Report: United Airlines Flight 232
By: Chris Kilroy
United flight 232 was enroute from Denver to Chicago
on the afternoon of July 19, 1989. On the flight deck that day were
Captain Al Haynes, a 30,000 hour pilot, First Officer William Records, and
Flight Engineer Dudley Dvorak. Along with eight flight attendents, there
were 285 passengers on board the DC-10. Shortly after crossing into
Iowa, the aircraft began a gentle right turn to take it direct to Chicago.
|A frame from an amateur video shows United 232 exploding on impact.
With Records flying, there was a loud bang from the rear of the aircraft,
causing the entire aircraft to shudder. Haynes saw that the number two (center)
engine had failed and asked for the engine shutdown checklist to be started.
As Dvorak began the checklist, he noticed that all three hydrualic systems
were losing pressure and quantity.
Instead of straightening out, the aircraft
continued it's right turn. Records disconnected the autopilot and attempted
to level the aircraft out, but he found that he could no longer control the
aircraft. Meanwhile, the plane had now begun a descent. Haynes attempted
to fly the aircraft via his controls but with the same result. He then eased
the power back on the port engine and the excess thrust on the starboard
side began to roll the aircaft back to a wings level attitude.
The crew gave a
call to Minneapolis Air Traffic Control Center relaying their problem. The controller initially
gave 232 a vector towards Des Moines International, but seeing that the aircraft
had continued its turn back towards the west before straightening out, he
then gave it a vector towards Sioux City Gateway Airport. Located on the
east bank of the Missouri river, Gateway had a runway of 9,000ft and another
of 6,600ft. It had a third runway of nearly 7,000ft which had been closed
for some time.
Haynes alerted the passengers that they had lost the number
two engine and then instructed the flight attendents to prepare the passengers
for an emergency landing. The crew had come to the realization that they
were now unable to move any of the aircraft's control surfaces and had only the engine
power of the left and right engines to control the aircraft.
|A photograph taken of the aircraft on final approach to Sioux City. Note the missing tailcone and damage to the horizontal stabilizer.
It turned out
that one of the passengers on board flight 232 was Dennis Fitch, a United
training and check pilot with over 3,000 hours on the DC-10. Haynes asked
Fitch to go back and look out the windows to check for any structural damage.
When Fitch returned to the flight deck, he informed Haynes that the both
of the inboard ailerons were sticking up, but none of the controls appeared
to be damaged or moving.
Haynes asked Fitch to take control of the throttle
levers to allow the crew time to sort out the other decisions they were facing.
Fitch knelt down in front of the controls and began to work with the throttles
to maintain control of the aircraft. During this time, the aircraft had completed
two slow right turns while descending. Calling Sioux City approach, Haynes
requested the ILS (Instrument Landing System) frequency for runway
The crew continued to prepare for an emergency landing, dumping fuel
and extending the landing gear. A flight attendent reported that she saw
damage to the aircraft's horizontal stabilizer which Dvorak went back and
confirmed. The aircraft was now descending through 9,000ft some 21 miles
northeast of the airport. Approach asked 232 to fly southbound to keep it
east of the city and set it up for an approach to runway 31.
Fitch was unable
to fight the aircraft's continuing efforts to turn right and, instead of
turning southbound, the aircraft again flew a 360 which Fitch was able to
stop just as the airport lay ahead of them. They were now 12 miles from the
airport and lined up with the closed runway, the 6888ft. runway
Fortunately, there was an open field at the far
end of the runway. The controller cleared them to use the closed runway and
the crew managed to get the aircraft flying straight. Unfortunately, they
couldn't accurately control the airspeed and sink rate. They were descending
at over 1,600 feet per minute at around 215 knots. In an incredible feat of airmanship,
they managed to touch down near the beginning of the runway just off the
centerline. Unfortunately, the starboard wingtip touched down just prior
to the landing gear, pulling the aircraft sideways. The excess airspeed and
high sink rate caused the aircraft to break up on impact, igniting into a
huge fireball. Amazingly, depsite the explosion and high speed break-up,
185 people survived the accident, including all four cockpit crew members.
|Parts of the wreckage of United 232 can be seen to the left in this photo, showing the impact the aircraft produced as it slid across Runway 31 at Sioux City's Gateway Airport..
Examination of the wreckage showed that portions
of the number 2 engine fan blades were embedded in the empennage. Missing
from the wreckage was number 2 engine fan module, which had seperated in
flight. The failure of the number 2 engine sent fregments through the empennage,
rendering all three hydraulic systems inoperable, all of which had critical
components that ran together near the engine casing. Several farmers living
northeast of the city reported finding various parts of the aircraft on their
Investigators were able to recover the aircraft's
tailcone as well as half of the fan containment ring. Also found were fan
blade fragments and parts of the hydraulic lines. Three months after the
accident, two pieces of the engine fan disk were found in the fields near
where the first pieces were located. Together the pieces made up nearly the
entire fan disk assembly. Two large fractures were found in the disk, indicating
overstress failure. Metallurgical examination showed that the primary fracture
had resulted from a fatigued section on the inside diameter of the disk.
Further examination showed that the fatiguing had resulted in a small cavity
on the surface of the disk, apparently a defect in manufacturing. The 17
year old disk had undergone routine maintainence and six times had been subjected
to flourescent penetration inspections. Investigators concluded that human
error was responsible in improperly identifying the fatigued area before
Subsequent simulator tests showed that other DC-10 crews
were unable to repeat the effort of the crew of 232. Investigators concluded
that, in its damaged condition, it was not possible to land the aircraft
on a runway. As a result, the crew was given much praise for managing to
put the aircraft down just off the runway centerline and saving as many lives
as they did.