Rows of ambulances were lining up at the jetway at New York’s JFK International Airport (KJFK) when a Turkish Airlines Boeing 777 pulled into the gate on March 9, 2019, all there to whisk 30 injured occupants to nearby hospitals. Afterward, passengers recounted and videos confirmed bodies being tossed into the overheads and blood everywhere. Some vowed never to fly again.
Unfortunately, what happened on Turkish Flight 001 is hardly without precedent. And injuries from inflight turbulence will happen again.
According to NTSB Senior Meteorologist Donald Eick, turbulence has caused more serious injuries to passengers than any other class of accident. Between 2000 and 2011, 71% of air carrier weather-related accidents were due in part to turbulence. On average, FAR Part 121 carriers experience 27 “significant turbulence” events annually, resulting in 14 serious and 69 minor injuries.
These short-lived but violent encounters can even be fatal.
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Pacific Nightmare
On Dec. 28, 1997, a United Airlines Boeing 747 cruising at a cloud-free FL 310 en route from Tokyo to Honolulu encountered clear air turbulence (CAT) so severe that one seat-beltless woman was thrown upward and smashed into the ceiling so forcefully, she was killed. Another 18 passengers received serious injuries and 171 suffered minor injuries.
The official accident report reveals the flight crew had tried to make the best decisions possible with the information available but also illuminates the difficulty in doing so when in oceanic airspace. According to the captain, a veteran of 30-40 Pacific crossings, because of his concern about turbulence, he chose an oceanic track that had no SIGMETs near it. Further, he briefed the purser of the possibility of turbulence approximately 2 hr. after takeoff.
During the en route climb the captain made a PA announcement including a request that each passenger keep his or her seat belt fastened when seated. However, most of the passengers spoke only Japanese and a bilingual flight attendant did not fully translate into Japanese one of the captain’s instructions to fasten seat belts, although such an announcement was made and translated several times prior to the CAT encounter.
One hour, 40 min. into the flight the airplane encountered what the captain described as “wave action,” and he turned the seat belt sign on as a precaution. PA announcements were made in English and Japanese. The captain radioed a Northwest flight up ahead requesting its experience and was told the ride was smooth with occasional light turbulence. No more than 2 min. later, the United aircraft was in turbulence. Seconds later there was another episode, at which point the captain instructed the flight attendants to sit down. He ordered the first officer to reduce speed and the aircraft slowed to 330-340 KIAS. At the time of the encounters the total air temperature read approximately -40C to -44C. There was no rapid change in wind direction or speed before or after the encounter.
After the flight crew dealt with several warning lights, the captain asked the second officer to check on the condition of the cabin crew and passengers. After he returned to the cockpit with a preliminary report, the captain went back to observe the damage and injuries himself.
The nearest suitable landing airport was Midway Island, which the captain considered appropriate if there were structural damage to the aircraft, but he favored Narita for medical treatment for the injured. In addition, a medical doctor who was a passenger suggested getting medical aid as soon as possible. After assessing the aircraft’s airworthiness and collecting information on the injuries — a process that took about 20 min. — the captain used his emergency authority to turn off course and climb 500 ft. Upon request, Tokyo ATC quickly granted a clearance back to Narita and emergency services met the aircraft when it landed.
The upper air data at the time of the turbulence encounter showed westerly winds at 105 kt. at 30,000 ft. and 125 kt. at 34,000 ft. Significant horizontal wind shears were evident in the area. The flight data recorder indicated that while the aircraft was cruising at FL 310, it experienced a +1.814 vertical acceleration, followed 6 sec. later by a -0.824 one. The aircraft rolled 18 deg. right-wing down and recovered to wings level shortly thereafter. Altitude excursions were nominal.
The NTSB determined the probable cause of the accident to be the PIC’s inadvertent flight into adverse weather conditions, and the difficulty of obtaining adequate weather forecasts of over-ocean turbulence. It is significant to note that none of the passengers who sustained serious injuries were wearing their seat belts at the time.
Mitigating Turbulence
Load factor variations generated by turbulence are not necessarily the same throughout an aircraft. According to the Airbus document “Managing Severe Turbulence,” the vertical longitudinal motions are concentrated within a few seconds and injuries generally occur to non-buckled passengers and cabin crew when the vertical load factor decreases under 0g before increasing again. Turbulence has a great impact on those in the aft cabin, which is where nearly eight out of 10 injuries have occurred, according to the training video “Turbulence Education and Training Aid.”
Most injuries result when non-buckled passengers or cabin crewmembers are tossed during turbulence. Advisory Circular 120-88A, “Preventing Injuries Caused by Turbulence,” dated Jan. 19, 2006, strongly suggests that during a turbulence encounter passengers and cabin crew be sitting with seat belts fastened. From 1980-2003, only four belted people received serious injuries during turbulence. Yet despite the mandatory before-takeoff briefings about seat belt usage, too many passengers release their buckle at cruise.
During turbulence any loose object can become a projectile. Soda cans can fly across a cabin with enough energy to cause severe harm. Food service carts not attached to the floor can crush the unlucky. Coffee pots can scald. Flimsy latches on overhead bins can fail, thereby launching loose luggage as blunt missiles.
Unfortunately, unrestrained infants are especially prone to being ripped free from a parent’s protective arms by turbulence. A United Boeing 737 en route from Denver to Billings, Montana, on Feb. 17, 2014, encountered severe turbulence at FL 340. An infant was flung from its mother’s arms but fortunately landed in an adjacent seat. Unfortunately, three of the flight attendants aboard were injured, one with a severe head wound. The flight crew declared an emergency and upon landing those injured were rushed to the hospital.
Quite correctly, the FAA urges passengers to use an approved child-safety seat when flying with children under two years of age.
Avoiding Turbulence
Again citing Airbus’ “Managing Severe Turbulence,” weather information available before takeoff and weather briefings have to be as complete as possible, and depending on context, this information has to be updated in flight as often as possible. In some severe turbulence events, post-flight investigations revealed that an appropriate update of weather information in flight would have very likely allowed its avoidance.
Up until recently the only routine observations of turbulence have been those provided verbally as pilot reports (PIREPs) in the U.S. and as air reports (AIREPs) internationally. Unfortunately, PIREPs can err substantially in the activity’s reported intensity, position and time. Transcontinental flights have the benefit of reports from heavily traveled air lanes. By contrast, flights over some oceanic regions are notoriously “data sparse.”
And even though formal definitions of the severity categories are provided in terms of normal accelerations or airspeed fluctuations, in practice the measures are subjective and aircraft dependent, meaning that a heavily loaded Boeing 727 with its highly swept wing will experience less aircraft disturbance than a lightly loaded straight-wing King Air. Pilot observations are therefore often unreliable for providing consistent information about atmospheric turbulence levels.
Airborne weather radar does not assure protection from turbulence. An Airbus review of previous turbulence encounters revealed that some flight crews lacked a full appreciation of the intensity and extent of the weather in their vicinity. As a result, they failed to deviate soon or far enough to avoid the weather.
As is well known, airborne weather radar detects precipitation but not wind, ice, fog or CAT. When properly utilized, the equipment can be quite efficient in the detection and avoidance of convective clouds laden with droplets. It is only helpful for the avoidance of turbulence associated with detectable precipitation — in other words, associated with convective storms. And to do so, it must be properly tuned (tilt, weather mode and range control) to present an optimum weather radar picture. Also, the flight crew must perform regular vertical scans and interpret the screen display correctly. For example, a tilt setting in cruise too close to the horizon will only scan in a high range of altitude where precipitation particles are in ice form and poorly reflect radar signals.
Satellites can be used to predict the turbulence associated with convection, and the new generation of satellites (GOES-16) with higher spatial and temporal resolutions have the potential to improve turbulence avoidance by helping identify deep convection and detecting gravity waves.
Analysis by Airbus found that a large part of turbulence events come from aircraft incursions into cumulonimbus that were either not localized by the crew or not avoided with sufficient margin.
Furthermore, turbulence associated with cumulonimbus is not only contained within the cloud. And since current weather radars cannot detect dry turbulence, it is essential to take adequate precautionary measures, and to do so especially in the “clear air” above a thunderstorm.
Cabin Preparation
Aircraft cabins are not designed to provide readily available restraints in case of turbulence. For example, the lav and galley often lack safety features such as hand holds for support when passengers or crew are unrestrained during unexpected encounters.
Accordingly, it’s good practice to keep the cabin as ready as possible for turbulence and to periodically check that passengers are wearing seat belts, that bins are latched, and carts and other loose items stowed.
Summary
The costs to operators that result from turbulence encounters can be substantial and involve medical attention, liability suits, lengthy absences of injured cabin crewmembers, higher insurance premiums and workers compensation, along with repairs to the aircraft and the loss of aircraft availability due to inspections. Moreover, any inflight injury to passengers or crew may require a flight divert and emergency landing, which can be a costly necessity when operating in remote or oceanic airspace.
The NTSB has issued abundant recommendations for countering exposure to inflight turbulence. We all need to put them to practice.
And people in back, please keep those seat belts buckled. They’re there to keep you pain free.
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