Safety

Cable
Collisions

Electrical wires and other cables are statistically one of the most significant hazards for helicopter especially for Low Altitude Helicopter Operations (LALT) and may result in fatal accidents. This article presents the EASA animation “Helicopter wire strike avoidance – Wires in the helicopter environment” and develops the good practices introduced in this video that can help you avoid striking cables.

Understand the risks of cable collisions to your operation

Striking wires may have critical consequences: it results in fatalities in approximately 30% of the accidents and up to 60% when operating in Instrument Meteorological Conditions (IMC) or at night. Wire and obstacle strike is one of the top operational causes of fatal Rotorcraft accidents, as rotorcraft fly approximately 90% of their time in LALT operations in the wire environment.

Besides, number of flight hours is not a guarantee for avoiding wires, as most wire strike accidents statistically occur to experienced pilots with more than 2000 flight hours and good knowledge of the area. As reported by numerous accident investigations, even very experienced pilots, to avoid IMC flight conditions and looking for visual contact with the ground, forget to ensure that no wires are in the area.

The video shows an example situation

In the video, a student pilot is on a Visual Flight Rules (VFR) training flight with a flight instructor in a Cabri G2 helicopter. The flight takes place in a mountainous environment in VFR conditions: it is a sunny day with no clouds in sight. The flight instructor advises the trainee to keep flying above 500 ft. in compliance with the Standardised European Rules of the Air (SERA) and to use visual cues and landmarks to help navigating. The trainee asks to have a closer look at a castle over a hill and while ascending to fly over the castle, he becomes blinded by the sunlight.

Inadvertently the helicopter descends below the minimum altitude over the hillside and gets dangerously close to electrical wires ahead. The student pilot is instructed to climb and turn right to avoid striking the wires. Even in Visual Meteorological Conditions (VMC), it might be difficult to see wires in the flight path and collisions with cables are usually critical and lead to fatal accidents. The video mentions two examples of accidents: Airbus AS 350 BA helicopter of 30 July 2015 in Canada and EC 120 of 3 March in Slovakia.

Video

What you can do to reduce the risk of cable collisions

There are a number of things that you can do to help mitigate the risks.

Preparation and planning:

Undergo wire-strike safety training programme including hazards understanding, mission preparation and Crew Resource Management (CRM), and implement wire avoidance flying techniques and procedures in flight.
Understand the risk of wire strikes by taking the necessary precautions especially when flying at low altitude.
Prepare your flight thoroughly and review any known cable installations on the planned flight path. Every year, thousands of new electrical and communication towers and antennas and hundreds or thousands of kilometers of wire are being added - the situation can change from one day to another. Always download the latest version of maps locating wires and other hazards such as natural and artificial obstacles including wind turbines in your flying area. Familiarise yourself with the terrain, navigational charts and obstacles.

Use if possible an aircraft equipped with wire detection and avoidance and wire cutting technologies. Using technology to its maximum benefit requires dedicated training. Note that pilots often turn off cable or terrain audio warnings as these may disturb attention in highly critical maneuvering and exceed mental processing capacity. Detection systems are ineffective when audio warnings are turned off! If you are used to a helicopter equipped with detection systems, the risk can increase when moving to a non-equipped helicopter because you are used to, but won’t receive audio warnings.

During the flight:

Do not fly at low altitude unless necessary for the operation and permitted by the authority in compliance with the Standardised European Rules of the Air (SERA) and Air Operations Rules.
Around 40% of the pilots who hit wires however knew there were there but couldn’t see them. Visibility becomes a huge issue when looking at wires from above. Even when wires are visible from the ground, they are not consistently visible for pilots in the air! At typical flight speed, most wires are hard to see. Maintain situational awareness during the whole flight and ensure there is sufficient clearance from any obstacle on either side of the flight path and at all heights, especially in a mountainous or hilly environment. Stay focused on the flight and avoid distractions!
Invite everyone onboard to look actively for cables, support structures, terrain, obstacles and traffic, especially when the mission requires flying at low altitude.
A higher level reconnaissance is recommended before descending and entering a potentially dangerous wire environment, typically below 500 ft.

Pay maximum attention to the flight path ahead. Scan wide and slow a 70-degree wide field beyond the center, actively looking for wires and indicators that can reveal the presence of wires such as towers, poles and pathways cut out in trees. Expect wires around roads and buildings and towers on hills and hilltops.
In Special Operations (aerial work), Helicopter Medical Services (HEMS) and other critical missions performed at low altitude, external influences like changing wind direction or gust could be highly demanding especially in mountainous areas. Beware also of poor or deteriorating weather and visibility conditions! Flight preparation and anticipation is key. Mission training, CRM and experience gathering are essential for critical missions.
Even the latest version of maps with obstacles locations, is not a guarantee that all obstacles are properly identified. Take into account all types of wires such as transport cables, guy-wires, ski cables, electrical and communication cables, mobile tree cables, cable cars and slack lines. Thin cables are particularly difficult to see and can be hidden by trees and other natural or artificial obstacles.

More info

Robinson helicopter safety notice

Analysis of helicopter occurrence data has identified a number of accidents and incidents where loose items in the cabin have exited the helicopter and contacted the tail rotor. In some cases this has resulted in a complete loss of control of the helicopter. Pilots and crews must ensure that all items in the cabin are securely stowed before take-off, even if operating with all doors fitted. Passengers must be briefed on the dangers of loose items in and around the vicinity of helicopters.