United flight 232 was enroute from Denver to
Chicago on the afternoon of July 19, 1989.
On the flight deck at FL370 that day was
Captain Al Haynes, a 30,000 hour pilot,
First Officer William Records, and Flight
Engineer Dudley Dvorak. Along with eight
flight attendants, 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.
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 (centre) engine had
failed and asked for the engine shutdown
checklist to be started. As Dvorak began
the checklist, he noticed that all three
hydraulic systems were loosing pressure
and quantity. Instead of straitening 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 aircraft
had now began a descent. Haynes attempted
to fly the aircraft via his controls but
found 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 aircraft back to wings-level.
The crew then gave a call to Minneapolis
Centre relaying their problem. The
controller initially gave 232 a vector
towards Des Moines International, but
seeing that the aircraft had continued
it's turn back towards the west before
straightening out, he then gave 232 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
attendants 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 control surfaces and
had only the engine power of the left and
right engines to control the aircraft. 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.
232 Explodes on Impact
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
floor 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 frequency for
9,000ft runway 31. The crew continued to
prepare for emergency landing, dumping
fuel and extending the landing gear. A
flight attendant 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 22. 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 1,600feet/minute
at around 215kts. In an incredible feat of
airmanship, they managed to touch down
near the beginning of the runway just off
the centreline.
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, despite the explosion and high
speed break-up, 185 people survived the
accident, including all four crew members.
......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 separated in
flight. The failure of the number 2 engine
sent fragments 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
properties.
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 maintenance and
six times had been subjected to
fluorescent penetration inspections.
Investigators concluded that human error
was responsible in improperly identifying
the fatigued area before the accident.
Subsequent simulator
tests showed that other DC-10 crews were
unable to repeat the effort of the crew of
232. Investigators concluded that, in it's
damaged condition, it was not possible to
land the aircraft on a runway. As a
result, the crew was giving much praise
for managing to put the aircraft down just
off the runway centreline and saving as
many lives as they did.