Protecting pilots’ eyes from laser attacks

31 October 2018 (Last Updated October 31st, 2018 13:39)

Laser attacks on pilots, although not new, are growing in frequency and severity around the world. Andrew Tunnicliffe talks to BAE Systems’ Dr Mark Bray about the risks they pose and how technology can help protect pilots’ eyes.

Protecting pilots’ eyes from laser attacks
According to figures from the US Federal Aviation Authority, there were 6,753 laser illuminations reported in 2017. Image: U.S. Air Force/Airman Shawna L. Keyes.

In recent years the number of pilots reporting being distracted by lasers – often during take of or landing – has grown, leading to increased pressure on governments to take more robust action.

It is believed perpetrators are often out to cause mischief, not fully understanding the potential consequences of their actions. However, those consequences can be as serious as temporarily or permanently blinding flight crew, which in itself poses a major risk to life.

According to figures from the US Federal Aviation Authority, there were 6,753 laser illuminations reported in 2017. Thankfully that figure is lower than 2016’s 7,442 and a peak of 7,703 the previous year. However, that peak was a significant rise in the number of incidents reported annually, fewer than 4,000, before 2015.

Laser attacks: a growing threat to pilots

“Lasers may be used to either dazzle a pilot or, at greater powers, actually damage pilots’ eyesight, causing blindness,” explains BEA Systems’ executive scientist and photonics expert Dr Mark Bray.

“Dazzle will cause the eye’s response to change, making it more difficult to see other, less bright, objects. In addition, dazzle will cause the pilot to lose concentration. Laser dazzle is a particular difficulty when the pilot is undertaking a high workload, such as landing or taking off, but is also likely when the aircraft is nearer the ground, making it easier to shine a laser beam.”

The UK Ministry of Defence reported 40 such incidents in 2017, up from the 30 the previous year; although down from their peak in 2014 and 2015. Because of the risks being posed to military aircraft, Kevan Jones, a former UK defence minister, called for police to be given greater resources to catch offenders around military bases.

His concerns are not the first of this kind. In 2015, then arliamentary under-secretary for defence, Mark Lancaster MP, said: “There have been some 470 laser related Defence Air Safety Occurrence Reports received in the last five years involving UK military aircraft. Some 250 occurred in the UK and 220 overseas.”

Laser protection for pilots

Although often thought of as a social and civil concern, military leaders are facing a new and growing threat from emerging laser technology, likely state-backed. In response, the US Coast Guard’s Office of Aviation Forces has worked with the US Air Force’s Vision Science Lab at the Naval Medical Research Unit Dayton to develop better ways of counteracting the threat.

Heading the project are senior research psychologist Dr Michael Reddix and aerospace optometrist Lieutenant Commander Micah Kinney. They explain: “Handheld lasers can produce levels of solar radiant energy that exceed the maximum Federal Aviation Authority exposure recommendations. Non-lethal continuous wave laser exposures can produce veiling glare, obscuring a significant portion of an aircraft windscreen while reliably reducing speed and accuracy of responses to aviation-relevant visual tasks during critical phases of flight. These factors are also capable of producing visual impairments such as temporary scotoma or a temporary disturbance in vision.”

Together they have designed and manufactured what they call a ‘low cost LEP spectacle’ which has been cleared for flight acceptance testing that is currently ongoing.

“Laser eye protection exists in two forms,” explains Bray. “Coloured glass filters centred at the correct wavelength will reduce the laser light transmitted, but also cut out much of the light that the pilot wants to see, like wearing sunglasses indoors. These will reduce the overall light level by too much for a normal pilot.”

Interference filters, he says, are designed to just cut out the wavelengths required. “They have a narrow linewidth, a few nanometres, so most of the normal light is transmitted. It is, however, very angular dependent; if the laser light strikes the filter just off normal it will be transmitted, causing dazzle. The angular performance can be improved by increasing the linewidth of the filter but this in turn cuts out more of the light the pilot needs to see. So there are two competing effects.”

Bray says a lot of work has gone in to developing products that protect pilots from this form of attack; now much of the challenge is about developing the frames to house the filters. BAE has developed a filter that Bray says cuts out all laser power and works at three well known wavelengths simultaneously, whilst providing over 70% normal transmission. He explains that the system has additional features that improve the performance for off axis beams, adding: “The filter is designed to operate at different angles by curving the filter the angular performance is improved.”

A growing international issue

Recently the US Pentagon revealed there had been a growing number of laser related incidents involving its pilots. In the first seven months of this year, forces serving in the Middle East reported more than 350 attacks across Afghanistan, Iraq, and Syria, according to Air Forces Central Command in Qatar.

They coincide with a number of incidents around a US military installation in East Africa, which reportedly injured two crew on a C-130 cargo plane and are said to have originated from a Chinese military base in the region. If true, those attacks appear to be part of a wider Chinese tactic with a dramatic rise in the number of similar incidents reported by US personnel on operations in the East China Sea.

Speaking to CNN in June, a US military spokesperson said there had been 20 incidents since September 2017. Although not directly attributing them to Chinese military personnel, the US suspects they are coming from Chinese fishing vessels, likely the country’s so-called ‘Little Blue Men’, a part-time militia known to work on behalf of the Chinese Government. China has flatly denied the accusations, saying they were “groundless” and accused the US of “making up rumours”.

Of huge concern has been the use of military grade or ‘dazzler’ lasers, particularly in East Africa. This marks a serious change from the previous use of commercially available devices, and poses a far greater threat to military personnel.

Among its known and growing laser arsenal, China has developed a number of low powered laser devices for use by individuals, military and arguably militia, and it’s not afraid to tell us about them. In a report published by Chinese state-owned newspaper Global Times in 2015, the government unveiled four such devices: the BBQ-905 Laser Dazzler Weapon, the PY132A Blinding Laser Weapon, the PY131A Blinding Laser Weapon, and the WJG-2002 Laser Gun, each resembling an assault weapon. In the same year, China’s military newspaper PLA Daily reported: “China has been updating its home-made blinding laser weapons in recent years to meet the needs of different combat operations.”

The rhetoric, and actions, of China mean laser attacks must now be treated as a genuine threat.

Laser eye protection: now and in the future

There have been significant steps taken by military and industry to counter the growing threat posed by laser attack on both military and commercial aircraft. But challenges remain, says Bray.

“Among them are achieving performance for off axis incidence of laser, a high absorption at the wavelength of interest whilst keeping the transmission high elsewhere, and ensuing they work,” he says, “something not easily done given the risk to individuals if they don’t work.”

Although the technology is advanced and will continue to move apace – often led by those intending harm – the biggest challenges can be taken from any manufacturer’s book. They are responsible for ensuring any protective eyewear is up to the wear and tear of a pilot’s role, easily adaptable should laser technology move on quickly, and they can be made at a price that suits everyone’s pocket.