When United Airlines flight 232 slammed into the ground at the Sioux Falls, Iowa airport and exploded into a huge ball of flame on July 19, 1989, it became one of the most widely witnessed aviation disasters in history. The amateur video footage which captured and froze in time that terrible one minute of violence quickly blossomed on home television screens across the country and around the world; and it would be viewed repeatedly for months and even years to come. What the general public might at first have thought was just an emergency landing gone wrong was in fact the inevitable consequence of a cascade of events which had begun 35 minutes earlier and 60 miles to the east when the tail-mounted and central of the jumbo jet’s three engines exploded at 37,000 feet. In the process, all three of the plane’s supposedly redundant hydraulic lines were severed leaving the cockpit crew with no means of controlling the giant jet other than by adjusting power alternately to the two remaining wing-mounted engines. Without flaps and spoilers, the only option was to literally “fly” the plane onto the ground at 250 miles per hour, and pilot Al Haynes and his “front office” crew did a masterful job of pulling off what they did.
That 184 of the plane’s 296 passengers survived the fiery impact was a miracle which still cannot be fully explained today. That investigators were able to put together a jig-saw puzzle of bits and pieces spread across hundreds of square miles of space and months of time in order to solve a handful of aviation mysteries is the story behind the story; and the motivation for today’s column.
The turbofan jet engine gets its name from the large (71/2 foot diameter) multi-blade fan which sits at the very front of a modern jet engine pulling in huge amounts of air to both feed and supplement the thrust of the fuel-driven jet behind it. It was this fan on the General Electric CF-6-6 engine mounted in the DC-10’s tail section which exploded on that July day high above Buena Vista County, Iowa, doing damage to surrounding components – including the illogically-routed hydraulic lines – before the 400-pound component departed for the earth far below, subject to the laws of gravity, wind, trajectory and sheer chance.
In summer months, more than 12 million acres of Iowa countryside are clad in a rolling, green and nearly unbroken canopy of corn. To make searching conditions even worse, those tall rows of flowering stalks were engulfed in a nearly physical cloud of pollen dust during the weeks when thousands of citizen volunteers and law enforcement professionals were tasked with walking a grid pattern through miles of those breath-constricting rows in search of any piece of wreckage which might lead to the elusive fan hub in which the ultimate answers were believed to lie. Even a generous reward system failed to produce results as the trail grew cooler, while the use of low-flying helicopters only succeeded in angering farmers who watched their corn fields being blown into patches of mulch.
While the airframe of the DC-10 with tail number N1819U had seen numerous engine changes in its nearly 20-year operating life, the particular GE engine in question had seen more than 15,000 cycles (landing/takeoffs) at a time when titanium-rich fan design represented a relatively-new technology. An entire industry awaited answers as one season morphed into another.
On the afternoon of October 10th -- 83 days after UAL 232 and its pieces came to earth -- 58-year-old Janice Sorenson was driving her harvester down the corn rows near her home just north of Alta, Iowa when the machine ran up against something that shouldn’t have been there: the largest part of a disk partially buried in the rich Iowa soil. Two days later, a neighboring farmer, Harold Halverson found the rest of the 350-pound fan wheel less than two miles away, and the NTSB and a panel of waiting analysts finally had their “smoking gun.” And a surprised Janice Sorenson would receive a check for $116,000!
The almost-microscopic flaw which had bloomed into a crack in the fan wheel’s titanium hub would lead to a whole new set of testing methods and standards, the DC-10’s hydraulic system would see major routing changes, and United and other air lines would alter the frequency and depth of engine testing and replacement protocols.
POST SCRIPT: As a result of examining the life changes of Flight 232 survivors and their rescuers over the years following the incident, we learn that PTSD with all of its ramifications exists beyond the battlefield and is just as real.