Growing threat of wake turbulence, with larger, heavier planes – and more crowded airspace
Date added: April 17, 2017
Wake turbulence may be a growing problem that needs more investigation and reassurance for air passengers. There were 34 serious wake turbulence incidents in the past 10 years but 11 of those have been in the past two years. The most serious was the encounter between an Emirates A380 and a corporate jet in March 2017. The A380 was on flight EK412 from Dubai to Sydney and was at FL350 (ie. 35,000 ft) about 630nm south-east of Muscat when the business jet passed 1,000 ft underneath in the opposite direction. The corporate jet, an MHS Aviation Challenger 604 was flying from the Maldives to Abu Dhabi with 9 people on board and was en route at FL340 (34,000 ft). 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. With more larger planes in global fleets, the problem may increase. The strength of the wake turbulence is governed by the weight, speed and wingspan of the generating aircraft. The greatest strength occurs when the generating aircraft is heavy, at slow speed with a clean wing configuration. It is an industry-wide problem that is increasing mainly because air traffic is doubling every 15 years – so there is more air traffic congestion and more stacking or holding of aircraft prior to landing. . Tweet
The growing threat of wake turbulence
By Geoffrey Thomas – Editor-in-Chief (Airline Ratings)
15 Apr 2017
Wake turbulence is a deadly and invisible killer and needs another look
FAA illustration of wake turbulence
Wake turbulence from a Boeing C-17 creates spirals in the clouds below.
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.
By Geoffrey Thomas & Steve Creedy (Airline Ratings)
13th Apr 2017
Wake turbulence is believed responsible for the severe turbulence that injured 15 passengers
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.
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 private jet was carrying vacationers back from the Maldives to Berlin and cruising over the Arabian Sea when it passed 1,000 feet under an A380, Der Spiegel reported. A short time later, it rolled at least three times, throwing unsecured passengers around the cabin, and descended out of control “like a paper plane in a wind tunnel,” the newspaper said.
Germout Freitag, a spokesman for the BFU, confirmed the agency was investigating but said no details were available until an interim report was released. He added that there was no estimate when that would be published.
Steffen Fries, CEO of MHS Aviation, which is the largest executive jet operator in Germany, told NBC News: “Since the investigation from BFU is ongoing, we cannot comment.”
FlightGlobal reported that aviation authorities had issued revised guidance to Bombardier Challenger operators and air traffic controllers about the possible effects of wake turbulence from four-engined Airbus A380 planes on other aircraft.