Turbulence/windshear/microburst

On 8 November 2013, the captain and first officer operating a Qantas Boeing 767 aircraft, registered VH-OGU, prepared to conduct a scheduled passenger service from Melbourne, Victoria to Sydney, New South Wales. The crew obtained the relevant weather information, with no requirements for holding fuel or an alternate indicated.

During the descent into Sydney, the crew switched on the seatbelt sign at about 10,000 ft above mean sea level (AMSL). At about the same time, they observed lightning to the right of the aircraft’s track, with a corresponding red return on the aircraft’s weather radar display.

At about 2026 Eastern Daylight-savings Time, while on approach and descending through 4,200 ft AMSL, the aircraft encountered moderate turbulence for about 2 minutes. At about 3,000 ft AMSL, the crew elected to discontinue the approach, and conducted a missed approach. During the subsequent climb, passing about 4,200 ft AMSL, the aircraft encountered severe turbulence.

The crew reported that full go-around power was required to maintain altitude and speed, and they experienced difficulty controlling the aircraft. In the cabin, one passenger sustained a serious injury; one passenger sustained a minor rib injury and a third passenger sustained a minor injury from an iPad.

After orbiting for about 20 minutes, the crew commenced an approach to runway 16 Right. Passing about 5,000 ft AMSL, the aircraft again encountered severe turbulence and was difficult to control, and the crew again conducted a missed approach and commenced a turn to the north.

At about 2127, based on the remaining fuel quantity and the turbulence on the approach to Sydney, the crew declared a ‘PAN’ and elected to divert to Williamtown, New South Wales.  The aircraft landed at Williamtown with fuel reserves intact.

This incident serves as a timely reminder to passengers to safely stow any carry-on baggage, laptops, iPads and other items correctly, as they can become projectiles during turbulence if not properly secured.

Aviation Short Investigation Bulletin - Issue 26

On 23 September 2013, the crew of a Boeing 777-3ZGER aircraft operated by Virgin Australia, registered VH-VPE (VPE) conducted a scheduled passenger flight from Brisbane, Australia to Los Angeles, United States. At about 0305 Coordinated Universal Time in the cruise at flight level (FL) 310 and flying in clear air the aircraft encountered abrupt severe turbulence.  The flight crew turned on the seat belt sign, reduced the speed of the aircraft and requested from air traffic control a descent to a block altitude from FL310 to FL 290.

At the same time, the cabin crew had begun the meal service and the seat belt signs were turned off. Cabin crew members reported being thrown around the cabin by the turbulence with two of the 12 cabin crew hitting their heads on the aircraft cabin ceiling. Food and catering equipment were spread over seats, passengers and the aisles with the rear section of the aircraft affected the most. All passengers were seated at the time with their seat belts on. One passenger reported a sore neck and another passenger reported a burn injury as a result of a spilt hot meal. There were no reported injuries to the four flight crew.

This incident is a timely reminder for passengers to keep their seatbelt fastened when seated, pay attention to the safety demonstration and any instructions given by the cabin crew and read the safety information card in the seat pocket.

Aviation Short Investigation Bulletin - Issue 28

The ATSB was advised of two turbulence related events that occurred on 5 July 2013 and 7 July 2013, involving VH-VZY and VH-QOP respectively.

VH-VZY

On 5 July 2013, a Boeing 737 aircraft, registered VH‑VZY, departed Perth, Western Australia on a scheduled passenger service to Canberra, Australian Capital Territory. While descending through 8,000 ft, the aircraft encountered severe turbulence for about 2 minutes. The flight crew reported that they experienced difficulties with maintaining their assigned altitude of 7,500 ft for about 1 minute and the aircraft descended to 7,200 ft. A cabin crew member positioned in the rear of the aircraft sustained minor injuries.

VH-QOP

On 7 July 2013, a Bombardier DHC-8-402 aircraft, registered VH-QOP, was being operated on a scheduled passenger service from Wagga Wagga to Sydney, New South Wales.

During the cruise, while in clear conditions, maintaining flight level (FL) 210, the aircraft experienced severe turbulence. The turbulence ceased for about 2 seconds and moderate turbulence was then experienced. The aircraft pitched upwards by 5°, the right wing dropped by 7°, and the airspeed increased by about 20 kt. The seat belt sign was turned on. Overall, the turbulence encounter lasted for about 6 seconds. It was reported that a passenger sustained a broken or dislocated ankle, and a cabin crew member sustained an ankle injury.

Research conducted by the Australian Transport Safety Bureau (ATSB) identified that 99 per cent of people on board an aircraft receive no injuries during a typical turbulence event. However, passengers and cabin crew not wearing a seat belt can be thrown around without warning.

Aviation Short Investigation Bulletin - issue 23

On 10 May 2013, at about 2000 Eastern Standard Time, a Sunstate Airlines Bombardier DHC‑8‑402 aircraft, registered VH‑QOD (QOD), departed Townsville on a scheduled passenger flight to Cairns, Queensland. 

About 20 minutes into the flight, the aircraft was in the cruise at FL 180 and flying in clear air when the aircraft encountered light turbulence. The captain immediately switched on the seat belt sign. A second later, the aircraft encountered abrupt severe turbulence.

 The autopilot disconnected and the captain, as pilot flying, assumed manual control of the aircraft. The flight crew reduced the speed of the aircraft to below the turbulence penetration speed. The turbulence event lasted about 10 seconds, during which time the aircraft climbed about 400 ft above the cruising altitude. The flight crew then re-engaged the autopilot and returned the aircraft to the assigned level.

The weather radar did not show any significant weather for the entire flight. Both members of the cabin crew were standing when the aircraft encountered the turbulence and impacted the roof before falling to the floor. Both sustained head injuries and one was knocked unconscious.

The aircraft landed in Cairns about 20 minutes later, without further incident and the cabin crew were transferred to hospital.

In this event, all passengers were seated with their seat belts fastened, even though the seat belt sign had been switched off earlier. The fact that none of the passengers were injured highlights the benefits of keeping your seatbelt fastened during the flight.

Cabin crew are at greater risk of injury during turbulence encounters as they are moving around the cabin and not seated with a seat belt fastened.

Aviation Short Investigation Bulletin - Issue 23

On 13 September 2012, a Boeing 737 aircraft, registered VH-YIO (YIO), departed Bali International Airport (Denpasar), Indonesia on a scheduled passenger service to Brisbane, Queensland.

The aircraft became established in the cruise and the seat belt sign was turned off. Shortly after, the crew observed opposite direction traffic on the aircraft’s traffic alert and collision avoidance system (TCAS), about 1,000 ft above and slightly to the left. The crew observed the aircraft pass to the left. Airservices Australia surveillance data indicated the aircraft passed with about 0.9 NM lateral and 1,400 ft vertical separation.

Soon after, the First Officer reported that they felt ‘cobblestone’ like turbulence. The aircraft then experienced a wake induced roll, initially to the right to a maximum angle of 6.5° and then left to 40.4°, with a 40 ft loss in altitude. As the roll to the left commenced, the crew immediately responded by applying full right aileron deflection. 

Surveillance data indicated that there was about 2.1 NM lateral, and 1,400 ft vertical separation and the correct air traffic control separation standards were being applied at the time. Nil injuries were received.

This incident demonstrated the value of periodic recurrent training, allowing the crew to react to the wake turbulence encounter intuitively and promptly. Furthermore, it is a timely reminder of the benefits of having the seat belt fastened, even when the seat belt sign is turned off, so that injuries during a turbulence encounter can be minimised.

Aviation Short Investigation Bulletin – Issue 17

On 20 May 2011, a Qantas Airways Boeing 767-338 aircraft, registered VH OGR, was being operated on a scheduled passenger service from Melbourne, Victoria to Perth, Western Australia.

During the approach to runway 03 at Perth, the aircraft encountered turbulence over a 9 second period, with severe turbulence recorded for 3-4 seconds during that time; a go-around was conducted.

Two passengers, who were reportedly not wearing their seat belts at the time, sustained head injuries from coming into contact with a window reveal and an overhead locker. After landing, both passengers received medical attention, with one being transported to hospital.

As a result of this occurrence, the aircraft operator has advised the ATSB that they intend to present this incident at the Airservices Australia industry participation working group for discussion; to improve the dissemination of information relating to windshear events.

Generally, 99 per cent of people receive no injuries during a turbulence encounter; however, if passengers and cabin crew are not wearing their seatbelts, they can be thrown around without warning. Almost all in-flight turbulence injuries could be avoided by wearing a seatbelt and paying attention to any safety announcements made by the flight crew and cabin crew during the flight.

On 31 January 2011, a Boeing Company Aircraft 777-3ZGER, registered VH-VPH, was en-route from Phuket, Thailand to Melbourne, Victoria. When the aircraft was 170 NM north of Jakarta, Indonesia it encountered a period of sudden and unexpected turbulence. Six cabin crew members and four passengers received minor injuries.

At the time of the incident, the aircraft was established in the cruise and flying in cloud. The weather radar showed no significant weather in the immediate vicinity of the aircraft.

The flight continued to Melbourne where two cabin crew members consulted with paramedics, however no medical treatment was required.

The operator is considering including details of this occurrence in flight crew and cabin crew training to improve general crew awareness on the practical aspects of turbulence management and the importance of cabin discipline particularly relating to the handling of cabin equipment.

The operator is also considering changing a number of internal procedures to improve or standardise processes related to reporting injuries, providing support to crew in remote ports and assessing when crew are fit to return to duty.

On 16 February 2011, a Piper Aircraft Corporation PA-30 aircraft, registered VH-MAC, was being operated on a private flight from Coldstream, Victoria, to Canberra, Australian Capital Territory, via Strathbogie, Wangaratta Vic. and Albury, NSW, under the instrument flight rules. On board the aircraft were the pilot and one passenger. In preparation for the flight, the pilot had submitted a flight plan and obtained an aviation meteorological area forecast the previous evening.

After departure from Coldstream aerodrome, the pilot obtained clearance to 9,000 ft above mean sea level. While flying in light cloud and passing NE of Albury, tracking to Canberra, the aircraft encountered severe turbulence. After experiencing uncommanded climbs and descents continuously for nearly 35 minutes, while at times becoming inverted, the pilot saw terrain through a break in the cloud and flew clear of the cloud. The pilot then decided to divert to Albury and landed safely a short time later.

The pilot stated that in future, he would check the aviation area forecast prior to departure.

The aircraft was operating as Flight QF004/145 from San Francisco to Sydney, cruising at flight level 390 in smooth, clear, moonless conditions. The aircraft Captain occupied the left control position and the Second Officer occupied the right. The weather radar system was serviceable and operating. No significant weather had been forecast or observed by the crew during the flight. Although the "fasten seatbelt" signs had earlier been turned off, passengers had been advised, by cabin announcements, that it was recommended that seat belts should be worn unless moving around the cabin. This information was also included in the passenger safety briefing cards as well as being stamped onto each seatbelt buckle. About six hours after leaving San Francisco, the Captain noticed stars he had observed from his left window were becoming obscured. Upon closer inspection he noticed cloud ahead, and to the left of, the aircraft. Although no weather radar returns were apparent, the Captain took the precaution of turning on the fasten seatbelt signs. Approximately 15 seconds later the aircraft encountered a short period of moderate to severe turbulence. A number of passengers and flight attendants were flung about the cabin, incurring minor injuries as they struck fixed objects. Damage to the aircraft was minor and confined to internal fittings. After considering the condition of the injured, the enroute medical facilities and the superficial nature of the aircraft damage, the Captain decided the flight should continue as planned. The aircraft subsequently landed at Sydney where further medical treatment was provided. Twenty passengers required short term treatment in hospital. The investigation of the incident revealed that the flight crew had operated the aircraft in accordance with approved company procedures. Their knowledge, and use, of the weather radar systems was considered satisfactory. All weather radar systems depend on the fact that water particles, either in suspension (cloud) or as rainfall, will reflect a radar energy beam to an extent generally dependent upon the density and size of the water droplets. The aircraft encountered vertical air currents associated with an isolated towering cumulus cloud, which evidently contained insufficient moisture to be detectable by weather radar.