Iowa

The pilot made four missed ILS approaches at the airport. He stated that he did not see the approach lights during any of the approaches and did not feel comfortable making a landing. The reported visibility during these approaches was 1/2-statute mile. On the fifth approach the pilot said he had '...mistaken closely inline cars and a road for the MALSR and runway.' He pilot stated the airplane continued to descend after initiating a go-around. He said he saw oncoming traffic in front of him, and turned the airplane to the right. He said he lost altitude and the right wing struck the ground. The pilot's employers operations specification require a 1/4- mile increase in visibility for an ILS approach that does not have an operating approach lighting system. The approach lights were checked by the airport manager and were confirmed to be in working order. An on-scene investigation revealed no pre-accident airframe or engine anomalies that would have prevented normal flight.

During a landing approach, the pilot noted that the right engine remained at a high power setting, when he moved the power levers to reduce power. He executed a missed approach and had difficulty keeping the airplane straight and level. The pilot maneuvered for a second approach to land. After landing, he could not maintain directional control of the airplane and tried to go around, but the airplane went off the end of the runway and impacted the localizer antenna. The pilot did not advise ATC of the problem nor did he declare an emergency. The Pilot's Operating Handbook stated that for a power plant control malfunction, the affected engine should be shut down, and a single engine landing should be made. The power control cable was found disconnected from the anchoring point. A safety tab was broken off the housing, allowing it to unscrew. About one month before the accident, maintenance had been performed on the right engine to correct a discrepancy about the right engine power lever being stiff. The mechanic re-rigged the right engine power cable.

According to the pilot, the airplane '...began moving to the left side of the runway...' immediately upon touchdown. He attempted to abort the landing but the airplane contacted snow at the runway's left edge. The airplane exited the runway's left edge and slid sideways, about 300 yards.

During flight, the pilot reported shutting down the left engine due to a loss of oil pressure. He declared an emergency and diverted toward an alternate airport. However, while diverting, radar and radio contact were lost, and the airplane crashed. The wreckage path covered a distance of approximately 60 feet; the descent angle during impact was estimated to be about 45°. Oil was found behind the left engine, on the left flap, on the bottom of the left horizontal stabilizer, and on the bottom of the fuselage. Also, fuel stains were seen in the grass around the airplane. No preimpact fire indications were found. The pilot had reported low oil pressure in the left engine before the accident flight, and purchased seven quarts of oil before departing. No indications of power at impact were seen on either engine or propeller. Numerous abnormalities existed with the left engine. No discrepancies were noted with the right engine. The farmer who found the wreckage reported that sleet was falling at the time of the accident. The pilot of another aircraft reported structural icing conditions.

While cruising at FL240, a propeller (prop) hub arm on the left prop failed, releasing the prop blade, which struck a 2nd blade, breaking off its tip. This resulted in a severe engine vibration and shutdown of the left engine. The left engine was forced downward and inboard on its mounts. The cabin depressurized, possibly from blade contact. The flight crew made an emergency descent and received a vector to divert for an ILS approach to Dubuque. The airplane was incapable of maintaining altitude and descended in instrument conditions. Subsequently, it collided with a silo and crashed about 8 miles south of Dubuque. An investigation revealed the left prop hub failed from fatigue that initiated from multiple initiation sites on the inside diameter surface of the hole for the pilot tube. There was evidence that the fatigue properties of the hub were reduced by a combination of factors, including machining marks or scratches, mixed microstructure, corrosion, decarburization, and residual stresses. All eight occupants were killed, among them George Mickelson, 52, Governor of South Dakota.

During the second ILS approach the airplane descended below the glidepath and impacted the terrain 2,500 feet short of the intended landing runway. The pilot indicated that a failure in the approach lighting system contributed to the accident. A post accident functional check of the approach lighting system failed to reveal any anomalies.

On final approach, after being cleared to land, the pilot informed the controller that he might have to shut down an engine. He declined to declare an emergency or request assistance. On short final, the aircraft was observed to roll to the left and descent into the terrain. Subsequent examination revealed evidence that the left engine was not developing power, although the left propeller was not feathered. There was evidence that the right engine was producing high power during impact. No mechanical deficiency of the left engine or propeller was found. The pilot, sole on board, was killed.

The aircraft was on an ILS approach at dusk in IMC and icing conditions with the alternate air on. According to the pilot, he had just descended below an overcast, on final approach, when the engine lost power and would not respond to throttle application. A forced landing was made in a wooded area short of the runway and the aircraft was extensively damaged. During an exam of the engine, the turbocharger and wastegate transition pipes were found separated at the flange. Carbonaceous residue was found in the area of separation, but no heat damage was noted. The gasket, bolts, washers and self-locking nuts (for holding the pipes together) were not found. Later, the engine ran successfully during an operational check. During the investigation, 3 similar cases of pipe separation were identified, which involved another aircraft; these resulted in only partial losses of power. The right front seat passenger reported seeing a trace of ice on the wings as the aircraft was descending thru clouds. The pitot heat, stall warning heat, and ice light switch were fnd in the 'off' position. At 1650 cst, the temperature and dew point at the surface were 36° and 35° respectively. All three occupants were seriously injured.

United Flight 232 departed Denver-Stapleton International Airport, Colorado, USA at 14:09 CDT for a domestic flight to Chicago-O'Hare, Illinois and Philadelphia, Pennsylvania. There were 285 passengers and 11 crew members on board. The takeoff and the en route climb to the planned cruising altitude of FL370 were uneventful. The first officer was the flying pilot. About 1 hour and 7 minutes after takeoff, at 15:16, the flightcrew heard a loud bang or an explosion, followed by vibration and a shuddering of the airframe. After checking the engine instruments, the flightcrew determined that the No. 2 aft (tail-mounted) engine had failed. The captain called for the engine shutdown checklist. While performing the engine shutdown checklist, the flight engineer observed that the airplane's normal systems hydraulic pressure and quantity gauges indicated zero. The first officer advised that he could not control the airplane as it entered a right descending turn. The captain took control of the airplane and confirmed that it did not respond to flight control inputs. The captain reduced thrust on the No. 1 engine, and the airplane began to roll to a wings-level attitude. The flightcrew deployed the air driven generator (ADG), which powers the No. 1 auxiliary hydraulic pump, and the hydraulic pump was selected "on." This action did not restore hydraulic power. At 15:20, the flightcrew radioed the Minneapolis Air Route Traffic Control Center (ARTCC) and requested emergency assistance and vectors to the nearest airport. Initially, Des Moines International Airport was suggested by ARTCC. At 15:22, the air traffic controller informed the flightcrew that they were proceeding in the direction of Sioux City; the controller asked the flightcrew if they would prefer to go to Sioux City. The flightcrew responded, "affirmative." They were then given vectors to the Sioux Gateway Airport (SUX) at Sioux City, Iowa. A UAL DC-10 training check airman, who was off duty and seated in a first class passenger seat, volunteered his assistance and was invited to the cockpit at about 15:29. At the request of the captain, the check airman entered the passenger cabin and performed a visual inspection of the airplane's wings. Upon his return, he reported that the inboard ailerons were slightly up, not damaged, and that the spoilers were locked down. There was no movement of the primary flight control surfaces. The captain then directed the check airman to take control of the throttles to free the captain and first officer to manipulate the flight controls. The check airman attempted to use engine power to control pitch and roll. He said that the airplane had a continuous tendency to turn right, making it difficult to maintain a stable pitch attitude. He also advised that the No. 1 and No. 3 engine thrust levers could not be used symmetrically, so he used two hands to manipulate the two throttles. About 15:42, the flight engineer was sent to the passenger cabin to inspect the empennage visually. Upon his return, he reported that he observed damage to the right and left horizontal stabilizers. Fuel was jettisoned to the level of the automatic system cutoff, leaving 33,500 pounds. About 11 minutes before landing, the landing gear was extended by means of the alternate gear extension procedure. The flightcrew said that they made visual contact with the airport about 9 miles out. ATC had intended for flight 232 to attempt to land on runway 31, which was 8,999 feet long. However, ATC advised that the airplane was on approach to runway 22, which was closed, and that the length of this runway was 6,600 feet. Given the airplane's position and the difficulty in making left turns, the captain elected to continue the approach to runway 22 rather than to attempt maneuvering to runway 31. The check airman said that he believed the airplane was lined up and on a normal glidepath to the field. The flaps and slats remained retracted. During the final approach, the captain recalled getting a high sink rate alarm from the ground proximity warning system (GPWS). In the last 20 seconds before touchdown, the airspeed averaged 215 KIAS, and the sink rate was 1,620 feet per minute. Smooth oscillations in pitch and roll continued until just before touchdown when the right wing dropped rapidly. The captain stated that about 100 feet above the ground the nose of the airplane began to pitch downward. He also felt the right wing drop down about the same time. Both the captain and the first officer called for reduced power on short final approach. The check airman said that based on experience with no flap/no slat approaches he knew that power would have to be used to control the airplane's descent. He used the first officer's airspeed indicator and visual cues to determine the flightpath and the need for power changes. He thought that the airplane was fairly well aligned with the runway during the latter stages of the approach and that they would reach the runway. Soon thereafter, he observed that the airplane was positioned to the left of the desired landing area and descending at a high rate. He also observed that the right wing began to drop. He continued to manipulate the No. 1 and No. 3 engine throttles until the airplane contacted the ground. He said that no steady application of power was used on the approach and that the power was constantly changing. He believed that he added power just before contacting the ground. The airplane touched down on the threshold slightly to the left of the centerline on runway 22 at 16:00. First ground contact was made by the right wing tip followed by the right main landing gear. The airplane skidded to the right of the runway and rolled to an inverted position. Witnesses observed the airplane ignite and cartwheel, coming to rest after crossing runway 17/35. Firefighting and rescue operations began immediately, but the airplane was destroyed by impact and fire. The accident resulted in 111 fatal, 47 serious, and 125 minor injuries. The remaining 13 occupants were not injured.

The airplane was in a normal appearing climb after takeoff when it pitched up to a 70° to 80° attitude, stalled, dropped the right wing, then leveled the wings and hit the ground in a near-flat attitude. The weight and cg were within limits. No preimpact problems were found that could cause an inadvertent pitchup. Pilot's only memory is that he couldn't get the control column far enough forward to stop the pitchup. The pilot's seat was found in the full forward position with the right locking pin in the locking hole and the left pin 1/4th of an inch forward of the front locking hole. There were no visible marks on either of the locking pins. Deep scratches were found on the sides of the rail where the seat attachments normally slide back and forth when the seat is adjusted. Exam of the outboard side recessed surface near the aft end disclosed what appeared to be a fresh scratch. The pilot, sole on board, was seriously injured.