Virgin Australia A332 at Perth on Nov 26th 2014, lightning strike at the gate
Last Update: March 9, 2017 / 14:20:01 GMT/Zulu time
Australia's Transportation Safety Board reported on Dec 2nd 2014, that the ground worker was injured as result of the lightning strike and opened an investigation.
On Mar 9th 2017 the ATSB released their final report concluding the probable causes of the accident were:
- In combination, perceived operational pressure by the Ramp Supervisor, and their assessment that there would be a 45-minute break in thunderstorm activity, influenced the decision to resume work on the ramp during local thunderstorm activity.
- Consistent with the observed lightning strike to the tail of the aircraft, connection of the headset to the aircraft during local thunderstorm activity resulted in a ‘contact’ strike to the ramp supervisor.
Other factors that increased risk
- The Automated Thunderstorm Alerting System and Global Positioning and Tracking System data did not show cloud-to-ground lightning activity within 10 NM (19 km) of the airport prior to work resuming on the tarmac or at the time of the injuries. Despite the observed local conditions, the lack of recorded ground strikes prior to the incident may have created a false impression of a low lightning risk environment.
- The Virgin Australia Airlines Pty Ltd Meteorological Officer report of no lightning activity in the area in the previous 30 minutes was communicated to the Ramp Supervisor by the Operations Controller. That and the subsequent communication by the Airport Movement Coordinator was perceived by the Ramp Supervisor as pressure to resume ramp duties.
- The Ramp Supervisor’s assessment that there would be a 45-minute break in thunderstorm activity was reinforced by the report by the Operations Controller of no lightning activity in the area in the preceding 30 minutes, and the supervisor’s perception of a reduction in local storm activity.
The ATSB rorted the aircraft had landed and had been holding short of the gate for about an hour due to severe thunderstorm activity in the area. The aircraft subsequently continued taxi to the gate. After arriving at the gate the ramp supervisor connected his head set with the aircraft to communicate to the flight crew. At about that time another ground worker observed a lightning hit the tail of the aircraft, the ramp supervisor became unconscious as result of the electrical discharge, a second ground worker was also affected by the lightning discharge but remained conscious. Both ground workers were taken to a hospital. The aircraft did not sustain any apparent damage.
The airport's lightning detection system was working within its specifications, it had not detected any lightning strike up to the accident.
The ATSB described the sequence of events:
At about 1435 Western Standard Time,1 due to an electrical storm at Perth Airport, all work on the ramp stopped. At about 1515, no further lightning activity was observed on the weather radar, so the ground crew resumed their duties. However, shortly after, cloud-to-cloud lightning was observed and lightning struck the ramp behind an aircraft. All work activities immediately ceased again. The Ramp Supervisor (RS) reported continually monitoring the local conditions from that time to determine when it would be safe for staff to resume work on the ramp.
The captain reported that, on approach into Perth, the aircraft descended through cloud and that they became visual between 4,000–5,000 ft above ground level with small storm cells and lightning activity observed to the north of the airport. The captain recalled landing on runway 06 shortly after 1615 and, during the landing roll, seeing lightning strike the ground about 500 m to the right of the aircraft. The flight crew were advised by air traffic control to hold on the taxiway as the ramp was closed and their designated bay (20A) was occupied.
At about 1630, the Airport Movement Coordinator advised the RS they had been contacted by Virgin’s operations controller located in Brisbane, who queried why duties on the ramp had not recommenced, as other airlines had already resumed their Perth operations. The RS called the Operations Controller and was questioned directly as to why they had not returned to the ramp. During this conversation, the RS was told of advice from Virgin’s Meteorological Officer that there had not been any lightning activity in the area for the past 30 minutes. In response, the RS relayed that lightning was still visible overhead, and was told to discuss this with Virgin’s Meteorological Officer. After being unsuccessfully transferred to the Meteorological Officer’s phone, the RS hung up and reviewed the Bureau of Meteorology weather radar images.
After assessing the weather radar images, the RS determined that there could shortly be about a 45-minute break in the storm cell activity in the area. The Airport Movement Coordinator received a number of additional calls from the Operations Controller about the resumption of ramp duties, which were relayed to the RS. Following a discussion with other senior ground crew, and observing a reduction in the local storm activity, the RS decided to resume work on the ramp. The RS gave priority to clearing the backlog of aircraft waiting to be unloaded, then directed ground crew to move the aircraft already at bay 20A to nearby ‘stand-off’ bay 915 (Figure 1).
At about 1717, the crew of XFJ taxied to bay 20A. After they came to a stop, the RS chocked the nose wheels and connected a headset to the intercom jack at the aircraft’s nose landing gear (Figure 2).
As the ground crew were parking the other aircraft on bay 915, lightning was observed to strike the tail region of XFJ. Simultaneously, engineers located at bay 20A reported observing a lightning flash to the rear-left of XFJ. As the RS depressed the ‘push-to-talk’ button and established contact with the flight crew, the RS received an electrical shock consistent with a high voltage electrical discharge.
The RS staggered from the aircraft before collapsing unconscious on the ground. A second ground crew member assigned to XFJ was also subjected to the electrical discharge and sustained a burn injury. That ground crew member did not lose consciousness.
Both ground crew were transported to hospital for observation. The second injured ground crew member was released the next day and the RS remained in hospital for a number of days before being released.
Inspection of the aircraft by Virgin did not find any evidence of the lightning strike entry or exit points, nor were any defects found that could account for the injuries sustained by the ground crew.
With respect to workload and operational pressure the ATSB analysed:
At the first sign of lightning near the ramp (at about 1515), the RS ceased work activities and withdrew the ground-handling staff. At about 1630, the Aircraft Movement Coordinator and Operations Controller questioned why the RS had not recommenced work on the ramp as the meteorological information provided showed no lightning activity since about 1600. At that time, work had ceased for over an hour and there were partially-unloaded aircraft that had landed just prior to the lightning activity.
The Operations Controller re-enforced that the aircraft needed to be unloaded and dispatched, as they were required on the ‘east coast’ that night. As a result, the RS reviewed the radar data on the BoM website before directing the ground handlers to resume ramp duties.
The RS stated that had he not felt pressured by the Operations Controller and Aircraft Movement Coordinator, he would most likely not have resumed work on the ramp at that time.
With respect to the location of the lightning strike the ATSB analysed:
The lack of an identifiable lightning strike entry or exit point on XFJ could be attributed to the integrity of the aircraft’s electrical bonding and that ground discharge occurred through the headset and ramp supervisor (RS). However, a lightning strike to the ground adjacent to the aircraft, rather than to the aircraft itself, would also account for the absence of lightning damage to the aircraft.
The ground staff on bay 915 reported seeing lightning strike the tail of XFJ. The presence of lightning was further supported by the flash at the rear-left of the tail of the aircraft as reported by the engineers on bay 20A.
The ATSB considered which of a lightning strike to the tail or to the nearby ground was more likely. In this regard, a lightning ground strike would result in radial discharge from the point of strike as shown in Figure 7 (see below).
Had a ground strike occurred at the near-rear of the aircraft, and discharged outward toward the location of the RS and second ground crew member at the nose wheel, it would have also radiated approximately the same distance behind and to the sides of the aircraft. Given the lack of reported lightning injuries/effects to other ground crew working in those areas, a ground strike is considered less likely than a tail strike.
With respect to lightning monitoring and the decision to resume work the ATSB analysed:
Virgin’s Brisbane-based Meteorological Officer had access to Bureau of Meteorology weather data and was monitoring the weather at Perth Airport. Specific to lightning activity, they had access to the Automated Thunderstorm Alerting System (ATSAS) and the Global Positioning and Tracking System data. Neither system showed ground strikes at the airport prior to or during the occurrence. The absence of lightning activity in that data, which was briefed to the Operations Controller by the Virgin Meteorological Officer, was a significant factor influencing the controller to discuss the resumption of work on the ramp with the RS.
The ATSAS and Global Positioning and Tracking system provided a high level of accuracy in the detection of cloud-to-ground lightning strikes (reported as up to 90 per cent accuracy). However, the absence of detection by either system in this occurrence supports the need to source collaborative local data when determining whether it is safe to return to work activities.
The RS attempted to clarify the lightning risk after the Operations Controller called to advise that no lightning activity was recorded in the area for the last 30 minutes, and that other operators had resumed tarmac operations. This entailed the RS attempting to telephone the Brisbane-based Meteorological Officer to discuss the disparity in the controller’s advice as compared to the lighting still being observed overhead. The RS was unable to contact the Meteorological Officer.
Consistent with the reported perception by the RS of pressure from the Operations Controller and Airport Movement Coordinator to resume work earlier than they would have liked, the RS used the Bureau of Meteorology website’s weather radar information to assess the local conditions and estimate the storm’s movement. The weather radar displayed areas of precipitation, but did not directly show cloud formation, thunderstorm or lightning strike activity. Therefore, the weather radar alone did not provide sufficient information to predict lightning strikes. Additionally, the use and interpretation of weather radar information without formal training increased the likelihood that the RS was not aware of this limitation.
In the event, the RS’s decision to resume tarmac activities was informed by their interpretation of the radar data accessed on the Bureau of Meteorology website. This interpretation was reinforced by the report from the Operations Controller of no lightning activity in the area in the preceding 30 minutes, and by the supervisor’s perception of a reduction in local storm activity.
A review of weather radar images for the period leading up to the incident indicated ongoing rain in the vicinity of the airport (Figure 5). The data did not show a clear break in the storm.
YPPH 261100Z 05009KT 9999 -RA FEW090 BKN110 20/17 Q1011 INTER 1100/1400 VRB25G45KT 4000 TSRA SCT040 FEW100CB FM1200 MOD TURB BLW 3000FT
YPPH 261030Z 09017G27KT 9999 -TSRA FEW060 OVC110 FEW110CB 20/17 Q1010 TEMPO 1030/1100 VRB25G45KT 4000 TSRA SCT040 SCT090CB INTER 1100/1330 VRB25G45KT 4000 TSRA
YPPH 261000Z 09012KT 9999 -TSRA FEW060 OVC110 FEW110CB 20/17 Q1010 TEMPO 1000/1100 VRB25G45KT 4000 TSRA SCT040 SCT090CB INTER 1100/1300 VRB25G45KT 4000 TSRA SCT
YPPH 260930Z 08014G28KT 9999 -TSRA SCT040 OVC110 SCT110CB 20/17 Q1010 RETS TEMPO 0930/1100 VRB25G45KT 4000 TSRA SCT040 SCT090CB INTER 1100/1230 VRB25G45KT 4000
YPPH 260921Z 09016G28KT 9999 TSRA SCT040 OVC090 SCT090CB 20/17 Q1010 TEMPO 0921/1100 VRB25G45KT 4000 TSRA BKN050 SCT090CB INTER 1100/1221 VRB25G45KT 4000 TSRA S
YPPH 260900Z 08017KT 9999 TSRA SCT045 OVC090 SCT090CB 20/17 Q1010 TEMPO 0900/1100 VRB25G45KT 4000 TSRA BKN050 SCT090CB INTER 1100/1200 VRB25G45KT 4000 TSRA SCT0
YPPH 260830Z 07016KT 9999 -TSRA BKN070 BKN100CB 21/18 Q1010 TEMPO 0830/1100 VRB25G45KT 4000 TSGR BKN070 SCT100CB INTER 1100/1130 VRB25G45KT 4000 TSRA SCT070 FEW
YPPH 260811Z 05015KT 9999 -TSRA SCT040 BKN100CB 23/16 Q1010 TEMPO 0811/1100 VRB25G45KT 4000 TSGR BKN070 SCT100CB
YPPH 260800Z 01009KT 9999 -TSRA FEW070 BKN100CB 23/16 Q1009 TEMPO 0800/1100 VRB25G45KT 2000 TSGR BKN070 SCT100CB
YPPH 260757Z 36011KT 9999 -TSRA FEW070 BKN100CB 23/16 Q1009 TEMPO 0757/1057 VRB25G45KT 2000 TSGR BKN070 SCT100CB
YPPH 260730Z 11012KT 9999 -TSRA FEW090 BKN110CB 25/13 Q1007 TEMPO 0730/1030 VRB25G45KT 2000 TSGR BKN070 SCT100CB
YPPH 260725Z 12013KT 9999 TS FEW080 BKN120CB 25/14 Q1007 TEMPO 0725/1025 VRB25G45KT 2000 TSGR BKN070 SCT100CB
YPPH 260707Z 13022G32KT 9999 VCTS FEW070 BKN120 FEW110CB 24/15 Q1006 TEMPO 0707/0900 VRB25G45KT 2000 TSGR BKN070 SCT100CB INTER 0900/1007 VRB25G45KT 3000 TSRA B
YPPH 260700Z 13025KT 9999 VCTS FEW070 BKN120 FEW110CB 24/16 Q1006 TEMPO 0700/0900 VRB25G45KT 2000 TSGR BKN070 SCT100CB INTER 0900/1000 VRB25G45KT 3000 TSRA BKN070 FEW100CB
YPPH 260644Z 14015KT 9999 -TSRA FEW070 BKN110CB 24/17 Q1007 TEMPO 0644/0900 VRB25G45KT 2000 TSGR BKN070 SCT100CB
YPPH 260630Z 20007KT 9999 -TSRA SCT070 BKN110CB 24/17 Q1009 TEMPO 0630/0900 VRB25G45KT 2000 TSGR BKN070 SCT100CB
YPPH 260600Z 14008KT 9999 -TSRA FEW030 BKN110CB 25/16 Q1008
This article is published under license from Avherald.com. © of text by Avherald.com.
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