Wake turbulence that is suspected of causing the upset that injured 15 on a Qantas 747, south of Hong Kong, on April 7 is a growing problem that needs another look.

According to Aviation Herald reports,  there have been 34 wake turbulence incidents in the past 10 years but 11 of those have been in the past two years.

The most serious was the apparent encounter between an Emirates A380 and a corporate jet. The A380 was performing flight EK412 from Dubai to Sydney and was at FL350 about 630nm south-east of Muscat when the business jet passed underneath in the opposite direction.

The corporate jet, an MHS Aviation Challenger 604 was operating flight MHV-604 from Male to Abu Dhabi with 9 people on board and was en route at FL340.

After the A380 passed the crew lost control of their jet and were only able to regain control of the aircraft only after losing about 10,000 feet. A number of the passengers sustained injuries.

Wake turbulence is a natural by-product of powered flight but was not generally regarded as a serious flight hazard until the late 1960s, says the US FAA.

Interest – and concern – in this phenomenon greatly increased with the introduction of large wide-body turbofan aircraft during the late 1960s and a concern about the impact of greater wake turbulence.

The FAA said that “this was the impetus to conduct research to gain additional information and determine what safety considerations were necessary as more and more large aircraft entered the industry fleets.”

According to the FAA “an investigation of the wake-turbulence phenomenon, conducted by Boeing in mid-1969 as part of the FAA test program, included both analysis and limited flight test and produced more detailed information on wake vortices. The flight tests provided a direct comparison between the 747 and representative from the then current jet fleet, a 707-320C.

Those tests that were later extended made several observations;

1.    The strength of the wake turbulence is governed by the weight, speed and wingspan of the generating aircraft.

2.    The greatest strength occurs when the generating aircraft is heavy, at slow speed with a clean wing configuration.

3.    The wake was observed to move down initially and then level off and it was never encountered at the same flight level as the generating aircraft or more than 900 feet below the generating aircraft.

Minimum radar-controlled wake turbulence separation distances were established for the following aircraft with the separation distances depending on the weight of both the leading and following aircraft.

Adjustments in separation distances were made as more information on the wake-turbulence phenomenon was gained during the 1960s, 1980s and 1990s, but the basic concept of using aircraft weights remained constant.

The US National Transportation Safety Board data show that between 1983 and 1993, there were at least 51 accidents and incidents in the United States that resulted from probable encounters with wake turbulence.

In these 51 encounters, 27 occupants were killed, 8 were seriously injured, and 40 aircraft were substantially damaged or destroyed.

But by far the worst encounter was the November 12, 2001 , loss of an American Airlines A300, Flight AA587, in New York with 265 lives lost.

The A300 took off after a Japan Air Lines Boeing 747, flight JL047, bound for Tokyo-Narita. While JL047 was preparing for takeoff, the tower controller called AA587, cautioned the flight crew about wake turbulence.

While in a climbing left turn, the crew of AA587 heard a rattling sound, possibly caused by wake turbulence and then fifteen seconds later the Airbus began to yaw to the right.

The first officer, who was the flying pilot, applied full right and left rudder and called for max power.

He then again full right and left rudder and the tail of the A300 snapped off and the plane crashed into the Queens area killing 5 on the ground as well as all on board.

According to Aviation-safety.net the probable cause was: “The in-flight separation of the vertical stabilizer as a result of the loads beyond ultimate design that were created by the first officer’s unnecessary and excessive rudder pedal inputs. Contributing to these rudder pedal inputs were characteristics of the A300-600 rudder system design and elements of the American Airlines Advanced Aircraft Maneuvering Program. ”

While the Airbus A380 has been singled out of attention, wake turbulence is an industry-wide problem that is increasing mainly because air traffic is doubling every 15 years.

And with that increase in air traffic comes congestion and more stacking or holding of aircraft prior to landing.

With more larger aircraft such as the A380, 747 and 777 and increasing traffic perhaps the time has come to revisit strategies to avoid wake turbulence.

Someone in the US  government has received the message that airline passengers don’t want their fellow flyers yapping away on cell phones while in flight.

That’s one reason Federal Communications Chairman Ajit Pai has proposed an order that would end the commission’s consideration of lifting a prohibition on in-flight cell phone use. The ban has been in effect since 1991.

The commission has yet to formally vote on Pai’s proposal.

In a statement, Pai said he stood with airline pilots and flight attendants and the traveling public in supporting a measure that would terminate the FCC’s 2013 proceeding that sought to relax rules governing mobile phone use in aircraft.

“I do not believe that moving forward with this plan is in the public interest,” he said. “Taking [it] off the table permanently will be a victory for Americans across the country who, like me, value a moment of quiet at 30,000 feet.”

According to USA Today, in 2014 the U.S. Department of Transportation solicited public comment as to whether to allow to voice calls aloft if the FCC dropped the ban. DOT got some 1,700 comments with a  full 96 per cent favored keeping the ban in place.

Two per cent favored the ban, with exceptions for emergencies. Another two per cent argued airlines should set their own phone policies.

In this latest call for public comment, passengers’ responses were cut from same cloth and an AirlineRatings review underscored the strong reaction against in-flight voice calls.

Frequent flyer William Box (165,000 miles last year) of Franklin, Tennessee said he “can’t imagine the change in an aircraft’s environment” should the ban not stay in place. “Many flyers are ‘stressed’ as it is.”

M.W. McSherry of Danville, Virginia could “scarcely imagine the cacophony of dozens of voices in an already noisy and cramped cabin, all straining to be heard over the ambient noise and each other…There’s no compelling public interest in allowing voice calls.”

William Witter of Boulder, Colorado believed “voice calls in aircraft would dramatically harm public order on an aircraft.”

Greg Marino of Loveland, Colorado asserted:  “Flying has become unpleasant enough without having to listen to the guy next to you talk loudly into his phone the entire flight.”

Keeping the ban in place is more than an exercise in passenger sanity. Flight attendants contend it’s a safety matter.

They’re concerned terrorists could coordinate attacks and passengers might start fighting because of a seatmate’s incessantly loud chatter.

The Qantas 747 that suffered severe buffeting 110km south of Hong Kong on April 7 apparently encountered wake turbulence from another aircraft flying just above it.

The incident, which the Australian Transport Safety Bureau termed as serious, injured 15 passengers.

The area just south of Hong Kong is very congested often with aircraft in various holding patterns as air traffic control manages the traffic flow.

Wake turbulence is turbulence that forms behind an aircraft as it passes through the air. This turbulence includes various components, the most important of which are wingtip vortices and jetwash.

READ: Emirates A380 sends jet into a spin

Qantas Flt QF29 was operating from Melbourne to Hong Kong.

According to the ATSB, the 747 was about to enter a holding pattern at Flight Level 220 (22,000ft) about 110km (60nm) south-east of Hong Kong at a waypoint called BETTY when the aircraft’s stick shaker activated.

The stick shaker is a mechanical device that noisily vibrates the pilot’s control column or yoke (the stick) to warn of an imminent aerodynamic stall.

(An aerodynamic stall occurs when the angle of attack of the wing causes the air moving over the upper surface to separate from the wing, causing a loss of lift and control.)

However, Boeing warns that “a stall must not be confused with the stall warning that alerts the pilot to an approaching stall. Recovery from an approach to stall is not the same as a recovery from an actual stall. An approach to stall is a controlled flight manoeuvre; a stall is an out-of-control, but recoverable, condition.”

The Qantas crew immediately disconnected the aircraft’s autopilot and recovered the aircraft manually,  the ATSB said.

“While holding at flight level 220, the flight crew received a stick shaker activation and detected airframe buffeting,” it said. ” The flight crew disconnected the autopilot and manoeuvred the aircraft in response.”

One of the passengers, teacher Jemma Gendall, told 9news.com.au that the pilot made a PA to the passengers telling them that “another aircraft flying overhead had become too close and caused the altitude drop”.

Wake turbulence incidents involving A380s, 747s and 757s are a serious issue and have caused a number of deadly crashes as well as numerous injuries to passengers and crew on other aircraft flying just below that encounter the wake.

The wake turbulence would have caused significant upset to the 747 and triggered the stick shaker and other alarms.

The 747 in question has continued to operate flights normally since the incident.

Qantas confirmed that passengers on QF29 experienced “unexpected turbulence’’ about an hour before landing.

The airline said the incident lasted about two minutes and the captain called for an ambulance to meet the aircraft on arrival.

The injuries were minor, but one passenger was transferred to hospital for a precautionary medical assessment and later released.

“We notified the ATSB of the occurrence, and our teams are also reviewing the event,’’ the airline said in a statement. “These investigations need to be completed before Qantas can comment further.”

The head of United Airlines has issued a grovelling apology to a doctor dragged off one of its flights as the US carrier battles to address a global tsunami of reputational damage and a potential legal move from the passenger.

United chief executive Oscar Munoz issued the belated apology to the 69-year-old doctor, identified as David Dao,  who was forcibly dragged from a United Express plane in Chicago on Sunday so a  United crew member could take his seat.

But that was not before videos of the incident swept around the world, prompting calls for boycotts and sparking an angry backlash in the fast-growing and strategically important Chinese market.

Memes have already started spreading through social media lampooning the airline’s brutal treatment of its passenger

Even White House spokesman Sean Spicer found the video of Dao’s ordeal  “troubling”.

Read: The viral Video hits Delta did not want.

Munoz had already issued one apology that had been criticised for its “tone-deaf’  wording.   He also sent an email to staff saying that while he deeply regretted the situation, he emphatically stood behind them and commending them for “continuing to go above and beyond to ensure we fly  right’’.

“The truly horrific event that occurred on this flight has elicited many responses from all of us: outrage, anger, disappointment,’’ Munoz said in his second effort, released on Tuesday.  “I share all of those sentiments, and one above all: my deepest apologies for what happened.

“Like you, I continue to be disturbed by what happened on this flight and I deeply apologize to the customer forcibly removed and to all the customers aboard. No one should ever be mistreated this way.

“I want you to know that we take full responsibility and we will work to make it right.

“It’s never too late to do the right thing. I have committed to our customers and our employees that we are going to fix what’s broken so this never happens again.”

Dao was dragged from the plane after United failed to find volunteers willing to be bumped from the flight so that four its crew could take their seats. This was despite offering vouchers worth up to $US1000.

It then selected four passengers to be removed from the plane under its involuntary denied boarding policy. Three went quietly but Dao refused, saying he had to get home to treat patients.

Security was called and Dao was dragged bleeding from the plane as other passengers protested.

A United report included in the email from Munoz to staff said the passenger raised his voice and refused to comply with crew member instructions.

“He was approached a few more times after that in order gain his compliance to come off the aircraft and each time he refused and became more disruptive and belligerent,’’ it said, adding that staff had no choice but to call security agents

Munoz pledged to conduct a  thorough review of crew movement, the airline’s policies for offering incentives for volunteers when flights are overbooked and how the airline handles oversold situations.

It would also look at how it partners with airport authorities and local law enforcement.

“We’ll communicate the results of our review by April 30,’’ he said.

Controversy has also flared over US media reports of Dao’s criminal past as he recovered in a Chicago hospital.

A father of five and a grandfather who went to medical school in Vietnam, a Kentucky newspaper revealed his US medical licence was suspended for illegally prescribing painkillers amid allegations he did so with one patient in return for sex.

The Los Angeles Times reported medical documents showed that Dao had a history of mental health problems including depression, anxiety and post-traumatic stress disorder.  He had also been ordered to seek evaluation for “anger management” issues.

He fought to have his licence re-instated and underwent an “educational intervention plan’’   involving retraining and monitoring before it was restored in 2015.

Dao has now engaged Chicago lawyers Stephen Golan and Thomas Demetrio to act on the family’s  behalf.

The lawyers said in a statement: “Dr. David Dao, the United Airlines passenger who was removed from an airplane seat on United Airlines Sunday, is undergoing treatment in a Chicago hospital for his injuries.

“The family of Dr. Dao wants the world to know that they are very appreciative of the outpouring of prayers, concern and support they have received.  Currently, they are focused only on Dr. Dao’s medical care and treatment.”

Break out your Jerry Garcia ties — they won’t be out of place when Australian carrier Qantas hands out colourful new international business class amenity kits from the start of May.

The Australian carrier has selected 16 works from some of Australia’s leading artists, photographers and digital influencers to give passengers collectible pieces to take home.  Amenity kits have a myriad of post-flight uses so it’s not unusual for passengers to take the bags with them.

The sixteen amenity kits – eight each for men and women — feature names such as Fairy Bread, 7000 Ironbarks and Maaate.

They include pop culture, photography, fine art, abstract landscape, Indigenous art and textile design.

Two designs will launch every few months.

“As the national carrier, we’re pleased to support talented Aussies telling uniquely Australian stories through their artwork and share them with a global audience,” Qantas group executive brand, marketing & corporate Affairs Olivia Wirth said.

“Along with inflight pyjamas, we know amenity kits are an important part of the international Business class experience. Customers love the functionality of our kits and many use them after their flight as make-up bags, an evening clutch or to carry their mobile phones. So, the exposure is broad.”

The airline’s support for the arts includes a joint acquisition program for contemporary Australian art with Sydney’s Museum of Contemporary Art and Tate in the UK as well as support for organisations such as the National Gallery of Australia, Opera Australia, Australian Ballet and Bangarra Dance Theatre.