, it is even more effective to take preventive measures to avoid entering areas affected by mountain waves:
However, it is even more effective to take preventive measures to avoid entering areas affected by mountain waves:
- Awareness
In the Alps regions, particularly in the Zurich – Milano regions, a general rule of thumb that a QNH difference of more than 5 – 8 mb between LSZH and LIMC, for example, or between north and south of the Alps, will provide for significant mountain wave activity over the Alps. A higher QNH in Zurich will result in mountain waves south of the Alps, for example.
If significant mountain wave activity is expected, as a rule of thumb and if possible plan a flight at least 5000 – 8000 feet above the highest elevation along your route.
- Forecasting
- Cloud Formation
- Restraint Systems
Summary
Mountain waves are not the most dangerous phenomenon in aviation. But for unprepared crews (especially in small aviation), it can pose a significant threat to flight safety. Understanding the physics of the processes, ways of forecasting mountain waves allows pilots to take necessary actions in advance (changing altitude/direction of flight, securing passengers), thereby maintaining both comfort and safety.
In addition to the threats, mountain waves also create very beautiful cloud formations, which you can see in the photos in this article. So, as almost always, nature is simultaneously beautiful and dangerous. But if we are familiar with it, there is a great chance that we can enjoy the views without compromising safety.
Fly safe :)
In addition to the threats, mountain waves also create very beautiful cloud formations, which you can see in the photos in this article. So, as almost always, nature is simultaneously beautiful and dangerous. But if we are familiar with it, there is a great chance that we can enjoy the views without compromising safety.
Fly safe :)
Name of article: Mountain waves
Release date: 11/09/2023
Acrticle author: Nikita Pavlov
Release date: 11/09/2023
Acrticle author: Nikita Pavlov
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