Aircraft Wake Avoidance

Aircraft Wake Avoidance Solution

Wake Watch’s real-time systems enable airport capacity growth with existing infrastructure.

Wake Watch’s Dynamic Wake Avoidance Solution measures and analyzes wake, wind and atmospheric conditions present at an airport to safely optimize runway capacity in real time. Safe optimization of capacity is attained by using real-time measurements to show when the optimum atmospheric conditions can be used to safely maximize capacity such as when no temperature inversion layers are present in higher wind in unstable atmospheres, conditions which minimize the wake vortex lifetime. Current wake separations assume the a wake turbulence encounter is possible at any time of the day. By measuring the critical parameters of the atmosphere in real time such as the head wind, cross wind, turbulence, stability and inversion layer gradients, as assessment of the likely occurrence of short or long lived wake vortices can also be made in real time. When the vortices are short lived such as in higher speed winds and unstable atmospheres when no inversion layers are present, separation can be safely minimized.  Longer lived wake vortices are present in lower speed winds and stable atmospheres at. Wake vortices become especially long lived and can be present in the flight path when inversion layers are present. This Solution gives airports more information to make more informed decisions to be able to  increase runway capacity when it is safe to do so. How it works
    1. Wake Watch’s systems measure the structure of the atmosphere and the wake lifetimes in real time to determine what the current spacing should be.
    2. The real time data from the wind profiler is used to assess the current state of the atmosphere and to then make an assessment of the most likely wake lifetime. The graphic below shows such a wake lifetime assessment. If there is an inversion layer present, which increases wake lifetime, then the likely location for a wake encounter is also shown on the 3 degree glide slope.
    3. This wake estimate graphic trigger points will be optimized further using the data from our wake array. The wake lifetime estimates can be checked against the current actual wake lifetimes below.
    4. The wake lifetime estimates are constantly being updated using the measurements from the wake array ( wake lifetime) and the wind profiler ( wind data and temperature estimates that show the inversion layer heights). When the atmosphere is changeable then the wake lifetime estimates tend to also be variable.

Click on the image below then, Refresh/Ctrl F5 to see the latest wake lifetime and position estimate. When there is no inversion layer then the wakes fall at around 1.6m/s and have short lifetimes so an estimate of the wake position is not relevant. NOT approved for operational use.

The Current warning level is in 5 increments. Level 1 for wake lifetimes < 0.5 minutes. Level 2 for wake lifetimes < 1 minute. Level 3 is for wake lifetimes < 2 minutes. level 4 is for wake lifetimes < 3 minutes and shows the possible wake encounter location on the glide slope. level 5 is for wake lifetimes > 3 minutes and shows the possible wake encounter location on the glide slope. The small box graphic shows the warning levels for the last 40 minutes.

In normal atmospheres when even a moderate amount of turbulence is present aircraft wake vortices fall below the flight path at around 1.5m/s and typically last less than 30 seconds. Sometimes, mostly at night, temperature inversion layers can be present which can cause the wake vortices to rebound ( rather than falling ) and last for many minutes, posing a severe hazard to any aircraft following too closely behind. The temperature inversion layers are the only atmospheric phenomena that cause the aircraft wake vortices to rebound or last longer. A real time wake measurement data graphic of wake vortex measurements is shown below. The ICAO 24 bit aircraft identification number is shown in the bottom annotation together with the aircraft flight number. The wind parameters are also shown there. The graphic below updates every minute, provided that aircraft have recently passed over the wake array. The vertical red line is present when the aircraft passes over the wake array and is caused by the aircraft noise. The recording then runs for 5 minutes before stopping and waiting for the next aircraft. The wind speed is shown for runway 34 departures( Northerly wind) and 16 arrivals (Southerly wind). The 16 arrivals are at a height of 60m above the wake array. Often the vortices are not evident at all such as when the convective activity of the atmosphere or high winds result in the vortices demising rapidly. The dynamic range of the image below is from 1 volts (black) to 200 volts (red) so the image is linear, a range of 46dB. This allows the atmospheric structure and the wake vortices to be easily seen. The current data from the outputs of the 5 wake array sensors located closest to the center line are shown below. This data is updated mostly in close to real time, but at times it also shows historical data when the graphics display is catching up. The graphic of wakes below indicates the direction of the aircraft (arrival, departure) and the ground wind speed at the time. The measurement is triggered if the aircraft is below 430m when it is over the wake array.

Click on the image below then, Refresh/Ctrl F5 to see the latest wake data. The Matlab data being shown here can be slower due to the amount of data to process, the actual data being read from the sensors is generated in real time. Not approved for operational use.

The outputs from 5 vertical wake measurement sensors is shown above. The sensors are located 900m from the 16 runway threshold. The spacing of each sensor from the runway center line  is shown above each receiver in the title blocks. The sensors are located either side of the runway center-line at -32m, -14.5m 3m, 20.5m and 38m. The time scale of the top row of graphics is 300 seconds while the bottom three center graphics have a time scale of 100 seconds and a reduced vertical scale of 100m so that more detail can be seen in the bottom three graphics of the middle three receivers. The top row shows the received signal level from vertical wind gradients while the bottom row contains a measure of all measured wake lifetimes on the left, the middle three show more detail of the wakes measured in row 1, while the right pic shows the last 5 measured wake lifetimes. The vertical red lines are from the aircraft noise when it is directly over the array. Just after the aircraft has passed over the array, the wake vortices can usually be seen (to the right of the aircraft noise). A strong vortex will have a strong wind speed gradient within it and will thus show more red. The lifetime of the vortex is shown in the bottom left and right graphics, the left graphic shows all the measured wake lifetimes since the measurements started, while the bottom right graphic shows the wake lifetimes for the last 5 arrivals, these measurements are fully automated. As the measurement is of vertical wind speed gradients, the horizontal wind speed component is not seen and the measurement shows only turbulence generated by the passing aircraft in low wind, atmospheric structure can also be seen when the atmosphere is more turbulent. In higher wind (above about 3 m/s) there is a lot more interaction of the vortices with the wind resulting in strong vertical gradients and wake rebounds. A positive cross wind component indicates that the wind is from right to left, ie., receiver 6 is upwind and receiver 2 is downwind. Several examples of wake vortex measurements are shown in the report on “Examples of wake vortex measurements.pdf”, the theory of the wake vortex measurements is given in “Vortex Backscatter theoryV11.pdf”, both of these reports are available for download in the Reports section. There are also 2 videos on the reports page that provide a day of wake measurements, the wind profiles for the same time are also available on the reports page. The Wake Watch systems can readily determine when it safe to use MRS between aircraft using the real time wake and real time atmospheric inversion layer detection systems. Below, a temperature inversion layer is present at around 60m, at around 12:13 UTC ( night time in Australia ) a departing A330 sheds a wake vortex which falls to the inversion layer and rebounds lasting at least 5 minutes.