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US: UPDATED - Pilot of crashed 777 first says he was blinded by a light; then retracts any vision effects

The pilot of the Asiana Airlines flight that crashed July 6 2013 on approach to San Francisco International Airport, told U.S. investigators that he was temporarily blinded by a bright light when 500 feet above the ground (approximately 34 seconds before impact). The Boeing 777 aircraft crashed at 11:28 am local (PDT) time. Thus, it was daylight when the bright light flash occurred.

During a press conference on July 10, the chair of the National Transportation Safety Board revealed the pilot’s statement. Deborah Hersman was asked specifically if it could have been a laser pointed from the ground. She replied “We really don’t know at this point what it could have been. We need to look into it. We need to understand what he’s talking about. We may need to follow up with him.”

Hersman described the flash as only “a temporary issue”, according to the San Francisco Chronicle.

From USA Today (initial story; story about laser hazards), SFGate, and ABC News.

UPDATED July 11 2013: NTSB chair Deborah Hersman gave additional details indicating that the light was not a laser and did not interfere with the pilot’s vision.

Hersman said at a July 11 media briefing that the pilot flying “observed a bright point source of light that could have been a reflection of the sun but he wasn’t sure. The light source was straight in front of the airplane but not on the runway. He briefly looked away from the light and then he looked into the cockpit. And he stated that he did not think that the light affected his vision because he could see the flight control instruments and he was able to look at the speed tape at that time. Neither of the other two flight crew members mention this light during their interviews with our investigators, and in the review of the Cockpit Voice Recorder there is no discussion on the CVR of the light or of the flying pilot seeing a light.”

She continued,”Investigators will determine the relative position of the sun at the time of the landing to help identify any possible sources of momentary reflection that could have been in his field of view…. So to recap, the flying pilot stated … that he did not believe that it affected his vision and he was able to see the cockpit instruments.”

Hersman told NBC Bay Area in a July 11 interview that the flash was not a laser.

Updated info from USA Today, InsideBayArea and NBC Bay Area.

Analysis from LaserPointerSafety.com

[The section below was prepared after the initial report of a flash of light, but before the NTSB chair said it was not caused by a laser. We are leaving this section here for background information.]

Based on FAA records and reports of laser events, a daytime lasing of an aircraft would be extremely rare. At LaserPointerSafety.com we have seen only one news report of a laser aimed at aircraft during daylight hours, and this might have been due to a news reporter misreading the time listed on a police report.

Time of day - 2009 FAA presentation
In 2009, the FAA presented the above chart showing the percentage of laser incidents reported to FAA, versus the time of day. The chart does show some daytime incident reports; however, less than 1% of incidents took place during the 11:00 am to noon timeframe of the Asiana crash. (It is not known how many total laser incidents were analyzed for this chart.)

Is daytime visual interference likely?

Laser/aviation safety experts have long been concerned about low-light and nighttime laser pointer illuminations of aircraft during critical phases of flight such as landing, takeoff, and emergency maneuvers. This is primarily because of the visual effects that bright laser light can cause: temporary flashblindness, glare, task disruption, and distraction.

At cruise altitude there is plenty of time to recover from visual interference. But at critical times-- especially when other factors are going wrong -- laser interference could be the proverbial “straw that broke the camel’s back.”

Daytime visual disruption may be possible depending on the power of a laser. But to the best of LaserPointerSafety.com's knowledge, laser/aviation safety experts have not studied this, and have only focused on low-light and nighttime visual disruption.

One reason is that pilots' pupils are smaller when exposed to daytime light levels, which reduces the amount of laser light that can enter the eye. In addition, there is no loss of night vision as is sometimes seen after nighttime laser "hits".

Daytime aiming

One factor working against a daytime laser “hit” is the difficulty of aiming the beam during daytime. At night, it is usually easy for the person aiming a laser to see the beam. If the beam hits the aircraft, a bright “dot” could be seen depending on the surface reflectivity, reflection angle and other factors.

During daylight however, a person with a handheld laser would be aiming blind. They can point the laser in the direction of the aircraft, but it would be a guess as to where exactly the beam is going. We are not aware of any consumer lasers that have sights.

A rifle-mounted laser could conceivably be used, in which case the weapon’s sight may be helpful in aiming (assuming it is adjusted for the laser dot and not for bullet windage, gravity, etc.). But this is not likely based on the vast majority of lasers which have been recovered from perpetrators -- almost all are handheld, pointer-style lasers.

Would eye injuries be likely, or detectable after the fact?

Laser/aviation safety experts are primarily concerned with visual interference. They are less worried about lasers causing eye injuries to pilots. This is due to a variety of factors such as the beam spreading out over long distances, and relative movement of the handheld laser and the aircraft. The U.S. FAA and U.K. CAA both have reported no permanent eye injuries in any of the over 16,000 reported laser/aircraft incidents.

In the Asiana Airlines case, if a laser was aimed at the pilot, it is highly unlikely that there would be any discernible effect on the pilot's eye. If a visible-light laser was powerful enough to cause injury, the pilot would have immediately had symptoms such as pain or spots that would not fade. But if the pilot has not complained about this until days after the event, it is unlikely that there would be any physical change or indication of laser injury to the eye that could independently confirm the pilot’s account.

In 2011, out of 3,591 laser incidents reported to the FAA, there were 55 cases of eye effects (1.5% of reports). This included 31 cases of pain or discomfort, and 31 cases of vision impairment. (This totals more than 55 due to multiple symptoms in a single incident.)

Of the 31 vision impairment reports, there were 10 cases of flashblinding/afterimage, 5 cases of blind spots, 8 cases of temporary vision impairment, 7 cases of blurry vision, and 1 case of loss of night vision. All of these occurred during low-light levels or nighttime. There were no cases of serious or permanent eye damage or injury.

Color of the light

As of this writing, mid-day July 11, there have been no reports of the color of the bright light that the Asiana pilot saw. But the color could be an important factor.

If the light were a single color, especially green, this would tend to indicate a laser. Out of the 3,482 laser sightings reported to FAA in 2012, 94% were green, 1.4% were red and 1.7% were blue.

There are no white-light handheld lasers. So if the pilot reported white light, this is a strong indication that it is not a laser.

However, this is not infallible proof. In 2012, there were 30 laser incidents (0.9%) where a pilot reported seeing white light. It may be that some of these were not lasers (e.g., spotlights), that they were not handheld lasers (e.g., from a laser light show or other source), that the pilots misreported the color due to shock and surprise, or that the light was so bright that color differentiation would be difficult (e.g., bleaching of the retina).