Description

On 17 October 2006, at night, in low cloud and poor visibility conditions in the vicinity of Kinloss Airfield UK, a loss of separation event occurred between an RAF Nimrod MR2 aircraft and a civilian AS332L Puma helicopter.

The Nimrod was flying an aerodrome training circuit and was vectored by Approach for an “azimuth-only” approach [no glidepath information - advisory heights are passed with range from touchdown]. When the Nimrod was on short final (2-3nm), the crew executed a go-around as part of the training and the aircraft came in close proximity to a previously departed AS332L helicopter.

Summary of Information Reported to UKAB

The following is an extract from the United Kindgdom Airpox Bard (UKAB) Report 154/06 on the Serious Incident:

"As the Nimrod approached departure end of RW08, the A3701 squawk (the discrete code assigned to AS332L) was directly ahead and slightly below the Nimrod and turned R (right) eventually onto the track of about 170°. The Nimrod was indicating 2200ft Mode C and the Puma was indicating 2000ft Mode C climbing.

The Nimrod was on TALKDOWN position frequency, and was transferred to LOS APP controller shortly before the loss of separation occurred. The departing helicopter was on TWR frequency and was transferred to LOS APP frequency during the loss of separation.

The statement of the LOS APP controller includes:

The crew of the Nimrod called him on UHF shortly before the returns merged and informed him of the ATS required and intentions all in one transmission, which delayed his avoiding instructions by some 3-4 seconds. As result both ac (aircraft) were diverging with less than ½ nm horizontal separation by the time the nimrod pilot was first instructed to make an avoiding action L turn. The Puma pilot then called him on VHF in the climb, but as the ac were now safely diverging no avoiding action was given to the Puma crew. He asked both acs’ crews if they had been visual with each other and both informed him that they had not seen the other ac and that they were in Instrument Meteorological Conditions (IMC) throughout. […]

The statement of the TOWER controller includes:

After the controller passed the departure clearance: […] At the time he believed that the Puma was DOWNWIND, as he had watched it land on and then establish forward flight, this all before he had logged it on the statistics page. But the Puma crew informed him that they had in fact landed back on RW08 and were now well up the runway, E of the overrun cable and close to the upwind threshold. Clearance to depart was given, as it seemed to him that the Nimrod could not have travelled particularly far and the Puma was in fact blocking the runway. […]

Summary of Board’s Discussions

[…] Neither crew was aware of the other’s ac until a very late stage when they had switched to LOS APP. Both crews were in IMC in cloud and neither ac was fitted with TCAS. Furthermore, it was unfortunate that the avoiding action proffered by LOS APP when confronted with these two ac in close proximity was too late to be effective as the crew of the Nimrod called just before the returns merged. It was purely fortuitous that any separation existed at all as each ac turned in opposite directions and both ac climbed. The Board concluded unanimously that a definite risk of collision existed in circumstances conscientiously reported here.

Cause

• The Kinloss TOWER controller cleared the AS332L for take-off into conflict with the Nimrod. Degree of risk: A.

Related Articles

• Loss of Separation - ATCO-induced Situations
• Radar Control - Collision Avoidance Concepts
• Collision Avoidance
• Accident and Serious Incident Reports: LOS

Further Reading

• Analysis of Airprox in UK Airspace - Jul - Dec - 2006 - Report 17 (See AIRPROX Report 154/06, pp 215 - 221), UK Airprox Board