Airprox Serious incident Aéropsatiale AS 332M1 Super Puma T-314, Thursday 26 April 2012

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Date:	Thursday 26 April 2012
Time:	15:20
Type:	Aéropsatiale AS 332M1 Super Puma
Owner/operator:	Swiss Air Force
Registration:	T-314
MSN:	2328
Fatalities:	Fatalities: 0 / Occupants:
Other fatalities:	0
Aircraft damage:	None
Category:	Serious incident
Location:	Alpnach Airport (LSMA) - Switzerland
Phase:	Approach
Nature:	Military
Departure airport:	Alpnach Airport (LSMA)
Destination airport:	Alpnach Airport (LSMA)
Investigating agency:	STSB

Narrative:
A Piper Cheyenne IIIA, registered D-IOSD, was on a flight from Münster-Osnabrück to Buochs. After passing through the Emmen control zone, the pilot contacted Buochs air traffic service approximately five kilometers northwest of Buochs Airfield at an altitude of 7,000 ft QNH. The controller at Buochs then cleared the pilot to enter the right downwind leg for runway 07 at Buochs.

The pilot flew slightly west of Buochs Airfield, then turned south, and later southwest, beginning his descent. Around the same time, a formation of two Swiss Air Force helicopters, AS332 Super Puma, registered T-322 and T-314, was returning from Lucerne to Alpnach Air Base. The controller at Alpnach had cleared the formation to approach via the left downwind leg for runway 01.

Meanwhile, the pilot of D-IOSD had flown around the Stanserhorn mountain from the south, and Alpnach Air Base came into view ahead. Believing he was approaching Buochs, the pilot initiated an approach to runway 01 at Alpnach Air Base. During final approach, the pilot of D-IOSD initiated a go-around.

At that moment, the leader of the helicopter formation was flying slightly west of runway 01, in the left downwind leg heading south, while the wingman was positioned slightly to the left and behind the leader, above the runway. During the go-around maneuver, a dangerous proximity occurred with the helicopter formation: the wingman was overflown by D-IOSD at an altitude approximately 300 ft higher, on a reciprocal course.

The closest separation was 0ft horizontally and 300 ft vertically.

Causes
The serious incident occurred because the pilot of a civilian aircraft confused Buochs Airfield with Alpnach Air Base and conducted an uncoordinated approach there. This led to a dangerous near-collision with a formation of Swiss Air Force helicopters, as the aircraft crossed above the runway on a reciprocal course.

Direct Cause
The pilot had insufficient situational awareness of his aircraft’s position because he had not developed a proper approach plan.

Contributing Systemic Factor
The air traffic control units at Buochs and Alpnach did not have a radar display showing the position of the approaching aircraft.

Accident investigation: