Crash of a Beechcraft 200 Super King Air in Elk Grove Village

Date & Time: Sep 8, 2023 at 1841 LT
Operator:
Registration:
N220KW
Flight Type:
Survivors:
Yes
Schedule:
Chicago – Waterloo
MSN:
BB-1120
YOM:
1983
Crew on board:
1
Crew fatalities:
Pax on board:
0
Pax fatalities:
Other fatalities:
Total fatalities:
0
Circumstances:
The pilot departed Chicago-O'Hare Airport at 1643LT on a flight to Waterloo. Less than 50 minutes into the flight, he encountered an unexpected situation and was cleared to return to his departure point. On approach to runway 09L, he initiated a go around procedure then a turn to the left for a second circuit to land. While descending on final, he lost control of the airplane that crashed in a wooded area located in Elk Grove Village, less than 8 km west of O'Hare Airport. The pilot was slightly injured and the airplane was damaged beyond repair.

Crash of a Boeing 747-412F in Halifax

Date & Time: Nov 7, 2018 at 0506 LT
Type of aircraft:
Operator:
Registration:
N908AR
Flight Type:
Survivors:
Yes
Schedule:
Chicago – Halifax
MSN:
28026/1105
YOM:
1997
Flight number:
KYE4854
Country:
Crew on board:
3
Crew fatalities:
Pax on board:
1
Pax fatalities:
Other fatalities:
Total fatalities:
0
Captain / Total flying hours:
21134
Captain / Total hours on type:
166.00
Copilot / Total flying hours:
7404
Copilot / Total hours on type:
1239
Aircraft flight hours:
92471
Aircraft flight cycles:
16948
Circumstances:
The Sky Lease Cargo Boeing 747-412F aircraft (U.S. registration N908AR, serial number 28026) was conducting flight 4854 (KYE4854) from Chicago/O’Hare International Airport, Illinois, U.S., to Halifax/Stanfield International Airport, Nova Scotia, with 3 crew members, 1 passenger, and no cargo on board. The crew conducted the Runway 14 instrument landing system approach. When the aircraft was 1 minute and 21 seconds from the threshold, the crew realized that there was a tailwind; however, they did not recalculate the performance data to confirm that the landing distance available was still acceptable, likely because of the limited amount of time available before landing. The unexpected tailwind resulted in a greater landing distance required, but this distance did not exceed the length of the runway. The aircraft touched down firmly at approximately 0506 Atlantic Standard Time, during the hours of darkness. After the firm touchdown, for undetermined reasons, the engine No. 1 thrust lever was moved forward of the idle position, causing the speed brakes to retract and the autobrake system to disengage, increasing the distance required to bring the aircraft to a stop. In addition, the right crab angle (4.5°) on initial touchdown, combined with the crosswind component and asymmetric reverser selection, caused the aircraft to deviate to the right of the runway centreline. During the landing roll, the pilot monitoring’s attention was focused on the lateral drift and, as a result, the required callouts regarding the position of the deceleration devices were not made. Although manual brake application began 8 seconds after touchdown, maximum braking effort did not occur until 15 seconds later, when the aircraft was 800 feet from the end of the runway. At this position, it was not possible for the aircraft to stop on the runway and, 5 seconds later, the aircraft departed the end of the runway at a speed of 77 knots and came to a stop 270 m (885 feet) past the end. The aircraft struck the approach light stanchions and the localizer antenna array. The No. 2 engine detached from its pylon during the impact sequence and came to rest under the left horizontal stabilizer, causing a fire in the tail section following the impact. The emergency locator transmitter activated. Aircraft rescue and firefighting personnel responded. All 3 crew members received minor injuries and were taken to the hospital. The passenger was not injured. During the overrun, the aircraft crossed a significant drop of 2.8 m (9 feet) approximately 166 m (544 feet) past the end of the runway and was damaged beyond repair.
Probable cause:
Findings as to causes and contributing factors:
These are conditions, acts or safety deficiencies that were found to have caused or contributed to this occurrence.
1. The ineffective presentation style and sequence of the NOTAMs available to the crew and flight dispatch led them to interpret that Runway 23 was not available for landing at Halifax/Stanfield International Airport.
2. The crew was unaware that the aircraft did not meet the pre-departure landing weight requirements using flaps 25 for Runway 14.
3. Due to the timing of the flight during the nighttime circadian trough and because the crew had had insufficient restorative sleep in the previous 24 hours, the crew was experiencing sleep-related fatigue that degraded their performance and cognitive functioning during the approach and landing.
4. Using unfactored (actual) landing distance charts may have given the crew the impression that landing on Runway 14 would have had a considerable runway safety margin, influencing their decision to continue the landing in the presence of a tailwind.
5. When planning the approach, the crew calculated a faster approach speed of reference speed + 10 knots instead of the recommended reference speed + 5 knots, because they misinterpreted that a wind additive was required for the existing conditions.
6. New information regarding a change of active runway was not communicated by air traffic control directly to the crew, although it was contained within the automatic terminal information service broadcast; as a result, the crew continued to believe that the approach and landing to Runway 14 was the only option available.
7. For the approach, the crew selected the typical flap setting of flaps 25 rather than flaps 30, because they believed they had a sufficient safety margin. This setting increased the landing distance required by 494 feet.
8. The crew were operating in a cognitive context of fatigue and biases that encouraged anchoring to and confirming information that aligned with continuing the initial plan, increasing the likelihood that they would continue the approach.
9. The crew recognized the presence of a tailwind on approach 1 minute and 21 seconds from the threshold; likely due to this limited amount of time, the crew did not recalculate the performance data to confirm that the runway safety margin was still acceptable.
10. An elevated level of stress and workload on short final approach likely exacerbated the performance-impairing effects of fatigue to limit the crew’s ability to determine the effect of the tailwind, influencing their decision to continue the approach.
11. The higher aircraft approach speed, the presence of a tailwind component, and the slight deviation above the glideslope increased the landing distance required to a distance greater than the runway length available.
12. After the firm touchdown, for undetermined reasons, the engine No. 1 thrust lever was moved forward of the idle position, causing the speed brakes to retract and the autobrake system to disengage, increasing the distance required to bring the aircraft to a stop.
13. The right crab angle (4.5°) on initial touchdown, combined with the crosswind component and asymmetric reverser selection, caused the aircraft to deviate to the right of the runway centreline.
14. During the landing roll, the pilot monitoring’s attention was focused on the lateral drift and, as a result, the required callouts regarding the position of the deceleration devices were not made.
15. The pilot flying focused on controlling the lateral deviation and, without the benefit of the landing rollout callouts, did not recognize that all of the deceleration devices were not fully deployed and that the autobrake was disengaged.
16. Although manual brake application began 8 seconds after touchdown, maximum braking effort did not occur until 15 seconds later, when the aircraft was 800 feet from the end of the runway. At this position, it was not possible for the aircraft to stop on the runway and, 5 seconds later, the aircraft departed the end of the runway at a speed of 77 knots and came to a stop 270 m (885 feet) past the end of the runway.
17. During the overrun, the aircraft crossed a significant drop of 2.8 m (9 feet) approximately 166 m (544 feet) past the end of the runway and was damaged beyond repair. While this uneven terrain was beyond the 150 m (492 feet) runway end safety area proposed by Transport Canada, it was within the recommended International Civil Aviation Organization runway end safety area of 300 m (984 feet).

Findings as to risk:
These are conditions, unsafe acts or safety deficiencies that were found not to be a factor in this occurrence but could have adverse consequences in future occurrences.
1. If the pilot monitoring does not call out approach conditions or approach speed increases, the pilot flying might not make corrections, increasing the risk of a runway overrun.

Other findings:
These items could enhance safety, resolve an issue of controversy, or provide a data point for future safety studies.
1. The investigation concluded that there was no reverted rubber hydroplaning and almost certainly no dynamic hydroplaning during this occurrence.
2. Although viscous hydroplaning can be expected on all wet runways, the investigation found that when maximum braking effort was applied, the aircraft braking was consistent with the expected braking on Runway 14 under the existing wet runway conditions.
Final Report:

Crash of a McDonnell Douglas MD-83 in Alexandria

Date & Time: Apr 20, 2018 at 1420 LT
Type of aircraft:
Operator:
Registration:
N807WA
Survivors:
Yes
Schedule:
Chicago - Alexandria
MSN:
53093/2066
YOM:
1993
Flight number:
WAL708
Crew on board:
7
Crew fatalities:
Pax on board:
94
Pax fatalities:
Other fatalities:
Total fatalities:
0
Captain / Total flying hours:
13335
Captain / Total hours on type:
6466.00
Copilot / Total flying hours:
4590
Copilot / Total hours on type:
2474
Aircraft flight hours:
43724
Circumstances:
The airplane suffered a right main landing gear collapse during landing at the destination airport. The airplane sustained substantial damage to the right lower wing skin when it contacted the runway after the landing gear collapse. The crew stopped the airplane on the runway and an emergency evacuation was performed through three of the four doors on the airplane. The escape slide at the left forward door did not deploy or inflate due to the depletion of the gas charge in the reservoir. The reservoir depleted due to a leak in the valve assembly and was not caught during multiple inspections since installation of the slide assembly in the airplane. The landing gear cylinder fractured under normal landing loads due to the presence of a fatigue crack on the forward side of the cylinder in an area subject to an AD inspection for cracks. The most recent AD inspection of the cylinder was performed 218 landings prior when the fatigue crack was large enough to be detectable. A previous AD inspection performed 497 landings prior to the accident also did not detect the crack that would have been marginally detectable at the time.
Probable cause:
The failure of the right main landing gear under normal loads due to fatigue cracking in an area subject to an FAA Airworthiness Directive that was not adequately inspected.
Final Report:

Crash of a Boeing 767-323ER in Chicago

Date & Time: Oct 28, 2016 at 1435 LT
Type of aircraft:
Operator:
Registration:
N345AN
Flight Phase:
Survivors:
Yes
Schedule:
Chicago – Miami
MSN:
33084
YOM:
2003
Flight number:
AA383
Crew on board:
9
Crew fatalities:
Pax on board:
161
Pax fatalities:
Other fatalities:
Total fatalities:
0
Captain / Total flying hours:
17400
Captain / Total hours on type:
4000.00
Copilot / Total flying hours:
22000
Copilot / Total hours on type:
1846
Aircraft flight hours:
50632
Aircraft flight cycles:
8120
Circumstances:
On October 28, 2016, about 1432 central daylight time, American Airlines flight 383, a Boeing 767-323, N345AN, had started its takeoff ground roll at Chicago O’Hare International Airport, Chicago, Illinois, when an uncontained engine failure in the right engine and subsequent fire occurred. The flight crew aborted the takeoff and stopped the airplane on the runway, and the flight attendants initiated an emergency evacuation. Of the 2 flight crewmembers, 7 flight attendants, and 161 passengers on board, 1 passenger received a serious injury and 1 flight attendant and 19 passengers received minor injuries during the evacuation. The airplane was substantially damaged from the fire. The airplane was operating under the provisions of 14 Code of Federal Regulations Part 121. Visual meteorological conditions prevailed at the time of the accident. The uncontained engine failure resulted from a high-pressure turbine (HPT) stage 2 disk rupture. The HPT stage 2 disk initially separated into two fragments. One fragment penetrated through the inboard section of the right wing, severed the main engine fuel feed line, breached the fuel tank, traveled up and over the fuselage, and landed about 2,935 ft away. The other fragment exited outboard of the right engine, impacting the runway and fracturing into three pieces. Examination of the fracture surfaces in the forward bore region of the HPT stage 2 disk revealed the presence of dark gray subsurface material discontinuities with multiple cracks initiating along the edges of the discontinuities. The multiple cracks exhibited characteristics that were consistent with low-cycle fatigue. (In airplane engines, low-cycle fatigue cracks grow in single distinct increments during each flight.) Examination of the material also revealed a discrete region underneath the largest discontinuity that appeared white compared with the surrounding material. Interspersed within this region were stringers (microscopic-sized oxide particles) referred to collectively as a “discrete dirty white spot.” The National Transportation Safety Board’s (NTSB) investigation found that the discrete dirty white spot was most likely not detectable during production inspections and subsequent in-service inspections using the procedures in place. The NTSB’s investigation also found that the evacuation of the airplane occurred initially with one engine still operating. In accordance with company procedures and training, the flight crew performed memory items on the engine fire checklist, one of which instructed the crew to shut down the engine on the affected side (in this case, the right side). The captain did not perform the remaining steps of the engine fire checklist (which applied only to airplanes that were in flight) and instead called for the evacuation checklist. The left engine was shut down as part of that checklist. However, the flight attendants had already initiated the evacuation, in accordance with their authority to do so in a life-threatening situation, due to the severity of the fire on the right side of the airplane.
Probable cause:
The National Transportation Safety Board determines that the probable cause of this accident was the failure of the high-pressure turbine (HPT) stage 2 disk, which severed the main engine fuel feed line and breached the right main wing fuel tank, releasing fuel that resulted in a fire on the right side of the airplane during the takeoff roll. The HPT stage 2 disk failed because of low-cycle fatigue cracks that initiated from an internal subsurface manufacturing anomaly that was most likely not detectable during production inspections and subsequent in-service inspections using the procedures in place. Contributing to the serious passenger injury was (1) the delay in shutting down the left engine and (2) a flight attendant’s deviation from company procedures, which resulted in passengers evacuating from the left overwing exit while the left engine was still operating. Contributing to the delay in shutting down the left engine was (1) the lack of a separate checklist procedure for Boeing 767 airplanes that specifically addressed engine fires on the ground and (2) the lack of communication between the flight and cabin crews after the airplane came to a stop.
Final Report:

Crash of an Embraer ERJ-145LR in Ottawa

Date & Time: Sep 4, 2011 at 1529 LT
Type of aircraft:
Operator:
Registration:
N840HK
Survivors:
Yes
Schedule:
Chicago - Ottawa
MSN:
145-341
YOM:
2001
Flight number:
UA3363
Country:
Crew on board:
3
Crew fatalities:
Pax on board:
44
Pax fatalities:
Other fatalities:
Total fatalities:
0
Captain / Total flying hours:
8000
Captain / Total hours on type:
4000.00
Copilot / Total flying hours:
4800
Copilot / Total hours on type:
3800
Aircraft flight hours:
25655
Aircraft flight cycles:
23335
Circumstances:
At 1406, United Express Flight 3363 (LOF3363), operated by Trans States Airlines LLC (TSA), departed Chicago O’Hare International Airport, Chicago, United States. Before commencing the descent into Ottawa/Macdonald-Cartier International Airport (CYOW), Ontario, the flight crew obtained the automatic terminal information service (ATIS) information Yankee for CYOW issued at 1411. Based on the reported wind speed and direction, the flight crew calculated the approach speed (VAPP) to be 133 knots indicated airspeed (KIAS). Runway 25 was identified in ATIS information Yankee as the active runway. However, as a result of a previous overrun on Runway 07/25 in August 2010, TSA prohibited its flight crews from landing or taking off on Runway 07/25 when the surface is reported as damp or wet. Because rain showers were forecast for CYOW and Runway 32 was the longest runway, the flight crew decided at 1506 to carry out an instrument landing system (ILS) approach to Runway 32. At 1524, the CYOW terminal air traffic controller (ATC) advised the flight crew that it was starting to rain heavily at CYOW. About 2 minutes later, the aircraft intercepted the glideslope for the ILS to Runway 32. Final descent was initiated, the landing gear was extended, and the flaps were selected to 22°. Upon contacting the CYOW tower controller, the flight crew was advised that moderate rain had just started at the airport and the wind was reported as 310° magnetic (M) at 10 knots. The aircraft crossed the GREELY (YYR) final approach fix at 4.3 nautical miles (nm), slightly above the glideslope at 174 KIAS. About 1528, the aircraft passed through 1000 feet above ground level (agl) at 155 knots. Moments later, the flaps were selected to 45°. The airspeed at the time was approximately 145 KIAS. The tower controller advised the flight crew that the wind had changed to 320°M at 13 knots gusting to 20 knots. To compensate for the increased wind speed, the flight crew increased the VAPP to 140 KIAS. About 1 minute later, at 1529, the aircraft crossed the threshold of Runway 32 at about 45 feet agl, at an airspeed of 139 KIAS. As the aircraft crossed the runway threshold, the intensity of the rain increased, so the flight crew selected the windshield wipers to high. When the aircraft was about 20 feet agl, engine power was reduced and a flare was commenced. Just before touchdown, the aircraft encountered a downpour sufficient to obscure the crew’s view of the runway. Perceiving a sudden increase in descent rate, at approximately 5 feet agl, the captain applied maximum thrust on both engines. The master caution light illuminated, and a voice warning stated that the flaps were not in a take-off configuration. Maximum thrust was maintained for 7 seconds. The aircraft touched down smoothly 2700 feet beyond the threshold at 119 KIAS; the airspeed was increasing, and the aircraft became airborne again. The aircraft touched down a second time at 3037 feet beyond the threshold, with the airspeed increasing through 125 KIAS. Airspeed on touchdown peaked at 128 KIAS as the nosewheel was lowered to the ground, and then the thrust levers were retarded to flight idle. The outboard spoilers almost immediately deployed, and about 8 seconds later, the inboard spoilers deployed. The aircraft was about 20 feet right of the runway centreline when it touched down for the second time. Once the nosewheel was on the ground, the captain applied maximum brakes. The flight crew almost immediately noted that the aircraft began skidding. The captain then requested the first officer to apply maximum brakes as well. The aircraft continued to skid, and no significant brake pressure was recorded until about 14 seconds after the outboard spoilers deployed, when brake pressure suddenly increased to its maximum. During this time, the captain attempted to steer the aircraft back to the runway centreline. As the aircraft skidded down the runway, it began to yaw to the left. Full right rudder was applied, but was ineffective in correcting the left yaw. Sufficient water was present on the runway surface to cause the aircraft tires to send a spray of water, commonly known as a rooster tail, to a height of over 22 feet, trailing over 300 feet behind the aircraft. At some point during the landing roll, the captain partially applied the emergency/parking brake (EPB), and when no braking action was felt, the EPB was engaged further. With no perceivable deceleration being felt, the EPB was stowed. The aircraft continued to skid down the runway until about 7500 feet from the threshold, at which point it started skidding sideways along the runway. At 1530, the nosewheel exited the paved surface, 8120 feet from the threshold, at approximately 53 knots, on a heading of 271°M. The aircraft came to rest on a heading of 211°M, just off the left side of the paved surface. After coming to a stop, the flight crew carried out the emergency shutdown procedure as per the company Quick Reference Handbook (QRH), and consulted with the flight attendant on the status of everyone in the passenger cabin. The flight crew determined that there was no immediate threat and decided to hold the passengers on board. When the aircraft exited the runway surface, the tower activated the crash alarm. The CYOW airport rescue and firefighting (ARFF) services responded, and were on scene approximately 3 minutes after the activation of the crash alarm. Once ARFF personnel had conducted a thorough exterior check of the aircraft, they informed the flight crew that there was a fuel leak. The captain then called for an immediate evacuation of the aircraft. The passengers evacuated through the main cabin door, and moved to the runway as directed by the flight crew and ARFF personnel. The evacuation was initiated approximately 12 minutes after the aircraft came to a final stop. After the evacuation was complete, the firefighters sprayed foam around the aircraft where the fuel had leaked.
Probable cause:
Findings as to causes and contributing factors:
1. Heavy rainfall before and during the landing resulted in a 4–6 mm layer of water contaminating the runway.
2. The occurrence aircraft’s airspeed during final approach exceeded the company prescribed limits for stabilized approach criteria. As a result, the aircraft crossed the runway threshold at a higher than recommended VREF airspeed.
3. A go-around was not performed, as per standard operating procedures, when the aircraft’s speed was greater than 5 knots above the appropriate approach speed during the stabilized portion of the approach.
4. The application of engine thrust just before touchdown caused the aircraft to touch down 3037 feet from the threshold at a higher than recommended airspeed.
5. The combination of a less than firm landing and underinflated tires contributed to the aircraft hydroplaning.
6. The emergency/parking brake was applied during the landing roll, which disabled the anti-skid braking system and prolonged the skid.
7. The aircraft lost directional control as a result of hydroplaning and veered off the runway.

Findings as to risk:
1. The typical and frequently used technique for differential braking that pilots are trained to use may not be effective when anti-skid systems require different techniques.
2. If aircraft electrical power is applied with an active fuel leak, there is a risk that an electrical spark could ignite the fuel and start a fire.
3. The use of non-grooved runways increases the risk of hydroplaning, which may result in runway excursions.
4. If there is an absence of information and training about non-grooved runways, there is a risk that crews will not carry out the appropriate landing techniques when these runways are wet.
5. The use of thrust reversers reduces the risk of runway excursions when landing on wet runways.
6. If pilots do not comply with standard operating procedures, and companies do not assure compliance, then there is a risk that occurrences resulting from such deviations will persist.

Other findings:
1. The central maintenance computer was downloaded successfully; however, there were no data present in the memory unit.
2. Although the Transportation Safety Board was able to download high-quality data from the flight data recorder, the parameters that were not recorded due to the model type and input to the flight data recorder made it more difficult to determine the sequence of events.
Final Report:

Crash of a Boeing 727-223 in Chicago

Date & Time: Feb 9, 1998 at 0954 LT
Type of aircraft:
Operator:
Registration:
N845AA
Survivors:
Yes
Schedule:
Kansas City - Chicago
MSN:
20986
YOM:
1975
Flight number:
AA1340
Crew on board:
6
Crew fatalities:
Pax on board:
115
Pax fatalities:
Other fatalities:
Total fatalities:
0
Captain / Total flying hours:
11000
Captain / Total hours on type:
1319.00
Aircraft flight hours:
59069
Circumstances:
On February 9, 1998, about 0954 central standard time (CST), a Boeing 727-223 (727), N845AA, operated by American Airlines as flight 1340, impacted the ground short of the runway 14R threshold at Chicago O'Hare International Airport (ORD) while conducting a Category II (CAT II) instrument landing system (ILS) coupled approach. Twenty-two passengers and one flight attendant received minor injuries, and the airplane was substantially damaged. The airplane, being operated by American Airlines as a scheduled domestic passenger flight under the provisions of 14 Code of Federal Regulations (CFR) Part 121, with 116 passengers, 3 flight crewmembers, and 3 flight attendants on board, was destined for Chicago, Illinois, from Kansas City International Airport (MCI), Kansas City, Missouri. Daylight instrument meteorological conditions prevailed at the time of the accident.
Probable cause:
The failure of the flight crew to maintain a proper pitch attitude for a successful landing or go-around. Contributing to the accident were the divergent pitch oscillations of the airplane, which occurred during the final approach and were the result of an improper autopilot desensitization rate.
Final Report:

Crash of an ATR72-212 in Roselawn: 68 killed

Date & Time: Oct 31, 1994 at 1559 LT
Type of aircraft:
Operator:
Registration:
N401AM
Flight Phase:
Survivors:
No
Schedule:
Indianapolis - Chicago
MSN:
401
YOM:
1994
Flight number:
AA4184
Crew on board:
4
Crew fatalities:
Pax on board:
64
Pax fatalities:
Other fatalities:
Total fatalities:
68
Captain / Total flying hours:
7867
Captain / Total hours on type:
1548.00
Copilot / Total flying hours:
5176
Copilot / Total hours on type:
3657
Aircraft flight hours:
1352
Aircraft flight cycles:
1671
Circumstances:
American Eagle Flight 4184 was scheduled to depart the gate in Indianapolis at 14:10; however, due to a change in the traffic flow because of deteriorating weather conditions at destination Chicago-O'Hare, the flight left the gate at 14:14 and was held on the ground for 42 minutes before receiving an IFR clearance to O'Hare. At 14:55, the controller cleared flight 4184 for takeoff. The aircraft climbed to an enroute altitude of 16,300 feet. At 15:13, flight 4184 began the descent to 10,000 feet. During the descent, the FDR recorded the activation of the Level III airframe de-icing system. At 15:18, shortly after flight 4184 leveled off at 10,000 feet, the crew received a clearance to enter a holding pattern near the LUCIT intersection and they were told to expect further clearance at 15:45, which was revised to 16:00 at 15:38. Three minutes later the Level III airframe de-icing system activated again. At 15:56, the controller contacted flight 4184 and instructed the flight crew to descend to 8,000 feet. The engine power was reduced to the flight idle position, the propeller speed was 86 percent, and the autopilot remained engaged in the vertical speed (VS) and heading select (HDG SEL) modes. At 15:57:21, as the airplane was descending in a 15-degree right-wing-down attitude at 186 KIAS, the sound of the flap overspeed warning was recorded on the CVR. The crew selected flaps from 15 to zero degrees and the AOA and pitch attitude began to increase. At 15:57:33, as the airplane was descending through 9,130 feet, the AOA increased through 5 degrees, and the ailerons began deflecting to a right-wing-down position. About 1/2 second later, the ailerons rapidly deflected to 13:43 degrees right-wing-down, the autopilot disconnected. The airplane rolled rapidly to the right, and the pitch attitude and AOA began to decrease. Within several seconds of the initial aileron and roll excursion, the AOA decreased through 3.5 degrees, the ailerons moved to a nearly neutral position, and the airplane stopped rolling at 77 degrees right-wing-down. The airplane then began to roll to the left toward a wings-level attitude, the elevator began moving in a nose-up direction, the AOA began increasing, and the pitch attitude stopped at approximately 15 degrees nose down. At 15:57:38, as the airplane rolled back to the left through 59 degrees right-wing-down (towards wings level), the AOA increased again through 5 degrees and the ailerons again deflected rapidly to a right-wing-down position. The captain's nose-up control column force exceeded 22 pounds, and the airplane rolled rapidly to the right, at a rate in excess of 50 degrees per second. The captain's nose-up control column force decreased below 22 pounds as the airplane rolled through 120 degrees, and the first officer's nose-up control column force exceeded 22 pounds just after the airplane rolled through the inverted position (180 degrees). Nose-up elevator inputs were indicated on the FDR throughout the roll, and the AOA increased when nose-up elevator increased. At 15:57:45 the airplane rolled through the wings-level attitude (completion of first full roll). The nose-up elevator and AOA then decreased rapidly, the ailerons immediately deflected to 6 degrees left-wing-down and then stabilized at about 1 degree right-wing-down, and the airplane stopped rolling at 144 degrees right wing down. At 15:57:48, as the airplane began rolling left, back towards wings level, the airspeed increased through 260 knots, the pitch attitude decreased through 60 degrees nose down, normal acceleration fluctuated between 2.0 and 2.5 G, and the altitude decreased through 6,000 feet. At 15:57:51, as the roll attitude passed through 90 degrees, continuing towards wings level, the captain applied more than 22 pounds of nose-up control column force, the elevator position increased to about 3 degrees nose up, pitch attitude stopped decreasing at 73 degrees nose down, the airspeed increased through 300 KIAS, normal acceleration remained above 2 G, and the altitude decreased through 4,900 feet. At 15:57:53, as the captain's nose-up control column force decreased below 22 pounds, the first officer's nose-up control column force again exceeded 22 pounds and the captain made the statement "nice and easy." At 15:57:55, the normal acceleration increased to over 3.0 G. Approximately 1.7 seconds later, as the altitude decreased through 1,700 feet, the elevator position and vertical acceleration began to increase rapidly. The last recorded data on the FDR occurred at an altitude of 1,682 feet (vertical speed of approximately 500 feet per second), and indicated that the airplane was at an airspeed of 375 KIAS, a pitch attitude of 38 degrees nose down with 5 degrees of nose-up elevator, and was experiencing a vertical acceleration of 3.6 G. The airplane impacted a wet soybean field partially inverted, in a nose down, left-wing-low attitude. Based on petitions filed for reconsideration of the probable cause, the NTSB on September 2002 updated it's findings.
Probable cause:
The loss of control, attributed to a sudden and unexpected aileron hinge moment reversal, that occurred after a ridge of ice accreted beyond the deice boots while the airplane was in a holding pattern during which it intermittently encountered supercooled cloud and drizzle/rain drops, the size and water content of which exceeded those described in the icing certification envelope. The airplane was susceptible to this loss of control, and the crew was unable to recover. Contributing to the accident were:
1) the French Directorate General for Civil Aviation’s (DGAC’s) inadequate oversight of the ATR 42 and 72, and its failure to take the necessary corrective action to ensure continued airworthiness in icing conditions;
2) the DGAC’s failure to provide the FAA with timely airworthiness information developed from previous ATR incidents and accidents in icing conditions,
3) the Federal Aviation Administration’s (FAA’s) failure to ensure that aircraft icing certification requirements, operational requirements for flight into icing conditions, and FAA published aircraft icing information adequately accounted for the hazards that can result from flight in freezing rain,
4) the FAA’s inadequate oversight of the ATR 42 and 72 to ensure continued airworthiness in icing conditions; and
5) ATR’s inadequate response to the continued occurrence of ATR 42 icing/roll upsets which, in conjunction with information learned about aileron control difficulties during the certification and development of the ATR 42 and 72, should have prompted additional research, and the creation of updated airplane flight manuals, flightcrew operating manuals and training programs related to operation of the ATR 42 and 72 in such icing conditions.
Final Report:

Crash of a Boeing 737-3B7 in Aliquippa: 132 killed

Date & Time: Sep 8, 1994 at 1903 LT
Type of aircraft:
Operator:
Registration:
N513AU
Survivors:
No
Schedule:
Chicago – Pittsburgh
MSN:
23699
YOM:
1987
Flight number:
US427
Crew on board:
5
Crew fatalities:
Pax on board:
127
Pax fatalities:
Other fatalities:
Total fatalities:
132
Captain / Total flying hours:
12000
Captain / Total hours on type:
3269.00
Copilot / Total flying hours:
9119
Copilot / Total hours on type:
3644
Aircraft flight hours:
23846
Aircraft flight cycles:
14489
Circumstances:
The aircraft crashed while maneuvering to land at Pittsburgh International Airport, Pittsburgh, Pennsylvania. Flight 427 was operating under the provisions of 14 Code of Federal Regulations Part 121 as a scheduled domestic passenger flight from Chicago-O'Hare International Airport, Chicago, Illinois, to Pittsburgh. The flight departed about 1810, with 2 pilots, 3 flight attendants, and 127 passengers on board. The airplane entered an uncontrolled descent and impacted terrain near Aliquippa, Pennsylvania, about 6 miles northwest of the destination airport. All 132 people on board were killed, and the airplane was destroyed by impact forces and fire. Visual meteorological conditions prevailed for the flight, which operated on an instrument flight rules flight plan.
Probable cause:
A loss of control of the airplane resulting from the movement of the rudder surface to its blowdown limit. The rudder surface most likely deflected in a direction opposite to that commanded by the pilots as a result of a jam of the main rudder power control unit servo valve secondary slide to the servo valve housing offset from its neutral position and overtravel of the primary slide.
Final Report: