“without the ADS-B trial at North Weald it was unlikely that the AGO would have seen the Quik early enough to provide Traffic Information”

On 2nd August 2019, the ADS-B Traffic Display provided to North Weald airfield as part of the Airspace4All GA Airfield ATS ADS-B Traffic Display Trial showed its worth when it played a part in helping to avoid a mid-air collision.

UK Airprox Board “members quickly agreed that the call from the [North Weald] AGO had successfully enabled the C150 pilot to take timely and effective avoiding action, which ensured that there had been no risk of collision”. The AGO and the pilot had reviewed the incident on the video recording of the ADS-B Traffic Display and agreed to raise the airprox report.

Extracts from the UK Airprox Board report 2019220:

Members agreed that the incident reinforced the need for vigilance, even when in the visual circuit, because without the ADS-B trial at North Weald it was unlikely that the AGO would have seen the Quik early enough to provide Traffic Information.

THE NORTH WEALD A/GO reports that he was keeping an eye on the ADS-B Traffic Display as part of an Airspace4all trial, ensuring that the equipment was working as it should. There were several training aircraft in the circuit, all with ADS-B SkyEcho equipment on board. During the C150’s climb-out he happened to look over at the display and noticed that there was ADS-B traffic approaching from the west, indicating 100ft above the circuit height (1200ft QNH). In line with the AIC document that was published as part of the trial, he gave Traffic information to the C150 pilot informing him that there was ADS-B traffic approaching from the west not on frequency. The instructor confirmed that he was looking, but was not visual. The AGO proceeded to give a position report in relation to known local reference points. As the C150 climbed into the crosswind leg of the circuit and reached circuit height (indicated 1300’ QNH on ADS-B TD) he became visual with the unknown traffic at a range of estimated 300m. The instructor took avoiding action by commencing a level right turn towards the southern boundary of

Stansted CTA which is located approximately 1.5nm north of North Weald Airfield. Once clear of the conflicting traffic, the C150 continued their circuit detail without further issues. The Traffic Display shows the registration, type, speed, altitude and squawk. After finishing his radio operator duties he downloaded the screen recording onto a memory stick and went to see the instructor to see if the recording matched their view. They discussed what options were available and agreed that an Airprox report would be suitable as there is no ATZ at North Weald.

 

PART B: SUMMARY OF THE BOARD’S DISCUSSIONS

For his part, the C150 pilot received Traffic Information from the AGO and stopped his climb accordingly. He then saw the Quik and took avoiding action, ensuring adequate separation. Members agreed that the incident reinforced the need for vigilance, even when in the visual circuit, because without the ADS-B trial at North Weald it was unlikely that the AGO would have seen the Quik early enough to provide Traffic Information.

Finally, the Board turned to the actions of the AGO. He was keeping an eye on the ADS-B receiver in the Tower and saw the unknown aircraft (the Quik) approaching at a similar level to the circuit traffic. He gave timely Traffic Information to the C150 and enabled the pilot to see it and the Board thought that he had done well to do so having seen a developing safety situation.

In assessing the risk associated with the Airprox, members quickly agreed that the call from the AGO had successfully enabled the C150 pilot to take timely and effective avoiding action, which ensured that there had been no risk of collision; risk Category C.

 

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