Microlighters

Great visualisation of wingtip vortices! Often spoken about, but seldom seen!

On that topic . . . . some good information from http://www.komanetskyaviation.com/Educa ... /index.htm

What wingtip vortices are and how they form is relatively simple to understand.
• The air on top of the wings of an aircraft in flight is at a lower pressure than the surrounding air. This is one of the basics of aerodynamics - Bernoulli's Principle
• The air underneath the wings of an aircraft in flight has a higher pressure than the air above the wings
• This differential air pressure causes the air below to want to take up the area where the reduced air pressure is located above the wings
• The wing tips are really the only place along the wings where this can occur. So, the air below circles around the tip of the wing to meet the air above
• This circling action creates horizontal 'tornadoes' that trail behind the aircraft as the aircraft moves forward
• The air being pushed to the side of the aircraft's fuselage also contributes to the movement of the vortices. They tend to move away from the aircraft and then they follow the wind direction

Operational Tips For Light Aircraft – How to Avoid Vortex Wake:
1. Lift Off Short of Large Aircraft Rotation Point.
2. Land Well Beyond Large Aircraft Touchdown Point.
3. Pass Over Flight Path of Large Aircraft, or At Least 1000' Under.
4. Stay to Windward of Large Aircraft Flight Paths.
5. Keep Alert, Especially on Calm Days When Vortices Persist Longest.

John.com , amazing pic ! Thanks for the explanation

"In level flight, in stable conditions, these vortices descend slowly @ sink rates of 400-500 fpm to stabilise approximately 1000 ft below the aircrafts flight path, remaining there for up to 4 minutes! if the air is unstable, vortices disperse fairly quickly. in Order to avoid the turbulence, a following aircraft should always fly ABOVE the flight path of the aircraft. Vortices are most dangerous to following aircraft during the take-off, initial climb and the final approach phase. When close to the ground they drift sideways from the track of the generating aircraft"

Hope this helps
Chris

Sorry Chris, need to correct a fact on the drifting scenario. If there is a cross wind, yes, the vortices do drift, but only marginally. The friction of the earths surface holds the vortices. It also helps to break them up. So landing close behind another aircraft in a crosswind situation is not safe. The vortices will remain on the downwind side of the runway, catching your downwind wing by surprise:) Always remain above the approach flight path of the aircraft landing ahead of you, and touchdown beyond it's touchdown point.

Another interesting fact is that a standard 450kg microlight, fully loaded, with a standard wing of +- 14.5m2, flying at standard best lift speed of +- 45mph, generates 2.5Metric tonnes per SECOND of wake vortice. That is the value of the force exerted by the swirling air. So, don't be fooled thinking it's only a trike! We may be micro, but out wake is macro! Our wings are very dirty generators of lift. That's why we need 100hp motors to try and fly at 85mph... Very low aspect ratio wings.

Nice chatting.

Regards.